Conductive Hydrogels Embedding Three Dimensionally Connected Graphene Networks for Biomedical Applications

Conductive hydrogels afford efficient electrical communication with biological systems while providing soft and hydrated interfaces, which have garnered great attention for various biomedical applications, such as tissue engineering scaffolds and prosthetics. However, several issues, including high electrical properties with minimal incorporation of conductive components and simple fabrication of various shapes, remain a challenge. In this study, we developed novel conductive hydrogel system composed of three-dimensionally connected reduced graphene networks using graphene-coated agarose microbeads and thermal annealing. Differently charged graphene-coated agarose microbeads self-assembled to form granulate hydrogels, which can be easily handled and processed to produce various shapes of constructs. Subsequent mild heating allowed for the production of the conductive hydrogels (named thermally annealed graphene-channeled agarose hydrogel (TAGAH)) containing a three-dimensionally connected rGO network, which was formed via graphene rearrangement, thermal reduction, and agarose syneresis. TAGAH showed high electrical conductivity (~20 mS cm^-1) with a very small amount of graphene (~1.5 mg mL^-1), substantially low impedance (&gt; 10-fold lower than that of controls), and tissue-like softness (~150 kPa Young’s modulus). Various conductive constructs system could be easily fabricated by molding and 3D printing. <i>In vitro </i>cytocompatibility and <i>in vivo</i> tissue compatibility of these conductive hydrogels were confirmed by cell culture studies and subcutaneous implantation for 8 weeks. Moreover, potential biomedical applications of TAGAH-based materials as soft bioelectrodes, pressure sensors, strain sensors, and conductive tissue scaffolds were successfully demonstrated.