Abstract: Liposomal formulations having extended circulation time in vivo and increased drug retention are comprised of sphingomyelin and cholesterol and have an acidic intraliposomal pH. The formulations have enhanced stability and thus are used in methods which provide improved drug delivery and more effective treatment. The delivery of ciprofloxacin, and alkaloid drugs, particularly swainsonine, vincristine and vinblastine, is significantly improved.

Abstract: Methods for encapsulating ionizable antineoplastic agents in liposomes using transmembrane potentials are provided. Trapping efficiencies approaching 100% and rapid loading are readily achieved. Dehydration protocols which allow liposomes to be conveniently used in the administration of antineoplastic agents in a clinical setting are also provided. In accordance with other aspects of the invention, transmembrane potentials are used to reduce the rate of release of ionizable drugs from liposomes.

Abstract: Novel, hydrophobic lipid-nucleic acid complexes. The complexes are charge-neutralized and contain the nucleic acid in a non-condensed form. Manipulation of these complexes in either detergent-based or organic solvent-based systems leads to particle formation. Thus, the present invention also provides methods of preparing lipid-nucleic acid particles which are useful for the therapeutic delivery of nucleic acids. The particles are constructed via hydrophobic lipid-nucleic acid intermediates (or complexes). Upon removal of a solubilizing component (i.e., detergent or an organic solvent) the nucleic acid forms a particle with lipids and is protected from degradation. The particles thus formed are suitable for use in intravenous nucleic acid transfer as they are stable in circulation, of a size required for pharmacodynamic behavior resulting in access to extravascular sites and target cell populations.

Abstract: A method for encapsulation of antineoplastic agents in liposomes is provided, having preferably a high drug:lipid ratio. Liposomes may be made by a process that loads the drug by an active mechanism using a transmembrane ion gradient, preferably a transmembrane pH gradient. Using this technique, trapping efficiencies approach 100%, and liposomes may be loaded with drug immediately prior to use, eliminating stability problems related to drug retention in the liposomes. Drug:lipid ratios employed are about 3-80 fold higher than for traditional liposome preparations, and the release rate of the drug from the liposomes is reduced. An assay method to determine free antineoplastic agents in a liposome preparation is also disclosed.

Abstract: Liposomal compositions encapsulating bioactive agents and having improved circulation longevity of the agents are disclosed. Such liposomes combine a low pH of the solution in which a bioactive agent is entrapped and a sugar-modified lipid or an amine-bearing lipid, the combination of which enhances the retention of the encapsulated bioactive agent and thereby promotes circulation longevity. The present invention also discloses methods of making and using such compositions.

Abstract: Dehydrated liposomes are prepared by drying liposome preparations under reduced pressure in the presence of one or more protective sugars, e.g., the disaccharides trehalose and sucrose. Preferably, the protective sugars are present at both the inside and outside surfaces of the liposome membranes. Freezing of the liposome preparation prior to dehydration is optional. Alternatively, the protective sugar can be omitted if: (1) the liposomes are of the type which have multiple lipid layers; (2) the dehydration is done without prior freezing; and (3) the dehydration is performed to an end point which results in sufficient water being left in the preparation (e.g., at least 12 moles water/mole lipid) so that the integrity of a substantial portion of the multiple lipid layers is retained upon rehydration.

Abstract: Liposomal formulations having extended circulation time in vivo and increased drug retention are comprised of sphingomyelin and cholesterol and have an acidic intraliposomal pH. The formulations have enhanced stability and thus are used in methods which provide improved drug delivery and more effective treatment. The delivery of lipophilic drugs such as the vinca alkaloids, and particularly vincristine and vinblastine, to tumors is significantly improved.

Abstract: Microemulsion compositions for the delivery of hydrophobic compounds are provided. Such compositions have a variety of uses. In one embodiment, the hydrophobic compounds are therapeutic agents including drugs. The present invention also discloses methods for in vitro and in vivo delivery of hydrophobic compounds to cells. Uses of the methods in vitro include the testing of hydrophobic compounds for cytotoxicity. Uses of the methods in vivo include diagnostic and therapeutic purposes.

Abstract: Aminoglycosides, analogs and derivatives thereof, in the form of phosphate salts are described as well as the process for making and utilizing same. Aminoglycoside phosphate liposomes and nonguanadino aminoglycoside phosphate liposomes, their preparation and use, are particularly described.

Abstract: This invention relates to a method for synthesizing a substantially pure reactive lipid including, for example, N-[4-(p-maleimidophenyl)-butyryl]phosphatidylethanolamine (MPB-PE) and related compositions. The compositions of the present invention are useful as coupling agents and may be incorporated into liposomes and subsequently coupled to proteins, cofactors and a number of other molecules. A preferred coupling method is also disclosed as are protein conjugates.

Abstract: The present invention describes a composition consisting of liposomes covalently or non-covalently coupled to the glycoprotein streptavidin. The streptavidin may additionally be coupled to biotinated proteins such as Immunoglobulin G or monoclonal antibodies.The liposomes of the invention may have a transmembrane potential across their membranes, and may be dehydrated. In addition, the composition may contain ionizable bioactive agents such as antineoplastic agents, and may be used in diagnostic assays.

Abstract: Methods for encapsulating ionizable antineoplastic agents in liposomes using transmembrane potentials are provided. Trapping efficiencies approaching 100% and rapid loading are readily achieved. Dehydration protocols which allow liposomes to be conveniently used in the administration of antineoplastic agents in a clinical setting are also provided. In accordance with other aspects of the invention, transmembrane potentials are used to reduce the rate of release of ionizable drugs from liposomes.

Abstract: The present invention relates to a general method for producing sized protein-liposome conjugates exhibiting enhanced blood circulation times. The present invention also relates to the sized protein-liposome conjugate compositions produced by the method of the present invention. The protein-liposome conjugates of the present invention preferably range in size from about 75 nm to about 200 nm.The liposomes of the invention may have a transmembrane potential across their membranes, and may be dehydrated. In addition, the composition may contain ionizable bioactive agents such as antineplastic agents, and may be used in diagnostic assays.

Abstract: The present invention describes a composition consisting of liposomes covalently or non-covalently coupled to the glycoprotein streptavidin. The streptavidin may additionally be coupled to biotinated proteins such as Immunoglobulin G or monoclonal antibodies. The liposomes of the invention may have a transmembrane potential across their membranes, and may be dehydrated. In addition, the composition may contain ionizable bioactive agents such as antineoplastic agents, and may be used in diagnostic assays.This is a divisional application of copending application Ser. No. 941,913, filed Dec. 15, 1986, which is now U.S. Pat. No. 4,885,172, which is a continuation-in-part of copending application Ser. No. 811,037, which in turn is a continuation-in-part of copending application Ser. No. 749,161, filed June 26, 1985, both now abandoned and copending application Ser. No. 759,419, filed July 26, 1985 now U.S. Pat. No. 4,870,635.

Abstract: A method for reducing the lamellarity of a population of liposomes is provided which comprises repeatedly passing the liposomes under pressure through a filter which has a pore size equal to or less than about 100 nm. In certain embodiments, the method is used to convert a population of previously formed multilamellar liposomes into a population of substantially unilamellar liposomes. In accordance with other aspects of the disclosure, liposomes are prepared directly from a lipid powder or pellet and buffer without the use of any solvents, detergents or other extraneous materials.

Abstract: A multilamellar vesicle dispersed in an aqueous phase comprising an aqueous medium, a lipid concentration of at least about 50 mg/ml and a trapping efficiency of at least about 40 percent. The vesicle can be prepared by dispersing the lipid in an aqueous phase to form a multilamellar vesicle, rapidly freezing the multilamellar vesicle to obtain a frozen lipid-aqueous medium mixture, and warming the mixture to obtain a frozen and thawed multilamellar vesicle dispersed in an aqueous phase.

Abstract: The present invention describes a composition consisting of liposomes covalently or non-covalently coupled to the glycoprotein streptavidin. The streptavidin may additionally be coupled to biotinated proteins such as Immunoglobulin G or monoclonal antibodies.The liposomes of the invention may have a transmembrane potential across their membranes, and may be dehydrated. In addition, the composition may contain ionizable bioactive agents such as antineoplastic agents, and may be used in diagnostic assays.

Abstract: Dehydrated liposomes are prepared by drying liposome preparations under reduced pressure in the presence of one or more protective sugars, e.g., the disaccharides trehalose and sucrose. Preferably, the protective sugars are present at both the inside and outside surfaces of the liposome membranes. Freezing of the liposome preparation prior to dehydration is optional. Alternatively, the protective sugar can be omitted if: (1) the liposomes are of the type which have multiple lipid layers; (2) the dehydration is done without prior freezing; and (3) the dehydration is performed to an end point which results in sufficient water being left in the preparation (e.g., at least 12 moles water/mole lipid) so that the integrity of a substantial portion of the multiple lipid layers is retained upon rehydration.