Engineered Injectable Coaxial Supramolecular Hydrogel for a Minimally Invasive Neural Electrode

Implantable neural electrodes with long-term stability remain a central challenge for brain-computer interfaces due to the severe mechanical mismatch between rigid electrodes and soft neural tissue, which triggers chronic inflammation and signal degradation. Herein, we report an injectable coaxial supramolecular hydrogel electrode based on dynamic host-guest interactions between β-cyclodextrin and adamantane, combined with silver nanowire incorporation for enhanced electrical conductivity. The resulting hydrogel exhibits shear-thinning and rapid self-recovery behavior, enabling minimally invasive injection and in situ formation of soft, cylindrical neural electrodes without auxiliary insertion devices. By tuning the supramolecular crosslinker density, the hydrogel achieves tissue-matched mechanical properties comparable to those of brain tissue, effectively mitigating a mechanical mismatch at the electrode-tissue interface. The incorporation of silver nanowires establishes a percolated conductive network, leading to low impedance and stable electrochemical performance. In vivo implantation demonstrates stable impedance and reliable neural signal recording over 14 days. Furthermore, the hydrogel electrodes successfully capture stimulus-evoked neural responses and pathological epileptic activity in a rat model. This work provides a versatile strategy for constructing injectable, mechanically compliant, and electrically robust neural electrodes, offering opportunities for next-generation soft neural interfaces.