DAMAGED HAIR AND CERAMIDE-RICH LIPOSOMES 575 where an increase in the tshort was also observed. This could be related to the high lipid absorption of these two samples. As seen in the lipid analysis, the IWL liposomes trig- gered an increase mainly in the content of polar lipids (ceramides, glycosilceramides, and cholesterol sulfate). All these lipids have N-H and O-H groups, which can form hydro- gen bonds, and some of them are charged, with the result that they can interact with other charged groups. All these lipids could account for an increase in the amount of weak bonds in hair fi bers. The σinterm and the tinterm indicated that the amount of intermediate bonds decreased in the treated fi bers as well as in the case of weak bonds. An increase in intermediate relaxed stress and intermediate relaxation time was observed when IWL liposomes were applied. Again, the IWL application improved the cohesion between the matrix and fi laments, especially in the case of the untreated and bleached samples. Some variations in non-relaxed stress caused modifi cations in the percentage of disulfi de bonds of the protein structure. After the application of IWL liposomes, strong bonds normally decreased because of the increase in the percentage of weak bonds, which were generated by IWL liposomes. These new lipids (IWL) were not able to form or destroy disulfi de bonds. The strength and relaxation studies indicate a high resistance to break of the untreated, bleached, and permed samples post-treated with IWL liposomes. This was accompanied by an increase in the short and intermediate relaxed stress. This indicates an increase in hydrogen bonds and electrostatic forces and an improvement in cohesion between the matrix and the fi laments, probably because of some lipid recovery. CONCLUSIONS Lipid analysis of chemically treated samples showed a reduction in the amount of lipids, cholesterol and cholesterol sulfate being the most affected. The permed sample had a lipid composition that most resembled native hair. The bleached extract showed lower amounts of free fatty acids, and the relaxed extract had smaller amounts of ceramides. Lipid recovery of damaged human hair by the application of IWL liposomes can be cor- roborated by lipid analysis of the hair. An increase in the lipids analyzed confi rms the absorption of IWL into the fi ber. There is a selective absorption of polar lipids, ceramides, glycosilceramides, and cholesterol sulfate by the undamaged and damaged hair fi bers. The role of cholesterol sulfate in maintaining the bilayer structure could be related to moisture retention, elasticity, and the strength of the fi bers. The thermogravimetric analyses showed few differences in the water content of the hair as a result of chemical pretreatments and IWL liposome application. There was a small decrease in the external water content owing to the pretreatments, whereas an increase was observed after IWL liposome application, especially in the case of bleached hair. Lower breaking stresses were obtained in all the chemically treated hairs, which indicated lower hair reticulation. The application of IWL improved breaking stress and deforma- tion at break and led to an increase in the breaking work of untreated hair. Little im- provement was obtained in the case of the chemically treated hair. Only a slight increase in the resistance to break was observed in the bleached and permed samples. Moreover, the relaxation study showed a decrease in weak and intermediate bonds in the chemically

JOURNAL OF COSMETIC SCIENCE 576 treated hair samples, probably because of a decrease in their lipidic composition. IWL were able to improve the cohesion between the fi bers, increasing the hydrogen bonds and electrostatic forces and improving the cohesion between the matrix and the fi laments. This is especially true in the case of non-treated and bleached samples. ACKNOWLEDGMENTS The authors acknowledge the fi nancial support of the National Projects from Ministerio de Educación y Ciencia (Spain), Ref. CTQ2006-15404-C03-01 and CTQ2009-13967- C03-01, and the technical support of Mr. J. Carilla. Also, this work was supported by Keratec Limited (New Zealand). REFERENCES (1) S. B. Ruetsch and H. D. Weigmann, Mechanism of tensile stress release in the keratin fi ber cuticle, Proc. 9th Int. Wool Textile Research Conf., 2, 44–55 (1995). (2) J. D. Leeder, The cell membrane complex and its infl uence on the properties of the wool fi bre, Wool Sci. Rev., 63, 3–35 (1986). (3) J. A. Swift and A. W. Holmes, Degradation of human hair by papain. Part III. Some electron microscope observations, Text. Res. J., 35, 1014–1019 (1965). (4) A. K. Allen, J. Ellis and, D. E. Rivett, The presence of glycoproteins in the cell membrane complex of a variety of keratin fi bres, Biochim. Biophys. Acta, 1074, 331 (1991). (5) G. P. Mitchell, J. Mifsud, D. E. Rivett, and A. K. Allen, Characterization of formic acid-derived cell membrane complex protein from wool, Biochem. Soc. Trans., 20, 90S (1992). (6) L. N. Jones and D. E. Rivett, The role of 18-methyleicosanoic acid in the structure and formation of mammalian hair fi bres, Micron. 28, 469–485 (1997). (7) L. Duvel, D. Chun, D. Deppa, and P.. Wertz, Analysis of hair lipids and tensile properties as a function of distance from scalp, Int. J. Cosmet. Sci., 27, 193–197 (2005). (8) K. Nishimura, M. Nishino, Y. Inaoka, Y. Kitada, and M. Fukushima, Interrelationship between the hair lipids and the hair moisture, Nippon Koshohin Kagakkaishi, 13, 134–139 (1989). (9) Y. Masukawa, H. Narita, and G. Imokawa, Characterization of the lipid composition at the proximal root regions of human hair, J. Cosmet. Sci., 56, 1–6 (2005). (10) D. Braida, G. Dubief, G. Lang, and P. Hallegot, Ceramide: A new approach to hair protection and con- ditioning, Cosmet. Toiletr., 109, 49–57 (1994). (11) 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). (12) 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, JAOCS, 79, 1215–1220 (2002). (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. 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, Patent WO/2001/004244. (16) S. Méndez, C. Barba, A. Roddick-Lanzilotta, R. Kelly, J. L. Parra, and L. Coderch, Application of inter- nal wool lipids to hair, Skin Res. Technol., 14, 448–453 (2008). (17) R. Kelly, A. Roddick-Lanzilotta, S. Vorwerk, and L. Coderch, Treatement of hair or nails with internal wool lipids, Patent WO/2007/098075. (18) R. Ramírez, M. Martí, A. Cavaco-Paulo, R. Silva, A. De la Maza, J. L. Parra, and L. Coderch, Liposome formation with wool lipid extracts rich in ceramides, J. Liposom. Res., 19, 77–83 (2009). (19) N. Hayashi, A. Koyanagi, S. Daikai, N. Gotou, Y. Ueda, and K. Uehara, Effect to hair conditioner, an uniquely developed hybrid polymer consisted of hydrolyzed wheat protein, silicone and alkyl chain, Proc. 24th IFSCC Congress, Osaka, Japan, PE-216, 432–433 (2006).