Permeability changes caused by surfactants in liposomes that model the stratum corneum lipid composition

The alterations caused by different surfactants in the permeability of liposomes formed by a lipid mixture that models the stratum corneum (SC) composition (40% ceramides, 25% cholesterol, 25% palmitic acid, and 10% cholesteryl sulfate) were investigated. The surfactant/lipid molar ratios (Re) and the bilayer/aqueous phase surfactant partition coefficients (K) were determined at two sublytic levels. The selected surfactant were sodium dodecyl sulfate (SDS); sodium dodecyl ether sulfate (SDES) to assess the influence of the ethylene oxide groups on the anionic surfactant’s behavior; Triton X‐100 (OP‐10EO) and dodecyl betaine (D‐Bet) as representatives of nonionic and amphoteric surfactants. Permeability alterations were determined by monitoring the increase in the fluorescence intensity of liposomes due to the 5(6) carboxyfluorescein (CF) released from the interior of vesicles. The SC liposomes/surfactant sublytic interactions were mainly ruled by the action of surfactant monomers. OP‐10EO showed the highest ability to alter the permeability of bilayers and the highest affinity with these structures, whereas D‐Bet showed the lowest tendencies. Although SDS and SDES exhibited similar activity at 50% CF release (similar Re values), SDES appeared to be more active at 100% CF release, its affinity with bilayers being also increased. The different ability exhibited by SDS, SDES, and D‐Bet (same alkyl chainlength) to alter the permeability of SC liposomes emphasizes the role played by the polar part of these surfactants in this interaction. Different trends in the evolution of Re and K were observed when comparing the results with those reported for phosphatidylcholine (PC) liposomes. Thus, whereas SC liposomes appeared to be more resistant to the action of surfactants, the surfactant affinity with SC bilayers was always greater than that reported for PC bilayers.