TRANSIENT-RESPONSE OF MULTILAYER ELECTROENZYMATIC BIOSENSORS

A numerical model is used to analyze the transient response of amperometric enzyme sensors. Different biosensor types are considered according to whether the enzyme is fixed on the inner or the outer surface or inside the membrane itself. The numerical simulation is performed with a finite volume method which makes it possible to easily solve the transient mass balance equations in all the juxtaposed layers of the biosensors. Phenomena induced by the transient mass transfers in the different layers are emphasized particularly by analyzing the effects of the stirring strength and the assay protocol on the shape of the current-time curves. This makes it possible to suggest theoretically significant opportunities to improve the reliability and performance of biosensors. The peak current, which appears in some cases when stirring is decreased, offers a measure that is faster and less sensitive to the operating conditions than the steady-state value. After determination of a maximum number of physicochemical parameters by independent experiments, the model satisfactorily fits experimental results performed with free enzyme and immobilized enzyme sensors.