Mathematical model of toxicity monitoring sensors incorporating microbial whole cells

A model is presented that describes aspects of the transient and steady-state behaviour of toxicity monitoring biosensors that incorporate living microbial cells immobilized in a thin layer between an amperometric electrode and a porous (non-tortuous) membrane. In the example considered here, respiratory or photosynthetic electron-transport activity is monitored by using artificial redox mediators to divert electrons from the electron-transport systems to the working electrode poised at a suitable reducing potential. Such biosensors are being developed for a range of environmental monitoring applications. The mathematical model is used to demonstrate how the response of practical devices can be manipulated and to indicate potential pitfalls in the interpretation of toxicity assessment data derived by such biosensors.