Enzyme-Based Amperometric Biosensors in Flow-Systems for Biomolecule Detection

Abstract: Amperometric enzyme based biosensors were designed, developed and characterised in flow systems. Solid graphite and carbon paste electrodes were used as support for enzyme immobilisation. Both mediated and direct electron transfers between redox enzymes and electrodes were utilised for biosensor construction, as well as coupled enzyme systems. Special emphasis was placed on the optimisation of biosensor characteristics such as detection limit, stability, sensitivity, and selectivity. The effect of various polyelectrolytes on the carbon paste biosensor performance was investigated, resulting in a stabile and sensitive alcohol biosensor. Biosensors were also developed for detection of acetylcholine, carbohydrates, glucose, L-lactic acid, L-glutamate and beta-N-oxalyl-L-alfa, beta-diaminopropionic acid (beta-ODAP). Biosensors were applied as detectors in integrated flow systems for fast and selective detection. A dual biosensor cell, containing one glucose and one L-lactic acid electrode, was integrated with a microdialysis sampling system, which allowed simultaneous detection and on-line monitoring of a fermentation process. Also, an integrated flow system relying on the selectivity of L-glutamate oxidase for the toxic beta-form of ODAP, was utilised together with liquid chromatography and refractive index (RI) detection, enabling quantification of both total ODAP (alfa and beta-form) and beta-ODAP through the combined use of RI and biosensor detection.