JOURNAL OF COSMETIC SCIENCE 244 a lower polydispersity index, and greater stability than liposomes formed with IWL ob- tained by SFE, which were richer in sterol. The modifi cation of the properties in intact skin after daily application of IWL structured as liposomes was investigated. The IWL liposomes improved skin barrier integrity and increased skin hydration when applied onto intact skin. These results were slightly en- hanced when IWL liposomes richer in polar lipids were applied. Moreover, protection of intact skin against detergent action was confi rmed for the three samples, the results being slightly better in the case of IWL liposomes that were richer in sterol. These results sup- port the benefi cial effects of skin lipid supplementation given that IWL resemble those in the stratum corneum both in composition and in organization. ACKNOWLEDGMENTS We thank all the volunteers who participated in these trials. We are also indebted to Mr. G. von Knorring for his expert technical assistance and to the MEC program (Project PPQ2002-04136-C02-01) for fi nancial support. REFERENCES (1) L. Coderch, C. Soriano, A. de la Maza, P. Erra, and J. L. Parra, Chromatographic characterization of in- ternal polar lipids from wool, J. Am. Oil. Chem. Soc., 72, 715–720 (1995). (2) H. Schaefer and T. E. Redelmeier, Skin barrier: Principles in percutaneous penetration (Basel, Karger, 1996), pp. 55–58. (3) J. Fonollosa, M. Martí, A. de la Maza, J. L. Parra, and L. Coderch, TLC-FID analysis of the ceramide content of internal wool lipids, J. Planar. Chrom., 13, 119–122 (2000). (4) L. Coderch, I. Bondía, J. Fonollosa, S. Méndez, and J. L. Parra, Ceramides from wool: Analysis and structure, IFSCC Magazine, 6, 117–123 (2003). (5) P. M. Elias, Lipids and the epidermal permeability barrier, Arch. Dermatol. Res., 270, 95–117 (1981). (6) L. Yang, M. Mao-Qiang, M. Taljebini, P. M. Elias, and K. R. Feingold, Topical stratum corneum lipids accelerate barrier repair after tape stripping, solvent treatment and some but not all types of detergent treatment, Br. J. Dermatol., 133, 679–685 (1995). (7) M. Mao-Qiang, K. R. Feingold, C. R. Thornfeldt, and P. M. Elias, Optimization of physiological lipid mixtures for barrier repair, J. Invest. Dermatol., 106, 1096–1101 (1996). (8) A. Körner, S. Petrovic, and H. Höcker, Cell membrane lipids of wool and human hair form liposomes, Text. Res. J., 65, 56–58 (1995). (9) L. Coderch, A. de la Maza, A. Pinazo, and J. L. Parra, Physicochemical characteristics of liposomes formed with internal wool lipids, J. Am. Oil. Chem. Soc., 73, 1713–1718 (1996). (10) M. H. Schmid and H. C. Korting, Liposomes for atopic dry skin: The rationale for a promising ap- proach, Clin. Invest., 71, 649–653 (1993). (11) M. Fresta and G. Puglisi, Corticosteroid dermal delivery with skin-lipid liposomes, J. Controlled Release, 44, 141–151 (1997). (12) L. Coderch, M. de Pera, N. Pérez-Cullell, J. Estelrich, A. de la Maza, and J. L. Parra, The effect of lipo- somes on skin barrier structure, Skin Pharmacol. Appl. Skin Physiol., 12, 235–246 (1999). (13) M. de Pera, L. Coderch, J. Fonollosa, A. de la Maza, and J. L. Parra, Effect of internal wool lipid lipo- somes on skin repair, Skin Pharmacol. Appl. Skin Physiol., 13, 188–195 (2000). (14) L. Coderch, M. de Pera, J. Fonollosa, A. de la Maza, and J. L. Parra, Effi cacy of stratum corneum lipid supplementation on human skin, Contact Dermatitis, 47, 139–146 (2002). (15) L. Coderch, J. Fonollosa, M. de Pera, A. de la Maza, J. L. Parra, and M. Martí, Compositions of internal lipid extract of wool and use thereof in the preparation of products for skin care and treatment, N° 9901541 (1999). (16) R. Ramírez, M. Martí, A. Manich, J. L. Parra, and L. Coderch, Ceramides extracted from wool: Pilot plant solvent extraction, Text. Res. J., 78, 73–80 (2008).

IWL LIPOSOMES AND SKIN BARRIER IMPROVEMENT 245 (17) R. Ramírez, M. Martí, I. Garay, A. M. Manich, J. L. Parra, and L. Coderch, Ceramides extracted from wool: Supercritical extraction processes, Text. Res. J., 79, 721–727 (2009). (18) E. Berardesca and H. I. Maibach, Transepidermal water loss and skin surface hydration in the non-inva- sive assessment of stratum corneum function, Derm. Beruf. Umwelt., 38, 50–53 (1990). (19) J. Pinnagoda, R. A. Tupker, T. Agner, and J. Serup, Guidelines for transepidermal water loss (TEWL) measurement. A report from the standardization group of the European Society of Contact Dermatitis, Contact Dermatitis, 22, 164–178 (1990). (20) E. Berardesca, EEMCO guidance for the assessment of stratum corneum hydration: Electrical methods, Skin Res. Technol., 3, 126–132 (1997). (21) V. Rogiers, EEMCO guidance for the assessment of transepidermal water loss in cosmetic sciences, Skin Pharmacol. Appl. Skin Physiol., 14, 117–128 (2001). (22) R. A. Tupker, C. Willis, E. Berardesca, C. H. Lee, M. Fartasch, T. Agner, and J. Serup, Guidelines on sodium lauryl sulfate (SLS) exposure tests. A report from the Standardization Group of the European Society of Contact Dermatitis, Contact Dermatitis, 37, 53–69 (1997). (23) L. Coderch, J. Fonollosa, M. Martí, F. Garde, A. de la Maza, and J. L. Parra, Extraction and analysis of ceramides from internal wool lipids, J. Am. Oil. Chem. Soc., 79, 1215–1220 (2002). (24) P. W. Wertz, W. Abraham, L. Landmann, and D. T. Downing, Preparation of liposomes from stratum corneum lipids, J. Invest. Dermatol., 87, 582–584 (1986). (25) L. Coderch, O. López, A. de la Maza, and J. L. Parra, Ceramides and skin function, Am. J. Clin. Dermatol., 4, 107–129 (2003). (26) N. Pérez-Cullell, L. Coderch, A. de la Maza, J. L. Parra, and J. Estelrich, Infl uence of the fl uidity of lipo- some compositions on percutaneous absorption, Drug Delivery, 7, 7–13 (2000).