A dynamic and self-crosslinked polysaccharide hydrogel with autonomous self-healing ability.

Natural polymeric hydrogels with self-healing capability that can recover the functionalities and structures of gels after damage are extremely attractive due to their emerging applications in the biomedical field. Here we report a self-healable polymeric hydrogel by self-crosslinking two natural polymers acrylamide-modified chitin (AMC) containing amino groups and oxidized alginate containing dialdehyde groups. The generation of the self-crosslinked hydrogel relies on the dynamic covalent linkage through Schiff base between the polysaccharide chains. The self-healing capability of the crosslinked hydrogel depends on the molar ratio of AMC and oxidized alginate and the surrounding pH. Under certain circumstances, the damaged hydrogel shows a complete recovery and can be stretched to a favorable extent, which is seldom observed for polysaccharide self-healing hydrogel. Notably, we find that the self-healing ability can be "stored" by freeze-drying and "activated" by rehydration. In addition, we demonstrate that the hydrogel can be used as a soft template to guide the repair of inorganic materials like hydroxyapatite. We anticipate that this self-healable hydrogel consisting of biocompatible and biodegradable polysaccharides can be applied to various biomedical fields.