Theory of Catalytic Current at the Biocatalyst Electrode with Entrapped Mediator

Abstract

A mathematical model of a biocatalyst electrode with entrapped mediator is presented. Differential equations describing the diffusion of the substrate and mediator coupled with the enzyme reaction in the immobilized enzyme layer adjacent to the electrode surface are numerically solved to simulate the dependence of the steady-state current, I, on the concentration of the substrate at the surface of the enzyme layer, ¹c_s, and on the concentration of the mediator entrapped in the enzyme layer, C_M. The numerical solutions are expressed by Michaelis-Menten type equations with three parameters which characterize the I vs. ¹c_s and I vs. C_M curves. The diffusional resistance of a semipermeable membrane covering the enzyme layer on the electrode surface is also taken into consideration. The dependence of the current on the potential applied to the electrode, E, is also derived and the parameters characterizing the I vs. E curve are discussed.