STRUCTURE OF FULLY HYDRATED HUMAN STRATUM-CORNEUM - A FREEZE-FRACTUREELECTRON-MICROSCOPY STUDY

The structure of fully hydrated human stratum corneum was investigated by means of freeze-fracture electron microscopy. Mammary and abdomina l stratum corneum were incubated for 48 h with phosphate-buffered sali ne, pH 7.4, occlusively or phosphate buffer, pH 7.4, occlusively and n on-occlusively. The micrographs showed the corneocytes aligned paralle l to the surface of the stratum corneum embedded in intercellular lipi ds. The corneocytes were swollen by the uptake of water. New features located in the intercellular lamellar regions were rough structures, w ater pools, and occasionally vesicle-like structures. The nature of th e vesicle-like structures was not completely clear. The presence of wa ter pools, mostly in close contact with the rough structures, suggests that a lipid-water phase separation occurred. The localization of wat er in the intercellular region and the corneocytes offers new insights into the penetration enhancement property of water (and into the path ways of drug penetration).