The influence of the incorporation of cholesterol and water on the particle size, bilayer thickness, melting behavior, and relative sucrose ester composition of reversed vesicles

The influence of the incorporation of cholesterol and water on the particle size, bilayer thickness, melting behavior, and relative sucrose eater comp osition of reversed vesicles was studied. Reversed vesicles (RVs) were prep ared of sucrose eater in silicon oil by sonication. The RVs were characteri zed by polarized light microscopy, laser diffraction, high-performance liqu id chromatography, small angle X-ray scattering (SAXS), and differential sc anning calorimetry. The particle size distributions of the studied dispersi ons were bimodal with peaks at 5 and 0.4 mum, There was no significant diff erence in the sucrose eater composition of these two size categories of RVs . The incorporation of cholesterol and water had no effect on the size dist ribution of the RVs. The SAXS results showed that the RVs prepared without cholesterol and water consisted of bilayers with fully interdigitated alkyl chains. The incorporation of high concentrations of cholesterol caused a p hase separation within the bilayers. The incorporation of water also result ed in a phase separation within the bilayers but at a lower cholesterol con centration. The presence of two different size classes of RVs in one RVs di spersion and the phase separation within the bilayers of certain compositio ns can have consequences for the application of RVs. (C) 2001 Wiley-Liss, I nc. and the American Pharmaceutical Association J Pharm Sci 90:588-598, 200 1.