Liposomes in double-emulsion globules.

Tubular liposomes containing a hydrophilic model compound (fluorescein sodium salt, FSS) were entrapped inside the internal aqueous phase (W1) of water-in-oil-in-water (W1/O/W2) double-emulsion globules. Our hypothesis was that the oil membrane of double emulsions can function as a layer of protection to liposomes and their contents and thus better control their release. Liposomes were prepared in bulk, and their release was observed microscopically from individual double-emulsion globules. The liposomes containing FSS were released through external coalescence, and the behavior of this system was monitored visually by capillary video microscopy. Double-emulsion globules were stabilized with Tween 80 as the water-soluble surfactant, with Span 80 as the oil-soluble surfactant, while the oil phase (O) was n-hexadecane. The lipids in the tubular liposomes consist of l-α-phosphatidylcholine and Ceramide-VI. Variations of Tween 80 concentration in the external aqueous phase (W2) and Span 80 concentration in th...