DEVELOPMENT OF A MODEL OF THE LIPID CONSTITUENT PHASE OF THE STRATUM-CORNEUM .1. PREPARATION AND CHARACTERIZATION OF SKIN LIPID LIPOSOMES USING SYNTHETIC LIPIDS

Liposomes were prepared using four commercially available synthetic lipids, namely, ceramides, cholesterol, cholesterol sulfate, and palmitic acid, which represent the lipid classes found in the stratum corneum. The appropriate conditions for the preparation of liposomes were determined. Hydration of the four lipids, combined at different compositions by conventional hydration methods at 55-degrees-C, revealed that the lipid mixtures existed in equilibria that contained free (unentrapped) lipids in addition to liposomes. Variation in lipid composition resulted in suspensions whose composition always differed from that of the starting materials. In all cases, the disparities were reflected in their trapped volume as well as in their bilayer-forming ability. The lipid composition of the liposomes was modified to obtain a final formulation that formed a stable monolayer at a surface pressure similar to that obtained by lipids extracted from mouse stratum corneum. The results suggest that the modified synthetic lipid mixture could be used to form bilayers that are similar in composition and cohesiveness to the lipid bilayers of the stratum corneum.