Nanoscale phase separation induced self-reinforced Janus hydrogel achieves robust adhesion under extreme acidity and anti-postoperative adhesions

Adhesive hydrogels have become an ideal alternative to sutures and staples for sealing tissue defects and anchoring devices. However, most existing adhesive hydrogels are designed for two-sided adhesion and suffer from irreversible swelling in the in vivo environment. In this work, we report a nanoscale phase separation induced self-reinforced PABA-EGCG-ALC Janus hydrogel as a sutureless therapeutic solution for gastrointestinal (GI) defect sealing and gastric perforation repair. The Janus hydrogel is prepared by a one-step method and exhibits excellent mechanical compliance, one-sided adhesion behavior, and ROS scavenging ability. Notably, the nanoscale phase separation structures formed by polymer chain entanglements effectively inhibit the swelling behavior of the hydrogel (60.2 % at equilibrium) and induce self-reinforced mechanical strength and interfacial robustness under extreme acidity. After soaking the hydrogel in simulated gastric fluid (SGF, pH 2.0) for 72 h, its tensile stress, elongation at break, toughness, Young's modulus, and burst pressure are increased by 2.9, 1.7, 6.4, 2.4, and 2.1 folds, respectively. Subsequent in vivo animal experiments demonstrate that the PABA-EGCG-ALC Janus hydrogel provides a convenient, fluid-tight, gastric fluid-resistant, robust and suture-free sealing for GI defects and effectively preventing postoperative adhesions while addressing the key limitations of commercially available tissue adhesives and Janus hydrogels.