Injectable chitin hydrogels with self-healing property and biodegradability as stem cell carriers

To meet the demands of various therapeutic tasks, injectable hydrogels with tunable mechanical properties and degradability are highly desired. Herein, we developed an injectable chitin hydrogel system with well-manipulated mechanical properties and degradability through dynamic acylhydrazone crosslinking catalyzed by 4-amino-DL-phenylalanine (Phe-NH₂). The mechanical properties and degradability of the hydrogels could be easily adjusted by varying the solid content, while their gelation time could be maintained at a constant level (∼130 s) by altering Phe-NH₂ content, thereby ensuring the good injectability of hydrogels. Moreover, the chitin hydrogels showed excellent self-healing capacity with a healing efficiency up to 95 %. Owing to their superior biocompatibility and biodegradability, the chitin hydrogels could support the proliferation and multi-potent differentiations of rat bone marrow-derived stem cells, serving as a beneficial 3D scaffold for stem cell encapsulation and delivery. This work provides a promising injectable delivery vehicle of therapeutic drugs or cells for tissue regenerative medicine.