ABSTRACT
This chapter presents the broader definition of biosensors that is used by which the device is a chemically responsive transducer directly in contact with a biological matrix or surface but does not itself necessarily incorporate a biological component. Microelectrodes with a tip diameter up to 200 µm have been developed for fundamental biological investigations. The ready electrochemical oxidation of endogenous, organic, and pharmaceutical agents at polarizing voltages well below those capable of decomposing water can in principle be used for their in vivo monitoring. The devices are insufficiently robust for clinical application but have been used extensively for dynamic intracellular ion monitoring and also extracellular measurement in some cases. Peritoneally implanted electrodes may prove acceptable for in vivo monitoring in the glucose clamp experiments have shown long equilibration times with respect to blood; thus in vivo calibration here may not be feasible.
