Synthetic diether-linked cationic lipids for gene delivery

The discovery and enhanced properties of trichain lipids in lipopolyplex gene delivery systems

Novel trichain lipids have been identified with enhanced transfection properties in lipopolyplexes.

The formation of a novel trichain (TC) lipid was discovered when a cationic lipid possessing a terminal hydroxyl group and the helper lipid dioleoyl l-α-phosphatidylethanolamine (DOPE) were formulated as vesicles and stored. Importantly, the transfection efficacies of lipopolyplexes comprised of the TC lipid, a targeting peptide and DNA (LPDs) were found to be higher than when the corresponding dichain (DC) lipid was used. To explore this interesting discovery and determine if this concept can be more generally applied to improve gene delivery efficiencies, the design and synthesis of a series of novel TC cationic lipids and the corresponding DC lipids was undertaken. Transfection efficacies of the LPDs were found to be higher when using the TC lipids compared to the DC analogues, so experiments were carried out to investigate the reasons for this enhancement. Sizing experiments and transmission electron microscopy indicated that there were no major differences in the size and shape of the LPDs prepared using the TC and DC lipids, while circular dichroism spectroscopy showed that the presence of the third acyl chain did not influence the conformation of the DNA within the LPD. In contrast, small angle neutron scattering studies showed a considerable re-arrangement of lipid conformation upon formulation as LPDs, particularly of the TC lipids, while gel electrophoresis studies revealed that the use of a TC lipid in the LPD formulation resulted in enhanced DNA protection properties. Thus, the major enhancement in transfection performance of these novel TC lipids can be attributed to their ability to protect and subsequently release DNA. Importantly, the TC lipids described here highlight a valuable structural template for the generation of gene delivery vectors, based on the use of lipids with three hydrophobic chains.

Efficient transfection of Xenobiotic Responsive Element-biosensor plasmid using diether lipid and phosphatidylcholine liposomes in differentiated HepaRG cells

In this study, we evaluated cationic liposomes prepared from diether-NH₂ and egg phosphatidylcholine (EPC) for in vitro gene delivery. The impact of the lipid composition, i.e. the EPC and Diether-NH₂ molar ratio, on in vitro transfection efficiency and cytotoxicity was investigated using the human HEK293T and hepatoma HepaRG cells known to be permissive and poorly permissive cells for liposome-mediated gene transfer, respectively. Here, we report that EPC/Diether-NH₂-based liposomes enabled a very efficient transfection with low cytotoxicity compared to commercial transfection reagents in both HEK293T and proliferating progenitor HepaRG cells. Taking advantage of these non-toxic EPC/Diether-NH₂-based liposomes, we developed a method to efficiently transfect differentiated hepatocyte-like HepaRG cells and a biosensor plasmid containing a Xenobiotic Responsive Element and a minimal promoter driving the transcription of the luciferase reporter gene. We demonstrated that the luciferase activity was induced by a canonical inducer of cytochrome P450 genes, the benzo[a]pyrene, and two environmental contaminants, the fluoranthene, a polycyclic aromatic hydrocarbon, and the endosulfan, an organochlorine insecticide, known to induce toxicity and genotoxicity in differentiated HepaRG cells. In conclusion, we established a new efficient lipofection-mediated gene transfer in hepatocyte-like HepaRG cells opening new perspectives in drug evaluation relying on xenobiotic inducible biosensor plasmids.

Synthesis and Characterization of Series of Soft-Template Agents for Mesoporous Materials

Quaternary ammonium surfactants 3a–d, with diether linkages in the backbone between hydrocarbon chains and the ammonium head groups, were synthesized as potential soft-template agents for the preparation of mesoporous materials. Varying the length of their carbon chains was expected to control the pore sizes of the corresponding mesoporous materials prepared. The critical micelle concentration (CMC) and γcmc (surface tension of the CMC) of these surfactants were measured by surface tension method.

Structure-function relationship research of glycerol backbone-based cationic lipids for gene delivery

Transfection activities of two series of synthetic glycerol backbone-based cationic lipids were studied as gene delivery carriers. The variable length of hydrocarbon chains, diverse quaternary ammonium heads, different linkage, as well as alternative anion combined with them allowed to find how these factors affect cationic lipids on their gene delivery performance. The structure-function relationship of the synthetic glycerol backbone-based cationic lipids was discussed, and the transfection efficiency of some of the cationic liposomes was superior or parallel to that of two commercial transfection agents.

Effect of spacer attachment sites and pH-sensitive headgroup expansion on cationic lipid-mediated gene delivery of three novel myristoyl derivatives

The transfection activity and physicochemical properties of the dimyristoyl derivatives from three novel series of double-chained tertiary cationic lipids were compared. Two of the derivatives were constructed as isomers with different linkages of the same bis-(2-dimethylaminoethane) polar headgroup and hydrophobic chains to the diaminopropanol backbone, while the third was designed with a hydrophilic region containing only a single ionizable amine group. Such systematic molecular changes offer a great opportunity to delineate factors critical for transfection activity, which in this work include the intramolecular distance between the hydrophobic chains and pH-expandability of the polar headgroup. The physical studies comprised a variety of techniques, including pKa determination, Langmuir monolayer studies, fluorescence anisotropy, gel electrophoresis mobility shift assay, ethidium bromide displacement assay, particle size distribution, and zeta potential. These studies are crucial in the development of lipid-based gene delivery systems with improved efficacy. Physicochemical characterization revealed that a symmetric bivalent pH-expandable polar headgroup in combination with greater intramolecular space between the hydrophobic chains provide for high transfection activity through efficient binding and compaction of pDNA, increased acyl chain fluidity, and high molecular elasticity.