Molecular Dynamics Study of Cationic Vesicle Bilayers Composed of Ion Pair Amphiphiles with Double-Tailed Cationic Surfactants

An-Tsung Kuo, Chien-Hsiang Chang, Wataru Shinoda

Langmuir, 28, 8156-8164(2012).DOI: 10.1021/la300651u

The physical stability of catanionic vesicles is important for the development of novel drug or DNA carriers. For investigating the mechanism by which catanionic vesicles are stabilized, molecular dynamics (MD) simulation is an attractive approach that provides microscopic structural information on the vesicular bilayer. In this study, MD simulation was applied to investigate the bilayer properties of catanionic vesicles composed of an ion pair amphiphile (IPA), hexadecyltrimethylammonium- dodecylsulfate (HTMA-DS), and a double-tailed cationic surfactant, ditetradecyl-dimethylammonium chloride (DTDAC). Structural information regarding membrane elasticity and the organization and conformation of surfactant molecules was obtained based on the resulting trajectory. Simulation results showed that a proper amount of DTDAC could be used to complement the asymmetric structure between the HTMA-DS molecules, resulting in an ordered hydrocarbon chain packing within the rigid membrane observed in the mixed HTMA-DS/DTDAC system. The coexistence of gel and fluid phases was also observed in the presence of excess DTDAC. MD simulation results agreed well with results obtained from experimental studies examining mixed HTMA-DS/DTDAB vesicles.