Development of brain glutamate microbiosensor using platinum (Pt) electrode and application of in vivo / Siti Kartika Hamdan

Monitoring of extracellular brain glutamate (Glu) level by microbiosensor is a promising approach for further investigation of the important role of neurotransmitter. The neurotransmitter glutamate has shown in development of brain function including cognition, memory and learning process. Glutamate microbiosensor should serve high sensitivity which able to response for low concentration, high selectivity from interferences, fast and accurate result. Surface teflon encapsulated platinum (Pt) electrode disk design of internal size diameter 50 µm, electropolymerized with poly-o-phenylenediamine (PPD), layered with nafion (Naf), immobilized with glutamate oxidase (GluOx) and cross-linked glutaraldehyde (GA) (Pt50/PPD/Naf/GluOx/GA) has chosen in glutamate detection and performed promising glutamate biosensor using constant potential amperometry (CPA) where Michaelis-Menten for glutamate response, Jmax = 120 µAcm-2, KM= 60 µM and limit of detection (LOD) is 2.5 µM ± 0.5 µM were obtained. The response time was ~9s which is three times faster as compared to Pt50/PPD/GluOx/Ga. The developed glutamate microbiosensor have established an excellent in rejection against ascorbic acid (AA) and other interferences. This electrode designed configuration shows good sensitivity in neutral pH range at pH 7.5. The stability of the electrode was stable until 3 days and kept in cold temperature at 4oC. The reduced enzyme activity on the electrode was due to dissolution of the enzymatic membrane during storage and causing the sensitivity of electrode less stable along the period. In vivo studied shows that data sampling rate of electrode without enzyme (Pt50/PPD/Naf) and with enzyme (Pt50/PPD/Naf/GluOx/GA) were 0.0022 µA and 0.0039 µA, respectively. The ability of glutamate microbiosensor in monitoring the presence of glutamate in the prefrontal cortex of anaesthetized rats was proven.