J. Cosmet. Sci., 62, 565–577 (November/December 2011) 565 Damaged hair retrieval with ceramide-rich liposomes SANDRA MÉNDEZ, ALBERT M. MANICH, MERITXELL MARTÍ, JOSÉ L. PARRA, and LUISA CODERCH, Advanced Chemical Institute of Catalonia, (IQAC-CSIC), Jordi Girona 18-26, 08034 Barcelona, Spain. Accepted for publication June 21, 2011. Synopsis Lipids from human hair consist mainly of cholesterol esters, free fatty acids, cholesterol, ceramides, and cholesterol sulfate. They are structured as lipid bilayers in the cell membrane complex (CMC) and make a large contribution to diffusion, cell cohesion, and mechanical strength. The loss of these lipids could im- pair the integrity of the hair, leading to deterioration in its tensile properties. Internal wool lipids (IWL) resemble those of the membranes of other keratinic tissues such as human hair or stratum corneum. The application of IWL structured as liposomes on pretreated hair samples has been demonstrated to restore the natural properties of the fi bers. This study seeks to apply IWL liposomes to untreated hair fi bers and to hair fi bers subjected to chemical treatment. Differences in the lipidic composition of all chemically treated hairs were found with respect to the untreated ones. Lipid recovery of damaged hair due to the ap- plication of IWL liposomes was corroborated by lipid analysis of the hair. A high resistance to break of hair samples post-treated with IWL liposomes was observed. An increase in hydrogen bonds and electrostatic forces and an improvement in the cohesion between matrix and fi laments were detected, probably because of some lipid recovery. INTRODUCTION Human hair is a keratinized fi ber 50–100 μm in diameter and is divided into three struc- tural zones: medulla, cortex, and cuticle. The medulla, which is located in the central region of the hair, has a diameter of 5–10 μm and is composed of loosely packed cells leaving a series of vacuoles along the fi ber axis. The cortex is made up of crystalline pro- teins (microfi brils) surrounded by a relatively amorphous matrix. The high-sulfur and high-glycine/high-tyrosine proteins are concentrated in the matrix. The microfi brils are relatively rich in low-sulfur proteins (these proteins are rich in amino acids that favor α-helix formation). The outermost layer of the hair is the cuticle, which is generally 5-μm thick. It is made up of nine to ten scales. Each scale has a laminar structure with an outer and inner layer, known as exo- and endocuticle, respectively (1,2). The three differ- ent kinds of cells (medullar, cortical, and cuticular) are separated by the cell membrane Address all correspondence to Meritxell Marti at meritxcell.marti@iqac.csic.es.

JOURNAL OF COSMETIC SCIENCE 566 complex (3). This consists of a protein layer (4,5), termed δ-layer (∼18 nm), which is sur- rounded by two lipid layers (each layer being 3-μm thick) known as β-layers (6). Lipids from human hair consist mainly of cholesterol esters, free fatty acids, cholesterol, ceramides, and cholesterol sulfate. The loss of lipids along the fi ber (7), may be attributed to repeated shampooing, grooming, and UV exposure. In some individuals, chlorine, hair dyes, and hair bleaches may also contribute to the loss of lipids. The loss of these lipids could impair the integrity of the cuticle. This loss of cuticle integrity would increase the susceptibility of the protein and lipid lamellae to degradation, leading to a decrease in the tensile properties of the hair (7). A number of studies suggest that hair lipids can contrib- ute to physicochemical phenomena such as diffusion, cell cohesion, and mechanical strength, despite occurring in a considerably lower proportion than proteins (2,8–10). Wool is another keratinous tissue, whose internal lipids have been extracted and analyzed in different works (11,12). These lipids are rich in cholesterol, free fatty acids, cholesterol sulfate, and ceramides, and they resemble those found in membranes of other keratinous tissues such as human hair or stratum corneum. The application of liposomes made up of internal wool lipids (IWL) on skin has been studied because of the similarity of composi- tion of IWL and SCL (stratum corneum lipids of human skin) and because of their capac- ity to form stable bilayer structures. The benefi cial effect of liposomes with ceramides extracted from wool fi ber on intact skin in aging populations or in individuals with dry skin has been reported (13,14). Accordingly, internal wool lipids could be regarded as a new natural extract suitable for topical application and incorporation into pharmaceutical or cosmetic formulations for skin care (15). The similarity in chemical and morphological structures of wool and hair fi bers prompted us to study the effect of applying IWL on human hair. Natural properties of hair fi ber were restored to a certain degree, especially when IWL structured as liposomes were ap- plied (16). Consequently a new cosmetic application of these lipids on hair and nail repair was envisaged (17). The study seeks to evaluate the effect of IWL liposome application on untreated hair fi - bers and on hair fi bers subjected to chemical treatment. The effect of this lipid supple- mentation on the moisture regulation and mechanical strength of hair fi ber was determined. The lipid absorption was evaluated in order to measure the recovery of these lipids in the treated fi bers. Lipid modifi cations were related to the chemical and me- chanical properties of hair fi ber. MATERIAL AND METHODS CHEMICALS The chemicals used in this study were acetone (Merck, Darmstadt, Germany), formic acid 85% (Probus S.A., Badalona, Barcelona), citric acid monohydrate (Merck, Darmstadt, Germany), chloroform (Merck, Darmstadt, Germany), diethyl ether (Merck, Darmstadt, Germany), hydrogen peroxide 30% (Merck, Schuchardt, Germany), meth- anol (Merck, Darmstadt, Germany), N-hexane (Merck, Darmstadt, Germany), sodium hydroxide (Carlo Erba Reagenti, Rodano), and thioglycolic acid (Merck, Darmstadt, Germany).