THE USE OF FLUORESCENCE SENSORSAS OPTICAL BIOSENSORS

Abstract

The use of miniaturized fluorescence probes for on-line monitoring analytes in continuous- flow systems (automated clinical analysis, process control, e.g. in biotechnological processes, environmental control, etc.) has becomeincreasingly important. Wereport the application of a fiber-optic based fluorescence probe used as optrode for a novel optical biosensor system to monitor NAD(H) dependent enzymatic reactions based on the flow-injection analysis (FIA) principle. A miniaturized fiber-optic fluorimeter is combined with a small size membrane reactor (1 ml) (Fig. 1). In here, enzymes (dehydrogenases) for analyte conversion and coenzymeregeneration as well as the macromolecular coenzyme derivative polyethyleneglycol (PEG, M, = 20,000)-N°-(2-aminoethyl)-NAD(H) [1] are retained in the direct vicinity of the sensor tip of a concentric fiber-optic probe (fluorescence excitation 360 nm / emission 460 nm) by an ultrafiltration membrane (cutoff: 5000 Dalton) (Fig. 2). Only low molecular-weight compounds (analytes, products, etc.) can freely pass through thisultrafiltration membrane.