Convenient Synthesis of an On-Demand Tissue Adhesive Based on a Thermoresponsive Hydrogel Aided by a Multifunctional Hyperbranched Polymeric Crosslinker

Tissue adhesives are increasingly utilized for wound closure in various clinical settings that could either replace or augment more traditional options, such as sutures and patches. Biocompatible hydrogels capable of providing a physical barrier and ample hydration are increasingly utilized for this purpose. However, hydrogels often lack sufficient adhesive and cohesive strengths compared to traditional adhesives, especially under a hydrated environment. In this study, a thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) hydrogel was developed as a pressure-sensitive adhesive using a catechol-modified acrylic hyperbranched polyglycerol crosslinker ('CAHPG'). The presence of both acrylate and catechol on HPG enhances the mechanical properties of the PNIPAm hydrogel by chemical crosslinking of acrylate and physical interaction of catechol with the surrounding PNIPAm chains, while the adhesive properties are mainly conferred by catechol. More notably, the adhesiveness of the PNIPAm-CAHPG hydrogels is "activated" above the transition temperature of PNIPAm due to the thermoresponsive deswelling driven by the increased hydrophobicity, removing the hydration layer at the interface to maximize the adhesive interaction. This unique characteristic of the PNIPAm-CAHPG hydrogel, coupled with the ability to deliver therapeutic agents to further promote wound healing, is demonstrated to be highly suited for "on-demand" tissue adhesive applications.