Biogenic silver nanoparticle-loaded injectable thermosensitive chitosan hydrogels accelerate repair of non-infected burn wounds

Burn wounds are susceptible to microbial contamination, inflammation, fluid loss and delayed repair, highlighting the need for local formulations that conform to wound beds and support healing. Silver nanoparticles (AgNPs) have broad antibacterial potential, but direct topical application can be limited by aggregation, burst exposure and local toxicity. Here, phytogenic AgNPs previously synthesized from Ricinus communis and Aloe barbadensis leaf extracts were incorporated into injectable thermosensitive chitosan/glycerol-2-phosphate hydrogels. The formulations were designated Ch-HI, Ch/Rc-AgNP-HI and Ch/Ab-AgNP-HI and evaluated for physicochemical properties, sol-gel transition, swelling, AgNP content and entrapment efficiency, apparent release of Ag-containing species, erosion, morphology, thermal behavior, antibacterial activity, cytocompatibility and burn wound repair. The AgNP-loaded hydrogels showed near-physiological pH, rapid gelation near body temperature, porous morphology, apparent Ag-containing species release over 30 h and gradual matrix erosion over 21 days. The formulations demonstrated in vitro antibacterial activity against Escherichia coli and Staphylococcus aureus and maintained HFF-1 fibroblast viability above the 70% cytotoxicity threshold across 1–50 μg/mL. In a female BALB/c mouse second-degree burn wound model, daily administration of 50 µL formulation for three consecutive days promoted wound closure; Ch/Rc-AgNP-HI and Ch/Ab-AgNP-HI achieved 99.34% ± 0.4% and 98.75% ± 0.6% wound contraction by day 14 and complete closure by day 21. Microbial surveillance showed no detectable bacterial growth in any group, indicating a non-infected burn wound repair model. Histological and biochemical analyses further showed improved re-epithelialization, collagen organization, hydroxyproline deposition and dry matter recovery. These findings support phytogenic AgNP-loaded injectable chitosan/β-GP hydrogels as promising platforms for non-infected burn wound repair, with antibacterial potential demonstrated in vitro .