Design of nonanoic acid composite vesicles as cosmetics carrier: Stability, skin permeability, antioxidant and antibacterial activity

Based on the inherent alkaline adaptability of fatty acid vesicles (FAVs) when in contact with the human body, along with the very narrow pH window for the formation and application of FAVs, which is far from the physiological pH range, this study successfully prepared a composite vesicle of non-ionic surfactant Tween60 (TW60) with nonanoic acid (NA) to migrate and expand the pH window. Acid-base titration confirmed that adding varying proportions of TW60 to sodium nonanoate (SN) solutions expanded the pH window from 6.6–7.5 to 1.28–6.52, widening it by 5.24, as determined by conductivity and turbidity. Studies under different conditions such as ionic strength, temperature, and storage time indicated that NA/TW60-FAV exhibited excellent stability. At a myricetin (MYR) concentration of 1 mg/mL and a pH of 6, encapsulation efficiency (EE) was 93.03 ± 0.03 %, and the drug loading capacity (DLC) was 8.65 ± 0.02 %, reaching the highest values. In vitro release and skin permeation results indicated that compared to free MYR solution (1 mg/mL), the skin permeability of the MYR-loaded composite vesicles (NA/TW60/MYR-FAV) was 1.64 times that of the MYR solution, significantly increasing skin absorption and retention, with a pronounced sustained release effect. The antioxidant activity experiments confirmed a significant enhancement in its ability to scavenge DPPH, ferric ions, and hydroxyl radicals (OH). The antibacterial experiments showed that NA/TW60/MYR-FAV had significant inhibitory effects against Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ), indicating potential applications in cosmetics. In summary, the pH range of the blank composite vesicles (NA/TW60-FAV) aligns with the requirements for human skin adaptation, significantly enhancing the intrinsic value of the loaded substance. This indicates that it is a reliable and stable vesicle carrier, offering preliminary evidence for further research and application in the cosmetics industry.