Method of preparing giant size liposomes

Claim 1

An improvement in the method of treating aqueous dispersions of small unilamellar vesicles (SUV) to obtain vesicles of enlarged size, said SUV having been prepared by hydration of a bilayer-forming lipid, and thereafter subjecting said aqueous dispersion to at least one cycle of freezing and thawing, wherein the improvement comprises: (a) having present in said SUV dispersion prior to said freeze-thaw cycle at least a 0.1 molar concentration of a crystallizable polar compound plus any additional substance desired to be entrapped in large vestices; (b) then subjecting the dispersion to repeated freeze-thaw cycles in which the temperature reduction in the freezing step is sufficient to crystallize substantially all of the water, said freeze-thaw cycles being repeated until the resulting vesicles are in a generally aggregated form and contain entrapped solution of increased polar compound concentration as well as other substances desired to be entrapped; and then (c) dialyzing the resulting vesicles against an aqueous hypoosmotic medium causing the vesicles to imbibe water, said dialysis being continued until said aggregated vesicles imbibe sufficient water to reform into enlarged unilamellar vesicles.

Claim 12

The method of treating aqueous dispersions of small unilamellar vesicles to obtain vesicles of enlarged size, said vesicles having been prepared by hydration of a bilayer-forming phospholipid, the phospholipid content of said dispersion on a water-lipid basis being at least 1% by weight, comprising dissolving in said dispersion a water-soluble polar compound to a concentration of at least 0.1 molar, subjecting to the polar compound-containing dispersion to repeated freeze-thaw cycles until the resulting vesicles are in a generally aggregated form and contain entrapped solution of increased polar compound concentration, and then dialyzing the resulting vesicles against an aqueous hypoosmotic medium causing the vesicles to imbibe water, said dialysis being continued until said aggregated vesicles have imbibed sufficient water to reform into enlarged unilamellar vesicles.

Claim 13

The method of treating aqueous dispersions of small unilamellar vesicles to obtain vesicles of enlarged size, said vesicles having been prepared by hydration of a bilayer-forming phospholipid, the phospholipid content of said dispersion on a water-lipid basis being at least 1% by weight, comprising dissolving in said dispersion a water-soluble polar compound to a concentration of at least 0.1 molar, subjecting to the polar compound-containing dispersion to repeated freeze-thaw cycles until the resulting vesicles are in a generally aggregated form and contain entrapped solution of increased polar compound concentration, and then dialyzing the resulting vesicles against an aqueous hypoosmotic medium causing the vesicles to imbibe water, said dialysis being continued until said aggregated vesicles have imbibed sufficient water to reform into enlarged unilamellar vesicles.