Thiolated Silk and Chitosan Blended Hydrogels

Self-healing hydrogels have numerous biomedical applications such as wound healing, drug delivery, and tissue engineering. Thiol-silk hydrogels have been previously investigated due to the stability, durability, and high mechanical strength of silk. However, silk hydrogel scaffolding is brittle and limited in function in a 3D cell culture environment. Chitosan is a polysaccharide derived from chitin found in insect, shellfish, and crustacean exoskeletons. Chitosan has high antibacterial properties and hemostatic potential, but poor mechanical strength and low solubility at neutral pH. Blending chitosan with silk hydrogels is anticipated to improve the flexibility and mechanical properties over silk alone. The Murphy group previously developed a procedure for creating thiol-modified silk to form a hydrogel via disulfide crosslinking. Here, this strategy was adapted for chitosan, which should allow uniform crosslinking to occur between thiol-silk and thiol-chitosan. The addition of thiols to the polymers was monitored with 1H NMR spectroscopy. Other characterization techniques used were UV-Vis spectroscopy and rheology, which verified that the reaction occurred as expected and compared the properties of the combined hydrogels to the plain thiol silk or thiol chitosan gels. This work aims to produce a reproducible protocol that combines thiol-silk and thiol-chitosan into a more mechanically robust self-healing hydrogel than a gel comprised of either polymer alone.