Tunable pH-sensitive liposomes composed of mixtures of cationic and anionic lipids.

The pH-dependent fusion properties of large unilamellar vesicles (LUVs) composed of binary mixtures of anionic and cationic lipids have been investigated. It is shown that stable LUVs can be prepared from the ionizable anionic lipid cholesteryl hemisuccinate (CHEMS) and the permanently charged cationic lipid N,N-dioleoyl-N, N-dimethylammonium chloride (DODAC) at neutral pH values and that these LUVs undergo fusion as the pH is reduced. The critical pH at which fusion was observed (pH(f)) was dependent on the cationic lipid-to-anionic lipid ratio. LUVs prepared from DODAC/CHEMS mixtures at molar ratios of 0 to 0.85 resulted in vesicles with pH(f) values that ranged from pH 4.0 to 6.7, respectively. This behavior is consistent with a model in which fusion occurs at pH values such that the DODAC/CHEMS LUV surface charge is zero. Related behavior was observed for LUVs composed of the ionizable cationic lipid 3alpha-[N-(N',N'-dimethylaminoethane)-carbamoyl] cholesterol hydrochloride (DC-Chol) and the acidic lipid dioleoylphosphatidic acid (DOPA). Freeze-fracture and (31)P NMR evidence is presented which indicates that pH-dependent fusion results from a preference of mixtures of cationic and anionic lipid for "inverted" nonbilayer lipid phases under conditions where the surface charge is zero. It is concluded that tunable pH-sensitive LUVs composed of cationic and anionic lipids may be of utility for drug delivery applications. It is also suggested that the ability of cationic lipids to adopt inverted nonbilayer structures in combination with anionic lipids may be related to the ability of cationic lipids to facilitate the intracellular delivery of macromolecules.

[1]  S. Gruner,et al.  Cation-dependent segregation phenomena and phase behavior in model membrane systems containing phosphatidylserine: influence of cholesterol and acyl chain composition. , 1984, Biochemistry.

[2]  D. Thompson,et al.  TRIGGERED RELEASE FROM LIPOSOMES MEDIATED BY PHYSICALLY AND CHEMICALLY INDUCED PHASE TRANSITIONS , 1996 .

[3]  S. Gruner,et al.  Characterization of cholesterol hemisuccinate and α-tocopherol hemisucccinate vesicles , 1988 .

[4]  D. Siegel The modified stalk mechanism of lamellar/inverted phase transitions and its implications for membrane fusion. , 1999, Biophysical journal.

[5]  D. Loose-Mitchell Antisense nucleic acids as a potential class of pharmaceutical agents. , 1988, Trends in pharmacological sciences.

[6]  R. Rand,et al.  Cardiolipin forms hexagonal structures with divalent cations. , 1972, Biochimica et biophysica acta.

[7]  F. Szoka,et al.  Mechanism of DNA release from cationic liposome/DNA complexes used in cell transfection. , 1996, Biochemistry.

[8]  M. Yatvin,et al.  pH-sensitive liposomes: possible clinical implications. , 1980, Science.

[9]  J. Northrop,et al.  Lipofection: a highly efficient, lipid-mediated DNA-transfection procedure. , 1987, Proceedings of the National Academy of Sciences of the United States of America.

[10]  L. Mayer,et al.  Vesicles of variable sizes produced by a rapid extrusion procedure. , 1986, Biochimica et biophysica acta.

[11]  R. Straubinger pH-sensitive liposomes for delivery of macromolecules into cytoplasm of cultured cells. , 1993, Methods in enzymology.

[12]  B. Tycko,et al.  Rapid acidification of endocytic vesicles containing α 2-macroglobulin , 1982, Cell.

[13]  Jizomoto Hiroaki,et al.  pH-Sensitive liposomes composed of tocopherol hemisuccinate and of phosphatidylethanolamine including tocopherol hemisuccinate , 1994 .

[14]  F. Szoka,et al.  Acid- and calcium-induced structural changes in phosphatidylethanolamine membranes stabilized by cholesteryl hemisuccinate. , 1985, Biochemistry.

[15]  Lipid polymorphism and the functional roles of lipids in biological membranes. , 1979 .

[16]  L. Huang,et al.  pH-sensitive liposomes: acid-induced liposome fusion. , 1984, Proceedings of the National Academy of Sciences of the United States of America.

[17]  I. Hafez,et al.  Cholesteryl hemisuccinate exhibits pH sensitive polymorphic phase behavior. , 2000, Biochimica et biophysica acta.

[18]  B. de Kruijff,et al.  The lipidic particle as an intermediate structure in membrane fusion processes and bilayer to hexagonal HII transitions. , 1980, Biochimica et Biophysica Acta.

[19]  J. Zasadzinski,et al.  Spontaneous vesicle formation in aqueous mixtures of single-tailed surfactants. , 1989, Science.

[20]  F. Maxfield,et al.  Immunoliposomes with different acid sensitivities as probes for the cellular endocytic pathway. , 1989, Biochimica et Biophysica Acta.

[21]  P. Cullis,et al.  Freeze-fracture of lipids and model membrane systems. , 1989, Journal of electron microscopy technique.

[22]  B. de Kruijff,et al.  The polymorphic phase behaviour of phosphatidylethanolamines of natural and synthetic origin. A 31P NMR study. , 1978, Biochimica et biophysica acta.

[23]  P. Cullis,et al.  Structural and fusogenic properties of cationic liposomes in the presence of plasmid DNA. , 1997, Biophysical journal.

[24]  P. Cullis,et al.  Ca2+ and pH induced fusion of small unilamellar vesicles consisting of phosphatidylethanolamine and negatively charged phospholipids: a freeze fracture study. , 1983, Biochemical and biophysical research communications.

[25]  D. Hoekstra,et al.  Use of resonance energy transfer to monitor membrane fusion. , 1981, Biochemistry.

[26]  F. Szoka,et al.  Effects of replacement of the hydroxyl group of cholesterol and tocopherol on the thermotropic behavior of phospholipid membranes. , 1985, Biochemistry.

[27]  S. Gruner,et al.  Lipid polymorphism: the molecular basis of nonbilayer phases. , 1985, Annual review of biophysics and biophysical chemistry.

[28]  J. Zimmerberg,et al.  Bending membranes to the task: structural intermediates in bilayer fusion. , 1995, Current opinion in structural biology.

[29]  F. Szoka,et al.  Mechanism of oligonucleotide release from cationic liposomes. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[30]  E. Dufourc,et al.  Effects of pH and cholesterol on DMPA membranes: a solid state 2H- and 31P-NMR study. , 1995, Biophysical journal.

[31]  L. J. Lis,et al.  Membrane fusion and inverted phases. , 1989, Biochemistry.

[32]  Y. Barenholz,et al.  Electrostatic parameters of cationic liposomes commonly used for gene delivery as determined by 4-heptadecyl-7-hydroxycoumarin. , 1997, Biochimica et biophysica acta.

[33]  J. Teissié,et al.  Ionization of phospholipids and phospholipid-supported interfacial lateral diffusion of protons in membrane model systems. , 1990, Biochimica et biophysica acta.

[34]  Gulik-Krzywicki,et al.  Self-assembly of flat nanodiscs in salt-free catanionic surfactant solutions , 1999, Science.

[35]  F. Ledley Nonviral gene therapy: the promise of genes as pharmaceutical products. , 1995, Human gene therapy.

[36]  A. Verkleij,et al.  Polymorphic phase behaviour of cardiolipin as detected by 31P NMR and freeze-fracture techniques. Effects of calcium, dibucaine and chlorpromazine. , 1978, Biochimica et biophysica acta.

[37]  I. Tannock,et al.  Acid pH in tumors and its potential for therapeutic exploitation. , 1989, Cancer research.

[38]  F. Szoka,et al.  pH-induced destabilization of phosphatidylethanolamine-containing liposomes: role of bilayer contact. , 1984, Biochemistry.