Interaction of liposomes with human epidermis reconstructed in vitro.

Upon topical application of liposomes of the large unilamellar vesicle type to human epidermis reconstructed in vitro, there is a dose-dependent alteration of the morphology of both the stratum corneum and the living part of the epidermis. In particular, shrunken lipid droplets are found between corneocytes and keratinocytes. Sometimes, corneocytes show inclusions reminiscent of 'cholesterol crystals'. Corneocytes, moreover, show a decreased density. Both corneocytes of the various layers of the stratum corneum and keratinocytes belonging to the uppermost layer of the living epidermis show particularly osmophilic membranes, indicating lipid transfer. Intact liposomes or their remnants can sometimes be seen between corneocytes of the upper strata. The presence of liposomal lipid within the stratum corneum is supported by the presence of gold particles used as a marker. There is, however, no evidence for the uptake of intact liposomes by the living epidermis, or their passage through this compartment of the skin.