Solubilization of liposomes formed by lipids modeling the stratum corneum caused by alkyl pyridinium surfactants

Abstract

The interactions of a series of alkyl pyridinium surfactants (alkyl chain lengths C-10 (DePB), C-12 (DoPB) and C-14 (TePB)) with liposomes modeling the stratum corneum (SC) lipid 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 partition coefficients ( K) were determined by monitoring the changes in the static light scattering of the system during solubilization. The fact that the free concentration was always similar to the surfactant critical micelle concentration (CMC) indicates that liposome solubilization was mainly ruled by formation of mixed micelles. The Re and K values fell as the surfactant alkyl chain length decreased or 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 highest power of saturation and solubilization of SC structures in terms of total surfactant amounts needed to produce these effects. Different trends in the interaction of these surfactants with SC liposomes were observed 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 liposomes was higher in all cases.