Conductive hydrogel constructs with three-dimensionally connected graphene networks for biomedical applications

• A conductive hydrogel with three-dimensionally connected graphene was fabricated. • TAGAH exhibited high electrical conductivity with a very small amount of graphene. • Fabrication of TAGAH with various shapes can be easily achieved. • TAGAH is useful biomaterial for various biomedical applications. Conductive hydrogels afford efficient electrical communication with biological systems while providing soft and hydrated interfaces. However, facile fabrication of the conductive hydrogels of high electrical properties with minimal incorporation of conductive components is still challenge. We developed a conductive hydrogel composed of three-dimensionally connected reduced graphene oxide (rGO) networks using graphene oxide (GO)-coated agarose microbeads and thermal annealing. Self-assembly of GO-coated agarose microbeads to granulate hydrogels and subsequent mild heating allowed the production of conductive hydrogels (named thermally annealed graphene-channeled agarose hydrogel (TAGAH)) containing a three-dimensionally connected rGO network. TAGAH exhibited high electrical conductivity with a small amount of graphene, low impedance, and soft tissue-like elasticity. Various conductive constructs could be easily fabricated by molding and 3D printing. In vitro and in vivo studies revealed their excellent biocompatibility. Moreover, potential biomedical applications of TAGAH-based materials were successfully demonstrated as soft bioelectrodes, pressure sensors, strain sensors, and conductive tissue scaffolds.