SOLUBILIZATION OF LIPOSOMES FORMED BY LIPIDS MODELING THE STRATUM-CORNEUM CAUSED BY ALKYL PYRIDINIUM SURFACTANTS

The interactions of a series of alkyl pyridinium surfactants (alkyl ch ain lengths C-10 (DePB), C-12 (DoPB) and C-14 (TePB)) with liposomes m odeling the stratum corneum (SC) lipid composition (40%, ceramides, 25 % cholesterol, 25% palmitic acid and 10% cholesteryl sulfate) were inv estigated. Tile surfactant:lipid molar ratios (Re) and the bilayer-aqu eous phase partition coefficients (K) were determined by monitoring th e changes in the static light scattering of the system during solubili zation. The fact that the free concentration was always similar to the surfactant critical micelle concentration (CMC) indicates that liposo me solubilization was mainly ruled by formation of mixed micelles. The Re and K values fell as the surfactant alkyl chain length decreased o r their CMC increased. Thus, the higher the surfactant CMC the higher the surfactant ability to saturate or solubilize SC liposomes and the lower its degree of partitioning into liposomes. The balance of these two tendencies shows that the TePB and DoPB had respectively the highe st power of saturation and solubilization of SC structures in terms of total surfactant amounts needed to produce these effects. Different t rends in the interaction of these surfactants with SC liposomes were o bserved when comparing the Re and K values with those reported for PC ones. Thus, whereas SC liposomes were more resistant to the surfactant action, the degree of partitioning of these surfactants into these li posomes was higher in all cases. (C) 1997 Elsevier Science Ireland Ltd .