Controlling the size of vesicles prepared from egg lecithin using a hydrotrope

Phase diagrams were constructed using egg lecithin as a source of lipid, so dium xylenesulfonate as the hydrotrope, and various aqueous media. The resu lted oil-in-water microemulsion (L-1) region was utilized to prepare unilam ellar vesicles by diluting the microemulsion with equal amount of the aqueo us media. When the ratio of lecithin/SXS was adjusted in the original micel lar solution the average size of the corresponding vesicles that formed upo n dilution of the L-1 phase changed accordingly. An increase in the ratio o f lecithin/SXS resulted in a linear increase of average vesicle size, rangi ng from 75 to 500 nm. This correlation can be explained with the predictabl e chance in the curvature of a vesicle when sufficient amount of hydrotrope was incorporated. The slope of this linear relationship is influenced by t he polarity of the medium and the presence of molecules that can intercalat e into the lipid bilayer. (C) 2000 Elsevier Science Ltd. All rights reserve d.