SIGNAL GENERATION AND EVALUATION IN FLUORESCENCE-BASED ON-LINE FIBER OPTIC BIOSENSORS

Abstract

The signal generation, size and transmission of pre-steady-state and steady-state signals in fluorescence based fiber optic biosensors for on-line use and their applicability in several flow sensor configurations are investigated. In contrast to the theory, the signal for dynamic column biosensorswith larger particles was foundto be onlyslightly higher than for a column sensorwith smaller particles. This is due to interparticle interactions, which reduce the areathat is accessible for mass transfer, on particles with a diameter below 100 pm. Additionally this system has shown that dynamic biosensors with hydrolases can not be used for the determination of the end-pointof hydrolytic processes, when the equilibrium of the substrate conversion remains below 100%. The flow of optical power in fluorescent fiber optic sensors is analyzed, multiplicative noise is identified as the dominantlimitation of sensor performance. Evanescent coupling is a promising concept for fast biosensors. The observed nonlinear relation between absorbance and concentration is explained as an optical effect, caused by multimode operation. The use of special fibers with increased surface area gives higher sensitivity, reduced nonlinearity.