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

A self-referencing technique utilizing two microelectrodes on a ceramic-based multisite array is employed for confirmation and elimination of interferences detected by enzyme-based microelectrodes. The measurement of L-glutamate using glutamate oxidase was the test System; however, other oxidase enzymes 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 sites allowed for identification and elimination of interfering signals to be removed from the analyte response. The electrode showed low detection limits (LOD = 0.98 ± 0.09 μM, signal-to-noise ratio of 3), fast response times (T₉₀ ∼1 s), and excellent linearity (R² = 0.999 ± 0.000) over the concentration range of 0-200 μM for calibrations of L-glutamate in vitro. The selectivity and dimensions of the multisite electrode allow in vivo glutamate measurements. This electrode has been applied-to in vivo measurements of the clearance of locally applied glutamate and release of glutamate in the prefrontal cortex of anesthetized rats. In addition, a similar approach has been applied to the development of a microelectrode for measures of glucose.