ABSTRACT
This chapter focuses on fiberoptic biosensors (FOB) in which a chemical mediation step is not required to link the biochemical reaction with the optical measurement. For enzyme-based sensors the immobilized enzyme catalyzes either the production or consumption of a fluorophore or chromophore and the resulting fluorescence or absorbance is measured through the fiberoptic probe. The general design of an enzyme-based nonmediated FOB includes an enzyme layer immobilized at the distal end of a fiberoptic sensing probe. The analytical performance of the lactate dehydrogenase-based FOB depends on the pH of the sample solution, the concentration of the cosubstrate, and amount of active enzyme immobilized at the sensor tip. Nonmediated anti-body-based FOB has been developed based on light scattering, absorbance, and fluorescence measurements. Nicotinamide adenine dinucleotide accumulates according to the amount of lactate present and the corresponding fluorescence is measured. The concept of the internal enzyme biosensor has been demonstrated with a FOB for ethanol.
