Benedictine University, Chemistry, Lisle, IL 60532-0900
Enzyme electrodes are biosensors that use the selectivity of the enzyme with the sensitivity of the electrochemical detection. Enzyme electrodes have increased usage as they are simple to construct, inexpensive, selective, regenerate easily and are reusable. However, the less commonly studied rotating enzyme electrodes (RDEE) provides continuous stirring of the bulk solution and faster transport of the analyte to the electrode surface resulting in shorter detection times and faster overall analysis. The RDEEs are also less likely to suffer from electrode fouling in biological sample matrix, a major limitation of the existing enzyme electrodes. In this study, rotating disk electrodes modified with glucose oxidase (GOx) were constructed as working electrodes for the amperometric detection of β-D-glucose. The enzyme glucose oxidase (GOx) is highly specific for β-D-glucose and was directly immobilized onto the Pt electrode surface through electrodeposition. A membrane prevents enzyme leaching due to the centrifugal force generated as the electrode rotates. The oxidation of the H2O2, enzymatically generated in the presence of glucose and oxygen, was detected at the optimized potential of 0.7 V vs. Ag wire using a three-electrode configuration. Additional experimental conditions such as electrode material, pH, temperature, and electrode rotation rate were optimized with free and/or bound enzyme. The optimal experimental conditions were: electrode material platinum; pH free enzyme 8.1 and immobilized 7.6; temperature 51º C; and electrode rotation rate 600 rpm. The activation energy was calculated for GOx to be 46.11 kJ mol-1. Also, surface area of the electrode was determined by chronocoulometry of 6 mM ferricyanide. For this immobilization method the detection limit, linear range, signal to noise ratio, and shelf life were established. The specificity of the GOx-modified RDEE was examined by exposing the sensors to molecules structurally similar to β-D-glucose. GOx RDEE was highly specific for β-D-glucose.
A. A. Peverly was financially supported by the Natural Science Summer Student Research program at Benedictine University.
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