Solubilizing interactions of octylphenol surfactants with liposomes modeling the stratum corneum lipid composition

The interaction of a series of polyethoxylated octylphenols (ethylene oxide units average 8.5–20.0) with liposomes modeling the stratum corneum (SC) lipid composition (40% ceramides, 25% cholesterol, 25% palmitic acid and 10% of cholesteryl sulfate) was investigated. The surfactant/lipid molar ratios (Re) and the bilayer/aqueous-phase partition coefficients (X) were determined by monitoring the changes in the static light scattering of the system during solubilization. The fact that free concentration for each surfactant tested was always similar to its critical micelle concentration (CMC) indicates that the liposome solubilization was mainly ruled by the formation of mixed micelles. The Re and K parameters for liposome saturation fell as the surfactant HLB increased. Thus, at this interaction step the higher the surfactant HLB, the higher the ability of these surfactants to saturate SC liposomes and the lower their degree of partitioning into liposomes.