ENZYME - BASED (FIBRE) OPTIC SENSORS

This chapter describes enzyme-based fiber optic sensors. Enzymes are most useful reagents that allow selective sensing of biologically important species, including enzyme substrates, metabolites, inhibitors, activators, and others. The chapter provides an overview of how enzymatic reactions can be monitored by making use of optical chemical sensors. The chapter also describes new types of biosensors in which the intrinsic fluorescence of a co-substrate (NADH) or co-enzyme (FAD) changes as a result of the enzyme/substrate interaction. The FAD-based system has the advantage of accepting oxygen as a second substrate. As a result, it acts fully reversibly in the presence of oxygen. Moreover, its excitation and emission wavelengths are in the visible. These findings have led to new types of optical biosensors in which the holo-enzymes act as both the recognition and transduction elements. Because carbon dioxide is the end product of aerobic metabolism and enzymatic activity always is associated with the existence of life, it became obvious to incorporate a CO 2 sensor into a device for detection of bacterial contamination of blood.