Enzyme Inhibition Assays with an Amperometric Glucose Biosensor Based on a Thiolate Self-Assembled Monolayer

Abstract

A new bioelectrocatalytic enzyme membrane for biosensors based on immobilization of glucose oxidase (GOx) is evaluated for use in inhibition assays. The objectives are to show that the newly developed glucose biosensor has advantages for inhibition assays, not as a specific glucose biosensor as such. The mediator used is 2-aminoethanethiol, which forms a self-assembled monolayer on the surface of a gold electrode. The membrane configuration consists of the thiol as mediator, covalently bound to the gold electrode and at the same time entrapped with GOx in a polyvinylpyridine (PVP) membrane. Cyclic voltammetric scans indicate a catalytic peak at +950 mV (vs. Ag/AgCl) after addition of glucose to a blank phosphate buffer at pH 7.4. The PVP membranes are shown to be reusable for determination of glucose for at least one week. As an example of inhibition of the enzyme reaction, the response to glucose is shown to be sensitive to the addition of Hg(II) in the ppb range with a detection limit of 0.2 ppb. Interference to CV scans from oxidizable organic compounds and other metal ions is found to be minimal, however hydrogen peroxide is the exception and interferes at 1 mM concentration.