The in vivo transport of elastic vesicles into human skin: effects of occlusion, volume and duration of application.

In the present study, several aspects of elastic vesicle transport into human skin were investigated in vivo. Surfactant-based elastic vesicles were applied onto human skin in vivo and subsequently a series of tape-strippings were performed, which were visualised by freeze fracture electron microscopy. Factors of investigation for non-occlusive treatment were the duration of application and the volume of application. In addition, occlusive vs. non-occlusive application was studied. The results have shown a fast penetration of intact elastic vesicles into the stratum corneum after non-occlusive treatment, frequently via channel-like regions. Intact vesicles could reach the ninth tape-strip after the 1-h non-occlusive treatment. After the 4-h treatment, vesicle material could be found in the 15th tape-strip. However, micrographs of the 4-h treatment showed extensive vesicle fusion, both at the skin surface as well as in the deeper layers of the stratum corneum. A higher volume of application resulted in an increase in the presence of vesicle material found in the deeper layers of the stratum corneum. Micrographs after occlusive treatment revealed very few intact vesicles in the deeper layers of the stratum corneum, but the presence of lipid plaques was frequently observed. Furthermore, we have proposed a hypothesis that the channel-like regions represent imperfections within the intercellular lipid lamellae in areas with highly undulating cornified envelopes.