Spontaneous vesicle formation in catanionic mixtures of amino acid-based surfactants: chain length symmetry effects |
| |
Authors: | Marques Eduardo F Brito Rodrigo O Silva Sandra G Rodríguez-Borges J Enrique do Vale Maria Luísa Gomes Paula Araújo Maria J Söderman Olle |
| |
Institution: | Centro de Investiga??o em Química, Department of Chemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, no. 687, P 4169-007 Porto, Portugal. efmarque@fc.up.pt |
| |
Abstract: | The use of amino acids for the synthesis of novel surfactants with vesicle-forming properties potentially enhances the biocompatibility levels needed for a viable alternative to conventional lipid vesicles. In this work, the formation and characterization of catanionic vesicles by newly synthesized lysine- and serine-derived surfactants have been investigated by means of phase behavior mapping and PFG-NMR diffusometry and cryo-TEM methods. The lysine-derived surfactants are double-chained anionic molecules bearing a pseudogemini configuration, whereas the serine-derived amphiphile is cationic and single-chained. Vesicles form in the cationic-rich side for narrow mixing ratios of the two amphiphiles. Two pairs of systems were studied: one symmetric with equal chain lengths, 2C12/C12, and the other highly asymmetric with 2C8/C16 chains, where the serine-based surfactant has the longest chain. Different mechanisms of the vesicle-to-micelle transition were found, depending on symmetry: the 2C12/C12 system entails limited micellar growth and intermediate phase separation, whereas the 2C8/C16 system shows a continuous transition involving large wormlike micelles. The results are interpreted on the basis of currently available models for the micelle-vesicle transitions and the stabilization of catanionic vesicles (energy of curvature vs mixing entropy). |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|