Influence of the level of cholesteryl sulfate in the solubilization of stratum corneum lipid liposomes by sodium dodecyl sulfate

The role played by cholesteryl sulfate (Chol-sulf) in the solubilization of liposomes modeling the stratum corneum (SC) lipids by sodium dodecyl sulfa te (SDS) was studied. We determined the surfactant-to-lipid molar ratios an d the bilayer/aqueous phase surfactant partition coefficients of this inter action by varying the proportion of Chol-sulf, the relative proportions of the others lipids remaining constant. These parameters were determined by m onitoring the changes in the static light scattering of the system during s olubilization. The fact that the free surfactant concentration was always s imilar to its critical micelle concentration indicates that the liposome so lubilization was mainly ruled by the formation of mixed micelles. The SDS a bility to saturate and solubilize SC liposomes decreased as the proportion of Chol-sulf in the bilayers increased until a minimum was reached for a Ch ol-sulf proportion of about 15%. Inversely, the SDS partitioning into lipos omes (or affinity with these bilayers) increased as the proportion of Chol- sulf increased until a maximum was reached at similar Chol-sulf proportions (10-15%). Hence, in these Chol-sulf proportions (similar to that existing in the intercellular lipids. which was 10%) the ability of SDS molecules to interact with liposomes exhibits a minimum despite their enhanced partitio ning into liposomes. These effects may be related to the reported dependenc ies of the level of Chol-sulf on the abnormalities in the skin barrier func tion and on the SC intercellular cohesion.