A Zwitterionic Conductive Hydrogel Interface for Enhanced Electrocorticography Signal Fidelity via High Conductivity, Antifouling, and Brain-Matched Mechanics

Electrocorticography (ECoG) holds considerable promise for neural signal monitoring with high spatiotemporal resolution. However, conventional rigid ECoG electrodes are often hampered by poor mechanical compliance and insufficient resistance to biofouling, leading to high interfacial impedance and compromised signal quality. While integrating conductive hydrogels into ECoG interface offers a potential solution, concurrently achieving high conductivity, mechanical compatibility with brain tissue, biosafety, and robust antifouling remains a significant challenge. This study introduces SPP@NaCl, a novel zwitterionic conductive hydrogel synthesized by doping a poly(sulfobetaine methacrylate) (pSB) hydrogel matrix with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and employing NaCl as a Lewis acid to induce phase separation, thereby promoting an interconnected PEDOT network. The resultant SPP@NaCl hydrogel exhibits a compelling combination of properties: high electrical conductivity (∼9 S·m^-1), a low Young's modulus (1.74 kPa) that closely matches brain tissue, excellent conformability, and markedly reduced protein adsorption attributable to its zwitterionic structure. When integrated with commercial ECoG electrodes, the optimized SPP@NaCl-8 hydrogel dramatically lowers interfacial impedance. The resulting Au-SPP@NaCl electrodes enabled high-fidelity, real-time monitoring of cortical epileptiform discharges in a rat seizure model and demonstrated stable, long-term neural signal acquisition in anesthetized healthy rats. This work presents a new strategy for constructing ECoG interfaces that simultaneously deliver high conductivity, mechanical compliance, biosafety, and antifouling capabilities, highlighting the significant potential of these hydrogel-integrated ECoG electrodes for advanced brain-computer interface applications.