Enzymatic electrocatalysis in a micellar environment: Glucose oxidase catalysis mediated by ferrocene solubilized by addition of n-octyl-beta-D-glucoside

In the presence of the neutral n-octylglucoside surfactant the reduced form P of the ferrocene mediator is solubilized by micellization in aqueous solution. Then it can be used in the mediation of the electrochemically driven oxidation of glucose catalyzed by glucose oxidase. The validity of the assumption that P is the only micellized species is ascertained by the analysis of the experimental results. The micellization of the water-soluble ferrocenium Q can be neglected. The apparent diffusion coefficient D-P of ferrocene can be controlled by the micelle concentration while the diffusion coefficient D-Q of ferrocenium is only affected by the accompanying changes in the viscosity of the medium. Accordingly, the kinetics of the enzymatic electrocatalysis, investigated by means of cyclic voltammetry, depends on D-P and the ratio delta = D-P/D-Q. A thorough quantitative analysis of the observed behavior enabled us to carry out the complete kinetic characterization of the process and to show that all the rate constants involved in the enzyme kinetics are unaffected by the presence of the surfactant.