Scientific Bibliography

Nanobiology and Cancer Nanotechnology
Nanotechnology Devices and Nanomaterials
Nanotechnology-Enabled Therapeutics Development and Delivery
Cancer Diagnostics and Biosensors
Nanotechnologies in Advanced Imaging
Environment, Health and Safety

---

Nanotechnology Devices and Nanomaterials

2007  2006   2005   2004   2003   2002

[ expand all abstracts ]   [ collapse all abstracts ]

Light-assisted oxidation of single-wall carbon nanohorns for abundant creation of oxygenated groups that enable chemical modifications with proteins to enhance biocompatibility.
Minfang Zhang, Masako Yudasaka, Kumiko Ajima, Jin Miyawaki, Sumio Iijima.
ACS Nano. 2007;1(4), 265–272.
[ expand abstract ]

We show that light-assisted oxidation with hydrogen peroxide effectively and rapidly opens holes in carbon nanohorn walls and, more importantly, creates abundant oxygenated groups such as carboxylic groups at the hole edges. These oxygenated groups reacted with the protein bovine serum albumin. The obtained conjugates were highly dispersed in phosphate-buffered saline and were taken up by cultured mammalian cells via an endocytosis pathway.

Amphiphilic helical peptide enhances the uptake of single-walled carbon nanotubes by living cells.
Chin SF, Baughman RH, Dalton AB, Dieckmann GR, Draper RK, Mikoryak C, Musselman IH, Poenitzsch VZ, Xie H, Pantano P.
Exp Biol Med (Maywood). 2007 Oct;232(9):1236-44.
[ expand abstract ]

Department of Chemistry, The University of Texas at Dallas, Richardson, TX 75083-0688, USA. The success of many projected applications of carbon nano-tubes (CNTs) to living cells, such as intracellular sensors and nanovectors, will depend on how many CNTs are taken up by cells. Here we report the enhanced uptake by HeLa cells of single-walled CNTs coated with a designed peptide termed nano-1. Atomic force microscopy showed that the dispersions were composed of individual and small bundles of nano-1 CNTs with 0.7- to 32-nm diameters and 100- to 400-nm lengths. Spectroscopic characterizations revealed that nano-1 disperses CNTs in a non-covalent fashion that preserves CNT optical properties. Elemental analyses indicated that our sample preparation protocol involving sonication and centrifugation effectively eliminated metal impurities associated with CNT manufacturing processes. We further showed that the purified CNT dispersions are taken up by HeLa cells in a time- and temperature-dependent fashion, and that they do not affect the HeLa cell growth rate, evidence that the CNTs inside cells are not toxic under these conditions. Finally, we discovered that approximately 6-fold more CNTs are taken up by cells in the presence of nano-1 compared with medium containing serum but no peptide. The fact that coating CNTs with a peptide enhances uptake offers a strategy for improving the performance of applications that require CNTs to be inside cells.

Dendrimer generation effects on photodynamic efficacy of dendrimer porphyrins and dendrimer-loaded supramolecular nanocarriers.
Li Y, Jang WD, Nishiyama N, Kishimura A, Kawauchi S, Morimoto Y, Miake S, Yamashita T, Kikuchi M, Aida T, Kataoka K.
Chem. Mater. 2007; 19 (23), 5557 -5562.
[ expand abstract ]

A series of poly(benzyl ether) dendrimer porphyrins (DPs) (Gn = n-generation dendrimer, n = 1-3) was examined as potential photosensitizers for photodynamic therapy (PDT). Polyion complexes (PICs) between the DPs and poly(ethylene glycol)-block-poly(L-lysine) (PEG-b-PLL) were formed via an electrostatic interaction between the positively charged poly(L-lysine) (PLL) segment and negatively charged periphery of the DPs. Dynamic light scattering (DLS) measurements and transmission electron microscopy (TEM) showed that G3 formed a core-shell-type nanocarrier micelle, whereas G1 and G2 formed irregular-shaped nanoparticles with a relatively high polydispersity. The photophysical properties of the DP-loaded PIC nanocarriers strongly depend on the generation of the DPs. In the case of G1 and G2, their fluorescence lifetime and oxygen consumption ability were significantly reduced by the formation of the PIC nanocarriers, whereas the G3-loaded PIC nanocarrier exhibited almost comparable fluorescence lifetimes and oxygen consumption abilities to the free G3. The incorporation of DPs into PIC nanocarriers resulted in an appreciable increase in the cellular uptake, yet inversely correlated with the generation. Alternatively, the photocytotoxicity of the DPs within the nanocarriers increased with an increase in the generation despite a decrease in the cellular uptake. By correlating the effects of the uptake amount with the photocytotoxicity, the PIC nanocarriers showed remarkable enhancement of the PDT efficacy dependent on the generation of DPs.

Biocatalytic microcontact printing.
Snyder PW, Johannes MS, Vogen BN, Clark RL, Toone EJ.
J Org Chem. 2007 Sep 14;72(19):7459-61.
[ expand abstract ]

Immobilized biocatalytic lithography is presented as an application of soft lithography. In traditional microcontact printing, diffusion limits resolution of pattern transfer. By using an immobilized catalyst, the lateral resolution of microcontact printing would depend only on the length and flexibility of the tether (<2 nm) as opposed to diffusion (>100 nm). In the work, exonuclease reversibly immobilized on a relief-patterned stamp is used to ablate ssDNA monolayers Percent of ablation was determined via confocal fluorescence microscopy to be approximately 70%.

Glutaric acid as a spacer facilitates improved intracellular uptake of LHRH-SPION into human breast cancer cells.
Kumar CS, Leuschner C, Urbina M, Ozkaya T, Hormes J.
Int J Nanomedicine. 2007;2(2):175-9.
[ expand abstract ]

Superparamagnetic iron oxide nanoparticles (SPIONs) bound directly to luteinizing hormone releasing hormone (LHRH) have shown high efficiency for intracellular uptake to breast cancer cells, MDA-MB-435S.luc. We demonstrate in this communication that inclusion of a small spacer molecule such as glutaric acid (Glu) in between SPION and LHRH increases further receptor mediated intracellular uptake. LHRH-bound SPIONs with and without the spacer molecule were nontoxic.

Selecting clinically-driven biomarkers for cancer nanotechnology.
Phan JH, Young AN, Wang MD.
Conf Proc IEEE Eng Med Biol Soc. 2006;1:3317-20.
[ expand abstract ]

The challenge of biomarker identification for bionanotechnology is that we need to find less than ten potential biomarkers from high throughput data so that quantum dot synthesis and imaging can be effective. Among all the extensive biomarker research, the novelty of our research is to reduce the number the biomarkers by studying the efficacy of several classifiers and error estimation methods. Specifically, we are using renal cancer expression data. The dataset consists of 31 microarray samples divided into four classes-clear cell, oncocytoma/chromophobe, papillary, and angiomyolipoma. Each class is compared to all other classes using error estimation methods for support vector machines (SVM), Fisher's discriminant (FD), and signed distance function (SDF). Prior knowledge of significant biomarker from a previous study is used to score the effectiveness of each classifier in correctly identifying these biomarkers. We have achieved intelligent model selection for biomarker identification so that the total number of nano-imaging targets is small.

Nanotechnology and Cancer.
Heath JR, Davis ME.
Annu Rev Med. 2008;59:251-65.
[ expand abstract ]

The biological picture of cancer is rapidly advancing from models built from phenomenological descriptions to network models derived from systems biology, which can capture the evolving pathophysiology of the disease at the molecular level. The translation of this (still academic) picture into a clinically relevant framework can be enabling for the war on cancer, but it is a scientific and technological challenge. In this review, we discuss emerging in vitro diagnostic technologies and therapeutic approaches that are being developed to handle this challenge. Our discussion of in vitro diagnostics is guided by the theme of making large numbers of measurements accurately, sensitively, and at very low cost. We discuss diagnostic approaches based on microfluidics and nanotechnology. We then review the current state of the art of nanoparticle-based therapeutics that have reached the clinic. The goal of the presentation is to identify nanotherapeutic strategies that are designed to increase efficacy while simultaneously minimizing the toxic side effects commonly associated with cancer chemotherapies.

Supramolecular Chemistry on Water-Soluble Carbon Nanotubes for Drug Loading and Delivery.
Liu Z, Sun X, Nakayama-Ratchford N, Dai H.
ACS Nano. 2007;1(1):50–56.
[ expand abstract ]

We show that large surface areas exist for supramolecular chemistry on single-walled carbon nanotubes (SWNTs) prefunctionalized noncovalently or covalently by common surfactant or acid-oxidation routes. Water-soluble SWNTs with poly(ethylene glycol) (PEG) functionalization via these routes allow for surprisingly high degrees of p-stacking of aromatic molecules, including a cancer drug (doxorubicin) with ultrahigh loading capacity, a widely used fluorescence molecule (fluorescein), and combinations of molecules. Binding of molecules to nanotubes and their release can be controlled by varying the pH. The strength of p-stacking of aromatic molecules is dependent on nanotube diameter, leading to a method for controlling the release rate of molecules from SWNTs by using nanotube materials with suitable diameter. This work introduces the concept of “functionalization partitioning” of SWNTs, i.e., imparting multiple chemical species, such as PEG, drugs, and fluorescent tags, with different functionalities onto the surface of the same nanotube. Such chemical partitioning should open up new opportunities in chemical, biological, and medical applications of novel nanomaterials.

Surface modification and functionalization of nanoscale metal-organic frameworks for controlled release and luminescence sensing.
Rieter WJ, Taylor KM, Lin W.
J Am Chem Soc. 2007 Aug 15;129(32):9852-3.
[ expand abstract ]

We describe in this paper a general method for synthesizing a new class of nanocomposites with a nanoscale metal-organic framework (NMOF) core and a silica shell. Silica shells of variable thickness were deposited on the NMOFs that had been surface-modified with polyvinylpyrrolidone (PVP) using a sol-gel procedure. The NMOF core of the nanocomposite could be completely removed (via dissolution) at low pH to afford hollow silica shells with varied thickness and aspect ratios. We also showed that the silica shell of such nanocomposites significantly stabilized the NMOF core against dissolution, thus demonstrating the ability to control the release of metal constituents from such silica-coated NMOFs. The silica shell was further functionalized with a silylated Tb-EDTA monoamide derivative for the luminescence sensing of dipicolinic acid (DPA), which is a major constituent of many pathogenic spore-forming bacteria. Owing to the tunability of NMOF composition and morphology, the present approach should allow for the synthesis of not only interesting nanoshells that are not accessible with presently available templates but also novel core-shell hybrid nanostructures for future imaging, sensing, and drug delivery applications.

Hydrodynamic dimensions, electrophoretic mobility, and stability of hydrophilic quantum dots.
Pons T, Uyeda HT, Medintz IL, Mattoussi H.
J Phys Chem B. 2006 Oct 19;110(41):20308-16.
[ expand abstract ]

Luminescent semiconductor quantum dots (QDs) have great potential for use in biological assays and imaging. These nanocrystals are capped with surface ligands (bifunctional molecules, amphiphilic polymers, phospholipids, etc.) that render them hydrophilic and provide them with functional properties. These coatings alters their hydrodynamic radii and surface charge, which can drastically affect properties such as diffusion within the cell cytoplasm. Heavy atom techniques such as transmission electron microscopy and X-ray scattering probe the inorganic core and do not take into account the ligand coating. Herein we use dynamic light scattering to characterize the hydrodynamic radius (R(H)) of CdSe-ZnS QDs capped with various hydrophilic surface coatings (including dihydrolipoic acid and amphiphilic polymers) and self-assembled QD-protein bioconjugates. Experiments were complemented with measurements of the geometric size and zeta potential using agarose gel electrophoresis and laser Doppler velocimetry. We find that the effects of surface ligands on the hydrodynamic radius and on the nanoparticle mobility are complex and strongly depend on a combination of the inorganic core size and nature and lateral extension of the hydrophilic surface coating. These properties are critical for the design of QD-based biosensing assays as well as QD bioconjugate diffusion in live cells.

Influence of size, surface, cell line, and kinetic properties on the specific binding of A33 antigen-targeted multilayered particles and capsules to colorectal cancer cells.
Christina Cortez, Eva Tomaskovic-Crook, Angus P. R. Johnston, Andrew M. Scott, Edouard C. Nice, Joan K. Heath, Frank Caruso.
ACS Nano. 2007;1(2):93–102.
[ expand abstract ]

There has been increased interest in the use of polymer capsules formed by the layer-by-layer (LbL) technique as therapeutic carriers to cancer cells due to their versatility and ease of surface modification. We have investigated the influence of size, surface properties, cell line, and kinetic parameters such as dosage (particle concentration) and incubation time on the specific binding of humanized A33 monoclonal antibody (huA33 mAb)-coated LbL particles and capsules to colorectal cancer cells. HuA33 mAb binds to the A33 antigen present on almost all colorectal cancer cells and has demonstrated great promise in clinical trials as an immunotherapeutic agent for cancer therapy. Flow cytometry experiments showed the cell binding specificity of huA33 mAb-coated particles to be size-dependent, with the optimal size for enhanced selectivity at ~500 nm. The specific binding was improved by increasing the dosage of particles incubated with the cells. The level of specific versus nonspecific binding was compared for particles terminated with various polyelectrolytes to examine the surface dependency of antibody attachment and subsequent cell binding ability. The specific binding of huA33 mAb-coated particles is also reported for two colorectal cancer cell lines, with an enhanced binding ratio between 4 and 10 obtained for the huA33 mAb-functionalized particles. This investigation aims to improve the level of specific targeting of LbL particles, which is important in targeted drug and gene delivery applications.

Dendrimer-mediated transfer printing of DNA and RNA microarrays.
Rozkiewicz DI, Brugman W, Kerkhoven RM, Ravoo BJ, Reinhoudt DN.
J Am Chem Soc. 2007 Sep 19;129(37):11593-9.
[ expand abstract ]

This paper describes a new method to replicate DNA and RNA microarrays. The technique, which facilitates positioning of DNA and RNA with submicron edge resolution by microcontact printing (muCP), is based on the modification of poly(dimethylsiloxane) (PDMS) stamps with dendrimers ("dendri-stamps"). The modification of PDMS stamps with generation 5 poly(propylene imine) dendrimers (G5-PPI) gives a high density of positive charge on the stamp surface that can attract negatively charged oligonucleotides in a "layer-by-layer" arrangement. DNA as well as RNA is transfer printed from the stamp to a target surface. Imine chemistry is applied to immobilize amino-modified DNA and RNA molecules to an aldehyde-terminated substrate. The labile imine bond is reduced to a stable secondary amine bond, forming a robust connection between the polynucleotide strand and the solid support. Microcontact printed oligonucleotides are distributed homogeneously within the patterned area and available for hybridization. By using a robotic spotting system, an array of hundreds of oligonucleotide spots is deposited on the surface of a flat, dendrimer-modified stamp that is subsequently used for repeated replication of the entire microarray by microcontact printing. The printed microarrays are characterized by homogeneous probe density and regular spot morphology.

Fluorescent magnetic nanocrystals by sequential addition of reagents in a one-pot reaction: a simple preparation for multifunctional nanostructures.
Gao J, Zhang B, Gao Y, Pan Y, Zhang X, Xu B.
J Am Chem Soc. 2007 Oct 3;129(39):11928-35.
[ expand abstract ]

Core-shell nanostructures consisting of FePt magnetic nanoparticles as the core and semiconducting chalcogenides as the shell were synthesized by a series of reactions in a one-pot procedure. Adding Cd(acac)2 as the cadmium precursor to a reaction mixture containing FePt nanoparticles afforded FePt@CdO core-shell intermediates. The subsequent addition of chalcogens yielded FePt@CdX core-shell nanocrystals (where X was S or Se). The reverse sequence of addition, i.e., adding X before Cd, resulted in spongelike nanostructures because the chalcogens readily formed nanowires in the solution. Transmission electron microscopy, energy-dispersive X-ray spectrometry, selected area electron diffraction, fluorescence spectroscopy, and SQUID were used to characterize the nanostructures. These core-shell nanostructures displayed superparamagnetism at room temperature and exhibited fluorescence with quantum yields of 2.3-9.7%. The flexibility in the sequence of addition of reagents, combined with the compatibility of the lattices of the different materials, provides a powerful yet convenient strategy for generating sophisticated, multifunctional nanostructures.

Facile production of multivalent enzyme-nanoparticle conjugates.
Kuhna SJ, Fincha SK, Hallahana DE, Giorgioa TD.
J Magn Magn Mater. 2007 April;311(1):68-72
[ expand abstract ]

Nanoparticles (NPs) enable the development of new, biologically relevant, multifunctional agents. Multifunctional NPs can mimic the invasive biological processes involved in cancer metastasis. We have demonstrated a facile and controllable method of conjugating multiple enzyme species to superparamagnetic (SPM) NPs. Horseradish peroxidase, a-glucosidase, and collagenase were conjugated to SPM NPs with a functional enzyme:NP ratio of 15:127:103:1. N-succinimidyl-S-acetylthiopropionate (SATP)-mediated addition of sulfhydryls to enzymes was achieved without significant activity loss. Conjugation of all enzymes was simultaneously accomplished using maleimide reactive groups generated from activation of amines associated with polyethylene glycol molecules on the NP surface. Cross reactivity between enzyme activity assay systems was negligible.

Integrated magnetic bionanocomposites through nanoparticle-mediated assembly of ferritin.
Srivastava S, Samanta B, Jordan BJ, Hong R, Xiao Q, Tuominen MT, Rotello VM.
J Am Chem Soc. 2007 Sep 26;129(38):11776-80.
[ expand abstract ]

Magnetic (FePt) and nonmagnetic (Au) nanoparticles were used to assemble ferritin into near-monodisperse bionanocomposites featuring regular interparticle spacing. The FePt/ferritin assemblies are integrated magnetic materials with ferritin providing added magnetic volume fraction to the magnetic nanocomposite. These assemblies differ from either of their constituent particles in terms of blocking temperature (TB), net magnetic moment, coercivity, and remnance.

Surface modification of cetyltrimethylammonium bromide-capped gold nanorods to make molecular probes.
Yu C, Varghese L, Irudayaraj J.
Langmuir. 2007 Aug 14; 23(17):9114-9.
[ expand abstract ]

A chemical procedure to replace the cetyltrimethylammonium bromide (CTAB) cap on gold nanorods (GNRs) fabricated through seed-mediated growth with organothiol compounds [3-animo-5-mercapto-1,2,4-triazole (AMTAZ) and 11-mercaptoundecaonic acid (MUDA)] was developed to reduce the cytotoxity of GNRs and facilitate further biofunctionalization. Compared to phosphatidylcholine (PC) modification, our procedure yields stable GNRs that are biocompatible and suitable for whole-cell studies. The PC-, AMTAZ-, and MUDA-activated GNRs all showed low cytotoxicity. By choosing different organothiols, net positive or negative charges could be created on the nanorod surface, for different applications. Gold nanorod molecular probes (GNrMPs) were fabricated by subsequent attachment of antibodies to the activated GNRs and were used to visualize and detect cell surface biomarkers in normal and transformed human breast epithelial cells, demonstrating the potential of developing novel biosensors using gold nanorods. The sensitivity of GNrMPs made from organothiol-activated GNRs is considerably higher than that of CTAB/PC-activated GNRs, demonstrating that the protocol reported here is favored in developing molecular probes using GNRs.

The efficiency of a PAMAM dendrimer toward the encapsulation of the antileukemic drug 6-mercaptopurine.
Neerman MF.
Anticancer Drugs. 2007 Aug;18(7):839-42.
[ expand abstract ]

No abstract available (Citation link)

Locked nucleic acid-nanoparticle conjugates.
Seferos DS, Giljohann DA, Rosi NL, Mirkin CA.
Chembiochem. 2007 Jul 23;8(11):1230-2.
[ expand abstract ]

No abstract available (Citation link)

Simplified preparation via streptavidin of antisense oligomers/carriers nanoparticles showing improved cellular delivery in culture.
Wang Y, Nakamura K, Liu X, Kitamura N, Kubo A, Hnatowich DJ.
Bioconjug Chem. 2007 Jul-Aug;18(4):1338-43.
[ expand abstract ]

OBJECTIVE: Carriers are increasingly now viewed as helpful or even essential to improve cellular uptake in connection with antisense tumor targeting and other applications requiring transmembrane delivery of oligomers. Evaluation of many of the large number of available and potentially useful carriers is limited only by the complexities of preparing the oligomer/carriers by covalent conjugation. However, using streptavidin as a linker between biotinylated carriers and biotinylated antisense oligomers would require only simple mixing for preparation. The goal of this study was to evaluate the preparation and cell accumulation in culture of carrier/streptavidin nanoparticle of an antisense phosphorodiamide morpholino (MORF) oligomer. METHODS: The model carriers were cholesterol, a 10 mer HIV-tat peptide, and a 10 mer polyarginine, each having been reported elsewhere to improve cellular delivery of oligomers. The model antisense oligomer was the 25 mer MORF targeting the survivin mRNA. The accumulations of the antisense MORF/carrier nanoparticle were compared to the sense MORF/carrier, to the carrier-free nanoparticles, and to the naked antisense MORF in the survivin-expressing MCF-7 cells. The MORFs and peptides were purchased biotinylated, while the cholesterol was biotinylated in-house. In all cases, the 99mTc radiolabel was placed on the oligomers. Cell studies were performed at low nM concentration as required for antisense imaging applications and at 37 degrees C primarily in 1% FBS. RESULTS: Each radiolabeled oligomer/streptavidin/carrier nanoparticle was successfully prepared by careful mixing at a 1:1 molar ratio. As evidence of carrier participation, the radiolabeled MORF showed increased accumulation in cells when incubated as the nanoparticle compared to the carrier-free nanoparticle and by as much as a factor of 11. Accumulation of the antisense MORF/streptavidin/tat nanoparticle was significantly higher than the sense MORF/streptavidin/tat nanoparticle as evidence of specific antisense targeting. CONCLUSIONS: The preparation of oligomer/carrier nanoparticles was greatly simplified over covalent conjugations by using streptavidin as a linker. Furthermore, our results suggest that the addition of streptavidin did not interfere with the cellular delivery function of the tat, polyarginine, or cholesterol carriers nor with the specific antisense mRNA binding function of the MORF oligomer.

Long circulating nanoparticles via adhesion on red blood cells: mechanism and extended circulation.
Chambers E, Mitragotri S.
Exp Biol Med (Maywood). 2007 Jul;232(7):958-66.
[ expand abstract ]

Polymeric nanoparticles have long been sought after as carriers for systemic and targeted drug delivery. However, applications of nanoparticles are limited by their short in vivo circulation lifetimes. We report that by attaching polymeric nanoparticles to the surface of red blood cells, it is possible to dramatically improve their in vivo circulation lifetime. The particles remain in circulation as long as they remain attached to red blood cells. Particles eventually detach from red blood cells due to shear forces and cell-cell interactions and are subsequently cleared in the liver and spleen. Circulation of red blood cells themselves is not affected by particle attachment procedures. This manuscript reports an in depth analysis of the behavior of nanoparticles bound to red blood cells, especially their circulation characteristics, biodistribution, and mechanisms of clearance.

Continuous production of water dispersible carbon–iron nanocomposites by laser pyrolysis: Application as MRI contrasts.
Y. Lecontea Y, Veintemillas-Verdaguerb S, Moralesb MP, Costob R, Rodríguezc I, Bonvillea P, Bouchet-Fabrea B, Herlin-Boimea N.
J Colloid Interface Sci. 2007 Sep 15; 313(2):511-518.
[ expand abstract ]

Carbon encapsulated iron/iron-oxide nanoparticles were obtained using laser pyrolysis method. The powders were processed to produce stable and biocompatible colloidal aqueous dispersions. The synthesis method consisted in the laser decomposition of an aerosol of ferrocene solution in toluene. This process generated, in a continuous way and in a single step, a nanocomposite formed by amorphous carbon nanoparticles of 50–100 nm size in which isolated iron based nanoparticles of 3–10 nm size are located. The effect of using different carriers and additives was explored in order to improve the efficiency of the process. The samples after purification by solid–liquid extraction with toluene, were oxidised in concentrated nitric acid solution of sodium chlorate, washed and finally ultrasonically dispersed in 1 mM tri-sodium citrate solutions. The dispersions obtained have hydrodynamic particle size less than 150 nm and are stable in the pH range of 2–11. Finally the shortening of the transversal relaxation time of water protons produced by the dispersed particles was studied in order to test the feasibility of these systems to be traced by magnetic resonance imaging techniques.

Strongly emissive individual DNA-encapsulated Ag nanoclusters as single-molecule fluorophores.
Vosch T, Antoku Y, Hsiang JC, Richards CI, Gonzalez JI, Dickson RM.
Proc Natl Acad Sci USA. 2007 Jul 31;104(31):12616-21.
[ expand abstract ]

The water-soluble, near-IR-emitting DNA-encapsulated silver nanocluster presented herein exhibits extremely bright and photostable emission on the single-molecule and bulk levels. The photophysics have been elucidated by intensity-dependent correlation analysis and suggest a heavy atom effect of silver that rapidly depopulates an excited dark level before quenching by oxygen, thereby conferring great photostability, very high single-molecule emission rates, and essentially no blinking on experimentally relevant time scales (0.1 to >1,000 ms). Strong antibunching is observed from these biocompatible species, which emit >10(9) photons before photobleaching. The significant dark-state quantum yield even enables bunching from the emissive state to be observed as a dip in the autocorrelation curve with only a single detector as the dark state precludes emission from the emissive level. These species represent significant improvements over existing dyes, and the nonpower law blinking kinetics suggest that these very small species may be alternatives to much larger and strongly intermittent semiconductor quantum dots.

Design and creation of new nanomaterials for therapeutic RNAi.
Baigude H, McCarroll J, Yang CS, Swain PM, Rana TM.
ACS Chem Biol. 2007 Apr 24;2(4):237-41.
[ expand abstract ]

RNA interference is an evolutionarily conserved gene-silencing phenomenon that shows great promise for developing new therapies. However, the development of small interfering RNA (siRNA)-based therapies needs to overcome two barriers and be able to (i) identify chemically stable and effective siRNA sequences and (ii) efficiently silence target genes with siRNA doses that will be clinically feasible in humans. Here, we report the design and creation of interfering nanoparticles (iNOPs) as new systemic gene-silencing agents. iNOPs have two subunits: (i) a well-defined functionalized lipid nanoparticle as a delivery agent and (ii) a chemically modified siRNA for sustained silencing in vivo. When we injected iNOPs containing only 1-5 mg kg(-1) siRNA into mice, an endogenous gene for apolipoprotein B (apoB) was silenced in liver, plasma levels of apoB decreased, and total plasma cholesterol was lowered. iNOP treatment was nontoxic and did not induce an immune response. Our results show that these iNOPs can silence disease-related endogenous genes in clinically acceptable and therapeutically affordable doses.

Preparation of poly(ethylene glycol)-modified poly(amido amine) dendrimers encapsulating gold nanoparticles and their heat-generating ability.
Haba Y, Kojima C, Harada A, Ura T, Horinaka H, Kono K.
Langmuir. 2007 May 8;23(10):5243-6.
[ expand abstract ]

Loading of HAuCl4 in poly(amido amine) G4 dendrimers having poly(ethylene glycol) (PEG) grafts at all chain ends and subsequent reduction with NaBH4 yielded PEG-modified dendrimers encapsulating gold nanoparticles (Au NPs) of ca. 2 nm diameter. The Au NPs held in the dendrimers were stable in aqueous solutions and dissolved readily, even after freeze-drying. Despite their small particle size, the heat-generating ability of Au NPs held in the dendrimer was comparable to that of widely used Au NPs with ca. 11 nm diameter under visible light irradiation. The observed excellent colloidal stability, high heat-generating ability and their biocompatible surface confirm that the PEG-modified dendrimers encapsulating Au NPs are a promising tool for photothermal therapy and imaging.

Surfactant-polymer nanoparticles: a novel platform for sustained and enhanced cellular delivery of water-soluble molecules.
Chavanpatil MD, Khdair A, Panyam J.
Pharm Res. 2007 Apr;24(4):803-10.
[ expand abstract ]

PURPOSE: Nanoparticles, drug carriers in the sub-micron size range, can enhance the therapeutic efficacy of encapsulated drug by increasing and sustaining the delivery of the drug inside the cell. However, the use of nanoparticles for small molecular weight, water-soluble drugs has been limited by poor drug encapsulation efficiency and rapid release of the encapsulated drug. Here we report enhanced cellular delivery of water-soluble molecules using novel AerosolOT (AOT)-alginate nanoparticles recently developed in our laboratory. MATERIALS AND METHODS: AOT-alginate nanoparticles were formulated using emulsion-crosslinking technology. Rhodamine and doxorubicin were used as model water-soluble molecules. Kinetics and mechanism of nanoparticle-mediated cellular drug delivery and therapeutic efficacy of nanoparticle-encapsulated doxorubicin were evaluated in two model breast cancer cell lines. RESULTS: AOT-alginate nanoparticles demonstrated sustained release of doxorubicin over a 15-day period in vitro. Cell culture studies indicated that nanoparticles enhanced the cellular delivery of rhodamine by about two-tenfold compared to drug in solution. Nanoparticle uptake into cells was dose-, time- and energy-dependent. Treatment with nanoparticles resulted in significantly higher cellular retention of drug than treatment with drug in solution. Cytotoxicity studies demonstrated that doxorubicin in nanoparticles resulted in significantly higher and more sustained cytotoxicity than drug in solution. CONCLUSIONS: AOT-alginate nanoparticles significantly enhance the cellular delivery of basic, water-soluble drugs. This translates into enhanced therapeutic efficacy for drugs like doxorubicin that have intracellular site of action. Based on these results, AOT-alginate nanoparticles appear to be suitable carriers for enhanced and sustained cellular delivery of basic, water-soluble drugs.

Synthesis and assessment of first-generation polyamidoamine dendrimer prodrugs to enhance the cellular permeability of P-gp substrates.
Najlah M, Freeman S, Attwood D, D'Emanuele A.
Bioconjug Chem. 2007 May-Jun;18(3):937-46.
[ expand abstract ]

The aim of this study is to evaluate the potential use of first-generation (G1) polyamidoamine (PAMAM) dendrimers as drug carriers to enhance the permeability, hence oral absorption, of drugs that are substrates for P-glycoprotein (P-gp) efflux transporters. G1 PAMAM dendrimer-based prodrugs of the water-insoluble P-gp substrate terfenadine (Ter) were synthesized using succinic acid (suc) or succinyl-diethylene glycol (suc-deg) as a linker/spacer (to yield G1-suc-Ter and G1-suc-deg-Ter, respectively). In addition, the permeability of G1-suc-deg-Ter was enhanced by attaching two lauroyl chains (L) to the dendrimer surface (L2-G1-suc-deg-Ter). All of the G1 dendrimer-terfenadine prodrugs were more hydrophilic than the parent drug, as evaluated by drug partitioning between 1-octanol and phosphate buffer at pH 7.4 (log K(app)). The influence of the dendrimer prodrugs on the integrity and viability of human Caucasian colon adenocarcinoma cells (Caco-2) was determined by measuring the transepithelial electrical resistance (TEER) and leakage of lactate dehydrogenase (LDH) enzyme, respectively. The LDH assay indicated that the dendrimer prodrugs had no impact on the viability of Caco-2 cells up to a concentration of 1 mM. However, the IC(50) of the prodrugs was lower than that of G1 PAMAM dendrimer because of the high toxicity of terfenadine. Measurements of the transport of dendrimer prodrugs across monolayers of Caco-2 cells showed an increase of the apparent permeability coefficient (P(app)) of terfenadine in both apical-to-basolateral (A --> B) and basolateral-to-apical (B --> A) directions after its conjugation to G1 PAMAM dendrimer. The A --> B P(app) of the dendrimer prodrugs was significantly greater than B --> A P(app). The surface-modified dendrimer prodrug L2-G1-suc-deg-Ter showed the highest A --> B permeability among the conjugates.

Cell-penetrating-peptide-coated nanoribbons for intracellular nanocarriers.
Lim YB, Lee E, Lee M.
Angew Chem Int Ed Engl. 2007;46(19):3475-8.
[ expand abstract ]

No abstract available (Citation link)

A cell nanoinjector based on carbon nanotubes.
Chen X, Kis A, Zettl A, Bertozzi CR.
Proc Natl Acad Sci U S A. 2007 May 15;104(20):8218-22.
[ expand abstract ]

Technologies for introducing molecules into living cells are vital for probing the physical properties and biochemical interactions that govern the cell's behavior. Here, we report the development of a nanoscale cell injection system (termed the nanoinjector) that uses carbon nanotubes to deliver cargo into cells. A single multiwalled carbon nanotube attached to an atomic force microscope (AFM) tip was functionalized with cargo via a disulfide-based linker. Penetration of cell membranes with this "nanoneedle" was controlled by the AFM. The following reductive cleavage of the disulfide bonds within the cell's interior resulted in the release of cargo inside the cells, after which the nanoneedle was retracted by AFM control. The capability of the nanoinjector was demonstrated by injection of protein-coated quantum dots into live human cells. Single-particle tracking was used to characterize the diffusion dynamics of injected quantum dots in the cytosol. This technique causes no discernible membrane or cell damage, and can deliver a discrete number of molecules to the cell's interior without the requirement of a carrier solvent.

Cell-penetrating quantum dots based on multivalent and endosome-disrupting surface coatings.
Duan H, Nie S.
J Am Chem Soc. 2007 Mar 21;129(11):3333-8.
[ expand abstract ]

We report the development of cell-penetrating quantum dots (QDs) based on the use of multivalent and endosome-disrupting (endosomolytic) surface coatings. Hyperbranched copolymer ligands such as polyethylene glycol (PEG) grafted polyethylenimine (PEI-g-PEG) are found to encapsulate and solubilize luminescent quantum dots through direct ligand-exchange reactions. Because of the positive charges and a "proton sponge effect" associated with multivalent amine groups, this class of ligand-exchanged QDs is able to penetrate cell membranes and is also able to disrupt endosomal organelles in living cells. The grafted PEG segment is essential for reducing the cytotoxicity of PEI as well as for improving the overall nanoparticle stability and biocompatibility. In comparison with previous QDs encapsulated with amphiphilic polymers, the cell-penetrating QDs are smaller in size and are considerably more stable in acidic environments. Cellular uptake and imaging studies reveal that the number of PEG grafts per PEI molecule has a pronounced effect on the intracellular pathways of internalized QDs. In particular, QDs coated with PEI-g-PEG2 are rapidly internalized by endocytosis, and are initially stored in vesicles, followed by slow endosomal escape and release into the cytoplasm. These insights are important toward the design and development of nanoparticle agents for intracellular imaging and therapeutic applications.

Live dynamic imaging of caveolae pumping targeted antibody rapidly and specifically across endothelium in the lung.
Oh P, Borgström P, Witkiewicz H, Li Y, Borgström BJ, Chrastina A, Iwata K, Zinn KR, Baldwin R, Testa JE, Schnitzer JE.
Nat Biotechnol. 2007 Mar;25(3):327-37.
[ expand abstract ]

How effectively and quickly endothelial caveolae can transcytose in vivo is unknown, yet critical for understanding their function and potential clinical utility. Here we use quantitative proteomics to identify aminopeptidase P (APP) concentrated in caveolae of lung endothelium. Electron microscopy confirms this and shows that APP antibody targets nanoparticles to caveolae. Dynamic intravital fluorescence microscopy reveals that targeted caveolae operate effectively as pumps, moving antibody within seconds from blood across endothelium into lung tissue, even against a concentration gradient. This active transcytosis requires normal caveolin-1 expression. Whole body gamma-scintigraphic imaging shows rapid, specific delivery into lung well beyond that achieved by standard vascular targeting. This caveolar trafficking in vivo may underscore a key physiological mechanism for selective transvascular exchange and may provide an enhanced delivery system for imaging agents, drugs, gene-therapy vectors and nanomedicines. 'In vivo proteomic imaging' as described here integrates organellar proteomics with multiple imaging techniques to identify an accessible target space that includes the transvascular pumping space of the caveola.

A Highly Selective, One-Pot Purification Method for Single-Walled Carbon Nanotubes.
Wang Y, Shan H, Hauge RH, Pasquali M, Smalley RE.
J Phys Chem B Condens Matter Mater Surf Interfaces Biophys. 2007 Feb 15;111(6):1249-1252.
[ expand abstract ]

We report on a one-pot, highly selective chemistry to remove residual catalysts from single-walled carbon nanotubes (SWNTs). The impurities, initially present at approximately 35 wt % and mostly as carbon-coated iron nanoparticles, can be driven below 5 wt % with nearly no loss of SWNTs. The carbon-coated iron impurities are dissolved simply by reacting with an aqueous mixture of H2O2 and HCl at 40-70 degrees C for 4-8 h. This purification combines two known reactions involving H2O2 and HCl, respectively; however, by combining these two typically inefficient reactions into a one-pot reaction, the new process is surprisingly selective toward the removal of the metal impurities. This high selectivity derives from the proximity effect of the iron-catalyzed Fenton chemistry. At pH approximately 1-3, iron is dissolved upon exposure, avoiding the otherwise aggressive iron-catalyzed digestion of SWNTs by H2O2. This extremely simple and selective chemistry offers a "green" and scalable process to purify carbon nanotube materials.

Multicomponent Nanoparticles via Self-Assembly with Cross-Linked Block Copolymer Surfactants.
Kim BS, Taton TA.
Langmuir. 2007 Feb 13;23(4):2198-202.
[ expand abstract ]

We describe a simple and versatile protocol to prepare water-soluble multifunctional nanostructures by encapsulation of different nanoparticles in shell cross-linked, block copolymer micelles. This method permits simultaneous incorporation of different nanoparticle properties within a nanoscale micellar container. We have demonstrated the co-encapsulation of magnetic (gamma-Fe2O3 and Fe3O4), semiconductor (CdSe/ZnS), and metal (Au) nanoparticles in different combinations to form multicomponent micelles that retain the precursor particles' distinct properties. Because these multifunctional hybrid nanostructures spontaneously assemble from solution by simultaneous desolvation of nanoparticles and amphiphilic block copolymer components, we anticipate that this can be used as a general protocol for preparing multifunctional nanostructures without explicit multimaterial synthesis or surface functionalization of nanoparticles.

Functionalization of monodisperse magnetic nanoparticles.
Lattuada M, Hatton TA.
Langmuir. 2007 Feb 13;23(4):2158-68.
[ expand abstract ]

We report a new strategy for the preparation of monodisperse, water-soluble magnetic nanoparticles. Oleic acid-stabilized magnetic nanocrystals were prepared by the organic synthesis route proposed by Sun et al. (J. Am. Chem. Soc. 2004, 126, 273.), with size control obtained via seeded-mediated growth. The oleic groups initially present on the nanoparticle surfaces were replaced via ligand exchange reactions with various capping agents bearing reactive hydroxyl moieties. These hydroxyl groups were (i) exploited to initiate ring opening polymerization (ROP) of polylactic acid from the nanoparticle surfaces and (ii) esterified by acylation to permit the addition of alkyl halide moieties to transform the nanoparticle surfaces into macroinitiators for atom transfer radical polymerization (ATRP). By appropriate selection of the ligand properties, the nanoparticle surfaces can be polymerized in various solvents, providing an opportunity for the growth of a wide variety of water-soluble polymers and polylectrolyte brushes (both cationic and anionic) from the nanoparticle surfaces. The nanoparticles were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), electron microscopy, and light scattering. Light scattering measurements indicate that the nanoparticles are mostly present as individual nonclustered units in water. With pH-responsive polymers grown on the nanoparticle surfaces, reversible aggregation of nanoparticles could be induced by suitable swings in the pH between the stable and unstable regions.

Highly Luminescent Eu(3+) Chelate Nanoparticles Prepared by a Reprecipitation-Encapsulation Method.
Peng H, Wu C, Jiang Y, Huang S, McNeill J.
Langmuir. 2007 Feb 13;23(4):1591-1595.
[ expand abstract ]

Aqueous suspensions of highly luminescent Eu3+ chelate nanoparticles are prepared by a novel reprecipitation-encapsulation method. An alkyl alkoxysilane encapsulation agent is included during the nanoparticle formation process, forming a nanoparticle encapsulation layer that inhibits aggregation as evidenced by UV-vis spectroscopy and atomic force microscopy. In addition, the encapsulated nanoparticles exhibit a small size (10 nm), intense luminescence, and excellent photostability. We estimate that the molar extinction coefficients of the approximately 10 nm particles are approximately 5.0 x 107 M-1 cm-1 with a luminescence quantum yield of 6%, indicating a luminescence brightness many times larger than that of conventional fluorescent dyes and comparable to that of colloidal semiconductor quantum dots. The small size, high brightness, highly red-shifted luminescence, and long luminescence lifetimes of the nanoparticles are of interest for luminescence labeling and sensing applications.

Synthesis, Stability, and Cellular Internalization of Gold Nanoparticles Containing Mixed Peptide-Poly(ethylene glycol) Monolayers.
Liu Y, Shipton MK, Ryan J, Kaufman ED, Franzen S, Feldheim DL.
Anal Chem. 2007 Feb 9; [Epub ahead of print].
[ expand abstract ]

Gold nanoparticles have shown great promise as therapeutics, therapeutic delivery vectors, and intracellular imaging agents. For many biomedical applications, selective cell and nuclear targeting are desirable, and these remain a significant practical challenge in the use of nanoparticles in vivo. This challenge is being addressed by the incorporation of cell-targeting peptides or antibodies onto the nanoparticle surface, modifications that frequently compromise nanoparticle stability in high ionic strength biological media. We describe herein the assembly of poly(ethylene glycol) (PEG) and mixed peptide/PEG monolayers on gold nanoparticle surfaces. The stability of the resulting bioconjugates in high ionic strength media was characterized as a function of nanoparticle size, PEG length, and monolayer composition. In total, three different thiol-modified PEGs (average molecular weight (MW), 900, 1500, and 5000 g mol-1), four particle diameters (10, 20, 30, and 60 nm), and two cell-targeting peptides were explored. We found that nanoparticle stability increased with increasing PEG length, decreasing nanoparticle diameter, and increasing PEG mole fraction. The order of assembly also played a role in nanoparticle stability. Mixed monolayers prepared via the sequential addition of PEG followed by peptide were more stable than particles prepared via simultaneous co-adsorption. Finally, the ability of nanoparticles modified with mixed PEG/RME (RME = receptor-mediated endocytosis) peptide monolayers to target the cytoplasm of HeLa cells was quantified using inductively coupled plasma optical emission spectrometry (ICP-OES). Although it was anticipated that the MW 5000 g mol-1 PEG would sterically block peptides from access to the cell membrane compared to the MW 900 PEG, nanoparticles modified with mixed peptide/PEG 5000 monolayers were internalized as efficiently as nanoparticles containing mixed peptide/PEG 900 monolayers. These studies can provide useful cues in the assembly of stable peptide/gold nanoparticle bioconjugates capable of being internalized into cells.

Biopolymer-based materials: the nanoscale components and their hierarchical assembly.
Payne GF.
Curr Opin Chem Biol. 2007 Feb 9; [Epub ahead of print].
[ expand abstract ]

Protein and nucleic acid biopolymers are well appreciated for their high-performance capabilities for molecular recognition, catalysis and information storage. Increasingly, these biopolymers are being examined for materials applications. Less tractable are polysaccharides and polymers of phenols, which, despite being nature's most abundant macromolecules, remain largely ignored for advanced materials applications. In our opinion, it seems certain that biology will contribute two major capabilities for materials biofabrication - the means to generate biopolymeric components with nanoscale precision, and the mechanisms for the hierarchical assembly of nanocomponents. These capabilities will enable unprecedented control of materials structure and provide exciting opportunities at the convergence of molecular biology and macromolecular science.

Dendrimers as multi-purpose nanodevices for oncology drug delivery and diagnostic imaging.
Tomalia DA, Reyna LA, Svenson S.
Biochem Soc Trans. 2007 Feb;35(Pt 1):61-7.
[ expand abstract ]

Dendrimers are routinely synthesized as tuneable nanostructures that may be designed and regulated as a function of their size, shape, surface chemistry and interior void space. They are obtained with structural control approaching that of traditional biomacromolecules such as DNA/RNA or proteins and are distinguished by their precise nanoscale scaffolding and nanocontainer properties. As such, these important properties are expected to play an important role in the emerging field of nanomedicine. This review will describe progress on the use of these features for both targeted diagnostic imaging and drug-delivery applications. Recent efforts have focused on the synthesis and pre-clinical evaluation of a multipurpose STARBURST(R) PAMAM (polyamidoamine) dendrimer prototype that exhibits properties suitable for use as: (i) targeted, diagnostic MRI (magnetic resonance imaging)/NIR (near-IR) contrast agents, (ii) and/or for controlled delivery of cancer therapies. Special emphasis will be placed on the lead candidate, namely [core: 1,4-diaminobutane; G (generation)=4.5], [dendri-PAMAM(CO(2)Na)(64)]. This dendritic nanostructure (i.e. approximately 5.0 nm diameter) was selected on the basis of a very favourable biocompatibility profile [The Nanotechnology Characterization Laboratory (NCL), an affiliate of the National Cancer Institute (NCI), has completed extensive in vitro studies on the lead compound and have found it to be very benign, non-immunogenic and highly biocompatible], the expectation that it will exhibit desirable mammalian kidney excretion properties and demonstrated targeting features.

Understanding the nanoparticle-protein corona using methods to quantify exchange rates and affinities of proteins for nanoparticles.
Cedervall T, Lynch I, Lindman S, Berggard T, Thulin E, Nilsson H, Dawson KA, Linse S.
Proc Natl Acad Sci USA. 2007 Jan 31; [Epub ahead of print].
[ expand abstract ]

Due to their small size, nanoparticles have distinct properties compared with the bulk form of the same materials. These properties are rapidly revolutionizing many areas of medicine and technology. Despite the remarkable speed of development of nanoscience, relatively little is known about the interaction of nanoscale objects with living systems. In a biological fluid, proteins associate with nanoparticles, and the amount and presentation of the proteins on the surface of the particles leads to an in vivo response. Proteins compete for the nanoparticle "surface," leading to a protein "corona" that largely defines the biological identity of the particle. Thus, knowledge of rates, affinities, and stoichiometries of protein association with, and dissociation from, nanoparticles is important for understanding the nature of the particle surface seen by the functional machinery of cells. Here we develop approaches to study these parameters and apply them to plasma and simple model systems, albumin and fibrinogen. A series of copolymer nanoparticles are used with variation of size and composition (hydrophobicity). We show that isothermal titration calorimetry is suitable for studying the affinity and stoichiometry of protein binding to nanoparticles. We determine the rates of protein association and dissociation using surface plasmon resonance technology with nanoparticles that are thiol-linked to gold, and through size exclusion chromatography of protein-nanoparticle mixtures. This method is less perturbing than centrifugation, and is developed into a systematic methodology to isolate nanoparticle-associated proteins. The kinetic and equilibrium binding properties depend on protein identity as well as particle surface characteristics and size.

Biomolecule-nanoparticle hybrids as functional units for nanobiotechnology.
Baron R, Willner B, Willner I.
Chem Commun (Camb). 2007 Jan 28;(4):323-32.
[ expand abstract ]

Biomolecule-metal or semiconductor nanoparticle (NP) hybrid systems combine the recognition and catalytic properties of biomolecules with the unique electronic and optical properties of NPs. This enables the application of the hybrid systems in developing new electronic and optical biosensors, to synthesize nanowires and nanocircuits, and to fabricate new devices. Metal NPs are employed as nano-connectors that activate redox enzymes, and they act as electrical or optical labels for biorecognition events. Similarly, semiconductor NPs act as optical probes for biorecognition processes. Double-stranded DNA or protein chains that are modified with metallic nanoclusters act as templates for the synthesis of metallic nanowires. The nanowires are used as building blocks to assemble nano-devices such as a transistor or a nanotransporter.

Nanotechnological applications in medicine.
Caruthers SD, Wickline SA, Lanza GM.
Curr Opin Biotechnol. 2007 Jan 23; [Epub ahead of print].
[ expand abstract ]

Nanotechnology-based tools and techniques are rapidly emerging in the fields of medical imaging and targeted drug delivery. Employing constructs such as dendrimers, liposomes, nanoshells, nanotubes, emulsions and quantum dots, these advances lead toward the concept of personalized medicine and the potential for very early, even pre-symptomatic, diagnoses coupled with highly-effective targeted therapy. Highlighting clinically available and preclinical applications, this review explores the opportunities and issues surrounding nanomedicine.

Fullerene-Derivatized Amino Acids: Synthesis, Characterization, Antioxidant Properties, and Solid-Phase Peptide Synthesis.
Yang J, Alemany LB, Driver J, Hartgerink JD, Barron AR.
Chemistry. 2007 Jan 19; [Epub ahead of print].
[ expand abstract ]

A series of [60]fullerene-substituted phenylalanine (Baa) and lysine derivatives have been prepared by the condensation of 1,2-(4'-oxocyclohexano)fullerene with the appropriately protected (4-amino)phenylalanine and lysine, respectively. Conversion of the imine to the corresponding amine is achieved by di-acid catalyzed hydroboration. The reduction of the imine is not accompanied by hydroboration of the fullerene cage. The [70]fullerene phenylalanine derivative has also been prepared as have the di-amino acid derivatives. The compounds were characterized by MALDI-TOF mass spectrometry, UV/Vis spectroscopy, and cyclic voltammetry. (1)H and (13)C NMR spectroscopy allowed the observation of diastereomers. Fullerene-substituted peptides may be synthesized on relatively large scale by solid-phase peptide synthesis. The presence of the C(60)-substituted amino acid in a peptide has a significant effect on the secondary structures and self-assembly properties of peptides as compared to the native peptide. The antioxidant assay of Baa and a Baa-derived anionic peptide was determined to be significantly more potent than Trolox.

Synthesis and temperature response analysis of magnetic-hydrogel nanocomposites.
Frimpong RA, Fraser S, Zach Hilt J.
J Biomed Mater Res A. 2007 Jan;80(1):1-6.
[ expand abstract ]

Magnetically responsive hydrogel networks based on composites of magnetic nanoparticles and temperature responsive hydrogels were developed. These systems show great promise as active components of microscale and nanoscale devices and are expected to have a wide applicability in various biomedical applications. Specifically, nanocomposite hydrogel systems based on the temperature sensitive N-isopropylacrylamide hydrogels crosslinked with ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and poly(ethylene glycol) 400 dimethacrylate (PEG400DMA) were synthesized and characterized. The composite systems were synthesized by UV free-radical polymerization. Iron oxide magnetic nanoparticles were incorporated into the hydrogel systems by polymerizing mixtures of the nanoparticles and monomer solutions. The swelling response of these composite systems to different crosslinking molecular weights, temperature, and the effect of the presence of the magnetic nanoparticles were examined.

Quenching of photoluminescence in conjugates of quantum dots and single-walled carbon nanotube.
Biju V, Itoh T, Baba Y, Ishikawa M.
J Phys Chem B Condens Matter Mater Surf Interfaces Biophys.
2006 Dec 28;110(51):26068-74.
[ expand abstract ]

Development of quantum dot (QD) based device components requires controlled integration of QDs into different photonic and electronic materials. In this regard, introduction of methods for regular arrangement of QDs and investigation of properties of QD-based assemblies are important. In the current work we report (1) controlled conjugation of CdSe-ZnS QDs to sidewall-functionalized single-walled carbon nanotube (SWCNT) templates (2) and the effect of conjugation of QDs to SWCNT on the photoluminescence (PL) properties of QDs. We identified that PL intensity and lifetime of QDs are considerably reduced after conjugation to SWCNT. The origin of the quenching of the PL intensity and lifetime was discussed in terms of Forster resonance energy transfer (FRET). FRET involves nonradiative transfer of energy from a photoexcited QD (energy donor) to a nearby SWCNT (energy acceptor) in the ground state. This was examined by varying the density of QDs on SWCNT and conjugating smaller and bigger QDs to the same SWCNT. We estimated the FRET efficiency in QD-SWCNT conjugates from the quenching of the PL intensity and lifetime and identified that FRET is independent of the density and type of QDs on SWCNT but inherent to QD-SWCNT conjugates.

Template synthesized molecularly imprinted polymer nanotube membranes for chemical separations.
Wang HJ, Zhou WH, Yin XF, Zhuang ZX, Yang HH, Wang XR.
J Am Chem Soc. 2006 Dec 20;128(50):15954-5.
[ expand abstract ]

No abstract available

Nanoparticle-enzyme hybrid systems for nanobiotechnology.
Willner I, Basnar B, Willner B.
FEBS J. 2006 Dec 20; [Epub ahead of print].
[ expand abstract ]

Biomolecule-nanoparticle (NP) [or quantum-dot (QD)] hybrid systems combine the recognition and biocatalytic properties of biomolecules with the unique electronic, optical, and catalytic features of NPs and yield composite materials with new functionalities. The biomolecule-NP hybrid systems allow the development of new biosensors, the synthesis of metallic nanowires, and the fabrication of nanostructured patterns of metallic or magnetic NPs on surfaces. These advances in nanobiotechnology are exemplified by the development of amperometric glucose sensors by the electrical contacting of redox enzymes by means of AuNPs, and the design of an optical glucose sensor by the biocatalytic growth of AuNPs. The biocatalytic growth of metallic NPs is used to fabricate Au and Ag nanowires on surfaces. The fluorescence properties of semiconductor QDs are used to develop competitive maltose biosensors and to probe the biocatalytic functions of proteases. Similarly, semiconductor NPs, associated with electrodes, are used to photoactivate bioelectrocatalytic cascades while generating photocurrents.

Adsorption and hybridization of oligonucleotides on mercaptoacetic acid-capped CdSe/ZnS quantum dots and quantum dot-oligonucleotide conjugates.
Algar WR, Krull UJ.
Langmuir. 2006 Dec 19;22(26):11346-52.
[ expand abstract ]

Interest in the unique optical properties of quantum dots (QDs) has resulted in the development QD-bioconjugates for imaging and diagnostics. Although these applications are numerous, considerably less is known about the interactions between QDs and biomolecules. In this work, we describe hydrogen-bonding interactions between oligonucleotides and CdSe/ZnS quantum dots capped with mercaptoacetic acid ligands. The strength of the interactions can be modulated by changes in the pH and ionic strength, the addition of formamide, and differences between ssDNA and dsDNA. Fluorescence resonance energy transfer experiments have shown that conjugated oligonucleotides adopt a conformation that lies across the surface of the QD. The hydrogen-bonding interactions also affect the kinetics of hybridization with QD-DNA conjugates and the thermal stability of QD-conjugated dsDNA. The former is analogous to conventional solid-phase hybridization, where stronger oligonucleotide adsorption leads to faster kinetics. With respect to the latter, interactions with the QD surface can sharpen the melt transition and alter the melt temperature of dsDNA. These effects are largely absent when adsorptive interactions are minimized.

Arylthiolate-protected silver quantum dots.
Branham MR, Douglas AD, Mills AJ, Tracy JB, White PS, Murray RW.
Langmuir. 2006 Dec 19;22(26):11376-83.
[ expand abstract ]

This paper describes a new, organic-soluble 4-tert-butylbenzyl mercaptan (BBT) monolayer-protected silver cluster (AgBBT MPC) as the first example of a dissolved silver nanoparticle that exhibits quantized one-electron double layer charging (QDL) voltammetry. Polydisperse AgBBT MPCs made by two different synthetic protocols, but with similar average core diameters (2.1 nm), exhibit sharply differing electrochemistry and optical absorbance spectra. A two-phase procedure (organic/aqueous, termed Prep A-AgBBT) produced MPCs exhibiting a 475 nm surface plasmon absorbance and QDL voltammetry. Neither property was seen for MPCs made by a single-phase procedure, termed Prep B-AgBBT. The difference is thought to reflect poor passivation to oxide formation in the latter Prep B procedure, which is supported by X-ray photoelectron spectroscopy results. Thermogravimetry, mass spectra, and electrochemistry results suggest an average stoichiometric formula of Ag140BBT53, but transmission electron microscopy shows that the products are also polydisperse and include polycrystalline aggregates. Dry, cast films of both Ag MPC preparations on interdigitated array electrodes exhibit low electron hopping conductivity, compared to Au MPCs.

Optimization of the methods for introduction of amine groups onto the silica nanoparticle surface.
Liu S, Zhang HL, Liu TC, Liu B, Cao YC, Huang ZL, Zhao YD, Luo QM.
J Biomed Mater Res A. 2006 Dec 19; [Epub ahead of print].
[ expand abstract ]

The luminescent silica nanoparticle has attracted the researchers' concentration in bioanalysis recently. Its extensive application is based on the immobilization of various biomolecules such as deoxyribonucleic acid, antibody, and so forth onto the surface. By comparing different introduction methods of amine groups, it was confirmed that the "two-step" route is more preferable by adding tetraethyl orthosilicate and 3-aminopropyl-(triethoxyl)silane in sequence, to attain ideal amine-modified silica nanoparticles. On this basis, carboxyl groups were derived from amine groups on the nanoparticle surface and then were activated by 1-ethyl-3-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxy-succinimide. Finally, mouse monoclonal antihuman CD71 antibody (McAb CD71) and transferrin were effectively linked with the carboxyl groups and successfully labeled the receptors in the membrane of fibroblast cells, respectively.

Maximizing DNA loading on a range of gold nanoparticle sizes.
Hurst SJ, Lytton-Jean AK, Mirkin CA.
Anal Chem. 2006 Dec 15;78(24):8313-8.
[ expand abstract ]

We have investigated the variables that influence DNA coverage on gold nanoparticles. The effects of salt concentration, spacer composition, nanoparticle size, and degree of sonication have been evaluated. Maximum loading was obtained by salt aging the nanoparticles to approximately 0.7 M NaCl in the presence of DNA containing a poly(ethylene glycol) spacer. In addition, DNA loading was substantially increased by sonicating the nanoparticles during the surface loading process. Last, nanoparticles up to 250 nm in diameter were found have approximately 2 orders of magnitude higher DNA loading than smaller (13-30 nm) nanoparticles, a consequence of their larger surface area. Stable large particles are attractive for a variety of biodiagnostic assays.

Back to Top

Development of High Magnetization Fe(3)O(4)/Polystyrene/Silica Nanospheres via Combined Miniemulsion/Emulsion Polymerization.
Xu H, Cui L, Tong N, Gu H.
J Am Chem Soc. 2006 Dec 13;128(49):15582-3.
[ expand abstract ]

Monodispersed, hydrophilic, superparamagnetic magnetic nanospheres with a high fraction of magnetite were synthesized by combining modified miniemulsion/emulsion polymerization and sol-gel technique for the first time. The surface of the nanospheres was coated by a silica layer with controlled thickness. Transmission electron microscopy experimental results showed well-proportioned, equal-sized, magnetite/polystyrene (Fe3O4/PS) nanospheres with a thin silica shell. Based on the TGA data, the fraction of magnetite in the Fe3O4/PS nanospheres core was estimated to be 80 wt %. Magnetization measurements indicated that the superparamagnetic nature of the nanospheres had high saturation magnetization of 40 emu/g at 300 K. The procedures of the novel synthesis are described in detail. Also discussed are the mechanisms of the novel combined miniemulsion/emulsion polymerization processes.

Quantitative measurement and control of oxygen levels in microfluidic poly(dimethylsiloxane) bioreactors during cell culture.
Mehta G, Mehta K, Sud D, Song JW, Bersano-Begey T, Futai N, Heo YS, Mycek MA, Linderman JJ, Takayama S.
Biomed Microdevices. 2006 Dec 12; [Epub ahead of print].
[ expand abstract ]

Microfluidic bioreactors fabricated from highly gas-permeable poly(dimethylsiloxane) (PDMS) materials have been observed, somewhat unexpectedly, to give rise to heterogeneous long term responses along the length of a perfused mammalian cell culture channel, reminiscent of physiologic tissue zonation that arises at least in part due to oxygen gradients. To develop a more quantitative understanding and enable better control of the physical-chemical mechanisms underlying cell biological events in such PDMS reactors, dissolved oxygen concentrations in the channel system were quantified in real time using fluorescence intensity and lifetime imaging of an oxygen sensitive dye, ruthenium tris(2,2'-dipyridyl) dichloride hexahydrate (RTDP). The data indicate that despite oxygen diffusion through PDMS, uptake of oxygen by cells inside the perfused PDMS microchannels induces an axial oxygen concentration gradient, with lower levels recorded in downstream regions. The oxygen concentration gradient generated by a balance of cellular uptake, convective transport by media flow, and permeation through PDMS in our devices ranged from 0.0003 (mg/l)/mm to 0.7 (mg/l)/mm. The existence of such steep gradients induced by cellular uptake can have important biological consequences. Results are consistent with our mathematical model and give insight into the conditions under which flux of oxygen through PDMS into the microchannels will or will not contribute significantly to oxygen delivery to cells and also provide a design tool to manipulate and control oxygen for cell culture and device engineering. The combination of computerized microfluidics, in situ oxygen sensing, and mathematical models opens new windows for microphysiologic studies utilizing oxygen gradients and low oxygen tensions.

Micropatterned surfaces for controlling cell adhesion and rolling under flow.
Nalayanda DD, Kalukanimuttam M, Schmidtke DW.
Biomed Microdevices. 2006 Dec 12; [Epub ahead of print].
[ expand abstract ]

Cell adhesion and rolling on the vascular wall is critical to both inflammation and thrombosis. In this study we demonstrate the feasibility of using microfluidic patterning for controlling cell adhesion and rolling under physiological flow conditions. By controlling the width of the lines (50-1000 mum) and the spacing between them (50-100 mum) we were able to fabricate surfaces with well-defined patterns of adhesion molecules. We demonstrate the versatility of this technique by patterning surfaces with 3 different adhesion molecules (P-selectin, E-selectin, and von Willebrand Factor) and controlling the adhesion and rolling of three different cell types (neutrophils, Chinese Hamster Ovary cells, and platelets). By varying the concentration of the incubating solution we could control the surface ligand density and hence the cell rolling velocity. Finally by patterning surfaces with both P-selectin and von Willebrand Factor we could control the rolling of both leukocytes and platelets simultaneously. The technique described in this paper provides and effective and inexpensive way to fabricate patterned surfaces for use in cell rolling assays under physiologic flow conditions.

Truncated forms of viral VP2 proteins fused to EGFP assemble into fluorescent parvovirus-like particles.
Gilbert L, Toivola J, Valilehto O, Saloniemi T, Cunningham C, White D, Makela AR, Korhonen E, Vuento M, Oker-Blom C.
J Nanobiotechnology. 2006 Dec 8;4(1):13 [Epub ahead of print].
[ expand abstract ]

ABSTRACT: Fluorescence correlation spectroscopy (FCS) monitors random movements of fluorescent molecules in solution, giving information about the number and the size of for example nano-particles. The canine parvovirus VP2 structural protein as well as N-terminal deletion mutants of VP2 (-14, -23, and -40 amino acids) were fused to the C-terminus of the enhanced green fluorescent protein (EGFP). The proteins were produced in insect cells, purified, and analyzed by western blotting, confocal and electron microscopy as well as FCS. The non-truncated form, EGFP-VP2, diffused with a hydrodynamic radius of 17 nm, whereas the fluorescent mutants truncated by 14, 23 and 40 amino acids showed hydrodynamic radii of 7, 20 and 14 nm, respectively. These results show that the non-truncated EGFP-VP2 fusion protein and the EGFP-VP2 constructs truncated by 23 and by as much as 40 amino acids were able to form virus-like particles (VLPs). The fluorescent VLP, harbouring VP2 truncated by 23 amino acids, showed a somewhat larger hydrodynamic radius compared to the non-truncated EGFP-VP2. In contrast, the construct containing EGFP-VP2 truncated by 14 amino acids was not able to assemble into VLP resembling structures. Formation of capsid structures was confirmed by confocal and electron microscopy. The number of fluorescent fusion protein molecules present within the different VLPs was determined by FCS. In conclusion, FCS provides a novel strategy to analyze virus assembly and gives valuable structural information for strategic development of parvovirus-like particles.

Aggregated CdS Quantum Dots: Host of Biomolecular Ligands.
Narayanan SS, Pal SK.
J Phys Chem B Condens Matter Mater Surf Interfaces Biophys. 2006 Dec 7;110(48):24403-9.
[ expand abstract ]

In this contribution, we have studied structural and photophysical properties of aggregated CdS quantum dots (QDs) capped with 2-mercaptoethanol in aqueous medium. The hydrodynamic diameter of the nanostructures in aqueous solution was found to be approximately 160 nm with the dynamic light scattering (DLS) technique, which is in close agreement with atomic force microscopy (AFM) studies (diameter approximately 150 nm). However, the UV-vis absorption spectroscopy, powder X-ray diffraction (XRD), and transmission electron microscopy (TEM) studies confirm the average particle size (QD) in the nanoaggregate to be 4.0 +/- 0.5 nm. The steady-state and time-resolved photoluminescence studies on the QDs further confirm preservation of electronic band structure of the QDs in the nanoaggregate. To study the nature of the nanoaggregate we have used small fluorescent probes, which are widely used as biomolecular ligands (2,6-p-toluidinonaphthalene sulfonate (TNS) and Oxazine 1), and found the pores of the aggregate to be hydrophobic in nature. The significantly large spectral overlap of the host quantum dots (donor) with that of the guest fluorescent probe Oxazine 1 (acceptor) allows us to carry out Forster resonance energy transfer (FRET) studies to estimate average donor-acceptor distance in the nanostructure, found to be approximately 25 A. The quantum dot aggregate and the characterization techniques reported here could have implications in the future application of the QD-nanoaggregate as host of small ligand molecules of biological interest.

Compact, high performance surface plasmon resonance imaging system.
Chinowsky TM, Grow MS, Johnston KS, Nelson K, Edwards T, Fu E, Yager P.
Biosens Bioelectron. 2006 Dec 4; [Epub ahead of print].
[ expand abstract ]

We report the construction and characterization of a new compact surface plasmon resonance imaging instrument. Surface plasmon resonance imaging is a versatile technique for detection, quantification and visualization of biomolecular binding events which have spatial structure. The imager uses a folded light path, wide-field optics and a tilted detector to implement a high performance optical system in a volume 7in.x4in.x2in. A bright diode light source and an image detector with fast frame rate and integrated digital signal processor enable real-time averaging of multiple images for improved signal-to-noise ratio. Operating angle of the imager is adjusted by linear translation of the light source. Imager performance is illustrated using resolution test targets, refractive index test solutions, and competition assays for the antiepileptic drug phenytoin. Microfluidic flowcells are used to enable simultaneous assay of three sample streams. Noise level of refractive index measurements was found to decrease proportional to the square root of the number of pixels averaged, reaching approximately 5x10(-7) refractive index units root-mean-square for 160x120 pixels image regions imaged for 1s. The simple, compact construction and high performance of the imager will allow the device to be readily applied to a wide range of applications.

Electrohydrodynamic Generation and Delivery of Monodisperse Picoliter Droplets Using a Poly(dimethylsiloxane) Microchip.
Kim SJ, Song YA, Skipper PL, Han J.
Anal Chem. 2006 Dec 1;78(23):8011-9.
[ expand abstract ]

We developed a drop-on-demand microdroplet generator for the discrete dispensing of biosamples into a bioanalytical unit. This disposable PDMS microfluidic device can generate monodisperse droplets of picoliter volume directly out of a plane sidewall of the microfluidic chip by an electrohydrodynamic mechanism. The droplet generation was accomplished without using either an inserted capillary or a monolithically built-in tip. The minimum droplet volume was approximately 4 pL, and the droplet generation was repeatable and stable for at least 30 min, with a typical variation of less than 2.0% of drop size. The Taylor cone, which is usually observed in electrospray, was suppressed by controlling the surface wetting property of the PDMS device as well as the surface tension of the sample liquids. A modification of the channel geometry right before the opening of the microchannel also enhanced the continuous droplet generation without applying any external pumping. A simple numerical simulation of the droplet generation verified the importance of controlling the surface wetting conditions for the droplet formation. Our microdroplet generator can be effectively applied to a direct interface of a microfluidic chip to a biosensing unit, such as AMS, MALDI-MS or protein microarray-type biochips.

Separation of acidic and basic proteins by nanoparticle-filled capillary electrophoresis.
Yu CJ, Su CL, Tseng WL.
Anal Chem. 2006 Dec 1;78(23):8004-10.
[ expand abstract ]

We present the first example of the analysis of acidic and basic proteins by nanoparticle-filled capillary electrophoresis. Compared to the didodecyldimethylammonium bromide (DDAB)-coated capillary, the DDAB-capped gold nanoparticles (AuNPs) as pseudostationary phase were found to form more stable coating on the capillary wall, thus leading to greater separation efficiency and high reproducibility. In addition to their advantages for protein separation, DDAB-capped AuNPs can generate high reversed electroosmotic flow, which is 75% greater than DDAB at pH 3.5. To allow strong interactions with proteins, the AuNPs were modified with poly(ethylene oxide) via noncovalent bonding to form gold nanoparticles/polymer composites (AuNPPs). Using a capillary dynamically coated with DDAB-capped AuNPs and filled with AuNPPs under acidic conditions (10 mM phosphate, pH 3.5), we have demonstrated the separation of acidic and basic proteins with peak efficiencies ranging from 71 000 to 1 007 000 plates/m and relative standard deviations of migration time less than 0.6%. Additionally, the proposed method has been applied to the analyses of biological samples, including saliva, red blood cells, and plasma. With simplicity, high resolving power, and high reproducibility, the proposed method has shown great potential for proteomics applications and clinical diagnosis.

Combined microfluidic-micromagnetic separation of living cells in continuous flow.
Xia N, Hunt TP, Mayers BT, Alsberg E, Whitesides GM, Westervelt RM, Ingber DE.
Biomed Microdevices. 2006 Dec;8(4):299-308.
[ expand abstract ]

This paper describes a miniaturized, integrated, microfluidic device that can pull molecules and living cells bound to magnetic particles from one laminar flow path to another by applying a local magnetic field gradient, and thus selectively remove them from flowing biological fluids without any wash steps. To accomplish this, a microfabricated high-gradient magnetic field concentrator (HGMC) was integrated at one side of a microfluidic channel with two inlets and outlets. When magnetic micro- or nano-particles were introduced into one flow path, they remained limited to that flow stream. In contrast, when the HGMC was magnetized, the magnetic beads were efficiently pulled from the initial flow path into the collection stream, thereby cleansing the original fluid. Using this microdevice, living E. coli bacteria bound to magnetic nanoparticles were efficiently removed from flowing solutions containing densities of red blood cells similar to that found in blood. Because this microdevice allows large numbers of beads and cells to be sorted simultaneously, has no capacity limit, and does not lose separation efficiency as particles are removed, it may be especially useful for separations from blood or other clinical samples. This on-chip HGMC-microfluidic separator technology may potentially allow cell separations to be carried out in the field outside of hospitals and clinical laboratories.

Time-Controlled Microfluidic Seeding in nL-Volume Droplets To Separate Nucleation and Growth Stages of Protein Crystallization.
Gerdts CJ, Tereshko V, Yadav MK, Dementieva I, Collart F, Joachimiak A, Stevens RC, Kuhn P, Kossiakoff A, Ismagilov RF.
Angew Chem Int Ed Engl. 2006 Nov 13; [Epub ahead of print].
[ expand abstract ]

No abstract available

A Versatile Approach for the Preparation of Thermosensitive PNIPAM Core-Shell Microgels with Nanoparticle Cores.
Karg M, Pastoriza-Santos I, Liz-Marzan LM, Hellweg T.
Chemphyschem. 2006 Nov 13;7(11):2298-2301.
[ expand abstract ]

No abstract available

A Review of Poloxamer 407 Pharmaceutical and Pharmacological Characteristics.
Dumortier G, Grossiord JL, Agnely F, Chaumeil JC.
Pharm Res. 2006 Nov 11; [Epub ahead of print].
[ expand abstract ]

Poloxamer 407 copolymer (ethylene oxide and propylene oxide blocks) shows thermoreversible properties, which is of the utmost interest in optimising drug formulation (fluid state at room temperature facilitating administration and gel state above sol-gel transition temperature at body temperature promoting prolonged release of pharmacological agents). Pharmaceutical evaluation consists in determining the rheological behaviour (flow curve or oscillatory studies), sol-gel transition temperature, in vitro drug release using either synthetic or physiological membrane and (bio)adhesion characteristics. Poloxamer 407 formulations led to enhanced solubilisation of poorly water-soluble drugs and prolonged release profile for many galenic applications (e.g., oral, rectal, topical, ophthalmic, nasal and injectable preparations) but did not clearly show any relevant advantages when used alone. Combination with other excipients like Poloxamer 188 or mucoadhesive polymers promotes Poloxamer 407 action by optimising sol-gel transition temperature or increasing bioadhesive properties. Inclusion of liposomes or micro(nano)particles in Poloxamer 407 formulations offers interesting prospects, as well. Besides these promising data, Poloxamer 407 has been held responsible for lipidic profile alteration and possible renal toxicity, which compromises its development for parenteral applications. In addition, new findings have demonstrated immuno-modulation and cytotoxicity-promoting properties of Poloxamer 407 revealing significant pharmacological interest and, hence, human trials are in progress to specify these potential applications.

External force-assisted cell positioning inside microfluidic devices.
Rhee SW, Taylor AM, Cribbs DH, Cotman CW, Jeon NL.
Biomed Microdevices. 2006 Nov 8; [Epub ahead of print].
[ expand abstract ]

This paper describes straightforward approaches to positioning cells within microfluidic devices that can be implemented without special equipment or fabrication steps. External forces can effectively transport and position cells in preferred locations inside microfluidic channels. Except for centrifugal force-based positioning that can be used with any microfluidic channels, hydrodynamic and gravitational force-based positioning yield reproducible and biocompatible results when implemented with a microfluidic "module" that contains a barrier with embedded microgrooves. Primary rat cortical neurons, metastatic human breast cancer cells MDA-MB-231, NIH 3T3 mouse fibroblasts, and human umbilical vein endothelial cells (HUVECs) were compatible with the positioning processes. After positioning, cells attached, proliferated and migrated like control cells that were cultured on tissue culture dishes or glass coverslips. No apparent morphological differences were observed in positioned cells compared with control cells. Finally, to demonstrate a practical application of the methods, cells were placed in a single row along a wall inside a microfluidic chemotaxis chamber (MCC), and were exposed to stable concentration gradient of chemoattractant. Cell positioning allows that all cells get exposed to the same level of chemoattractant at the start of the experiment helping standardize cellular response.

Hormone-PAMAM Dendrimer Conjugates: Polymer Dynamics and Tether Structure Affect Ligand Access to Receptors.
Kim SH, Katzenellenbogen JA.
Angew Chem Int Ed Engl. 2006 Nov 6;45(43):7243-7248.
[ expand abstract ]

No abstract available

Massively Parallel Dip-Pen Nanolithography with 55 000-Pen Two-Dimensional Arrays.
Salaita K, Wang Y, Fragala J, Vega RA, Liu C, Mirkin CA.
Angew Chem Int Ed Engl. 2006 Nov 6;45(43):7220-7223.
[ expand abstract ]

No abstract available

Quantitative multispectral biosensing and 1D imaging using quasi-3D plasmonic crystals.
Stewart ME, Mack NH, Malyarchuk V, Soares JA, Lee TW, Gray SK, Nuzzo RG, Rogers JA.
Proc Natl Acad Sci SA. 2006 Nov 3; [Epub ahead of print].
[ expand abstract ]

We developed a class of quasi-3D plasmonic crystal that consists of multilayered, regular arrays of subwavelength metal nanostructures. The complex, highly sensitive structure of the optical transmission spectra of these crystals makes them especially well suited for sensing applications. Coupled with quantitative electrodynamics modeling of their optical response, they enable full multiwavelength spectroscopic detection of molecular binding events with sensitivities that correspond to small fractions of a monolayer. The high degree of spatial uniformity of the crystals, formed by a soft nanoimprint technique, provides the ability to image binding events over large areas with micrometer spatial resolution. These features, together with compact form factors, low-cost fabrication procedures, simple readout apparatus, and ability for direct integration into microfluidic networks and arrays, suggest promise for these devices in label-free bioanalytical detection systems.

Biocompatible superparamagnetic iron oxide nanoparticle dispersions stabilized with poly(ethylene glycol)-oligo(aspartic acid) hybrids.
Wan S, Huang J, Guo M, Zhang H, Cao Y, Yan H, Liu K.
J Biomed Mater Res A. 2006 Nov 2; [Epub ahead of print].
[ expand abstract ]

Methoxypoly(ethylene glycol)-oligo(aspartic acid) (MPEG-Asp(n)-NH(2), n = 2-5) hybrid block copolymers were synthesized and used as stabilizers to prepare superparamagnetic Fe(3)O(4) nanoparticles with magnetite as the inner core and and poly(ethylene glycol) as the hydrophilic outer shell. The aqueous dispersions of the nanoparticles were stable at pH 2-11 and in 1M NaCl solution, when repeat number, n, was 3 or more. Transmission electron microscopy showed that the nanoparticles, stabilized with MPEG-Asp(3)-NH(2), were about 14 nm in diameter. Magnetic measurements indicated that MPEG-Asp(3)-NH(2)-coated iron oxide nanoparticles showed superparamagnetic behavior. Cell adhesion assay and in vitro cell viability/cytotoxicity studies showed that MPEG-Asp(3)-NH(2)-coated iron oxide nanoparticles had less effect on cell adhesion/viability and morphology, and less cytotoxicity compared with uncoated, poly (acrylic acid)-coated, and MPEG-poly(acrylic acid)-coated iron oxide nanoparticles.

Synthesis and Study of Cross-Linked Chitosan-N-Poly(ethylene glycol) Nanoparticles.
Bodnar M, Hartmann JF, Borbely J.
Biomacromolecules. 2006 Nov;7(11):3030-6.
[ expand abstract ]

The present investigation describes the synthesis and characterization of novel biodegradable nanoparticles based on chitosan. Poly(ethylene glycol) dicarboxylic acid was used for intramolecular cross-linking of the chitosan linear chains. The condensation reaction of carboxylic groups and pendant amino groups of chitosan was performed by using water-soluble carbodiimide. The prepared nanosystems were stable in aqueous media. The structure of the products was determined by nuclear magnetic resonance (NMR) spectroscopy, and the particle size was identified by dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. It was found that biodegradable cross-linked chitosan nanoparticles experienced considerable swelling because of the length and flexibility of the cross-linking agent. The aqueous solutions or dispersions of nanoparticles were stable and clear or mildly opalescent systems depending on the ratio of cross-linking and molecular weight of chitosan, findings consistent with values of transmittance above 75%. Particle size measured by TEM varied in the range of 4-24 nm. In the swollen state, the average size of the individual particles measured by DLS was in the range of 50-120 nm depending on the molecular weight of chitosan and the ratio of cross-linking.

Fluorescent core-shell silica nanoparticles: towards "Lab on a Particle" architectures for nanobiotechnology.
Burns A, Ow H, Wiesner U.
Chem Soc Rev. 2006 Nov;35(11):1028-42.
[ expand abstract ]

Novel nanoscale fluorescent materials are integral to the progress of emergent fields such as nanobiotechnology and facilitate new research in a variety of contexts. Sol-gel derived silica is an excellent host material for creating fluorescent nanoparticles by the inclusion of covalently-bound organic dyes. Significant enhancements in the brightness and stability of organic dye emission can be achieved for silica-based core-shell nanoparticle architectures at length scales down to tens of nanometers with narrow size distributions. This tutorial review will highlight these findings and describe the evolution of the fluorescent core-shell silica nanoparticle concept towards integration of multiple functionalities including mesoporosity, metal nanoshells and quantitative chemical sensing. These developments point towards the development of "lab on a particle" architectures with promising prospects for nanobiotechnology, drug development and beyond.

Gold nanostructures: engineering their plasmonic properties for biomedical applications.
Hu M, Chen J, Li ZY, Au L, Hartland GV, Li X, Marquez M, Xia Y.
Chem Soc Rev. 2006 Nov;35(11):1084-94.
[ expand abstract ]

The surface plasmon resonance peaks of gold nanostructures can be tuned from the visible to the near infrared region by controlling the shape and structure (solid vs. hollow). In this tutorial review we highlight this concept by comparing four typical examples: nanospheres, nanorods, nanoshells, and nanocages. A combination of this optical tunability with the inertness of gold makes gold nanostructures well suited for various biomedical applications.

Functional DNA nanotechnology: emerging applications of DNAzymes and aptamers.
Lu Y, Liu J.
Curr Opin Biotechnol. 2006 Oct 20; [Epub ahead of print].
[ expand abstract ]

In the past 25 years, DNA molecules have been utilized both as powerful synthetic building blocks to create nanoscale architectures and as versatile programmable templates for assembly of nanomaterials. In parallel, the functions of DNA molecules have been expanded from pure genetic information storage to catalytic functions like those of protein enzymes (DNAzymes) and specific binding functions like antibodies (aptamers). In the past few years, a new interdisciplinary field has emerged that aims to combine functional DNA biology with nanotechnology to generate more dynamic and controllable DNA-based nanostructures or DNA-templated nanomaterials that are responsive to chemical stimuli.

Magnetically Assisted and Accelerated Self-Assembly of Strawberry-like Nano/Microparticles.
Huang H, Anker JN, Wang K, Kopelman R.
J Phys Chem B Condens Matter Mater Surf Interfaces Biophys. 2006 Oct 12;110(40):19929-34.
[ expand abstract ]

Precisely controlling multiple components of functional materials with well-defined shapes and dimensions on the micro/nanometer scale promises to provide new electronic, magnetic, mechanical, and optical properties for novel sensors, circuits, and other materials application. Here for the first time we introduce a novel method to reliably pattern strawberry-like microspheres by employing magnetically directed and accelerated self-assembly of nano/microparticles in aqueous solution, without the use of a template (such as molds or grooves). The results show that 100-1000 nm paramagnetic "decorating particles" rapidly self-assembled onto the surface of fluorescent 4-5 mum spherical magnetized "core particles", producing strawberry-like particles with stable and precisely arranged microstructures. Magnetic CrO(2) nanorods, approximately 60 nm in diameter and 300 nm long, attached to the nonplanar surface of the 4-5 mum polystyrene core microspheres, serve as nanometer magnetic traps, so as to attract and confine paramagnetic decorating particles. The ease and speed, with which these particles can be fabricated with the aid of magnetic force, and the flexibility to tailor their chemical and physical properties through the choice of decorating particles, should facilitate their use for practical application in materials science, biology, and technology.

Preparation of amorphous cefuroxime axetil nanoparticles by controlled nanoprecipitation method without surfactants.
Zhang JY, Shen ZG, Zhong J, Hu TT, Chen JF, Ma ZQ, Yun J.
Int J Pharm. 2006 Oct 12;323(1-2):153-60.
[ expand abstract ]

Amorphous nanoparticles of cefuroxime axetil (CFA), a poorly water-soluble drug, were produced by the controlled nanoprecipitation method without any surfactants at room temperature. The influence of the operation parameters, such as the types of solvent and anti-solvent, the stirring speed, the solvent/anti-solvent (S/AS) volume ratio, the drug concentration and the precipitation temperature, were experimentally investigated. The results indicated that increasing the stirring speed and the S/AS volume, decreasing the drug concentration and the temperature favored to decrease the particle size from 700 to 900nm to approximately 300nm. The XRD analyses confirmed that the as-prepared CFA was amorphous nanoparticles. Furthermore, the amorphous CFA nanoparticles exhibited significantly enhanced dissolution property when compared to the commercial spray-dried product. The results demonstrated that the controlled nanoprecipitation method is a direct and feasible technology which could be utilized for preparation of the poorly water-soluble pharmaceutical nanoparticles.

Tagging of avidin immobilized beads with biotinylated YAG:Ce(3+) nanocrystal phosphor.
Asakura R, Isobe T, Kurokawa K, Aizawa H, Ohkubo M.
Anal Bioanal Chem. 2006 Oct 11; [Epub ahead of print] .
[ expand abstract ]

YAG:Ce(3+) nanoparticles 9.5 +/- 1.2 nm in diameter have been synthesized from aluminium isopropoxide and acetates of yttrium and cerium in 1,4-butanediol (1,4-BD) by autoclave treatment at 300 degrees C for 2 h. After replacing 1,4-BD by ultrapure water, NH(2) groups were introduced on the surface of YAG:Ce(3+) nanoparticles by addition of 3-aminopropyltrimethoxysilane then biotinylation with sulfo-NHS-LC-biotin. We demonstrated that avidin immobilized beads are tagged by biotinylated YAG:Ce(3+) nanoparticles by the selective avidin-biotin interaction, furnishing a green fluorescent image on excitation with blue light. This result indicates that YAG:Ce(3+) nanoparticle phosphors have much potential in biological applications.

Toward Intelligent Nanosize Bioreactors: A pH-Switchable, Channel-Equipped, Functional Polymer Nanocontainer.
Broz P, Driamov S, Ziegler J, Ben-Haim N, Marsch S, Meier W, Hunziker P.
Nano Lett. 2006 Oct 11;6(10):2349-2353.
[ expand abstract ]

To develop an intelligent sensor-effector functionality on the nanoscale, a pH-switchable, controlled nanoreactor based on amphiphilic copolymer membranes was built. The nanovesicles were equipped with bacterial transmembrane ompF pore proteins and the pH-sensitive enzyme acid phosphatase, resulting in a switchable substrate processing at pH 4-6.5. Ideal pH and substrate concentrations for the reaction were determined experimentally. In future, the reactor might be used for self-regulating targeted diagnostic and therapeutic applications in medicine.

Recent developments in optical detection methods for microchip separations.
Gotz S, Karst U.
Anal Bioanal Chem. 2006 Oct 10; [Epub ahead of print] .
[ expand abstract ]

This paper summarizes the features and performances of optical detection systems currently applied in order to monitor separations on microchip devices. Fluorescence detection, which delivers very high sensitivity and selectivity, is still the most widely applied method of detection. Instruments utilizing laser-induced fluorescence (LIF) and lamp-based fluorescence along with recent applications of light-emitting diodes (LED) as excitation sources are also covered in this paper. Since chemiluminescence detection can be achieved using extremely simple devices which no longer require light sources and optical components for focusing and collimation, interesting approaches based on this technique are presented, too. Although UV/vis absorbance is a detection method that is commonly used in standard desktop electrophoresis and liquid chromatography instruments, it has not yet reached the same level of popularity for microchip applications. Current applications of UV/vis absorbance detection to microchip separations and innovative approaches that increase sensitivity are described. This article, which contains 85 references, focuses on developments and applications published within the last three years, points out exciting new approaches, and provides future perspectives on this field.

Nanostructured Thermosensitive Polymers with Radical Scavenging Ability.
Zhou G, Harruna II, Zhou WL, Aicher WK, Geckeler KE.
Chemistry. 2006 Oct 10; [Epub ahead of print].
[ expand abstract ]

The thermosensitive [60]fullerene end-capped poly(N-isopropylacrylamide) was successfully synthesized by the reaction of C(60) with dithiobenzoate-terminated poly(N-isopropylacrylamide), which was prepared by reversible addition-fragmentation chain-transfer (RAFT) polymerization in the presence of azobisisobutyronitrile (AIBN). Its structure was determined by FTIR, UV/Vis, and carbon and proton NMR spectroscopy as well as by size exclusion chromatography (SEC). The novel fullerenated polymer retained the thermosensitivity of poly(N-isopropylacrylamide). Moreover, it is soluble in water and most of the common organic solvents. Interestingly, it was able to form nanoparticle clusters in methanol and exhibited significant radical scavenging ability in cell viability and metabolic activity tests with fibroblasts and NOR-3 radicals.

Hormone-PAMAM Dendrimer Conjugates: Polymer Dynamics and Tether Structure Affect Ligand Access to Receptors.
Kim SH, Katzenellenbogen JA.
Angew Chem Int Ed Engl. 2006 Oct 6; [Epub ahead of print] .
[ expand abstract ]

No abstract available

Chemically Selective Sensing through Layer-by-Layer Incorporation of Biorecognition into Thin Film Substrates for Surface-Enhanced Resonance Raman Scattering.
Pieczonka NP, Goulet PJ, Aroca RF.
J Am Chem Soc. 2006 Oct 4;128(39):12626-7.
[ expand abstract ]

In this work, the fabrication, characterization, and application of avidin/Ag nanoparticle layer-by-layer (LbL) films as chemically selective substrates for surface-enhanced resonance Raman scattering (SERRS) is demonstrated. The biospecific interaction between avidin and the small molecule biotin, one of the strongest known to exist in nature, is exploited to preferentially capture biotinylated species from solution. This highly favored adsorption is shown to yield SERRS concentration enhancements and improved detection sensitivities of ca. 10(2) for commercially available and in situ prepared biotinylated species over their nontagged counterparts.

The proteomic reactor: a microfluidic device for processing minute amounts of protein prior to mass spectrometry analysis.
Ethier M, Hou W, Duewel HS, Figeys D.
J Proteome Res. 2006 Oct;5(10):2754-9.
[ expand abstract ]

Gel-free proteomics has emerged as a complement to conventional gel-based proteomics. Gel-free approaches focus on peptide or protein fractionation, but they do not address the efficiency of protein processing. We report the development of a microfluidic proteomic reactor that greatly simplifies the processing of complex proteomic samples by combining multiple proteomic steps. Rapid extraction and enrichment of proteins from complex proteomic samples or directly from cells are readily performed on the reactor. Furthermore, chemical and enzymatic treatments of proteins are performed in 50 nL effective volume, which results in an increased number of generated peptides. The products are compatible with mass spectrometry. We demonstrated that the proteomic reactor is at least 10 times more sensitive than current gel-free methodologies with one protein identified per 440 pg of protein lysate injected on the reactor. Furthermore, as little as 300 cells can be directly introduced on the proteomic reactor and analyzed by mass spectrometry.

Profiling the near field of a plasmonic nanoparticle with Raman-based molecular rulers.
Lal S, Grady NK, Goodrich GP, Halas NJ.
Nano Lett. 2006 Oct;6(10):2338-43.
[ expand abstract ]

The enhanced local optical fields at the surface of illuminated metallic nanoparticles and nanostructures are of intense fundamental and technological interest. Here we report a self-consistent measurement of the spatial extent of the fringing field above a plasmonic nanoparticle surface. Bifunctional DNA-based adsorbate molecules are used as nanoscale optical rulers, providing two distinct surface enhanced Raman scattering signals that vary independently in intensity as a function of distance from the nanoparticle surface. While the measurement technique is calibrated on gold nanoshell surfaces with controlled and predictable electromagnetic nanoenvironments, this approach is broadly adaptable to a wide range of plasmonic geometries.

The effect of silica nanoparticulate coatings on serum protein adsorption and cellular response.
Lord MS, Cousins BG, Doherty PJ, Whitelock JM, Simmons A, Williams RL, Milthorpe BK.
Biomaterials. 2006 Oct;27(28):4856-62.
[ expand abstract ]

Serum protein adsorption on colloidal silica surfaces was investigated using a quartz crystal microbalance with dissipation (QCM-D) monitoring. The amount of serum proteins adsorbed on colloidal silica-coated surfaces was not significantly different from the control silica surfaces, with the exception of 21nm colloidal silica which experienced significantly less (P<0.05) fibrinogen adsorption compared with control silica. The adhesion and proliferation of human endothelial cells (C11STH) on nano-scale colloidal silica surfaces were significantly reduced compared with control silica surfaces, suggesting that the conformation of adsorbed proteins on the colloidal silica surfaces plays a role in modulating the amount of cell binding. Fibronectin is one of the main extracellular matrix proteins involved in endothelial cell attachment to biomaterial surfaces. There was reduced binding of a monoclonal anti-fibronectin antibody, that reacted specifically with the cell-binding fragment, to fibronectin-coated colloidal silica surfaces compared with control silica surfaces. This suggests that the fibronectin adsorbed on the colloidal silica-coated surfaces was conformationally changed compared with control silica reducing the availability of the cell-binding domain of fibronectin.

Massively Parallel Dip-Pen Nanolithography with 55 000-Pen Two-Dimensional Arrays.
Salaita K, Wang Y, Fragala J, Vega RA, Liu C, Mirkin CA.
Angew Chem Int Ed Engl. 2006 Sep 25; [Epub ahead of print] .
[ expand abstract ]

No abstract available

Controlled release from a nanocarrier entrapped within a microcarrier.
Rojas EC, Sahiner N, Lawson LB, John VT, Papadopoulos KD.
J Colloid Interface Sci. 2006 Sep 15;301(2):617-23.
[ expand abstract ]

This study illustrates the entrapment of the dye molecule fluorescein sodium salt (FSS) by hydrogel nanoparticles, which are in turn confined inside a water-in-oil-in-water double-emulsion globule, and its subsequent release by the action of the competing agent hydrochloric acid (HCl). Thus, a "double carrier" concept is being introduced in which a nanoscale delivery vehicle is being transported by a microscale delivery vehicle in order to simultaneously take advantage of both systems. This may facilitate storage and handling while protecting the active substance and improving its action upon application.

Quantum Dot Encapsulation in Viral Capsids.
Dixit SK, Goicochea NL, Daniel MC, Murali A, Bronstein L, De M, Stein B, Rotello VM, Kao CC, Dragnea B.
Nano Lett. 2006 Sep 13;6(9):1993-1999.
[ expand abstract ]

Incorporation of CdSe/ZnS semiconductor quantum dots (QDs) into viral particles provides a new paradigm for the design of intracellular microscopic probes and vectors. Several strategies for the incorporation of QDs into viral capsids were explored; those functionalized with poly(ethylene glycol) (PEG) can be self-assembled into viral particles with minimal release of photoreaction products and enhanced stability against prolonged irradiation.

Application of a microfluidic reactor for screening cancer prodrug activation using silica-immobilized nitrobenzene nitroreductase.
Berne C, Betancor L, Luckarift HR, Spain JC.
Biomacromolecules. 2006 Sep;7(9):2631-6.
[ expand abstract ]

The nitroreductase-catalyzed conversion of a strong electron-withdrawing nitro group to the corresponding electron-donating hydroxylamine is useful in a variety of biotechnological applications. Activation of prodrugs for cancer treatments or antibiotic therapy are the most common applications. Here, we show that a bacterial nitrobenzene nitroreductase (NbzA) from Pseudomonas pseudoalcaligenes JS45 activates the dinitrobenzamide cancer prodrug CB1954 and the proantibiotic nitrofurazone. NbzA was purified by affinity chromatography and screened for substrate specificity with respect to prodrug activation. To facilitate screening of alternate potential prodrugs, polyethyleneimine-mediated silica formation was used to immobilize NbzA with high immobilization yields and high loading capacities. Greater than 80% of the NbzA was immobilized, and enzyme activity was significantly more stable than NbzA in solution. The resulting silica-encapsulated NbzA was packed into a microfluidic microreactor that proved suitable for continuous operation using nitrobenzene, CB1954, and the proantibiotic nitrofurazone. The flow-through system provides a rapid and reproducible screening method for determining the NbzA-catalyzed activation of prodrugs and proantibiotics.

Application of microfluidic chip with integrated optics for electrophoretic separations of proteins.
Vieillard J, Mazurczyk R, Morin C, Hannes B, Chevolot Y, Desbene PL, Krawczyk S.
J Chromatogr B Analyt Technol Biomed Life Sci. 2006 Sep 7; [Epub ahead of print] .
[ expand abstract ]

This paper describes the fabrication, the characterization and the applications of a capillary electrophoresis microchip. This hybrid device (glass/PDMS) features channels and optical waveguides integrated in one common substrate. It can be used for electrophoretic separation and fluorimetric detection of molecules. The microfluidic performance of the device is demonstrated by capillary zone and gel electrophoresis of proteins.

Optimization of DNA-tagged liposomes for use in microtiter plate analyses.
Edwards KA, Baeumner AJ.
Anal Bioanal Chem. 2006 Sep 5; [Epub ahead of print] .
[ expand abstract ]

Dye-encapsulating unilamellar DNA oligonucleotide-tagged liposomes were prepared and characterized for use as signal-enhancing reagents in a microtiter plate sandwich-hybridization analyses of single-stranded RNA or DNA sequences. The liposomes were synthesized using the reversed-phase evaporation method and tagged with DNA oligonucleotides by adding cholesteryl-modified DNA reporter probes to the initial lipid mixture. Liposomes were prepared using probe coverages of 0.0013-0.103 mol% of the total lipid input, several hydrophobic and poly(ethylene glycol)-based spacers between the cholesteryl anchor and the probe, and liposome diameters ranging from 200 nm to 335 nm. Their signal enhancement functionality was compared by using them in microtiter plate sandwich-hybridization assays for the detection of single-stranded DNA sequences. In these assays, an optimal reporter probe concentration of 0.103 mol%, a liposome diameter of 274 nm, and a phospholipid concentration of 0.3 mM were found. The length between the cholesteryl anchor and the probe was optimal when a spacer composed of TEG+(CH(2)O)(3) was used. Under optimal conditions, a detection limit of 0.5 nM for a truncated synthetic DNA sequence was found with a coefficient of variation of 4.4%. A 500-fold lower limit of detection using fluorescence was found using lysed dye-encapsulating liposomes versus a single fluorescein-labeled probe. Finally, when this method was applied to the detection of atxA RNA extracted from E.coli SG12036-pIu121 and amplified using NASBA, a minimum extracted concentration of RNA of 1.1x10(-7) mug/muL was found.

A nanofluidic railroad switch for DNA.
Riehn R, Austin RH, Sturm JC.
Nano Lett. 2006 Sep;6(9):1973-6.
[ expand abstract ]

We present a metamaterial consisting of a two-dimensional, asymmetric lattice of crossed nanochannels in fused silica, with channel diameters of 80 nm to 140 nm. When DNA is introduced, it is stretched and linearized. We show that the asymmetry in channel dimensions gives rise to a preferred direction for DNA orientation and a preferred direction for transport under dc electrophoresis. Interestingly, the preferred axis of orientation and transport can be switched by 90 degrees through application of an ac voltage. We explain the results in terms of an energy landscape for polyelectrolytes that consists of entropic and dielectrophoretic contributions and whose strength and sign can be tuned by changing the ac field strength.

Size and stability of liposomes: A possible role of hydration and osmotic forces.
Sabin J, Prieto G, Ruso JM, Hidalgo-Alvarez R, Sarmiento F.
Eur Phys J E Soft Matter. 2006 Aug;20(4):401-408.
[ expand abstract ]

Dynamic light scattering and electrophoretic mobility measurements have been used to characterize the size, size distribution and zeta potentials (zeta-potentials) of egg yolk phosphatidylcholine (EYPC) liposomes in the presence of monovalent ions ( Na(+) and K(+)). To study the stability of liposomes the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory has been extended by introducing the hydrated radius of the adsorbed ions onto the liposome surfaces. The decrease of liposome size is explained on the basis of the membrane impermeability to some ions which generate osmotic forces, which leads to evacuate water from liposome inside.

Actin Filament Guidance on a Chip: Toward High-Throughput Assays and Lab-on-a-Chip Applications.
Sundberg M, Bunk R, Albet-Torres N, Kvennefors A, Persson F, Montelius L, Nicholls IA, Ghatnekar-Nilsson S, Omling P, Tagerud S, Mansson A.
Langmuir. 2006 Aug 15;22(17):7286-95.
[ expand abstract ]

Biological molecular motors that are constrained so that function is effectively limited to predefined nanosized tracks may be used as molecular shuttles in nanotechnological applications. For these applications and in high-throughput functional assays (e.g., drug screening), it is important that the motors propel their cytoskeletal filaments unidirectionally along the tracks with a minimal number of escape events. We here analyze the requirements for achieving this for actin filaments that are propelled by myosin II motor fragments (heavy meromyosin; HMM). First, we tested the guidance of HMM-propelled actin filaments along chemically defined borders. Here, trimethylchlorosilane (TMCS)-derivatized areas with high-quality HMM function were surrounded by SiO(2) domains where HMM did not bind actin. Guidance along the TMCS-SiO(2) border was almost 100% for filament approach angles between 0 and 20 degrees but only about 10% at approach angles near 90 degrees . A model (Clemmens, J.; Hess, H.; Lipscomb, R.; Hanein, Y.; Bohringer, K. F.; Matzke, C. M.; Bachand, G. D.; Bunker, B. C.; Vogel, V. Langmuir 2003, 19, 10967-10974) accounted for essential aspects of the data and also correctly predicted a more efficient guidance of actin filaments than previously shown for kinesin-propelled microtubules. Despite the efficient guidance at low approach angles, nanosized (<700 nm wide) TMCS tracks surrounded by SiO(2) were not effective in guiding actin filaments. Neither was there complete guidance along nanosized tracks that were surrounded by topographical barriers (walls and roof partially covering the track) unless there was also chemically based selectivity between the tracks and surroundings. In the latter case, with dually defined tracks, there was close to 100% guidance. A combined experimental and theoretical analysis, using tracks of the latter type, suggested that a track width of less than about 200-300 nm is sufficient at a high HMM surface density to achieve unidirectional sliding of actin filaments. In accord with these results, we demonstrate the long-term trapping of actin filaments on a closed-loop track (width < 250 nm). The results are discussed in relation to lab-on-a-chip applications and nanotechnology-assisted assays of actomyosin function.

Integrated microfluidics for parallel screening of an in situ click chemistry library.
Wang J, Sui G, Mocharla VP, Lin RJ, Phelps ME, Kolb HC, Tseng HR.
Angew Chem Int Ed Engl. 2006 Aug 11;45(32):5276-81.
[ expand abstract ]

No abstract available

Integrated microfluidics for parallel screening of an in situ click chemistry library.
Wang J, Sui G, Mocharla VP, Lin RJ, Phelps ME, Kolb HC, Tseng HR.
Angew Chem Int Ed Engl. 2006 Aug 11;45(32):5276-81.
[ expand abstract ]

No abstract available

Sonochemical preparation of hydroxyapatite nanoparticles stabilized by glycosaminoglycans.
Han Y, Li S, Wang X, Bauer I, Yin M.
Ultrason Sonochem. 2006 Aug 9; [Epub ahead of print] .
[ expand abstract ]

Stable hydroxyapatite (HAP) nanoparticles system was synthesized from Ca(H(2)PO(4))(2) aqueous solution and saturated Ca(OH)(2) aqueous solution by an improved precipitation method. This method was reformed through using ultrasound irradiation as assistant technology due to its unique chemical reaction effects and adding glycosaminoglycans (GAGs) as regulation additive due to its strong interaction with HAP. The products were characterized by Malvern Zetasizer 3000HS Analysis system, TEM and ED. The size distribution and zeta potential of HAP nanoparticles were influenced by the concentration of GAGs. With the GAGs concentration of 0.35g/L, the better excellent HAP nanoparticle system could be obtained with the number-averaged particle size of 22.2nm in 84.5% area and 54.6nm in 15.5% area between 18.1nm and 117.4nm and the zeta potential of -60.9mV. In the presence of GAGs, the particle size and size distribution are little sensitive to the ultrasound irradiation (UI) time. With the increasing of UI time from 0.5h to 3h and 5h, the particle size increased a little and the crystallinity was improved. GAGs inhibited HAP crystal growth and stabilized HAP nanoparticles. Based on the TEM observation and size distribution determination of HAP nanoparticles, the possible formation mechanism of HAP nanoparticles stabilized by GAGs under UI was discussed.

Electrochemical fabrication of conducting polymer nanowires in an integrated microfluidic system.
Wang J, Bunimovich YL, Sui G, Savvas S, Wang J, Guo Y, Heath JR, Tseng HR.
Chem Commun (Camb). 2006 Aug 7;(29):3075-7.
[ expand abstract ]

In this paper, we introduce a new approach for the in situ electrochemical fabrication of an individually addressable array of conducting polymer nanowires (CPNWs) positioned within an integrated microfluidic device and also demonstrate that such an integrated device can be used as a chemical sensor immediately after its construction.

Continuous separation of particles using a microfluidic device equipped with flow rate control valves.
Sai Y, Yamada M, Yasuda M, Seki M.
J Chromatogr A. 2006 Aug 4; [Epub ahead of print] .
[ expand abstract ]

We propose herein an improved microfluidic system for continuous and precise particle separation. We have previously proposed a method for particle separation called "pinched flow fractionation." Using the previously reported method, particles can be continuously separated according to differences in their diameters, simply by introducing liquid flows with and without particles into a specific microchannel structure. In this study, we incorporated PDMS membrane microvalves for flow rate control into the microfluidic device to improve the separation accuracy. By adjusting the flow rates distributed to each outlet, target particles could be precisely collected from the desired outlet. We succeeded in separating micron and submicron-size polymer particles. This method can be used widely for continuous and precise separation of various kinds of particles, and can function as an important part of microfluidic systems.

Microfluidic vias enable nested bioarrays and autoregulatory devices in Newtonian fluids.
Kartalov EP, Walker C, Taylor CR, Anderson WF, Scherer A.
Proc Natl Acad Sci U S A. 2006 Aug 3; [Epub ahead of print] .
[ expand abstract ]

We report on a fundamental technological advance for multilayer polydimethylsiloxane (PDMS) microfluidics. Vertical passages (vias), connecting channels located in different layers, are fabricated monolithically, in parallel, by simple and easy means. The resulting 3D connectivity greatly expands the potential complexity of microfluidic architecture. We apply the vias to printing nested bioarrays and building autoregulatory devices. A current source is demonstrated, while a diode and a rectifier are derived; all are building blocks for analog circuitry in Newtonian fluids. We also describe microfluidic septa and their applications. Vias lay the foundation for a new generation of microfluidic devices.

Solution-phase surface modification in intact poly(dimethylsiloxane) microfluidic channels.
Sui G, Wang J, Lee CC, Lu W, Lee SP, Leyton JV, Wu AM, Tseng HR.
Anal Chem. 2006 Aug 1;78(15):5543-51.
[ expand abstract ]

An improved approach composed of an oxidation reaction in acidic H2O2 solution and a sequential silanization reaction using neat silane reagents for surface modification of poly(dimethylsiloxane) (PDMS) substrates was developed. This solution-phase approach is simple and convenient for some routine analytical applications in chemistry and biology laboratories and is designed for intact PDMS-based microfluidic devices, with no device postassembly required. Using this improved approach, two different functional groups, poly(ethylene glycol) (PEG) and amine (NH2), were introduced onto PDMS surfaces for passivation of nonspecific protein absorption and attachment of biomolecules, respectively. X-ray electron spectroscopy and temporal contact angle experiments were employed to monitor functional group transformation and dynamic characteristics of the PEG-grafted PDMS substrates; fluorescent protein solutions were introduced into the PEG-grafted PDMS microchannels to test their protein repelling characteristics. These analytical data indicate that the PEG-grafted PDMS surfaces exhibit improved short-term surface dynamics and robust long-term stability. The amino-grafted PDMS microchannels are also relatively stable and can be further activated for modifications with peptide, DNA, and protein on the surfaces of microfluidic channels. The resulting biomolecule-grafted PDMS microchannels can be utilized for cell immobilization and incubation, semiquantitative DNA hybridization, and immunoassay.

Quantum Dot-Based Fluorescence Resonance Energy Transfer with Improved FRET Efficiency in Capillary Flows.
Zhang CY, Johnson LW.
Anal Chem. 2006 Aug 1;78(15):5532-7.
[ expand abstract ]

Fluorescence resonance energy transfer (FRET)-based nanosensors with quantum dots (QDs) as donors and organic dyes as acceptors have long been of interest for the detection of biomolecules such as nucleic acids, but their low FRET efficiency in bulk solution has prevented the sensitive detection of nucleic acids due to the large size of the QDs and the long length of nucleic acids. Here we describe a novel approach to improve the detection sensitivity of QD-based nanosensors using single-molecule detection in a capillary flow. In comparison with bulk measurement, single-molecule detection in a capillary flow possesses the unique advantages of improved FRET efficiency, high sensitivity, prevention of photobleaching, and low sample consumption. Greater FRET efficiency was obtained due to the deformation of DNA in the capillary stream. This technique can be easily extended to sensitive bimolecular analysis in microfluidic chips, and it may also offer a promising approach to study the deformation of small nucleic acids in fluid flow.

All-Optical Nanoscale pH Meter.
Bishnoi SW, Rozell CJ, Levin CS, Gheith MK, Johnson BR, Johnson DH, Halas NJ.
Nano Lett. 2006 Aug;6(8):1687-92.
[ expand abstract ]

We show that an Au nanoshell with a pH-sensitive molecular adsorbate functions as a standalone, all-optical nanoscale pH meter that monitors its local environment through the pH-dependent surface-enhanced Raman scattering (SERS) spectra of the adsorbate molecules. Moreover, we also show how the performance of such a functional nanodevice can be assessed quantitatively. The complex spectral output is reduced to a simple device characteristic by application of a locally linear manifold approximation algorithm. The average accuracy of the nano-"meter" was found to be +/-0.10 pH units across its operating range.

Compact fluorescence detection using in-fiber microchannels-its potential for lab-on-a-chip applications.
Irawan R, Tay CM, Tjin SC, Fu CY.
Lab Chip. 2006 Aug;6(8):1095-8.
[ expand abstract ]

This paper reports a compact and practical fluorescence sensor using an in-fiber microchannel. A blue LED, a multimode PMMA or silica fiber and a mini-PMT were used as an excitation source, a light guide and a fluorescence detector, respectively. Microfluidic channels of 100 microm width and 210microm depth were fabricated in the optical fibers using a direct-write CO(2) laser system. The experimental results show that the sensor has high sensitivity, able to detect 0.005 microg L(-1) of fluorescein in the PBS solution, and the results are reproducible. The results also show that the silica fiber sensor has better sensitivity than that of the PMMA fiber sensor. This could be due to the fouling effect of the frosty layer formed at the microchannel made within the PMMA fiber. It is believed that this fiber sensor has the potential to be integrated into microfluidic chips for lab-on-a-chip applications.

On-chip syringe pumps for picoliter-scale liquid manipulation.
Yokokawa R, Saika T, Nakayama T, Fujita H, Konishi S.
Lab Chip. 2006 Aug;6(8):1062-6.
[ expand abstract ]

On-chip microsyringes are developed by integrating parallel micro actuators and a microfluidic chip. Sliders of an Electrostatically Controlled Linear Inchworm Actuator (ECLIA) are applied to manipulate microsyringes in the nanometer range, which allows liquid control on the picoliter scale. ECLIA drives sliders in parallel with high accuracy and a large stroke. The requirements for syringe performance, such as parallel and precise liquid control, can be satisfied by the above features of ECLIA. A total volume of a few microL is manipulated at a flow rate of 19-27 pL s(-1) by the stepwise motion of ECLIA sliders in a fluidic channel. Microsyringes integrated into the driving mechanism are a key component of Micro Total Analysis Systems (microTAS) due to the possibility of on-chip integration. In addition, the proposed approach has a significant implication in MEMS in that the electrostatic micro actuator performs a physical task that affects the outside structure.

Enzyme-targeted fluorescent imaging probes on a multiple antigenic peptide core.
Galande AK, Hilderbrand SA, Weissleder R, Tung CH.
J Med Chem. 2006 Jul 27;49(15):4715-20.
[ expand abstract ]

Peptide dendrimers have a variety of applications in biology such as the vehicles for drug and gene delivery, molecular inhibitors, protein mimics, and synthetic vaccines. The multiple antigenic peptide (MAP) system is a well-known example of a discrete, dendrimeric scaffold. We explored a novel application of the MAP-based scaffold by designing molecular probes that fluoresce only after enzymatic treatment. The probes, which were synthesized on solid support, incorporate a cathepsin S dipeptide substrate (Leu-Arg), and a poly(ethylene glycol) (PEG) chain in their dendritic arms. The fluorescence emission of the near-infrared fluorochromes attached to the N-termini of the dendritic arms was quenched. Mechanistic studies revealed formation of H-type dye aggregates within the tetravalent MAP system. By varying the length of the PEG chain, three probes were synthesized, CyPEG-1, CyPEG-2, and CyPEG-3 with 4, 8, and 12 ethylene oxide units, respectively. CyPEG-2 showed optimum aqueous solubility and quenching efficiency for imaging applications. Upon proteolytic activation with cathepsin S (EC 3.4.22.27), CyPEG-2 showed greater than 70-fold increase and more than 95% recovery in fluorescence emission.

Microfluidic diagnostic technologies for global public health.
Yager P, Edwards T, Fu E, Helton K, Nelson K, Tam MR, Weigl BH.
Nature. 2006 Jul 27;442(7101):412-8.
[ expand abstract ]

The developing world does not have access to many of the best medical diagnostic technologies; they were designed for air-conditioned laboratories, refrigerated storage of chemicals, a constant supply of calibrators and reagents, stable electrical power, highly trained personnel and rapid transportation of samples. Microfluidic systems allow miniaturization and integration of complex functions, which could move sophisticated diagnostic tools out of the developed-world laboratory. These systems must be inexpensive, but also accurate, reliable, rugged and well suited to the medical and social contexts of the developing world.

Asymmetric functionalization of gold nanoparticles with oligonucleotides.
Xu X, Rosi NL, Wang Y, Huo F, Mirkin CA.
J Am Chem Soc. 2006 Jul 26;128(29):9286-7.
[ expand abstract ]

No abstract available

Ion Exchange as a Way of Controlling the Chemical Compositions of Nano- and Microparticles Made from Infinite Coordination Polymers.
Oh M, Mirkin CA.
Angew Chem Int Ed Engl. 2006 Jul 21; [Epub ahead of print] .
[ expand abstract ]

No abstract available

Ultrasensitive solution-cast quantum dot photodetectors.
Konstantatos G, Howard I, Fischer A, Hoogland S, Clifford J, Klem E, Levina L, Sargent EH.
Nature. 2006 Jul 13;442(7099):180-3. EH.
[ expand abstract ]

Solution-processed electronic and optoelectronic devices offer low cost, large device area, physical flexibility and convenient materials integration compared to conventional epitaxially grown, lattice-matched, crystalline semiconductor devices. Although the electronic or optoelectronic performance of these solution-processed devices is typically inferior to that of those fabricated by conventional routes, this can be tolerated for some applications in view of the other benefits. Here we report the fabrication of solution-processed infrared photodetectors that are superior in their normalized detectivity (D*, the figure of merit for detector sensitivity) to the best epitaxially grown devices operating at room temperature. We produced the devices in a single solution-processing step, overcoating a prefabricated planar electrode array with an unpatterned layer of PbS colloidal quantum dot nanocrystals. The devices showed large photoconductive gains with responsivities greater than 10(3) A W(-1). The best devices exhibited a normalized detectivity D* of 1.8 x 10(13) jones (1 jones = 1 cm Hz(1/2) W(-1)) at 1.3 microm at room temperature: today's highest performance infrared photodetectors are photovoltaic devices made from epitaxially grown InGaAs that exhibit peak D* in the 10(12) jones range at room temperature, whereas the previous record for D* from a photoconductive detector lies at 10(11) jones. The tailored selection of absorption onset energy through the quantum size effect, combined with deliberate engineering of the sequence of nanoparticle fusing and surface trap functionalization, underlie the superior performance achieved in this readily fabricated family of devices.

DNA-Induced Size-Selective Separation of Mixtures of Gold Nanoparticles.
Lee JS, Stoeva SI, Mirkin CA.
J Am Chem Soc. 2006 Jul 12;128(27):8899-903.
[ expand abstract ]

We present a novel method for size-selectively separating mixtures of nanoparticles in aqueous media utilizing the inherent chemical recognition properties of DNA and the cooperative binding properties of DNA-functionalized gold nanoparticles. We have determined that the melting temperatures (T(m)s) of aggregates formed from nanoparticles interconnected by duplex DNA are dependent upon particle size. This effect is proposed to derive from larger contact areas between the larger particles and therefore increased cooperativity, leading to higher T(m)s. The separation protocol involves taking two aliquots of a mixture of particles that vary in size and functionalizing them with complementary DNA. These aliquots are mixed at a temperature above the T(m) for aggregates formed from the smaller particles but below the T(m) for aggregates formed from the larger particles. Therefore, the aggregates that form consist almost exclusively of the larger particles and can be easily separated by sedimentation and centrifugation from the smaller dispersed particles. This unusual size-dependent behavior and separation protocol are demonstrated for three binary mixtures of particles and one ternary mixture.

Self-Assembling Molecular Dumbbells: From Nanohelices to Nanocapsules Triggered by Guest Intercalation.
Ryu JH, Kim HJ, Huang Z, Lee E, Lee M.
Angew Chem Int Ed Engl. 2006 Jul 12; [Epub ahead of print].
[ expand abstract ]

No abstract available

Two-Dimensional Nanoparticle Arrays Show the Organizational Power of Robust DNA Motifs.
Zheng J, Constantinou PE, Micheel C, Alivisatos AP, Kiehl RA, Seeman NC.
Nano Lett. 2006 Jul 12;6(7):1502-1504.
[ expand abstract ]

The bottom-up spatial organization of potential nanoelectronic components is a key intermediate step in the development of molecular electronics. We describe robust three-space-spanning DNA motifs that are used to organize nanoparticles in two dimensions. One strand of the motif ends in a gold nanoparticle; only one DNA strand is attached to the particle. By using two of the directions of the motif to produce a two-dimensional crystalline array, one direction is free to bind gold nanoparticles. Identical motifs, tailed in different sticky ends, enable the two-dimensional periodic ordering of 5 and 10 nm diameter gold nanoparticles.

Sequence-Specific Detection of Femtomolar DNA via a Chronocoulometric DNA Sensor (CDS): Effects of Nanoparticle-Mediated Amplification and Nanoscale Control of DNA Assembly at Electrodes.
Zhang J, Song S, Zhang L, Wang L, Wu H, Pan D, Fan C.
J Am Chem Soc. 2006 Jul 5;128(26):8575-80.
[ expand abstract ]

We herein report a novel nanoparticle-based electrochemical DNA detection approach. This DNA sensor is based on a "sandwich" detection strategy, which involves capture probe DNA immobilized on gold electrodes and reporter probe DNA labeled with gold nanoparticles that flank the target DNA sequence. Electrochemical signals are generated by chronocoulometric interrogation of [Ru(NH(3))(6)](3+) that quantitatively binds to surface-confined capture probe DNA via electrostatic interactions. We demonstrated that the incorporation of a gold nanoparticle in this sensor design significantly enhanced the sensitivity and the selectivity. Nanoscale control of the self-assembly process of DNA probes at gold electrodes further increased the sensor performance. As a result of these two combined effects, this DNA sensor could detect as low as femtomolar (zeptomoles) DNA targets and exhibited excellent selectivity against even a single-base mismatch. In addition, this novel DNA sensor showed fairly good reproducibility, stability, and reusability.

Designed DNA molecules: principles and applications of molecular nanotechnology.
Condon A.
Nat Rev Genet. 2006 Jul;7(7):565-75; Epub 2006 Jun 13.
[ expand abstract ]

Long admired for its informational role in the cell, DNA is now emerging as an ideal molecule for molecular nanotechnology. Biologists and biochemists have discovered DNA sequences and structures with new functional properties, which are able to prevent the expression of harmful genes or detect macromolecules at low concentrations. Physical and computational scientists can design rigid DNA structures that serve as scaffolds for the organization of matter at the molecular scale, and can build simple DNA-computing devices, diagnostic machines and DNA motors. The integration of biological and engineering advances offers great potential for therapeutic and diagnostic applications, and for nanoscale electronic engineering.

Structural basis for near unity quantum yield core/shell nanostructures.
McBride J, Treadway J, Feldman LC, Pennycook SJ, Rosenthal SJ.
Nano Lett. 2006 Jul;6(7):1496-501.
[ expand abstract ]

Aberration-corrected Z-contrast scanning transmission electron microscopy of core/shell nanocrystals shows clear correlations between structure and quantum efficiency. Uniform shell coverage is obtained only for a graded CdS/ZnS shell material and is found to be critical to achieving near 100% quantum yield. The sublattice sensitivity of the images confirms that preferential growth takes place on the anion-terminated surfaces. This explains the three-dimensional "nanobullet" shape observed in the case of core/shell nanorods.

Carbon nanotubes as electrodes for dielectrophoresis of DNA.
Tuukkanen S, Toppari JJ, Kuzyk A, Hirviniemi L, Hytonen VP, Ihalainen T, Torma P.
Nano Lett. 2006 Jul;6(7):1339-43.
[ expand abstract ]

Dielectrophoresis can potentially be used as an efficient trapping tool in the fabrication of molecular devices. For nanoscale objects, however, the Brownian motion poses a challenge. We show that the use of carbon nanotube electrodes makes it possible to apply relatively low trapping voltages and still achieve high enough field gradients for trapping nanoscale objects, e.g., single molecules. We compare the efficiency and other characteristics of dielectrophoresis between carbon nanotube electrodes and lithographically fabricated metallic electrodes, in the case of trapping nanoscale DNA molecules. The results are analyzed using finite element method simulations and reveal information about the frequency-dependent polarizability of DNA.

A microfluidic device for continuous, real time blood plasma separation.
Yang S, Undar A, Zahn JD.
Lab Chip. 2006 Jul;6(7):871-80; Epub 2006 Apr 19.
[ expand abstract ]

A microfluidic device for continuous, real time blood plasma separation is introduced. The principle of the blood plasma separation from blood cells is supported by the Zweifach-Fung effect and was experimentally demonstrated using simple microchannels. The blood plasma separation device is composed of a blood inlet, a bifurcating region which leads to a purified plasma outlet, and a concentrated blood cell outlet. It was designed to separate blood plasma from an initial blood sample of up to 45% inlet hematocrit (volume percentage of cells). The microfluidic network was designed using an analogous electrical circuit, as well as analytical and numerical studies. The functionality of this device was demonstrated using defibrinated sheep blood. During 30 minutes of continuous blood infusion through the device, all the erythrocytes (red blood cells) traveled through the device toward the concentrated blood outlet while only the plasma was separated at the bifurcating regions and flowed towards the plasma outlet. The device has been operated continuously without any clogging or hemolysis of cells. The experimentally determined plasma selectivity with respect to blood hematocrit level was almost 100% regardless of the inlet hematocrit. The total plasma separation volume percent varied from 15% to 25% with increasing inlet hematocrit. Due to the device's simple structure and control mechanism, this microdevice is expected to be used for highly efficient continuous, real time cell-free blood plasma separation from blood samples for use in lab on a chip applications.

Peptide-Capped Gold Nanoparticles: Towards Artificial Proteins.
Levy R.
Chembiochem. 2006 Jun 29; [Epub ahead of print].
[ expand abstract ]

Peptides can be designed to form self-assembled monolayers on gold nanoparticles to give nanomaterials with some chemical properties analogous to those of proteins. A variety of molecular-recognition properties are readily integrated within the peptide monolayer. Monofunctionalized nanoparticles are obtained by using separation methods that have been optimized for proteins. Recent applications as artificial enzymes and artificial enzyme substrates are presented. The limitations and long-term potential of peptide-capped nanoparticles as artificial proteins are discussed.

HaloTag Protein-Mediated Site-Specific Conjugation of Bioluminescent Proteins to Quantum Dots.
Zhang Y, So MK, Loening AM, Yao H, Gambhir SS, Rao J.
Angew Chem Int Ed Engl. 2006 Jun 29; [Epub ahead of print].
[ expand abstract ]

No abstract available

DNA counterion current and saturation examined by a MEMS-based solid state nanopore sensor.
Chang H, Venkatesan BM, Iqbal SM, Andreadakis G, Kosari F, Vasmatzis G, Peroulis D, Bashir R.
Biomed Microdevices. 2006 Jun 23; [Epub ahead of print].
[ expand abstract ]

Reports of DNA translocation measurements have been increasing rapidly in recent years due to advancements in pore fabrication and these measurements continue to provide insight into the physics of DNA translocations through MEMS based solid state nanopores. Specifically, it has recently been demonstrated that in addition to typically observed current blockages, enhancements in current can also be measured under certain conditions. Here, we further demonstrate the power of these nanopores for examining single DNA molecules by measuring these ionic currents as a function of the applied electric field and show that the direction of the resulting current pulse can provide fundamental insight into the physics of condensed counterions and the dipole saturation in single DNA molecules. Expanding on earlier work by Manning and others, we propose a model of DNA counterion ionic current and saturation of this current based on our experimental results. The work can have broad impact in understanding DNA sensing, DNA delivery into cells, DNA conductivity, and molecular electronics.

Increasing protein stability through control of the nanoscale environment.
Asuri P, Karajanagi SS, Yang H, Yim TJ, Kane RS, Dordick JS.
Langmuir. 2006 Jun 20;22(13):5833-6.
[ expand abstract ]

We have discovered a novel property of single-walled carbon nanotubes (SWNTs)-their ability to stabilize proteins at elevated temperatures and in organic solvents to a greater extent than conventional flat supports. Experimental results and theoretical analysis reveal that the stabilization results from the curvature of SWNTs, which suppresses unfavorable protein-protein lateral interactions. Our results also indicate that the phenomenon is not unique to SWNTs but could be extended to other nanomaterials. The protein-nanotube conjugates represent a new generation of active and stable catalytic materials with potential use in biosensors, diagnostics, and bioactive films and other hybrid materials that integrate biotic and abiotic components.

Synthesis and spectroscopic observation of dendrimer-encapsulated gold nanoclusters.
Tran ML, Zvyagin AV, Plakhotnik T.
Chem Commun (Camb). 2006 Jun 14;(22):2400-1; Epub 2006 May 3.
[ expand abstract ]

We report on the observation of the excitation/emission spectrum of a dendrimer-encapsulated gold nanocluster; the synthesis of Au-PAMAM was based on reduction of HAuCl(4).3H(2)O co-dissolved in methanol together with fourth-generation OH-terminated PAMAM.

Designed DNA molecules: principles and applications of molecular nanotechnology.
Condon A.
Nat Rev Genet. 2006 Jun 13; [Epub ahead of print] .
[ expand abstract ]

Long admired for its informational role in the cell, DNA is now emerging as an ideal molecule for molecular nanotechnology. Biologists and biochemists have discovered DNA sequences and structures with new functional properties, which are able to prevent the expression of harmful genes or detect macromolecules at low concentrations. Physical and computational scientists can design rigid DNA structures that serve as scaffolds for the organization of matter at the molecular scale, and can build simple DNA-computing devices, diagnostic machines and DNA motors. The integration of biological and engineering advances offers great potential for therapeutic and diagnostic applications, and for nanoscale electronic engineering.

Biohybrid nanosystems with polymer nanofibers and nanotubes.
Greiner A, Wendorff JH, Yarin AL, Zussman E.
Appl Microbiol Biotechnol. 2006 Jun 10; [Epub ahead of print] .
[ expand abstract ]

Advanced techniques for the preparation of nanofibers, core shell fibers, hollow fibers, and rods and tubes from natural and synthetic polymers with diameters down to a few nanometers have recently been established. These techniques, among them electro- and co-electrospinning and specific template methods, allow the incorporation not only of semiconductor or catalytic nanoparticles or chromophores but also enzymes, proteins, microorganism, etc., directly during the preparation process into these nanostructures in a very gentle way. One particular advantage is that biological objects such as, for instance, proteins can be immobilized in a fluid environment within these polymer-based nano-objects in such a way that they keep their native conformation and the corresponding functions. The range of applications of such biohybrid nanosystems is extremely broad, for instance, in the areas of biosensorics, catalysis, drug delivery, or optoelectronics.

Arraying of intact liposomes into chemically functionalized microwells.
Kalyankar ND, Sharma MK, Vaidya SV, Calhoun D, Maldarelli C, Couzis A, Gilchrist L.
Langmuir. 2006 Jun 6;22(12):5403-11.
[ expand abstract ]

Here, we describe a protocol to bind individual, intact phospholipid bilayer liposomes, which are on the order of 1 mum in diameter, in microwells etched in a regular array on a silicon oxide substrate. The diameter of the wells is on the order of the liposome diameter, so only one liposome is located in each well. The background of the silicon oxide surface is functionalized with a PEG oligomer using the contact printing of a PEG silane to present a surface that resists the adsorption of proteins, lipid material, and liposomes. The interiors of the wells are functionalized with an aminosilane to facilitate the conjugation of biotin, which is then bound to Neutravidin. The avidin-coated well interiors bind the liposomes whose surfaces contain biotinylated lipids. The specific binding of the liposomes to the surface using the biotin-avidin linkage, together with the resistant nature of the background and the physical confinement of the wells, allows the liposomes to remain intact and to not unravel, rupture, and fuse onto the surface. We demonstrate this intact arraying using confocal laser scanning microscopy of fluorophores specifically tagging the microwells, the lipid bilayer, and the aqueous interior of the liposome.

Purification and preconcentration of genomic DNA from whole cell lysates using photoactivated polycarbonate (PPC) microfluidic chips.
Witek MA, Llopis SD, Wheatley A, McCarley RL, Soper SA.
Nucleic Acids Res. 2006 Jun 6;34(10):e74.
[ expand abstract ]

We discuss the use of a photoactivated polycarbonate (PPC) microfluidic chip for the solid-phase, reversible immobilization (SPRI) and purification of genomic DNA (gDNA) from whole cell lysates. The surface of polycarbonate was activated by UV radiation resulting in a photo-oxidation reaction, which produced a channel surface containing carboxylate groups. The gDNA was selectively captured on this photoactivated surface in an immobilization buffer, which consisted of 3% polyethylene glycol, 0.4 M NaCl and 70% ethanol. The methodology reported herein is similar to conventional SPRI in that surface-confined carboxylate groups are used for the selective immobilization of DNA; however, no magnetic beads or a magnetic field are required. As observed by UV spectroscopy, a load of approximately 7.6 +/- 1.6 microg/ml of gDNA was immobilized onto the PPC bed. The recovery of DNA following purification was estimated to be 85 +/- 5%. The immobilization and purification assay using this PPC microchip could be performed within approximately 25 min as follows: (i) DNA immobilization approximately 6 min, (ii) chip washout with ethanol 10 min, and (iii) drying and gDNA desorption approximately 6 min. The PPC microchip could also be used for subsequent assays with no substantial loss in recovery, no observable carryover and no need for 'reactivation' of the PC surface with UV light.

Association temperature governs structure and apparent thermodynamics of DNA-gold nanoparticles.
Beermann B, Carrillo-Nava E, Scheffer A, Buscher W, Jawalekar A, Seela F, Hinz HJ.
Biophys Chem. 2006 Jun 4; [Epub ahead of print] .
[ expand abstract ]

Apparent thermodynamics of association of DNA-modified gold nanoparticles has been characterized by UV spectroscopy and dynamic light scattering (DLS). Extinction coefficients of unlabelled and DNA-labelled gold nanoparticles have been determined to permit quantitative analysis of the absorption measurements. In contrast to previous studies the associating gold nanoparticles were furnished with complementary oligonucleotide DNA single strands. This resulted in direct complex formation between the nanoparticles on mixing without the requirement of a DNA linker sequence for initiation of cluster formation. Melting curves of the nanoparticle assemblies formed at different temperatures were subjected to two-state analysis. A comparison of the apparent thermodynamic parameters obtained for the dissociation of these aggregates suggests that both thermodynamically and structurally different nanoparticle clusters are obtained depending on the temperature at which assembly proceeds. The van't Hoff enthalpies permit an estimate of the DNA duplexes: gold nanoparticle ratio involved in network formation.

Trends in imprint lithography for biological applications.
Truskett VN, Watts MP.
Trends Biotechnol. 2006 Jun 4; [Epub ahead of print] .
[ expand abstract ]

Imprint lithography is emerging as an alternative nano-patterning technology to traditional photolithography that permits the fabrication of 2D and 3D structures with <100nm resolution, patterning and modification of functional materials other than photoresist and is low cost, with operational ease for use in developing bio-devices. Techniques for imprint lithography, categorized as either 'molding and embossing' or 'transfer printing', will be discussed in the context of microarrays for genomics, proteomics and tissue engineering. Specifically, fabrication by nanoimprint lithography (NIL), UV-NIL, step and flash imprint lithography (S-FIL), micromolding by elastomeric stamps and micro- and nano-contact printing will be reviewed.

The effect of silica nanoparticulate coatings on serum protein adsorption and cellular response.
Lord MS, Cousins BG, Doherty PJ, Whitelock JM, Simmons A, Williams RL, Milthorpe BK.
Biomaterials. 2006 Jun 3; [Epub ahead of print] .
[ expand abstract ]

Serum protein adsorption on colloidal silica surfaces was investigated using a quartz crystal microbalance with dissipation (QCM-D) monitoring. The amount of serum proteins adsorbed on colloidal silica-coated surfaces was not significantly different from the control silica surfaces, with the exception of 21nm colloidal silica which experienced significantly less (P<0.05) fibrinogen adsorption compared with control silica. The adhesion and proliferation of human endothelial cells (C11STH) on nano-scale colloidal silica surfaces were significantly reduced compared with control silica surfaces, suggesting that the conformation of adsorbed proteins on the colloidal silica surfaces plays a role in modulating the amount of cell binding. Fibronectin is one of the main extracellular matrix proteins involved in endothelial cell attachment to biomaterial surfaces. There was reduced binding of a monoclonal anti-fibronectin antibody, that reacted specifically with the cell-binding fragment, to fibronectin-coated colloidal silica surfaces compared with control silica surfaces. This suggests that the fibronectin adsorbed on the colloidal silica-coated surfaces was conformationally changed compared with control silica reducing the availability of the cell-binding domain of fibronectin.

Biomolecule-nanoparticle hybrid systems for bioelectronic applications.
Willner I, Willner B, Katz E.
Bioelectrochemistry. 2006 Jun 2; [Epub ahead of print] .
[ expand abstract ]

Recent advances in nanobiotechnology involve the use of biomolecule-nanoparticle (NP) hybrid systems for bioelectronic applications. This is exemplified by the electrical contacting of redox enzymes by means of Au-NPs. The enzymes, glucose oxidase, GOx, and glucose dehydrogenase, GDH, are electrically contacted with the electrodes by the reconstitution of the corresponding apo-proteins on flavin adenine dinucleotide (FAD) or pyrroloquinoline quinone (PQQ)-functionalized Au-NPs (1.4 nm) associated with electrodes, respectively. Similarly, Au-NPs integrated into polyaniline in a micro-rod configuration associated with electrodes provides a high surface area matrix with superior charge transport properties for the effective electrical contacting of GOx with the electrode. A different application of biomolecule-Au-NP hybrids for bioelectronics involves the use of Au-NPs as carriers for a nucleic acid that is composed of hemin/G-quadruplex DNAzyme units and a detecting segment complementary to the analyte DNA. The functionalized Au-NPs are employed for the amplified DNA detection, and for the analysis of telomerase activity in cancer cells, using chemiluminescence as a readout signal. Biomolecule-semiconductor NP hybrid systems are used for the development of photoelectrochemical sensors and optoelectronic systems. A hybrid system consisting of acetylcholine esterase (AChE)/CdS-NPs is immobilized in a monolayer configuration on an electrode. The photocurrent generated by the system in the presence of thioacetylcholine as substrate provides a means to probe the AChE activity. The blocking of the photocurrent by 1,5-bis(4-allyldimethyl ammonium phenyl)pentane-3-one dibromide as nerve gas analog enables the photoelectrochemical analysis of AChE inhibitors. Also, the association CdS-NP/double-stranded DNA hybrid systems with a Au-electrode, and the intercalation of methylene blue into the double-stranded DNA, generates an organized nanostructure of switchable photoelectrochemical functions. Electrochemical reduction of the intercalator to the leuco form, -0.4 V vs. SCE, results in a cathodic photocurrent as a result of the transfer of photoexcited conduction-band electrons to O(2) and the transport of electrons to the valance-band holes by the reduced intercalator units. The oxidation of the intercalator, E 0 V (vs. SCE), yields in the presence of triethanolamine, TEOA, as sacrificial electron donor, an anodic photocurrent by the transport of conduction-band electrons, through intercalator units, to the electrodes, and filling the valance-band holes with electrons supplied by TEOA. The systems reveal potential-switchable directions of the photocurrents, and reveal logic gate functions.

One-Pot Synthesis and Bioapplication of Amine-Functionalized Magnetite Nanoparticles and Hollow Nanospheres.
Wang L, Bao J, Wang L, Zhang F, Li Y.
Chemistry. 2006 Jun 1; [Epub ahead of print] .
[ expand abstract ]

To demonstrate their applications in biological and medical fields such as in immunoassays, magnetic separation of cells or proteins, drug or gene delivery, and magnetic resonance imaging, the template-free syntheses of water-soluble and surface functionalized magnetic nanomaterials have become essential and are challenging. Herein, we developed a facile one-pot template-free method for the preparation of amine-functionalized magnetite nanoparticles and hollow nanospheres by using FeCl(3)6 H(2)O as single iron source. These magnetic nanomaterials were characterized by TEM, SEM, XRD, and FTIR technologies. Their magnetic properties were also studied by using a superconducting quantum interference device (SQUID) magnetometer at room temperature. Then the amine-functionalized magnetite nanoparticles were applied to immunoassays and magnetic resonance imaging in live mice.

Microfluidics assisted synthesis of well-defined spherical polymeric microcapsules and their utilization as potential encapsulants.
Abraham S, Jeong EH, Arakawa T, Shoji S, Kim KC, Kim I, Go JS.
Lab Chip. 2006 Jun;6(6):752-6; Epub 2006 Apr 10.
[ expand abstract ]

In this article, the development of a novel technique to fabricate spherical polymeric microcapsules by utilizing microfluidic technology is presented. Atom transfer radical polymerization (ATRP) was employed to synthesize well-defined amphiphilic block copolymers. An organic polymer solution was constrained to adopt the spherical droplets in a continuous water phase at a T-junction microchannel, and the generation of the droplets was studied quantitatively. The flow conditions of two immiscible solutions were adjusted for the successful generation of the polymer droplets. The morphology of the microcapsules was examined. The efficiency of these polymer microcapsules as containers for the storage and controlled release of loaded molecules was evaluated by encapsulating the microcapsules with Congo-red dye and investigating the release performance using temperature controlled UV-VIS spectroscopy.

Deposition of PEG onto PMMA microchannel surface to minimize nonspecific adsorption.
Bi H, Meng S, Li Y, Guo K, Chen Y, Kong J, Yang P, Zhong W, Liu B.
Lab Chip. 2006 Jun;6(6):769-75; Epub 2006 Mar 31.
[ expand abstract ]

A protein-resistant surface has been constructed on the poly(methyl methacrylate) (PMMA) microfluidic chips based on a one-step modification. The copolymer of butyl methacrylate (BMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) is synthesized to introduce a dense PEG molecular brush-like coating on the PMMA microchannel surfaces via the anchoring effect of the hydrophobic BMA units. The PEGMA segments could produce hydrophilic domains formed on the interface so as to achieve stable electroosmotic flow, and less nonspecific adsorption toward biomolecules. The modification procedure and the properties of the poly(BMA-co-PEGMA)-coated surface have been characterized by FT-IR spectroscopy, confocal fluorescence microscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. The water contact angle and electroosmotic flow of PEG-modified PMMA microchip are measured to be 36 degrees and 5.4 x 10(-4) cm(2) V(-1) s(-1), while those of 73 degrees and 1.9 x 10(-4) cm(2) V(-1) s(-1) for native one, respectively. The PEG-modified microchip has been applied for the electrophoresis separation of proteins, corresponding to the theoretical efficiencies about 16 300 and 412 300 plates m(-1). In the interest of achieving efficient separation while minimizing biofoulings from the serum and plasma, the fabrication of PEG-coated microfluidic chips would provide a biocompatible platform for complex biological analysis.

A microfluidic multi-injector for gradient generation.
Chung BG, Lin F, Jeon NL.
Lab Chip. 2006 Jun;6(6):764-8; Epub 2006 Apr 6.
[ expand abstract ]

This paper describes a microfluidic multi-injector (MMI) that can generate temporal and spatial concentration gradients of soluble molecules. Compared to conventional glass micropipette-based methods that generate a single gradient, the MMI exploits microfluidic integration and actuation of multiple pulsatile injectors to generate arbitrary overlapping gradients that have not previously been possible. The MMI device is fabricated in poly(dimethylsiloxane) (PDMS) using multi-layer soft lithography and consists of fluidic channels and control channels with pneumatically actuated on-chip barrier valves. Repetitive actuation of on-chip valves control pulsatile release of solution that establishes microscopic chemical gradients around the orifice. The volume of solution released per actuation cycle ranged from 30 picolitres to several hundred picolitres and increased linearly with the duration of valve opening. The shape of the measured gradient profile agreed closely with the simulated diffusion profile from a point source. Steady state gradient profiles could be attained within 10 minutes, or less with an optimized pulse sequence. Overlapping gradients from 2 injectors were generated and characterized to highlight the advantages of MMI over conventional micropipette assays. The MMI platform should be useful for a wide range of basic and applied studies on chemotaxis and axon guidance.

Synthesis and magnetic properties of biocompatible hybrid hollow spheres.
Ding Y, Hu Y, Zhang L, Chen Y, Jiang X.
Biomacromolecules. 2006 Jun;7(6):1766-72.
[ expand abstract ]

Magnetic hybrid hollow spheres of about 200 nm were prepared by a core-template-free route, that is, adding Fe(3)O(4) nanoparticles stabilized by poly(vinyl alcohol) (PVA) to an aqueous solution of polymer-monomer pairs composed of a cationic polymer, chitosan (CS), and an anionic monomer, acrylic acid (AA), followed by polymerization of acrylic acid and selective cross-linking of chitosan at the end of polymerization. The obtained hybrid spheres were characterized by dynamic light scattering (DLS) in aqueous solution and observed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) in the solid state. Fourier transform infrared spectroscopy (FTIR) and X-ray and electron diffractions revealed that the Fe(3)O(4) nanoparticles were incorporated into the shells of chitosan-poly(acrylic acid) (CS-AA) hollow spheres. Magnetization studies and Mossbauer spectroscopy suggested that the chains (or islands) of iron oxide nanoparticles were most likely formed in the walls of the hollow spheres. The phantom test of magnetic resonance imaging showed that the synthesized hybrid hollow spheres had a significant magnetic resonance signal enhancement in T2-weighted image.

Nanofluidics and the role of nanocapillary array membranes in mass-limited chemical analysis.
Gatimu EN, Sweedler JV, Bohn PW.
Analyst. 2006 Jun;131(6):705-9; Epub 2006 Apr 27.
[ expand abstract ]

Integrated microfluidic structures, comprised of three-dimensional assemblies of microfluidic channels, can effect sequentially-linked analytical operations with mass-limited samples. This three-dimensional operation is enabled by electrically-switchable nanocapillary array membranes with novel transport properties.

Microfluidic handling of PCR solution and DNA amplification on a reaction chamber array biochip.
Gong H, Ramalingam N, Chen L, Che J, Wang Q, Wang Y, Yang X, Yap PH, Neo CH.
Biomed Microdevices. 2006 Jun;8(2):167-76.
[ expand abstract ]

A microfluidic biochip for conducting an array of polymerase chain reaction (PCR) simultaneously was fabricated to understand the microfluidic loading process of PCR solution into microfabricated glass reaction chambers. The geometrical factors of the microfluidic structure, including the shape and depth of the microchamber, shape and size of the microchannels were investigated on the formation of air bubbles trapped within the microchamber during the PCR solution loading process. Furthermore, the effects of surface properties of the microfluidic structure, including hydrophilicity of the microchamber and inlet channel, and hydrophobicity of the outlet channel, on the loading of PCR solution, especially on the formation of air bubbles were studied. As a result, the surface wetting property of the microchamber was found to be the main reason for the formation of the air bubbles inside the microchamber during the loading of PCR solution in the biochips. A solution to avoid the air trapping has been proposed and investigated.

An optically driven pump for microfluidics.
Leach J, Mushfique H, di Leonardo R, Padgett M, Cooper J.
Lab Chip. 2006 Jun;6(6):735-9; Epub 2006 Apr 28.
[ expand abstract ]

We demonstrate a method for generating flow within a microfluidic channel using an optically driven pump. The pump consists of two counter rotating birefringent vaterite particles trapped within a microfluidic channel and driven using optical tweezers. The transfer of spin angular momentum from a circularly polarised laser beam rotates the particles at up to 10 Hz. We show the that the pump is able to displace fluid in microchannels, with flow rates of up to 200 microm(3) s(-1) (200 fL s(-1)). The direction of fluid pumping can be reversed by altering the sense of the rotation of the vaterite beads. We also incorporate a novel optical sensing method, based upon an additional probe particle, trapped within separate optical tweezers, enabling us to map the magnitude and direction of fluid flow within the channel. The techniques described in the paper have potential to be extended to drive an integrated lab-on-chip device, where pumping, flow measurement and optical sensing could all be achieved by structuring a single laser beam.

Microfluidics/CMOS orthogonal capabilities for cell biology.
Linder V, Koster S, Franks W, Kraus T, Verpoorte E, Heer F, Hierlemann A, de Rooij NF.
Biomed Microdevices. 2006 Jun;8(2):159-66.
[ expand abstract ]

The study of individual cells and cellular networks can greatly benefit from the capabilities of microfabricated devices for the stimulation and the recording of electrical cellular events. In this contribution, we describe the development of a device, which combines capabilities for both electrical and pharmacological cell stimulation, and the subsequent recording of electrical cellular activity. The device combines the unique advantages of integrated circuitry (CMOS technology) for signal processing and microfluidics for drug delivery. Both techniques are ideally suited to study electrogenic mammalian cells, because feature sizes are of the same order as the cell diameter, approximately 50 microm. Despite these attractive features, we observe a size mismatch between microfluidic devices, with bulky fluidic connections to the outside world, and highly miniaturized CMOS chips. To overcome this problem, we developed a microfluidic flow cell that accommodates a small CMOS chip. We simulated the performances of a flow cell based on a 3-D microfluidic system, and then fabricated the device to experimentally verify the nutrient delivery and localized drug delivery performance. The flow-cell has a constant nutrient flow, and six drug inlets that can individually deliver a drug to the cells. The experimental analysis of the nutrient and drug flow mass transfer properties in the flowcell are in good agreement with our simulations. For an experimental proof-of-principle, we successfully delivered, in a spatially resolved manner, a 'drug' to a culture of HL-1 cardiac myocytes.

Self-assembly of dendrimer-encapsulated nanoparticle arrays using 2-d microbial s-layer protein biotemplates.
Mark SS, Bergkvist M, Yang X, Angert ER, Batt CA.
Biomacromolecules. 2006 Jun;7(6):1884-97.
[ expand abstract ]

We investigated the formation of self-assembled two-dimensional (2-D) arrays of dendrimer-encapsulated platinum nanoparticles (Pt-DENs) using prokaryotic surface-layer (S-layer) proteins as biomacromolecular templates. The Pt-DENs (mean core diameter 1.8 +/- 0.5 nm) were synthesized by chemical reduction of metal ion species complexed within the interior of fourth-generation, hydroxyl-terminated, starburst poly(amidoamine) dendrimers (G4 PAMAM-OH). Detailed structural and elemental composition analyses performed using high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy indicated that the dendrimer-metal nanocomposite particles were crystalline in nature rather than amorphous and that at least some quantity of the platinum found within the particles is present in the expected zerovalent state. By using the S-layer lattices from the acidothermophilic archaeon Sulfolobus acidocaldarius and the Gram-positive bacterium Deinococcus radiodurans as a biotemplate, hexagonal- and honeycomb-ordered arrays of the Pt-DENs were successfully fabricated under a range of different pH conditions via noncovalent nanoparticle-protein interactions. Fast Fourier transform analyses of transmission electron microscopy images verified that the fabricated Pt-DEN assemblies displayed mean periodicities that corresponded well with the lattice constants of the native protein templates (i.e., 22 and 18 nm for S. acidocaldarius and D. radiodurans S layers, respectively). Our results demonstrate that utilizing pre-synthesized Pt-DENs in conjunction with microbial S-layer proteins displaying highly periodic topochemical properties can be an effective, novel route for creating patterned arrays of Pt nanoparticles with potential technological applications.

Study on Drug Release Behaviors of Poly-alpha,beta-[N-(2-hydroxyethyl)-l-aspartamide]-g-poly(epsilon-caprolactone) Nano- and Microparticles.
Miao ZM, Cheng SX, Zhang XZ, Zhuo RX.
Biomacromolecules. 2006 Jun;7(6):2020-6.
[ expand abstract ]

Biodegradable amphiphilic graft copolymers poly-alpha,beta-[N-(2-hydroxyethyl)-l-aspartamide]-g-poly(epsilon-caprolactone) (PHEA-g-PCL) with different branch lengths were synthesized through the ring-opening polymerization of epsilon-caprolactone initiated by the macroinitiator PHEA bearing hydroxyl groups. With use of the graft copolymers with different compositions, nanoparticle drug delivery systems with sizes smaller than 100 nm were prepared by a dialysis method, and microparticle drug delivery systems with sizes smaller than 5 mum were fabricated by a melting-emulsion method. The regularly spherical shapes of the drug-loaded nano- and microparticles were verified by transmission electron microscopy and scanning electron microscopy. In vitro drug release properties of nano- and microparticle drug delivery systems were investigated, with the emphasis on the effects of polymer composition, particle size, and drug-loading content on the release behaviors.

Magnetic-based microfluidic platform for biomolecular separation.
Ramadan Q, Samper V, Poenar D, Yu C.
Biomed Microdevices. 2006 Jun;8(2):151-8.
[ expand abstract ]

A novel microfluidic platform for manipulation of micro/nano magnetic particles was designed, fabricated and tested for applications dealing with biomolecular separation. Recently, magnetic immunomagnetic cell separation has attracted a noticeable attention due to the high selectivity of such separation methods. Strong magnetic field gradients can be developed along the entire wire, and the miniaturized size of these current-carrying conductors strongly enhances the magnetic field gradient and therefore produces large, tunable and localized magnetic forces that can be applied on magnetic particles and confine them in very small spots. Further increases in the values of the generated magnetic field gradients can be achieved by employing miniaturized ferromagnetic structures (pillars) which can be magnetized by an external magnetic field or by micro-coils on the same chip. In this study, we demonstrate magnetic beads trapping, concentration, transportation and sensing in a liquid sample under continuous flow by employing high magnetic field gradients generated by novel multi-functional magnetic micro-devices. Each individual magnetic micro-device consists of the following components: 1. Cu micro-coils array embedded in the silicon substrate with high aspect ratio conductors for efficient magnetic field generation 2. Magnetic pillar(s) made of the magnetic alloy NiCoP for magnetic field focusing and magnetic field gradient enhancement. Each pillar is magnetized by its corresponding coil 3. Integrated sensing coil for magnetic beads detection 4. Microfluidic chamber containing all the previous components. Magnetic fields of about 0.1 T and field gradients of around 300 T/cm have been achieved, which allowed to develop a magnetic force of 3 x 10(-9) N on a magnetic particle with radius of 1 mum. This force is large enough to trap/move this particle as the required force to affect such particles in a liquid sample is on the order of approximately pN. Trapping rates of up to 80% were achieved. Furthermore, different micro-coil designs were realized which allowed various movement modes and with different step-sizes.These results demonstrate that such devices incorporated within a microfluidic system can provide significantly improved spatial resolution and force magnitude for quick, efficient and highly selective magnetic trapping, separation and transportation, and as such they are an excellent solution for miniaturized mu-total analysis systems.

FloDots: luminescent nanoparticles.
Yao G, Wang L, Wu Y, Smith J, Xu J, Zhao W, Lee E, Tan W.
Anal Bioanal Chem. 2006 Jun;385(3):518-24; Epub 2006 May 6.
[ expand abstract ]

Luminescent dye-doped silica nanoparticles (FloDots) have been developed for ultrasensitive bioanalysis and diagnosis in the past several years. Those novel nanoparticles are highly luminescent and extremely photostable. In this paper, we review the preparation, characterization, bioconjugation and bioapplication of FloDots. All the results clearly demonstrated that FloDots have many advantages over currently used luminescent probes, such as traditional fluorophores and quantum dots.

Tandem synthesis of core-shell brush copolymers and their transformation to peripherally cross-linked and hollowed nanostructures.
Cheng C, Qi K, Khoshdel E, Wooley KL.
J Am Chem Soc. 2006 May 31;128(21):6808-9.
[ expand abstract ]

Core-shell brush copolymers were prepared on the basis of a tandem synthetic strategy and used as single molecular templates for the preparation of polymeric nanomaterials. An alkoxyamine-functionalized norbornene monomer was prepared and then polymerized by ring-opening metathesis polymerization. The well-defined polymer (M(n) = 122 kDa, M(w)/M(n) = 1.13) contained one alkoxyamine functionality per repeat unit and was then used as a polyfunctional macroinitiator for sequential nitroxide-mediated radical polymerizations of isoprene and tert-butyl acrylate. The resulting well-defined brush copolymer (M(n) = 1410 kDa, M(w)/M(n) = 1.23) was transformed to an amphiphilic core-shell brush copolymer comprising poly(isoprene)-b-poly(acrylic acid) grafts by hydrolysis. Subsequent cross-linking of the poly(acrylic acid) block segments afforded peripherally cross-linked brush copolymer nanostructures, which served, finally, as templates for hollowed nanoscale frameworks by ozonolysis of the poly(isoprene)-based cores. Each transformation led to dramatic changes in the nanoscale composition and structure which were detected by combinations of spectroscopic measurements, atomic force microscopy imaging in the solid state, and/or dynamic light-scattering characterization in aqueous solution.

Oligonucleotide-arrayed TFT photosensor applicable for DNA chip technology.
Tanaka T, Hatakeyama K, Sawaguchi M, Iwadate A, Mizutani Y, Sasaki K, Tateishi N, Takeyama H, Matsunaga T.
Biotechnol Bioeng. 2006 May 26; [Epub ahead of print] .
[ expand abstract ]

A thin film transistor (TFT) photosensor fabricated by semiconductor IC technology was applied to DNA chip technology. The surface of the TFT photosensor was coated with TiO(2) using a vapor deposition technique for the fabrication of optical filters. The immobilization of thiolated oligonucleotide probes onto a TiO(2)-coated TFT photosensor using gamma-aminopropyltriethoxysilane (APTES) and N-(gamma-maleimidobutyloxy) sulfosuccinimide ester (GMBS) was optimized. The coverage value of immobilized oligonucleotides reached a plateau at 33.7 pmol/cm(2), which was similar to a previous analysis using radioisotope-labeled oligonucleotides. The lowest detection limits were 0.05 pmol/cm(2) for quantum dot and 2.1 pmol/cm(2) for AlexaFluor350. Furthermore, single nucleotide polymorphism (SNP) detection was examined using the oligonucleotide-arrayed TFT photosensor. A SNP present in the aldehyde dehydrogenase 2 (ALDH2) gene was used as a target. The SNPs in ALDH2*1 and ALDH2*2 target DNA were detected successfully using the TFT photosensor. DNA hybridization in the presence of both ALDH2*1 and ALDH2*2 target DNA was observed using both ALDH2*1 and ALDH2*2 detection oligonucleotides arrayed TFT photosensor. Use of the TFT photosensor will allow the development of a disposable photodetecting device for DNA chip systems.

Aspen SP1, an exceptional thermal, protease and detergent resistant self-assembled nano-particle.
Wang WX, Dgany O, Wolf SG, Levy I, Algom R, Pouny Y, Wolf A, Marton I, Altman A, Shoseyov O.
Biotechnol Bioeng. 2006 May 26; [Epub ahead of print] .
[ expand abstract ]

Stable protein 1 (SP1) is a homo-oligomeric protein isolated from aspen (Populus tremula aspen) plants which forms a ring-shape dodecameric particle with a central cavity. The oligomeric form of SP1 is an exceptionally stable structure that is resistant to proteases (e.g. trypsin, V8 and proteinase K), high temperatures, organic solvents and high levels of ionic detergent. Analytical ultra-centrifugation, chemical cross-linking, matrix-assisted laser-desorption time-of-flight mass spectrometry and transmission electron microscopy were used to further characterise the SP1 dodecamer. Introduction of a single cysteine at the N-terminus of SP1 enabled the formation of disulfide bridges within the SP1 dodecamer, concurrent with increased melting point. A six-histidine tag was introduced at the N-terminus of SP1 to generate 6HSP1, and the DeltaNSP1 mutant was generated by a deletion of amino acids 2-6 at the N-terminus. Both 6HSP1 and DeltaNSP1 maintained their ability to assemble a stable dodecamer. Remarkably, these SP1 homo-dodecamers were able to re-assemble into stable hetero-dodecamers following co-electroelution from SDS-PAGE. The exceptional stability of the SP1-nano ring and its ability to self-assemble hetero-complexes paves the way to further research in utilising this unique protein in nano-biotechnology.

Micellar electrokinetic chromatography of fluorescently labeled proteins on poly(dimethylsiloxane)-based microchips.
Roman GT, Carroll S, McDaniel K, Culbertson CT.
Electrophoresis. 2006 May 24; [Epub ahead of print] .
[ expand abstract ]

MEKC of standard proteins was investigated on PDMS microfluidic devices. Standard proteins were labeled with AlexaFluor(R) 488 carboxylic acid tetrafluorophenyl ester and filtered through a size-exclusion column to remove any small peptides and unreacted label. High-efficiency MEKC separations of these standard proteins were performed using a buffer consisting of 10 mM sodium tetraborate, 25 mM SDS, and 20% v/v ACN. A separation of BSA using this buffer in a 3.0 cm long channel generated a peak with a plate height of 0.38 mum in <20 s. Additional fast separations of myoglobin, alpha-lactalbumin, lysozyme, and cytochrome c also yielded peaks with plate heights ranging from 0.54 to 0.72 mum. All proteins migrated with respect to their individual pIs. To improve the separations, we used a PDMS serpentine chip with tapered turns and a separation distance of 25 cm. The number of plates generated increased linearly with increasing separation distance on the extended separation channel chips; however, the resolution reached an asymptotic value after about 7 cm. This limited the peak capacity of the separation technique to 10-12.

Tailored recombinant elastin-like polymers for advanced biomedical and nano(bio)technological applications.
Arias FJ, Reboto V, Martin S, Lopez I, Rodriguez-Cabello JC.
Biotechnol Lett. 2006 May 23; [Epub ahead of print] .
[ expand abstract ]

The genetic engineering of protein-based polymers is a method that enables, in an easy way, the design of complex and highly functional macromolecules. As examples of this approach, different molecular designs are presented, with increasing degree of complexity, showing how the controlled increase in their complexity yields (multi)functional materials with more selected and sophisticated properties. The simplest designs show interesting properties already, but the adequate introduction of given chemical functions along the polymer chain provides an opportunity to expand the range of properties to enhanced smart behavior and self-assembly. Finally, examples are given where those molecular designs further incorporate selected bioactivities in order to develop materials for the most cutting edge applications in biomedicine and nano(bio)technology.

Integrated polymerase chain reaction chips utilizing digital microfluidics.
Chang YH, Lee GB, Huang FC, Chen YY, Lin JL.
Biomed Microdevices. 2006 May 20; [Epub ahead of print] .
[ expand abstract ]

This study reports an integrated microfluidic chip for polymerase chain reaction (PCR) applications utilizing digital microfluidic chip (DMC) technology. Several crucial procedures including sample transportation, mixing, and DNA amplification were performed on the integrated chip using electro-wetting-on-dielectric (EWOD) effect. An innovative concept of hydrophobic/hydrophilic structure has been successfully demonstrated to integrate the DMC chip with the on-chip PCR device. Sample droplets were generated, transported and mixed by the EWOD-actuation. Then the mixture droplets were transported to a PCR chamber by utilizing the hydrophilic/hydrophobic interface to generate required surface tension gradient. A micro temperature sensor and two micro heaters inside the PCR chamber along with a controller were used to form a micro temperature control module, which could perform precise PCR thermal cycling for DNA amplification. In order to demonstrate the performance of the integrated DMC/PCR chips, a detection gene for Dengue II virus was successfully amplified and detected. The new integrated DMC/PCR chips only required an operation voltage of 12V(RMS) at a frequency of 3 KHz for digital microfluidic actuation and 9V(DC) for thermal cycling. When compared to its large-scale counterparts for DNA amplification, the developed system consumed less sample and reagent and could reduce the detection time. The developed chips successfully demonstrated the feasibility of Lab-On-a-Chip (LOC) by utilizing EWOD-based digital microfluidics.

FloDots: luminescent nanoparticles.
Yao G, Wang L, Wu Y, Smith J, Xu J, Zhao W, Lee E, Tan W.
Anal Bioanal Chem. 2006 May 6; [Epub ahead of print].
[ expand abstract ]

Luminescent dye-doped silica nanoparticles (FloDots) have been developed for ultrasensitive bioanalysis and diagnosis in the past several years. Those novel nanoparticles are highly luminescent and extremely photostable. In this paper, we review the preparation, characterization, bioconjugation and bioapplication of FloDots. All the results clearly demonstrated that FloDots have many advantages over currently used luminescent probes, such as traditional fluorophores and quantum dots.

Proteolytic Actuation of Nanoparticle Self-Assembly.
Harris TJ, von Maltzahn G, Derfus AM, Ruoslahti E, Bhatia SN.
Angew Chem Int Ed Engl. 2006 May 5;45(19):3161-3165.
[ expand abstract ]

No abstract available

Bienzyme sensors based on novel polymethylferrocenyl dendrimers.
Losada J, Zamora M, Garcia Armada P, Cuadrado I, Alonso B, Casado CM.
Anal Bioanal Chem. 2006 May 4; [Epub ahead of print].
[ expand abstract ]

Amperometric bienzyme electrodes with horseradish peroxidase (HRP) and glucose oxidase (GOx) co-immobilized on polymethylferrocenyl dendrimers deposited onto platinum electrodes have been used for determination of the hydrogen peroxide produced by the oxidase during the enzymatic reaction. The redox dendrimers consist of flexible poly(propylenimine) dendrimer cores functionalised with octamethylferrocenyl units. The effects of dendrimer generation, the thickness of the dendrimer layer, substrate concentration, interferences, and reproducibility on the response of the sensors were investigated. The new bienzyme biosensors respond to substrate at work potential values between 200 and 50 mV (vs. SCE), have good sensitivity, and are resistant to interferences.

Direct electrochemical immunoassay based on a silica nanoparticles/sol-gel composite architecture for encapsulation of immunoconjugate.
Wang FC, Yuan R, Chai YQ.
Appl Microbiol Biotechnol. 2006 May 4; [Epub ahead of print].
[ expand abstract ]

A highly hydrophobic and non-toxic colloidal silica nanoparticle/polyvinyl butyral sol-gel composite membrane was prepared on a platinum wire electrode. With diphtheria-toxoid (D-Ag) as a model antigen and encapsulation of diphtheria antibody (D-Ab) in the composite architecture, this membrane could be used for reagentless electrochemical immunoassay. It displayed a porous and homogeneous composite architecture without the aggregation of the immobilized protein molecules. The formation of immunoconjugate by a simple one-step immunoreaction between D-Ag in sample solution and the immobilized D-Ab introduced the change in the potential. Under optimal conditions, the D-Ag analyte could be determined in the linear ranges from 10 to 800 ng ml(-1) with a relatively low detection limit of 2.3 ng ml(-1) at 3delta. The D-Ag immunosensor exhibited good precision, high sensitivity, acceptable stability, accuracy, and reproducibility. This composite membrane could be used efficiently for the entrapment of different biomarkers and clinical applications.

Controlled microfluidic encapsulation of cells, proteins, and microbeads in lipid vesicles.
Tan YC, Hettiarachchi K, Siu M, Pan YR, Lee AP.
J Am Chem Soc. 2006 May 3;128(17):5656-8.
[ expand abstract ]

Cells have been encapsulated inside lipid vesicles by using a new microfluidic lipid vesicle formulation technique. Lipid vesicles are formulated within minutes without using toxic lipid solvents. The encapsulation efficiency inside the vesicles is controlled by the microfluidic flows. Green fluorescent proteins (GFP), carcinoma cells, and bead encapsulated vesicles have mean diameters of 27.2 mum, 62.4 mum, and 55.9 mum, respectively. The variations of vesicle sizes are approximately 20% for the GFP and cell encapsulated vesicles and approximately 10% for the bead encapsulated vesicles.

HPLC method for determination of SN-38 content and SN-38 entrapment efficiency in a novel liposome-based formulation, LE-SN38.
Xuan T, Zhang JA, Ahmad I.
J Pharm Biomed Anal. 2006 May 3;41(2):582-8; Epub 2006 Jan 18.
[ expand abstract ]

A simple HPLC method was developed for quantification of SN-38, 7-ethyl-10-hydroxycamptothecin, in a novel liposome-based formulation (LE-SN38). The chromatographic separation was achieved on an Agilent Zorbax SB-C18 (4.6mmx250mm, 5mum) analytical column using a mobile phase consisting of a mixture of NaH(2)PO(4) (pH 3.1, 25mM) and acetonitrile (50:50, v/v). SN-38 was detected at UV wavelength of 265nm and quantitatively determined using an external calibration method. The limit of detection (LOD) and limit of quantitation (LOQ) were found to be 0.05 and 0.25mug/mL, respectively. The individual spike recovery of SN-38 ranged from 100 to 101%. The percent of relative standard deviation (%R.S.D.) of intra-day and inter-day analyses were less than 1.6%. The method validation results confirmed that the method is specific, linear, accurate, precise, robust and sensitive for its intended use. The current method was successfully applied to the determination of SN-38 content and drug entrapment efficiency in liposome-based formulation, LE-SN38 during early stage formulation development.

Microfluidic cartridges preloaded with nanoliter plugs of reagents: an alternative to 96-well plates for screening.
Chen DL, Ismagilov RF.
Curr Opin Chem Biol. 2006 May 2; [Epub ahead of print].
[ expand abstract ]

In traditional screening with 96-well plates, microliters of substrates are consumed for each reaction. Further miniaturization is limited by the special equipment and techniques required to dispense nanoliter volumes of fluid. Plug-based microfluidics confines reagents in nanoliter plugs (droplets surrounded by fluorinated carrier fluid), and uses simple pumps to control the flow of plugs. By using cartridges pre-loaded with nanoliter plugs of reagents, only two pumps and a merging junction are needed to set up a screen. Screening with preloaded cartridges uses only nanoliters of substrate per reaction, and requires no microfabrication. The low cost and simplicity of this method has the potential of replacing 96-well and other multi-well plates, and has been applied to enzymatic assays, protein crystallization and optimization of organic reactions.

PCR microfluidic devices for DNA amplification.
Zhang C, Xu J, Ma W, Zheng W.
Biotechnol Adv. 2006 May-Jun;24(3):243-84. Epub 2005 Dec 2.
[ expand abstract ]

The miniaturization of biological and chemical analytical devices by micro-electro-mechanical-systems (MEMS) technology has posed a vital influence on such fields as medical diagnostics, microbial detection and other bio-analysis. Among many miniaturized analytical devices, the polymerase chain reaction (PCR) microchip/microdevices are studied extensively, and thus great progress has been made on aspects of on-chip micromachining (fabrication, bonding and sealing), choice of substrate materials, surface chemistry and architecture of reaction vessel, handling of necessary sample fluid, controlling of three or two-step temperature thermocycling, detection of amplified nucleic acid products, integration with other analytical functional units such as sample preparation, capillary electrophoresis (CE), DNA microarray hybridization, etc. However, little has been done on the review of above-mentioned facets of the PCR microchips/microdevices including the two formats of flow-through and stationary chamber in spite of several earlier reviews [Zorbas, H. Miniature continuous-flow polymerase chain reaction: a breakthrough? Angew Chem Int Ed 1999; 38 (8):1055-1058; Krishnan, M., Namasivayam, V., Lin, R., Pal, R., Burns, M.A. Microfabricated reaction and separation systems. Curr Opin Biotechnol 2001; 12:92-98; Schneegabeta, I., Kohler, J.M. Flow-through polymerase chain reactions in chip themocyclers. Rev Mol Biotechnol 2001; 82:101-121; deMello, A.J. DNA amplification: does 'small' really mean 'efficient'? Lab Chip 2001; 1: 24N-29N; Mariella, Jr. R. MEMS for bio-assays. Biomed Microdevices 2002; 4 (2):77-87; deMello AJ. Microfluidics: DNA amplification moves on. Nature 2003; 422:28-29; Kricka, L.J., Wilding, P. Microchip PCR. Anal BioAnal Chem 2003; 377:820-825]. In this review, we survey the advances of the above aspects among the PCR microfluidic devices in detail. Finally, we also illuminate the potential and practical applications of PCR microfluidics to some fields such as microbial detection and disease diagnosis, based on the DNA/RNA templates used in PCR microfluidics. It is noted, especially, that this review is to help a novice in the field of on-chip PCR amplification to more easily find the original papers, because this review covers almost all of the papers related to on-chip PCR microfluidics.

Chemical nano-corking.
Doerr A.
Nat Methods. 2006 May;3(5):338.
[ expand abstract ]

Silica nano test tubes used as delivery vehicles can be 'corked' with nanoparticles using chemical self-assembly.

Design and fabrication of a multilayered polymer microfluidic chip with nanofluidic interconnects via adhesive contact printing.
Flachsbart BR, Wong K, Iannacone JM, Abante EN, Vlach RL, Rauchfuss PA, Bohn PW, Sweedler JV, Shannon MA.
Lab Chip. 2006 May;6(5):667-74. Epub 2006 Mar 17.
[ expand abstract ]

The design and fabrication of a multilayered polymer micro-nanofluidic chip is described that consists of poly(methylmethacrylate) (PMMA) layers that contain microfluidic channels separated in the vertical direction by polycarbonate (PC) membranes that incorporate an array of nanometre diameter cylindrical pores. The materials are optically transparent to allow inspection of the fluids within the channels in the near UV and visible spectrum. The design architecture enables nanofluidic interconnections to be placed in the vertical direction between microfluidic channels. Such an architecture allows microchannel separations within the chip, as well as allowing unique operations that utilize nanocapillary interconnects: the separation of analytes based on molecular size, channel isolation, enhanced mixing, and sample concentration. Device fabrication is made possible by a transfer process of labile membranes and the development of a contact printing method for a thermally curable epoxy based adhesive. This adhesive is shown to have bond strengths that prevent leakage and delamination and channel rupture tests exceed 6 atm (0.6 MPa) under applied pressure. Channels 100 microm in width and 20 microm in depth are contact printed without the adhesive entering the microchannel. The chip is characterized in terms of resistivity measurements along the microfluidic channels, electroosmotic flow (EOF) measurements at different pH values and laser-induced-fluorescence (LIF) detection of green-fluorescent protein (GFP) plugs injected across the nanocapillary membrane and into a microfluidic channel. The results indicate that the mixed polymer micro-nanofluidic multilayer chip has electrical characteristics needed for use in microanalytical systems.

An effervescent reaction micropump for portable microfluidic systems.
Good BT, Bowman CN, Davis RH.
Lab Chip. 2006 May;6(5):659-66; Epub 2006 Mar 20.
[ expand abstract ]

A water-activated, effervescent reaction was used to transport fluid in a controllable manner on a portable microfluidic device. The reaction between sodium bicarbonate and an organic acid, tartaric acid and/or benzoic acid, was modeled to analyze methods of controlling the generation of carbon-dioxide gas for the purposes of pumping fluids. Integration and testing of the effervescent reaction pump in a microfluidic device was made possible by using elastomeric polymers as both photopolymerizable septa and removable lids. These materials combined to enable facile access to otherwise gas-tight devices. Based on theoretical predictions for 0.33 mg of sodium bicarbonate and a stoichiometric amount of organic acid, the pumping flow rate could be varied from 0.01 microL s(-1) to 70 microL s(-1). The flow rate is controlled by adjusting any or all of the particle size of the least soluble reactant, the amount of reactants used, and the type of organic acid selected. The tartaric acid systems rapidly produce carbon dioxide; however, the gas generation rates dramatically decrease over the course of the reaction. In contrast, carbon dioxide production rate in the benzoic acid systems is lower and nearly constant for several minutes. Water activation and direct placement on a microfluidic device are key features of this micropump, which is therefore useful for portable microfluidic applications.

Thiolated PAMAM dendrimer-coated CdSe/ZnSe nanoparticles as protein transfection agents.
Wisher AC, Bronstein I, Chechik V.
Chem Commun (Camb). 2006 Apr 21;(15):1637-9; Epub 2006 Mar 16.
[ expand abstract ]

Functionalisation of PAMAM dendrimers with a small number of thiol groups makes them good ligands for CdSe/ZnSe nanoparticles; the particles coated with thiolated dendrimers have good cell permeability and are potent transfection agents.

A gold nanoparticle based approach for screening triplex DNA binders.
Han MS, Lytton-Jean AK, Mirkin CA.
J Am Chem Soc. 2006 Apr 19;128(15):4954-5.
[ expand abstract ]

Nanoparticle assemblies interconnected with DNA triple helixes can be used to colorimetrically screen for triplex DNA binding molecules and simultaneously determine their relative binding affinities based on melting temperatures. Nanoparticles assemble only when DNA triple helixes form between DNA from two different particles and a third strand of free DNA. In addition, the triple helix structure is unstable at room temperature and only forms in the presence of triplex DNA binding molecules which stabilize the triple helix. The resulting melting transition of the nanoparticle assembly is much sharper and at a significantly higher T(m) than the analogous triplex structure without nanoparticles. Upon nanoparticle assembly, a concomitant red-to-blue color change occurs. The assembly process and color change do not occur in the presence of duplex DNA binders and therefore provide a significantly better screening process for triplex DNA binding molecules compared to standard methods.

Fluorescent Signal Amplification of Carbocyanine Dyes Using Engineered Viral Nanoparticles.
Soto CM, Blum AS, Vora GJ, Lebedev N, Meador CE, Won AP, Chatterji A, Johnson JE, Ratna BR.
J Am Chem Soc. 2006 Apr 19;128(15):5184-5189.
[ expand abstract ]

We report enhancement in the fluorescent signal of the carbocyanine dye Cy5 by using an engineered virus as a scaffold to attach >40 Cy5 reporter molecules at fixed locations on the viral capsid. Although cyanine dye loading is often accompanied by fluorescence quenching, our results demonstrate that organized spatial distribution of Cy5 reporter molecules on the capsid obviates this commonly encountered problem. In addition, we observe energy transfer from the virus to adducted dye molecules, resulting in a highly fluorescent viral nanoparticle. We have used this enhanced fluorescence for the detection of DNA-DNA hybridization. When compared with the most often used detection methods in a microarray-based genotyping assay for Vibrio cholerae O139, these viral nanoparticles markedly increased assay sensitivity, thus demonstrating their applicability for existing DNA microarray protocols.

A nanoparticle-dendrimer conjugate prepared from a one-step chemical coupling of monofunctional nanoparticles with a dendrimer.
Worden JG, Dai Q, Huo Q.
Chem Commun (Camb). 2006 Apr 14;(14):1536-8; [Epub 2006 Feb 28].
[ expand abstract ]

Gold nanoparticle-dendrimer conjugate clusters were prepared by a covalent coupling of monofunctional gold nanoparticles with a generation 5 PAMAM dendrimer.

Fast and sensitive analysis of DNA hybridization in a PDMS micro-fluidic channel using fluorescence resonance energy transfer.
Yea KH, Lee S, Choo J, Oh CH, Lee S.
Chem Commun (Camb). 2006 Apr 14;(14):1509-11; [Epub 2006 Feb 28].
[ expand abstract ]

Fluorescence resonance energy transfer has been used to illustrate its applicability to the sensitive detection of DNA hybridization reactions in a PDMS microfluidic channel.

Magnetic carbon nanotubes: synthesis by electrostatic self-assembly approach and application in biomanipulations.
Gao C, Li W, Morimoto H, Nagaoka Y, Maekawa T.
J Phys Chem B Condens Matter Mater Surf Interfaces Biophys. 2006 Apr 13;110(14):7213-20.
[ expand abstract ]

Magnetic multiwalled carbon nanotubes (MWNTs) were facilely prepared by the electrostatic self-assembly approach. Poly(2-diethylaminoethyl methacrylate) (PDEAEMA) was covalently grafted onto the surfaces of MWNTs by MWNT-initiated in situ atom transfer radical polymerization (ATRP) of 2-diethylaminoethyl methacrylate (DEAEMA). The PDEAEMA-grafted MWNTs were quaternized with methyl iodide (CH(3)I), resulting in cationic polyelectrolyte-grafted MWNTs (MWNT-PAmI). Magnetic iron oxide (Fe(3)O(4)) nanoparticles were loaded onto the MWNT surfaces by electrostatic self-assembling between MWNT-PAmI and Fe(3)O(4), affording magnetic nanotubes. The assembled capability of the nanoparticles can be adjusted to some extent by changing the feed ratio of Fe(3)O(4) to MWNT-PAmI. The obtained magnetic nanotubes were characterized with TEM, EDS, STEM, and element mapping analyses. TEM and EDS measurements confirmed the nanostructures and the components of the resulting nanoobjects. The magnetic nanotubes were assembled onto sheep red blood cells in a phosphate buffer solution, forming magnetic cells. The blood cells attached with or without magnetic nanotubes can be selectively manipulated in a magnetic field. These results promise a general and efficient strategy to magnetic nanotubes and the fascinating potential of such magnetic nanoobjects in applications of bionanoscience and technology.

Laser-Assisted Synthesis of Superparamagnetic Fe@Au Core-Shell Nanoparticles.
Zhang J, Post M, Veres T, Jakubek ZJ, Guan J, Wang D, Normandin F, Deslandes Y, Simard B.
J Phys Chem B Condens Matter Mater Surf Interfaces Biophys. 2006 Apr 13;110(14):7122-7128.
[ expand abstract ]

A novel method combining wet chemistry for synthesis of an Fe core, 532 nm laser irradiation of Fe nanoparticles and Au powder in liquid medium for deposition of an Au shell, and sequential magnetic extraction/acid washing for purification has been developed to fabricate oxidation-resistant Fe@Au magnetic core-shell nanoparticles. The nanoparticles have been extensively characterized at various stages during and up to several months after completion of the synthesis by a suite of electron microscopy techniques (HRTEM, HAADF STEM, EDX), X-ray diffraction (XRD), UV-vis spectroscopy, inductively coupled plasma atomic emission spectroscopy, and magnetometry. The surface plasmon resonance of the Fe@Au nanoparticles is red shifted and much broadened as compared with that of pure colloidal nano-gold, which is explained to be predominantly a shell-thickness effect. The Au shell consists of partially fused approximately 3-nm-diameter fcc Au nanoparticles (lattice interplanar distance, d = 2.36 A). The 18-nm-diameter magnetic core is bcc Fe single domain (d = 2.03 A). The nanoparticles are superparamagnetic at room temperature (300 K) with a blocking temperature, T(b), of approximately 170 K. After 4 months of shelf storage in normal laboratory conditions, their mass magnetization per Fe content was measured to be 210 emu/g, approximately 96% of the Fe bulk value.

Nanoparticle-Templated Assembly of Viral Protein Cages.
Chen C, Daniel MC, Quinkert ZT, De M, Stein B, Bowman VD, Chipman PR, Rotello VM, Kao CC, Dragnea B.
Nano Lett. 2006 Apr 12;6(4):611-615.
[ expand abstract ]

Self-assembly of regular protein surfaces around nanoparticle templates provides a new class of hybrid biomaterials with potential applications in medical imaging and in bioanalytical sensing. We report here the first example of efficiently self-assembled virus-like particles (VLPs) having a brome mosaic virus protein coat and a functionalized gold core. The present study indicates that functionalized gold particles can initiate VLP assembly by mimicking the electrostatic behavior of the nucleic acid component of the native virus. These VLP constructs are symmetric, with the protein stoichiometry and packaging properties indicating similarity to the icosahedral packing of the capsid. Moreover, a pH-induced swelling transition of the VLPs is observed, in direct analogy to the native virus.

Determining the Size and Shape Dependence of Gold Nanoparticle Uptake into Mammalian Cells.
Chithrani BD, Ghazani AA, Chan WC.
Nano Lett. 2006 Apr 12;6(4):662-668.
[ expand abstract ]

We investigated the intracellular uptake of different sized and shaped colloidal gold nanoparticles. We showed that kinetics and saturation concentrations are highly dependent upon the physical dimensions of the nanoparticles (e.g., uptake half-life of 14, 50, and 74 nm nanoparticles is 2.10, 1.90, and 2.24 h, respectively). The findings from this study will have implications in the chemical design of nanostructures for biomedical applications (e.g., tuning intracellular delivery rates and amounts by nanoscale dimensions and engineering complex, multifunctional nanostructures for imaging and therapeutics).

Blood Compatible Carbon Nanotubes - Nano-based Neoproteoglycans.
Murugesan S, Park TJ, Yang H, Mousa S, Linhardt RJ.
Langmuir. 2006 Apr 11;22(8):3461-3463.
[ expand abstract ]

Although nanotechnology has provided a rich variety of nanomaterials (1-100 nm) for in vivo medical applications, the blood compatibility of all these nanobiomaterials is still largely unexamined. Here, we report the preparation of blood-compatible carbon nanotubes (CNTs) that potentially represent the building blocks for nanodevices having in vivo applications. Activated partial thromboplastin time (APTT) and thromboelastography (TEG) studies prove that heparinization can significantly enhance the blood compatibility of nanomaterials.

In-situ encapsulation of quantum dots into polymer microspheres.
Sheng W, Kim S, Lee J, Kim SW, Jensen K, Bawendi MG.
Langmuir. 2006 Apr 11;22(8):3782-90.
[ expand abstract ]

We have incorporated fluorescent quantum dots (QDs) into polystyrene microspheres using functionalized oligomeric phosphine (OP) ligands. We find that a uniform distribution of quantum dots is loaded inside each polymer bead. Some local close-packing of quantum dots in the beads is attributed to the self-polymerization of the functionalized ligands. The presence of quantum dots disturbs the nucleation and growth processes during the formation of polymer microspheres and results in a wider size distribution of the quantum dot-embedded polystyrene beads than for the control without dots. The change in quantum efficiency of the quantum dots before ( approximately 20%) and after (12%) loading into the beads substantiates the protection of oligomeric phosphine ligands yet indicates that the properties of these quantum dots are still affected during processing.

DNA nano-carriers from biodegradable cationic branched polyesters are formed by a modified solvent displacement method.
Oster CG, Wittmar M, Bakowsky U, Kissel T.
J Control Release. 2006 Apr 10;111(3):371-81; [Epub 2006 Feb 24].
[ expand abstract ]

DNA nano-carriers were formulated relying on biodegradable polyesters consisting of amine-modified poly(vinyl alcohol) (PVAL) backbones grafted with PLGA, based on the Marangoni effect thus avoiding detrimental shear or ultrasonic forces. These amine modified high molecular weight biodegradable polyesters combine specific characteristics, such as electrostatic interactions between DNA and cationic branched polyesters facilitating loading of NP with DNA. The resulting DNA containing NP showed hydrodynamic diameters in the range of 175-285 nm and highly positive xi-potentials, depending on the nitrogen to phosphate (N/P) ratio used for the particle formation. Atomic force microscopy (AFM) demonstrated well-defined spherical particle morphologies. DNA was released from NP upon incubation in PBS buffer in its intact supercoiled form. Agarose gel electrophoresis demonstrated that DNA within the NP was protected from enzyme degradation. The biological efficiency of the DNA delivery by this nano-carrier was demonstrated by an in vitro transfection assay using four cell lines. Reporter gene delivery of the amine-modified polymers was higher than naked DNA (Control) and raised with increasing degree of amine substitution. Also type of amine and distance of cationic charge from the backbone play an important role. Further, this feature was shown by Luciferase expression of the pCMV-Luc plasmid with PEI 25 kDa/DNA polyplexes and NP prepared with amine modified polyesters with a grafted PLGA chain length of 10 monomers compared at equal N/P ratios. DNA loaded NP from P(68)-10 showed 8x higher transfection efficiencies than the PEI 25 kDa at an N/P ratio of 9 for both preparations. These novel DNA nano-carriers merit further investigations in particular for DNA vaccination under in vivo conditions.

Preparation, characterization, resistance to protein adsorption, and specific avidin-biotin binding of poly(amidoamine) dendrimers functionalized with oligo(ethylene glycol) on gold.
Yam CM, Deluge M, Tang D, Kumar A, Cai C.
J Colloid Interface Sci. 2006 Apr 1;296(1):118-30; [Epub 2005 Oct 13].
[ expand abstract ]

Protein-resistant films derived from the fifth-generation poly(amidoamine) dendrimers (PAMAM G5) functionalized with oligo(ethylene glycol) (OEG) derivatives consisting of various ethylene glycol units (EG(n), n = 3, 4, and 6) were prepared on the self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA) on gold substrates. The resulting films were characterized by ellipsometry, contact angle goniometry, and X-ray photoelectron spectroscopy (XPS). About 35% of the peripheral amines of the dendrimers were reacted with N-hydroxysuccinimide-terminated EG(n) derivatives (NHS-EG(n)). The dendrimer films showed improved stability over octadecanethiolate SAMs on gold in hot solvents, attributed to the formation of multiple amide bonds per PAMAM unit with underlying NHS-activated MUA monolayer. The EG(n)-attached PAMAM surfaces with n = 3 reduced the adsorption of fibrinogen to approximately 20% monolayer, whereas 2-3% for n = 4 or 6. The dendrimer films with various densities of EG(n) molecules on PAMAM surfaces were prepared by immersion of the NHS-terminated MUA-functionalized gold substrates in ethanolic solutions containing PAMAM and NHS-EG(n) of various mole ratios. The density (r) of the EG(n) molecules on the PAMAM surfaces is consistent with the mole ratio (r') of NHS-EG(n)/free amine of PAMAM in solutions. The resistance to protein adsorption of the resulting surfaces is correlated with the surface density and the length of the EG chains. At their respective r, the EG(n)-modified dendrimer films resisted approximately 95% adsorption of fibrinogen on gold surfaces. Finally, the specific binding of avidin to the approximately 5% and approximately 40% biotinylated EG3 dendrimers (surface density of biotin with respect to the total number of terminal amino groups on PAMAM G5) gave rise to about 50% and 100% surface coverage by avidin, respectively.

Bioluminescent quantum dots.
Evanko D.
Nat Methods. 2006 Apr;3(4):240-1.
[ expand abstract ]

Bioluminescence is widely used for in vivo imaging of nude mice. By conjugating luciferase protein to quantum dots, bioluminescence resonance energy transfer (BRET) turns these useful fluorophores into a new class of bioluminescent probe.

Investigations into the physicochemical properties of dextran small particulate gadolinium oxide nanoparticles.
McDonald MA, Watkin KL.
Acad Radiol. 2006 Apr;13(4):421-7.
[ expand abstract ]

RATIONALE AND OBJECTIVES: Relatively few studies involving the physicochemical properties of crystalline, nanometer-sized particulate gadolinium complexes have been reported. This is in part because of the challenges associated with making nanoparticulate gadolinium suspensions that are stable in aqueous solution. Small particulate gadolinium oxide (SPGO) and SPGO embedded in albumin microspheres (gadolinium oxide albumin microspheres, GOAM), have been used experimentally as prototype contrast agents for multimodality imaging. MATERIALS AND METHODS: In the present study, an initial attempt was made to better solubilize SPGO, prevent particle aggregation, and investigate the physicochemical properties of dextran SPGO relevant to its use as a high-field magnetic resonance contrast agent in aqueous solution. RESULTS: Dextran SPGO demonstrates regular crystalline lattices and has a gadolinium oxide electron diffraction pattern consistent with that of published X-ray powder diffraction (XPD) patterns. The subtraction XPD pattern of dextran SPGO shows diffraction angles and intensities similar, but not identical, to that of published Gd(2)O(3) diffraction patterns. High r(2)/r(1) ratios and magnetic susceptibility studies indicate dextran SPGO can be classified as a superparamagnetic compound. Enhanced relaxivity is observed at high magnetic field strength; largely because of solubilization of SPGO via the surface adherent carbohydrate. Perhaps also contributing to the observed relaxivity enhancement is the ideal lattice structure of the central gadolinium oxide crystal and the effects of sonochemical preparation on nanoparticle physicochemical properties. CONCLUSIONS: It is anticipated that these studies will help provide a basis for the development of novel nanoparticulate contrast agent platforms capable of improving T(1) and T(2)/T(2)() contrast for high-field magnetic resonance imaging and molecular imaging.

Thermooptical properties of gold nanoparticles embedded in ice: characterization of heat generation and melting.
Richardson HH, Hickman ZN, Govorov AO, Thomas AC, Zhang W, Kordesch ME.
Nano Lett. 2006 Apr;6(4):783-8.
[ expand abstract ]

We investigate the system of optically excited gold NPs in an ice matrix aiming to understand heat generation and melting processes at the nanoscale level. Along with the traditional fluorescence method, we introduce thermooptical spectroscopy based on phase transformation of a matrix. With this, we can not only measure optical response but also thermal response, that is, heat generation. After several recrystallization cycles, the nanoparticles are embedded into the ice film where the optical and thermal properties of the nanoparticles are probed. Spatial fluorescence mapping shows the locations of Au nanoparticles, whereas the time-resolved Raman signal of ice reveals the melting process. From the time-dependent Raman signals, we determine the critical light intensities at which the laser beam is able to melt ice around the nanoparticles. The melting intensity depends strongly on temperature and position. The position-dependence is especially strong and reflects a mesoscopic character of heat generation. We think that it comes from the fact that nanoparticles form small complexes of different geometry and each complex has a unique thermal response. Theoretical calculations and experimental data are combined to make a quantitative measure of the amount of heat generated by optically excited Au nanoparticles and agglomerates. The information obtained in this study can be used to design nanoscale heaters and actuators.

Nano Fountain Pen Manufacture of Polymer Lenses for Nano-biochip Applications.
Sokuler M, Gheber LA.
Nano Lett. 2006 Apr;6(4):848-53.
[ expand abstract ]

Polymer microlenses have been manufactured by delivering droplets of a monomer mixture to a glass substrate using a nano fountain pen (NFP). Subsequent UV polymerization yielded microlenses with optical properties that were controlled by varying the deposition time of the monomer solution. Using this approach, it is possible to strategically place single microlenses at predefined positions with very high accuracy, an ability which may prove very useful for nano-biochip applications, as demonstrated.

Nanorice: a hybrid plasmonic nanostructure.
Wang H, Brandl DW, Le F, Nordlander P, Halas NJ.
Nano Lett. 2006 Apr;6(4):827-32.
[ expand abstract ]

We have designed and fabricated a new hybrid nanoparticle that combines the intense local fields of nanorods with the highly tunable plasmon resonances of nanoshells. This dielectric core-metallic shell prolate spheroid nanoparticle bears a remarkable resemblance to a grain of rice, inspiring the name "nanorice". This geometry possesses far greater structural tunability than either a nanorod or a nanoshell, along with much larger local field intensity enhancements and far greater sensitivity as a surface plasmon resonance (SPR) nanosensor than any dielectric-metal nanostructures reported previously. Invoking the plasmon hybridization picture allows us to understand the plasmon resonances of this geometry, as arising from a hybridization of the primitive plasmons of a solid spheroid and an ellipsoidal cavity inside a continuous metal.

Biosensors based on carbon nanotubes.
Balasubramanian K, Burghard M.
Anal Bioanal Chem. 2006 Mar 28; [Epub ahead of print] .
[ expand abstract ]

Carbon nanotubes (CNTs) exhibit a unique combination of excellent mechanical, electrical and electrochemical properties, which has stimulated increasing interest in the application of CNTs as components in (bio)sensors. This review highlights various design methodologies for CNT-based biosensors and their employment for the detection of a number of biomolecules. In addition, recent developments in the fields of CNT-based chemiresistors and chemically sensitive field-effect transistors are presented. After a critical discussion of the factors that currently limit the practical use of CNT-based biosensors, the review concludes with an outline of potential future applications for CNTs in biology and medicine.

Nanoparticle Targeting at Cells.
de la Fuente JM, Berry CC, Riehle MO, Curtis AS.
Langmuir. 2006 Mar 28;22(7):3286-3293.
[ expand abstract ]

Gold nanoparticles have been used for analytical and biomedical purposes for many years. In fact, the labeling of targeting molecules with nanoparticles has revolutionized the visualization of cellular or tissue components by electron microscopy. We report in this study the derivatization of tiopronin-protected nanoparticles with ethylenediamine and poly(ethylene glycol) bis(3-aminopropyl) terminated and their functionalization with the GRGDSP peptide sequence by a straightforward and economical methodology. The particles were subsequently tested in vitro with a human fibroblast cell line to determine the biocompatibility, and the cell-particle interactions, using fluorescence and scanning electron microscopies. The results indicate that tiopronin gold nanoparticles aggregate due to culture medium proteins, whereas the tiopronin gold nanoparticles derivatized with ethylenediamine induce endocytosis, and the same nanoparticles derivatized with poly(ethylene glycol) derivative promote particle-cell adhesion.

Collection, focusing, and metering of DNA in microchannels using addressable electrode arrays for portable low-power bioanalysis.
Shaikh FA, Ugaz VM.
Proc Natl Acad Sci USA. 2006 Mar 28;103(13):4825-30; [Epub 2006 Mar 21].
[ expand abstract ]

Although advances in microfluidic technology have enabled increasingly sophisticated biosensing and bioassay operations to be performed at the microscale, many of these applications employ such small amounts of charged biomolecules (DNA, proteins, and peptides) that they must first be preconcentrated to a detectable level. Efficient strategies for precisely handling minute quantities of biomolecules in microchannel geometries are critically needed; however, it has proven challenging to achieve simultaneous concentration, focusing, and metering capabilities with current-generation sample-injection technology. By using microfluidic chips incorporating arrays of individually addressable microfabricated electrodes, we demonstrate that DNA can be sequentially concentrated, focused into a narrow zone, metered, and injected into an analysis channel. This technique transports charged biomolecules between active electrodes upon application of a small potential difference (1 V) and is capable of achieving orders of magnitude concentration increases within a small device footprint. The collected samples are highly focused, with sample zone size and shape defined solely by electrode geometry.

Ultrafast enzyme immobilization over large-pore nanoscale mesoporous silica particles.
Sun J, Zhang H, Tian R, Ma D, Bao X, Su DS, Zou H.
Chem Commun (Camb). 2006 Mar 28;(12):1322-4; [Epub 2006 Feb 16].
[ expand abstract ]

By finely tuning the TEOS/P123 molar ratio of the octane/water/P123/TEOS quadruple emulsion system and by controlling the synthesis conditions, an ultrafine emulsion system was isolated, under the confinement of which, nanoscale silica particles with ordered large mesopores ( approximately 13 nm) have been successfully constructed; the obtained mesoporous silica particles have an unusual ultrafast enzyme adsorption speed and the amount of enzyme that can be immobilized is larger than that of conventional mesoporous silica, which has potential applications in the fast separation of biomolecules.

Preparation and encapsulation of highly fluorescent conjugated polymer nanoparticles.
Wu C, Szymanski C, McNeill J.
Langmuir. 2006 Mar 28;22(7):2956-60.
[ expand abstract ]

A facile method has been developed to prepare aqueous dispersions of encapsulated conjugated polymer nanoparticles exhibiting high fluorescence brightness. Salient features of the nanoparticles include their small diameter and spherical morphology. Encapsulation of the nanoparticles with a silica shell reduces the rate of photooxidation and allows facile attachment of functional groups for subsequent bioconjugation and nanoparticle assembly. Functionalization of the nanoparticle with amine groups followed by the addition of Au nanoparticles resulted in the formation of nanoparticle assemblies, as evidenced by the efficient quenching of the conjugated polymer fluorescence by the Au nanoparticles.

Synthesis of ultrafine Gd2O3 nanoparticles inside single-wall carbon nanohorns.
Miyawaki J, Yudasaka M, Imai H, Yorimitsu H, Isobe H, Nakamura E, Iijima S.
J Phys Chem B Condens Matter Mater Surf Interfaces Biophys. 2006 Mar 23;110(11):5179-81.
[ expand abstract ]

The large diameter of single-wall carbon nanohorns (SWNHs) allows various molecules to be easily incorporated in hollow nanospaces. In this report, we prove that the nanospaces of SWNHs even work as the chemical reaction field at high temperature; that is, Gd-acetate clusters inside SWNHs were transformed into ultrafine Gd(2)O(3) nanoparticles with their particle size retained even after heat-treatment at 700 degrees C. This indicates that the confinement of the Gd-acetate clusters in a deep potential well of the SWNH nanospaces prevented a migration to form larger particles, giving rise to ultrafine Gd(2)O(3) nanoparticles of 2.3 nm in average diameter, which is much smaller than the case without SWNHs. The Gd(2)O(3) nanoparticles thus obtained were demonstrated to be actually useful to the magnetic resonance imaging. We believe that the presented effectiveness of the inner hollow spaces of SWNHs, therefore, also those of the carbon nanotubes, for high-temperature chemical reactions should be highlighted, and that the thus produced novel nanomaterials are promising to expand the fields of nanoscience.

Silica-coated CdTe quantum dots functionalized with thiols for bioconjugation to IgG proteins.
Wolcott A, Gerion D, Visconte M, Sun J, Schwartzberg A, Chen S, Zhang JZ.
J Phys Chem B Condens Matter Mater Surf Interfaces Biophys. 2006 Mar 23;110(11):5779-89.
[ expand abstract ]

Quantum dots (QDs) have been increasingly used in biolabeling recently as their advantages over molecular fluorophores have become clear. For bioapplications QDs must be water-soluble and buffer stable, making their synthesis challenging and time-consuming. A simple aqueous synthesis of silica-capped, highly fluorescent CdTe quantum dots has been developed. CdTe QDs are advantageous as the emission can be tuned to the near-infrared where tissue absorption is at a minimum, while the silica shell can prevent the leakage of toxic Cd(2+) and provide a surface for easy conjugation to biomolecules such as proteins. The presence of a silica shell of 2-5 nm in thickness has been confirmed by transmission electron microscopy and atomic force microscopy measurements. Photoluminescence studies show that the silica shell results in greatly increased photostability in Tris-borate-ethylenediaminetetraacetate and phosphate-buffered saline buffers. To further improve their biocompatibility, the silica-capped QDs have been functionalized with poly(ethylene glycol) and thiol-terminated biolinkers. Through the use of these linkers, antibody proteins were successfully conjugated as confirmed by agarose gel electrophoresis. Streptavidin-maleimide and biotinylated polystyrene microbeads confirmed the bioactivity and conjugation specificity of the thiolated QDs. These functionalized, silica-capped QDs are ideal labels, easily synthesized, robust, safe, and readily conjugated to biomolecules while maintaining bioactivity. They are potentially useful for a number of applications in biolabeling and imaging.

MOSFET-Embedded microcantilevers for measuring deflection in biomolecular sensors.
Shekhawat G, Tark SH, Dravid VP.
Science. 2006 Mar 17;311(5767):1592-5; [Epub 2006 Feb 2].
[ expand abstract ]

A promising approach for detecting biomolecules follows their binding to immobilized probe molecules on microfabricated cantilevers; binding causes surface stresses that bend the cantilever. We measured this deflection, which is on the order of tens of nanometers, by embedding a metal-oxide semiconductor field-effect transistor (MOSFET) into the base of the cantilever and recording decreases in drain current with deflections as small as 5 nanometers. The gate region of the MOSFET responds to surface stresses and thus is embedded in silicon nitride so as to avoid direct contact with the sample solution. This approach, which offers low noise, high sensitivity, and direct readout, was used to detect specific binding events with biotin and antibodies.

Fully integrated miniature device for automated gene expression DNA microarray processing.
Liu RH, Nguyen T, Schwarzkopf K, Fuji HS, Petrova A, Siuda T, Peyvan K, Bizak M, Danley D, McShea A.
Anal Chem. 2006 Mar 15;78(6):1980-6.
[ expand abstract ]

A DNA microarray with 12,000 features was integrated with a microfluidic cartridge to automate the fluidic handling steps required to carry out a gene expression study of the human leukemia cell line (K562). The fully integrated microfluidic device consists of microfluidic pumps/mixers, fluid channels, reagent chambers, and a DNA microarray silicon chip. Microarray hybridization and subsequent fluidic handling and reactions (including a number of washing and labeling steps) were performed in this fully automated and miniature device before fluorescent image scanning of the microarray chip. Electrochemical micropumps were integrated into the cartridge to provide pumping of liquid solutions. The device was completely self-contained: no external pressure sources, fluid storage, mechanical pumps, mixers, or valves were necessary for fluid manipulation, thus eliminating possible sample contamination and simplifying device operation. Fluidic experiments were performed to study the on-chip washing efficiency and uniformity. A single-color transcriptional analysis of K562 cells with a series of calibration controls (spiked-in controls) to characterize this new platform with regard to sensitivity, specificity, and dynamic range was performed. The device detected sample RNAs with a concentration as low as 0.375 pM. Experiment also showed that the performance of the integrated microfluidic device is comparable with the conventional hybridization chambers with manual operations, indicating that the on-chip fluidic handling (washing and reaction) is highly efficient and can be automated with no loss of performance. The device provides a cost-effective solution to eliminate labor-intensive and time-consuming fluidic handling steps in genomic analysis.

A microfluidic device for kinetic optimization of protein crystallization and in situ structure determination.
Hansen CL, Classen S, Berger JM, Quake SR.
J Am Chem Soc. 2006 Mar 15;128(10):3142-3.
[ expand abstract ]

The unprecedented economies of scale and unique mass transport properties of microfluidic devices made them viable nano-volume protein crystallization screening platforms. However, realizing the full potential of microfluidic crystallization requires complementary technologies for crystal optimization and harvesting. In this paper, we report a microfluidic device which provides a link between chip-based nanoliter volume crystallization screening and structure analysis through "kinetic optimization" of crystallization reactions and in situ structure determination. Kinetic optimization through systematic variation of reactor geometry and actuation of micromechanical valves is used to screen a large ensemble of kinetic trajectories that are not practical with conventional techniques. Using this device, we demonstrate control over crystal quality, reliable scale-up from nanoliter volume reactions, facile harvesting and cryoprotectant screening, and protein structure determination at atomic resolution from data collected in-chip.

Back to Top

Rapid Purification and Size Separation of Gold Nanoparticles via Diafiltration.
Sweeney SF, Woehrle GH, Hutchison JE.
J Am Chem Soc. 2006 Mar 15;128(10):3190-7.
[ expand abstract ]

Purification and size-based separation of nanoparticles remain significant challenges in the preparation of well-defined materials for fundamental studies and applications. Diafiltration shows considerable potential for the efficient and convenient purification and size separation of water-soluble nanoparticles, allowing for the removal of small-molecule impurities and for the isolation of small nanoparticles from larger nanostructures in a single process. Herein, we report studies aimed at assessing the suitability of diafiltration for (i) the purification of water-soluble thiol-stabilized 3-nm gold nanoparticles, (ii) the separation of a bimodal distribution of nanoparticles into the corresponding fractions, and (iii) the separation of a polydisperse sample into fractions of differing mean core diameter. NMR, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) measurements demonstrate that diafiltration produces nanoparticles with a much higher degree of purity than is possible by dialysis or a combination of solvent washes, chromatography, and ultracentrifugation. UV-visible spectroscopic and transmission electron microscopic (TEM) analyses show that diafiltration offers the ability to separate nanoparticles of disparate core size. These results demonstrate the applicability of diafiltration for the rapid and green preparation of high-purity gold nanoparticle samples and the size separation of heterogeneous nanoparticle samples. They also suggest the development of novel diafiltration membranes specifically suited to high-resolution nanoparticle size separation.

Metal Nanoshells.
Hirsch LR, Gobin AM, Lowery AR, Tam F, Drezek RA, Halas NJ, West JL.
Ann Biomed Eng. 2006 Mar 10; [Epub ahead of print].
[ expand abstract ]

Metal nanoshells are a new class of nanoparticles with highly tunable optical properties. Metal nanoshells consist of a dielectric core nanoparticle such as silica surrounded by an ultrathin metal shell, often composed of gold for biomedical applications. Depending on the size and composition of each layer of the nanoshell, particles can be designed to either absorb or scatter light over much of the visible and infrared regions of the electromagnetic spectrum, including the near infrared region where penetration of light through tissue is maximal. These particles are also effective substrates for surface-enhanced Raman scattering (SERS) and are easily conjugated to antibodies and other biomolecules. One can envision a myriad of potential applications of such tunable particles. Several potential biomedical applications are under development, including immunoassays, modulated drug delivery, photothermal cancer therapy, and imaging contrast agents.

Back to Top

Molecular Dynamics Studies of the Size, Shape, and Internal Structure of 0% and 90% Acetylated Fifth-Generation Polyamidoamine Dendrimers in Water and Methanol.
Lee H, Baker JR Jr, Larson RG.
J Phys Chem B Condens Matter Mater Surf Interfaces Biophys. 2006 Mar 9;110(9):4014-4019.
[ expand abstract ]

We have performed molecular dynamics simulations of 0% and 90% acetylated fifth-generation (G5) polyamidoamine (PAMAM) dendrimers in water and methanol and obtained radii of gyration of 2.51-2.57 and 2.11-2.33 nm, respectively, similar to those measured experimentally in methanol by Prosa et al. (J. Polym. Sci. 1997, 35, 2913-2924) and in water by Choi et al. (Nano Lett. 2004, 4, 391-397). Calculation of the moments of inertia and the relative shape anisotropy show that both 0% and 90% acetylated G5 are modestly ellipsoidal. The distribution of branch points relative to the center of the dendrimer and penetration of solvent show that the core and surface of the dendrimer are more exposed to water than is the region between the core and the surface due to the interactions between monomers, including hydrogen bonds that rapidly break and re-form as solvent molecules compete for hydrogen-bonding sites on the monomers. The water and methanol solvents seem to produce similar numbers of hydrogen bond interactions between monomers.

Methods for Fabrication of Nanoscale Topography for Tissue Engineering Scaffolds.
Norman JJ, Desai TA.
Ann Biomed Eng. 2006 Mar 9; [Epub ahead of print].
[ expand abstract ]

Observations of how controlling the microenvironment of cell cultures can lead to changes in a variety of parameters has lead investigators to begin studying how the nanoenvironment of a culture can affects cells. Cells have many structures at the nanoscale such as filipodia and cytoskeletal and membrane proteins that interact with the environment surrounding them. By using techniques that can control the nanoenvironment presented to a cell, investigators are beginning to be able to mimic the nanoscale topographical features presented to cells by extracellular matrix proteins such as collagen, which has precise and repeating nanotopography. The belief is that these nanoscale surface features are important to creating more natural cell growth and function. A number of techniques are currently being used to create nanoscale topographies for cell scaffolding. These techniques fall into two main categories: techniques that create ordered topographies and those that create unordered topographies. Electron Beam lithography and photolithograpghy are two standard techniques for creating ordered features. Polymer demixing, phase separation, colloidal lithography and chemical etching are most typically used for creating unordered surface patterns. This review will give an overview of these techniques and cite observations from experiments carried out using them.

Back to Top

pH-Sensitive Quantum Dots.
Tomasulo M, Yildiz I, Raymo FM.
J Phys Chem B Condens Matter Mater Surf Interfaces Biophys. 2006 Mar 9;110(9):3853-5.
[ expand abstract ]

We have designed organic ligands able to adsorb on the surface of CdSe-ZnS core-shell quantum dots and switch the luminescence of the inorganic nanoparticles in response to hydroxide anions. These compounds incorporate a [1,3]oxazine ring within their molecular skeleton, which reacts with the nucleophilic hydroxide anion to generate a 4-nitrophenylazophenolate chromophore. The chromogenic transformation activates an energy transfer pathway from the quantum dot to the adsorbed chromophores. As a result, the luminescence intensity of the coated nanoparticles decreases significantly in the presence of hydroxide anions. In fact, this mechanism can be exploited to probe the pH of aqueous solutions. Indeed, an increase in pH from 7.1 to 8.5 translates into a 35% decrease in the luminescence intensity of the sensitive quantum dots. Thus, our operating principles for luminescence switching can efficiently transduce a chemical stimulation into a change in the emissive response of semiconductor nanoparticles. In principle, this protocol can be extended from hydroxide anions to other target analytes with appropriate adjustments in the molecular design of the chromogenic ligands. It follows that luminescent chemosensors, based on the unique photophysical properties of semiconductor quantum dots, can eventually evolve from our design logic and choice of materials.

Myotube Assembly on Nanofibrous and Micropatterned Polymers.
Huang NF, Patel S, Thakar RG, Wu J, Hsiao BS, Chu B, Lee RJ, Li S.
Nano Lett. 2006 Mar 8;6(3):537-542.
[ expand abstract ]

Skeletal muscle consists of parallel bundles of myotubes formed by the fusion of myoblasts. We fabricated nanofibrous and micropatterned polymers as cell culture substrates to guide the morphogenesis of muscular tissue. The nanoscale and microscale topographic features regulate cell and cytoskeleton alignment, myotube assembly, myotube striation, and myoblast proliferation. This bottom-up approach from nanoscale to tissue level demonstrates the potential of nanofibrous polymers for engineering the assembly of cell and tissue structure.

Back to Top

Chemistry of Carbon Nanotubes.
Tasis D, Tagmatarchis N, Bianco A, Prato M.
Chem Rev. 2006 Mar 8;106(3):1105-1136.
[ expand abstract ]

No abstract available

Microgram-scale testing of reaction conditions in solution using nanoliter plugs in microfluidics with detection by MALDI-MS.
Hatakeyama T, Chen DL, Ismagilov RF.
J Am Chem Soc. 2006 Mar 1;128(8):2518-9.
[ expand abstract ]

No abstract available

Back to Top

A simple, valveless microfluidic sample preparation device for extraction and amplification of DNA from nanoliter-volume samples.
Legendre LA, Bienvenue JM, Roper MG, Ferrance JP, Landers JP.
Anal Chem. 2006 Mar 1;78(5):1444-51.
[ expand abstract ]

A glass microdevice has been constructed for the on-line integration of solid-phase extraction (SPE) of DNA and polymerase chain reaction (PCR) on a single chip. The chromatography required for SPE in the microfluidic sample preparation device (muSPD) was carried out in a silica bead/sol-gel SPE bed, where the purified DNA was eluted directly into a downstream chamber where conventional thermocycling allowed for PCR amplification of specific DNA target sequences. Through rapid, simple passivation of the PCR chamber with a silanizing reagent, reproducible DNA extraction and amplification was demonstrated from complex biological matrixes in a manner amenable to any research laboratory, using only a syringe pump and a conventional thermocycler. The muSPD allowed for SPE concentration of DNA from 600 nL of blood coupled to subsequent on-chip amplification that yielded a detectable amplicon; this simple device can be applied to a variety of routine genetic analyses without the need for sophisticated instrumentation. In addition, the applicability of these developments to nonconventional thermocycling was demonstrated through the use of noncontact, IR-mediated heating. This was exemplified with the isolation of DNA from an anthrax spore-spiked nasal swab and the subsequent on-chip amplification of target DNA sequences in a total processing time of only 25 min.

Lab-on-a-chip: microfluidics in drug discovery.
Dittrich PS, Manz A.
Nat Rev Drug Discov. 2006 Mar;5(3):210-8.
[ expand abstract ]

Miniaturization can expand the capability of existing bioassays, separation technologies and chemical synthesis techniques. Although a reduction in size to the micrometre scale will usually not change the nature of molecular reactions, laws of scale for surface per volume, molecular diffusion and heat transport enable dramatic increases in throughput. Besides the many microwell-plate- or bead-based methods, microfluidic chips have been widely used to provide small volumes and fluid connections and could eventually outperform conventionally used robotic fluid handling. Moreover, completely novel applications without a macroscopic equivalent have recently been developed. This article reviews current and future applications of microfluidics and highlights the potential of 'lab-on-a-chip' technology for drug discovery.

Back to Top

Microfluidic technology for PET radiochemistry.
Gillies JM, Prenant C, Chimon GN, Smethurst GJ, Dekker BA, Zweit J.
Appl Radiat Isot. 2006 Mar;64(3):333-6.
[ expand abstract ]

This paper describes the first application of a microfabricated reaction system to positron emission tomography (PET) radiochemistry. We have applied microfluidic technology to synthesise PET radiopharmaceuticals using (18)F and (124)I as labels for fluorodeoxyglucose (FDG) and Annexin-V, respectively. These reactions involved established methods of nucleophilic substitution on a mannose triflate precursor and direct iodination of the protein using iodogen as an oxidant. This has demonstrated a proof of principle of using microfluidic technology to radiochemical reactions involving low and high molecular weight compounds. Using microfluidic reactions, [(18)F]FDG was synthesised with a 50% incorporation of the available F-18 radioactivity in a very short time of 4s. The radiolabelling efficiency of (124)I Annexin-V was 40% after 1min reaction time. Chromatographic analysis showed that such reaction yields are comparable to conventional methods, but in a much shorter time. The yields can be further improved with more optimisation of the microfluidic device itself and its fluid mixing profiles. This demonstrates the potential for this technology to have an impact on rapid and simpler radiopharmaceutical synthesis using short and medium half-life radionuclides.

Microfluidic reactor for the radiosynthesis of PET radiotracers.
Gillies JM, Prenant C, Chimon GN, Smethurst GJ, Perrie W, Hamblett I, Dekker B, Zweit J.
Appl Radiat Isot. 2006 Mar;64(3):325-32.
[ expand abstract ]

Here we show the first application of a microfabricated reaction system to PET radiochemistry, we term "microfluidic PET". The short half-life of the positron emitting isotopes and the trace chemical quantities used in radiolabelling make PET radiochemistry amenable to miniaturisation. Microfluidic technologies are capable of controlling and transferring tiny quantities of liquids which allow chemical and biochemical assays to be integrated and carried out on a small scale. Such technologies provide distinct advantages over current methods of PET radiochemical synthesis. To demonstrate "proof of principle" we have investigated the radiohalogenation of small and large molecular weight molecules using the microfluidic device. These reactions involved the direct radioiodination of the apoptosis marker Annexin V using iodine-124, the indirect radioiodination of the anti-cancer drug doxorubicin from a tin-butyl precursor and the radiosynthesis of 2-[(18)F]FDG from a mannose triflate precursor and fluorine-18 and hence provide a test bed for microfluidic reactions. We demonstrate the rapid radioiodination of the protein Annexin V (40% radiochemical yield within 1min) and the rapid radiofluorination of 2-[(18)F]FDG (60% radiochemical yield within 4s) using a polymer microreactor chip. Chromatographic analysis showed that the labelling efficiency of the unoptimised microfluidic chip is comparable to conventional PET radiolabelling reactions.

Back to Top

Dendrimers: novel polymeric nanoarchitectures for solubility enhancement.
Gupta U, Agashe HB, Asthana A, Jain NK.
Biomacromolecules. 2006 Mar;7(3):649-58.
[ expand abstract ]

Poor solubility and hydrophobicity of drugs/bioactives limit their possible applications in drug delivery and formulation development. Apart from conventional methods of solubility enhancement, there are some novel methods which can be used in solubilization. Dendrimers represent a novel type of polymeric material that has generated much interest in many diverse areas due to their unique structure and properties. Dendrimer-mediated solubility enhancement mainly depends on factors such as generation size, dendrimer concentration, pH, core, temperature, and terminal functionality. Added advantage in solubilization can be achieved considering these factors. Available literature suggests that ionic interaction, hydrogen bonding, and hydrophobic interactions are the possible mechanisms by which a dendrimer exerts its solubilizing property. This review presents various mechanisms and reports relating to solubility enhancement using dendrimers. Also, micellar behavior and future possibilities in relation to solubilization via dendrimers are included.

Molecular heterogeneity analysis of poly(amidoamine) dendrimer-based mono- and multifunctional nanodevices by capillary electrophoresis.
Shi X, Majoros IJ, Patri AK, Bi X, Islam MT, Desai A, Ganser TR, Baker JR Jr.
Analyst. 2006 Mar;131(3):374-81.
[ expand abstract ]

Poly(amidoamine) (PAMAM) dendrimer-based nanodevices are of recent interest in targeted cancer therapy. Characterization of mono- and multifunctional PAMAM-based nanodevices remains a great challenge because of their molecular complexity. In this work, various mono- and multifunctional nanodevices based on PAMAM G5 (generation 5) dendrimer were characterized by UV-Vis spectrometry, (1)H NMR, size exclusion chromatography (SEC), and capillary electrophoresis (CE). CE was extensively utilized to measure the molecular heterogeneity of these PAMAM-based nanodevices. G5-FA (FA denotes folic acid) conjugates (synthesized from amine-terminated G5.NH(2) dendrimer, approach 1) with acetamide and amine termini exhibit bimodal or multi-modal distributions. In contrast, G5-FA and bifunctional G5-FA-MTX (MTX denotes methotrexate) conjugates with hydroxyl termini display a single modal distribution. Multifunctional G5.Ac(n)-FI-FA, G5.Ac(n)-FA-OH-MTX, and G5.Ac(n)-FI-FA-OH-MTX (Ac denotes acetamide; FI denotes fluorescein) nanodevices (synthesized from partially acetylated G5 dendrimer, approach 2) exhibit a monodisperse distribution. It indicates that the molecular distribution of PAMAM conjugates largely depends on the homogeneity of starting materials, the synthetic approaches, and the final functionalization steps. Hydroxylation functionalization of dendrimers masks the dispersity of the final PAMAM nanodevices in both synthetic approaches. The applied CE analysis of mono- and multifunctional PAMAM-based nanodevices provides a powerful tool to evaluate the molecular heterogeneity of complex dendrimer conjugate nanodevices for targeted cancer therapeutics.

Back to Top

The kinetics of analyte capture on nanoscale sensors.
Solomon JE, Paul MR.
Biophys J. 2006 Mar;90(5):1842-52.
[ expand abstract ]

This article presents a number of kinetic analyses related to binding processes relevant to capture of target analyte species in nanoscale cantilever-type devices designed to detect small concentrations of biomolecules. The overall analyte capture efficiency is a crucial measure of the ultimate sensitivity of such devices, and a detailed kinetic analysis tells us how rapidly such measurements may be made. We have analyzed the capture kinetics under a variety of conditions, including the possibility of so-called surface-enhanced ligand capture. One of the modalities studied requires ligand capture through a cross-linking mechanism, and it was found that this mode may provide a robust and sensitive approach to biomolecular detection. For the two modalities studied, we find that detection of specific biomolecules down to concentration levels of 1 nM or less appear to be quite feasible for the device configurations studied.

A modular approach to two-photon absorbing organic nanodots: brilliant dendrimers as an alternative to semiconductor quantum dots?
Mongin O, Krishna TR, Werts MH, Caminade AM, Majoral JP, Blanchard-Desce M.
Chem Commun (Camb). 2006 Feb 28;(8):915-7.
[ expand abstract ]

Nanoscopic fluorescent dendrimers having up to 96 two-photon chromophores and showing very large two-photon absorption cross-sections (up to 56 000 GM) were designed as a complementary "organic" alternative to quantum dots.

Back to Top

Diffusion and mathematical modeling of release profiles from nanocarriers.
Cruz L, Soares LU, Costa TD, Mezzalira G, da Silveira NP, Guterres SS, Pohlmann AR.
Int J Pharm. 2006 Feb 23; [Epub ahead of print] .
[ expand abstract ]

The aim of this work was to establish models and to differentiate the kinetic release behavior of drug models from nanocapsules, nanoemulsion and nanospheres by physico-chemical characterization and release experiments. SAXS analysis showed that the polymer is organized in the nanocapsules, while in the nanospheres the sorbitan monostearate is organized and acts as an impurity of the poly(varepsilon-caprolactone) suggesting that constituents in these nanocarriers are differently organized. Formulations presented particle sizes ranging from 178 to 297nm, probe content from 0.981 to 0.997mg/mL, pH values from 4.90 to 5.10 and zeta potential from -37.9 to -51.9mV. The kinetic experiments showed that the nanostructures present similar behaviors when the probe is adsorbed on the nanocarriers (indomethacin-loaded formulations). However, when the probe is entrapped within the nanocarriers (indomethacin ethyl ester-loaded formulations), nanocapsules, nanospheres and nanoemulsion presented different kinetic behaviors. Mathematical modeling of the release profiles was conducted, showing that the presence of the polymer increases the half-lives of the burst phases (5.9, 4.4 and 2.7min) while the presence of the oil increases the half-lives of the sustained phases (288.8, 87.7 and 147.5min) for nanocapsules, nanospheres and nanoemulsion, respectively.

DNA nano-carriers from biodegradable cationic branched polyesters are formed by a modified solvent displacement method.
Oster CG, Wittmar M, Bakowsky U, Kissel T.
J Control Release. 2006 Feb 22; [Epub ahead of print] .
[ expand abstract ]

DNA nano-carriers were formulated relying on biodegradable polyesters consisting of amine-modified poly(vinyl alcohol) (PVAL) backbones grafted with PLGA, based on the Marangoni effect thus avoiding detrimental shear or ultrasonic forces. These amine modified high molecular weight biodegradable polyesters combine specific characteristics, such as electrostatic interactions between DNA and cationic branched polyesters facilitating loading of NP with DNA. The resulting DNA containing NP showed hydrodynamic diameters in the range of 175-285 nm and highly positive xi-potentials, depending on the nitrogen to phosphate (N/P) ratio used for the particle formation. Atomic force microscopy (AFM) demonstrated well-defined spherical particle morphologies. DNA was released from NP upon incubation in PBS buffer in its intact supercoiled form. Agarose gel electrophoresis demonstrated that DNA within the NP was protected from enzyme degradation. The biological efficiency of the DNA delivery by this nano-carrier was demonstrated by an in vitro transfection assay using four cell lines. Reporter gene delivery of the amine-modified polymers was higher than naked DNA (Control) and raised with increasing degree of amine substitution. Also type of amine and distance of cationic charge from the backbone play an important role. Further, this feature was shown by Luciferase expression of the pCMV-Luc plasmid with PEI 25 kDa/DNA polyplexes and NP prepared with amine modified polyesters with a grafted PLGA chain length of 10 monomers compared at equal N/P ratios. DNA loaded NP from P(68)-10 showed 8x higher transfection efficiencies than the PEI 25 kDa at an N/P ratio of 9 for both preparations. These novel DNA nano-carriers merit further investigations in particular for DNA vaccination under in vivo conditions.

Back to Top

Nanoparticles as targeting ligands.
Jain KK.
Trends Biotechnol. 2006 Feb 16; [Epub ahead of print] .
[ expand abstract ]

A recently published technique enables the attachment of small molecules to nanoparticles for improved targeting of nanomaterials. This new methodology has been compared with some of the other nanoparticle-based techniques for target discovery and found to be more versatile and specific. This approach has potential for high-throughput drug discovery, improved drug delivery and linking of diagnostics to therapeutics for the development of personalized medicines.

Iridium-complex modified CdSe/ZnS quantum dots; a conceptual design for bi-functionality toward imaging and photosensitization.
Hsieh JM, Ho ML, Wu PW, Chou PT, Tsai TT, Chi Y.
Chem Commun (Camb). 2006 Feb 14;(6):615-7.
[ expand abstract ]

We report the design and synthesis of Ir-complex functionalized CdSe/ZnS quantum dots (QDs), in which the QD plays a key role in imaging, while the Ir-complex acts as a sensitizer to produce singlet oxygen; this conceptual design presents a novel scheme in both bio-imaging and photodynamic therapy.

Back to Top

Comparative Examination of the Stability of Semiconductor Quantum Dots in Various Biochemical Buffers.
Boldt K, Bruns OT, Gaponik N, Eychmuller A.
Phys Chem B Condens Matter Mater Surf Interfaces Biophys. 2006 Feb 9;110(5):1959-1963.
[ expand abstract ]

Due to their greater photostability compared to established organic fluorescence markers, semiconductor quantum dots provide an attractive alternative for the biolabeling of living cells. On the basis of a comparative investigation using differently sized thiol-stabilized CdTe nanocrystals in a variety of commonly used biological buffers, a method is developed to quantify the stability of such a multicomponent system. Above a certain critical size, the intensity of the photoluminescence of the nanocrystals is found to diminish with pseudo-zero-order kinetics, whereas for specific combinations of particle size, ligand, and buffer there appears to be no decay below this critical particle size, pointing out the necessity for thorough investigations of this kind in the view of prospect applications of semiconductor nanocrystals in the area of biolabeling.

Degradation of Protein in Nanoplasma Generated around Gold Nanoparticles in Solution by Laser Irradiation.
Takeda Y, Kondow T, Mafune F.
J Phys Chem B Condens Matter Mater Surf Interfaces Biophys. 2006 Feb 9;110(5):2393-7.
[ expand abstract ]

We developed a method of protein degradation in an aqueous solution containing gold nanoparticles by irradiation of a pulse laser. In the present study, lysozyme was used as an example. Lysozyme degradation proceeded most efficiently when a pH of the solution was adjusted so that it was at the isoelectric point. The scheme of the lysozyme degradation is as follows: (1) Lysozyme molecules in the solution are neutralized and adsorbed on the gold nanoparticles with its pH value adjusted at the isoelectric point, (2) nanoplasma is generated in the close vicinity of a gold nanoparticle which is excited by an intense 532-nm laser, (3) lysozyme molecules in the nanoplasma are degraded into small fragments. Lysozyme degradation does not proceed efficiently at a pH value deviated from the isoelectric point because the lysozyme molecules are dissolved uniformly so that only a small portion of the lysozyme molecules are located in the vicinity of gold nanoparticles which create the nanoplasma.

Back to Top

Reversible Stimuli-Responsive Nanostructures Assembled from Amphiphilic Block Copolymers.
Xu C, Fu X, Fryd M, Xu S, Wayland BB, Winey KI, Composto RJ.
Nano Lett. 2006 Feb 8;6(2):282-287.
[ expand abstract ]

We present a novel route to assemble perpendicular cylinders by converting an asymmetric diblock copolymer from poly(styrene-b-tert-butyl acrylate) (PS-b-PtBA) to poly(styrene-b-acrylic acid) (PS-b-PAA) using an autocatalytic reaction. Upon exposure of the films of PS-b-PAA to water, PAA cylinders constrained by the continuous, glassy PS phase protrude 10 nm above the surface and swell laterally to form mushroom caps, rendering the entire surface hydrophilic. Upon annealing, the original nanostructures re-form demonstrating reversibility of swelling. Because of their stimuli-responsive behavior, these nanoscale materials are excellent candidates for sensors and microfluidic applications.

Controlling the shape, orientation, and linkage of carbon nanotube features with nano affinity templates.
Wang Y, Maspoch D, Zou S, Schatz GC, Smalley RE, Mirkin CA.
Proc Natl Acad Sci USA. 2006 Feb 6; [Epub ahead of print].
[ expand abstract ]

Directed assembly of nanoscale building blocks such as single-walled carbon nanotubes (SWNTs) into desired architectures is a major hurdle for a broad range of basic research and technological applications (e.g., electronic devices and sensors). Here we demonstrate a parallel assembly process that allows one to simultaneously position, shape, and link SWNTs with sub-100-nm resolution. Our method is based on the observation that SWNTs are strongly attracted to COOH-terminated self-assembled monolayers (COOH-SAMs) and that SWNTs with lengths greater than the dimensions of a COOH-SAM feature will align along the boundary between the COOH-SAM feature and a passivating CH3-terminated SAM. By using nanopatterned affinity templates of 16-mercaptohexadecanonic acid, passivated with 1-octadecanethiol, we have formed SWNT dot, ring, arc, letter, and even more sophisticated structured thin films and continuous ropes. Experiment and theory (Monte Carlo simulations) suggest that the COOH-SAMs localize the solvent carrying the nanotubes on the SAM features, and that van der Waals interactions between the tubes and the COOH-rich feature drive the assembly process. A mathematical relationship describing the geometrically weighted interactions between SWNTs and the two different SAMs required to overcome solvent-SWNT interactions and effect assembly is provided.

Back to Top

Number-concentration of nanoparticles in liposomal and polymeric multiparticulate preparations: empirical and calculation methods.
Epstein H, Afergan E, Moise T, Richter Y, Rudich Y, Golomb G.
Biomaterials. 2006 Feb;27(4):651-9.
[ expand abstract ]

The actual number of particles in formulations of nanoparticles (NP) is of importance for quality assurance, comprehensive physicochemical characterization, and pharmacodynamics. Some calculation methods that have been previously employed are limited because they rely on several assumptions and are not applicable for certain preparations. Currently there are no validated experimental methods for determining the particle number-concentration (Nc) of liposomal and polymeric nanoparticulate preparations (<500 nm). This study examines a new empirical method for counting the number of particles in nanoparticulate formulations including drug-containing liposomes and polymeric NP. In the new method, suspended NP are nebulized to form aerosol droplets which are dried and counted using a scanning mobility particle sizer (SMPS). Experiments were conducted with three different preparations, empty liposomes (200 and 400 nm), drug-loaded liposomes (200 nm), and polymeric NP (150 nm). It was verified that no detrimental morphological or structural changes of the formulations have been induced by the SMPS technique, and that the obtained Nc values represent the original particles. It is concluded that nano-formulations with concentrations of up to 10(7) particles per 1 cm3 air, corresponding to approximately 10(12) particles per 1 ml solution, can be directly counted within the size range of 30-900 nm. The measured values are compared to newly developed theoretical calculations to assess the viability of these calculations.

Mixing with bubbles: a practical technology for use with portable microfluidic devices.
Garstecki P, J Fuerstman M, Fischbach MA, Sia SK, Whitesides GM.
Lab Chip. 2006 Feb;6(2):207-12.
[ expand abstract ]

This paper demonstrates a methodology for micromixing that is sufficiently simple that it can be used in portable microfluidic devices. It illustrates the use of the micromixer by incorporating it into an elementary, portable microfluidic system that includes sample introduction, sample filtration, and valving. This system has the following characteristics: (i) it is powered with a single hand-operated source of vacuum, (ii) it allows samples to be loaded easily by depositing them into prefabricated wells, (iii) the samples are filtered in situ to prevent clogging of the microchannels, (iv) the structure of the channels ensure mixing of the laminar streams by interaction with bubbles of gas introduced into the channels, (v) the device is prepared in a single-step soft-lithographic process, and (vi) the device can be prepared to be resistant to the adsorption of proteins, and can be used with or without surface-active agents.

Back to Top

Sequence-independent helical wrapping of single-walled carbon nanotubes by long genomic DNA.
Gigliotti B, Sakizzie B, Bethune DS, Shelby RM, Cha JN.
Nano Lett. 2006 Feb;6(2):159-64.
[ expand abstract ]

Because of their nanometer sizes and molecular recognition capabilities, biological systems have garnered much attention as vehicles for the directed assembly of nanoscale materials.(1-6) One of the greatest challenges of this research has been to successfully interface biological systems with electronic materials, such as semiconductors and metals. As a means to address some of these issues, Sarikaya, Belcher, and others have used a combinatorial technique called phage display(7-9) to discover new families of peptides that showed binding affinities to various substrates. More recently, Zheng and co-workers used combinatorial DNA libraries to isolate short DNA oligomers (30-90 bases) that could disperse single-walled carbon nanotubes (SWCNT) in water.(10) Through a systematic analysis, they found that short oligonucleotides having repeating sequences of gunanines and thymines (dGdT)(n)() could wrap in a helical manner around a CNT with periodic pitch.(11) Although helix formation around SWCNTs having regular pitches is an effective method for dispersing and separating CNTs, the need for specific repeating sequences limits use to nonnatural DNA that must be synthesized with optimal lengths of less than 150 bases. In contrast, we demonstrate here that long genomic single-stranded DNA (>>100 bases) of a completely random sequence of bases can be used to disperse CNTs efficiently through the single-stranded DNA's (ssDNA) ability to form tight helices around the CNTs with distinct periodic pitches. Although this process occurs irrespective of the DNA sequence, we show that this process is highly dependent on the removal of complementary strands. We also demonstrate that although the helix pitch-to-pitch distances remain constant down the length of a single CNT, the distances are variable from one DNA-CNT to another. Finally, we report initial work that shows that methods developed to align long dsDNA can be applied in a similar fashion to produce highly dense arrays of aligned ssDNA-CNT hybrids.

Microemulsion and diafiltration approaches: An attempt to maximize the global yield of DNA-loaded nanospheres.
Hammady T, Nadeau V, Hildgen P.
Eur J Pharm Biopharm. 2006 Feb;62(2):143-54.
[ expand abstract ]

The yield of DNA-loaded nanospheres in its widest definition includes encapsulation efficiency and the integrity of the loaded molecules plus the production yield of fabricated nanospheres. The former aspect could be considerably improved by adopting the microemulsion concept to enhance the stability of the primary emulsion during the preparation of nanospheres by the double emulsion solvent-removal method. The droplet size of the mentioned emulsion was monitored by means of photon electron correlation spectroscopy and could serve as an index for emulsion fineness and stability. DNA stability as a function of applied mechanical stress was monitored by horizontal agarose gel electrophoresis. The impact of the primary emulsion on nanosphere porosity was assessed as well. Regarding the second aspect of the global yield of nanospheres, i.e. production yield, a modified diafiltration technique was adopted for the washing and recovery processes in comparison with the traditional and for the conservation of particle size characteristics of the recovered nanospheres.

Back to Top

Facile fabrication of microfluidic systems using electron beam lithography.
Mali P, Sarkar A, Lal R.
Lab Chip. 2006 Feb;6(2):310-5.
[ expand abstract ]

We present two fast and generic methods for the fabrication of polymeric microfluidic systems using electron beam lithography: one that employs spatially varying electron-beam energy to expose to different depths a negative electron-beam resist, and another that employs a spatially varying electron-beam dose to differentially expose a bi-layer resist structure. Using these methods, we demonstrate the fabrication of various microfluidic unit structures such as microchannels of a range of geometries and also other more complex structures such as a synthetic gel and a chaotic mixer. These are made without using any separate bonding or sacrificial layer patterning and etching steps. The schemes are inherently simple and scalable, afford high resolution without compromising on speed and allow post CMOS fabrication of microfluidics. We expect them to prove very useful for the rapid prototyping of complete integrated micro/nanofluidic systems with sense and control electronics fabricated by upstream processes.

Complement activation and protein adsorption by carbon nanotubes.
Salvador-Morales C, Flahaut E, Sim E, Sloan J, Green ML, Sim RB.
Mol Immunol. 2006 Feb;43(3):193-201.
[ expand abstract ]

As a first step to validate the use of carbon nanotubes as novel vaccine or drug delivery devices, their interaction with a part of the human immune system, complement, has been explored. Haemolytic assays were conducted to investigate the activation of the human serum complement system via the classical and alternative pathways. Western blot and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) techniques were used to elucidate the mechanism of activation of complement via the classical pathway, and to analyse the interaction of complement and other plasma proteins with carbon nanotubes. We report for the first time that carbon nanotubes activate human complement via both classical and alternative pathways. We conclude that complement activation by nanotubes is consistent with reported adjuvant effects, and might also in various circumstances promote damaging effects of excessive complement activation, such as inflammation and granuloma formation. C1q binds directly to carbon nanotubes. Protein binding to carbon nanotubes is highly selective, since out of the many different proteins in plasma, very few bind to the carbon nanotubes. Fibrinogen and apolipoproteins (AI, AIV and CIII) were the proteins that bound to carbon nanotubes in greatest quantity.

Back to Top

Stable and robust polymer nanotubes stretched from polymersomes.
Reiner JE, Wells JM, Kishore RB, Pfefferkorn C, Helmerson K.
Proc Natl Acad Sci USA. 2006 Jan 31;103(5):1173-7.
[ expand abstract ]

We create long polymer nanotubes by directly pulling on the membrane of polymersomes using either optical tweezers or a micropipette. The polymersomes are composed of amphiphilic diblock copolymers, and the nanotubes formed have an aqueous core connected to the aqueous interior of the polymersome. We stabilize the pulled nanotubes by subsequent chemical cross-linking. The cross-linked nanotubes are extremely robust and can be moved to another medium for use elsewhere. We demonstrate the ability to form networks of polymer nanotubes and polymersomes by optical manipulation. The aqueous core of the polymer nanotubes together with their robust character makes them interesting candidates for nanofluidics and other applications in biotechnology.

Real-time sizing of nanoparticles in microfluidic channels using confocal correlation spectroscopy.
Kuyper CL, Budzinski KL, Lorenz RM, Chiu DT.
J Am Chem Soc. 2006 Jan 25;128(3):730-1.
[ expand abstract ]

No abstract available

Back to Top

Superplastic carbon nanotubes.
Huang JY, Chen S, Wang ZQ, Kempa K, Wang YM, Jo SH, Chen G, Dresselhaus MS, Ren ZF.
Nature. 2006 Jan 19;439(7074):281.
[ expand abstract ]

The theoretical maximum tensile strain--that is, elongation--of a single-walled carbon nanotube is almost 20%, but in practice only 6% is achieved. Here we show that, at high temperatures, individual single-walled carbon nanotubes can undergo superplastic deformation, becoming nearly 280% longer and 15 times narrower before breaking. This superplastic deformation is the result of the nucleation and motion of kinks in the structure, and could prove useful in helping to strengthen and toughen ceramics and other nanocomposites at high temperatures.

Toward the isolation of functional organic nanotubes.
Dalgarno SJ, Cave GW, Atwood JL.
Angew Chem Int Ed Engl. 2006 Jan 16;45(4):570-4.
[ expand abstract ]

No abstract available

Back to Top

Comparative modeling and analysis of microfluidic and conventional DNA microarrays.
Benn JA, Hu J, Hogan BJ, Fry RC, Samson LD, Thorsen T.
Anal Biochem. 2006 Jan 15;348(2):284-93.
[ expand abstract ]

A theoretical analysis was developed to predict molecular hybridization rates for microarrays where samples flow through microfluidic channels and for conventional microarrays where samples remain stationary during hybridization. The theory was validated by using a multiplexed microfluidic microarray where eight samples were hybridized simultaneously against eight probes using 60-mer DNA strands. Mass transfer coefficients ranged over three orders of magnitude where either kinetic reaction rates or molecular diffusion rates controlled overall hybridization rates. Probes were printed using microfluidic channels and also conventional spotting techniques. Consistent with the theoretical model, the microfluidic microarray demonstrated the ability to print DNA probes in less than 1min and to detect 10-pM target concentrations with hybridization times in less than 5min.

Surface modification of magnetic nanoparticles capped by oleic acids: Characterization and colloidal stability in polar solvents.
Lee SY, Harris MT.
J Colloid Interface Sci. 2006 Jan 15;293(2):401-8.
[ expand abstract ]

The lyophobic surface of monodisperse magnetic nanoparticles capped by oleic acid was made to be more lyophilic by ozonolysis to increase the stability of the suspension in polar solvents like ethanol. The ozone oxidatively cleaved the double bond of oleic acid to form carbonyl and carboxyl groups on the surface of the nanoparticles. Additionally, interfacial ligand exchange of the capping molecules was applied to make the hydrophobic particle surface more hydrophilic. The magnetic particles showed enhanced miscibility and short-term stability in water after interfacial ligand exchange. The structure changes of the capping molecules on the nanoparticle surfaces were investigated using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). From these spectroscopy studies, the cleavage of the oleic acid and the formations of the carboxyl and carbonyl groups on the particle surface were confirmed. The shape and the magnetic properties of the nanoparticles were maintained after the surface modification. Ozonolysis is an effective method in modifying the lyophobic surface of the magnetic nanoparticles.

Back to Top

The promise of nanotechnology for separation devices - from a top-down approach to nature-inspired separation devices.
Eijkel JC, van den Berg A.
Electrophoresis. 2006 Jan 9; [Epub ahead of print].
[ expand abstract ]

An overview is given of the possible applications of nanotechnology to optimise existing separation methods and to enable new methods. Attention is paid to nanotechnological contributions in the fields of HPLC, CEC, sieves, Brownian ratchets and preconcentration units. A brief description is also given of some selection/separation mechanisms that occur in biological (cell) structures and possible future applications of these mechanisms in separation devices are investigated. Especially the active transport in discrete events occurring in cells is mentioned as a potentially powerful separating mechanism.

Dendritic supermolecules - towards controllable nanomaterials.
Smith DK.
Chem Commun (Camb). 2006 Jan 7;(1):34-44.
[ expand abstract ]

Dendritic molecules constitute one of the most exciting areas of modern nanochemistry, largely as a consequence of the unique properties associated with their branched architectures. This article describes how 'dendritic function' can also be achieved using small, synthetically accessible branched building blocks (individual dendrons) which simply self-assemble via non-covalent interactions to generate dendritic nanoscale architectures with novel behaviour. (a) Using non-covalent interactions at the focal point of a dendron allows the self-assembly of nanometre-sized supramolecular dendrimers around an appropriate template species. Such systems have potential applications in the controlled encapsulation and release of active ingredients. (b) Employing non-covalent intermolecular dendron-dendron interactions can give rise to the hierarchical assembly of nanostructured materials. Such assemblies of dendritic molecules ultimately express their molecular scale information on a macroscopic scale, and therefore have applications in materials science, for example as gels. (c) The multiple surface groups of dendrons are capable of forming multiple interactions with large surfaces, such as those found on biomolecules or in biological systems. Employing multivalent interactions between dendron surfaces and biological molecules opens up the potential application of dendritic systems as medicinal therapies. In summary, dendritic supermolecules offer a potentially cost-effective approach to the future application of dendritic systems to a range of real-world problems.

Is nanotechnology ready for primetime?
Brower V.
J Natl Cancer Inst. 2006 Jan 4;98(1):9-11.
[ expand abstract ]

No abstract available

Back to Top

Fabrication of fluorescent nanotubes based on layer-by-layer assembly via covalent bond.
Tian Y, He Q, Tao C, Li J.
Langmuir. 2006 Jan 3;22(1):360-2.
[ expand abstract ]

A pressure-filter-template approach was employed to prepare fluorescent nanotubes of polyethyleneimine (PEI) and 3,4,9,10-perylenetetracarboxylicdianhydride (PTCDA) through covalent combination in the porous of alumina template based on the layer-by-layer (LbL) assembly technique. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images exhibited a tubular structure of the obtained samples. The wall thickness of the nanotubes is well controlled by varying the assembled cycle number, which is detected by UV-visible spectroscopy. Fourier transform infrared (FT-IR) spectroscopy confirmed the formation of covalent bonds between PEI and PTCDA in nanotubes.

Hydrolytic and Enzymatic Degradation of Nanoparticles Based on Amphiphilic Poly(gamma-glutamic acid)-graft-l-Phenylalanine Copolymers.
Akagi T, Higashi M, Kaneko T, Kida T, Akashi M.
Biomacromolecules. 2006 Jan-Feb;7(1):297-303.
[ expand abstract ]

Amphiphilic graft copolymers consisting of poly(gamma-glutamic acid) (gamma-PGA) as the hydrophilic backbone and l-phenylalanine ethylester (L-PAE) as the hydrophobic side chain were synthesized by grafting L-PAE to gamma-PGA. The nanoparticles were prepared by a precipitation method, and about 200 nm-sized nanoparticles were obtained due to their amphiphilic properties. The hydrolytic and enzymatic degradation of these gamma-PGA nanoparticles was studied by gel permeation chromatography (GPC), scanning electron microscopy (SEM), dynamic light scattering (DLS) and (1)H NMR measurements. The hydrolysis ratio of gamma-PGA and these hydrophobic derivatives was found to decrease upon increasing the hydrophobicity of the gamma-PGA derivates. The pH had an effect on the hydrolytic degradation of the polymer. The hydrolysis of the polymer could be accelerated by alkaline conditions. The degradation of the gamma-PGA backbone by gamma-glutamyl transpeptidase (gamma-GTP) resulted in a dramatic change in nanoparticle morphology. With increasing time, the gamma-PGA nanoparticles began to decrease in size and finally disappeared completely. Moreover, the gamma-PGA nanoparticles were degraded by four different enzymes (Pronase E, protease, cathepsin B and lipase) with different degradation patterns. The enzymatic degradation of the nanoparticles occurred via the hydrolysis of gamma-PGA as the main chain and L-PAE as the side chain. In the case of the enzymatic degradation of gamma-PGA nanoparticles with Pronase E, the size of the nanoparticles increased during the initial degradation stage and decreased gradually when the degradation time was extended. Nanoparticles composed of biodegradable amphiphilic gamma-PGA with reactive function groups can undergo further modification and are expected to have a variety of potential pharmaceutical and biomedical applications, such as drug and vaccine carriers.

Back to Top

Sequential Enzymatic Reactions and Stability of Biomolecules Immobilized onto Phospholipid Polymer Nanoparticles.
Watanabe J, Ishihara K.
Biomacromolecules. 2006 Jan-Feb;7(1):171-5.
[ expand abstract ]

Polymer nanoparticles for sequential enzymatic reactions were prepared by combining a phospholipid polymer shell with a polystyrene core. The active ester groups for the bioconjugation and phospholipid polar groups were incorporated into the phospholipid polymer backbone using a novel active ester monomer and 2-methacryloyloxyethyl phosphorylcholine. For the sequential enzymatic reactions, acetylcholinesterase, choline oxidase, and horseradish peroxidase-labeled IgG were immobilized onto the nanoparticles. As substrates, acetylcholine chloride, choline chloride, and tetramethylbenzidine were added to the nanoparticle suspension, the acetylcholine chloride was converted to choline chloride, the choline chloride was oxidized by choline oxidase, and hydrogen peroxide was then formed as an enzymatic degradation product. The hydrogen peroxide was used for the next enzymatic reaction (oxidized by peroxidase) with tetramethylbenzidine. The sequential enzymatic reactions on the nanoparticles via degradation products (hydrogen peroxide) were significantly higher than that of the enzyme mixture. This result indicated that the diffusion pathway of the enzymatic products and the localization of the immobilized enzyme were important for these reactions. These nanoparticles were capable of facilitating sequential enzymatic reactions.

Bionanotechnology progress and advances.
Chan WC.
Biol Blood Marrow Transplant. 2006 Jan;12(1 Suppl 1):87-91.
[ expand abstract ]

Advances in the nanotechnology research have provided a new set of research tools, materials, structures, and systems for biological and medical research and applications. These nanotechnologies include the application of fluorescent quantum dots for optical imaging, the design of metallic nanoparticle surfaces for ultrasensitive biomolecular fingerprinting, and the use of nanostructures as hyperthermia agents for cancer therapy. Unlike conventional technologies, unique properties can be incorporated into nanometer-size particles, structures, and systems simply by changing their size, shape, and composition. Because of the tunable properties, biologists and clinicians could custom-design a material for a specific research need. In this review article, we highlight the recent advances and progress in Bionanotechnology research as well as provide future perspective on this integrative field.

Back to Top

Polymer nanoengineering for biomedical applications.
Lee LJ.
Ann Biomed Eng. 2006 Jan;34(1):75-88; [Epub 2006 Mar 16].
[ expand abstract ]

Polymeric materials possess many attractive properties such as high toughness and recyclability. Some possess excellent biocompatibility, are biodegradable, and can provide various biofunctionalities. Proper combination of functional polymers and biomolecules can offer tailored properties for various biomedical applications. This overview article covers three major sections: Applications of Polymeric Structures and Devices, Nanoscale Polymer Fabrication Technologies, and Conclusions and Future Directions.

Optofluidic control using photothermal nanoparticles.
Liu GL, Kim J, Lu Y, Lee LP.
Nat Mater. 2006 Jan;5(1):27-32.
[ expand abstract ]

Photothermal metallic nanoparticles have attracted significant attention owing to their energy-conversion properties. Here, we introduce an optofluidic application based on a direct optical-to-hydrodynamic energy conversion using suspended photothermal nanoparticles near the liquid-air interface. Using light beams with submilliwatt power, we can drive and guide liquid flow in microfluidic channels to transport biomolecules and living cells at controlled speeds and directions. Previously, a variety of methods for controlling microscale liquid flow have been developed owing to the increasing interest for microfluidics-based biochemical analysis systems. However, our method dispenses with the need for complex pump and valve devices, surface chemistry and electrode patterning, or any other further effort towards substrate fabrication. Instead, our optofluidic control method will allow the fabrication of all-optical large-scale integrated microfluidic circuits for biomolecular and cellular processing without any physical valve or mechanical pumping device.

The use of microorganisms for the formation of metal nanoparticles and their application.
Mandal D, Bolander ME, Mukhopadhyay D, Sarkar G, Mukherjee P.
Appl Microbiol Biotechnol. 2006 Jan;69(5):485-92.
[ expand abstract ]

Nanomaterials are at the leading edge of the rapidly developing field of nanotechnology. The development of reliable experimental protocols for the synthesis of nanomaterials over a range of chemical compositions, sizes, and high monodispersity is one of the challenging issues in current nanotechnology. In the context of the current drive to develop green technologies in material synthesis, this aspect of nanotechnology is of considerable importance. Biological systems, masters of ambient condition chemistry, synthesize inorganic materials that are hierarchically organized from the nano- to the macroscale. Recent studies on the use of microorganisms in the synthesis of nanoparticles are a relatively new and exciting area of research with considerable potential for development. This review describes a brief overview of the current research worldwide on the use of microorganisms in the biosynthesis of metal nanoparticles and their applications.

Back to Top

Nanoscale organic and polymeric field-effect transistors as chemical sensors.
Wang L, Fine D, Sharma D, Torsi L, Dodabalapur A.
Anal Bioanal Chem. 2006 Jan;384(2):310-21.
[ expand abstract ]

This article reviews recently published work concerning improved understanding of, and advancements in, organic and polymer semiconductor vapor-phase chemical sensing. Thin-film transistor sensors ranging in size from hundreds of microns down to a few nanometers are discussed, with comparisons made of sensing responses recorded at these different channel-length scales. The vapor-sensing behavior of nanoscale organic transistors is different from that of large-scale devices, because electrical transport in a nanoscale organic thin-film transistor depends on its morphological structure and interface properties (for example injection barrier) which could be modulated by delivery of analyte. Materials used in nanoscale devices, for example nanoparticles, nanotubes, and nanowires, are also briefly summarized in an attempt to introduce other relevant nano-transducers.

2005

Where the worlds of nanotechnology, materials science, and bioanalysis converge.
Karst U.
Anal Bioanal Chem. 2005 Dec 30;1 [Epub ahead of print].
[ expand abstract ]

No abstract available

Back to Top

Toward the Isolation of Functional Organic Nanotubes.
Dalgarno SJ, Cave GW, Atwood JL.
Angew Chem Int Ed Engl. 2005 Dec 27;45(4):570-574.
[ expand abstract ]

No abstract available

Generating highly ordered DNA nanostrand arrays.
Guan J, Lee LJ.
Proc Natl Acad Sci U S A. 2005 Dec 20;102(51):18321-5.
[ expand abstract ]

Highly ordered arrays of stretched DNA molecules were generated over the millimeter scale by using a modified molecular combing method and soft lithography. Topological micropatterning on polydimethyl siloxane stamps was used to mediate the dynamic assembly of DNA molecules into arranged nonostrand arrays. These arrays consisted of either short nanostrands of several micrometers with fixed length and orientation or long nanostrands up to several hundred micrometers in length. The nanostrand arrays were transferred onto flat solid surfaces by contact printing, allowing for the creation of more complex patterns. This technique has potential applications for the construction of next-generation DNA chips and functional circuits of DNA-based 1D nanostructures.

Back to Top

Multistep synthesis of a radiolabeled imaging probe using integrated microfluidics.
Lee CC, Sui G, Elizarov A, Shu CJ, Shin YS, Dooley AN, Huang J, Daridon A, Wyatt P, Stout D, Kolb HC, Witte ON, Satyamurthy N, Heath JR, Phelps ME, Quake SR, Tseng HR.
Science. 2005 Dec 16;310(5755):1793-6.
[ expand abstract ]

Microreactor technology has shown potential for optimizing synthetic efficiency, particularly in preparing sensitive compounds. We achieved the synthesis of an [(18)F]fluoride-radiolabeled molecular imaging probe, 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG), in an integrated microfluidic device. Five sequential processes-[18F]fluoride concentration, water evaporation, radiofluorination, solvent exchange, and hydrolytic deprotection-proceeded with high radio-chemical yield and purity and with shorter synthesis time relative to conventional automated synthesis. Multiple doses of [18F]FDG for positron emission tomography imaging studies in mice were prepared. These results, which constitute a proof of principle for automated multistep syntheses at the nanogram to microgram scale, could be generalized to a range of radiolabeled substrates.

A facile method to prepare heparin-functionalized nanoparticles for controlled release of growth factors.
Chung YI, Tae G, Hong Yuk S.
Biomaterials. 2005 Dec 14; [Epub ahead of print].
[ expand abstract ]

A new, facile method to prepare the heparin-functionalized PLGA nanoparticle (HEP-PLGA NP) for the controlled release of growth factors is developed. This system is composed of PLGA as a hydrophobic core, Pluronic F-127 as a hydrophilic surface layer, and heparin as the functional moiety. HEP-PLGA NPs were prepared by a solvent-diffusion method without chemical modification of the components. The entrapment of heparin molecules was confirmed by a negatively increased zeta potential value and the specific binding affinity to antithrombin III. The average diameter and the surface charge of the nanoparticles were ranged from 139+/-2 to 188+/-4nm and from -26.0+/-1.1 to -44.1+/-1.3mV by increasing the amount of heparin during the nanoparticle preparation. Accordingly, the amount of heparin on the nanoparticle increased from 0% to 4.7%. As a model in vitro release experiment, lysozyme was loaded into HEP-PLGA NPs, and a sustained release profile over 2 weeks was obtained with maintaining its bioactivity. The release of rhVEGF, one of the heparin-binding growth factors, showed a more sustained and prolonged profile than that of lysozyme over one month.

Back to Top

Dendrimer-drug interactions.
D'Emanuele A, Attwood D.
Adv Drug Deliv Rev. 2005 Dec 14;57(15):2147-62.
[ expand abstract ]

The interaction between drugs and dendrimers is reviewed with particular reference to the entrapment of drugs within the dendrimer architecture and the electrostatic and covalent complexation of drugs to the dendrimer surface. The application of dendrimer-drug complexation in the enhancement of drug solubility and bioavailability and the use of the complexes as vehicles for the controlled release of drugs and drug targeting is discussed.

Dendrimers in gene delivery.
Dufes C, Uchegbu IF, Schatzlein AG.
Adv Drug Deliv Rev. 2005 Dec 14;57(15):2177-202.
[ expand abstract ]

Dendrimers have unique molecular architectures and properties that make them attractive materials for the development of nanomedicines. Key properties such as defined architecture and a high ratio of multivalent surface moieties to molecular volume also make these nanoscaled materials highly interesting for the development of synthetic (non-viral) vectors for therapeutic nucleic acids. Rational development of such vectors requires the link to be made between dendrimer structure and the morphology and physicochemistry of the respective nucleic acid complexes and, furthermore, to the biological performance of these systems at the cellular and systemic level. The review focuses on the current understanding of the role of dendrimers in those aspects of synthetic vector development. Dendrimer-based transfection agents have become routine tools for many molecular and cell biologists but therapeutic delivery of nucleic acids remains a challenge.

Back to Top

Tumor angiogenic vasculature targeting with PAMAM dendrimer-RGD conjugates.
Shukla R, Thomas TP, Peters J, Kotlyar A, Myc A, Baker Jr JR.
Chem Commun (Camb). 2005 Dec 14;(46):5739-41.
[ expand abstract ]

PAMAM dendrimer-RGD-4C peptide conjugate was synthesized and in vitro targeting efficacy to integrin receptor expressing cells was studied by flow cytometry and confocal microscopy.

Dendrimers in biomedical applications-reflections on the field.
Svenson S, Tomalia DA.
Adv Drug Deliv Rev. 2005 Dec 14;57(15):2106-29.
[ expand abstract ]

The formation of particulate systems with well-defined sizes and shapes is of eminent interest in certain medical applications such as drug delivery, gene transfection, and imaging. The high level of control possible over the architectural design of dendrimers; their size, shape, branching length/density, and their surface functionality, clearly distinguishes these structures as unique and optimum carriers in those applications. The bioactive agents may be encapsulated into the interior of the dendrimers or chemically attached/physically adsorbed onto the dendrimer surface, with the option of tailoring the carrier to the specific needs of the active material and its therapeutic applications. In this regard, the high density of exo-presented surface groups allows attachment of targeting groups or functionality that may modify the solution behavior or toxicity of dendrimers. Quite remarkably, modified dendrimers have been shown to act as nano-drugs against tumors, bacteria, and viruses. Recent successes in simplifying and optimizing the synthesis of dendrimers such as the 'lego' and 'click' approaches, provide a large variety of structures while at the same time reducing the cost of their production. The reflections on biomedical applications of dendrimers given in this review clearly demonstrate the potential of this new fourth major class of polymer architecture and indeed substantiate the high hopes for the future of dendrimers.

Back to Top

Micro- and nanoparticulates.
Moshfeghi AA, Peyman GA.
Adv Drug Deliv Rev. 2005 Dec 13;57(14):2047-52.
[ expand abstract ]

OBJECTIVES: Pharmacotherapeutics has begun to play an increasingly important role in the management of patients with neovascular age-related macular degeneration (AMD). Because micro- and nano-particulates are currently being evaluated as a potential drug-delivery option for AMD patients, the purpose of this analysis was to describe how micro- and nano-particulates have been used experimentally and what their potential clinical applications may be. FINDINGS: Micro- and nano-particulates have been used primarily on a pre-clinical basis as new drug-delivery devices in experimental models of neovascular AMD. CONCLUSIONS: It is likely that micro- and nano-particulates will become an important component of targeted clinical pharmacotherapeutics in patients with neovascular AMD.

The Kinetics of Analyte Capture on Nanoscale Sensors.
Solomon JE, Paul MR.
Biophys J. 2005 Dec 9; [Epub ahead of print].
[ expand abstract ]

This paper presents a number of kinetic analyses related to binding processes relevant to capture of target analyte species in nanoscale cantilever-type devices designed to detect small concentrations of biomolecules. The overall analyte capture efficiency is a crucial measure of the ultimate sensitivity of such devices; while a detailed kinetic analysis tells us how rapidly such measurements may be made. We have analyzed the capture kinetics under a variety of conditions, including the possibility of so-called surface-enhanced ligand capture. One of the modalities studied requires ligand capture through a cross-linking mechanism, and it was found that this mode may provide a robust and sensititive approach to biomolecular detection. For the two modalities studied, we find that detection of specific biomolecules down to concentration levels of 1 nM or less appear to be quite feasible for the device configurations studied.

Back to Top

DNA molecular motor driven micromechanical cantilever arrays.
Shu W, Liu D, Watari M, Riener CK, Strunz T, Welland ME, Balasubramanian S, McKendry RA.
J Am Chem Soc. 2005 Dec 7;127(48):17054-60.
[ expand abstract ]

The unique ability of living systems to translate biochemical reactions into mechanical work has inspired the design of synthetic DNA motors which generate nanoscale motion via controlled conformational change. However, while Nature has evolved intricate mechanisms to convert molecular shape change into specific micrometer-scale mechanical cellular responses, the integration of artificial DNA motors with mechanical devices presents a major challenge. Here we report the direct integration between an ensemble of DNA motors and an array of microfabricated silicon cantilevers. The forces exerted by the precise duplex to nonclassical i-motif conformational change were probed via differential measurements using an in-situ reference cantilever coated with a nonspecific sequence of DNA. Fueled by the addition of protons, the open to close stroke of the motor induced 32 +/- 3 mN/m compressive surface stress, which corresponds to a single motor force of approximately 11 pN/m, an order of magnitude larger than previous classical hybridization studies. Furthermore, the surface-tethered conformational change was found to be highly reversible, in contrast to classical DNA motors which typically suffer rapid system poisoning. The direction and amplitude of motor-induced cantilever motion was tuneable via control of buffer pH and ionic strength, indicating that electrostatic forces play an important role in stress generation. Hybrid devices which directly harness the multiple accessible conformational states of dynamic oligonucleotides and aptamers, translating biochemical energy into micromechanical work, present a radical new approach to the construction of "smart" nanoscale machinery and mechano-biosensors.

Regiochemical functionalization of a nanoscale cage-like structure: Robust core-shell nanostructures crafted as vessels for selective uptake and release of small and large guests.
Turner JL, Chen Z, Wooley KL.
J Control Release. 2005 Dec 5;109(1-3):189-202.
[ expand abstract ]

As synthetic methods evolve toward the preparation of increasingly complex nanostructured materials inspired from biological nano-objects, the ability to tailor the three-dimensional architecture and the placement of functional groups at well-defined positions within those frameworks is advancing. In this report, we demonstrate the ability to functionalize selectively internal and external sites (regiochemically) within polymer nanocages, to advance their development as synthetic analogs of viral capsids. Nanocages, possessing carbonyl groups on their internal surfaces and acrylic acid residues throughout their structure were prepared and functionalized, through either Schiff-base chemistry, to attach covalently phosphatidylethanolamine-based lipids within the nanocage, or carbodiimide-mediated coupling, to attach covalently the lipids throughout the shell. The resulting nanostructures were altered by the insertion of molecules within and on the structure, including, for the Schiff base functionalized nanostructure, an enhanced response to pH and increased uptake of hydrophobic guests. Additionally, the use of phosphatidylethanolamine lipids labeled with 7-nitrobenz-2-oxa-1,3-diazole (NBD) allowed for determination of the environmental polarities of the lipid domains within the lipid-nanocage constructs.

Back to Top

Nanoparticle assemblies with molecular springs: a nanoscale thermometer.
Lee J, Govorov AO, Kotov NA.
Angew Chem Int Ed Engl. 2005 Dec 1;44(45):7439-42.
[ expand abstract ]

No abstract available.

Role of nanobiotechnology in developing personalized medicine for cancer.
Jain KK.
Technol Cancer Res Treat. 2005 Dec;4(6):645-50.
[ expand abstract ]

Personalized medicine simply means the prescription of specific therapeutics best suited for an individual. Personalization of cancer therapies is based on a better understanding of the disease at the molecular level. Nanotechnology will play an important role in this area. Nanobiotechnology is being used to refine discovery of biomarkers, molecular diagnostics, drug discovery and drug delivery, which are important basic components of personalized medicine and are applicable to management of cancer as well. Examples are given of the application of quantum dots, gold nanoparticles, and molecular imaging in diagnostics and combination with therapeutics -- another important feature of personalized medicine. Personalized medicine is beginning to be recognized and is expected to become a part of medical practice within the next decade. Personalized management of cancer, facilitated by nanobiotechnology, is expected to enable early detection of cancer, more effective and less toxic treatment increasing the chances of cure.

Back to Top

Designing dendrimers for biological applications.
Lee CC, Mackay JA, Frechet JM, Szoka FC.
Nat Biotechnol. 2005 Dec;23(12):1517-26.
[ expand abstract ]

Dendrimers are branched, synthetic polymers with layered architectures that show promise in several biomedical applications. By regulating dendrimer synthesis, it is possible to precisely manipulate both their molecular weight and chemical composition, thereby allowing predictable tuning of their biocompatibility and pharmacokinetics. Advances in our understanding of the role of molecular weight and architecture on the in vivo behavior of dendrimers, together with recent progress in the design of biodegradable chemistries, has enabled the application of these branched polymers as anti-viral drugs, tissue repair scaffolds, targeted carriers of chemotherapeutics and optical oxygen sensors. Before such products can reach the market, however, the field must not only address the cost of manufacture and quality control of pharmaceutical-grade materials, but also assess the long-term human and environmental health consequences of dendrimer exposure in vivo.

Light-induced gene transfer from packaged DNA enveloped in a dendrimeric photosensitizer.
Nishiyama N, Iriyama A, Jang WD, Miyata K, Itaka K, Inoue Y, Takahashi H, Yanagi Y, Tamaki Y, Koyama H, Kataoka K.
Nat Mater. 2005 Dec;4(12):934-41.
[ expand abstract ]

The control of gene transfection in the body is a core issue in gene therapy. Photochemical internalization is a technology that allows light-induced delivery of DNA, drugs or other biological factors directly inside cells. Usually it requires that a photosensitizer be added to the drug-delivery system to photochemically destabilize the endosomal membrane. Here we present a system for in vivo DNA delivery in which these two components are assembled into one structure. This is a ternary complex composed of a core containing DNA packaged with cationic peptides and enveloped in the anionic dendrimer phthalocyanine, which provides the photosensitizing action. The ternary complex showed more than 100-fold photochemical enhancement of transgene expression in vitro with reduced photocytotoxicity. In an animal experiment, subconjuctival injection of the ternary complex followed by laser irradiation resulted in transgene expression only in the laser-irradiated site. This work demonstrates a new biomedical application for dendrimers, and the first success in the photochemical-internalization-mediated gene delivery in vivo.

Back to Top

Nanotechnology in cancer detection and treatment.
Singh KK.
Technol Cancer Res Treat. 2005 Dec;4(6):583-4.
[ expand abstract ]

No abstract available.

Nanoparticles of Poorly Water-Soluble Drugs Prepared by Supercritical Fluid Extraction of Emulsions.
Shekunov BY, Chattopadhyay P, Seitzinger J, Huff R.
Pharm Res. 2005 Nov 30; [Epub ahead of print].
[ expand abstract ]

PURPOSE: The aim of the study was to develop and evaluate a new method for the production of micro- and nanoparticles of poorly soluble drugs for drug delivery applications. METHODS: Fine particles of model compounds cholesterol acetate (CA), griseofulvin (GF), and megestrol acetate (MA) were produced by extraction of the internal phase of oil-in-water emulsions using supercritical carbon dioxide. The particles were obtained both in a batch or a continuous manner in the form of aqueous nanosuspensions. Precipitation of CA nanoparticles was used for conducting a mechanistic study on particle size control and scale-up. GF and MA nanoparticles were produced in several batches to compare their dissolution behavior with that of micronized materials. The physical analysis of the particles produced was performed using dynamic light scattering (particle size), scanning electron microscopy (morphology), powder X-ray diffraction (crystallinity), gas chromatography (residual solvent), and a dissolution apparatus. RESULTS: Particles with mean volume diameter ranging between 100 and 1000 nm were consistently produced. The emulsion droplet size, drug solution concentration, and organic solvent content in the emulsion were the major parameters responsible for particle size control. Efficient and fast extraction, down to low parts-per-million levels, was achieved with supercritical CO(2). The GF and MA nanoparticles produced were crystalline in nature and exhibited a 5- to 10-fold increase in the dissolution rate compared with that of micronized powders. Theoretical calculations indicated that this dissolution was governed mainly by the surface kinetic coefficient and the specific surface area of the particles produced. It was observed that the necessary condition for a reliable and scalable process was the sufficient emulsion stability during the extraction time. CONCLUSION: The method developed offers a viable alternative to both the milling and constructive nanoparticle formation processes. Although preparation of a stable emulsion can be a challenge for some drug molecules, the new technique significantly shortens the processing time and overcomes the current limitations of the conventional precipitation techniques in terms of large waste streams, product purity, and process scale-up.

Back to Top

Preparation, characterization and application of magnetic silica nanoparticle functionalized multi-walled carbon nanotubes.
Deng Y, Deng C, Yang D, Wang C, Fu S, Zhang X.
Chem Commun (Camb). 2005 Nov 28;(44):5548-50.
[ expand abstract ]

Magnetic silica nanoparticle functionalized multi-walled carbon nanotubes (MS-MWNTs) were prepared, characterized and used for the convenient, rapid and efficient separation of trace aromatic compounds.

Nanoliter scale microbioreactor array for quantitative cell biology.
Lee PJ, Hung PJ, Rao VM, Lee LP.
Biotechnol Bioeng. 2005 Nov 28; [Epub ahead of print].
[ expand abstract ]

A nanoliter scale microbioreactor array was designed for multiplexed quantitative cell biology. An addressable 8 x 8 array of three nanoliter chambers was demonstrated for observing the serum response of HeLa human cancer cells in 64 parallel cultures. The individual culture unit was designed with a "C" shaped ring that effectively decoupled the central cell growth regions from the outer fluid transport channels. The chamber layout mimics physiological tissue conditions by implementing an outer channel for convective "blood" flow that feeds cells through diffusion into the low shear "interstitial" space. The 2 microm opening at the base of the "C" ring established a differential fluidic resistance up to 3 orders of magnitude greater than the fluid transport channel within a single mold microfluidic device. Three-dimensional (3D) finite element simulation were used to predict fluid transport properties based on chamber dimensions and verified experimentally. The microbioreactor array provided a continuous flow culture environment with a Peclet number (0.02) and shear stress (0.01 Pa) that approximated in vivo tissue conditions without limiting mass transport (10 s nutrient turnover). This microfluidic design overcomes the major problems encountered in multiplexing nanoliter culture environments by enabling uniform cell loading, eliminating shear, and pressure stresses on cultured cells, providing stable control of fluidic addressing, and permitting continuous on-chip optical monitoring. (c) 2005 Wiley Periodicals, Inc.

Back to Top

Effect of enzymatic degradation on the release kinetics of model drug from Pluronic F127/poly(lactic acid) nano-particles.
Xiong XY, Tam KC, Gan LH.
J Control Release. 2005 Nov 28;108(2-3):263-70.
[ expand abstract ]

Poly(lactic acid) (PLA) was successfully grafted to both ends of Pluronic F127 block copolymer (PEO-PPO-PEO) to obtain amphiphilic PLA-F127-PLA block copolymers. The effect of enzymatic degradation on the release behaviors of hydrophobic model drug 9-(methylaminomethyl)anthracene (MAMA) from PLA-F127-PLA nano-particles with vesicular structure was studied by UV-Vis spectroscopy. It was observed that the release rate of MAMA from PLA-F127-PLA nano-particles with the enzymatic degradation varied with temperature due to the activity of the enzyme with temperature. However, the enzyme concentration has negligible effect on the release rates of MAMA.

Nanoparticle-DNA conjugates bearing a specific number of short DNA strands by enzymatic manipulation of nanoparticle-bound DNA.
Qin WJ, Yung LY.
Langmuir. 2005 Nov 22;21(24):11330-4.
[ expand abstract ]

Self-assembling of metallic nanoparticles to form well-defined nanostructured structures is a field that has been receiving considerable research interest in recent years. In this field, DNA is a commonly used linker molecule to direct the assembly of the nanoscale building blocks because of its unique recognition capabilities, mechanical rigidity, and physicochemical stability. This study reported our novel approach to generate gold nanoparticle-DNA conjugates bearing specially designed DNA linker molecules that can be used as building blocks to construct nanoassemblies with precisely controlled structure or as nanoprobes for quantitative DNA sequence detection analysis. In our approach, gold nanoparticle-DNA conjugates bearing a specific number of long double-stranded DNA strands were prepared by gel electrophoresis. A restriction endonuclease enzyme was then used to manipulate the length of the nanoparticle-bound DNA. This enzymatic cleavage was confirmed by gel electrophoresis, and digestion efficiency of 90% or more was achieved. With this approach, nanoparticle conjugates bearing a specific number of strands of short DNA with less than 20-base can be achieved.

Back to Top

Materials and biology. Nanotechnology takes aim at cancer.
Service RF.
Science.
[ expand abstract ]

No abstract available

Chip devices for miniaturized biotechnology.
Kohler JM, Henkel T.
Appl Microbiol Biotechnol. 2005 Nov;69(2):113-25.
[ expand abstract ]

Chip devices were introduced in chemistry and molecular biology to improve the read-out of information from molecular systems by efficient analytical procedures and to organize automated experiments. Biochips and chip reactor systems are of interest for cellular processes, too, and can be regarded as components in interfaces for the information exchange between living nature and digital electronic systems. In this minireview, different types of chip reactors for biotechnological applications like nanotiterplates, chip thermocyclers and devices for segmented flow operations are discussed. Finally, an outlook is given on the application of chip reactor systems, which are promising tools for automated experiments with highly parallelized screening procedures, for artificial microcompartmentation, cell analogue systems, micro-ecological studies, investigations on modulated morphogenesis, and for a bioanalogue molecular nanotechnology.

Back to Top

Chiral separations on multichannel microfluidic chips.
Gao Y, Shen Z, Wang H, Dai Z, Lin B.
Electrophoresis. 2005 Nov 9; [Epub ahead of print].
[ expand abstract ]

Chiral separations of FITC-labeled basic drugs on multichannel microfluidic chips with LIF detector were investigated. A preliminary screening procedure for seven neutral CDs was performed under optimized conditions for chiral separations of three FITC-labeled drugs (baclofen, norfenefrine, and tocainide) on a mono-channel microfluidic chip. According to the results of screening, FITC-baclofen and FITC-norfenefrine as well as two chiral selectors including gamma-CD and dimethyl-beta-CD (DM-beta-CD) were selected as models to perform chiral separations on a two-channel chip. FITC-baclofen enantiomers were separated completely by gamma-CD in one channel, while resolution of FITC-norfenefrine enantiomers was achieved by DM-beta-CD in the other channel in the same run. Furthermore, the feasibility of using one chiral selector to separate multiple chiral samples was studied on a four-channel chip. These results show that multichannel chip has a potential for chiral high-throughput screening.

Directed growth of pure phosphatidylcholine nanotubes in microfluidic channels.
Brazhnik KP, Vreeland WN, Hutchison JB, Kishore R, Wells J, Helmerson K, Locascio LE.
Langmuir. 2005 Nov 8;21(23):10814-7.
[ expand abstract ]

The morphology of self-assembled phospholipid membranes (e.g., micelles, vesicles, rods, tubes, etc.) depends on the method of formation, secondary manipulation, temperature, and storage conditions. In this contribution, microfluidic systems are used to create pure phosphatidylcholine (PC) micro- and nanotubes with unprecedented lengths. Tubes up to several centimeters in length and aligned with the long axis of the microchannel were created from spots of dry films of 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). These high aspect ratio structures, which, to our knowledge, represent the first examples of extended tubes formed from pure PC lipids, were examined by fluorescence microscopy, electron and optical microscopy, and optical manipulation tools (i.e., a laser trap and laser scalpel) to characterize structure and stability. In particular, the tubular structure was confirmed by observation of fluorescent dyes that were sequestered within the aqueous cavity or within the phospholipid tube. Compared to other phospholipid tubes, the tubes formed from PC lipids in microfluidic channels show high mechanical stability and rigidity that depend on tube size, age, and storage conditions.

Back to Top

Ultra-high-yield growth of vertical single-walled carbon nanotubes: Hidden roles of hydrogen and oxygen.
Zhang G, Mann D, Zhang L, Javey A, Li Y, Yenilmez E, Wang Q, McVittie JP, Nishi Y, Gibbons J, Dai H.
Proc Natl Acad Sci U S A. 2005 Nov 8;102(45):16141-5.
[ expand abstract ]

An oxygen-assisted hydrocarbon chemical vapor deposition method is developed to afford large-scale, highly reproducible, ultra-high-yield growth of vertical single-walled carbon nanotubes (V-SWNTs). It is revealed that reactive hydrogen species, inevitable in hydrocarbon-based growth, are damaging to the formation of sp(2)-like SWNTs in a diameter-dependent manner. The addition of oxygen scavenges H species and provides a powerful control over the C/H ratio to favor SWNT growth. The revelation of the roles played by hydrogen and oxygen leads to a unified and universal optimum-growth condition for SWNTs. Further, a versatile method is developed to form V-SWNT films on any substrate, lifting a major substrate-type limitation for aligned SWNTs.

Regiochemical functionalization of a nanoscale cage-like structure: Robust core-shell nanostructures crafted as vessels for selective uptake and release of small and large guests.
Turner JL, Chen Z, Wooley KL.
J Control Release. 2005 Nov 5; [Epub ahead of print].
[ expand abstract ]

As synthetic methods evolve toward the preparation of increasingly complex nanostructured materials inspired from biological nano-objects, the ability to tailor the three-dimensional architecture and the placement of functional groups at well-defined positions within those frameworks is advancing. In this report, we demonstrate the ability to functionalize selectively internal and external sites (regiochemically) within polymer nanocages, to advance their development as synthetic analogs of viral capsids. Nanocages, possessing carbonyl groups on their internal surfaces and acrylic acid residues throughout their structure were prepared and functionalized, through either Schiff-base chemistry, to attach covalently phosphatidylethanolamine-based lipids within the nanocage, or carbodiimide-mediated coupling, to attach covalently the lipids throughout the shell. The resulting nanostructures were altered by the insertion of molecules within and on the structure, including, for the Schiff base functionalized nanostructure, an enhanced response to pH and increased uptake of hydrophobic guests. Additionally, the use of phosphatidylethanolamine lipids labeled with 7-nitrobenz-2-oxa-1,3-diazole (NBD) allowed for determination of the environmental polarities of the lipid domains within the lipid-nanocage constructs.

Back to Top

In vitro non-viral gene delivery with nanofibrous scaffolds.
Liang D, Luu YK, Kim K, Hsiao BS, Hadjiargyrou M, Chu B.
Nucleic Acids Res. 2005 Nov 3;33(19):e170.
[ expand abstract ]

Extracellular and intracellular barriers typically prevent non-viral gene vectors from having an effective transfection efficiency. Formulation of a gene delivery vehicle that can overcome the barriers is a key step for successful tissue regeneration. We have developed a novel core-shelled DNA nanoparticle by invoking solvent-induced condensation of plasmid DNA (beta-galactosidase or GFP) in a solvent mixture [94% N,N-dimethylformamide (DMF) + 6% 1x TE buffer] and subsequent encapsulation of the condensed DNA globule in a triblock copolymer, polylactide-poly(ethylene glycol)-polylactide (L8E78L8), in the same solvent environment. The polylactide shell protects the encapsulated DNA from degradation during electrospinning of a mixture of encapsulated DNA nanoparticles and biodegradable PLGA (a random copolymer of lactide and glycolide) to form a nanofibrous non-woven scaffold using the same solution mixture. The bioactive plasmid DNA can then be released in an intact form from the scaffold with a controlled release rate and transfect cells in vitro.

Nanoscale hydrodynamics: enhanced flow in carbon nanotubes.
Majumder M, Chopra N, Andrews R, Hinds BJ.
Nature. 2005 Nov 3;438(7064):44.
[ expand abstract ]

Nanoscale structures that could mimic the selective transport and extraordinarily fast flow possible in biological cellular channels would have a wide range of potential applications. Here we show that liquid flow through a membrane composed of an array of aligned carbon nanotubes is four to five orders of magnitude faster than would be predicted from conventional fluid-flow theory. This high fluid velocity results from an almost frictionless interface at the carbon-nanotube wall.

Back to Top

Preparation of solid lipid nanoparticles using a membrane contactor.
Charcosset C, El-Harati A, Fessi H.
J Control Release. 2005 Nov 2;108(1):112-20.
[ expand abstract ]

Solid lipid nanoparticles (SLN) were introduced at the beginning of the 1990s, as an alternative to solid nanoparticles, emulsions and liposomes in cosmetic and pharmaceutical preparations. The present study investigates a new process for the preparation of SLN using a membrane contactor. The lipid phase is pressed, at a temperature above the melting point of the lipid, through the membrane pores allowing the formation of small droplets. The aqueous phase circulates inside the membrane module, and sweeps away the droplets forming at the pore outlets. SLN are formed by the following cooling of the preparation to room temperature. The influence of process parameters (aqueous phase and lipid phase temperatures, aqueous phase cross-flow velocity and lipid phase pressure, membrane pore size) on the SLN size and on the lipid phase flux is investigated. It is shown that the membrane contactor allows the preparation of SLN with a lipid phase flux between 0.15 and 0.35 m(3)/h m(2), and a mean SLN size between 70 and 215 nm. The advantages of this new process are its facility of use, the control of the SLN size by an appropriate choice of process parameters, and its scaling-up abilities.

Physico-chemical characterization of polysaccharide-coated nanoparticles.
Lemarchand C, Gref R, Lesieur S, Hommel H, Vacher B, Besheer A, Maeder K, Couvreur P.
J Control Release. 2005 Nov 2;108(1):97-111.
[ expand abstract ]

A series of amphiphilic copolymers (PCL-DEX) made of poly(varepsilon-caprolactone) (PCL) side chains grafted onto a dextran (DEX) backbone, was used to modify the surface of PCL nanoparticles. PCL-DEX nanoparticles were prepared by a technique derived from emulsion-solvent evaporation. The purpose of the present study was to investigate the DEX coating (quantification, conformation, mobility) in order to better understand particle surface-protein interactions. The DEX coating was deeply examined using different complementary methods: zeta potential measurement, specific degradation of the DEX shell by dextranase, energy-filtering transmission electron microscopy coupled to image-spectrum electron energy-loss spectroscopy, electronic paramagnetic resonance, high performance size exclusion chromatography as well as nonspecific bovine serum albumin adsorption. All our data together supported a core-shell structure of the nanoparticles, DEX moieties constituting the external coating. The amount of DEX located on the nanoparticle surface was estimated to 70%. The organisation of the shell including chains density and mobility was found to be dramatically influenced by DEX molar mass. The steric repulsion conferred by the presence of DEX at the surface of the nanoparticles decreased the adsorption of albumin. The nanoparticle-protein interaction was, however, greatly influenced by the polysaccharide conformation onto the surface.

Back to Top

Microstructured layers of spherical biofunctional core-shell nanoparticles provide enlarged reactive surfaces for protein microarrays.
Borchers K, Weber A, Brunner H, Tovar GE.
Anal Bioanal Chem. 2005 Nov;383(5):738-46.
[ expand abstract ]

Nanostructured core-shell particles with tailor-made affinity surfaces were used to generate microstructured affinity surfaces by microspotting the particles to form densely packed amorphous nanoparticle layers. These layers provided a large reactive surface for the specific binding of protein ligands from aqueous solution. Biofunctional core-shell particles were synthesized for this purpose that consisted of a silica core with a diameter of 100 nm and an organic shell a few nm thick. The nanoparticle core was prepared by sol-gel chemistry and the shell formed in suspension by organosilane chemistry. The shell provided amino groups or carbonyl groups at its outer surface for subsequent covalent immobilization of streptavidin, rabbit IgG antibodies or goat IgG antibodies. AlexaFluor 647((R))-conjugated and biotinylated cytochrome C and CyDye-labeled anti-rabbit IgG and anti-goat IgG were probed as model analytes. The core-shell nanoparticles were spotted using a pin-ring micro-arrayer onto microscope glass slides that were coated with a polycation monolayer by dip-coating prior to nanoparticle deposition. Amorphous particle layers of well-defined thicknesses in the range of 100 nm to 2 mum were obtained by printing aqueous particle suspensions containing 5-500 mg/mL (0.5-50 wt%) of silica particles. The specific affinity of the plotted nanoparticulate capture surface was demonstrated by binding Cy3-labeled donkey anti-rabbit IgG and Cy5-labeled mouse anti-goat IgG to immobilized rabbit IgG and goat IgG particles. The signal intensity per spot increased for any given analyte concentration when the amount of particles per spot was augmented. This was attributed to the increasing integration of receptor molecules per surface footprint, which shifted the binding equilibrium towards the formation of the receptor-ligand complex. Additionally, the locally-increased supply of receptor molecules at the nanoparticulate microchip surface resulted in a wide dynamic range of 4 fM-20 nM (covering six orders of magnitude).

Unique features of a pH-sensitive fusogenic peptide that improves the transfection efficiency of cationic liposomes.
Futaki S, Masui Y, Nakase I, Sugiura Y, Nakamura T, Kogure K, Harashima H.
J Gene Med. 2005 Nov;7(11):1450-8.
[ expand abstract ]

BACKGROUND: One of the critical steps in intracellular gene delivery using cationic liposomes is the endosomal escape of the plasmid/liposome complexes to the cytosol. The addition of GALA, a pH-sensitive fusogenic peptide, is a promising method to accelerate this step in order to enhance the expression of the desired proteins. Detailed studies on the methods of enhancement would broaden the horizon of its application. METHODS: Using representative commercially available cationic liposomes (Lipofectin, Lipofectamine, and Lipofectamine 2000), the effects of GALA on transfection efficiency were studied by luciferase assay and confocal microscopic observations. RESULTS: A concentration-dependent increase in the transfection efficiency was observed for GALA. Addition of 0.1 microM GALA to the plasmid/liposome complex significantly increased the transfection efficiency, especially in the case of Lipofectin, but higher concentration of GALA decreased transfection efficiency. Successful reduction in the liposomal dosage was attained by employing GALA while maintaining a high transfection efficiency. Interestingly, although the transfection efficiency was higher in the presence of GALA, a lower amount of the plasmid DNA was taken up by the cells. Confocal microscopic observations of the rhodamine-labeled plasmid did not show a significant difference in the cellular localization among cells incubated in the presence or absence of GALA, suggesting that a slight increase in GALA-induced release of the plasmid to the cytosol may cause a significant change in the transfection efficiency. CONCLUSION: The unique features of GALA to mediate improved transfection efficiencies were identified.

Back to Top

Synthesis and in vitro drug release behavior of amphiphilic triblock copolymer nanoparticles based on poly (ethylene glycol) and polycaprolactone.
Zhang Y, Zhuo RX.
Biomaterials. 2005 Nov;26(33):6736-42.
[ expand abstract ]

Novel BAB type amphiphilic triblock copolymers consisting of poly (ethylene glycol) (PEG) (B) as hydrophilic segment and poly (epsilon-caprolactone) (PCL) (A) as hydrophobic block were prepared by coupling reaction using L-lysine methyl ester diisocyanate (LDI) as the chain extender. The triblock copolymers obtained were characterized by FT-IR, 1H NMR, GPC, and DSC. Core-shell type nanoparticles were prepared by nanoprecipitation method and below 100 nm nanoparticles were obtained due to their specific structure. Transmission electron microscopy image demonstrated that these nanoparticles were spherical in shape. Stability of the nanoparticles in biological media was evaluated. Poorly water-soluble anticancer drug 4'-demethyl-epipodophyllotoxin (DMEP) was chosen for controlled drug release because it was easily encapsulated into polymeric nanoparticles via hydrophobic interaction. In vitro release behavior of DMEP from polymeric nanoparticles was investigated, the results showed that the drug release rate can be modulated by the variation of the copolymer composition.

Enhanced cell-seeding into 3D porous scaffolds by use of magnetite nanoparticles.
Shimizu K, Ito A, Honda H.
J Biomed Mater Res B Appl Biomater. 2005 Oct 21; [Epub ahead of print].
[ expand abstract ]

To engineer functional tissues, a large number of cells must be successfully seeded into scaffolds. We previously proposed a methodology for tissue engineering using magnetite nanoparticles and magnetic force, which we termed "Mag-TE." In the present study, we applied the Mag-TE technique to a cell seeding process and have termed the technique "Mag-seeding." The cell-seeding efficiency of NIH/3T3 fibroblasts (FBs) by Mag-seeding was investigated using six types of commercially available scaffolds (5 collagen sponges and 1 D,D-L,L polylactic acid sponge) having various pore sizes. FBs were magnetically labeled with our original magnetite cationic liposomes (MCLs), which have a positive surface charge, to improve adsorption onto the cell surface. FBs labeled with MCLs were seeded onto a scaffold, and a magnet (4 kG) was placed under the scaffold. Mag-seeding facilitated successful cell seeding into the deep internal space of the scaffolds. Cell-seeding efficiency increased significantly in all scaffolds when compared to those without magnetic force. Moreover, when a high-intensity magnet (10 kG) was used, cell-seeding efficiency was significantly enhanced. These results suggest that Mag-seeding is a promising approach for tissue engineering. (c) 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005.

Back to Top

Nanoparticle Assemblies with Molecular Springs: A Nanoscale Thermometer.
Lee J, Govorov AO, Kotov NA.
Angew Chem Int Ed Engl. 2005 Oct 18; [Epub ahead of print].
[ expand abstract ]

No abstract available

Silica encapsulation and magnetic properties of FePt nanoparticles.
Aslam M, Fu L, Li S, Dravid VP.
J Colloid Interface Sci. 2005 Oct 15;290(2):444-9.
[ expand abstract ]

Core-shell nanoparticles have emerged as an important class of functional nanostructures with potential applications in many diverse fields, especially in health sciences. We have used a modified aqueous sol-gel route for the synthesis of size-selective FePt@SiO2 core-shell nanoparticles. In this approach, oleic acid and olyel amine stabilized FePt nanoparticles are first encapsulated through an aminopropoxysilane (APS) monolayer and then subsequent condensation of triethoxysilane (TEOS) on FePt particle surface. These well-defined FePt@SiO2 core-shell nanoparticles with narrow size distribution become colloidal in aqueous media, and can thus be used as carrier fluid for biomolecular complexes. In comparison, the scarce hydrophilic nature of oleic acid monolayers on FePt particle surface yields an edgy partial coating of silica when only TEOS is applied for the surface modification. The synthesized core-shell nanoparticles were characterized by direct techniques of high resolution transmission electron microscopy (HRTEM), EDS and indirectly via UV-vis absorption and FTIR studies. The FePt@SiO2 nanoparticles exhibit essential characteristics of superparamagnetic behavior, as investigated by SQUID magnetometry. The blocking temperatures (T(B)) of FePt and FePt@SiO2 (135 and 80 K) were studied using zero field cooled (ZFC)/field cooled (FC) curves

Back to Top

Loading of hydrophobic materials into polymer particles: implications for fluorescent nanosensors and drug delivery.
Zhu H, McShane MJ.
J Am Chem Soc. 2005 Oct 5;127(39):13448-9.
[ expand abstract ]

A straightforward method for loading hydrophobic materials into commercially available polymer nano- or microparticles is described. PMMA and PS nano/microparticles were swelled by an organic solvent with an ionic surfactant (SDS) to stabilize the particles in aqueous solution. FITC and Ru(dpp)(3)Cl(2) were loaded into those particles based on the principle of "like dissolves like". Further surface modification of the loaded particles was achieved via layer-by-layer (LbL) self-assembly. Culture of fibroblasts with the dye-doped, coated particles showed that the cells internalized the fluorescent particles with no apparent toxic effects. The findings suggest the facile process could be useful in a wide range of applications for fluorescent micro/nanosensors and drug delivery.

NMR characterization of paclitaxel/poly (styrene-isobutylene-styrene) formulations.
Chen JZ, Ranade SV, Xie XQ.
Int J Pharm. 2005 Oct 1; [Epub ahead of print].
[ expand abstract ]

TAXUStrade mark is a coronary drug-eluting stent system utilizing a formulation consisting of cellular-target drug paclitaxel and poly (styrene-isobutylene-styrene) (SIBS). The present study investigates the interaction and interfacial dynamics of paclitaxel incorporated in a nano-polymeric matrix system. Solution and solid-state CP/MAS NMR experiments were designed to characterize the microstructure of heterogeneous drug-polymer mixtures in terms of its composition, molecular mobility, molecular order, paclitaxel-SIBS molecular interactions, and molecular mobility of the drug in the polymer matrix. The NMR spectra demonstrated unchanged chemical shifts between the neat and incorporated paclitaxel, and suggested that the level of the interactions between paclitaxel and SIBS is limited to non-bonding interactions or physical interactions between paclitaxel and SIBS when mixed in solution under NMR detection. Carbon spin-lattice relaxation time and proton spin-lattice relaxation time in the rotating frame offer further confirmation that the mobility of paclitaxel is increased in the paclitaxel-SIBS mixture. The results also indicate that a change occurs from crystalline packing to amorphous packing in paclitaxel due to its intermolecular interaction with SIBS. Our studies were used in understanding the detailed structure, morphology, and molecular motion of paclitaxel in the paclitaxel-SIBS system and to probe chemical and physical heterogeneity down to the nanometer scale.

Back to Top

Tat-Conjugated PAMAM Dendrimers as Delivery Agents for Antisense and siRNA Oligonucleotides.
Kang H, Delong R, Fisher MH, Juliano RL.
Pharm Res. 2005 Oct 1; [Epub ahead of print].
[ expand abstract ]

PURPOSE: PAMAM G5 dendrimer (P) was conjugated to Tat peptide (T), a cell penetrating peptide, in search of an efficient cellular delivery vehicle for antisense and siRNA oligonucleotides. METHODS: PAMAM G5 dendrimer was reacted with 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propionic acid, sulfosuccinimidyl ester, sodium salt (BODIPY) for visualization to yield the conjugate BP. Bifunctional sulfosuccinimidyl 6-[alpha-methyl-alpha-(2-pyridyldithio)toluamido]hexanoate (sulfo-LC-SMPT) was then used to conjugate primary amino groups of BP to cysteine derivatized Tat peptide to give the designed conjugate, BPT. This conjugate was complexed with antisense and siRNA oligonucleotides designed to inhibit MDR1 gene expression. NIH 3T3 MDR cells were used for the evaluation of biological activity of the conjugate. RESULTS: Both antisense and siRNA readily formed complexes with the synthesized BPT, introduced into NIH 3T3 MDR cells, and primarily accumulated in intracellular vesicles. MDR1 gene expression was partially inhibited by the antisense-BPT complex and weakly inhibited by the siRNA-BPT complex when both were tested at nontoxic levels of dendrimer. Conjugation with Tat peptide did not improve the delivery efficiency of the dendrimer. CONCLUSIONS: Dendrimer-oligonucleotide complexes were moderately effective for delivery of antisense and only poorly effective for delivery of siRNA. Conjugation of the dendrimer with the Tat cell penetrating peptide failed to further enhance the effectiveness of the dendrimer.

Surface modification of gold and quantum dot nanoparticles with chitosan for bioapplications.
Tan WB, Zhang Y.
J Biomed Mater Res A. 2005 Oct 1;75(1):56-62.
[ expand abstract ]

Gold (Au) and quantum dot (QD) nanoparticles, which have been extensively used in many fields, were encapsulated with a natural polymer, chitosan, to improve their biocompatibility. Characterization was performed using ultraviolet-visible, dynamic light scattering, atomic force microscopy, and transmission electron microscope analyses. It was found that a Au/chitosan ratio of 1:1 and smaller produced chitosan-encapsulated Au nanoparticles of a sufficiently small size, and this result was then applied in the chitosan encapsulation of QDs. The biocompatibility of both types of nanoparticles was assessed in cell culture studies using HT29 human colon carcinoma and NIH 3T3 mouse fibroblast cells. MTT and trypan blue exclusion assays revealed that both chitosan-encapsulated Au nanoparticles and QDs exhibited improved biocompatibility over their bare, nonencapsulated counterparts. Therefore, this study showed that chitosan could be used to encapsulate both Au nanoparticles and QDs in order to enhance their biocompatibility. The approaches developed in this study can also be extended to other nanoparticles for bioapplications as well.

Back to Top

Simultaneous monitoring of temperature and T(1): Methods and preliminary results of application to drug delivery using thermosensitive liposomes.
Bos C, Lepetit-Coiffe M, Quesson B, Moonen CT.
Magn Reson Med. 2005 Oct;54(4):1020-4.
[ expand abstract ]

A method is presented to obtain temperature and longitudinal relaxivity measurements simultaneously and in near real-time. Quantitative relaxivity values are obtained from the signal magnitude from fast Look-Locker EPI data, whereas phase information from all signal samples on the recovery curve is combined to provide temperature values using the proton resonance frequency method. The utility of this technique is illustrated in an in vitro experiment with thermosensitive liposomes, which are studied as potential micro vehicles for local drug delivery. The method allowed measuring the evolution of relaxivity during RF-heating of liposomes containing a paramagnetic contrast agent, demonstrating increase of liposome permeability near the phase transition temperature. Potential applications are monitoring of local drug delivery using thermosensitive liposomes, and confirmation of reaching the liposomes' threshold temperature during thermal therapy. Magn Reson Med, 2005.

Poly(d,l-lactide-co-glycolide)/montmorillonite nanoparticles for oral delivery of anticancer drugs.
Dong Y, Feng SS.
Biomaterials. 2005 Oct;26(30):6068-76.
[ expand abstract ]

This research developed a novel bioadhesive drug delivery system, poly(d,l-lactide-co-glycolide)/montmorillonite (PLGA/MMT) nanoparticles, for oral delivery of paclitaxel. Paclitaxel-loaded PLGA/MMT nanoparticles were prepared by the emulsion/solvent evaporation method. MMT was incorporated in the formulation as a matrix material component, which also plays the role of a co-emulsifier in the nanoparticle preparation process. Paclitaxel-loaded PLGA/MMT nanoparticles were found to be of spherical shape with a mean size of around 310 nm and polydispersity of less than 0.150. Adding MMT component to the matrix material appears to have little influence on the particles size and the drug encapsulation efficiency. The drug release pattern was found biphasic with an initial burst followed by a slow, sustained release, which was not remarkably affected by the MMT component. Cellular uptake of the fluorescent coumarin 6-loaded PLGA/MMT nanoparticles showed that MMT enhanced the cellular uptake efficiency of the pure PLGA nanoparticles by 57-177% for Caco-2 cells and 11-55% for HT-29 cells, which was dependent on the amount of MMT and the particle concentration in incubation. Such a novel formulation is expected to possess extended residence time in the gastrointestinal (GI) tract, which promotes oral delivery of paclitaxel.

Back to Top

Development of efficient packaging method of oligodeoxynucleotides by a condensed nano particle in lipid envelope structure.
Yamada Y, Kogure K, Nakamura Y, Inoue K, Akita H, Nagatsugi F, Sasaki S, Suhara T, Harashima H.
Biol Pharm Bull. 2005 Oct;28(10):1939-42.
[ expand abstract ]

An efficient delivery system is required if antisense oligodeoxynucleotides (ODN) are to be utilized for gene therapy. We report herein on the development of a novel ODN delivery system, ODN-encapsulated nano particles (ODN-ENP) using an efficient and simple packaging method. The ODN-ENP consists of a condensed ODN particle and a lipid envelope, which can be equipped with various functional devices for the efficient delivery of ODN with a small diameter (150 nm). The encapsulation efficiency and ODN recovery of ODN-ENP were significantly higher than those of other packaging methods, such as a stabilized antisense-lipid particles method or a freeze-thaw method. Furthermore, the time required for the preparation of the ODN-ENP was shorter than the other methods. The method developed in this study is a simple and efficient packaging method for ODN with a condensed nano particle in lipid-envelope structure.

Tailoring Aqueous Solubility of Functionalized Single-Wall Carbon Nanotubes over a Wide pH Range through Substituent Chain Length.
Zeng L, Zhang L, Barron AR.
Nano Lett. 2005 Oct;5(10):2001-4.
[ expand abstract ]

Carboxylic acid-functionalized SWNTs prepared via the reaction of an amino acid, NH(2)(CH(2))(n)()CO(2)H, with fluoronanotubes show similar levels of sidewall functionalization; however, the solubility in water is controlled by the length of the hydrocarbon side chain (i.e., n). The 6-aminohexanoic acid derivative is soluble in aqueous solution (0.5 mg mL(-1)) between pH 4 and 11, whereas the glysine and 11-aminoundecanoic acid derivatives are insoluble across all pH values.

Back to Top

Development and characterization of sub-micron poly(d,l-lactide-co-glycolide) particles loaded with magnetite/maghemite nanoparticles.
Ngaboni Okassa L, Marchais H, Douziech-Eyrolles L, Cohen-Jonathan S, Souce M, Dubois P, Chourpa I.
Int J Pharm. 2005 Sep 30;302(1-2):187-196.
[ expand abstract ]

PURPOSE:: The objective of this study is to develop biodegradable sub-micron poly(lactide-co-glycolide) particles loaded with magnetite/maghemite nanoparticles for intravenous drug targeting. METHOD:: Sub-micron magnetite/PLGA particles (also called composite nanoparticles) were prepared by a modified double emulsion method (w/o/w) or by an emulsion-evaporation process (o/w). To optimize the composite nanoparticles formulation, the influence of some experimental parameters, such as types of magnetite/maghemite nanoparticles, volume of magnetite suspension and amount of polymer were investigated. The morphology, size and zeta potential of the magnetite/PLGA nanoparticles were determined. The magnetite entrapment efficiency and magnetite content were assessed by dosing iron in the composite nanoparticles. RESULTS:: TEM photomicrographs showed that the composite nanoparticles were almost spherical in shape with a rather monomodal distribution in size. All composite nanoparticle formulations were found to have the mean diameter within the range of 268-327nm with polydispersity index within the range of 0.02-0.15. Magnetite nanoparticles coated with oleic acid showed more efficient entrapment (60%) as compared to uncoated magnetite nanoparticles (48%). In both cases, when the volume of magnetite suspension increased, the magnetite entrapment efficiency decreased but the magnetite content increased. In addition, the two-fold rise in the amount of polymer did not significantly affect the composite nanoparticle characteristics except the magnetite content. Finally, none modification of the mean diameter of the composite nanoparticles was observed after storage for 3 months at 4 degrees C. CONCLUSIONS:: Magnetite/PLGA nanoparticles were prepared and the influence of some process parameters have been assessed. Improvement of the magnetite entrapment efficiency are in progress and the magnetization properties of the composite nanoparticles will subsequently be tested.

Effect of enzymatic degradation on the release kinetics of model drug from Pluronic F127/poly(lactic acid) nano-particles.
Xiong XY, Tam KC, Gan LH.
J Control Release. 2005 Sep 28; [Epub ahead of print] .
[ expand abstract ]

Poly(lactic acid) (PLA) was successfully grafted to both ends of Pluronic F127 block copolymer (PEO-PPO-PEO) to obtain amphiphilic PLA-F127-PLA block copolymers. The effect of enzymatic degradation on the release behaviors of hydrophobic model drug 9-(methylaminomethyl)anthracene (MAMA) from PLA-F127-PLA nano-particles with vesicular structure was studied by UV-Vis spectroscopy. It was observed that the release rate of MAMA from PLA-F127-PLA nano-particles with the enzymatic degradation varied with temperature due to the activity of the enzyme with temperature. However, the enzyme concentration has negligible effect on the release rates of MAMA.

Back to Top

Poly(amidoamine) dendrimer-based multifunctional engineered nanodevice for cancer therapy.
Majoros IJ, Thomas TP, Mehta CB, Baker JR Jr.
J Med Chem. 2005 Sep 22;48(19):5892-9.
[ expand abstract ]

Multifunctional cancer therapeutic nanodevices have been designed and synthesized using the poly(amidoamine) (PAMAM) dendrimer as a carrier. Partial acetylation of the generation 5 (G5) PAMAM dendrimer was utilized to neutralize a fraction of the primary amino groups, provide enhanced solubility of the dendrimer during the conjugation reaction of fluorescein isothiocyanate (FITC) (in dimethyl sulfoxide (DMSO)), and prevent nonspecific targeting interactions (in vitro and in vivo) during delivery. The remaining nonacetylated primary amino groups were utilized for conjugation of the functional molecules fluorescein isothiocyanate (FITC, an imaging agent), folic acid (FA, targets overexpressed folate receptors on specific cancer cells), and methotrexate (MTX, chemotherapeutic drug). The appropriate control nanodevices have been synthesized as well. The G5 PAMAM dendrimer molecular weight and number of primary amino groups were determined by gel permeation chromatography (GPC) and potentiometric titration for stoichiometric design of ensuing conjugation reactions. Additionally, dendrimer conjugates were characterized by multiple analytical methods including GPC, nuclear magnetic resonance spectroscopy (NMR), high performance liquid chromatography (HPLC), and UV spectroscopy. The fully characterized nanodevices can be used for the targeted delivery of chemotherapeutic and imaging agents to specific cancer cells. Here, we present a more extensive investigation of our previously reported synthesis of this material with improvements directed toward scale-up synthesis and clinical trials.

Functionalization of Carbon Nanotubes via Cleavable Disulfide Bonds for Efficient Intracellular Delivery of siRNA and Potent Gene Silencing.
Kam NW, Liu Z, Dai H.
J Am Chem Soc. 2005 Sep 14;127(36):12492-3.
[ expand abstract ]

We present a novel functionalization scheme for single-walled carbon nanotubes (SWNTs) to afford nanotube-biomolecule conjugates with the incorporation of cleavable bonds to enable controlled molecular releasing from nanotube surfaces, thus creating "smart" nanomaterials with high potential for chemical and biological applications. With this versatile functionalization, we demonstrate transporting, enzymatic cleaving and releasing of DNA from SWNT transporters, and subsequent nuclear translocation of DNA oligonucleotides in mammalian cells. We further show highly efficient delivery of siRNA by SWNTs and achieving more potent RNAi functionality than a widely used conventional transfection agent. Thus, the novel functionalization of SWNTs with cleavable bonds is highly promising for a wide range of applications including gene and protein therapy

Back to Top

Defined DNA/nanoparticle conjugates.
Ackerson CJ, Sykes MT, Kornberg RD.
Proc Natl Acad Sci U S A. 2005 Sep 9; [Epub ahead of print] .
[ expand abstract ]

Glutathione monolayer-protected gold clusters were reacted by place exchange with 19- or 20-residue thiolated oligonucleotides. The resulting DNA/nanoparticle conjugates could be separated on the basis of the number of bound oligonucleotides by gel electrophoresis and assembled with one another by DNA-DNA hybridization. This approach overcomes previous limitations of DNA/nanoparticle synthesis and yields conjugates that are precisely defined with respect to both gold and nucleic acid content.

A modular nanoparticle-based system for reagentless small molecule biosensing.
Sandros MG, Gao D, Benson DE.
J Am Chem Soc. 2005 Sep 7;127(35):12198-9.
[ expand abstract ]

Metalloprotein tethered CdSe nanoparticles have been generated to provide selective and reagentless maltose biosensing. As opposed to cell or protein detection by semiconducting nanoparticle bioconjugates, a modular method for small-molecule detection using semiconducting nanoparticle bioconjugates has been difficult. Here we report a method for reagentless protein-based semiconducting nanoparticle biosensors. This method uses Ru(II) complex-CdSe nanoparticle interactions and the maltose-induced conformation changes of maltose binding protein to alter the CdSe nanoparticle fluorescence emission intensity. In this proof-of-principle system, the maltose-induced protein conformation changes alter the Ru(II) complex-CdSe nanoparticle interaction, which increases the CdSe emission intensity. Altered CdSe emission intensity effects are best described as electron transfer from the Ru(II) complex to the CdSe excited state forming the nonfluorescent CdSe anion. Four surface-cysteine, Ru(II) complex-attached maltose-binding proteins have been studied for maltose dependent alteration of CdSe emission intensities. With 3.0-3.5 nm diameter CdSe nanoparticles, all ruthenated maltose-binding proteins display similar maltose-dependent increases (1.4-fold) in CdSe emission intensity and maltose binding affinities (K(A) = 3 x 10(6) M(-1)). For these four systems, the only difference was the sample-to-sample variation in maltose-dependent responses. Thus, very few surface cysteine mutations need to be examined to find a successful biosensor, as opposed to analogous systems using organic fluorophores. This strategy generates a unimolecular, or reagentless, semiconducting nanoparticle biosensor for maltose, which could be applied to other proteins with ligand-dependent conformation changes.

Back to Top

Semiconductor nanocrystals for biological imaging.
Fu A, Gu W, Larabell C, Alivisatos AP.
Curr Opin Neurobiol. 2005 Sep 5; [Epub ahead of print] .
[ expand abstract ]

Conventional organic fluorophores suffer from poor photo stability, narrow absorption spectra and broad emission spectra. Semiconductor nanocrystals, however, are highly photo-stable with broad absorption spectra and narrow size-tunable emission spectra. Recent advances in the synthesis of these materials have resulted in the generation of bright, sensitive, extremely photo-stable and biocompatible semiconductor fluorophores. Commercial availability facilitates their application in a variety of unprecedented biological experiments, including multiplexed cellular imaging, long-term in vitro and in vivo labeling, deep tissue structure mapping and single particle investigation of dynamic cellular processes. Semiconductor nanocrystals are one of the first examples of nanotechnology enabling a new class of biomedical applications.

An adaptable microvalving system for on-chip polymerase chain reactions.
Pilarski PM, Adamia S, Backhouse CJ.
J Immunol Methods. 2005 Sep 5; [Epub ahead of print] .
[ expand abstract ]

On-chip genetic analysis systems are beginning to provide a viable alternative to conventional gene profiling and amplification devices, through minimal reagent use, high detection resolution, and the potential for high-throughput parallel testing of the genetic material, even from single cells. Despite the advantages, there are many difficulties inherent in creating an integrated microfluidic diagnostic platform. One major challenge is the accurate control and manipulation of fluid, and particularly the immobilization of reaction mixtures during heating phases of polymerase chain reactions (PCR). In this paper we present a pumping and valving system based on the use of three servomotor-controlled valve fingers that actuate microchannels within a poly-dimethylsiloxane (PDMS) fluidic chip. We characterize the valving ability of the system in terms of fluid loss and show the successful fluid retention of the system over 35-cycle PCR runs at temperatures of up to approximately 96 degrees C. In addition, we demonstrate the system's ability to perform PCR by successfully amplifying a sample of beta2 microglobulin transcript obtained from the peripheral blood of a patient with multiple myeloma. This work has proven to be a successful approach to multi-use valving and a viable method of alleviating the fluid control difficulties inherent in performing a PCR reaction in an on-chip environment. In addition, it opens the door for further automation and integration with other chip-based genetic analysis platforms.

Back to Top

Development of a microfluidic platform with an optical imaging microarray capable of attomolar target DNA detection.
Bowden M, Song L, Walt DR.
Anal Chem. 2005 Sep 1;77(17):5583-8.
[ expand abstract ]

In this paper, DNA hybridization in a microfluidic manifold is performed using fluorescence detection on a fiber-optic microarray. The microfluidic device integrates optics, sample transport, and fluidic interconnects on a single platform. A high-density optical imaging fiber array containing oligonucleotide-labeled microspheres was developed. DNA hybridization was observed at concentrations as low as 10 aM with response times of less than 15 min at a flow rate of 1 microL/min using 50 microL of target DNA samples. The fast response times coupled with the low sample volumes and the use of a high-density, fiber-optic microarray format make this method highly advantageous. This paper describes the initial development, optimization, and integration of the microfluidic platform with imaging fiber arrays.

Microfluidic system for studying the interaction of nanoparticles and microparticles with cells.
Farokhzad OC, Khademhosseini A, Jon S, Hermmann A, Cheng J, Chin C, Kiselyuk A, Teply B, Eng G, Langer R.
Anal Chem. 2005 Sep 1;77(17):5453-9.
[ expand abstract ]

Nanoparticles and microparticles have many potential biomedical applications ranging from imaging to drug delivery. Therefore, in vitro systems that can analyze and optimize the interaction of such particles with cells may be beneficial. Here, we report a microfluidic system that can be used to study these interactions. As a model system, we evaluated the interaction of polymeric nanoparticles and microparticles and similar particles conjugated to aptamers that recognize the transmembrane prostate specific membrane antigen (PSMA), with cells seeded in microchannels. The binding of particles to cells that expressed or did not express the PSMA (LNCaP or PC3, respectively) were evaluated with respect to changes in fluid shear stress, PSMA expression on target cells, and particle size. Nanoparticle-aptamer bioconjugates selectively adhered to LNCaP but not PC3 cells at static and low shear (<1 dyn/cm2) but not higher shear (approximately 4.5 dyn/cm2) conditions. Control nanoparticles and microparticles lacking aptamers and microparticle-aptamer bioconjugates did not adhere to LNCaP cells, even under very low shear conditions (approximately 0.28 dyn/cm2). These results demonstrate that the interaction of particles with cells can be studied under controlled conditions, which may aid in the engineering of desired particle characteristics. The scalability, low cost, reproducibility, and high-throughput capability of this technology is potentially beneficial to examining and optimizing a wide array of cell-particle systems prior to in vivo experiments.

Back to Top

Collagen-carbon nanotube composite materials as scaffolds in tissue engineering.
MacDonald RA, Laurenzi BF, Viswanathan G, Ajayan PM, Stegemann JP.
J Biomed Mater Res A. 2005 Sep 1;74(3):489-96.
[ expand abstract ]

Carbon nanotubes (CNT) are attractive for use in fiber-reinforced composite materials due to their very high aspect ratio, combined with outstanding mechanical and electrical properties. Composite materials comprising a collagen matrix with embedded CNT were prepared by mixing solubilized Type I collagen with solutions of carboxylated single-walled carbon nanotubes (SWNT) at concentrations of 0, 0.2, 0.4, 0.8, and 2.0 weight percent. Living smooth muscle cells were incorporated at the time of collagen gelation to produce cell-seeded collagen-CNT composite matrices. Constructs containing 2.0 wt % CNT exhibited delayed gel compaction, relative to lower concentrations that compacted at the same rate as pure collagen controls. Cell viability in all constructs was consistently above 85% at both Day 3 and Day 7, whereas cell number in CNT-containing constructs was lower than in control constructs at Day 3, though statistically unchanged by Day 7. Scanning electron microscopy showed physical interactions between CNT and collagen matrix. Raman spectroscopy confirmed the presence of CNT at the expected diameter (0.85-1.30 nm), but did not indicate strong molecular interactions between the collagen and CNT components. Such collagen-CNT composite matrices may have utility as scaffolds in tissue engineering, or as components of biosensors or other medical devices.

Microarray-based detection of protein binding and functionality by gold nanoparticle probes.
Wang Z, Lee J, Cossins AR, Brust M.
Anal Chem. 2005 Sep 1;77(17):5770-4.
[ expand abstract ]

We report a microarray format for the detection of proteins and protein functionality (kinase activity) based on marking either specific antibody-protein binding or peptide phosphorylation events by attachment of gold nanoparticles followed by silver deposition for signal enhancement. The attachment of the gold nanoparticles is achieved by standard avidin-biotin chemistry. The detection principle is resonance light scattering. Highly selective recognition of standard proteins (proteins A and G) down to 1 pg/mL for proteins in solution and 10 fg for proteins on the microarray spots is demonstrated. Enzyme activity of the kinase (PKA) is detected with high specificity down to a limit of 1 fg for an established peptide substrate (kemptide) on the microarray spots. Kinase inhibition by the inhibitor (H89) is shown, demonstrating the potential for high-throughput screening for inhibitors.

Back to Top

Rapid Fabrication and Chemical Patterning of Polymer Microstructures and their Applications as a Platform for Cell Cultures.
Faid K, Voicu R, Bani-Yaghoub M, Tremblay R, Mealing G, Py C, Barjovanu R.
Biomed Microdevices. 2005 Sep;7(3):179-84.
[ expand abstract ]

Much of the current knowledge regarding biological processes has been obtained through in-vitro studies in bulk aqueous solutions or in conventional Petri-dishes, with neither methodology accurately duplicating the actual in-vivo biological processes. Recently, a number of innovative approaches have attempted to address these shortcomings by providing substrates with controlled features. In particular, tunable surface chemistries and topographical micro and nanostructures have been used as model systems to study the complex biological processes. We herein report a versatile and rapid fabrication method to produce a variety of microstructured polymer substrates with precise control and tailoring of their surface chemistries. A poly(dimethylsiloxane) (PDMS) substrate, produced by replication over a master mold with specific microstructures, is modified by a fluoro siloxane derivative to enhance its anti-adhesion characteristics and used as a secondary replication mold. A curable material, deposited by spin coating on various substrates, is stamped with the secondary mold and crosslinked. The removal of the secondary mold produces a microstructured surface with the same topographical features as the initial master mold. The facile chemical patterning of the microstructured substrates is demonstrated through the use of microcontact printing methods and these materials are tested as a platform to guide cell attachment, growth and proliferation. The master mold and flexible fluorinated PDMS stamps can be used in a repeated manner without any degradation of the anti-adhesion characteristics opening the way to the development of high-throughput fabrication methods that can yield reliable and inexpensive microstructured and chemically patterned substrates.

A simple microfluidic system for efficient capillary electrophoretic separation and sensitive fluorimetric detection of DNA fragments using light-emitting diode and liquid-core waveguide techniques.
Wang SL, Fan XF, Xu ZR, Fang ZL.
Electrophoresis. 2005 Aug 31; [Epub ahead of print] .
[ expand abstract ]

A miniaturized CE system has been developed for fast DNA separations with sensitive fluorimetric detection using a rectangle type light-emitting diode (LED). High sensitivity was achieved by combining liquid-core waveguide (LCW) and lock-in amplification techniques. A Teflon AF-coated silica capillary on a compact 6x3 cm baseplate served as both the separation channel for CE separation and as an LCW for light transmission of fluorescence emission to the detector. An electronically modulated LED illuminated transversely through a 0.2 mm aperture, the detection point on the LCW capillary without focusing, and fluorescence light was transmitted to the capillary outlet. To simplify the optics and enhance collection of light from the capillary outlet, an outlet reservoir was designed, with a light transmission window, positioned directly in front of a photomultiplier tube (PMT), separated only by a high pass filter. Automated sample introduction was achieved using a sequential injection system through a split-flow interface that allowed effective release of gas bubbles. In the separation of a PhiX174 HaeIII DNA digest sample, using ethidium bromide as labeling dye, all 11 fragments of the sample were effectively resolved in 400 s, with an S/N ratio comparable to that of a CE system with more sophisticated LIF.

Back to Top

Electrospray interfacing of polymer microfluidics to MALDI-MS.
Wang YX, Zhou Y, Balgley BM, Cooper JW, Lee CS, Devoe DL.
Electrophoresis. 2005 Aug 31; [Epub ahead of print] .
[ expand abstract ]

The off-line coupling of polymer microfluidics to MALDI-MS is presented using electrospray deposition. Using polycarbonate microfluidic chips with integrated hydrophobic membrane electrospray tips, peptides and proteins are deposited onto a stainless steel target followed by MALDI-MS analysis. Microchip electrospray deposition is found to yield excellent spatial control and homogeneity of deposited peptide spots, and significantly improved MALDI-MS spectral reproducibility compared to traditional target preparation methods. A detection limit of 3.5 fmol is demonstrated for angiotensin. Furthermore, multiple electrospray tips on a single chip provide the ability to simultaneously elute parallel sample streams onto a MALDI target for high-throughput multiplexed analysis. Using a three-element electrospray tip array with 150 microm spacing, the simultaneous deposition of bradykinin, fibrinopeptide, and angiotensin is achieved with no cross talk between deposited samples. In addition, in-line proteolytic digestion of intact proteins is successfully achieved during the electrospray process by binding trypsin within the electrospray membrane, eliminating the need for on-probe digestion prior to MALDI-MS. The technology offers promise for a range of microfluidic platforms designed for high-throughput multiplexed proteomic analyses in which simultaneous on-chip separations require an effective interface to MS.

Self-made frits for nanoscale columns in proteomics.
Maiolica A, Borsotti D, Rappsilber J.
Proteomics. 2005 Aug 30; [Epub ahead of print] .
[ expand abstract ]

We report here the production of self-made frits for nano-columns. The frits introduce a minor dead volume and can be placed in capillaries with a wide range of diameters (20-250 microm tested) in an extremely simple and low-cost procedure. The obtained columns appear to be comparable to "no-frit" columns with near-ideal chromatographic characteristics. We expect that this frit will be useful for the spotting of gradients onto MALDI plates but also where special ESI set-ups do not allow for "no-frit" solutions.

Back to Top

Turning all the lights on: quantum dots in cellular assays.
Bruchez MP.
Curr Opin Chem Biol. 2005 Aug 24; [Epub ahead of print] .
[ expand abstract ]

Quantum dot materials are increasingly used in cellular assays, and offer a powerful and enabling complement to existing methods of labeling proteins, such as green fluorescent protein. These materials give researchers the ability to study specificity and functional responses in cellular systems, in a highly multiplexed manner, at either a molecular or cellular level. The recent literature bears witness to the increasing use of quantum dots for the investigation of chemicals on biological systems, and paves the way to the use of these assays for high-throughput analysis of functional responses in relevant models at scales including molecular, cellular and whole animal.

A conductive ormosil encapsulated with ferrocene conjugate and multiwall carbon nanotubes for biosensing application.
Kandimalla VB, Tripathi VS, Ju H.
Biomaterials. 2005 Aug 23; [Epub ahead of print] .
[ expand abstract ]

Highly non-toxic and conductive ormosil composite film was prepared using (3-aminopropyl)triethoxysilane and 2-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane by doping with ferrocenemonocarboxylic acid-bovine serum albumin (FMC-BSA) conjugate and multiwall carbon nanotubes (MWNTs). With glucose oxidase (GOD) as a model enzyme this film could be used to design an amperometric biosensor for glucose determination. The entrapped FMC-BSA conjugate performed excellent redox electrochemistry and the immobilized GOD was highly stable. Under optimal conditions this biosensor was able to detect glucose with a detection limit of 20mum (S/N=3) in the linear range of 0.05-20.0mm in flow system, which was wider than the batch amperometric mode, with an analysis time of 25s for each sample. The value of K(M)(app) was 6.6mm. The proximity of these three components FMC-BSA, MWNTs and GOD enhanced the electron transfer between the film and electrode. This film could be used efficiently for the entrapment of other redox bioactive compounds and biosensing/bioelectrochemical applications.

Back to Top

Quantum dot-conjugated hybridization probes for preliminary screening of siRNA sequences.
Bakalova R, Zhelev Z, Ohba H, Baba Y.
J Am Chem Soc. 2005 Aug 17;127(32):11328-35.
[ expand abstract ]

In the present study, we describe the design and fabrication of quantum dot-conjugated hybridization probes and their application to the development of a comparatively simple and rapid procedure for the selection of highly effective small-interfering RNA (siRNA) sequences for RNA interference (RNAi) in mammalian cells, for example, siRNAs with high accessibility and affinity to the respective mRNA target. A single-stranded siRNA was conjugated with a quantum dot and used as a hybridization probe. The target mRNA was amplified in the presence of Cy5-labeled nucleotides, and Cy5-mRNA served as a hybridization sample. The formation of siRNA/mRNA duplexes during a comparatively short hybridization time (1 h) was used as a criterion for the selection of highly effective, target-specific siRNA sequences. The accessibility and affinity of the siRNA sequence for the target mRNA site were determined by fluorescence resonance energy transfer (FRET) between a quantum dot (donor) and a fluorescent dye molecule (Cy5, acceptor) localized at an appropriate distance from each other when hybridization occurred. The FRET signal was observed only when there was high accessibility between an antisense siRNA and a sense mRNA and did not appear in the case of mismatch siRNAs. Moreover, the amplitude of the FRET signal significantly correlated with the specific effect of siRNA on the expression of the target mRNA and protein, determined in native cells by RT-PCR and immunoblot analysis, respectively.

Microfluidic Device for Rapid (<15 min) Automated Microarray Hybridization.
Peytavi R, Raymond FR, Gagne D, Picard FJ, Jia G, Zoval J, Madou M, Boissinot K, Boissinot M, Bissonnette L, Ouellette M, Bergeron MG.
Clin Chem. 2005 Aug 17; [Epub ahead of print] .
[ expand abstract ]

METHODS: We have developed a microfluidic flow cell consisting of a network of chambers and channels molded into a polydimethylsiloxane substrate. The substrate was aligned and bound in reverse to the microarray printed onto a standard glass slide to form a functional microfluidic unit. The microfluidic units were placed onto an engraved, disc-shaped support fixed on a rotational device. Centrifugal forces drove the sample and buffers directly onto the microarray surface. RESULTS: This microfluidic system allowed us to increase the hybridization signal by approximately 10fold compared with a passive system that made use of 10 times less sample. By means of a 15-min automated hybridization process, performed at room temperature, we demonstrated the discrimination of 4 clinically relevant Staphylococcus species that differ by as little as a single nucleotide polymorphism (SNP). This process included hybridization, washing, rinsing, and drying steps and does not require any purification of target nucleic acids. This platform was sensitive enough to detect 10 PCR-amplified bacterial genomes. CONCLUSION: This microfluidic system for removing microarray hybridization onto glass slides is promising for molecular diagnostics and gene profiling

Back to Top

Cationic liposome-microtubule complexes: Pathways to the formation of two-state lipid-protein nanotubes with open or closed ends.
Raviv U, Needleman DJ, Li Y, Miller HP, Wilson L, Safinya CR.
Proc Natl Acad Sci U S A. 2005 Aug 9;102(32):11167-72.
[ expand abstract ]

Intermolecular interactions between charged membranes and biological polyelectrolytes, tuned by physical parameters, which include the membrane charge density and bending rigidity, the membrane spontaneous curvature, the biopolymer curvature, and the overall charge of the complex, lead to distinct structures and morphologies. The self-assembly of cationic liposome-microtubule (MT) complexes was studied, using synchrotron x-ray scattering and electron microscopy. Vesicles were found to either adsorb onto MTs, forming a "beads on a rod" structure, or undergo a wetting transition and coating the MT. Tubulin oligomers then coat the external lipid layer, forming a tunable lipid-protein nanotube. The beads on a rod structure is a kinetically trapped state. The energy barrier between the states depends on the membrane bending rigidity and charge density. By controlling the cationic lipid/tubulin stoichiometry it is possible to switch between two states of nanotubes with either open ends or closed ends with lipid caps, a process that forms the basis for controlled chemical and drug encapsulation and release.

HPLC analysis of PAMAM dendrimer based multifunctional devices.
Islam MT, Majoros IJ, Baker JR Jr.
J Chromatogr B Analyt Technol Biomed Life Sci. 2005 Aug 5;822(1-2):21-6.
[ expand abstract ]

Comprehensive high-performance liquid chromatography (HPLC) analyses were performed on poly(amidoamine) (PAMAM) dendrimer based multifunctional devices. The nanometer-size devices were synthesized by conjugating partially acetylated (Ac) poly(amidoamine) dendrimers of generation 5 (G5) with fluorescein isothiocyanate (FITC), folic acid (FA) and methotrexate (MTX). The devices are intended for targeted intracellular drug delivery to tumor cells through the folate receptor. Methods were developed for detection and separation of various surface functionalized dendrimer conjugates and small molecules (FITC, FA, MTX) using a common gradient. Results indicate that the HPLC technique can be used as a quality control tool for determining purity of the G5 carrier, its acetylated form, and mono-, bi- and tri-functional nanodevices. More importantly, the chromatograms of these novel nanodevices, reported for the first time, provide information on critical properties such as polydispersity, surface heterogeneity and solubility. The benchmark data can be used to optimize the physicochemical properties of the conjugates to improve drug delivery to cancer cells.

Back to Top

Torque-actuated valves for microfluidics.
Weibel DB, Kruithof M, Potenta S, Sia SK, Lee A, Whitesides GM.
Anal Chem. 2005 Aug 1;77(15):4726-33.
[ expand abstract ]

This paper describes torque-actuated valves for controlling the flow of fluids in microfluidic channels. The valves consist of small machine screws (>/=500 mum) embedded in a layer of polyurethane cast above microfluidic channels fabricated in poly(dimethylsiloxane) (PDMS). The polyurethane is cured photochemically with the screws in place; on curing, it bonds to the surrounding layer of PDMS and forms a stiff layer that retains an impression of the threads of the screws. The valves were separated from the ceiling of microfluidic channels by a layer of PDMS and were integrated into channels using a simple procedure compatible with soft lithography and rapid prototyping. Turning the screws actuated the valves by collapsing the PDMS layer between the valve and channel, controlling the flow of fluids in the underlying channels. These valves have the useful characteristic that they do not require power to retain their setting (on/off). They also allow settings between "on" and "off" and can be integrated into portable, disposable microfluidic devices for carrying out sandwich immunoassays.

Self-assembled lipid superstructures: beyond vesicles and liposomes.
Barauskas J, Johnsson M, Tiberg F.
Nano Lett. 2005 Aug;5(8):1615-9.
[ expand abstract ]

A unique set of nanoparticle dispersions of self-assembled lipid mesophases with distinctive reversed cubic, hexagonal, and sponge phase structures has been prepared by use of original lipid combinations and a simple, generally applicable and scalable method. All key properties, particle size distributions, shape, phase structure, and stability, are controlled predictably and reproducibly. The results suggest the cross-disciplinary use of nonlamellar particle structures in science and technology as, for instance, biomimetics, in vivo drug delivery vehicles for diagnostic and therapeutic agents, protein crystallization matrices, and soft nanoporous materials.

Back to Top

Multipurpose microfluidic probe.
Juncker D, Schmid H, Delamarche E.
Nat Mater. 2005 Aug;4(8):622-8.
[ expand abstract ]

Microfluidic systems allow (bio)chemical processes to be miniaturized with the benefit of shorter time-to-result, parallelism, reduced sample consumption, laminar flow, and increased control and efficiency. However, such miniaturization inherently limits the size of the solid objects that can be processed and entails new challenges such as the interfacing of macroscopic samples with microscopic conduits. Here, we report a microfluidic probe (MFP) that overcomes these problems by combining the concepts of 'microfluidics' and of 'scanning probes'. Here, liquid boundaries formed by hydrodynamic forces underneath the MFP confine a flow of processing solution and replace the solid walls of closed microchannels. The MFP is therefore mobile and can be used to process large surfaces and objects by scanning across them. We illustrate the versatility of this concept with several examples including protein microarraying, complex gradient-formation, multiphase laminar-flow patterning, erasing, localized staining of cells and the contact-free detachment of a single cell. Many constraints imposed by the monolithic construction of microfluidic channels can now be circumvented using an MFP, opening up new avenues for microfluidic processing.

World-to-chip microfluidic interface with built-in valves for multichamber chip-based PCR assays.
Oh KW, Park C, Namkoong K, Kim J, Ock KS, Kim S, Kim YA, Cho YK, Ko C.
Lab Chip. 2005 Aug;5(8):845-50.
[ expand abstract ]

We report a practical world-to-chip microfluidic interfacing method with built-in valves suitable for microscale multichamber chip-based assays. One of the primary challenges associated with the successful commercialization of fully integrated microfluidic systems has been the lack of reliable world-to-chip microfluidic interconnections. After sample loading and sealing, leakage tests were conducted at 100 degrees C for 30 min and no detectable leakage flows were found during the test for 100 microchambers. To demonstrate the utility of our world-to-chip microfluidic interface, we designed a microscale PCR chip with four chambers and performed PCR assays. The PCR results yielded a 100% success rate with no contamination or leakage failures. In conclusion, we have introduced a simple and inexpensive microfluidic interfacing system for both sample loading and sealing with no dead volume, no leakage flow and biochemical compatibility.

Back to Top

Hydrophobic dendrimer-derived nanoparticles.
Singh B, Florence AT.
Int J Pharm. 2005 Jul 25;298(2):348-53.
[ expand abstract ]

Lipidic polylysine dendrimers, synthesized using Fmoc solid phase peptide techniques, have been formulated as nanoparticles by precipitation from solution in dichloromethane. The effect of concentration on the diameter and stability of nanoparticles formed from two short homologous series of dendrimers--one fifth generation and one sixth generation series and with surface C4, C10 or C12 groups--was investigated using photon correlation spectroscopy. The increase in generation from fifth to sixth resulted in increased diameter for each chain length. An increase in the surface lipidic chain length from C4 to C12 had no effect on the particle diameter of aggregates derived from fifth generation dendrimers, and a small and variable effect on the sixth generation derived nanoparticles. Using pyrene (excitation 340 nm) as a hydrophobic fluorescent probe, a decrease in intensity peak I1 (374 nm)/I3 (385 nm) in the emission spectra (340-600 nm) was observed in the two dendrimers studied, fifth generation dendrimers with C10 or C12 surface lipidic chains, as the dendrimer concentration increased, reaching a plateau at higher concentrations, indicating that a more compact form of the aggregates with a more hydrophobic interior was obtained. Apart from the hydrophobicity of the dendrimers and dendrimer concentration, the flexibility of the dendrimers might have a significant effect in determining nanoparticle size. The aggregates derived from the fifth generation dendrimers with C10 or C12 surface lipidic chains are stable in purified intestinal fluid but not in purified stomach fluid, in which further aggregation of the nanoparticulate dendrimer aggregates occurs as an effect of pH, salts, proteins and enzymes in these fluids. This study demonstrates, inter alia, the importance of testing nanoparticulate delivery systems in relevant physiologically based fluids prior to their use in vivo.

HaloTag protein-mediated site-specific conjugation of bioluminescent proteins to quantum dots.
Zhang Y, So MK, Loening AM, Yao H, Gambhir SS, Rao J.
Angew Chem Int Ed Engl. 2006 Jul 24;45(30):4936-40.
[ expand abstract ]

No abstract available

A reversible molecular valve.
Nguyen TD, Tseng HR, Celestre PC, Flood AH, Liu Y, Stoddart JF, Zink JI.
Proc Natl Acad Sci U S A. 2005 Jul 19;102(29):10029-34.
[ expand abstract ]

In everyday life, a macroscopic valve is a device with a movable control element that regulates the flow of gases or liquids by blocking and opening passageways. Construction of such a device on the nanoscale level requires (i) suitably proportioned movable control elements, (ii) a method for operating them on demand, and (iii) appropriately sized passageways. These three conditions can be fulfilled by attaching organic, mechanically interlocked, linear motor molecules that can be operated under chemical, electrical, or optical stimuli to stable inorganic porous frameworks (i.e., by self-assembling organic machinery on top of an inorganic chassis). In this article, we demonstrate a reversibly operating nanovalve that can be turned on and off by redox chemistry. It traps and releases molecules from a maze of nanoscopic passageways in silica by controlling the operation of redox-activated bistable [2]rotaxane molecules tethered to the openings of nanopores leading out of a nanoscale reservoir.

Back to Top

Million-fold preconcentration of proteins and peptides by nanofluidic filter.
Wang YC, Stevens AL, Han J.
Anal Chem. 2005 Jul 15;77(14):4293-9.
[ expand abstract ]

We have developed a highly efficient microfluidic sample preconcentration device based on the electrokinetic trapping mechanism enabled by nanofluidic filters. The device, fabricated by standard photolithography and etching techniques, generates an extended space charge region within a microchannel, which was used to both collect and trap the molecules efficiently. The electrokinetic trapping and collection can be maintained for several hours, and concentration factors as high as 10(6)-10(8) have been demonstrated. This device could be useful in various bioanalysis microsystems, due to its simplicity, performance, robustness, and integrabilty to other separation and detection systems.

Biocompatible and Biodegradable Polymer Nanofibers Displaying Superparamagnetic Properties.
Tan ST, Wendorff JH, Pietzonka C, Jia ZH, Wang GQ.
Chemphyschem. 2005 Jul 11; [Epub ahead of print].
[ expand abstract ]

Superparamagnetic polymer nanofibers intended for drug delivery and therapy are considered here. Magnetite (Fe(3)O(4)) nanoparticles in the diameter range of 5-10 nm were synthesized in aqueous solution. Polymer nanofibers containing magnetite nanoparticles were prepared from commercially available poly(hydroxyethyl methacrylate), PHEMA, and poly-L-lactide (PLLA) by the electrospinning technique. Nanofibers with diameters ranging from 50 to 300 nm were obtained. Nanofibers containing up to 35 wt % magnetite nanoparticles displayed superparamagnetism at room temperature. The blocking temperature was about 50 K for an applied field of 500 Oe, and the saturation magnetization was 3.5 emu g(-1) and 1.1 emu g(-1) for Fe(3)O(4)/PHEMA and Fe(3)O(4)/PLLA nanofibers, respectively, and depended on the amount of Fe(3)O(4) nanoparticles in the nanocomposites. To test such magnetic nano-objects for applications as drug carriers and drug-release systems we incorporated a fluorescent albumin with dog fluorescein isothiocyanate (ADFI).

A reversible molecular valve.
Nguyen TD, Tseng HR, Celestre PC, Flood AH, Liu Y, Stoddart JF, Zink JI.
Proc Natl Acad Sci U S A. 2005 Jul 8; [Epub ahead of print].
[ expand abstract ]

In everyday life, a macroscopic valve is a device with a movable control element that regulates the flow of gases or liquids by blocking and opening passageways. Construction of such a device on the nanoscale level requires (i) suitably proportioned movable control elements, (ii) a method for operating them on demand, and (iii) appropriately sized passageways. These three conditions can be fulfilled by attaching organic, mechanically interlocked, linear motor molecules that can be operated under chemical, electrical, or optical stimuli to stable inorganic porous frameworks (i.e., by self-assembling organic machinery on top of an inorganic chassis). In this article, we demonstrate a reversibly operating nanovalve that can be turned on and off by redox chemistry. It traps and releases molecules from a maze of nanoscopic passageways in silica by controlling the operation of redox-activated bistable [2]rotaxane molecules tethered to the openings of nanopores leading out of a nanoscale reservoir.

Back to Top

In vitro Enzymatic Degradation of Nanoparticles Prepared from Hydrophobically-Modified Poly(gamma-glutamic acid).
Akagi T, Higashi M, Kaneko T, Kida T, Akashi M.
Macromol Biosci. 2005 Jun 30;5(7):598-602.
[ expand abstract ]

Amphiphilic poly(gamma-glutamic acid) (gamma-PGA) was prepared by the introduction of L-phenylalanine ethylester (L-PAE) as a side chain. This gamma-PGA-graft-L-PAE formed monodispersed nanoparticles in water. The particle size of the gamma-PGA nanoparticles could be controlled by the degree of L-PAE grafting. The hydrolytic degradation and enzymatic degradation by gamma-glutamyl transpeptidase (gamma-GTP) of these gamma-PGA nanoparticles was studied by gel permeation chromatography (GPC) and scanning electron microscopy (SEM). The hydrolysis ratio of gamma-PGA was found to decrease upon increasing the hydrophilicity of the gamma-PGA. The degradation of the gamma-PGA backbone by gamma-GTP resulted in a dramatic change in nanoparticle morphology. With increasing time, the gamma-PGA nanoparticles reduced in size and finally disappeared completely.Time-course of the changes in the morphology of the gamma-PGA nanoparticles following incubation with gamma-glutamyl transpeptidase.

Single-file electrophoretic transport and counting of individual DNA molecules in surfactant nanotubes.
Tokarz M, Akerman B, Olofsson J, Joanny JF, Dommersnes P, Orwar O.
Proc Natl Acad Sci U S A. 2005 Jun 28;102(26):9127-32.
[ expand abstract ]

We demonstrate a complete nanotube electrophoresis system (nanotube radii in the range of 50 to 150 nm) based on lipid membranes, comprising DNA injection, single-molecule transport, and single-molecule detection. Using gel-capped electrodes, electrophoretic single-file transport of fluorescently labeled dsDNA molecules is observed inside nanotubes. The strong confinement to a channel of molecular dimensions ensures a detection efficiency close to unity and identification of DNA size from its linear relation to the integrated peak intensity. In addition to constituting a nanotechnological device for identification and quantification of single macromolecules or biopolymers, this system provides a method to study their conformational dynamics, reaction kinetics, and transport in cell-like environments.

Back to Top

Wet STEM: A new development in environmental SEM for imaging nano-objects included in a liquid phase.
Bogner A, Thollet G, Basset D, Jouneau PH, Gauthier C.
Ultramicroscopy. 2005 Jun 27; [Epub ahead of print].
[ expand abstract ]

Environmental scanning electron microscopy (ESEM) enables wet samples to be observed without potentially damaging sample preparation through the use of partial water vapour pressure in the microscope specimen chamber. However, in the case of latices in colloidal state or microorganisms, samples are not only wet, but made of objects totally submerged in a liquid phase. In this case, under classical ESEM imaging conditions only the top surface of the liquid is imaged, with poor contrast, and possible drifting of objects. The present paper describes experiments using a powerful new Scanning Transmission Electron Microscopy (STEM) imaging system, that allows transmission observations of wet samples in an ESEM. A special device, designed to observe all sorts of objects submerged in a liquid under annular dark-field imaging conditions, is described. Specific features of the device enable to avoid drifting of floating objects which occurs in the case of a large amount of water, thus allowing slow-scan high-definition imaging of particles with a diameter down to few tens of nm. The large potential applications of this new technique are then illustrated, including the imaging of different nano-objects in water. The particular case of grafted latex particles is discussed, showing that it is possible to observe details on their surface when submerged in water. All the examples demonstrate that images acquired in wet STEM mode show particularly good resolution and contrast, without adding enhancing contrast objects, and without staining.

Fabricating gold nanoparticle-oxide nanotube composite materials by a self-assembly method.
Xu JZ, Zhao WB, Zhu JJ, Li GX, Chen HY.
J Colloid Interface Sci. 2005 Jun 15; [Epub ahead of print].
[ expand abstract ]

Composition of nanostructured metal particles on oxide tubes (TiO(2) and ZrO(2)) were fabricated and characterized. The composite materials were examined by transmission electron microscopy, scanning electron microscopy, FT-IR absorption, and UV-visible absorption spectra. The results of characterization showed that the composites indeed contained both oxide tubes and gold nanoparticles and that the gold nanoparticles were intimately associated with the nanotubes.

Back to Top

The Binding of Single-Stranded DNA and PNA to Single-Walled Carbon Nanotubes Probed by Flow Linear Dichroism.
Rajendra J, Rodger A.
Chemistry. 2005 Jun 14; [Epub ahead of print].
[ expand abstract ]

The binding of single-stranded DNAs and a neutral DNA analogue (peptide nucleic acid, PNA) to single-walled carbon nanotubes in solution phase has been probed by absorbance spectroscopy and linear dichroism. The nanotubes are solubilised by aqueous sodium dodecyl sulfate, in which the nucleic acids also dissolve. The linear dichroism (LD) of the nanotubes, when subtracted from that due to the nanotubes/nucleic acid samples, gives the LD of the bound nucleic acid. The binding of the single-stranded DNA to the single-walled nanotubes is quite different from that previously observed for double-stranded DNA. It is likely that the nucleic acid bases lie flat on the nanotube surface with the backbone wrapping round the nanotube at an oblique angle in the region of 45 degrees . The net effect is like beads on a string. The base orientation with the single-stranded PNA is inverted with respect to that of the single-stranded DNA, as shown by their oppositely signed LD signals.

Water-Soluble Nanoparticles from Random Copolymer and Oppositely Charged Surfactant, 3.
Kizhakkedathu JN, Nisha CK, Manorama SV, Maiti S.
Macromol Biosci. 2005 Jun 10;5(6):549-558.
[ expand abstract ]

In this report, we investigate the nanoparticle formation between random copolymers (RCPs) of methoxy-poly(ethylene glycol) monomethacrylate (MePEGMA) and (3-(methacryloylamino)propyl)trimethylammonium chloride (MAPTAC) and oppositely charged natural surfactants, sodium oleate and sodium laurate, using turbidimetric titration, steady-state fluorescence, dynamic light scattering, and electron microscopy. Though sodium oleate and sodium laurate are sparingly soluble in water, the nanoparticle complexes formed between the RCPs and these surfactants are soluble in the entire range of compositions studied here, including the stoichiometric electronetural complexes. The spherical nature of these nanoparticle complexes is revealed by electron microscopic (EM) analysis. Dynamic light scattering (DLS) showed that the average diameters of the nanoparticles are in the range 50 to 150 nm, which is supported by EM analysis. Pyrene fluorescence experiments suggested that these soluble nanoparticles have hydrophobic cores, which may solubilize hydrophobic drug molecules. The polarity index (I(1)/I(3)) obtained from the pyrene fluorescence spectra and the conductometric measurements showed that the critical concentration of fatty acid salts needed to obtain nanoparticles are in the order of 10(-4) M. Further, the complexation of such poorly water-soluble amphiphilic surfactants with polymers offers a useful method for the immobilization of hydrophobic compounds towards water-soluble drug carrier formulations.The formation of water-soluble nanoparticles by the self-assembly of fatty acid salts upon interacting with oppositely charged poly(ethylene glycol)-based polyions.

Back to Top

HPLC analysis of PAMAM dendrimer based multifunctional devices.
Islam MT, Majoros IJ, Baker JR Jr.
J Chromatogr B Analyt Technol Biomed Life Sci. 2005 Jun 9; [Epub ahead of print].
[ expand abstract ]

Comprehensive high-performance liquid chromatography (HPLC) analyses were performed on poly(amidoamine) (PAMAM) dendrimer based multifunctional devices. The nanometer-size devices were synthesized by conjugating partially acetylated (Ac) poly(amidoamine) dendrimers of generation 5 (G5) with fluorescein isothiocyanate (FITC), folic acid (FA) and methotrexate (MTX). The devices are intended for targeted intracellular drug delivery to tumor cells through the folate receptor. Methods were developed for detection and separation of various surface functionalized dendrimer conjugates and small molecules (FITC, FA, MTX) using a common gradient. Results indicate that the HPLC technique can be used as a quality control tool for determining purity of the G5 carrier, its acetylated form, and mono-, bi- and tri-functional nanodevices. More importantly, the chromatograms of these novel nanodevices, reported for the first time, provide information on critical properties such as polydispersity, surface heterogeneity and solubility. The benchmark data can be used to optimize the physicochemical properties of the conjugates to improve drug delivery to cancer cells.

Dip-pen patterning and surface assembly of Peptide amphiphiles.
Jiang H, Stupp SI.
Langmuir. 2005 Jun 7;21(12):5242-6.
[ expand abstract ]

This paper presents results on controlling the surface morphology of evaporation-driven self-assembly of peptide amphiphile (PA) nanofibers by dip-pen nanolithography. These PA nanofibers, which measure only a few nanometers in diameter, can be oriented perpendicularly to the receding edge of a solution. Dragging a meniscus of PA ink with an atomic force microscope (AFM) tip creates reproducibly aligned arrays of isolated and close-packed PA nanofiber patterns on silicon substrates, utilizing surface coating of poly(ethylene glycol) to suppress the self-assembly of nanofibers on AFM tips. We also demonstrate the ability to construct double-layer patterns of differing nanofiber orientations at the same position. This result could be important in producing a complex, multilayer pattern of these peptide-based supramolecular nanostructures.

Back to Top

Decoration of Discretely Immobilized Cowpea Mosaic Virus with Luminescent Quantum Dots.
Medintz IL, Sapsford KE, Konnert JH, Chatterji A, Lin T, Johnson JE, Mattoussi H.
Langmuir. 2005 Jun 7;21(12):5501-5510.
[ expand abstract ]

This report describes two related methods for decorating cowpea mosaic virus (CPMV) with luminescent semiconductor nanocrystals (quantum dots, QDs). Variants of CPMV are immobilized on a substrate functionalized with NeutrAvidin using modifications of biotin-avidin binding chemistry in combination with metal affinity coordination. For example, using CPMV mutants expressing available 6-histidine sequences inserted at loops on the viral coat protein, we show that these virus particles can be specifically immobilized on NeutrAvidin functionalized substrates in a controlled fashion via metal-affinity coordination. To accomplish this, a hetero-bifunctional biotin-NTA moiety, activated with nickel, is used as the linker for surface immobilization of CPMV (bridging the CPMVs' histidines to the NeutrAvidin). Two linking chemistries are then employed to achieve CPMV decoration with hydrophilic CdSe-ZnS core-shell QDs; they target the histidine or lysine residues on the exterior virus surface and utilize biotin-avidin interactions. In the first scheme, QDs are immobilized on the surface-tethered CPMV via electrostatic attachment to avidin previously bound to the virus particle. In the second strategy, the lysine residues common to each viral surface asymmetric unit are chemically functionalized with biotin groups and the biotinylated CPMV is discretely immobilized onto the substrate via NeutrAvidin-biotin interactions. The biotin units on the upper exposed surface of the immobilized CPMV then serve as capture sites for QDs conjugated with a mixture of avidin and a second protein, maltose binding protein, which is also used for QD-protein conjugate purification. Characterization of the assembled CPMV and QD structures is presented, and the potential uses for protein-coated QDs functionalized onto this symmetrical virion nanoscaffold are discussed.

Preparation and characterization of intelligent core-shell nanoparticles based on poly(d,l-lactide)-g-poly(N-isopropyl acrylamide-co-methacrylic acid).
Lo CL, Lin KM, Hsiue GH.
J Control Release. 2005 Jun 2;104(3):477-88.
[ expand abstract ]

New thermo-responsive, pH-responsive, and biodegradable nanoparticles comprised of poly(d,l-lactide)-graft-poly(N-isopropyl acrylamide-co-methacrylic acid) (PLA-g-P(NIPAm-co-MAA)) were developed by grafting biodegradable poly(d,l-lactide) onto N-isopropyl acrylamide and methacrylic acid. A core-shell type nano-structure was formed with a hydrophilic outer shell and a hydrophobic inner core, which exhibited a phase transition temperature above 37 degrees C suitable for biomedical application. Upon heating above the phase transition temperature, PLA-g-P(NIPAm-co-MAA) nanoparticle showed a polarity increase of pyrene in either buffer solution or intra-hepato-carcinoma cells as determined by fluorescence measurement, indicating that the structure of nanoparticles caused leakages from outer shell copolymers aggregation and collapsed. The drug loading level of 5-fluorouracil (5-FU) encapsulated in the PLA-g-P(NIPAm-co-MAA) nanoparticles can be as high as 20%. The release of 5-FU from nanoparticles was strongly controlled by the pH in the aqueous solution. Based on these results, PLA-g-P(NIPAm-co-MAA) nanoparticles can be used as a drug carrier for intracellular delivery of anti-cancer drug.

Back to Top

Fiber-optic nanosensors for single-cell monitoring.
Vo-Dinh T, Kasili P.
Anal Bioanal Chem. 2005 Jun 1; [Epub ahead of print].
[ expand abstract ]

This article is an overview of the fabrication, operating principles, and applications of fiber-optic nanobiosensors with the capability of in-vivo analysis at the single-cell level. Recently, the cross-disciplinary integration of nanotechnology, biology, and photonics has been revolutionizing important areas in molecular biology, especially diagnostics and therapy at the molecular and cellular level. Fiber-optic nanobiosensors are a unique class of biosensor that enable analytical measurements in individual living cells and the probing of individual chemical species in specific locations within a cell. This article provides a review of the research performed in our laboratory and discusses the usefulness and potential of this nanotechnology-based biosensor system in biological research and its applications to biomonitoring of individual cells.

Preparation of fullerene-shell dendrimer-core nanoconjugates.
Jensen AW, Maru BS, Zhang X, Mohanty DK, Fahlman BD, Swanson DR, Tomalia DA.
Nano Lett. 2005 Jun;5(6):1171-3.
[ expand abstract ]

Generation 4 amine-terminated polyamidoamine dendrimer (PAMAM G4) was allowed to react with an excess of buckminsterfullerene (C(60)) to form a nanoconjugate containing a PAMAM core and C(60) shell. The PAMAM-C(60) conjugate was characterized by MALDI-TOF, TGA, UV-vis, and IR spectroscopy. Approximately thirty shell fullerenes surround each dendrimer core. The conjugates catalyze photooxidation of thioanisole by generation of singlet oxygen ((1)O(2)). The oxidation reactions occur in both organic and aqueous solvents, but the reactivity is enhanced in aqueous solution, possibly due to a nanoreactor effect resulting from diffusion of hydrophobic reactant molecules into dendrimer cavities.(1).

Back to Top

Quantum dot bioconjugates for imaging, labelling and sensing.
Medintz IL, Uyeda HT, Goldman ER, Mattoussi H.
Nat Mater. 2005 Jun;4(6):435-46.
[ expand abstract ]

One of the fastest moving and most exciting interfaces of nanotechnology is the use of quantum dots (QDs) in biology. The unique optical properties of QDs make them appealing as in vivo and in vitro fluorophores in a variety of biological investigations, in which traditional fluorescent labels based on organic molecules fall short of providing long-term stability and simultaneous detection of multiple signals. The ability to make QDs water soluble and target them to specific biomolecules has led to promising applications in cellular labelling, deep-tissue imaging, assay labelling and as efficient fluorescence resonance energy transfer donors. Despite recent progress, much work still needs to be done to achieve reproducible and robust surface functionalization and develop flexible bioconjugation techniques. In this review, we look at current methods for preparing QD bioconjugates as well as presenting an overview of applications. The potential of QDs in biology has just begun to be realized and new avenues will arise as our ability to manipulate these materials improves.

Nanotechnology and the environment: Risks and rewards.
Owen R, Depledge M.
Mar Pollut Bull. 2005 Jun;50(6):609-12.
[ expand abstract ]

No abstract available.

Back to Top

Metal nanoshell assembly on a virus bioscaffold.
Radloff C, Vaia RA, Brunton J, Bouwer GT, Ward VK.
Nano Lett. 2005 Jun;5(6):1187-91.
[ expand abstract ]

Chilo iridescent virus is demonstrated as a useful core substrate in the fabrication of metallodielectric, plasmonic nanostructures. A gold shell is assembled around the wild-type viral core by attaching small, 2-5-nm gold nanoparticles to the virus surface by means of the chemical functionality found inherently on the surface of the proteinaceous viral capsid. The density of these nucleation sites was maximized by reducing the repulsive forces between the gold particles through electrolyte addition. These gold nanoparticles then act as nucleation sites for the electroless deposition of gold ions from solution around the biotemplate. The optical extinction spectra of the metalloviral complex is in quantitative agreement with Mie scattering theory. Overall, the utilization of a native virus and the inherent chemical functionality of the capsid afford the ability to grow and harvest biotemplates for metallodielectric nanoshells in large quantities, potentially providing cores with a narrower size distribution and smaller diameters (below 80 nm) than for currently used silica.

Overcoming obviousness when patenting nanotechnology inventions.
Stipkala JM.
Nat Biotechnol. 2005 Jun;23(6):677-678.
[ expand abstract ]

No abstract available.

Back to Top

Synthesis and screening of a small library of proline based biodendrimers for use as delivery agents.
Sanclimens G, Shen H, Giralt E, Albericio F, Saltzman MW, Royo M.
Biopolymers. 2005 May 31; [Epub ahead of print].
[ expand abstract ]

A small library of defined peptide dendrimers based on polyproline sequences was designed to demonstrate the feasibility of generating a new type of polymeric agent for therapeutic use. Structural modifications to dendrimer surfaces further enriched the diversity of the library. Data show that the proline-rich dendrimers can be internalized in human epithelial (HeLa) cells, demonstrating the importance of the dendrimeric motif. The promising results described herein suggest that controlled modification of the dendrimer surface should eventually yield proline dendrimers with therapeutic potential. (c) 2005 Wiley Periodicals, Inc. Biopolymers (Peptide Science), 2005.

Construction of a multifunctional envelope-type nano device by a SUV*-fusion method.
Sasaki K, Kogure K, Chaki S, Kihira Y, Ueno M, Harashima H.
Int J Pharm. 2005 May 30;296(1-2):142-50.
[ expand abstract ]

A novel assembly method "SUV*-fusion method" was developed for the construction of a small and homogenous multifunctional envelope-type nano device (MEND) by utilizing a detergent-rich small unilamellar vesicle (SUV*). The method consists of three steps: (1) DNA condensation with a polycation, (2) electrostatic interaction of the SUV* with the DNA/polycation complex (DPC) and (3) lipid coating of DPC by SUV* fusion via removal of the detergent. We confirmed the construction of the MEND by sucrose density gradient centrifugation, and isolated the MEND only from the boundary between 25% and 40% sucrose. The isolated MEND had a small diameter (155 nm), was negatively charged (-24 mV), and encapsulated 30% of the total DNA. The MEND was formed by only SUV*, not by a lipid/detergent micelle. This confirms that a small and homogenous MEND can be constructed by the SUV*-fusion method. Furthermore, we confirmed that a transferrin-modified MEND could deliver a gene into a cell through receptor-mediated endocytosis. Consequently, we report on the successful construction of a small and homogenous MEND by a novel SUV*-fusion method.

Back to Top

Nanotechnology for the biologist.
McNeil SE.
J Leukoc Biol. 2005 May 27; [Epub ahead of print].
[ expand abstract ]

Nanotechnology refers to research and technology development at the atomic, molecular, and macromolecular scale, leading to the controlled manipulation and study of structures and devices with length scales in the 1- to 100-nanometers range. Objects at this scale, such as "nanoparticles," take on novel properties and functions that differ markedly from those seen in the bulk scale. The small size, surface tailorability, improved solubility, and multifunctionality of nanoparticles open many new research avenues for biologists. The novel properties of nanomaterials offer the ability to interact with complex biological functions in new ways--operating at the very scale of biomolecules. This rapidly growing field allows cross-disciplinary researchers the opportunity to design and develop multifunctional nanoparticles that can target, diagnose, and treat diseases such as cancer. This article presents an overview of nanotechnology for the biologist and discusses "nanotech" strategies and constructs that have already demonstrated in vitro and in vivo efficacy.

Magnetic nanotubes for magnetic-field-assisted bioseparation, biointeraction, and drug delivery.
Son SJ, Reichel J, He B, Schuchman M, Lee SB.
J Am Chem Soc. 2005 May 25;127(20):7316-7.
[ expand abstract ]

No abstract available.

Back to Top

Targeting quantum dots to surface proteins in living cells with biotin ligase.
Howarth M, Takao K, Hayashi Y, Ting AY.
Proc Natl Acad Sci U S A. 2005 May 24;102(21):7583-8.
[ expand abstract ]

Escherichia coli biotin ligase site-specifically biotinylates a lysine side chain within a 15-amino acid acceptor peptide (AP) sequence. We show that mammalian cell surface proteins tagged with AP can be biotinylated by biotin ligase added to the medium, while endogenous proteins remain unmodified. The biotin group then serves as a handle for targeting streptavidin-conjugated quantum dots (QDs). This labeling method helps to address the two major deficiencies of antibody-based labeling, which is currently the most common method for targeting QDs to cells: the size of the QD conjugate after antibody attachment and the instability of many antibody-antigen interactions. To demonstrate the versatility of our method, we targeted QDs to cell surface cyan fluorescent protein and epidermal growth factor receptor in HeLa cells and to alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors in neurons. Labeling requires only 2 min, is extremely specific for the AP-tagged protein, and is highly sensitive. We performed time-lapse imaging of single QDs bound to AMPA receptors in neurons, and we compared the trafficking of different AMPA receptor subunits by using two-color pulse-chase labeling.

Hydrophobic dendrimer-derived nanoparticles.
Singh B, Florence AT.
Int J Pharm. 2005 May 21; [Epub ahead of print].
[ expand abstract ]

Lipidic polylysine dendrimers, synthesized using Fmoc solid phase peptide techniques, have been formulated as nanoparticles by precipitation from solution in dichloromethane. The effect of concentration on the diameter and stability of nanoparticles formed from two short homologous series of dendrimers - one fifth generation and one sixth generation series and with surface C(4), C(10) or C(12) groups - was investigated using photon correlation spectroscopy. The increase in generation from fifth to sixth resulted in increased diameter for each chain length. An increase in the surface lipidic chain length from C(4) to C(12) had no effect on the particle diameter of aggregates derived from fifth generation dendrimers, and a small and variable effect on the sixth generation derived nanoparticles. Using pyrene (excitation 340nm) as a hydrophobic fluorescent probe, a decrease in intensity peak I(1) (374nm)/I(3) (385nm) in the emission spectra (340-600nm) was observed in the two dendrimers studied, fifth generation dendrimers with C(10) or C(12) surface lipidic chains, as the dendrimer concentration increased, reaching a plateau at higher concentrations, indicating that a more compact form of the aggregates with a more hydrophobic interior was obtained. Apart from the hydrophobicity of the dendrimers and dendrimer concentration, the flexibility of the dendrimers might have a significant effect in determining nanoparticle size. The aggregates derived from the fifth generation dendrimers with C(10) or C(12) surface lipidic chains are stable in purified intestinal fluid but not in purified stomach fluid, in which further aggregation of the nanoparticulate dendrimer aggregates occurs as an effect of pH, salts, proteins and enzymes in these fluids. This study demonstrates, inter alia, the importance of testing nanoparticulate delivery systems in relevant physiologically based fluids prior to their use in vivo.

Back to Top

Peptide-Polymer Hybrid Nanotubes.
Couet J, Samuel JD, Kopyshev A, Santer S, Biesalski M.
Angew Chem Int Ed Engl. 2005 May 20;44(21):3297-3301.
[ expand abstract ]

No abstract available.

Nanotechnology. Color-changing nanoparticles offer a golden ruler for molecules.
Service RF.
Science 2005 May 20;308(5725):1099.
[ expand abstract ]

At a meeting here last week, a chemist reported a way to use pairs of gold nanoparticles to track the binding and unbinding of DNA.

Back to Top

Amperometric biosensors based on redox polymer-carbon nanotube-enzyme composites.
Joshi PP, Merchant SA, Wang Y, Schmidtke DW.
Anal Chem. 2005 May 15;77(10):3183-8.
[ expand abstract ]

Based on their size and unique electrical properties, carbon nanotubes offer the exciting possibility of developing ultrasensitive, electrochemical biosensors. In this study, we describe the construction of amperometric biosensors based on the incorporation of single-walled carbon nanotubes modified with enzyme into redox polymer hydrogels. The composite films were constructed by first incubating an enzyme in a single-walled carbon nanotube (SWNTs) solution and then cross-linking within a poly[(vinylpyridine)Os(bipyridyl)(2)Cl(2+/3+)] polymer film. Incorporation of SWNTs, modified with glucose oxidase, into the redox polymer films resulted in a 2-10-fold increase in the oxidation and reduction peak currents during cyclic voltammetry, while the glucose electrooxidation current was increased 3-fold to approximately 1 mA/cm(2) for glucose sensors. Similar effects were also observed when SWNTs were modified with horseradish peroxidase prior to incorporation into redox hydrogels.

Electrochemically deposited nanocomposite of chitosan and carbon nanotubes for biosensor application.
Luo XL, Xu JJ, Wang JL, Chen HY.
Chem Commun (Camb). 2005 May 14;(16):2169-71.
[ expand abstract ]

A simple and controllable electrodeposition method for the formation of a chitosan-carbon nanotube nanocomposite film on an electrode surface was proposed and further used for the construction of an electrochemical biosensor.

Back to Top

Carbon Nanotubes Loaded with Magnetic Particles.
Korneva G, Ye H, Gogotsi Y, Halverson D, Friedman G, Bradley JC, Kornev KG.
Nano Lett. 2005 May 11;5(5):879-884.
[ expand abstract ]

We describe a simple and versatile technique to produce magnetic tubes by filling carbon nanotubes (CNTs) with paramagnetic iron oxide particles ( approximately 10 nm diameter). Commercial ferrofluids were used to fill CNTs with an average outer diameter of 300 nm made via chemical vapor deposition into alumina membranes. Transmission electron microscopy study shows a high density of particles inside the CNT. Experiments using external magnetic fields demonstrate that almost 100% of the nanotubes become magnetic and can be easily manipulated in magnetic field. These one-dimensional magnetic nanostructures can find numerous applications in nanotechnology, memory devices, optical transducers for wearable electronics, and in medicine.

Controlled fabrication of hierarchically branched nanopores, nanotubes, and nanowires.
Meng G, Jung YJ, Cao A, Vajtai R, Ajayan PM.
Proc Natl Acad Sci U S A. 2005 May 3; [Epub ahead of print].
[ expand abstract ]

Here, we report a generic synthetic approach to rationally design multiply connected and hierarchically branched nanopores inside anodic aluminum oxide templates. By using these nanochannels, we controllably fabricate a large variety of branched nanostructures, far more complex than what exists today. These nanostructures include carbon nanotubes and metallic nanowires having several hierarchical levels of multiple branching. The number and frequency of branching, dimensions, and the overall architecture are controlled precisely through pore design and templated assembly. The technique provides a powerful approach to produce nanostructures of greater morphological complexity, which could have far-reaching implications in the design of future nanoscale systems.

Back to Top

Integration of cell membranes and nanotube transistors.
Bradley K, Davis A, Gabriel JC, Gruner G.
Nano Lett. 2005 May;5(5):841-5.
[ expand abstract ]

We report the integration of a complex biological system and a nanoelectronic device, demonstrating that both components retain their functionality while interacting with each other. As the biological system, we use the cell membrane of Halobacterium salinarum. As the nanoelectronic device, we use a nanotube network transistor, which incorporates many individual nanotubes in such a way that entire patches of cell membrane are contacted by nanotubes. We demonstrate that the biophysical properties of the membrane are preserved, that the nanoelectronic devices still function as transistors, and that the two systems interact. Further, we use the interaction to study the charge distribution in the biological system, finding that the electric dipole of the membrane protein bacteriorhodopsin is located 2/3 of the way from the extracellular to the cytoplasmic side.

Dip Pen Nanolithography (DPN): process and instrument performance with NanoInk's NSCRIPTOR system.
Haaheim J, Eby R, Nelson M, Fragala J, Rosner B, Zhang H, Athas G.
Ultramicroscopy. 2005 May;103(2):117-32.
[ expand abstract ]

Precision nanoscale deposition is a fundamental requirement for much of current nanoscience research and promises to facilitate exciting industrial applications. Tailoring chemical composition and surface structure on the sub-100 nm scale benefits researchers in topics ranging from catalysis, to biological recognition in nanoscale systems, to electronic connectivity on the nanoscale. Precision nanoscale deposition engenders applications such as additive photomask repair and nanodevice fabrication. Dip Pen Nanolithography (DPN) is a scanning-probe-based direct-write technique for generating surface-patterned chemical functionality and discrete structures on the sub-100 nm scale. In this publication we explore the effects of changing tip radius and surface roughness. We find that blunter tips lead to higher minimum line widths and that higher rms surface roughness leads to higher minimum line widths; line edge roughness also increases with substrate roughness and surface feature size. Also, we characterize the performance of the Nscriptor DPN instrument and demonstrate the placement of pattern features with precision better than 10 nm, and size control better than 15% for sub-100 nm features.

Back to Top

Manufacturing of nanochannels with controlled dimensions using protease nanolithography.
Ionescu RE, Marks RS, Gheber LA.
Nano Lett. 2005 May;5(5):821-7.
[ expand abstract ]

The feasibility of creating nanometer scale depressions in biological substrates using active enzymes delivered with scanning probe microscopes has been previously demonstrated by us and other groups. Here we present a comprehensive study revealing the dependence of channels dimensions on the parameters of the "writing" process and provide a simple way to precisely control their dimensions. Such nanochannels may be used in nanofluidic biochip applications.

The enhancement of recombinant protein production by polymer nanospheres in cell suspension culture.
Ryu JH, Kim MS, Lee GM, Choi CY, Kim BS.
Biomaterials. 2005 May;26(14):2173-81.
[ expand abstract ]

Recombinant Chinese hamster ovary (rCHO) cells are being increasingly used in industry for the production of recombinant therapeutic proteins. Three-dimensional suspension culture is preferred to two-dimensional monolayer culture for the efficient large-scale culture of rCHO cells and subsequent mass production of recombinant proteins. Previously, we have demonstrated that the use of plain polymer nanospheres enhances the growth of anchorage-dependent animal cells (human embryonic kidney 293 cells) in suspension culture in serum-containing medium. Vitronectin and fibronectin were adsorbed onto poly(lactic-co-glycolic acid) (PLGA) nanospheres (696 nm in average diameter) by immersing the nanospheres in fetal bovine serum. In this study, we investigated if the use of vitronectin/fibronectin-adsorbed polymer nanospheres enhances recombinant protein production in rCHO cell suspension culture in serum-free medium. Cell aggregate formation may be critical for the survival and growth of anchorage-dependent animal cells in suspension culture, and cells in single cell suspension may result in cell death. The addition of vitronectin/fibronectin-adsorbed nanospheres to rCHO cell suspension culture promoted the rate and efficiency of cell aggregate formation. The nanospheres enhanced cell growth (2.9 folds on day 10) and, importantly, recombinant antibody production (1.8 folds on day 14), compared to suspension culture without nanospheres. The viability of cells in the aggregates in the nanosphere-added culture was high for the entire culture period of 14 days. Apoptotic activity of cells was much lower in the nanosphere-added culture than in the culture without nanospheres on day 5. The nanosphere suspension culture method developed in this study may be useful for the mass production of recombinant proteins through large-scale suspension culture of anchorage-dependent animal cells.

Back to Top

Encapsulation of magnetic and fluorescent nanoparticles in emulsion droplets.
Mandal SK, Lequeux N, Rotenberg B, Tramier M, Fattaccioli J, Bibette J, Dubertret B.
Langmuir. 2005 Apr 26;21(9):4175-9.
[ expand abstract ]

Oils containing both fluorescent semiconductor and magnetic oxide nanoparticles are used to produce oil in water emulsions. This technique produces oil droplets with homogeneous fluorescence and high magnetic nanoparticle concentrations. The optical properties of the oil droplets are studied as a function of the droplet sizes for various concentrations of fluorescent and magnetic nanoparticles. For all concentrations tested, we find a linear variation of the droplet fluorescent intensity as a function of the droplet volume. For a given size and a given quantum dot (QD) concentration, the droplet fluorescence intensity drops sharply as a function of the magnetic nanoparticle concentration. We show that this decrease is due mainly to the strong absorption cross section of the magnetic nanoparticles and to a lesser extent to the dynamic and static quenching of the QD fluorescence. The role of the iron oxide nanoparticle localization in the droplet (surface versus volume) is also discussed.

Synthesis of gold nanoparticles within a supramolecular gel-phase network.
Love CS, Chechik V, Smith DK, Wilson K, Ashworth I, Brennan C.
Chem Commun (Camb). 2005 Apr 21;(15):1971-3.
[ expand abstract ]

Gold nanoparticles with diameters of ca. 13 nm were synthesised by UV irradiation of a supramolecular organogel into which HAuCl(4) and tetraoctylammonium bromide had been diffused-the gel network plays an essential role in nanoparticle stabilisation.

Back to Top

Silica-Coated Nanocomposites of Magnetic Nanoparticles and Quantum Dots.
Yi DK, Selvan ST, Lee SS, Papaefthymiou GC, Kundaliya D, Ying JY.
J Am Chem Soc. 2005 Apr13;127(14):4990-4991.
[ expand abstract ]

Quantum dots (QDs) and magnetic nanoparticles (MPs) are of interest for biological imaging, drug targeting, and bioconjugation because of their unique optoelectronic and magnetic properties, respectively. To provide for water solubility and biocompatibility, QDs and MPs were encapsulated within a silica shell using a reverse microemulsion synthesis. The resulting SiO(2)/MP-QD nanocomposite particles present a unique combination of magnetic and optical properties. Their nonporous silica shell allows them to be surface modified for bioconjugation in various biomedical applications.

Cast thin film biosensor design based on a nafion backbone, a multiwalled carbon nanotube conduit, and a glucose oxidase function.
Tsai YC, Li SC, Chen JM.
Langmuir. 2005 Apr12;21(8):3653-8.
[ expand abstract ]

Novel electroanalytical sensing nanobiocomposite materials are reported. These materials are prepared by mixing multiwalled carbon nanotubes (MWNTs), a Nafion cation exchanger, and glucose oxidase (GOD) in appropriate amounts. The MWNTs are cylindrical with a diameter in the range 40-60 nm and with a length of up to several micrometers, and they provide electrical conductivity. Nafion acts as a polymer backbone to give stable and homogeneous cast thin films. Both MWNTs and Nafion provide negative functionalities to bind to positively charged redox enzymes such as glucose oxidase. The resulting biosensing composite material is inexpensive, reliable, and easy to use. The homogeneity of the MWNT-Nafion-GOD nanobiocomposite films was characterized by atomic force microscopy (AFM). Amperometric transducers fabricated with these materials were characterized electrochemically using cyclic voltammetry and amperometry in the presence of hydrogen peroxide and in the presence of glucose. Their linear response to hydrogen peroxide was demonstrated. The glucose biosensor sensitivity was strongly influenced by the glucose oxidase concentration within the nanobiocomposite film. The optimized glucose biosensor (2.5 mg/mL GOD) displayed a sensitivity of 330 nA/mM, a linear range of up to 2 mM, a detection limit of 4 muM, and a response time of <3 s.

Back to Top

Tethered or adsorbed supported lipid bilayers in nanotubes characterized by deuterium magic angle spinning NMR spectroscopy.
Wattraint O, Warschawski DE, Sarazin C.
Langmuir. 2005 Apr12;21(8):3226-8.
[ expand abstract ]

(2)H solid-state NMR experiments were performed under magic angle spinning on lipid bilayers oriented into nanotubes arrays, as a new method to assess the geometrical arrangement of the lipids. Orientational information is obtained from the intensities of the spinning sidebands. The lipid bilayers are formed by fusion of small unilamellar vesicles of DMPC-d(54) inside a nanoporous anodic aluminum oxide, either by direct adsorption on the support or by tethering through a streptavidin/biotin linker. The results support that the quality of the lipid bilayers alignment is clearly in favor of the tethering rather than an adsorbed strategy.

Engineering of vault nanocapsules with enzymatic and fluorescent properties.
Kickhoefer VA, Garcia Y, Mikyas Y, Johansson E, Zhou JC, Raval-Fernandes S, Minoofar P, Zink JI, Dunn B, Stewart PL, Rome LH.
Proc Natl Acad Sci U S A. 2005 Mar22;102(12):4348-52.
[ expand abstract ]

One of the central issues facing the emerging field of nanotechnology is cellular compatibility. Nanoparticles have been proposed for diagnostic and therapeutic applications, including drug delivery, gene therapy, biological sensors, and controlled catalysis. Viruses, liposomes, peptides, and synthetic and natural polymers have been engineered for these applications, yet significant limitations continue to prevent their use. Avoidance of the body's natural immune system, lack of targeting specificity, and the inability to control packaging and release are remaining obstacles. We have explored the use of a naturally occurring cellular nanoparticle known as the vault, which is named for its morphology with multiple arches reminiscent of cathedral ceilings. Vaults are 13-MDa ribonucleoprotein particles with an internal cavity large enough to sequester hundreds of proteins. Here, we report a strategy to target and sequester biologically active materials within the vault cavity. Attachment of a vault-targeting peptide to two proteins, luciferase and a variant of GFP, resulted in their sequestration within the vault cavity. The targeted proteins confer enzymatic and fluorescent properties on the recombinant vaults, both of which can be detected by their emission of light. The modified vaults are compatible with living cells. The ability to engineer vault particles with designed properties and functionalities represents an important step toward development of a biocompatible nanocapsule.

Back to Top

A simple and convenient route to prepare poly(vinylidene fluoride trifluoroethylene) copolymer nanowires and nanotubes.
Zheng RK, Yang Y, Wang Y, Wang J, Chan HL, Choy CL, Jin CG, Li XG.
Chem Commun (Camb). 2005 Mar21;(11):1447-9.
[ expand abstract ]

Poly(vinylidene fluoride trifluoroethylene) copolymer nanowires and nanotubes have been prepared for the first time via a high temperature (</=260 degrees C) vacuum infiltration method, which is a simple and convenient route for fabricating polymer nanowires and nanotubes when polymers, instead of monomers, are used as the starting materials.

Solidification of gold nanoparticles in carbon nanotubes.
Arcidiacono S, Walther JH, Poulikakos D, Passerone D, Koumoutsakos P.
Phys Rev Lett. 2005 Mar18;94(10):105502.
[ expand abstract ]

The structure and the solidification of gold nanoparticles in a carbon nanotube are investigated using molecular dynamics simulations. The simulations indicate that the predicted solidification temperature of the enclosed particle is lower than its bulk counterpart, but higher than that observed for clusters placed in vacuum. A comparison with a phenomenological model indicates that, in the considered range of tube radii (R(CNT)) of 0.5<R(CNT)<1.6 nm, the solidification temperature depends mainly on the length of the particle with a minor dependence on R(CNT).

Back to Top

Comparison of analytical techniques for purity evaluation of single-walled carbon nanotubes.
Itkis ME, Perea DE, Jung R, Niyogi S, Haddon RC.
J Am Chem Soc. 2005 Mar16;127(10):3439-48.
[ expand abstract ]

We compare popular analytical techniques, including scanning and transmission electron microscopy (SEM and TEM), thermogravimetric analysis (TGA), and Raman and near-infrared (NIR) spectroscopy, for the evaluation of the purity of bulk quantities of single-walled carbon nanotubes (SWNTs). Despite their importance as imaging techniques, SEM and TEM are not capable of quantitatively evaluating the purity of typical inhomogeneous bulk SWNT samples because the image frame visualizes less than 1 pg of SWNT material; furthermore, there is no published algorithm to convert such images into numerical data. The TGA technique is capable of measuring the amount of metal catalyst in an SWNT sample, but does not provide an unambiguous separation between the content of SWNTs and carbonaceous impurities. We discuss the utilization of solution-phase near-infrared spectroscopy and solution-phase Raman spectroscopy to quantitatively compare arbitrary samples of bulk SWNT materials of different purities. The primary goal of this paper is to provide the chemical community with a realistic evaluation of current analytical tools for the purity evaluation of a bulk sample of SWNTs. The secondary goal is to draw attention to the growing crisis in the SWNT industry as a result of the lack of quality control and the misleading advertising by suppliers of this material.

Oligo(ethylene glycol) containing polymer brushes as bioselective surfaces.
Andruzzi L, Senaratne W, Hexemer A, Sheets ED, Ilic B, Kramer EJ, Baird B, Ober CK.
Langmuir. 2005 Mar15;21(6):2495-504.
[ expand abstract ]

The nitroxide-mediated polymerization of styrenic monomers containing oligo(ethylene glycol) (OEGn) moieties was chosen for the preparation of biocompatible polymer brushes tethered to silicon oxide surfaces due to the broad range of monomer structures available and the use of a nonmetallic initiator. These surfaces were characterized by near-edge X-ray absorption fine structure and water contact angle measurements. The biocompatibility of these grown polymer brushes was studied and compared with deposited assemblies of surface-bound OEGn-terminated silanes with selected chain lengths. Grown polymer brushes with short OEGn side chains suppressed protein adsorption significantly more than the deposited assemblies of short OEGn chains, and this was attributed to higher surface coverage by the brushes. Cell adhesion studies confirmed that OEGn-containing polymer brushes are particularly effective in preventing nonspecific adhesion. Studies of protein adsorption and cell localization carried out with specific ligands on surfaces patterned demonstrated the potential of these surface-tethered polymer brushes for the formation of micro- and nanoscale devices.

Back to Top

Controlled synthesis of nonspherical microparticles using microfluidics.
Dendukuri D, Tsoi K, Hatton TA, Doyle PS.
Langmuir. 2005 Mar15;21(6):2113-6.
[ expand abstract ]

The controlled synthesis of nonspherical microparticles using microfluidics processing is described. Polymer droplets, formed by shearing a photopolymer using a continuous water phase at a T-junction, were constrained to adopt nonspherical shapes by confining them using appropriate microchannel geometries. Plugs were obtained by shearing the polymer phase at low shear rates, while disks were obtained by flattening droplets using a channel of low height. The nonspherical shapes formed were permanently preserved by photopolymerizing the constrained droplets in situ using ultraviolet light. Monodisperse plugs and disks of different lengths and diameters were obtained by varying the flow rates of the two phases.

Organic and inorganic nanoparticle hybrids.
Portney NG, Singh K, Chaudhary S, Destito G, Schneemann A, Manchester M, Ozkan M.
Langmuir. 2005 Mar15;21(6):2098-103.
[ expand abstract ]

Viruses are exemplary models in nanoassembly for their regular geometries, well characterized surface properties, and nanoscale dimensions. Armed with versatile tools aimed at site-directed mutagenesis to modify the virion's surface, conjugation chemistry for capsid coupling, and manipulation of nanoparticles, we have demonstrated nanoscale assembly of inorganic carbon nanotubes and quantum dots with engineered viruses to produce an intimate array of hybrid structures.

Back to Top

Electrically Assisted Sampling across Membranes with Electrophoresis in Nanometer Inner Diameter Capillaries.
Woods LA, Gandhi PU, Ewing AG.
Anal Chem. 2005 Mar 15;77(6):1819-23.
[ expand abstract ]

A nondestructive method for sampling from ultrasmall environments has been developed utilizing electrophoresis in nanometer inner diameter capillaries and etched electrochemical detection. The desire to study increasingly smaller biological environments such as mammalian cells has led to the need for capillary electrophoresis techniques with subpicoliter volume sampling capabilities. This sampling technique involves the fabrication of a microinjector at the tip of a 770-nm-inner diameter capillary and the use of electroporation for insertion through the membrane. Separations of catecholamines sampled from the interior of intact liposomes have been achieved. A separation of a cytoplasmic sample taken from an intact mammalian cell has also been obtained.

Gold nanoparticle-modified etched capillaries for open-tubular capillary electrochromatography.
Yang L, Guihen E, Holmes JD, Loughran M, O'sullivan GP, Glennon JD.
Anal Chem. 2005 Mar 15;77(6):1840-6.
[ expand abstract ]

The use of gold nanoparticles in conjunction with etched capillary-based open-tubular capillary electrochromatography (OTCEC) to improve the efficiency of separation and the selectivity between selected solutes is described. The fused-silica capillaries (50-mum i.d.) were etched with ammonium hydrogen difluoride, followed by prederivatization of the new surface with (3-mercaptopropyl)trimethoxysilane (MPTMS) for the immobilization of dodecanethiol gold nanoparticles, for OTCEC. The electrochromatography of a "reversed-phase" test mixture and of selected polycylic aromatic hydrocarbons was investigated, and efficient separations and high theoretical plate numbers per meter were obtained. The electroosmotic flow characteristics of the etched gold nanoparticle capillary, unetched gold nanoparticle capillary, bare capillary, and etched bare capillary were studied by varying the percentage of organic modifier in buffer, buffer pH, and separation voltage. Optical microscopy and scanning electron microscopy were used to examine the process of etching and modification and the surface features of the etched gold nanoparticle capillary. The results confirm that dodecanethiol gold nanoparticles bonded on the etched inner wall of the fused-silica capillary can provide sufficient solute-bonded phase interactions to obtain OTCEC separations with reproducible retention, as well as characteristic reversed-phase behavior, even with the inner diameter of the capillary of 50 mum.

Back to Top

Ligand Density Effect on Biorecognition by PEGylated Gold Nanoparticles: Regulated Interaction of RCA(120) Lectin with Lactose Installed to the Distal End of Tethered PEG Strands on Gold Surface.
Takae S, Akiyama Y, Otsuka H, Nakamura T, Nagasaki Y, Kataoka K.
Biomacromolecules. 2005 Mar 14;6(2):818-824.
[ expand abstract ]

PEGylated gold nanoparticles (diameter: 20 nm) possessing various functionalities of lactose ligand on the distal end of tethered PEG ranging from 0 to 65% were prepared to explore the effect of ligand density of the nanoparticles on their lectin binding property. UV-visible spectra of the aqueous solution of the nanoparticles revealed that the strong steric stabilization property of the PEG layer lends the nanoparticles high dispersion stability even under the physiological salt concentration (ionic strength, I = 0.15 M). The number of PEG strands on a single particle was determined to be 520 from thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) observation under controlled acceleration voltage revealed the thickness of the PEG layer on the nanoparticle to be approximately 7 nm. The area occupied by a single lactose molecule on the surface of PEGylated gold nanoparticles was then calculated based on TGA and SEM results and was varied in the range of 10-34 nm(2) depending on the lactose functionality (65 approximately 20%). PEGylated gold nanoparticles with 40% and 65% lactose functionality showed a selective and time-dependent aggregation in phosphate buffer with the addition of Ricinus communis agglutinin (RCA(120)) lectin, a bivalent galactose-specific protein. The aggregates can be completely redispersed by adding an excess amount of galactose. Time-lapse monitoring of UV-visible spectra at 600-750 nm revealed that the aggregation of PEGylated gold nanoparticles was accelerated with an increase in both RCA(120) concentration in the solution and the lactose density of the nanoparticles. Furthermore, the sensitivity of lectin detection could be controlled by the regulation of lactose density on the particle surface. Interestingly, there was a critical lactose density (>20%) observed to induce detectable particle aggregation, indicating that the interaction between the particles is triggered by the multimolecular bridging via lectin molecules.

Genetically engineered protein in hydrogels tailors stimuli-responsive characteristics.
Ehrick JD, Deo SK, Browning TW, Bachas LG, Madou MJ, Daunert S.
Nat Mater. 2005 Mar 13; [Epub ahead of print].
[ expand abstract ]

Certain proteins undergo a substantial conformational change in response to a given stimulus. This conformational change can manifest in different manners and result in an actuation, that is, catalytic or signalling event, movement, interaction with other proteins, and so on. In all cases, the sensing-actuation process of proteins is initiated by a recognition event that translates into a mechanical action. Thus, proteins are ideal components for designing new nanomaterials that are intelligent and can perform desired mechanical actions in response to target stimuli. A number of approaches have been undertaken to mimic nature's sensing-actuating process. We now report a new hybrid material that integrates genetically engineered proteins within hydrogels capable of producing a stimulus-responsive action mechanism. The mechanical effect is a result of an induced conformational change and binding affinities of the protein in response to a stimulus. The stimuli-responsive hydrogel exhibits three specific swelling stages in response to various ligands offering additional fine-tuned control over a conventional two-stage swelling hydrogel. The newly prepared material was used in the sensing, and subsequent gating and transport of biomolecules across a polymer network, demonstrating its potential application in microfluidics and miniaturized drug-delivery systems.

Back to Top

A novel microfluidic mixer utilizing electrokinetic driving forces under low switching frequency.
Fu LM, Yang RJ, Lin CH, Chien YS.
Electrophoresis. 2005 Mar 7; [Epub ahead of print].
[ expand abstract ]

This paper presents a novel technique in which low-frequency periodic electrokinetic driving forces are utilized to mix electrolytic fluid samples rapidly and efficiently in a double-T-form microfluidic mixer. Without using any additional equipment to induce flow perturbations, only a single high-voltage power source is required for simultaneously driving and mixing the sample fluids which results in a simple and low-cost system for the mixing purpose. The effectiveness of the mixer as a function of the applied electric field and the periodic switching frequency is characterized by the intensity distribution calculated downstream from the mixing zone. The present numerical and experimental results confirm that the proposed double-T-form micromixer has excellent mixing capabilities. The mixing efficiency can be as high as 95% within a mixing length of 1000 mum downstream from the secondary T-junction when a 100 V/cm driving electric field strength and a 2 Hz periodic switching frequency are applied. The results reveal that the optimal switching frequency depends upon the magnitude of the main applied electrical field. The rapid double-T-form microfluidic mixer using the periodic driving voltage switching model proposed in this study has considerable potential for use in lab-on-a-chip systems.

Engineering of vault nanocapsules with enzymatic and fluorescent properties.
Kickhoefer VA, Garcia Y, Mikyas Y, Johansson E, Zhou JC, Raval-Fernandes S, Minoofar P, Zink JI, Dunn B, Stewart PL, Rome LH.
Proc Natl Acad Sci U S A. 2005 Mar 7; [Epub ahead of print].
[ expand abstract ]

One of the central issues facing the emerging field of nanotechnology is cellular compatibility. Nanoparticles have been proposed for diagnostic and therapeutic applications, including drug delivery, gene therapy, biological sensors, and controlled catalysis. Viruses, liposomes, peptides, and synthetic and natural polymers have been engineered for these applications, yet significant limitations continue to prevent their use. Avoidance of the body's natural immune system, lack of targeting specificity, and the inability to control packaging and release are remaining obstacles. We have explored the use of a naturally occurring cellular nanoparticle known as the vault, which is named for its morphology with multiple arches reminiscent of cathedral ceilings. Vaults are 13-MDa ribonucleoprotein particles with an internal cavity large enough to sequester hundreds of proteins. Here, we report a strategy to target and sequester biologically active materials within the vault cavity. Attachment of a vault-targeting peptide to two proteins, luciferase and a variant of GFP, resulted in their sequestration within the vault cavity. The targeted proteins confer enzymatic and fluorescent properties on the recombinant vaults, both of which can be detected by their emission of light. The modified vaults are compatible with living cells. The ability to engineer vault particles with designed properties and functionalities represents an important step toward development of a biocompatible nanocapsule.

Back to Top

Incorporation of single-wall carbon nanotubes into an organic polymer monolithic stationary phase for mu-hplc and capillary electrochromatography.
Li Y, Chen Y, Xiang R, Ciuparu D, Pfefferle LD, Horvath C, Wilkins JA.
Anal Chem. 2005 Mar 1;77(5):1398-406.
[ expand abstract ]

Single-wall carbon nanotubes (SWNT) were incorporated into an organic polymer monolith containing vinylbenzyl chloride (VBC) and ethylene dimethacrylate (EDMA) to form a novel monolithic stationary phase for high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC). The retention behavior of neutral compounds on this poly(VBC-EDMA-SWNT) monolith was examined by separating a mixture of small organic molecules using micro-HPLC. The result indicated that incorporation of SWNT enhanced chromatographic retention of small neutral molecules in reversed-phase HPLC presumably because of their strongly hydrophobic characteristics. The stationary phase was formed inside a fused-silica capillary whose lumen was coated with covalently bound polyethyleneimine (PEI). The annular electroosmotic flow (EOF) generated by the PEI coating allowed peptide separation by CEC in the counterdirectional mode. Comparison of peptide separations on poly(VBC-EDMA-SWNT) and on poly(VBC-EDMA) with annular EOF generation revealed that the incorporation of SWNT into the monolithic stationary phase improved peak efficiency and influenced chromatographic retention. The structures of pretreated SWNT and poly(VBC-EDMA-SWNT) monolith were examined by high-resolution transmission electron microscopy, Raman spectroscopy, scanning electron microscopy, and multipoint BET nitrogen adsorption/desorption.

Layer-by-layer assembly of human serum albumin and phospholipid nanotubes based on a template.
Lu G, Ai S, Li J.
Langmuir. 2005 Mar 1;21(5):1679-82.
[ expand abstract ]

The preparation of nanotubes from human serum albumin (HSA) and mixtures of L-alpha-dimyristoylphosphatidic acid (DMPA)/HSA is described. The nanotubes were prepared via alternate adsorption of HSA of different/opposite charges (by variation of the pH) or by sequential adsorption of DMPA and HSA, respectively, onto the inner surfaces of porous anodic alumina templates. This simple layer-by-layer assembly results in a monodisperse size distribution and a uniform orientation. The nanotubes allow the specific incorporation of lipophilic components such as channels or receptors and may thus serve as probes or sensors for biological systems.

Back to Top

Direct conjugation of semiconductor nanoparticles with proteins.
Meziani MJ, Pathak P, Harruff BA, Hurezeanu R, Sun YP.
Langmuir. 2005 Mar 1;21(5):2008-11.
[ expand abstract ]

Nanocrystalline CdS particles directly conjugated with bovine serum albumin (BSA) protein were prepared by applying the supercritical fluid processing technique, rapid expansion of a supercritical solution into a liquid solvent. The direct conjugation takes advantage of the unique features of the process for nanoparticle formation. The BSA-conjugated CdS nanoparticles in stable aqueous suspension or in the solid state were characterized by using microscopy, X-ray diffraction, and optical spectroscopy methods. The results show that well-dispersed CdS nanoparticles are coated with BSA in a core-shell-like arrangement and that the protein species associated with the nanoparticles remain functional according to the modified Lowry assay. These BSA-conjugated CdS nanoparticles are also strongly luminescent, with the luminescence spectrum contributed to primarily by the exciton emission.

Bioreactive surfaces prepared via the self-assembly of dendron thiols and subsequent dendrimer bridging reactions.
Yang M, Tsang EM, Wang YA, Peng X, Yu HZ.
Langmuir. 2005 Mar 1;21(5):1858-65.
[ expand abstract ]

Here, we report a novel route to prepare bioreactive surfaces on gold by the self-assembly of generation-three hydroxyl-terminated dendron thiols (G3-OH) and subsequent bridging reactions using generation-two amine-terminated dendrimers (G2-NH(2)). It has been shown that G3-OH dendron thiols form a stable and uniform self-assembled monolayer on gold, which can be activated by the homobifunctional cross-linker N,N-disuccinimidyl carbonate (DSC). Subsequent derivatization of the activated monolayer via dendrimer bridging reactions with G2-NH(2) enhances the stability, reactivity, and versatility of the prepared surface. Each step of the surface formation reaction has been monitored, and the resulting surface has been characterized by wetting, electrochemistry, scanning tunneling microscopy (STM), and infrared (IR) spectroscopy measurements. The reactivity of this surface was demonstrated by a Schiff base coupling reaction with 4-cyanobenzaldehyde, by immobilizing biotin molecules onto the peripheral amine groups using one of the conjugation methods, and by further binding avidin onto the biotinylated surface. We believe that the prepared bioreactive surface with a high density of amine groups will be useful for the immobilization of biological macromolecules for various biosensor applications, such as the fabrication of DNA microarrays and protein chips.

Back to Top

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for quantitation and molecular stability assessment of insulin entrapped within PLGA nanoparticles.
Bilati U, Pasquarello C, Corthals GL, Hochstrasser DF, Allemann E, Doelker E.
J Pharm Sci. 2005 Mar;94(3):688-94.
[ expand abstract ]

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was evaluated for both qualitative and quantitative analysis of insulin entrapped within poly(D,L-lactic-co-glycolic acid) nanoparticles. Quantitation was performed by adding an internal standard (arg-insulin) to defined and unknown sample solutions, in order to reduce point-to-point and sample-to-sample variability. The ratio of the peak height of insulin to the peak height of arg-insulin was plotted against the insulin concentration. In this way, an excellent linear relationship was found (R(2) > 0.99). This method of quantitation was compared with classical UV spectroscopy and reverse-phase high-performance liquid chromatography measurements. All methods provided close final drug loading values for the insulin-loaded nanoparticle batches tested. Additionally, with respect to molecular stability, covalent insulin dimers were found only at trace levels in those nanoparticles. Compared with other methods, MALDI-TOF MS is a valuable tool for the characterization of proteins from nanoparticles, because no extensive extraction and complex sampling procedures are required. (c) 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:688-694, 2005.

Characterization of aqueous dispersions of Fe(3)O(4) nanoparticles and their biomedical applications.
Cheng FY, Su CH, Yang YS, Yeh CS, Tsai CY, Wu CL, Wu MT, Shieh DB.
Biomaterials. 2005 Mar;26(7):729-38.
[ expand abstract ]

A newly developed non-polymer coated Fe(3)O(4) nanoparticles showing well-dispersion were synthesized using Fe(II) and Fe(III) salt chemical coprecipitation with tetramethylammonium hydroxide (N(CH(3))(4)OH) in an aqueous solution. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), X-ray photoelectron spectrometer (XPS) and superconducting quantum interference measurement device (SQUID) measurements were employed to investigate the iron oxide properties. The resulting iron oxide particles were manipulated to be as small as 9 nm diameter in size. Based on FT-IR and X-ray photoelectron spectrometer results, it is suggested that the surfaces of the magnetite (Fe(3)O(4)) particles are covered with hydroxide (-OH) groups incorporated with (CH(3))(4)N(+) through electrostatic interaction. The in vitro cytotoxicity test revealed that the magnetite particles exhibited excellent biocompatibility, suggesting that they may be further explored for biomedical applications. NMR measurements revealed significantly reduced water proton relaxation times T1 and T2. The MR images of the nanoparticles in water, serum, and whole blood were investigated using a 1.5 T clinical MR imager. Significant reduction of the background medium signal was achieved in the T2-weighted and the T2*-weighted sequence especially in the serum and whole blood. Combining the advantage of MRI signal contrast, the non-polymer-coated surface chemistry for distinct bioconjugation and the homogenous nanometer size for better controlled biodistribution, these preliminary experiments demonstrated the potential of the as-synthesized magnetite material in functional molecular imaging for biomedical research and clinical diagnosis.

Back to Top

Gold nanoshells on polystyrene cores for control of surface plasmon resonance.
Shi W, Sahoo Y, Swihart MT, Prasad PN.
Langmuir. 2005 Feb 15;21(4):1610-7.
[ expand abstract ]

A method is presented for synthesizing core-shell structures consisting of monodisperse polystyrene latex nanospheres as cores and gold nanoparticles as shells. Use of polystyrene spheres as the core in these structures is advantageous because they are readily available commercially in a wide range of sizes, and with dyes or other molecules doped into them. Gold nanoparticles, ranging in size from 1 to 20 nm, are prepared by reduction of a gold precursor with sodium citrate or tetrakis(hydroxymethyl)phosphonium chloride (THPC). Carboxylate-terminated polystyrene spheres are functionalized with 2-aminoethanethiol hydrochloride (AET), which forms a peptide bond with carboxylic acid groups on their surface, resulting in a thiol-terminated surface. Gold nanoparticles then bind to the thiol groups to provide up to about 50% coverage of the surface. These nanoparticles serve as seeds for growth of a continuous gold shell by reduction of additional gold precursor. The shell thickness and roughness can be controlled by the size of the nanoparticle seeds as well as by the process of their growth into a continuous shell. By variation of the relative sizes of the latex core and the thickness of the gold overlayer, the plasmon resonance of the nanoshell can be tuned to specific wavelengths across the visible and infrared range of the electromagnetic spectrum, for applications ranging from the construction of photonic crystals to biophotonics. The position and width of the plasmon resonance extinction peak are well-predicted by extended Mie scattering theory.

Covalent decoration of multi-walled carbon nanotubes with silica nanoparticles.
Bottini M, Tautz L, Huynh H, Monosov E, Bottini N, Dawson MI, Bellucci S, Mustelin T.
Chem Commun (Camb). 2005 Feb 14;(6):758-60. Epub 2004 Dec 15.
[ expand abstract ]

We describe a novel tunable approach for the synthesis of carbon nanotube-silica nanobead composites. The control of nanotube morphology and bead size coupled with the versatility of silica chemistry makes these structures an excellent platform for the development of biosensors, or for optical, magnetic and catalytic applications.

Back to Top

Transport Of Surface-Modified Nanoparticles Through Cell Monolayers.
Koch AM, Reynolds F, Merkle HP, Weissleder R, Josephson L.
Chembiochem. 2005 Feb 4;6(2):337-345.
[ expand abstract ]

We synthesized three peptides, a D-polyarginyl peptide (r8(FITC)), a Tat peptide (Tat(FITC)), and a control peptide (Cp(FITC)) and attached each to amino-CLIO, a nanoparticle 30 nm in diameter. We then examined the effective permeability, P(eff), of all six materials through CaCo-2 monolayers. The transport of peptide-nanoparticles was characterized by a lag phase (0-8 h) and a steady-state phase (9-27 h). The steady-state P(eff) values for peptides were in the order r8(FITC)>Tat(FITC)=Cp(FITC). When r8(FITC) and Tat(FITC) peptides were attached to the nanoparticle, they conferred their propensity to traverse cell monolayers onto the nanoparticle, whereas Cp(FITC) did not. Thus, when the r8(FITC) peptide was attached to the amino-CLIO nanoparticle, the resulting peptide-nanoparticle had a P(eff) similar to that of this poly-d-arginyl peptide alone. The P(eff) of r8(FITC)-CLIO (M(W) approximately 1000 kDa) was similar to that of mannitol (M(W)=182 Da), a poorly transported reference substance, with a far lower molecular weight. These results are the first to indicate that the modification of nanoparticles by attachment of membrane-translocating sequence-based peptides can alter nanoparticle transport through monolayers. This suggests that the surface modification of nanoparticles might be a general strategy for enhancing the permeability of drugs and that high-permeability nanoparticle-based therapeutics can be useful in selected pharmaceutical applications.

Single DNA Molecule Detection Using Nanopipettes and Nanoparticles.
Karhanek M, Kemp JT, Pourmand N, Davis RW, Webb CD.
Nano Lett. 2005 Feb;5(2):403-407.
[ expand abstract ]

Single DNA molecules labeled with nanoparticles can be detected by blockades of ionic current as they are translocated through a nanopipette tip formed by a pulled glass capillary. The nanopipette detection technique can provide not only tools for detection and identification of single DNA and protein molecules but also deeper insight and understanding of stochastic interactions of various biomolecules with their environment.

Back to Top

Carbon nanotubes as adsorbent of solid-phase extraction and matrix for laser desorption/ionization mass spectrometry.
Pan C, Xu S, Zou H, Guo Z, Zhang Y, Guo B.
J Am Soc Mass Spectrom. 2005 Feb;16(2):263-70.
[ expand abstract ]

A method with carbon nanotubes functioning both as the adsorbent of solid-phase extraction (SPE) and the matrix for matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) to analyze small molecules in solution has been developed. In this method, 10 muL suspensions of carbon nanotubes in 50% (vol/vol) methanol were added to the sample solution to extract analytes onto surface of carbon nanotubes because of their dramatic hydrophobicity. Carbon nanotubes in solution are deposited onto the bottom of tube with centrifugation. After removing the supernatant fluid, carbon nanotubes are suspended again with dispersant and pipetted directly onto the sample target of the MALDI-MS to perform a mass spectrometric analysis. It was demonstrated by analysis of a variety of small molecules that the resolution of peaks and the efficiency of desorption/ionization on the carbon nanotubes are better than those on the activated carbon. It is found that with the addition of glycerol and sucrose to the dispersant, the intensity, the ratio of signal to noise (S/N), and the resolution of peaks for analytes by mass spectrometry increased greatly. Compared with the previously reported method by depositing sample solution onto thin layer of carbon nanotubes, it is observed that the detection limit for analytes can be enhanced about 10 to 100 times due to solid-phase extraction of analytes in solution by carbon nanotubes. An acceptable result of simultaneously quantitative analysis of three analytes in solution has been achieved. The application in determining drugs spiked into urine has also been realized.

Recent advances with liposomes as pharmaceutical carriers.
Torchilin VP.
Nat Rev Drug Discov. 2005 Feb;4(2):145-60.
[ expand abstract ]

Liposomes - microscopic phospholipid bubbles with a bilayered membrane structure - have received a lot of attention during the past 30 years as pharmaceutical carriers of great potential. More recently, many new developments have been seen in the area of liposomal drugs - from clinically approved products to new experimental applications, with gene delivery and cancer therapy still being the principal areas of interest. For further successful development of this field, promising trends must be identified and exploited, albeit with a clear understanding of the limitations of these approaches.

Back to Top

Preparation of inert magnetic nano-particles for the directed immobilization of antibodies.
Fuentes M, Mateo C, Guisan JM, Fernandez-Lafuente R.
Biosens Bioelectron. 2005 Jan 15;20(7):1380-7.
[ expand abstract ]

Various activated supports (cyanogen bromide, glutaraldehyde, epoxy-chelates, primary amino) were evaluated for the immobilization of IgG anti-horseradish peroxidase. Cyanogen bromide and glutaraldehyde supports greatly reduced the recognition capacity of the antigen, probably due to the incorrect orientation of the antibody on the support. Hetero-functional epoxy-chelate and immobilization by the sugar chain on primary amino groups had little effect on high recognition of the antigen (near to the theoretically expected value). However, the immobilization by the sugar chain resulted in a higher adsorption rate of horseradish peroxidase, possibly due to a favourable orientation on a flexible spacer arm). Antibodies immobilized on aminated surfaces showed two major drawbacks. Firstly, the biological activity of the immobilized antibody sharply decreased over several days when stored at low ionic strength, although this effect could be partially reversed by incubation at high ionic strength. Secondly, a high level of non-specific proteins adsorption on the support surface was observed. Both problems could be successfully resolved by controlling the coating of the support with aldehyde-aspartic-dextran. We propose that the loss of biological activity was related to the ionic adsorption of the immobilized antibody on the support surface, leading to a blocking of the recognition areas. This optimized protocol was applied to the immobilization of IgG anti-horseradish peroxidase from rabbit on magnetic nano-particles. A 10 microg preparation of nano-particles was able to capture more than 75% of the 0.1 microgram of recombinant horseradish peroxidase present in 10 L of crude protein extract (1g/L) from Escherichia coli.

Chemical cross-linking and high-performance fourier transform ion cyclotron resonance mass spectrometry for protein interaction analysis: application to a calmodulin/target peptide complex.
Kalkhof S, Ihling C, Mechtler K, Sinz A.
Anal Chem. 2005 Jan 15;77(2):495-503.
[ expand abstract ]

Chemical cross-linking has proved successful in combination with mass spectrometry as a tool for low-resolution structure determination of proteins. The integration of chemical cross-linking with Fourier transform ion cyclotron resonance (FTICR) mass spectrometry to determine protein interfaces was tested on the calcium-dependent complex between calmodulin (CaM) and a 26-amino acid peptide derived from the skeletal muscle myosin light chain kinase (M13). Different amine-reactive, homobifunctional cross-linkers and a "zero-length" cross-linker were employed. The covalently attached complexes were separated from nonreacted proteins by one-dimensional gel electrophoresis, and the bands of interest were excised and in-gel digested with trypsin. Digestion of the cross-linked complexes resulted in complicated peptide mixtures, which were analyzed by nano-HPLC/nano-ESI-FTICR mass spectrometry. The distance constraints obtained by chemical cross-linking were in agreement with the published NMR structure of the CaM/M13 complex, pointing to residues Lys-18 and Lys-19 of M13 being cross-linked with the central alpha-helix of CaM. Thus, the integrated approach described herein has proven to be an efficient tool for mapping the topology of the CaM/M13 complex. As such it is applicable as a general strategy for the investigation of the spatial organization of protein complexes and complements existing techniques, such as X-ray crystallography and NMR spectroscopy.

Back to Top

Microfluidic chip for peptide analysis with an integrated HPLC column, sample enrichment column, and nanoelectrospray tip.
Yin H, Killeen K, Brennen R, Sobek D, Werlich M, van de Goor T.
Anal Chem. 2005 Jan 15;77(2):527-33.
[ expand abstract ]

Current nano-LC/MS systems require the use of an enrichment column, a separation column, a nanospray tip, and the fittings needed to connect these parts together. In this paper, we present a microfabricated approach to nano-LC, which integrates these components on a single LC chip, eliminating the need for conventional LC connections. The chip was fabricated by laminating polyimide films with laser-ablated channels, ports, and frit structures. The enrichment and separation columns were packed using conventional reversed-phase chromatography particles. A face-seal rotary valve provided a means for switching between sample loading and separation configurations with minimum dead and delay volumes while allowing high-pressure operation. The LC chip and valve assembly were mounted within a custom electrospray source on an ion-trap mass spectrometer. The overall system performance was demonstrated through reversed-phase gradient separations of tryptic protein digests at flow rates between 100 and 400 nL/min. Microfluidic integration of the nano-LC components enabled separations with subfemtomole detection sensitivity, minimal carryover, and robust and stable electrospray throughout the LC solvent gradient.

Chemical reactions inside single-walled carbon nano test-tubes.
Britz DA, Khlobystov AN, Porfyrakis K, Ardavan A, Briggs GA.
Chem Commun (Camb). 2005 Jan 7;(1):37-9.
[ expand abstract ]

We report the application of SWNTs as templates for forming covalent polymeric chains from C(60)O reacting inside SWNTs; the resulting peapod polymer topology is different from the bulk polymer in that it is linear and unbranched.

Back to Top

Nanostructured designs of biomedical materials: applications of cell sheet engineering to functional regenerative tissues and organs.
Kikuchi A, Okano T.
J Control Release. 2005 Jan 3;101(1-3):69-84.
[ expand abstract ]

Biomaterials surface design is critical for control of cell-materials interactions. Materials surface characteristics important to cell-materials interactions are the following: (a) nonfouling surfaces where cells cannot interact; (b) surfaces that interact with cells but do not alter cell morphology or metabolism (passive adhesion processes); and (c) surfaces that strongly interact with cells and cell-surface receptors to alter cell shape after metabolic interactions (active adhesion). In this paper, we briefly discuss the relationship between materials surface characteristics and cells for biomaterials designs in these categories. We have extensively investigated the thermoresponsive polymer, poly(N-isopropylacrylamide) (PIPAAm), as grafted surfaces allowing recovery of confluent cell monolayers as contiguous living cell sheets for tissue engineering applications. Cellular interactions with PIPAAm-grafted surfaces can be regulated vertically using the thickness of the PIPAAm-grafted layers in nanometer-scale levels, as well as laterally (spatially) using nano-patterned PIPAAm chemistry on various other surface chemistries. PIPAAm-grafted surfaces with 15-20-nm thick layers exhibit temperature-dependent cell adhesion/detachment control, while surfaces with PIPAAm layer thicknesses of more than 30 nm do not support cell adhesion. These changes in cell adhesion are explained by the limited mobility of the surface grafted polymer chains as a function of grafting, hydration, and temperature.

Reagentless electrochemical biosensor based on the multi-wall carbon nanotubes and nanogold particles composite film.
Zhu JJ, Xu JZ, Hu Z, Chen HY.
Front Biosci. Front Biosci 2005 Jan 1;10:521-9.
[ expand abstract ]

A novel method was used to prepare the nano-composite by assembling nanogold (NG) particles on the multiwall carbon nanotubes (MWNTs) surface. The nano-composite could be immobilized on a glassy carbon (GC) electrode to get a novel modified electrode. The electrode can easily immobilize the horseradish peroxidase (HRP) molecules to construct a reagentless biosensor. The NG particles in the composite film have a good biological compatibility. And due to the existence of quinone groups on the MWNTs surface, the MWNTs can promote the electron transfer between enzymes and electrode surface. The biosensor shows a good stability and responds to H2O2 in the range from 2.0 microM to 3.5 mM with a detection limit of 1.0 microM.

Back to Top

Bright and Stable Core-Shell Fluorescent Silica Nanoparticles.
Ow H, Larson DR, Srivastava M, Baird BA, Webb WW Wiesner U.
Nano Lett. 2005 Jan;5(1):113-117.
[ expand abstract ]

A class of highly fluorescent and photostable core-shell nanoparticles from a modified Stöber synthesis in the size range of 20-30 nm is described. These nanoparticles are monodisperse in solution, 20 times brighter, and more photostable than their constituent fluorophore, and are amenable to specific labeling of biological macromolecules for bioimaging experiments. The photophysical characteristics of the encapsulated fluorophores differ from their solution properties. This raises the possibility of tuning nanoparticle structure toward enhanced radiative properties, making them an attractive material platform for a diverse range of applications.

Large-scale fabrication and characterization of Cd-doped ZnO nanocantilever arrays.
Zhou SM, Meng XM, Zhang XH, Fan X, Zou K, Wu SK, Lee ST.
Micron. 2005;36(1):55-9.
[ expand abstract ]

We demonstrate bulk synthesis of highly crystalline Cd-doped ZnO nanocantilever arrays (CZNAs) using Cd and Zn powders at 600 degrees C, which is characterized via scanning electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy, selected area electron diffraction, and high resolution TEM. The results show that the as-prepared CZNAs have diameters of about 15-50nm, and lengths up to 400nm and the corresponding process of growth is suggested for conventional vapor solid mechanism.

Back to Top

2004

Surface-enhanced Raman scattering on tunable plasmonic nanoparticle substrates.
Jackson JB, Halas NJ.
Proc Natl Acad Sci U S A. 2004 Dec 28;101(52):17930-5
[ expand abstract ]

Au and Ag nanoshells are investigated as substrates for surface-enhanced Raman scattering (SERS). We find that SERS enhancements on nanoshell films are dramatically different from those observed on colloidal aggregates, specifically that the Raman enhancement follows the plasmon resonance of the individual nanoparticles. Comparative finite difference time domain calculations of fields at the surface of smooth and roughened nanoshells reveal that surface roughness contributes only slightly to the total enhancement. SERS enhancements as large as 2.5 x 10(10) on Ag nanoshell films for the nonresonant molecule p-mercaptoaniline are measured.

Noble-metal nanoparticles directly conjugated to globular proteins.
Burt JL, Gutierrez-Wing C, Miki-Yoshida M, Jose-Yacaman M.
Langmuir. 2004 Dec 21;20(26):11778-83.
[ expand abstract ]

We report the synthesis of gold nanoparticles directly conjugated to bovine serum albumin protein by chemical reduction in aqueous solution. Transmission electron microscopy reveals that the gold nanoparticles are well dispersed with an average diameter less than 2 nm, and elemental analysis verifies the composition of the gold-protein conjugates. Infrared spectroscopy confirms that the polypeptide backbone is not cleaved during the conjugation process and that the side chain functional groups remain intact. Raman spectroscopy demonstrates that the disulfide bonds in the conjugated protein are broken and thus are available for interaction with the nanoparticle surface. This synthesis method is a new technique for directly attaching gold nanoparticles to macromolecular proteins.

Back to Top

Quantum dot-antibody and aptamer conjugates shift fluorescence upon binding bacteria.
Dwarakanath S, Bruno JG, Shastry A, Phillips T, John A, Kumar A, Stephenson LD.
Biochem Biophys Res Commun. 2004 Dec 17;325(3):739-43.
[ expand abstract ]

CdSe/ZnS quantum dots (QDs) exhibited fluorescence emission blue shifts when conjugated to antibodies or DNA aptamers that are bound to bacteria. The intensity of the shifted emission peak increased with the number of bound bacteria. Curiously, the emission was consistently shifted to approximately 440-460 nm, which is distinctly different from the major component of the natural fluorescence spectrum of these QDs. This minor emission peak can grow upon conjugation to antibodies or aptamers and subsequent binding to bacterial cell surfaces. We hypothesize that the wavelength shift is due to changes in the chemical environment of the QD conjugates when they encounter the bacterial surface and may be due to physical deformation of the QD that changes the quantum confinement state. Regardless of the mechanism, these remarkable emission wavelength shifts of greater than 140 nm in some cases strongly suggest new applications for QD-receptor conjugates.

Optimization of dye-doped silica nanoparticles prepared using a reverse microemulsion method.
Bagwe RP, Yang C, Hilliard LR, Tan W.
Langmuir. 2004 Sep 14;20(19):8336-42.
[ expand abstract ]

Fluorescent labeling based on silica nanoparticles facilitates unique applications in bioanalysis and bioseparation. Dye-doped silica nanoparticles have significant advantages over single-dye labeling in signal amplification, photostability and surface modification for various biological applications. We have studied the formation of tris(2,2'-bipyridyl)dichlororuthenium(II) (Ru(bpy)) dye-doped silica nanoparticles by ammonia-catalyzed hydrolysis of tetraethyl orthosilicate (TEOS) in water-in-oil microemulsion. The fluorescence spectra, particle size, and size distribution of Ru(bpy) dye-doped silica nanoparticles were examined as a function of reactant concentrations (TEOS and ammonium hydroxide), nature of surfactant molecules, and molar ratios of water to surfactant (R) and cosurfactant to surfactant (p). The particle size and fluorescence spectra were dependent upon the type of microemulsion system chosen. The particle size was found to decrease with an increase in concentration of ammonium hydroxide and increase in water to surfactant molar ratio (R) and cosurfactant to surfactant molar ratio (p). This optimization study of the preparation of dye-doped silica nanoparticles provides a fundamental knowledge of the synthesis and optical properties of Ru(bpy) dye-doped silica nanoparticles. With this information, these nanoparticles can be easily manipulated, with regard to particle size and size distribution, and bioconjugated as needed for bioanalysis and bioseparation applications.

Back to Top

Preparation and stability of lipid-coated nanocapsules of cisplatin: anionic phospholipid specificity.
Velinova MJ, Staffhorst RW, Mulder WJ, Dries AS, Jansen BA, de Kruijff B, de Kroon AI.
Biochim Biophys Acta. 2004 May 27;1663(1-2):135-42.
[ expand abstract ]

Cisplatin nanocapsules represent a novel lipid formulation of the anti-cancer drug cis-diamminedichloroplatinum(II) (cisplatin), in which nanoprecipitates of cisplatin are coated by a phospholipid bilayer consisting of a 1:1 mixture of zwitterionic phosphatidylcholine (PC) and negatively charged phosphatidylserine (PS). Cisplatin nanocapsules are characterized by an unprecedented cisplatin-to-lipid ratio and exhibit increased in vitro cytotoxicity compared to the free drug [Nat. Med. 8, (2002) 81]. In the present study, the stability of the cisplatin nanocapsules was optimized by varying the lipid composition of the bilayer coat and monitoring in vitro cytotoxicity and the release of contents during incubations in water and in mouse serum. The release of cisplatin from the PC/PS (1:1) nanocapsules in water increased with increasing temperature with a t(1/2) of 6.5 h at 37 degrees C. At 4 degrees C, cisplatin was retained in the nanocapsules for well over 8 days. Replacement of PS by either phosphatidylglycerol or phosphatidic acid revealed that nanocapsules prepared of PS were more stable, which was found to be due to the ability of PS to form a stable cisplatin-PS coordination complex. Mouse serum had a strong destabilizing effect on the cisplatin nanocapsules. The PC/PS formulation lost over 80% of cisplatin within minutes after resuspension in serum. Incorporation of poly(ethylene glycol 2000) (PEG)-derivatized phosphatidylethanolamine and cholesterol in the bilayer coat extended the lifetime of the cisplatin nanocapsules in mouse serum to almost an hour. The results demonstrate that specificity in the interaction of cisplatin with anionic phospholipids is an important criterium for the formation and stability of cisplatin nanocapsules.

Object-oriented design tools for supramolecular devices and biomedical nanotechnology.
Lee SC, Bhalerao K, Ferrari M.
Ann N Y Acad Sci..2004 May;1013:110-23.
[ expand abstract ]

Nanotechnology provides multifunctional agents for in vivo use that increasingly blur the distinction between pharmaceuticals and medical devices. Realization of such therapeutic nanodevices requires multidisciplinary effort that is difficult for individual device developers to sustain, and identification of appropriate collaborations outside ones own field can itself be challenging. Further, as in vivo nanodevices become increasingly complex, their design will increasingly demand systems level thinking. System engineering tools such as object-oriented analysis, object-oriented design (OOA/D) and unified modeling language (UML) are applicable to nanodevices built from biological components, help logically manage the knowledge needed to design them, and help identify useful collaborative relationships for device designers. We demonstrate the utility of these systems engineering tools by reverse engineering an existing molecular device (the bacmid molecular cloning system) using them, and illustrate how object-oriented approaches identify fungible components (objects) in nanodevices in a way that facilitates design of families of related devices, rather than single inventions. We also explore the utility of object-oriented approaches for design of another class of therapeutic nanodevices, vaccines. While they are useful for design of current nanodevices, the power of systems design tools for biomedical nanotechnology will become increasingly apparent as the complexity and sophistication of in vivo nanosystems increases. The nested, hierarchical nature of object-oriented approaches allows treatment of devices as objects in higher-order structures, and so will facilitate concatenation of multiple devices into higher-order, higher-function nanosystems.

Back to Top

Plasmon hybridization in spherical nanoparticles.
Prodan E, Nordlander P.
J Chem Phys. 2004 Mar 15;120(11):5444-54.
[ expand abstract ]

We show that the plasmon resonances in single metallic nanoshells and multiple concentric metallic shell particles can be understood in terms of interaction between the bare plasmon modes of the individual surfaces of the metallic shells. The interaction of these elementary plasmons results in hybridized plasmons whose energy can be tuned over a wide range of optical and infrared wavelengths. The approach can easily be generalized to more complex systems, such as dimers and small nanoparticle aggregates.

Biocompatibility of micro- and nano-particles in the colon. Part II.
Gatti AM.
Biomaterials. 2004 Feb;25(3):385-92.
[ expand abstract ]

Pathological colonic tissues were investigated with an Environmental Scanning Electron Microscope technique to verify the presence of inorganic, non-biodegradable pollutants, i.e. micro- and nano-debris of exogenous origin, after debris in liver and kidney had been discovered. In all, 18 samples of colon tissues affected by cancer and Crohn's disease were evaluated and found in all the cases to contain micro- and nano-particles. Their chemistry, detected with an X-ray microprobe, indicated a heterogeneous nature, whereas the size of the particles was homogeneous. Three control samples of healthy, young, cadavers were analysed and showed the absence of debris within the normal, healthy colon mucosa. The study reveals the presence of particulate debris, generally considered as biocompatible, in pathological specimens of human colon. The findings suggest a possible link between the presence of such particles and the underlying pathology in the cases analysed.

Back to Top

Nanoshell-enabled photonics-based imaging and therapy of cancer.
Loo C, Lin A, Hirsch L, Lee MH, Barton J, Halas N, West J, Drezek R.
Technol Cancer Res Treat. 2004 Feb;3(1):33-40.
[ expand abstract ]

Metal nanoshells are a novel type of composite spherical nanoparticle consisting of a dielectric core covered by a thin metallic shell which is typically gold. Nanoshells possess highly favorable optical and chemical properties for biomedical imaging and therapeutic applications. By varying the relative the dimensions of the core and the shell, the optical resonance of these nanoparticles can be precisely and systematically varied over a broad region ranging from the near-UV to the mid-infrared. This range includes the near-infrared (NIR) wavelength region where tissue transmissivity peaks. In addition to spectral tunability, nanoshells offer other advantages over conventional organic dyes including improved optical properties and reduced susceptibility to chemical/thermal denaturation. Furthermore, the same conjugation protocols used to bind biomolecules to gold colloid are easily modified for nanoshells. In this article, we first review the synthesis of gold nanoshells and illustrate how the core/shell ratio and overall size of a nanoshell influences its scattering and absorption properties. We then describe several examples of nanoshell-based diagnostic and therapeutic approaches including the development of nanoshell bioconjugates for molecular imaging, the use of scattering nanoshells as contrast agents for optical coherence tomography (OCT), and the use of absorbing nanoshells in NIR thermal therapy of tumors.

International nanotechnology development in 2003: Country, institution, and technology field analysis based on USPTO patent database.
Huang Z, Chen H, Chen ZK, Roco MC.
J Nanoparticle Research. 2004; 6:325-354
[ expand abstract ]

Nanoscale science and engineering (NSE) have seen rapid growth and expansion in new areas in recent years. This paper provides an international patent analysis using the U.S. Patent and Trademark Office (USPTO) data searched by keywords of the entire text: title, abstract, claims, and specifications. A fraction of these patents fully satisfy the National Nanotechnology Initiative definition of nanotechnology (which requires exploiting specific phenomena and direct manipulation at the nanoscale), while others only make use of NSE tools and methods of investigation. In previous work we proposed an integrated patent analysis and visualization framework of patent content mapping for the NSE field and of knowledge flow pattern identification until 2002. In this paper, the results are updated for 2003, and the new trends are presented.

The number of USPTO patents originated from all countries that include nanotechnology-related keywords in 2003 is about 8600, an increase of about 50% over the last 3 years, which is significantly larger than the increase of about 4% for patents in all technology fields (USPTO, 2004). The top five countries are U.S. (5228 patents in 2004), Japan (926), Germany (684), Canada (244) and France (183). Fastest growing are the Republic of Korea (84 patents in 2003) and Netherlands (81). For the first time in 2003, four electronic companies have reached the top five institutions: IBM (198 patents), Micron Technologies (129), Advanced Micro Devices (128), Intel (90) and University of California (89). However, overall, the single technology field ''Chemistry: molecular biology and microbiology'' and chemical industry remain in the lead. The citation networks show an increase of international interactions, and a relative change of the role of various countries, institutions and technological fields in time.

Back to Top

2003

A hybridization model for the plasmon response of complex nanostructures.
Prodan E, Radloff C, Halas NJ, Nordlander P.
Science. 2003 Oct 17;302(5644):419-22.
[ expand abstract ]

We present a simple and intuitive picture, an electromagnetic analog of molecular orbital theory, that describes the plasmon response of complex nanostructures of arbitrary shape. Our model can be understood as the interaction or "hybridization" of elementary plasmons supported by nanostructures of elementary geometries. As an example, the approach is applied to the important case of a four-layer concentric nanoshell, where the hybridization of the plasmons of the inner and outer nanoshells determines the resonant frequencies of the multilayer nanostructure.

Folic acid-conjugated nanostructured materials designed for cancer cell targeting.
Pan D, Turner JL, Wooley KL.
Chem Commun (Camb). 2003 Oct 7;(19):2400-1.
[ expand abstract ]

Shell cross-linked nanoparticles (SCKs) constitute a unique class of materials with amphiphilic core-shell morphology; SCKs are characterised by their structural integrity and available functionality to attach receptor-recognising or receptor-specific ligands on the shell surface and, therefore, hold great potential in drug delivery applications; in an attempt to develop novel, cancer cell specific delivery vehicles, folate receptor targeted SCKs have been prepared.

Back to Top

Nanoparticles of compacted DNA transfect postmitotic cells.
Liu G, Li D, Pasumarthy MK, Kowalczyk TH, Gedeon CR, Hyatt SL, Payne JM, Miller TJ, Brunovskis P, Fink TL, Muhammad O, Moen RC, Hanson RW.
J Biol Chem. 2003 Aug 29;278(35):32578-86. Epub 2003 Jun 14.
[ expand abstract ]

Charge-neutral DNA nanoparticles have been developed in which single molecules of DNA are compacted to their minimal possible size. We speculated that the small size of these DNA nanoparticles may facilitate gene transfer in postmitotic cells, permitting nuclear uptake across the 25-nm nuclear membrane pore. To determine whether DNA nanoparticles can transfect nondividing cells, growth-arrested neuroblastoma and hepatoma cells were transfected with DNA/liposome mixtures encoding luciferase. In both models, growth-arrested cells were robustly transfected by compacted DNA (6,900-360-fold more than naked DNA). To evaluate mechanisms responsible for enhanced transfection, HuH-7 cells were microinjected with naked or compacted plasmids encoding enhanced green fluorescent protein. Cytoplasmic microinjection of DNA nanoparticles generated a approximately 10-fold improvement in transgene expression as compared with naked DNA; this enhancement was reversed by the nuclear pore inhibitor, wheat germ agglutinin. To determine the upper size limit for gene transfer, DNA nanoparticles of various sizes were microinjected into the cytoplasm. A marked decrease in transgene expression was observed as the minor ellipsoidal diameter approached 25 nm. In summary, suitably sized DNA nanoparticles productively transfect growth arrested cells by traversing the nuclear membrane pore.

Gold and silver nanoparticles: a class of chromophores with colors tunable in the range from 400 to 750 nm.
Sun Y, Xia Y.
Analyst. 2003 Jun;128(6):686-91.
[ expand abstract ]

This paper presents several solution-phase methods for the large-scale synthesis of metal nanoparticles with controllable compositions (e.g., spherical nanoparticles of gold/silver alloys), morphologies (e.g., nanospheres, triangular nanoplates, circular nanodisks, and nanocubes of silver), and structures (e.g., solid vs. hollow colloids). Spectral measurements indicated that the positions of surface plasmon resonance (SPR) bands for these nanoparticles could be tuned by varying all these parameters. The number of SPR peaks was found to increase as the symmetry of the nanoparticles decreased. In addition to their use as chromophores with strong extinction coefficients, these nanoparticles could serve as a platform to probe binding events of chemical and biochemical species on their surfaces. Gold nanoshells with hollow interiors were, in particular, shown to exhibit a much higher sensitivity to environmental changes than gold solid colloids with roughly the same size.

Back to Top

Self-assembled nanoparticles of hydrophobically-modified polysaccharide bearing vitamin H as a targeted anti-cancer drug delivery system.
Na K, Bum Lee T, Park KH, Shin EK, Lee YB, Choi HK.
Eur J Pharm Sci. 2003 Feb;18(2):165-73.
[ expand abstract ]

Vitamin H (biotin) was incorporated into a hydrophobically modified polysaccharide, pullulan acetate (PA), in order to improve the cancer-targeting activity and internalization of self-assembled nanoparticles. The biotinylated pullulan acetate (BPA) nanoparticles were prepared by a diafiltration method and the mean diameter was approximately 100 nm. Three samples of biotinylated pullulan acetate (BPA), comprising 7 (BPA 1), 20 (BPA 2), and 39 (BPA 3) vitamin H groups per 100 anhydroglucose units of PA, were synthesized. The critical aggregation concentrations (CAC) of the BPA nanoparticles in distilled water were 3.1 x 10(-3), 4.3 x 10(-3) and 6.8 x 10(-3) mg/ml for BPA 1, BPA 2, and BPA 3, respectively. Adriamycin (ADR) was loaded into the BPA nanoparticles as a model drug. The loading efficiencies and ADR content in the BPA nanoparticles decreased with increasing vitamin H content due to a lower hydrophobicity. The RITC-labeled BPA nanoparticles exhibited very strong adsorption to the HepG2 cells, while the RITC-labeled PA nanoparticles did not show any significant interaction. The degree of the interaction increased with increasing vitamin H content. Confocal laser microscopy also revealed that internalization of the BPA nanoparticles into the cancer cells depended on the vitamin H content.

Investigation on Tc tuned nano particles of magnetic oxides for hyperthermia applications.
Giri J, Ray A, Dasgupta S, Datta D, Bahadur D.
Biomed Mater Eng. 2003;13(4):387-99.
[ expand abstract ]

Superparamagnetic as well as fine ferrimagnetic particles such as Fe3O4, have been extensively used in magnetic field induced localized hyperthermia for the treatment of cancer. The magnetic materials with Curie temperature (Tc) between 42 and 50 degrees C, with sufficient biocompatibility are the best candidates for effective treatment such that during therapy it acts as in vivo temperature control switch and thus over heating could be avoided. Ultrafine particles of substituted ferrite Co(1-a)Zn(a)Fe2O4 and substituted yttrium-iron garnet Y3Fe(5-x)Al(x)O12 have been prepared through microwave refluxing and citrate-gel route respectively. Single-phase compounds were obtained with particle size below 100 nm. In order to make these magnetic nano particles biocompatible, we have attempted to coat these above said composition by alumina. The coating of alumina was done by hydrolysis method. The coating of hydrous aluminium oxide has been done over the magnetic particles by aging the preformed solid particles in the solution of aluminium sulfate and formamide at elevated temperatures. In vitro study is carried out to verify the innocuousness of coated materials towards cells. In vitro biocompatibility study has been carried out by cell culture method for a period of three days using human WBC cell lines. Study of cell counts and SEM images indicates the cells viability/growth. The in vitro experiments show that the coated materials are biocompatible.

Back to Top

Engineered nanomaterials for biophotonics applications: improving sensing, imaging, and therapeutics.
West JL, Halas NJ.
Annu Rev Biomed Eng. 2003;5:285-92.
[ expand abstract ]

Advances in chemistry and physics are providing an expanding array of nanostructured materials with unique and powerful optical properties. These nanomaterials provide a new set of tools that are available to biomedical engineers, biologists, and medical scientists who seek new tools as biosensors and probes of biological fluids, cells, and tissue chemistry and function. Nanomaterials are also being used to develop optically controlled devices for applications such as modulated drug delivery as well as optical therapeutics. This review discusses applications that have been successfully demonstrated using nanomaterials including semiconductor nanocrystals, gold nanoparticles, gold nanoshells, and silver plasmon resonant particles.

2002

Engineering tumor-targeted gadolinium hexanedione nanoparticles for potential application in neutron capture therapy.
Oyewumi MO, Mumper RJ.
Bioconjug Chem. 2002 Nov-Dec;13(6):1328-35
[ expand abstract ]

Microemulsions (oil-in-water) have been employed as templates to engineer nanoparticles containing high concentrations of gadolinium for potential application in neutron capture therapy of tumors. Gadolinium hexanedione (GdH), synthesized by complexation of Gd(3+) with 2,4-hexanedione, was used as the nanoparticle matrix alone or in combination with either emulsifying wax or PEG-400 monostearate. Solid nanoparticles (<125 nm size) were obtained by simple cooling of the microemulsions prepared at 60 degrees C to room temperature in one vessel. The feasibility of tumor targeting via folate receptors was studied. A folate ligand was synthesized by chemically linking folic acid to distearoylphosphatidylethanolamine (DSPE) via a poly(ethylene glycol) (PEG; MW 3350) spacer. To obtain folate-coated nanoparticles, the folate ligand (0.75% w/w to 15% w/w) was added to either the microemulsion templates at 60 degrees C or nanoparticle suspensions at 25 degrees C. Efficiencies of folate ligand attachment/adsorption to nanoparticle formulations were monitored by gel permeation chromatography. Cell uptake studies were carried out in KB cells (human nasopharyngeal epidermal carcinoma cell line), known to overexpress folate receptors. The uptake of folate-coated nanoparticles was about 10-fold higher than uncoated nanoparticles after 30 min at 37 degrees C. The uptake of folate-coated nanoparticles at 4 degrees C was 20-fold lower than the uptake at 37 degrees C and comparable to the uptake of uncoated nanoparticles at 37 degrees C. Folate-mediated endocytosis was further verified by the inhibition of folate-coated nanoparticles uptake by free folic acid. It was observed that folate-coated nanoparticles uptake decreased to approximately 2% of its initial value with the coincubation of 0.001 mM of free folic acid. The results suggested that these tumor-targeted nanoparticles containing high concentrations of Gd may have potential for neutron capture therapy.

Back to Top

Nanoparticles in cancer therapy and diagnosis.
Brigger I, Dubernet C, Couvreur P.
Adv Drug Deliv Rev. 2002 Sep 13;54(5):631-51.
[ expand abstract ]

Numerous investigations have shown that both tissue and cell distribution profiles of anticancer drugs can be controlled by their entrapment in submicronic colloidal systems (nanoparticles). The rationale behind this approach is to increase antitumor efficacy, while reducing systemic side-effects. This review provides an update of tumor targeting with conventional or long-circulating nanoparticles. The in vivo fate of these systems, after intravascular or tumoral administration, is discussed, as well as the mechanism involved in tumor regression. Nanoparticles are also of benefit for the selective delivery of oligonucleotides to tumor cells. Moreover, certain types of nanoparticles showed some interesting capacity to reverse MDR resistance, which is a major problem in chemotherapy. The first experiments, aiming to decorate nanoparticles with molecular ligand for 'active' targeting of cancerous cells, are also discussed here. The last part of this review focus on the application of nanoparticles in imaging for cancer diagnosis.

Microfabrication technology for pancreatic cell encapsulation.
Desai TA.
Expert Opin Biol Ther. 2002 Aug;2(6):633-46.
[ expand abstract ]

The inadequacy of conventional insulin therapy for the treatment of Type I diabetes has stimulated research on several therapeutic alternatives, including insulin pumps and controlled-release systems for insulin. One of the most physiological alternatives to insulin injections is the transplantation of insulin-secreting cells. It is the beta-cells of the islets that secrete insulin in response to increasing blood glucose concentrations. Ideally, transplantation of such cells (allografts or xenografts) could restore normoglycaemia. However, as with most tissue or cellular transplants, the cellular grafts, particularly xenografts, are subject to immunorejection in the absence of chronic immunosuppression. Thus, it is of great interest to develop new technologies that may be used for insulin delivery or pancreatic cell transplantation. This review describes a new approach to cellular delivery based on micro- and nanotechnology. Utilising this approach, nanoporous biocapsules are bulk and surface micromachined to present uniform and well-controlled pore sizes as small as 7 nm, tailored surface chemistries and precise microarchitectures, in order to provide immunoisolating microenvironments for cells. Such a design may overcome some of the limitations associated with conventional encapsulation and delivery technologies, including chemical instabilities, material degradation or fracture and broad membrane pore sizes.

Back to Top

Rapid endo-lysosomal escape of poly(DL-lactide-co-glycolide) nanoparticles: implications for drug and gene delivery.
Panyam J, Zhou WZ, Prabha S, Sahoo SK, Labhasetwar V.
FASEB J. 2002 Aug;16(10):1217-26.
[ expand abstract ]

The endo-lysosomal escape of drug carriers is crucial to enhancing the efficacy of their macromolecular payload, especially the payloads that are susceptible to lysosomal degradation. Current vectors that enable the endo-lysosomal escape of macromolecules such as DNA are limited by their toxicity and by their ability to carry only limited classes of therapeutic agents. In this paper, we report the rapid (<10 min) endo-lysosomal escape of biodegradable nanoparticles (NPs) formulated from the copolymers of poly(DL-lactide-co-glycolide) (PLGA). The mechanism of rapid escape is by selective reversal of the surface charge of NPs (from anionic to cationic) in the acidic endo-lysosomal compartment, which causes the NPs to interact with the endo-lysosomal membrane and escape into the cytosol. PLGA NPs are able to deliver a variety of therapeutic agents, including macromolecules such as DNA and low molecular weight drugs such as dexamethasone, intracellularly at a slow rate, which results in a sustained therapeutic effect. PLGA has a number of advantages over other polymers used in drug and gene delivery including biodegradability, biocompatibility, and approval for human use granted by the U.S. Food and Drug Administration. Hence PLGA is well suited for sustained intracellular delivery of macromolecules.

Coupling of optical characterization with particle and network synthesis for biomedical applications.
Song L, Liu T, Liang D, Wu C, Zaitsev VS, Dresco PA, Chu B.
J Biomed Opt. 2002 Jul;7(3):498-506.
[ expand abstract ]

Polymeric microspheres containing a magnetic core have been used in cancer therapy for biophysical targeting of antitumor agents and in magnetic resonance imaging as contrasting agents. For the Human Genome Project, deoxyribose nucleic acid (DNA) capillary electrophoresis has become the most widely used analytical technique where a key component is the design of an effective separation medium. The synthesis and optical characterization of polymeric coated superparamagnetic nanoparticles and of (self-assembled) polymer networks by means of a range of physical techniques, including laser light scattering and laser-induced fluorescence detection, are presented. (1) Polymeric microspheres with a superparamagnetic core. A water-in-oil microemulsion approach has been used successfully to synthesize the superparamagnetic core and the polymeric microsphere in one continuous step. The synthesis permits us to control the magnetic nanoparticle size and the thickness of the hydrogel, ranging from 80 to 320 nm. Magnetite concentration in the microspheres, calculated by vibrating-sample magnetometry, was found to be up to 3.3 wt %. The internal structure of the microspheres, as observed by atomic force microscopy, confirmed a core-shell model. (2) Development of new separation media for DNA capillary electrophoresis. Block copolymers in selective solvents can self-assemble to form supramolecular structures in solution. The nanostructures can be characterized in the dilute concentration regime by means of laser light scattering. At semidilute concentrations, the mesh size, the supramolecular structure, and the surface morphology can be investigated by means of small angle x-ray scattering and atomic force microscopy. The structural knowledge and the information on chain dynamics can then be correlated with electrophoresis using laser-induced fluorescence detection to provide a deeper understanding for the development of new separation media.

Back to Top

Self-assembled hydrogel nanoparticles responsive to tumor extracellular pH from pullulan derivative/sulfonamide conjugate: characterization, aggregation, and adriamycin release in vitro.
Na K, Bae YH.
Pharm Res.2002 May;19(5):681-8.
[ expand abstract ]

PURPOSE: To investigate some physicochemical properties of self-assembled hydrogel nanoparticles of pullulan acetate (PA) and sulfonamide conjugates, as a potential tumor targeting drug carrier responsive to tumor extracellular pH. METHODS: A new class of pH-responsive polymers was synthesized by conjugating a sulfonamide, sulfadimethoxine (SDM), to succinylated pullulan acetate (coohPA). The polymers formed self-assembled PA/SDM hydrogel nanoparticles in aqueous media, which was confirmed by fluorometry and field emission-scanning electron microscopy. The pH-dependent behavior of the nanoparticles was examined by measuring transmittance, particle size and zeta potential. Adriamycin (ADR) was tested for loading into and release from the nanoparticles at various pHs. RESULTS: The mean diameters of all PA/SDM nanoparticles tested were <70 nm. with a unimodal size distribution. The critical aggregation concentrations at pH 9.0 were as low as 3.16 microg/mL. The nanoparticles showed good stability at pH 7.4, but shrank and aggregated below pH 7.0. The ADR release rate from the PA/SDM nanoparticles was pH-dependent around physiological pH and significantly enhanced below a pH of 6.8. CONCLUSIONS: The pH-responsive PA/SDM nanoparticles may provide some advantages for targeted anti-cancer drug delivery due to the particle aggregation and enhanced drug release rates at tumor pH.

Surface modification of superparamagnetic magnetite nanoparticles and their intracellular uptake.
Zhang Y, Kohler N, Zhang M.
Biomaterials. 2002 Apr;23(7):1553-61.
[ expand abstract ]

Superparamagnetic magnetite nanoparticles were surface-modified with poly (ethylene glycol) (PEG) and folic acid, respectively, to improve their intracellular uptake and ability to target specific cells. PEG and folic acid were successfully immobilized on the surfaces of magnetite nanoparticles and characterized using fourier transform infrared spectra. The nanoparticle internalization into mouse macrophage (RAW 264.7) and human breast cancer (BT20) cells was visualized using both fluorescence and confocal microscopy, and quantified by inductively coupled plasma emission spectroscopy (ICP). After the cells were cultured for 48 h in the medium containing the nanoparticles modified with PEG or folic acid, the results of fluorescence and confocal microscopy showed that the nanoparticles were internalized into the cells. The ICP measurements indicated that the uptake amount of PEG-modified nanoparticles into macrophage cells was much lower than that of unmodified nanoparticles. while folic acid modification did not change the amount of the uptake. However, for breast cancer cells, both PEG and folic acid modification facilitated the nanoparticle internalization into the cells. Therefore, PEG and folic acid modification of magnetite nanoparticles could be used to resist the protein adsorption and thus avoid the particle recognition by macrophage cells, and to facilitate the nanoparticle uptake to specific cancer cells for cancer therapy and diagnosis.

Back to Top

In vitro cellular accumulation of gadolinium incorporated into chitosan nanoparticles designed for neutron-capture therapy of cancer.
Shikata F, Tokumitsu H, Ichikawa H, Fukumori Y.
Eur J Pharm Biopharm.2002 Jan;53(1):57-63.
[ expand abstract ]

The accumulation of gadolinium loaded as gadopentetic acid (Gd-DTPA) in chitosan nanoparticles (Gd-nanoCPs), which were designed for gadolinium neutron-capture therapy (Gd-NCT) for cancer, was evaluated in vitro in cultured cells. Using L929 fibroblast cells, the Gd accumulation for 12 h at 37 degrees C was investigated at Gd concentrations lower than 40 ppm. The accumulation leveled above 20 ppm and reached 18.0+/-2.7 (mean+/-S.D.) microg Gd/10(6) cells at 40 ppm. Furthermore, the corresponding accumulations in B16F10 melanoma cells and SCC-VII squamous cell carcinoma, which were used in the previous Gd-NCT trials in vivo, were 27.1+/-2.9 and 59.8+/-9.8 microg Gd/10(6) cells, respectively, hence explaining the superior growth-suppression in the in vivo trials using SCC-VII cells. The accumulation of Gd-nanoCPs in these cells was 100-200 times higher in comparison to dimeglumine gadopentetate aqueous solution (Magnevist), a magnetic resonance imaging contrast agent. The endocytic uptake of Gd-nanoCPs, strongly holding Gd-DTPA, was suggested from transmission electron microscopy and comparative studies at 4 degrees C and with the solution system. These findings indicated that Gd-nanoCPs had a high affinity to the cells, probably contributing to the long retention of Gd in tumor tissue and leading to the significant suppression of tumor growth in the in vivo studies that were previously reported.

Nanocapsule technology: a review.
Couvreur P, Barratt G, Fattal E, Legrand P, Vauthier C.
Crit Rev Ther Drug Carrier Syst. 2002;19(2):99-134.
[ expand abstract ]

Nanocapsules are submicroscopic colloidal drug carrier systems composed of an oily or an aqueous core surrounded by a thin polymer membrane. Two technologies can be used to obtain such nanocapsules: the interfacial polymerization of a monomer or the interfacial nanodeposition of a preformed polymer. This article is an extended review of these nanocapsule technologies and their applications for the treatment of various diseases (including cancer and infections).

Back to Top

Combined vascular targeted imaging and therapy: a paradigm for personalized treatment.
Li KC, Guccione S, Bednarski MD.
J Cell Biochem Suppl. 2002;39:65-71.
[ expand abstract ]

In order to be successful in personalizing treatment, methods for selecting patients as well as good surrogate biomarkers for monitoring the effects of treatment are required in addition to development of an efficacious targeted therapy. We have developed a polymerized nanoparticle platform technology that will allow us to put different targeting moieties on the surface of the particles in addition to loading the particles with different contrast and therapeutic agents. We have proven that these nanoparticles can be targeted to endothelial receptors and different payloads of contrast and therapeutic agents have been delivered to target cells with high target to background ratios. Using this combined vascular targeted imaging and therapy approach, we are optimistic that personalized treatment regimens can be developed for different disease processes such as cancer, inflammation, and ischemia.