Amperometric Biosensors Based on a Biocatalyst Electrode with Entrapped Mediator

Abstract

A mathematical model of a biocatalyst electrode with entrapped mediator is presented. The electrode is a benzoquinone (BQ)-mixed carbon paste electrode (CPE), on which glucose oxidase (GOD) is immobilized by coating with a polymer film or semipermeable membrane (s.m, a film-coated GOD-BQ-CPE). BQ is dissolved in the immobilized-enzyme layer(e.l.) to mediate the electron transfer between the electrode and the enzyme. The model is focused on the diffusion accompanied with enzyme reaction of substrate (D-glucose) and mediators (BQ and its reduced form) in the e.l. and the diffusion in the sm. The amperometric response of the electrode is analyzed as a function of transport, kinetic, and geometrical parameters and compared with experimental results. A glucose sensor based on a film-coated GOD-BQ-CPE has a wide concentration range of response and is not affected by oxygen in test solution. Biosensors for D-gluconate and ethanol based on film-coated gluconate dehydrogenase-BQ- and alcohol dehydrogenase-NAD-CPE′s, respectively, are presented.