The use of redox mediator modified glucose oxidase in amperometric enzyme electrodes

Abstract

Abstract Glucose oxidase, modified by the covalent attachment of ferrocenyl groups, has been shown to undergo direct oxidation at clean metal electrodes (Degani & Heller 1987, 1988; Bartlett et al. 1987). Since modified enzymes of this type do not require a freely diffusing mediator and can be oxidized at modest overpotentials they are attractive for application in biosensors and in bioelectronics. The use of ferrocene monocarboxylic acid and ferrocene acetic acid modified glucose oxidase has been studied in membrane enzyme electrodes for glucose. It was found that the lifetime of these devices is limited by the stability of the oxidized form of the ferrocenyl substituent attached to the enzyme. In buffered aqueous solution this is of the order of minutes for the ferrocene monocarboxylic acid modified enzyme and of the order of hours for the ferrocene acetic acid modified material.