Reverse phase evaporation method This method
provided a progress in liposome technology, since it
allowed for the first time the preparation of liposomes
with a high aqueous space-to-lipid ratio and a capability
to entrap a large percentage of the aqueous material
presented. Reverse-phase evaporation is based on the
creation of inverted micelles. These inverted micelles are
shaped upon sonication of a mixture of a buffered aqueous
phase, which contains the water-soluble molecules
to be encapsulated into the liposomes and an organic
phase in which the amphiphilic molecules are
solubilized. The slow elimination of the organic solvent
leads to the conversion of these inverted micelles into
viscous state and gel form. At a critical point in this
process, the gel state collapses, and some of the inverted
micelles were disturbed. The excess of phospholipids in
the environment donates to the formation of a complete
bilayer around the residual micelles, which results in the
creation of liposomes. Liposomes made by reverse phase
evaporation method can be made from numerous lipid
formulations and have aqueous volume-to-lipid ratios
that are four times higher than hand-shaken liposomes
or multilamellar liposomes [19,20].