Mechanism of mixed liposome solubilization in the presence of sodium dodecyl sulfate

Structural transformations of vesicles to micelles that take place during the interaction of sodium dodecyl sulfate (SOS) with individual and mixed vesicles of phosphatidyl choline (PC) and phosphatidic acid (FA), have been studied by monitoring changes in optical density and in the concentration of free SOS monomer in the respective systems. Incorporation of the surfactant monomers (SOS) in the bilayers was found to result in an initial increase in concentration of the mixed vesicles up to its saturation. Subsequently a progressive relaxation of these structures together with a simultaneous fonnation of mixed micelles was found to occur. The breakup of bilayer and the fonnation of mixed micelles were completely dependent on the structure of the individual phospholipid. The solubilization of the anionic phosphatidic acid vesicle was very fast in the presence of SOS, due to its simple structure and its compatibility with the SOS molecule. But solubilization of the zwitter ionic phosphatidyl choline vesicle was very complicated in the presence of SOS, possibly due to its complex structure and the zwitterionic nature. On the other hand, solubilization of the mixed vesicle (mixed liposome) and fonnation of mixed micelle was found to be relatively easier. This may be attributed to one of the phospholipid component preferentially coming out first through interaction with SOS, thereby making the overall system unstable and enhancing the micellization processes. 0 200 I Elsevier Science B. V. All rights reserved. studying solubilization of cell membranes [47] and surfactants interactions with such biosystems as skin. The interaction of surfactants with liposomes eventually leads to the rupture of its vesicle structure resulting in the solubilization of phospholipid components. In general, there is agreement that growth of vesicles occurs in the initial stages, followed by the formation of a number'of complex lipid-surfactant aggregates associated with the vesicle to micelle transformations. The interactions of sodium dodecyl sulfate (SDS) with