Reconstructed human skin as model for liposome-skin interaction

Reconstructed human skin was prepared from human keratinoblasts. After 1 week of cultivation at the air-liquid interface a stratified layer developed, similar to native human epidermis. Liposomes with an average diameter of 50 nm, made of phosphatidylcholine (PC), phosphatidylserine (PS) and human stratum corneum lipids (hSCL) were applied on top of this culture system. The rate of penetration through the reconstructed human epidermis was 1.38, 0.55 and 0.013 ng lipidh-1cm-2 for PC, hSCL and PS liposomes, respectively. Electron microscopy and confocal laser scanning microscopy showed that PS and hSCL liposomes aggregated at the skin surface, while PC liposomes remained homogeneously dispersed. Fluorescence measurements demonstrated that vesicles, made of native human stratum corneum lipids rapidly mixed with PS liposomes, weakly with hSCL liposomes and did not mix with PC liposomes.