A microelectrode biosensor for real time monitoring of l-glutamate release

We have developed an amperometric microbiosensor for real time monitoring l-glutamate release in neural tissue, based on enzymatic oxidation catalyzed by the l-glutamate oxidase. By means of a sol–gel coating method, l-glutamate oxidase was entrapped in a biocompatible gel layer that provided a benign environment and retained enzyme activity on the surface of Pt microelectrode. Prior to gel layer formation, a modification on the surface of Pt microelectrode with poly(phenylene diamine) enabled the microbiosensor screen majority of common potential interfering substances existing in physiological samples. The miniaturized biosensor achieved a steady state response to l-glutamate within 10 s and exhibited a linear dependence on the concentration of l-glutamate from 0.5 to 100 μmol L−1 with a high sensitivity of 279.4 ± 2.0 μA (mmol L−1)−1 cm−2 (n = 4, R.S.D. = 2.8%). The microbiosensor also exhibited excellent long-term stability in dry storage. We have successfully used the microbiosensor for real time measuring of l-glutamate in vivo.