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.