Preparation of photo-crosslinked microalgae-carboxymethyl chitosan composite hydrogels for enhanced wound healing.

Integrating microalgae into wound dressings has proven effective in promoting chronic wound healing through photosynthesis-induced oxygen release. However, challenges such as high crosslinking temperatures and prolonged gel molding processes limit microalgae growth and reduce the overall therapeutic impact. In this work, inspired by cell-symbiotic photo-crosslinked hydrogels, we present a novel photo-crosslinked microalgae carboxymethyl chitosan composite hydrogel. This hydrogel completes crosslinking at room temperature within 30 s, enhancing chronic wound healing. The composite gel incorporates photosynthesizing unicellular microalgae (Chlamydomonas reinhardtii) and the antimicrobial agent ciprofloxacin during preparation. In light, the gel continues to photosynthesize, releasing oxygen while simultaneously acting as an antibacterial agent. This dual action results in the upregulation of CD31 and VEGFA levels and the downregulation of HIF-1α levels in diabetic wounds. The wound closure rate reached approximately 96.70 % on day 12 in the composite gel group, compared to only 78.98 % in the control group. Therefore, the composite gel promotes healing by reducing local hypoxia, encouraging angiogenesis, and lowering infection risk. These results suggest that photo-crosslinked microalgae composite gels provide an effective strategy for localized oxygen delivery to promote wound healing and offer a viable method for rapidly preparing living biomaterials under suitable conditions.