Synthesis and characterization of in situ cross-linked hydrogel based on self-assembly of thiol-modified chitosan with PEG diacrylate using Michael type addition

A novel injectable in situ cross-linked hydrogel has been designed via Michael type addition between thiol-modified chitosan (CS-NAC) and PEG diacrylate (PEGDA). Hydrogel was rapidly formed in situ under physiological conditions. The gelation time depended on the content of free thiols in CS-NAC, temperature, and concentration of CS-NAC and PEGDA. Thermogravimetric analysis showed the thermal stabilities of hydrogels. SEM observation results confirmed a porous 3D structure. Rheological studies showed that the cross-linking density and elasticity of hydrogel had a correlation to the content of CS-NAC and PEGDA. Swelling studies revealed that these hydrogels had a high initial swelling and were degradable under physiological conditions. And swelling was highly temperature-dependent and was directly related to the amount of cross-linking. Biological activities of the hydrogels were evaluated by in vitro cell compatibility on HDFs and A549 cells and the results indicated that the hydrogel was biocompatible.