Optimizing the ratio of horseradish peroxidase and glucose oxidase on a bienzyme electrode: Comparison of a theoretical and experimental approach

This study compares the behaviour of an electrochemical enzyme biosensor with a theoretical analysis based on a mathematical model and numerical simulation. The biosensor is based on a bienzyme channelling configuration, employing the enzymes glucose oxidase and horseradish peroxidase, with direct electron transfer of horseradish peroxidase at a conducting polymer electrode. This was modelled by a system of partial differential equations and boundary conditions representing convective and diffusive transport of the substrates glucose and hydrogen peroxide, as well as reaction kinetics of the bienzyme electrode. The main parameter investigated was the ratio of the two immobilised enzymes, with the aim of maximising the amperometric signal amplitude. Experimentally, it was found that the optimum ratio of enzymes on the electrode was 1:1. A theoretical model consistent with this outcome suggests that the kinetic rates of horseradish peroxidase were greatly reduced in this configuration.