An anti-swelling and toughening underwater adhesive hydrogel for wound healing

Hydrogel adhesives have the advantages of simple operation, non-invasive wound closure, prevention of fluid leakage, and promotion of tissue repair. However, existing hydrogel adhesives still encounter challenges such as insufficient adhesion at wet interfaces, high swelling rates, weak mechanical properties, and lack of specific adhesion, which significantly limit their clinical applications. To address these issues, a double-network (DN) hydrogel (PTCT) composed of polyacrylic polyacrylamide (PP), oxidized cellulose nanofibrils (TOCNFs), chitosan (CS), and tannic acid (TA) was prepared via a straightforward method. PP constituted the basic skeleton of the composite hydrogel, and the second network of hydrogel was crosslinked by using the dynamic reversible non-covalent bond, including electrostatic interaction and hydrogen bonds among PP, TOCNF, CS and TA. The hydrogel exhibited 4300% stretchability, 80% compressive resilience, and a low swelling rate of only 0.56. Notably, the hydrogel showed underwater adhesion only to biological tissues, and the wet adhesion strength reached up to 37.5 kPa. Moreover, the composite hydrogels exhibit antioxidant capacity, coagulation ability and sustained long-acting antibacterial properties.