A Tough Janus Hydrogel Patch with Strong Wet Adhesion and Self-Debonding for Oral Ulcer Treatment

Oral ulcers (OU) are the most common oral mucosal disease in humans across all geographic regions, seriously affecting patients' quality of life and even leading to irreversible loss of function. Existing clinical treatments, such as ointments, sprays, and oral patches, are often washed out by saliva within a few hours, posing challenges for dentists. Adhesive hydrogel dressings show promise to address these issues, but existing options lack wet adhesion, flexibility, and gentle debonding, limiting their application in dynamic wet environments like the oral cavity. To overcome these limitations, a hydrogen-bond-based Janus hydrogel patch was developed. N-[Tris(hydroxymethyl)methyl]-acrylamide (THMA) and chitosan (CS) were selected as the composites of the adhesive layer in this hydrogel, and the high-density hydrogen bonding provided by THMA and the topological adhesion synergy of CS greatly enhanced the wet adhesion performance of the hydrogel. A high-tenacity poly(ethylene glycol) diacrylate (PEGDA)-based hydrogel acts as a tough layer, providing flexibility, effective adhesion, and a physical barrier. The Janus hydrogel patch can instantly adhere to the oral mucosal wound and withstand chewing, biting, and other mouth movements; avoid external stimulation; and continuously release drugs to promote the repair of oral mucosal diseases. In particular, the hydrogel patch can gently and automatically debond after drug delivery, thereby achieving convenient operation and excellent therapeutic efficacy.