Impact of Oxygen on Glucose Oxidation Kinetics in a Redox Polymer Mediated Glucose Oxidase Electrode

Abstract

The kinetics of glucose oxidation by glucose oxidase (GOx) were evaluated with mediation by two different osmium redox polymers and in the presence and absence of oxygen (O2). A one-dimensional model was designed to account for the presence of dissolved oxygen, which competes with the mediator for adsorption sites on GOx and electrons from glucose oxidation. Kinetic parameters were determined by fitting the experimental current density measurements for varying potential, glucose and O2 concentrations, accounting for competitive inhibition and competitive reaction. It was demonstrated that the presence of O2 does not change the turnover number, kcat, of the enzyme, indicative of a competitive inhibition mechanism. However, improved fitting of the model was observed when considered the competitive reaction of O2. Kinetic parameters specific to the mediator reaction were an order of magnitude higher than other homogeneous mediated systems, leading to high mediation efficiency. Bimolecular rate constants for the GOx-oxygen reaction were found to be an order of magnitude lower than that of the free solution, which can be attributed to the reduced activity of immobilized GOx.