Analytical Sciences

Abstract − Analytical Sciences, 19(1), 55 (2003).

A Glass Capillary Microelectrode Based on Capillarity and Its Application to the Detection of L-Glutamate Release from Mouse Brain Slices
Kumiko NAKAJIMA, Takashi YAMAGIWA, Ayumi HIRANO, and Masao SUGAWARA 
Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajousui, Setagaya, Tokyo 156-8550, Japan
A new glass capillary microelectrode for L-glutamate is described using pulled glass capillaries (tip size, ~12.5 um) with a very small volume (~2 ul) of inner solution containing glutamate oxidase (GluOx) and ascorbate oxidase. The operation of the electrode is based on capillary action that samples L-glutamate into the inner solution. The enzyme reaction by GluOx generates hydrogen peroxide that is detected at an Os-gel-HRP polymer modified Pt electrode in a three-electrode configuration. The amperometric response behavior of the electrode was characterized in terms of the capillarity, response time, sensitivity and selectivity for measurements of L-glutamate. The currents at 0 V vs. Ag/AgCl increased linearly with the L-glutamate concentration from 10 to 150 uM for in vitro and in situ calibrations. The response was highly selective to L-glutamate over ascorbate, dopamine, serotonin and other amino acids. The detection of L-glutamate in the extracellular fluids of different regions of mouse hippocampal slices under stimulation of KCl was demonstrated.