Implantable Graphene-based Neural Electrode Interfaces for Electrophysiology and Neurochemistry in In Vivo Hyperacute Stroke Model

Implantable microelectrode arrays have attracted considerable interest due to their high temporal and spatial resolution recording of neuronal activity in tissues. We herein presented an implantable multichannel neural probe with multiple real-time monitoring of neural-chemical and neural-electrical signals by a nonenzymatic neural-chemical interface, which was designed by creating the newly developed reduced graphene oxide-gold oxide (rGO/Au₂O₃) nanocomposite electrode. The modified electrode on the neural probe was prepared by a facile one-step cyclic voltammetry (CV) electrochemical method with simultaneous occurrence of gold oxidation and GOs reduction to induce the intimate attachment by electrostatic interaction using chloride ions (Cl^-). The rGO/Au₂O₃-modified electrode at a low deposition scan rate of 10 mVs^-1 displayed significantly improved electrocatalytic activity due to large active areas and well-dispersive attached rGO sheets. The in vitro amperometric response to H₂O₂ demonstrated a fast response of less than 5 s and a very low detection limit of 0.63 M. In in vivo hyperacute stroke model, the concentration of H₂O₂ was measured as 100.48 ± 4.52 M for rGO/Au₂O₃ electrode within 1 h photothrombotic stroke, which was much higher than that (71.92 M ± 2.52 M) for noncoated electrode via in vitro calibration. Simultaneously, the somatosensory-evoked potentials (SSEPs) test provided reliable and precise validation for detecting functional changes of neuronal activities. This newly developed implantable probe with localized rGO/Au₂O₃ nanocomposite electrode can serve as a rapid and reliable sensing platform for practical H₂O₂ detection in the brain or for other neural-chemical molecules in vivo.