Preparation of lipid vesicles on the basis of a technique for providing W/O/W emulsions

Abstract

As one of the applications of a technique for providing W/O/W-type multiple-phase emulsions, an attempt was made to prepare an aqueous suspension of lipid vesicles as a model for one-lamellar liposomes. The procedure tested was divided into four operations; (1) preparation of a water-in- n-hexane emulsion stabilized by a mixture of soy lecithin and Span-80; (2) removal of n-hexane from the emulsion under reduced pressure, thus obtaining a water-in-lipid mixture system; (3) mixing of the above system with an aqueous solution of hydrophilic emulsifying agent so as to prepare an aqueous suspension of lipid vesicles composed of aqueous compartments 1–2 μm in diameter, surrounded by the lipid layer; and (4) dialysis of the lipid vesicle suspension against distilled water to remove the residue of the hydrophilic emulsifying agent from the aqueous suspending medium. The results obtained suggest that the necessary weight fraction of soy lecithin to Span-80 in the lipid mixture for attaining 90% or higher yields of the lipid vesicles ranges from 0.35 to 0.65 and that a relatively low concentration of the hydrophilic emulsifying agent is recommended to provide the lipid vesicle suspension in a stable form.