Spontaneous Vesicle Formation in Catanionic Mixtures of Amino Acid-Based Surfactants: Chain Length Symmetry Effects.

Summary, in English

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, 2C 12/C 12, and the other highly asymmetric with 2C 8/C 16 chains, where the serine-based surfactant has the longest chain. Different mechanisms of the vesicle-to-micelle transition were found, depending on symmetry: the 2C 12/C 12 system entails limited micellar growth and intermediate phase separation, whereas the 2C 8/C 16 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).

• Author: Eduardo Marques; Rodrigo de Oliveira Brito; Sandra Silva; J Rodríguez-Borges; Maria Vale; Paula Gomes; Maria Araújo; Olle Söderman
• Department/s: Physical Chemistry
• Publishing year: 2008
• Language: English
• Pages: 11009-11017
• Publication/Series: Langmuir
• Volume: 24
• Issue: 19
• Links: http://dx.doi.org/10.1021/la801518h
• Document type: Journal article
• Publisher: The American Chemical Society (ACS)
• Topic: Physical Chemistry
• Status: Published
• ISBN/ISSN/Other: ISSN: 0743-7463