Tannic acid post-treatment of enzymatically crosslinked chitosan-alginate hydrogels for biomedical applications

Enzyme-mediated crosslinked hydrogels as soft materials for biomedical applications have gained considerable attention. In this article, we studied the effect of tannic acid post-treatment on adhesiveness and physiochemical properties of an enzymatically crosslinked hydrogel based on chitosan and alginate. The hydrogels were soaked in TA solution at different pH (3, 5.5, 7.4, and 9) and concentrations (1, 10, 20, 30 TA wt%). Increasing the TA concentration to 30 TA wt% and pH (up to 7.4) increased the TA loading and TA release. TA post-treatment reduced the swelling ratio and degradation rate of the hydrogels due to the formation of hydrogen bonding between TA molecules, chitosan, and alginate chains resulted in higher crosslinking density. TA-reinforced hydrogels with 30 % TA (Gel-TA 30) exhibited significantly high adhesive strength (up to 18 kPa), storage modulus (40 kPa), and antioxidant activity (>96 %), antibacterial activity, and proliferation and viability of 3 T3-L1 fibroblast cells.