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Structure et physicochimie des tensioactifs, leurs impacts sur la toxicité cutanée et la fonction barrière

Abstract : Creams, shampoos, soaps, shower gels, these cosmetics daily used, have in common the presence of a raw material essential to their formulation, namely the surfactant or emulsifier. These molecules are therefore frequently in contact with the skin. Indeed, because of its particular amphiphilic structure, the surfactant helps the stabilization of emulsions, allows the formation of foam and provides the detergent properties of cleansing cosmetic products, by solubilizing the fatty substances present on the surface. These molecules can also interact with the components of the skin. One of the first obvious evidence of the interaction of surfactants with the skin is the observation of clinical signs following prolonged or chronic exposure to surfactant-rich formulas. These molecules are now known to cause irritant contact dermatitis and are the subject of a real public health problem regarding professional detergent diseases. However, considering the multitude of surfactants on the market, the mechanisms of action of surfactants on the skin are still poorly known, especially for nonionic surfactants, widely used in skincare products and often considered non-toxic. Sodium lauryl sulfate, anionic surfactant remains to this day, the model molecule currently studied. The cutaneous toxicity is most often related to the interaction of the surfactant with the proteins, charged molecules. As a result, ionic surfactants are considered to be the most toxic to the skin. In addition, the monomeric form of the surfactant is described as the entity responsible for cutaneous toxicity, fitting more easily into the lipid bilayer and thus able to penetrate the skin more easily than in the form of micelles. The toxicity of the surfactant is therefore also related to its critical micelle concentration. . The objective of this research project was to expand knowledge on different physicochemical properties of many classes of surfactants, to better understand their interactions and their effects on the skin. Several levels of studies have been developed. After detailed physicochemical analysis of the surfactants, in vitro measurements were used to evaluate the effect of the surfactant on skin toxicity. The study on the skin barrier function (surface properties / detergency, lipid matrix organization and evaluation of lipid extraction) was conducted via ex vivo experiments. Our studies have shown significant toxicity of some nonionic surfactants and conversely some ionic surfactants have been found to be perfectly well tolerated. Parameters highlighted in the literature such as CMC and surfactant charges have been questioned. Several explanations were put forward considering the organization of the surfactant in the water and its behavior on the skin barrier function thus bringing new tracks for a better understanding of the effect of the surfactant on the skin. In addition, the toxicity of the surfactants could be related to one of the three levels of disruption of the cutaneous barrier: the disorganization of the lipid matrix
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Submitted on : Wednesday, November 27, 2019 - 11:27:30 AM
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Emmanuelle Lemery. Structure et physicochimie des tensioactifs, leurs impacts sur la toxicité cutanée et la fonction barrière. Dermatologie. Université Claude Bernard - Lyon I, 2015. Français. ⟨NNT : 2015LYO10044⟩. ⟨tel-02382545⟩

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