An Improved Amperometric Microsensor Microarrays with High Sensitivity and High Selectivity for Ex-Vivo Glutamate Detection

Direct real-time detection of neurochemicals is crucial for a better understanding of their roles in various signaling mechanisms and implications in brain disorders. In this work, a platinum (Pt) microelectrode array (MEA) was modified with glutamate oxidase enzyme and polymer layers to detect glutamate (Glu), a major excitatory neurochemical, with high sensitivity and high selectivity in a complex brain tissue environment. We have developed a comprehensive understanding of key process parameters involved in determining the performance of the enzyme-based glutamate microbiosensor. For e.g. the effect of Pt microelectrode surface cleaning methods, enzyme concentration and loading, meta-polyphenylene diamine (mPD) interferent layer, storage methods and self-referencing techniques were investigated. We report a Glu microbiosensor with high sensitivity (212±4 to 530±34 nA/cm2µM, mean ± SEM), high selectivity towards ascorbic acid, a major interferent (244±5 to 841±54, mean ± SEM) and excellent long-term stability in vitro. The microbiosensor was validated in rat brain slice model in response to an electrical stimulation with varying pulse parameters and detecting Glu in real-time with fast response time (<8 s).