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J. Cosmet. Sci., 61, 235–245 (May/June 2010) 235 Skin effi cacy of liposomes composed of internal wool lipids rich in ceramides R. RAMÍREZ, M. MARTÍ, C. BARBA, S. MÉNDEZ, J. L. PARRA, and L. CODERCH, Department of Chemical and Surfactant Technology, IQAC (CSIC), Jordi Girona 18-26, 08034 Barcelona, Spain. Accepted for publication November 16, 2009. Synopsis Ceramides from intercellular lipids of skin stratum corneum are known to play an essential role in maintain- ing and structuring the lipid barrier of the skin. Internal wool lipids (IWL), which are also rich in ceramides, have a composition similar to that of the stratum corneum lipids. IWL extracted with chloroform/methanol azeotrope at the laboratory scale have been shown to be capable of forming liposomes with a stable bilayer structure. Furthermore, topical application of these IWL liposomes on intact and compromised skin has been demonstrated to improve barrier skin properties. In this study we evaluated the effect on human skin repair of different IWL extract compositions obtained by two extraction methodologies. The formation and characteristics of the liposomes prepared were greatly infl uenced by the IWL composition, primarily the sterol sulfate content. The IWL liposomes improved skin barrier integrity and increased skin hydration when applied onto intact skin. These improvements were slightly enhanced in the case of IWL liposomes that were richer in polar lipids. INTRODUCTION Wool is a natural fi ber that is mainly comprised of protein. It contains external lipids (lanolin) and a small amount of internal lipids (1.5%). Internal wool lipids (IWL) arouse considerable interest given their high proportion of ceramides. IWL are rich in choles- terol, free fatty acids, cholesteryl sulfate, and ceramides and they resemble those from membranes of other keratin tissues such as human hair or stratum corneum (1–4). Intercellular lipids of stratum corneum, mainly ceramides, play an important role in the bar- rier function of the skin by preventing penetration of external agents and controlling transepi- dermal water loss to maintain the physiological skin water content (5). Recent studies have shown that formulations, especially ceramide supplementation, containing lipids that resem- ble the natural components of the skin can improve compromised skin conditions (6,7). IWL have been extracted from wool on account of their high proportion of ceramides. IWL extracted by Soxhlet extraction at the laboratory scale has been shown to be capable Address all correspondence to L. Coderch.