Enzyme-Modified Microelectrodes for Measurement of Glutamate: Characterization and Applications

Glutamate is a critical neurotransmitter in the central nervous system that plays a key role in numerous physiological processes and neurological disorders. Traditional methods of glutamate detection have low spatiotemporal resolution, while electrochemical methods are limited due to glutamate not being readily redox active at unmodified carbon electrode surfaces. This study presents the development of a glutamate oxidase-modified microelectrode for the sensitive, real-time detection of glutamate using fast-scan cyclic voltammetry (FSCV) with a triangle waveform. Here, we employed a chitosan-hydrogel coating to immobilize glutamate oxidase onto carbon-fiber microelectrodes, enabling selective metabolism of glutamate to hydrogen peroxide. The metabolism to hydrogen peroxide facilitates indirect detection with high sensitivity across a concentration range relevant to physiological concentrations. We utilized FSCV for detection, which enhanced temporal resolution and chemical selectivity, allowing for the codetection of glutamate with other neurotransmitters such as dopamine and norepinephrine. We performed proof-of-concept validation and testing utilizing both biological fluids and complex food samples, demonstrating the enzyme-modified microelectrode's broad applicability in clinical diagnostics and food quality assessment. The sensor showed excellent stability, resistance to fouling, and retained over 90% of its initial response after multiple uses. This work highlights the potential of this biosensor as a versatile tool for minimally invasive, biocompatible, rapid, and accurate glutamate measurement in a wide variety of samples for a diverse set of applications.