Fused liposome and acid induced method for liposome fusion
First Claim
1. A method of fusing liposomes which comprises:
- (a) preparing a suspension of liposomes containing at least one lipid which has a tendency to form the inverted hexagonal phase and at least 20 mol percent of one or more amphipathic molecules containing one or more weakly acidic functional groups selected from the group consisting of C12 to C30 fatty acids and palmitoyl homocysteine; and
(b) in the absence of externally added divalent cations, proteins or other macromolecules, acidifying the liposome suspension to reduce the pH of these liposomes to below pH 7, whereby at least about 20% of said liposomes fuse to one another.
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Abstract
Liposomes containing phosphatidylethanolamine, palmitoyl homocysteine or oleic acid or palmitic acid, fuse rapidly when the pH of the medium is reduced below 7. Liposome fusion was measured by (a) mixing of the liposomal lipids as shown by resonance energy transfer, (b) gel filtration and (c) electron microscopy. The presence of phosphatidylethanolamine or acid addition esters thereof in the liposomes greatly enhances fusion; whereas the presence of phosphatidylcholine inhibits fusion. During fusion of liposomes containing phosphatidylethanolamine:palmitoyl homocysteine (8:2), almost all of the encapsulated calcein is released. Inclusion of cholesterol (40%) in the liposomes substantially decreases leakage without impairing fusion. Those pH sensitive liposomes are fused to deliver biologically active molecules such as DNA, into living cells.
26 Citations
20 Claims
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1. A method of fusing liposomes which comprises:
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(a) preparing a suspension of liposomes containing at least one lipid which has a tendency to form the inverted hexagonal phase and at least 20 mol percent of one or more amphipathic molecules containing one or more weakly acidic functional groups selected from the group consisting of C12 to C30 fatty acids and palmitoyl homocysteine; and (b) in the absence of externally added divalent cations, proteins or other macromolecules, acidifying the liposome suspension to reduce the pH of these liposomes to below pH 7, whereby at least about 20% of said liposomes fuse to one another. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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- 15. Fused nonagglomerated liposomes comprised of at least one lipid which has a tendency to form the inverted hexagonal phase and at least 20 mol percent of an amphipathic molecule containing one or more acidic functional groups an amphipathic molecule selected from palmitoylhomocysteine, palmitic acid and oleic acid. PG,30
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19. Fused liposomes containing phosphatidylethanolamine and oleic acid in a mol ratio of 8:
- 2.
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20. Fused liposomes containing phosphatidylethanolamine and palmitic acid in a mol ratio of 8:
- 2.
Specification