Robust Janus Hydrogel with Wet-Tissue Adhesive Properties for Wound Dressing and Anti-Postoperative Adhesion.

Although adhesive hydrogels have advanced rapidly in recent years, conventional double-sided adhesives still face challenges in achieving effective adhesion to wet tissues and preventing postoperative tissue adhesion. In this study, a novel Janus hydrogel wet adhesive was successfully designed by precisely regulating the distribution of free hydroxyl and phenolic hydroxyl groups on the two surfaces of the hydrogel. The resulting Janus hydrogel exhibits significantly different adhesive and nonadhesive properties on its upper and lower surfaces. Specifically, through a simple boric acid (BA) solution immersion process, BA cross-linked with poly(vinyl alcohol) (PVA) and tannic acid (TA), effectively suppressing the exposure of hydroxyl groups on the upper surface, leading to low adhesion. In contrast, the lower surface retains strong adhesion to various wet tissues, even underwater. Adhesion simulations with pig skin validated the robust adhesion of the hydrogel's bottom surface to wet tissues, while the low-adhesion upper surface effectively prevented tissue adhesion. Furthermore, cytocompatibility, hemolysis, and coagulation tests demonstrated that the PVA/TA/BA hydrogel possesses excellent biocompatibility and notable hemostatic properties. This simple and efficient preparation strategy offers a practical approach for developing novel Janus hydrogels, laying a solid theoretical and practical foundation for their application in wet tissue repair and postoperative antiadhesion treatments.