Q10-loaded NLC versus nanoemulsions: Stability, rheology and in vitro skin permeation

In this study, nanoemulsions (NE) of medium chain triacylglycerols (MCT) and nanostructured lipid carriers (NLC) of cetyl palmiate/MCT were produced to load coenzyme Q10 (Q10) and characterized for their stability before and after incorporation into xanthan gum hydrogels. After storage at 4, 25 and 40 °C, the particles remained in the nanosize range for 12 months, with zeta potential higher than |40 mV|. Similar results were found in xanthan gum-based hydrogels containing NE or NLC. The crystallinity index of Q10-loaded NLC increased after being incorporated into hydrogels. The Q10 entrapped in NLC and NE remained higher than 90% at all temperatures for 12 months but dramatically decreased when exposed to light. From the rheological studies, both NLC and NE dispersions possessed pseudoplastic flow having more liquid characteristics, whereas NLC and NE hydrogels exhibited plastic flow with thixothopy, showing more elastic rather than viscous properties. The occurrence of a spatial arrangement of lipid molecules was observed in the matrix of NLC when entrapped into hydrogels. From in vitro permeation studies, it could be stated that the amount of Q10 released and occlusiveness were major keys to promote the deep penetration of Q10 into the skin.