Mathematical simulation of an enzyme-based glucose sensor with pO2-basic sensor.

In the design of enzyme-based sensors, the measuring characteristics are mostly obtained by the trial-and-error method. An alternative is provided by mathematical simulation of the behaviour of the sensors. For this, a mathematical model was outlined which is described by two coubled inhomogeneous partial differential equations for each layer of the sandwich membrane structure and by a set of boundary conditions. This model was used to simulate the dependence of the measuring characteristics (calibration curves, response time) on the design parameters (geometry, transport properties of the membranes, enzyme activity) of the enzyme-based glucose sensor. The simulated and the measured calibration curves are in good correspondence. With decreasing pO2, a stoichiometric limitation appears, and the linear range of measurement is reduced. If catalase is coimmobilized with glucose oxidase, the oxygen consumption is halved and the measuring range is doubled. The influences of diffusion coefficients and of specific enzyme activities on the sensitivity and response time are simulated. The results are in good accordance with theoretical statements and experimental results. The limits of the model are determined by its convergence properties.