A Breakthrough Straightforward Multifunctional Hydrogel Platform Releasing Therapeutic Gas for Advanced Wound Healing

The advancement of therapeutic gas treatment has significantly impacted on the biomaterial field, with nitric oxide (NO) gaining attention for its safety, multifunctionality, and role in regulating biological processes. Thus, this study introduces a novel biocatalytic NO-generating in situ forming hydrogel (GTA/Cu) to address wound-related issues, fabricated through a simple, one-step process by incorporating copper ions (Cu²⁺) into tannic acid-conjugated gelatin (GTA). Herein, Cu²⁺ functions simultaneously as a crosslinking agent, NO-generating catalyst, and antibacterial agent, while the galloyl groups in GTA enable effective tissue adhesion and diverse crosslinking interactions. The hydrogels' mechanical properties are controlled by varying Cu²⁺ concentrations (25, 50, and 100 mg/mL), with higher concentration accelerating gelation and enhancing mechanical strength. At 100 mg/mL Cu²⁺, the hydrogel releases NO for up to 12 days, reaching a cumulative concentration of around 200 μM. It also demonstrated robust antioxidant activity, high tissue adhesion (~20 kPa), and comparable antibacterial effects to Cu-only samples. Interestingly, the released NO facilitates endothelial cell proliferation, accelerates scratch closure within 36 h, and stimulates new tube formation on Matrigel, showing comparable effects to VEGF. Additionally, it clearly promotes new blood vessel formation in vivo following subcutaneous injection, further highlighting its potential for practical wound healing applications.