IWL LIPOSOMES AND SKIN BARRIER IMPROVEMENT 243 SLS exposure has a much greater effect on TEWL (Figure 5), which refl ects the skin bar- rier function. TEWL values decrease in the zones treated with the three IWL liposome samples with respect to control and placebo zones, which is indicative of the recovery of the skin barrier function. The variation in TEWL after SLS exposure in the zones treated with liposomes formed with IWL extracted by SFE is signifi cant, with a decrease of about 10% in TEWL. This effect could be attributed to the larger size of the liposomes pre- pared with lipids extracted by SFE. These liposomes could remain in the external layers of the stratum corneum, thereby preventing some of the damaging effects of the surfac- tant insult. Moreover, the larger amount of sterol present in liposomes formed with SFE extracts could induce a decrease in the fl uidity of the lipid bilayer (26), which could lead to decreased penetration of these liposomes in deeper skin layers. In summary, different lipid mixtures extracted from wool fi bers have been demonstrated to form stable liposomes. Their application onto skin increases skin hydration and im- proves skin barrier integrity. Therefore, wool lipid mixtures could provide a new ap- proach to treatments of skin pathologies characterized by structural alterations in the stratum corneum, resulting in a loss of barrier function (25). CONCLUSIONS IWL extracted by OSE using pure methanol were richer in sterol sulfate than IWL ex- tracted by SFE with 10% methanol or ethanol as modifi ers, whereas a similar percentage of the three main lipid families (free fatty acids, sterols, and ceramides) was analyzed in the three IWL extracts. Both the formation and the characteristics of the liposomes pre- pared were considerably infl uenced by the IWL composition. The lower amount of sterol sulfate contained in lipids extracted with SFE hinders the formation of liposomes. Lipo- somes prepared from IWL extracted by OSE were richer in polar lipids such as ceramides, glycosilceramides, and sterol sulfate. These liposomes presented a smaller vesicular size, Figure 5. Variation of TEWL after SLS exposure. The intact skin was previously treated with IWL liposomes (*p 0.05, calculated between samples and control and placebos). Changes were evaluated versus baseline values (SLS-treated skin).

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).