title: DOTAP/DOPE and DC-Chol/DOPE lipoplexes for gene delivery: zeta potential measurements and electron spin resonance spectra.
abstract: Non-viral vectors represent an important alternative in gene delivery. Among these vectors, cationic liposomes are widely studied, because of their ability to form stable complexes with DNA fragments (lipoplexes). In the present work, we report on the characterization by electron spin resonance (ESR) spectroscopy and zeta potential measurements of cationic liposomes and of their complexes with oligonucleotides. Liposomes were made with a zwitterionic lipid, DOPE, and a cationic lipid, either DOTAP or DC-Chol. Oligonucleotides were the 20-base single strand polyA, the 20-base single strand polyT, and the corresponding double strand dsAT. The zeta potential as a function of the oligonucleotide/lipid+ ratio gave an S-shaped titration curve. Well-defined surface potential changes took place upon charge compensation between the cationic lipid heads and the phosphate groups on the oligonucleotides. The inversion point depended on the specific system under study. The bilayer properties and the changes that occurred with the incorporation of DNA fragments were also monitored by ESR spectroscopy of appropriately tailored spin probes. For all the systems investigated, the ESR spectra showed that no major alteration took place after lipoplex formation and molecular packing remained substantially unchanged. Both zeta potential and ESR measurements were in favor of an external mode of packing of the lipoplexes.
authors.affiliation: Department of Chemistry, University of Florence, Polo Scientifico, Via della Lastruccia, 3 50019 Sesto F. no, Florence, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Ciani
authors.forename: Sandra
authors.initials: S
authors.lastname: Ristori
authors.forename: Anna
authors.initials: A
authors.lastname: Salvati
authors.forename: Luca
authors.initials: L
authors.lastname: Calamai
authors.forename: Giacomo
authors.initials: G
authors.lastname: Martini
mesh_terms: D002412:Cations; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology*; D005456:Fluorescent Dyes / Q000494:pharmacology; D018014:Gene Transfer Techniques; D008055:Lipids / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008280:Magnetics; D008956:Models, Chemical; D009841:Oligonucleotides / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000494:pharmacology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D013696:Temperature
chemical_list: C410262:1,2-dioleoyl-glycero-3-phosphatidyl ethanolamine; D002412:Cations; D005229:Fatty Acids, Monounsaturated; D005456:Fluorescent Dyes; D008055:Lipids; D008081:Liposomes; D009841:Oligonucleotides; D010714:Phosphatidylethanolamines; D000644:Quaternary Ammonium Compounds; C070648:3-(N-(N',N'-dimethylaminoethane)carbamoyl)cholesterol; D002784:Cholesterol; C070046:1,2-dioleoyloxy-3-(trimethylammonium)propane