PREPARATION CONDITIONS AND EVALUATION OF THE STABILITY OF LIPID VESICLES (LIPOSOMES) USING THE MICROENCAPSULATION TECHNIQUE

Abstract

The conditions for the preparation of lipid vesicles ((liposomes) by the in-water drying method, one of the microencapsulation techniques, were described in detail. This process consists of the following steps: (I) dispersion of an aqueous solution of the drug to be encapsulated into an organic solvent to yield a water-in-oil emulsion, (II) dispersion of this w/o-type emulsion into an aqueous phase (distilled water), (III) formation of a lipid membrane on the surface of droplets by evaporation of the organic solvent from the oil phase, and (IV) removal of the free marker (drug) by ultracentrifugation or gel filtration through a Sephadex column. In this process, the mean diameter of the vesicles was dependent on the mechanical revolution number necessary for dispersing the w/o-type emulsion into the distilled water. Moreover, the percentage encapsulation of the lipid vesicles increased with the decrease in mechanical revolution number necessary for dispersing the w/o-type emulsion into the distilled water, and increased with the increase in the mechanical revolution number necessary for preparing the w/o-type emulsion. The resulting lipid vesicles in suspension were found to have excellent stability in comparison with other well-known methods such as vortexing, sonication and reverse phase evaporation. Moreover, the microencapsulation technique, which was simple, rapid and reproducible, was found to be very useful for mass production of lipid vesicles containing various drugs manufactured in the pharmaceutical industry.