Chapter 15
Mathematical Modeling of Mediated Amperometric Enzyme Sensors
A general discussion of enzyme sensor modeling has been presented in Chapter 04 where it has been assumed that the sensor response is proportional to the product concentration at the transducer surface. This condition can be fulfilled in the case of certain first-generation amperometric enzyme sensors. However, the mechanism of mediated amperometric enzyme sensors clearly deviates from the above assumption as the mediator is involved in a series of processes such as diffusion, reaction with the enzyme and the electrochemical reaction. That is why modeling of mediated amperometric enzyme sensors is a distinct problem, which is comprehensively reviewed in the literature [1–4].
This chapter introduces the principles of amperometric enzyme sensor modeling in two limiting cases depending on the location of the diffusion layer, namely the external diffusion and the internal diffusion cases.
In the external diffusion case, substrate diffusion is localized out of the sensing layer, within a membrane or within the diffusion layer formed in the solution when the solution is in direct contact with the enzyme layer. No diffusion processes occur within the enzyme layer.
The internal diffusion case is characterized by the fact that the enzyme reaction produces concentration gradients within the enzyme layer. Hence, diffusion occurs in parallel with the enzymatic reaction. This model assumes that no concentration gradients ...
