Self referencing ceramic based multisite microelectrodes for the detectionand elimination of interferences from the measurement of L-glutamate and other analytes

A self-referencing technique utilizing two microelectrodes on a ceramic-bas ed multisite array is employed for confirmation and elimination of interfer ences detected by enzyme-based microelectrodes. The measurement of L-glutam ate using glutamate oxidase was the test system; however, other oxidase enz ymes such as glucose oxidase can be employed. One recording site was coated with Nafion with L-glutamate oxidase and bovine serum albumin (BSA) cross- linked with glutaraldehyde while the other had Nafion with BSA cross-linked with glutaraldehyde. Differences in the chemistry of the two recording sit es allowed for identification and elimination of interfering signals to be removed from the analyte response. The electrode showed low detection limit s (LOD = 0.98 +/- 0.09 muM, signal-to-noise ratio of 3), fast response tith es (T-90 similar to1 s), and excellent linearity (R-2 = 0.999 +/- 0.000) ov er the concentration range of 0-200 muM for calibrations of L-glutamate in vitro. The selectivity and dimensions of the multisite electrode allow in v ivo glutamate measurements. This electrode has been applied to in vivo meas urements of the clearance of locally applied glutamate and release of gluta mate in the prefrontal cortex of anesthetized rats. In addition, a similar approach has been applied to the development of a microelectrode for measur es of glucose.