Enzyme Electrodes with Glucose Oxidase Immobilized on Stöber Glass Beads

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Abstract
In this study we report the development and experimental evaluation of a miniature Stöber glass-coated enzyme electrode for glucose biosensor applications. The enzyme - glucose oxidase - is chemically immobilized onto the surface of the Stöber glass beads after a silanization procedure. The sensors were fabricated using glass beads of different radii ranging from 20 nm to 100 nm. The overall thickness of the glass coating was about 1.4 μm in all cases. Initial calibration curves of the electrodes show an increase in the response value with decrease in the bead radius. Life-time evaluation tests, however, demonstrate a different behavior of the electrodes. At the end of a 50 day test, the electrode with bead radius of 70 nm remained most stable. The response of this electrode was stable over this period of time and no apparent decrease in its sensitivity was observed. This study suggests that there may be a relation between the immobilized enzyme stability and the porosity of the glass-bead layer. Preliminary tests in undiluted blood plasma suggest that electrodes can be used for glucose measurements in body fluids.