Waste-derived marigold flower carbon dot spray and gel formulations exhibit enhanced wound healing in deep excisional cutaneous and burn wounds

Bioactive carbon dots have shown significant progress in biomedical therapeutics due to their unique physicochemical characteristics and exceptional biocompatibility. This work focuses on the synthesis, characterization, and biomedical evaluation of carbon dots (CDs) extracted from waste and discarded marigold flowers for wound healing applications. The synthesized CDs exhibited a uniform size distribution of 2-5 nm and a zeta potential of -15.8 mV, indicating moderate stability against aggregation. Excitation-dependent photoluminescence was observed, with maximum intensity at 380 nm. In comparison, the UV-Vis adsorption spectrum showed a peak at 278 nm, corresponding to the π-π* transition of sp² carbon domains. Additional FTIR and XPS analyses revealed the presence of functional groups, including hydroxyl, carbonyl, and aromatic domains, and confirmed nitrogen and oxygen doping, which enhanced hydrophilicity and reactivity, respectively. <i>In vitro</i> cytocompatibility assays using MTT and FDA showed maximum cell viability at 500 μg mL^-1. Macroscopic examination of the scratch assay showed promising results, with cells and fibroblasts achieving a 98.97% wound healing rate at 48 h compared to control values. <i>In vivo</i> experiments on deep excisional full-thickness and burn injuries exhibited enhanced wound contraction, ECM deposition, angiogenesis, and faster healing with CD gel and spray compared to the control and standard treatments. Histology and immunohistochemistry supported enhanced collagen synthesis and remodeling in the treated tissue; however, the gel demonstrated marginally superior results compared to the spray, as it adhered more securely. These results show that the developed marigold-derived CDs are biocompatible, promote angiogenesis, and enhance healing of deep excisional and burn wounds.