Elastic vesicles as a tool for dermal and transdermal delivery.

The main problem in delivery of drugs across the skin is the barrier function of the skin, which is located in the outermost layer of the skin, the stratum corneum. The stratum corneum consists of corneocytes surrounded by lipid layers, the so-called lipid lamellae. When applying drugs onto the skin, the major penetration pathway is the tortuous intercellular route along the lipid lamellae. In order to increase the number of drugs administered via the transdermal route, novel drug delivery systems have to be designed. Among these systems are iontophoresis, electroporation, microneedles, and vesicular systems.

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.