Comparison of Stratum Corneum Penetration and Localization of a Lipophilic Model Drug Applied in an O/W Microemulsion and an Amphiphilic Cream

The study compared the penetration and localization of the lipophilic dye curcumin when applied in an oil-in-water (o/w) microemulsion versus an amphiphilic cream on the skin of 6 human volunteers. Using tape stripping and laser scanning microscopy, it was found that the microemulsion allowed deeper penetration into the stratum corneum (SC) and hair follicles, with significantly less curcumin remaining on the skin surface compared to the cream. The microemulsion facilitated penetration into the complete follicular infundibula, whereas the cream only reached the follicular orifices. This indicated that lipid layers and follicles are preferred pathways for the lipophilic dye in the microemulsion.