Mitochondria-Targeted Hydrogen Sulphide Delivery via an Adhesive Hydrogel Modulates Inflammation and Oxidative Stress in Diabetic Wounds

Chronic diabetic wounds are challenging to treat due to persistent inflammation, oxidative stress, impaired angiogenesis, and dysregulated matrix remodelling. Hydrogen sulphide (H₂S) has emerged as a therapeutic mediator with antioxidant, anti-inflammatory, and pro-angiogenic properties; however, its clinical translation is limited by volatility and a short biological half-life. Controlled delivery systems, such as hydrogels, are therefore required to harness its potential. This study aimed to develop and evaluate a sodium 2-acrylamido-2-methylpropane sulfonate (Na-AMPS)-based adhesive hydrogel incorporating AP39, a mitochondria-targeted H₂S donor, for sustained localised delivery and promotion of wound healing. Hydrogel formulations were characterised for rheological behaviour, adhesion, swelling, and AP39 release. Cytocompatibility was assessed in human umbilical vein endothelial cells (HUVECs); human dermal fibroblasts, adult (HDFa); and keratinocytes. Anti-inflammatory, antioxidant, and matrix-modulatory effects were evaluated via interleukin-6 and 8 (IL-6/IL-8) secretion, reactive oxygen species (ROS) levels, mitochondrial membrane potential, matrix metalloproteinase-9 (MMP-9), and transforming growth factor-beta (TGF-β). Functional wound healing activity was assessed using tube formation and scratch assays in endothelial cells. AP39-loaded hydrogels exhibited predominantly elastic, shear-thinning behaviour, strong adhesion, rapid hydration, and sustained release of AP39 (11.63 ± 1.20% over 24 h). Across all cell types, 500 nM concentrations of AP39 were well tolerated. In diabetic-like stress conditions, AP39 significantly decreased ROS in HUVECs (50122 ± 5999 to 33,087 ± 1865 AU; <i>p</i> < 0.0001) and HDFa cells (41,367 ± 4225 to 29,813 ± 2406 AU; <i>p</i> < 0.0001). AP39 improved mitochondrial membrane potential in both cell types (<i>p</i> < 0.01-0.001) and decreased pro-inflammatory cytokines. IL-6 decreased in HUVECs (96.05 ± 4.22 pg/mL to 60.99 ± 4.21 pg/mL; <i>p</i> < 0.0001) and HDFa cells (77.54 ± 8.94 pg/mL to 52.25 ± 6.78 pg/mL; <i>p</i> < 0.001), whilst in HDFa cells, MMP-9 was reduced (419.4 ± 25.51 pg/mL to 174 ± 15.1 pg/mL; <i>p</i> < 0.0001). Finally, wound closure was enhanced in HUVECs. The AP39-loaded Na-AMPS hydrogel represents a multifunctional wound dressing capable of controlled H₂S delivery, mechanical stability, and biological activity to support tissue repair in diabetic wound environments. These results highlight this gel's therapeutic potential for diabetic wound treatment.