An Immunocompatible Conductive Hydrogel Via Anion-π Interlocking as an Injectable Bridge for Sustained Bioelectronic Interfacing.

Advances in implantable bioelectronics have improved the interaction between intelligent systems and biological tissues. Yet, the mechanical-immunological mismatch between rigid electrodes and soft tissues continues to limit long-term device stability. Here, we present SSPH, an immunocompatible, injectable, conductive hydrogel bridge that enables minimally invasive delivery and stable tissue integration. By forming a compliant interfacial bridge, SSPH reduces mechanical-biological mismatch and immune stress on electrodes. It is formed by the spontaneous co-assembly of PEDOT:PSS and the zwitterionic polymer poly(sulfobetaine methacrylate) (PSBMA), resulting in a 3D network stabilized by anion-π interactions, electrostatic interactions, and PEDOT-rich nanostructures. This self-healable architecture allows SSPH to maintain its intrinsic conductive pathways after deformation. Experiments confirmed that SSPH exhibits stable electrochemical properties and favorable immunocompatibility. In an acute muscle injury model, SSPH restored signal transmission across the damaged region, demonstrating its potential to serve as a bridge across disrupted tissue. Furthermore, in both electromyography recording and spinal cord stimulation models, SSPH preserved electrode performance for up to four weeks, supporting reliable bidirectional signal conduction. These results highlight SSPH as a promising, durable, and immunocompatible bridging material for sustained bioelectronic interfaces.