Cationic liposome-mediated gene delivery in vivo

siRNA Design and Delivery Based on Carbon Nanotubes

Owing to the unique physical and chemical properties of carbon nanotubes, they have been widely explored as delivery vectors for proteins, and nucleic acid etc. after functionalization. Particularly, the modification of carbon nanotubes suited for the delivery of siRNA has been intensely studied over the past decade. The assay described in this chapter allows for realizable quantification of siRNA binding on carbon nanotube-based materials using gel electrophoresis and silencing by flow cytometry when the siRNA complexes are delivered in vitro.

Cationic cholesterol derivative efficiently delivers the genes: in silico and in vitro studies

The aims of the research work were to synthesize ethyl(cholesteryl carbamoyl)-L-arginate (ECCA), an arginine-conjugated cholesterol derivative, and to evaluate its application as a gene delivery vector. The interactions of ECCA with DNA duplex were studied using molecular dynamics (MD) simulations. It was found that the guanidine group of ECCA could interact with the phosphate group of DNA through ionic interactions as well as hydrogen bonds. The structure of DNA was stable throughout the simulation time. Liposomes were formulated using ECCA and soya phosphatidylcholine (SPC) by a thin-film hydration method. They had the particle size of ~ 150 nm and the zeta potential of + 51 mV. To ensure the efficient binding of DNA to the liposomes, the ratio of DNA to ECCA was optimized using gel retardation assay. Further, serum stability, haemolysis and cytotoxicity studies were carried out to determine the stability and safety of the lipoplexes. Circular dichroism spectroscopy was used to determine the interaction of DNA and cationic liposomes. Cellular uptake pathway was determined by studying the uptake of coumarin-loaded lipoplexes at 4 °C and in the presence of uptake inhibitors, i.e. genistein, chlorpromazine and methyl-β-cyclodextrin. Transfection studies were carried out to evaluate the transfection efficacy of the ECCA-loaded lipoplexes. The binding of DNA and lipoplexes was found to be stable in the presence of serum, and no degradation of DNA was observed. The lipoplexes showed low haemolysis and cytotoxicity. The uptake of coumarin-loaded liposomes was decreased up to ~ 20% in the presence of clathrin- and caveola-mediated uptake inhibitors, indicating a role of both the pathways in the uptake of the inhibitors. Satisfactory transfection efficiency was obtained compared to Lipofectamine^®. Thus, cationic cholesterol derivative is a useful tool for gene delivery vector.

In vivo single-cell electroporation for transfer of DNA and macromolecules

Single-cell electroporation allows transfection of plasmid DNA or macromolecules into individual living cells using modified patch electrodes and common electrophysiological equipment. This protocol is optimized for rapid in vivo electroporation of Xenopus laevis tadpole brains with DNA, dextrans, morpholinos and combinations thereof. Experienced users can electroporate roughly 40 tadpoles per hour. The technique can be adapted for use with other charged transfer materials and in other systems and tissues where cells can be targeted with a micropipette. Under visual guidance, an electrode filled with transfer material is placed in a cell body-rich area of the tadpole brain and a train of voltage pulses applied, which electroporates a nearby cell. We show examples of successfully electroporated single cells, instances of common problems and troubleshooting suggestions. Single-cell electroporation is an affordable method to fluorescently label and genetically manipulate individual cells. This powerful technique enables observation of single cells in an otherwise normal environment.

Cell Biological and Biophysical Aspects of Lipid-mediated Gene Delivery

Cationic lipids are conceptually and methodologically simple tools to deliver nucleic acids into the cells. Strategies based on cationic lipids are viable alternatives to viral vectors and are becoming increasingly popular owing to their minimal toxicity. The first-generation cationic lipids were built around the quaternary nitrogen primarily for binding and condensing DNA. A large number of lipids with variations in the hydrophobic and hydrophilic region were generated with excellent transfection efficiencies in vitro. These cationic lipids had reduced efficiencies when tested for gene delivery in vivo. Efforts in the last decade delineated the cell biological basis of the cationic lipid gene delivery to a significant detail. The application of techniques such as small angle X-ray spectroscopy (SAXS) and fluorescence microscopy, helped in linking the physical properties of lipid:DNA complex (lipoplex) with its intracellular fate. This biological knowledge has been incorporated in the design of the second-generation cationic lipids. Lipid-peptide conjugates (peptoids) are effective strategies to overcome the various cellular barriers along with the lipoplex formulations methodologies. In this context, cationic lipid-mediated gene delivery is considerably benefited by the methodologies of liposome-mediated drug delivery. Lipid mediated gene delivery has an intrinsic advantage of being a biomimetic platform on which considerable variations could be built to develop efficient in vivo gene delivery protocols.

Full deacylation of polyethylenimine dramatically boosts its gene delivery efficiency and specificity to mouse lung

High-molecular-mass polyethylenimines (PEIs) are widely used vectors for nucleic acid delivery. We found that removal of the residual N-acyl moieties from commercial linear 25-kDa PEI enhanced its plasmid DNA delivery efficiency 21 times in vitro, as well as 10,000 times in mice with a concomitant 1,500-fold enhancement in lung specificity. Several additional linear PEIs were synthesized by acid-catalyzed hydrolysis of poly(2-ethyl-2-oxazoline), yielding the pure polycations. PEI87 and PEI217 exhibited the highest efficiency in vitro: 115-fold and 6-fold above those of the commercial and deacylated PEI25s, respectively; moreover, PEI87 delivered DNA to mouse lung as efficiently as the pure PEI25 but at a lower concentration and with a 200-fold lung specificity. These improvements stem from an increase in the number of protonatable nitrogens, which presumably results in a tighter condensation of plasmid DNA and a better endosomal escape of the PEI/DNA complexes. As a validation of the potential of such linear, fully deacylated PEIs in gene therapy for lung diseases, systemic delivery in mice of the complexes of a short interfering RNA (siRNA) against a model gene, firefly luciferase, and PEI25 or PEI87 afforded a 77% and 93% suppression of the gene expression in the lungs, respectively. Furthermore, a polyplex of a siRNA against the influenza viral nucleocapsid protein gene and PEI87 resulted in a 94% drop of virus titers in the lungs of influenza-infected animals.