Sublytic alterations caused by alkyl glucosides in stratum corneum lipid liposomes

The sublytic interactions of a series of alkyl glucosides (alkyl chain lengths ranging from C8 to C12) with liposomes formed by a mixture of lipids modeling the stratum corneum (SC) lipid composition were investigated. The surfactant to lipid molar ratios (Re) and the normalized bilayer/aqueous phase partition coefficients (K) 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 to the bulk aqueous phase. Given that the free surfactant concentrations were always lower than their critical micelle concentrations (CMC) we may assume that the surfactant–liposome interactions were mainly ruled by the action of surfactant monomers. At the two interaction levels studied (50 and 100% CF release) the nonyl and the octyl glucoside showed respectively the highest ability to alter the liposome permeability (lowest Re values), whereas the dodecyl glucoside showed the highest degree of partitioning into liposomes or affinity with these structures (highest K values). Different trends in the interaction of these surfactants with SC and PC liposomes were detected when comparing the present Re and K values with those reported for PC vesicles. Thus, whereas SC lipid liposomes were more resistant to the action of alkyl glucosides (higher Re values), the degree of partitioning of these surfactants into SC bilayers was always greater than that exhibited for PC vesicles (higher K values).