ABSTRACT
Nonionic surfactants of a wide variety of structural types have been found to be useful alternatives to phospholipids in the fabrication of vesicular systems. Emulsification was carried out using a vortex mixer to produce the vesicle-in-water-in-oil (v/w/o) emulsion. Although all the v/w/o emulsions had vesicles in the aqueous disperse phase, their size is a reflection of the Span used and the mode of preparation of the vesicles. The effect of the particular Span surfactant on the release of Carboxyfluorescein was investigated by preparing niosomes and their equivalent water-in-oil dispersions using the Span series. The gelation was thought to be the result of the crystallization and solidification of the excess nonionic surfactant in the oil phase, but work has demonstrated surfactant fibril formation as a cause. It was essential to prepare the vesicles at a temperature above the gel-liquid transition temperature of the nonionic surfactants.
