Electrochemical activation of glucose oxidase with a 140-fold enhancement in intramolecular electron transfer rate constant.

In this work, we describe the electrochemical activation of glucose oxidase (GOx) via covalent attachment of a novel redox mediator, Os(bpy)2(API)Cl (bpy = 2,2'-bipyridine, API = 3-aminopropylimidazole), to the peptide backbone of GOx targeting at aspartate and glutamate residues. Cyclic voltammetry showed a pair of well-defined voltammetric peaks centered at 0.11 V for the activated enzyme. Os(bpy)2(API)Cl promotes direct oxidation of FADH2 centers in GOx without the need of any mediating agents in solution. Amperometric tests in glucose solution revealed that the GOx retains its enzymatic activity toward the oxidation of glucose. An intramolecular electron transfer rate constant of 1.0x10(5) s(-1) was obtained for the activated GOx, compared with the rate constant of 7.0x10(2) s(-1) of the natural GOx-oxygen system, making this an amenable system for biosensor applications. Attempts were made in utilizing the activated GOx as an electrochemical tag in nucleic acid assay.