Alginate-based composite hydrogel derived from Azotobacter vinelandii Av1: Preparation, properties, and wound-healing...

Mannuronic acid-enriched alginate has demonstrated significant potential for wound healing. However, the M/G ratio of alginate derived from seaweed exhibits considerable variability, whereas alginate obtained from bacterial sources shows greater consistency in quality. In addition, conventional alginate dressings often fail to satisfy the stringent requirements of medical applications in terms of water absorption and stability. In this study, a high mannuronic acid-content alginate (Av) was extracted from Azotobacter vinelandii Av1 and characterized. Av possesses a molecular weight of 2100 kDa and consists of 10.6% guluronic acid (G) and 89.4% mannuronic acid (M). Composite hydrogels of gelatin‑sodium alginate (GE-SA) and gelatin-Av (GE-Av) were subsequently prepared to evaluate their wound healing properties. GE-Av exhibited enhanced water absorption and stability compared to GE-SA. Moreover, GE+3%Av significantly promoted human skin fibroblast migration by upregulating epidermal growth factor (EGF) expression, achieving a 75.3% wound closure rate at 24 h. In full-thickness mouse wound models, GE+3%Av accelerated wound healing relative to both the native control and GE-SA groups. Histological analysis further revealed that GE+3%Av facilitated skin epithelialization and collagen deposition. Collectively, these findings indicate that the GE+3%Av composite hydrogel represents a promising candidate for wound healing and skin regeneration.