Polylactic acid-based dressing with oxygen generation and enzyme-like activity for accelerating both light-driven biofilm elimination and wound healing

Photodynamic therapy (PDT) is a widely used therapeutic approach for eradicating bacterial biofilms in infected wound, but its effectiveness is limited by the hypoxic environment within the biofilm. This study aimed to investigate whether the efficiency of photodynamic removing biofilm is improving by providing oxygen (O₂), as well as the expression of cytokines involved in infected wound healing.

Manganese dioxide (MnO₂) nanoparticles with catalase-like activity were grown in situ on graphitic phase carbon nitride (g-C₃N₄, CN) nanosheets to construct an all-in-one CN-MnO₂ nanozyme, which was then incorporated into poly-L-lactic acid (PLLA) to prepare CN-MnO₂/PLLA wound dressing by electrospinning. Subsequently, the in vitro antibacterial biofilm ratio and antibacterial ratio of CN-MnO₂/PLLA wound dressing were examined by spread plate and crystal violet staining under irradiation with 808 nm near-infrared light and 660 nm visible light. Meanwhile, the rat skin injury model was established, and hematoxylin and eosin (H&E), Masson’s, tumor necrosis factor-α (TNF-α), Arginase 1 (Arg-1), vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (BFGF) were evaluated in vivo to assess the effect of CN-MnO₂/PLLA wound dressing on wound healing.

Biofilm density caused by Staphylococcus aureus and Pseudomonas aeruginosa had elimination rates of 83 and 62%, respectively, when treated with CN-MnO₂/PLLA dressing. Additionally, the dressing exhibited high antibacterial efficacy against both bacteria, achieving 99 and 98.7% elimination of Staphylococcus aureus and Pseudomonas aeruginosa, respectively. Furthermore, in vivo experiments showed that the CN-MnO₂/PLLA wound dressing achieved complete healing of infected wounds on Day 14, with a wound healing rate of >99% by increasing collagen deposition, expression of anti-inflammatory cytokine Arg-1, vascularization cytokine VEGF, and epithelial cell BFGF, and inhibiting the expression of inflammatory cytokine TNF-α.

The CN-MnO₂/PLLA wound dressing exhibited excellent antibacterial properties in vitro and in vivo. In addition, CN-MnO₂/PLLA wound dressing accelerated rapid wound healing through an anti-inflammatory, pro-vascular regeneration and skin tissue remodeling mechanism.