Different stratum corneum lipid liposomes as models to evaluate the effect of the sodium dodecyl sulfate

The stability of stratum corneum (SC) liposomes against the action of surfactants has been revised. To this end, two types of vesicles were used; vesicles formed with the lipid and protein material extracted from SC, and lipid mixtures approximating the SC composition. In this case, the proportion of ceramides (Cer) and cholesteryl sulfate (Chol-sulf) was varied and the relative proportion of the other lipids remained constant. The increasing presence of these two lipids increased the resistance of liposomes against the action of the anionic surfactant sodium dodecyl sulfate (SDS). The rise in the cell-to-cell cohesion that occurred in recessive X-linked ichthyosis due to the accumulation of Chol-sulf could be associated in part to the enhanced stability of (Chol-sulf)-enriched bilayers. It is noteworthy that the surfactant partitioning between bilayers and the aqueous phase increased and decreased, respectively, as the proportion of Cer and Chol-sulf increased. This effect may be attributed to the variations in both the electrostatic interactions lipid-surfactant (electrostatic repulsion between the sulfate groups of both Chol-sulf and SDS), and the hydrophilic lipophilic balance of the lipid mixtures, in which Cer is replaced by the major polar lipid of the mixture (Chol-sulf). The fact that the free surfactant concentration was always smaller than its critical micelle concentration indicates that the permeability alterations were mainly ruled by the action of surfactant monomers, in agreement with the results reported for sublytic interactions of this surfactant with PC liposomes.