Nonlinear effects of partitioning and diffusion-limiting phenomena on the response and sensitivity of three-layer amperometric biosensors

Abstract

The influence of the partitioning and diffusion limitations on the response of amperometric biosensors is investigated analytically and computationally using a three-compartment model: an enzyme layer, a diffusion limiting membrane and an outer diffusion layer. The biosensors are modelled by a system of reaction–diffusion equations involving a nonlinear term related to Michaelis–Menten kinetics. Exact steady state analytical solutions for the substrate and reaction product concentrations and the output current are presented for specific cases of first and zero-order reaction rates. The performance of the biosensor is numerically investigated at the transition conditions. Application of different specific types of the interface conditions, perfect contact and partition conditions, at which the steady state biosensor response is the same for both types of the interface conditions is analysed. The effective diffusion coefficients merging two diffusion layers are defined for reducing the three-compartment to the corresponding two-compartment model. The nonlinear and non-monotonic behaviour of the biosensor response is discussed.