Stable reversed vesicles in oil: characterization studies and encapsulation of model compounds

The formation of reversed sucrose ester vesicles in silicon oil and mixtures of silicon oil and isopropyl palmitate was studied. The vesicles were characterized by polarized light microscopy, freeze-fracture electron microscopy, and differential scanning calorimetry. Furthermore the ability to encapsulate p-aminobenzoic acid and cholesterol in such vesicles was studied. The vesicles were multilamellar and had sizes up to several micrometers. The vesicles agglomerated but did not show fusion for at least 2 years when stored at room temperature in glass vials. The encapsulation efficiency of both p-aminobenzoic acid and cholesterol strongly depended on the oil phase in which the vesicles were prepared. Reversed sucrose ester vesicles in silicon oil encapsulated nearly 100% of the amount of p-aminobenzoic acid or cholesterol present in the dispersion. These compounds were encapsulated in different compartments of the vesicles. Reversed sucrose ester vesicles offer new perspectives regarding the development of novel pharmaceutical dosage forms.