External lipid function in ethnic hairs.

OBJECTIVE: The main aim of this study is to characterize the external lipids of different ethnic hairs and to study the contribution of the exogenous lipids on their physicochemical properties. METHODS: On the extraction procedure, sebaceous lipids from the exterior of the fiber are removed. The influence of those free lipids on the hair properties, such as contact angle, mechanical characteristics, and sorption of water, will be evaluated to determine permeation characteristics of the keratin fibers. Relationship with lipid order was also determined by infrared spectroscopy (IR). RESULTS: Lipid extraction indicates the greatest amount of total lipids for African hair. Caucasian lipid extracts present the higher melting point and phase transition temperatures. This could be related to higher hydration and lower diffusion coefficient of the Caucasian fibers. A decrease in moisture was found in the lipid-extracted fibers. This diminution of the maximum water regain in all cases could be due to a higher water desorption. IR results indicate that Caucasian and moreover African native fibers present the most quantity of lipids, and the similar frequency of all fibers indicates a lamellar/orthorhombic order arrangement. CONCLUSION: The hexane/tert-butanol extraction was demonstrated to modify not only cuticular but also cortex lipids. Exogenous lipid depletion in all fibers indicates a less water content and higher water desorption. However, lipid depleted Caucasian fibers presents an increase in the lipid order which could be related to the different saturation of the lipid extract and its improvement in breaking tenacity.

Damaged hair retrieval with ceramide-rich liposomes.

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 impair 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 fibers. This study seeks to apply IWL liposomes to untreated hair fibers and to hair fibers 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 application 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 filaments were detected, probably because of some lipid recovery.

Adsolubilisation of organic compounds onto collagen fibres.

Adsolubilisation has been defined as the incorporation to solid-water interfaces of molecules that do not adsorb spontaneously to such interfaces, but can be incorporated through an interaction with an adsorbing surfactant molecule. The aim of this work was to study the adsolubilisation of organic molecules with different hydrophobicity on collagen fibres. Hide powder collagen was treated under mild acidic aqueous conditions with an anionic surfactant, sodium dodecylbenzene sulphonate. Thereafter, five different organic molecules, i.e., benzyl alcohol, 2-naphtol, pararosaniline, hexamethylpararosaniline and nonylphenol with 10 mol ethylene oxide were separately applied to the treated collagen in order to study adsolubilisation as a function of their hydrophobicity. It was found that under acidic conditions all molecules were scarcely adsorbed or not adsorbed by the native hide powder collagen. However, all organic molecules, except benzyl alcohol, were adsolubilised if the hide powder collagen was previously treated with the anionic surfactant. The hydrophobicity of the molecules plays an important role in the adsolubilisation phenomenon with the result that the higher the hydrophobicity (nonylphenol with 10 mol ethylene oxide), the higher the adsolubilisation.