Sublytic alterations caused by alkyl glucosides in stratum corneum lipid liposomes

The sublytic interactions of a series of alkyl glucosides (alkyl chain leng ths ranging from C-8 to C-12) with liposomes formed by a mixture of lipids modeling the stratum corneum (SC) lipid composition were investigated. The surfactant to lipid molar ratios (R-e) and the normalized bilayer/aqueous p hase partition coefficients (K) were determined by monitoring the increase in the fluorescence intensity of liposomes due to the 5(6)-carboxyfluoresce in (CF) released from the interior of vesicles to the bulk aqueous phase. G iven that the free surfactant concentrations were always lower than their c ritical micelle concentrations (CMC) we may assume that the surfactant-lipo some interactions were mainly ruled by the action of surfactant monomers. A t the two interaction levels studied (50 and 100% CF release) the nonyl and the octyl glucoside showed respectively the highest ability to alter the l iposome permeability (lowest R-e values), whereas the dodecyl glucoside sho wed the highest degree of partitioning into liposomes or affinity with thes e structures (highest K values). Different trends in the interaction of the se surfactants with SC and PC liposomes were detected when comparing the pr esent R-e and K values with those reported for PC vesicles. Thus, whereas S C lipid liposomes were more resistant to the action of alkyl glucosides (hi gher R-e values), the degree of partitioning of these surfactants into SC b ilayers was always greater than that exhibited for PC vesicles (higher K va lues). (C) 2001 Elsevier Science B.V. All rights reserved.