DEVELOPMENT OF BIOSENSORS USING OPTICAL FIBERS

Abstract

Fiber optic biosensing probes consist of an immobilized biocatalytic layer at the distil tip of an optical fiber device. In the presence of the bioanalyte, the biocatalyst generates an optical signal which is measured and related to the bioanalyte concentration. Three new classes of fiber optic biosensors are presented. The first class is based on the immobilization of a deaminating enzyme at the tip of an fiber optic ammonia sensor. The first fiber optic urea sensor has been successfully demonstrated by immobilizing urease at the tip of an optimized fiber optic ammonia sensor. The second type of fiber optic biosensor is based on the immobilization of a dehydrogenase enzyme and the fluorometric detection of reduced nicotinamide adenine dinucleotide (NADH) at the distil tip of an optical fiber bundle. The feasibility of this NADH-based biosensor strategy has been successfully demonstrated with biosensors for lactate and pyruvate. Finally, a novel biosensor arrangement is introduced where the biocatalyst is separated from the sample solution by a gas-permeable membrane. This "internal enzyme" approach has been demonstrated with an ethanol sensor in which alcohol dehydrogenase is employed as the enzyme and the production of NADH is detected fluorometrically. Relative merits and future prospects for these three types of fiber optic biosensors are discussed.