A Janus hydrogel sealant with instant wet adhesion and anti-swelling behavior for gastric perforation repair

Achieving instant adhesion on wet tissues and preventing the concurrently occurred postoperative tissue adhesion remain tough challenges but urgently demanded. And the deteriorated cohesion and adhesion caused by undesired swelling of hydrogel could not be ignored. Herein, we developed a Janus hydrogel with instant wet adhesion and anti-swelling behavior, based on poly (acrylic acid) (PAA), gelatin (GT) and hyperbranched polymers modified with catechol (HBPC). The asymmetric structure is achieved through complexed one-side of the hydrogel with cationic polymers. The strong physical interaction between PAA and GT formed during immersing in water enhanced the mechanical strength of the gels. And the hydrogel exhibits good anti-swelling behavior, which circumvents the limitations of conventional hydrogel caused by swelling. Water drainage induced by hydrophobic component and the following removal of water residuals achieved by hydrophilic PAA synergistically enhanced the instant wet adhesion of the hydrogel. Besides, pH-responsive protonation of carboxyl groups in PAA equipped the adhesive with extreme acid-tolerance. The in vivo evaluation results demonstrated that the asymmetric adhesive hydrogel could promote the repair of gastric perforation while reducing the risk of postoperative tissue adhesion. The hydrogel with asymmetric wet adhesion might provide valuable insights into the establishment of bioadhesives for gastric sealing and repair.