A Janus adhesive hydrogel via one-pot phase separation for wound healing

Janus bio-adhesive hydrogels are promising for preventing postoperative tissue adhesions. However, integrating adhesive and non-adhesive interfaces entail multiple processes, posing challenges in meeting complex clinical demands. Herein, a Janus chitosan (CS) and poly (ethylene glycol) methacrylate (PEGMA) hydrogel (CS/PEG hydrogel) was developed via a one-pot phase separation polymerization process. This phase separation was driven by a simultaneous hydrogelation upon ultraviolet light irradiation on the top and heating at the bottom of the precursor solution. The light-induced surface (denoted as LIS) was rich in CS, while the heat-induced surface (denoted as HIS) contained a large amount of PEGMA. Non-adhesion HIS due to a large amount of PEG exhibited a pore size of 235.0 ± 11.3 μm, permitting mature vascularization. Adhesive LIS containing CS maximized the adhesiveness of the untreated wound, reaching 94.1 ± 3.3 J·m⁻². The three-dimensional crosslinking network ensured adequate strength to match the mechanical properties of skin with tensile modulus and compressive modulus reaching 32.2 kPa and 121.9 kPa, respectively. In vitro and in vivo experiments confirmed that this Janus hydrogel achieved nearly complete wound closure (>96%) within 14 days by promoting antibacterial activity, anti-inflammation, epithelialization, angiogenesis, and collagen deposition. The straightforward one-step integration of biocompatible CS and PEG to produce asymmetric hydrogel creates new opportunities for manufacturing adhesive dressings in advanced tissue repair scenarios.