AMPEROMETRIC BIOSENSORS FOR ONLINE MONITORING OF EXTRACELLULAR GLUCOSE AND GLUTAMATE IN THE BRAIN

Two designs of thin film amperometric enzyme biosensor flow cell are d escribed for the on-line measurement of glucose and glutamate concentr ations in the extracellular fluid of the brain in conjunction with a m icrodialysis probe. The biosensors have high sensitivity and speed of response, enabling them to be used in the investigation of short term phenomena. The effects of oxidisable chemical compounds and other inte rferences on the amperometric current are discussed and strategies for eliminating these effects are described. Whereas the interferences ca n be adequately overcome with ease for glucose measurements in the mil limolar range using platinised carbon paper-based enzyme electrodes, t hey are much more serious in the case of glutamate, which is present i n brain extracellular fluid at much lower concentrations. Results are presented to demonstrate the applicability of two types of biosensor m odule for in vivo measurements.