Facile and Rapid Fabrication of a Glutamate Sensor via Electropolymerization of o-Aminophenol

Abstract

Microfluidic analysis enables precise fluid manipulation and high-time-resolution measurements in microscale environments, and has attracted considerable attention as an analytical platform suitable for detecting spatiotemporally fluctuating biomolecules such as neurotransmitters. Glutamate is a major excitatory neurotransmitter in the central nervous system, and its real-time quantification is essential for understanding neural function and pathological mechanisms. In this study, aiming for application to microfluidic analysis, glutamate oxidase was immobilised within an electropolymerized poly(o-aminophenol) film, allowing facile and highly reproducible fabrication of enzyme-modified electrodes. When the response characteristics were evaluated using platinum electrodes of 3 mm and 25 µm in diameter, the microelectrode exhibited a high current density derived from radial diffusion and yielded a steady-state response. The limit of detection and limit of quantification obtained using the 3 mm electrode were 3.22 and 10.7 µM, respectively. Furthermore, the fabricated electrode showed no measurable response toward coexisting substances such as glutamine, aspartic acid, GABA, and glucose, indicating high substrate specificity, and the maximum response was obtained at pH 7.4. These results demonstrate that enzyme immobilisation via electropolymerization is a practical method suitable for integration with microelectrodes and microfluidic devices, and is expected to contribute to in situ glutamate monitoring as well as future applications in clinical diagnostic systems.