Numerical modelling of chemically modified enzyme electrodes

Abstract

In this paper the response of an amperometric biosensor based on a chemically modified electrode is modelled numerically. The model is based on a system of non-linear reaction-diffusion equations. The modelling biosensor comprises two compartments: an enzyme layer and an outer diffusion layer. In order to increase the efficiency of the numerical simulation the quasi-steady state approximation (QSSA) of the full model is investigated. The accuracy of the biosensor response simulated under quasi-steady state conditions is evaluated by the response simulated with the corresponding full model. In order to define the main governing parameters the corresponding dimensionless mathematical model was derived. The digital simulation was carried out using the finite difference technique. By changing model parameters the output results are numerically analysed at transition, quasi-steady state and steady state conditions. Calculations showed that the QSSA can be applied to the full model practically without losing the accuracy of the biosensor response prediction only if the biosensor acts under the limitation of the enzyme-mediator interaction as well as at relatively low mediator concentrations.