Coreopsis tinctoria-loaded gels for dermal delivery: development, optimization, retention capacity, and skin...

This study aimed to develop dermal gels loaded with Coreopsis tinctoria (CTGs) and evaluate its therapeutic effect against skin photoaging. The formulation was optimized using viscosity, water loss rate and moisture retention rate as evaluation indexes, and CTGs were prepared and characterized. Dermal release was investigated, and skin retention was evaluated using fluorescence imaging. Finally, a mouse skin photoaging model was established using ultraviolet B (UVB) to evaluate the effects of CTGs on improving skin condition and repairing photoaging damage. CTGs with uniform appearance, appropriate viscosity and good stability were successfully prepared. In vitro drug release from CTGs followed the Korsmeyer-Peppas model. Compared with the liquid formulation, CTGs significantly prolonged skin retention time and improved skin adhesion within 8 h. CTGs attenuated UVB-induced dermal damage, increased SOD activity and hydroxyproline (Hyp) content, and reduced MDA content and tyrosinase (Tyr) activity, indicating strong antioxidant and tyrosinase inhibitory activity. CTGs represent a promising dermal delivery strategy for ameliorating skin photoaging and abnormal pigmentation.