2019 Volume 19 Issue 1 Pages 13-20
Unilamelar vesicles in water spontaneously adsorb onto solid surfaces, sometimes rupturing and fusing to form a supported bilayer film. Although the general understanding of this process of interest and the driving force has been discussed, it has not been clarified due to the technical difficul ty. Recently, we succeeded to observe the dynamic bilayer formation behavior of dioctadecyldimethyl ammonium bromide (DODAB) vesicles, whose gel-liquid crystal transition temperature (Tc ) is 44°C, at the mica–water interface by high-speed atomic force microscopy (AFM) at 25°C. The vesicles instantaneously changed into the bilayer domains on solid surface and they rarely fused each other. Finally, the homogeneous bilayer film was not formed on mica surface. Another cationic surfactant (D18EAC) vesicle, which has the higher Tc, formed the tetralayer domain on mica surface on the way to bilayer transition. The much higher aggregation ability between the hydrophobic alkyl chains of D18EAC might make the motion of molecules slow. Therefore, it was clarified that the states of hydrated solid unilamellar shell of vesicles should affect the dynamic process of solid-supported bilayer formation.
