Size control of surfactant vesicles made by a mixture of cationic surfactants and organic derivatives

Spontaneous size-controllable vesicles that are prepared by a mixture of surfactants with different alkyl chain lengths (n-alkyltrimethylammonium bromide, C_nTAB) and an organic derivative (5-methyl salicylic acid, 5mS) in aqueous solution have been investigated. When the organic derivative 5mS is mixed with the C_nTAB surfactants in aqueous solution, the surfactant vesicles are spontaneously formed above a certain 5mS concentration. Small angle neutron scattering reveals that the core radius of surfactant vesicles is clearly increased from ca. 31 nm to ca. 97 nm with the alkyl chain length of surfactants while the bilayer thickness of the vesicles is nearly constant. The structure of surfactant vesicles maintains against temperature change ranging from 30°C to 45°C, showing no structural change. These results can provide thermally stable surfactant vesicles with various sizes and constant bilayer thickness that may possess a different permeability and may allow the surfactant vesicle to be used in gene or drug delivery for a variety of goods.