ABSTRACT
A panel of lipidic tetraalkylammonium chlorides has been prepared and screened in studies of both lipid hydration and in vivo mouse transfection. The effect of cationic lipid structure on liposome surface hydration was determined using differential scanning calorimetry. Increases in headgroup steric bulk and the inclusion of cis-unsaturation in the hydrophobic domain led to greater lipid hydration, indicative of a decrease in lipid polar domain associations. Cationic lipids containing hydrogen-bonding functionality in the polar domain exhibited a corresponding decrease in observed lipid hydration, indicative of an increase in lipid polar domain associations. To explore a potential correlation of the hydration data with transfection activity, we examined the in vivo transfection activity of the lipid panel by direct intratracheal instillation of cationic liposome-DNA complexes into BALB/c mice. The more active transfection agents were the lipids that featured headgroup structures promoting close polar domain association in combination with fatty acyl cis-unsaturation. The hydration data suggest that the more effective transfection lipids for mouse lung delivery are those possessing the greatest imbalance between the cross-sectional areas occupied by the polar and hydrophobic domains.
Subject(s)
Lipids/administration & dosage , Lung/metabolism , Transfection , Animals , Mice , Plasmids , TransgenesABSTRACT
Cationic lipids (cytofectins) have gained widespread acceptance as pharmaceutical polynucleotide delivery agents for both cultured cell and in vivo transfection, and the cytofectins DOTAP and DC-Cholesterol are being tested in clinical human gene therapy trials. This study reports the effects of modifications in the hydrophobic domain of a prototypic cytofectin (DORI), including modifications in lipid side-chain length, saturation, and symmetry. A panel of related compounds was prepared and analyzed using DNA transfection, electron microscopy, and differential scanning calorimetry (DSC). Lipid formulations were prepared with dioleoylphosphatidylethanolamine (DOPE) as unsonicated preparations and sonicated preparations. Transfection analyses were performed using cultured fibroblasts, human bronchial epithelial, and Chinese hamster ovarian cells as well as a mouse model for pulmonary gene delivery. In general, cytofectins containing dissymmetric hydrophobic domains were found to work as well or better than the best symmetric analogs. Optimal side-chain length and symmetry varied with cell type. Compounds with phase transitions (Tc) above and below physiological temperature (37 degrees C) were tested for DNA transfection activity. In contrast to previous reports, cytofectin Tc was not found to be predictive of transfection efficacy. Pulmonary treatment with free DNA was found to be at least as effective as treatment with commonly used cytofectin:DNA complexes. However, cytofectins that incorporate a hydroxyethylammonium moiety in the polar domain were found to enhance in vivo gene delivery relative to free DNA.
Subject(s)
DNA/administration & dosage , Lipids/administration & dosage , Phosphatidylethanolamines/chemistry , Transfection/methods , 3T3 Cells , Animals , CHO Cells , Calorimetry, Differential Scanning , Cations/chemistry , Cell Line , Cells, Cultured , Cricetinae , Drug Carriers , Fatty Acids, Monounsaturated/chemistry , Female , Humans , Lipids/chemical synthesis , Lipids/chemistry , Liposomes , Mice , Mice, Inbred BALB C , Quaternary Ammonium Compounds/chemistryABSTRACT
Cationic liposome transfection reagents are useful for transferring polynucleotides into cells, and have been proposed for human pulmonary gene therapy. The effect of adding cholesterol to cationic lipid preparations has been tested by first formulating the cationic lipid N-[1-(2,3-dioleoyloxy)propyl-N-[1-(2-hydroxy)ethyl]-N,N-dimethyl ammonium iodide (DORI) with varying amounts of dioleoylphosphatidylethanolamine (DOPE) and cholesterol. Cholesterol was found to enhance lipid-mediated transfection in both the respiratory epithelial cells and mouse fibroblasts. These findings will facilitate nucleic acid transfection of many cell types including differentiated epithelial cell monolayers, and therefore may be useful for examining gene regulation in various cell types and for developing pulmonary gene therapy.
