Chitosan gel loaded with carbon dots and mesoporous hydroxyapatite nanoparticles as a topical formulation for skin...

Carbon dots (CDs) are the research hotspots in antimicrobial applications. Also, due to the importance of calcium ions in skin regeneration, mesoporous hydroxyapatite nanoparticles (mHAP NPs) were prepared. This study aimed to evaluate the wound healing efficiency of both CD and mHAP NPs simultaneously.

We doped Fluorine (F) and Copper (Cu) in CDs to prepare Cu*F-doped CDs (Cu.CDs). For the rapid release of calcium ions, a novel double-surfactant system (CTAB/F-127) was used for the synthesis of mHAP NPs. Then, we loaded both Cu.CDs and mHAP NPs simultaneously into the chitosan (CTS) gel.

The released calcium for mHAP NPs prepared using CTAB/F-127 was proved about 30 % higher than that prepared using only CTAB, after one day. The BET-specific surface area for mHAP NPs prepared using CTAB/F-127 was 23.17 % more than that prepared using only CTAB. This high porosity improves wound exudate absorption. Rheological analysis showed that the addition of both mHAP NPs and Cu.CD decreases the viscosity of CTS gel and thereby makes it suitable for topical applications. CTS gel containing mHAP + Cu.CDs indicated exceptional antibacterial properties even without light and/or H₂O₂ with an inhibition zone diameter of 35 and 17 mm for E. coli and S. aureus species, respectively. CTS gel containing mHAP + Cu.CDs also showed significantly higher wound closure efficacy, greater inflammation inhibition, and better re-epithelialization than the other groups in rats with full-thickness skin wounds.

The CTS gel containing both Cu.CD and mHAP NPs can be proposed as a new therapeutic gel for wound healing.