title: Effect of the preparation procedure on the structural properties of oligonucleotide/cationic liposome complexes (lipoplexes) studied by electron spin resonance and Zeta potential.
abstract: Lipoplexes with different surface charge were prepared from a short oligonucleotide (20 mer, dsAT) inserted into liposomes of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 1,2-dioleoyl-sn-glycero-3-phospho-ethanolamine (DOPE). The starting liposomes were prepared by two different procedures, i.e. progressive dsAT addition starting from plain liposomes (titration) and direct mixing of dsAT with pure liposomes (point to point preparation). Lipoplexes were characterized from a molecular point of view by Electron Spin Resonance (ESR) of a cationic spin probe and by Nuclear Magnetic Resonance. Structural and surface features were analysed by Zeta potential (zeta) measurements and Cryo-TEM micrographs. The complete set of results allowed to demonstrate that: i) the interactions between dsAT and cationic lipids were strong and occurred at the liposome surface; ii) the overall shape and physicochemical properties of liposomes did not change when short nucleic acid fragments were added before surface charge neutralization; iii) the bilayer structure of the lipids in lipoplexes was substantially preserved at all charge ratios; iv) the physical status of lipoplexes with electrical charge far from neutrality did not depend on the preparation method.
authors.affiliation: Department of Chemistry & CSGI, University of Florence, Via della Lastruccia 3, 50019 Sesto F no, Firenze, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Ciani
authors.forename: Sandra
authors.initials: S
authors.lastname: Ristori
authors.forename: Claudia
authors.initials: C
authors.lastname: Bonechi
authors.forename: Claudio
authors.initials: C
authors.lastname: Rossi
authors.forename: Giacomo
authors.initials: G
authors.lastname: Martini
mesh_terms: D000225:Adenine / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D020285:Cryoelectron Microscopy; D004578:Electron Spin Resonance Spectroscopy; D005229:Fatty Acids, Monounsaturated / Q000737:chemistry; D008081:Liposomes / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008564:Membrane Potentials; D015394:Molecular Structure; D009841:Oligonucleotides / Q000737:chemistry*; D010714:Phosphatidylethanolamines / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013499:Surface Properties; D013941:Thymine / Q000737:chemistry
chemical_list: C410262:1,2-dioleoyl-glycero-3-phosphatidyl ethanolamine; D002412:Cations; D005229:Fatty Acids, Monounsaturated; D008081:Liposomes; D009841:Oligonucleotides; D010714:Phosphatidylethanolamines; D000644:Quaternary Ammonium Compounds; D000225:Adenine; C070046:1,2-dioleoyloxy-3-(trimethylammonium)propane; D013941:Thymine