Sol–gel‐derived amperometric glucose biosensor based on covalent attachment of toluidine blue O to carrier

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Abstract
An amperometric‐mediated glucose biosensor has been fabricated by immobilizing glucose oxidase (GOx) and mediator toluidine blue O (TBO) to a functional sol–gel thin layer on the surface of a platinum electrode via the cross‐linking agent glutaraldehyde. The functional sol–gel thin layer was synthesized through the hydrolysis and polycondensation of γ‐aminopropylmethyldimethoxysilane (APMDMOS) and tetramethoxysilicane (TMOS). GOx and TBO were covalently attached to carrier sol–gel material based on the interaction between the aldehyde group of glutaraldehyde and the amino group of GOx, TBO and carrier. Covalent immobilization eliminates leakage of the sensing reagent and mediator from the carrier. Cyclic voltammetry was employed to demonstrate the feasibility of electron transfer between the active site of sol–gel‐immobilized GOx and the surface of a platinum electrode. The calibration curve of glucose was linear in the range from 1 to 8 mmol/l, with a detection limit of 5 × 10−2 mmol/l. The lifetime of the biosensor was 30 days. Copyright © 2003 John Wiley & Sons, Ltd.