Preparation of carboxymethylchitosan based rapid self-healing injectable hydrogels

Carboxymethylchitosan (CMCS) was prepared in a strong alkaline mixture system of isopropyl alcohol and water, and the substitution degrees of carboxymethylation on -OH and -NH2 groups of chitosan were 58% and 5%, respectively. A series of hydrogels were obtained by mixing 1 wt%-5 wt% aqueous solution of CMCS with aldehyde-4-arm polyethylene glycol (4r-PEG-CHO) and ZnCl2 at room temperature at pH=6. The presence of a chemical and physical cross linker in the same time, 4r-PEG-CHO and ZnCl2, enhanced the mechanical properties of hydrogels and the storage modulus of the gels reached up to 1562 Pa. This may be due to a synergistic effect of imine bonds, metal coordination and hydrogen bonding. The hydrogels exhibited good injectability, pH sensitivity and rapid self-healing ability. Macroscopic observation and dynamic rheological results showed that the hydrogels could self-heal within 1 min after being damaged. This novel rapid self-healing injectable hydrogel has potential applications in the field of biomedicine.