Cationic amphiphiles of both lipid and nonlipid nature in gene therapy

Lipophilic Polyamines as Promising Components of Liposomal Gene Delivery Systems

Gene therapy requires an effective and safe delivery vehicle for nucleic acids. In the case of non-viral vehicles, including cationic liposomes, the structure of compounds composing them determines the efficiency a lot. Currently, cationic amphiphiles are the most frequently used compounds in liposomal formulations. In their structure, which is a combination of hydrophobic and cationic domains and includes spacer groups, each component contributes to the resulting delivery efficiency. This review focuses on polycationic and disulfide amphiphiles as prospective cationic amphiphiles for gene therapy and includes a discussion of the mutual influence of structural components.

Malonic acid based cationic lipids - The way to highly efficient DNA-carriers

Cationic lipids play an important role as non-viral nucleic acid carriers in gene therapy since 3 decades. This review will introduce malonic acid derived cationic lipids as nucleic acid carriers which appeared in the literature dealing with lipofection 10years ago. The family of amino-functionalized branched fatty acid amides will be presented as well as different generations of malonic acid diamides. Both groups of cationic lipids yield lipid mixtures with highly efficient nucleic acid transfer activities in in-vitro cell culture models. The DNA transfer screening of lipid libraries with directed structural variations in the lipophilic as well as in the hydrophilic part of the amphiphiles yields structure/activity relationships. Furthermore, the detailed characterizations of selected lipid composites at the air/water interface and in bulk systems are summarized with regard to transfection determining physical-chemical properties. The findings are also discussed in comparison to results obtained with other families of cationic lipids.

Structure-transfection activity relationships in a series of novel cationic lipids with heterocyclic head-groups

Cationic liposomes are promising candidates for the delivery of various therapeutic nucleic acids. Here, we report a convenient synthesis of carbamate-type cationic lipids with various hydrophobic domains (tetradecanol, dialkylglycerol, cholesterol) and positively charged head-groups (pyridinium, N-methylimidazolium, N-methylmorpholinium) and data on the structure-transfection activity relationships. It was found that single-chain lipids possess high surface activity, which correlates with high cytotoxicity due to their ability to disrupt the cellular membrane by combined hydrophobic and electrostatic interactions. Liposomes containing these lipids also display high cytotoxicity with respect to all cell lines. Irrespective of chemical structures, all cationic lipids form liposomes with similar sizes and surface potentials. The characteristics of complexes composed of cationic liposomes and nucleic acids depend mostly on the type of nucleic acid and P/N ratios. In the case of oligodeoxyribonucleotide delivery, the transfection activity depends on the type of cationic head-group regardless of the type of hydrophobic domain: all types of cationic liposomes mediate efficient oligonucleotide transfer into 80-90% of the eukaryotic cells, and liposomes based on lipids with N-methylmorpholinium cationic head-group display the highest transfection activity. In the case of plasmid DNA and siRNA, the type of hydrophobic domain determines the transfection activity: liposomes composed of cholesterol-based lipids were the most efficient in DNA transfer, while liposomes containing glycerol-based lipids exhibited reasonable activity in siRNA delivery under serum-free conditions.

Synthesis, characterization and comparative evaluation of phenoxy ring containing long chain gemini imidazolium and pyridinium amphiphiles

Two series of phenoxy ring containing long chain imidazolium and pyridinium based gemini amphiphiles have been synthesized from renewable cardanol oil having different spacers (i. e. -S-(CH(2))(n)-S-, where n is 2, 3, 4 & 6). Critical micelle concentration (cmc) of these new gemini amphiphiles has been determined by conductivity method. Further, these new cationic amphiphiles have been evaluated for their DNA binding capability by agarose gel electrophoresis, ethidium bromide exclusion experiments and transmission electron microscopy (TEM). The cytotoxicity of these new amphiphiles have been evaluated by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Comparative studies of these phenoxy ring containing long chain gemini imidazolium amphiphiles and their pyridinium analogues depicted low cmc values of the later but greater DNA interaction capability and low cytotoxicity of the former series of amphiphiles.

Novel cholesterol-based cationic lipids for gene delivery

Gene therapy based on gene delivery is a promising strategy for the treatment of human disease. Here we present data on structure/biological activity of new biodegradable cholesterol-based cationic lipids with various heterocyclic cationic head groups and linker types. Enhanced accumulation of nucleic acids in the cells mediated by the lipids was demonstrated by fluorescent microscopy and flow cytometry. Light scattering and atomic force microscopy were used to find structure/transfection activity correlations for the lipids. We found that the ability of the lipids to stimulate intracellular accumulation of the oligodeoxyribonucleotides and plasmid DNA correlates well with their ability to form in solution lipid/NA complexes of sizes that do not exceed 100 nm. Screening of the lipids revealed the most promising transfection agents both in terms of low toxicity and efficient delivery: cholesterol-based lipids with positively charged pyridine and methyl imidazole head groups and either the ester or carbamate linker.

Sunfish Cationic Amphiphiles: Toward an Adaptative Lipoplex Morphology

A detailed physicochemical study is presented on a new class of cationic amphiphiles, Sunfish amphiphiles, recently designed, synthesized, and tested for gene delivery. These materials have two hydrophobic tails, connected to the cationic pyridinium headgroup at the 1- and 4-positions. Two extreme morphologies can be visualized, i.e. one by back-folding involving association of both tails at one side of the pyridinium ring and one by independent unfolding of the tails, the two molecular geometries leading to considerable differences in the aggregate morphology. The behavior of six members of the Sunfish family in mixtures with DOPE, applying different conditions relevant for transfection, has been studied by a combination of techniques (DLS, DSC, NMR, SAXS, Cryo-TEM, fluorescence, etc.). The effects of structural parameters such as the presence of unsaturation in the tails and length of the alkyl chains on the properties of the aggregates have been assessed. A correlation of these structural data with cellular transfection efficiencies reveals that the highest transfection efficiency is obtained with those amphiphiles that are easily hydrated, form fluid aggregates, and undergo a transition to the inverted hexagonal phase in the presence of plasmid DNA (p-DNA) at physiological ionic strength.