Solubilization of stratum corneum lipid liposomes by Triton X-100. Influence of the level of cholesteryl sulfate in the process

The interaction of Triton X-100 (TX-100) with stratum corneum (SC) lipid liposomes varying the proportion of cholesteryl sulfate (Chol-sulf) was investigated. The surfactant/lipid molar ratios (Re) and the bilayer/aqueous phase surfactant partition coefficients (K) were determined by monitoring the changes in the static light scattering of the system during solubilization. The fact that the free surfactant concentration was always similar to its critical micelle concentration (CMC) indicates that the liposome solubilization was mainly ruled by the formation of mixed micelles. The TX-100 ability to saturate and to solubilize SC liposomes decreased as the proportion of Chol-sulf in bilayers increased until a minimum was reached for a Chol-sulf proportion of 10%. Inversely, the surfactant partitioning into liposomes (or affinity with these bilayers) increased as the proportion of Chol-sulf increased until a maximum was reached at the same Chol-sulf proportion. Hence, when the Chol-sulf proportion in bilayers was 10% (the same that existing in the intercellular SC lipids) the ability of TX-100 molecules to interact with liposomes exhibits a minimum despite their enhanced partitioning into liposomes. These effects may be related to the reported dependencies between the level of Chol-sulf in the intercellular lipids and the abnormalities in the skin properties as the barrier function.