| Abstract |
The incorporation of low solubility natural substances into cosmetic formulations is an industrial trend posing new challenges and opportunities for fundamental research and cost effective product development. The sub-PIT method, an easily scaled-up low energy process, was used to yield a stable reduced droplet diameter (similar to 20 nm) cationic nanoemulsion, containing a natural quercetin extract (95.5\% w/w), appropriate for cosmetic application. The formulation presented optical transparency and high quercetin concentration (0.5\% w/w). The preparation method was optimized in terms of mixture HLB and temperature. The best polydispersity index was achieved at 80 degrees C. Droplet diameter (DLS), zeta potential, rheological properties and nanodroplet morphology (cryo-TEM and AFM) were evaluated. This nanoemulsion contains spheric droplets with the lowest diameter ever described (to the best of our knowledge) for a cationic nanoemulsion prepared by the sub-PIT method. AFM experiments showed that the nanodroplets adsorb on a highly oriented pyrolytic graphite surface, holding a wettability similar to hair external surface. Accelerated stability assays carried out over 90 days indicated that Ostwald ripening destabilization occurred at 45 C temperature, but was not observed at room temperature. This nanoemulsion exhibits excelent characteristics for application in cosmetics and sets-up a nanotechnological platform for other cosmetic/pharmaceutical applications. (C) 2015 Elsevier B.V. All rights reserved. |
