title: Spontaneous entrapment of polynucleotides upon electrostatic interaction with ethanol-destabilized cationic liposomes.
abstract: This study describes the effect of ethanol and the presence of poly(ethylene) glycol (PEG) lipids on the interaction of nucleotide-based polyelectrolytes with cationic liposomes. It is shown that preformed large unilamellar vesicles (LUVs) containing a cationic lipid and a PEG coating can be induced to entrap polynucleotides such as antisense oligonucleotides and plasmid DNA in the presence of ethanol. The interaction of the cationic liposomes with the polynucleotides leads to the formation of multilamellar liposomes ranging in size from 70 to 120 nm, only slightly bigger than the parent LUVs from which they originated. The degree of lamellarity as well as the size and polydispersity of the liposomes formed increases with increasing polynucleotide-to-lipid ratio. A direct correlation between the entrapment efficiency and the membrane-destabilizing effect of ethanol was observed. Although the morphology of the liposomes is still preserved at the ethanol concentrations used for entrapment (25-40%, v/v), entrapped low-molecular-weight solutes leak rapidly. In addition, lipids can flip-flop across the membrane and exchange rapidly between liposomes. Furthermore, there are indications that the interaction of the polynucleotides with the cationic liposomes in ethanol leads to formation of polynucleotide-cationic lipid domains, which act as adhesion points between liposomes. It is suggested that the spreading of this contact area leads to expulsion of PEG-ceramide and triggers processes that result in the formation of multilamellar systems with internalized polynucleotides. The high entrapment efficiencies achieved at high polyelectrolyte-to-lipid ratios and the small size and neutral character of these novel liposomal systems are of utility for liposomal delivery of macromolecular drugs.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3. nmaurer@interchange.ubc.ca
authors.forename: N
authors.initials: N
authors.lastname: Maurer
authors.forename: K F
authors.initials: KF
authors.lastname: Wong
authors.forename: H
authors.initials: H
authors.lastname: Stark
authors.forename: L
authors.initials: L
authors.lastname: Louie
authors.forename: D
authors.initials: D
authors.lastname: McIntosh
authors.forename: T
authors.initials: T
authors.lastname: Wong
authors.forename: P
authors.initials: P
authors.lastname: Scherrer
authors.forename: S C
authors.initials: SC
authors.lastname: Semple
authors.forename: P R
authors.initials: PR
authors.lastname: Cullis
mesh_terms: D002412:Cations / Q000737:chemistry; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000378:metabolism; D016503:Drug Delivery Systems; D000431:Ethanol / Q000494:pharmacology*; D005614:Freeze Fracturing; D006801:Humans; D008027:Light; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D008954:Models, Biological; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011092:Polyethylene Glycols / Q000737:chemistry; D011119:Polynucleotides / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011721:Pyrenes / Q000737:chemistry; D012542:Scattering, Radiation; D013696:Temperature; D014461:Ultracentrifugation
chemical_list: D002412:Cations; D008055:Lipids; D008081:Liposomes; D016376:Oligonucleotides, Antisense; D011119:Polynucleotides; D011721:Pyrenes; D000431:Ethanol; D011092:Polyethylene Glycols; D004247:DNA; C030984:pyrene