PREPARATION AND PROPERTIES OF NEW UNILAMELLAR NON-IONIC IONIC SURFACTANT VESICLES/

Non-ionic surfactant vesicles (NSVs) were prepared from polysorbate 20 and cholesterol by means of two different methods: by direct sonicati on of an aqueous dispersion of the various components (bulk) or by sol ubilization of the components, evaporation of the organic solvent to f orm a film inside the vessel used for the preparation and then by soni cation (film). The influence of the preparation technique on the prope rties of the obtained structures was studied. Vesicles with bigger dim ensions and higher entrapment efficiency were obtained when sonication was carried out after the film formation. Vesicle formation in the pr esence of ionic surfactants was investigated in order to evaluate the effect of charged components on vesicle dimensions, entrapment efficie ncy and stability. Dimethyldioctadecylammonium bromide (DDOA) and cety lpyridinium chloride (CPy) were used to introduce a positive charge in the vesicle structure, while dicetylphosphate (DCP) was used for a ne gative charge. Better resistance to osmotic stress and higher entrapme nt efficiency values were obtained with vesicles containing DCP and CP y. (C) 1998 Elsevier Science B.V.