Mussel-inspired injectable supramolecular and covalent bond crosslinked hydrogels with rapid self-healing and recovery properties via a facile approach under metal-free conditions.

The design of polydopamine-based injectable hydrogels for biomedical applications with rapid self-healing and recovery properties under metal-free conditions is still a challenge. Here, we developed a facile approach to prepare mussel-inspired and polydopamine crosslinked gelatin hydrogels with fast self-healing ability by simply oxidizing a mixture of gelatin and dopamine under metal-free conditions. These injectable hydrogels autonomously self-healed immediately when coming into contact without any additive under physiological conditions. They exhibited fast recovery after 80% compression, simple reformability, good adhesiveness and biocompatibility. The mechanism of injectable hydrogel formation was also investigated, and demonstrated that the hydrogel network was crosslinked by both supramolecular and covalent bonds endowing the hydrogel with self-healing and recovery properties, and enabling the hydrogel to withstand deformation. This work provides a new and facile approach to prepare polydopamine-based rapid self-healing injectable materials with fast recovery and simple remoldability.