A high-sensitive nano-modified biosensor for dynamic monitoring of glutamate and neural spike covariation from rat cortex to hippocampal sub-regions.

BACKGROUND: Hippocampus is a critical part of brain tissue involved in many cognitive neural activities. They are controlled by various neurotransmitters such as glutamate (Glu), and affected by electrophysiology.

NEW METHOD: Herein, we fabricated a 16-site (25μm in diameter) microelectrode array (MEA) biosensor applied in dual-mode tests including Glu and neural spike measurements.

METHODS: All the 16 recording sites were electrodeposited with platinum nanoparticles (PtNPs) and 8 sites were used for electrical recording. Glutamate oxidase enzyme (Gluox) and 1,3-Phenylenediamine (mPD) layer were specially modified on the other 8 sites for Glu recording. The dual-mode MEA was implanted from cortex to hippocampus of anesthetized rat to record Glu content and firing rate.

RESULTS: The electrical sites showed much lower impedance. The Glu sites showed much higher sensitivity(7.807 pA/μM), and ideal selectivity to the major molecules in brain. The post calibration sensitivity (3.935 pA/μM) maintained on a positive level. Different Glu content peaks including cortex (18.32μM) and hippocampal CA1 (4.39μM), CA3 (10.16μM), dentate gyrus (DG, two layers: 5.36μM and 10.34μM) have detected. The corresponded firing rate was recorded, too.

COMPARISON WITH EXISTING METHODS: This modification showed much lower impedance and much higher sensitivity. We obtained more neuron activities simultaneously by dual-mode recording. The covariation of Glu and neural spike signals was discovered in the specific hippocampus sub-region.

CONCLUSIONS: The covariation between Glu and firing rate changes were synchronous, and effected by regions. The dual-mode signals were useful to find the neurology disease mechanism.