SUBSOLUBILIZING EFFECTS OF ALKYL SULFATES ON LIPOSOMES MODELING THE STRATUM-CORNEUM LIPID-COMPOSITION

The subsolubilizing interactions of three alkyl sulfates (chain length s C-10, C-12, and C-14), with liposomes modeling the stratum corneum l ipid composition, were investigated. Liposomes were formed from a lipi d mixture containing by weight 40% ceramides, 25% cholesterol, 25% pal mitic acid and 10% cholesteryl sulfate. The surfactant/lipid molar rat ios (Re) and the bilayer/aqueous phase partition coefficients (K) were determined by monitoring the increase in the fluorescence intensity o f liposomes due to the 5(6)-carboxyfluorescein (CF) released form the interior of vesicles. The free surfactant concentration was always low er than the critical micelle concentration. At the two interaction lev els studied (50% and 100% CF release) the tetradecyl sulfate showed th e highest ability to release the CF trapped in the liposomes (lowest R e values) and the highest degree of partitioning into the bilayers (hi ghest K values). Whereas stratum corneum liposomes were more resistant to the action of alkyl sulfates than were phosphatidylcholine (PC) li posomes, the degree of partitioning of these surfactants into stratum corneum bilayers was always greater than that reported for PC ones.