Glutamate biosensing probes based on fiber optic technology will be developed. These probes consist of the enzyme glutamate dehydrogenase immobilized at the distill tip of an optical fiber. This enzyme catalyzes the reaction between glutamate and oxidized nicotinamide adenine dinucleotide to form 2-oxoglutarate, ammonia and reduced nicotinamide adenine dinucleotide (NADH). The generation of NADH is monitored by either a fluorescence or bioluminescence process. In both cases, a steady-state signal is produced which can be related to the sample concentration of glutamate. If successful, the proposed glutamate biosensors will be suitable for in vivo studies to determine the neurological properties of glutamate. These sensors will allow localized, intratissue measurements of glutamate (and possibly aspartate) in intact neuoral tissue. Such localized measurements can potentially separate synaptic from non-synaptic pools of these putative neurotransmitters. In addition, a reagent-less glutamate probe will also be investigate as a means to make continuous, in vivo glutamate measurements.
