Efficient delivery of plasmid DNA using cholesterol-based cationic lipids containing polyamines and ether linkages

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.

Cationic lipids for gene delivery: many players, one goal

Lipid-based carriers represent the most widely used alternative to viral vectors for gene expression and gene silencing purposes. This class of non-viral vectors is particularly attractive for their ease of synthesis and chemical modifications to endow them with desirable properties. Despite combinatorial approaches have led to the generation of a large number of cationic lipids displaying different supramolecular structures and improved behavior, additional effort is needed towards the development of more and more effective cationic lipids for transfection purposes. With this review, we seek to highlight the great progress made in the design of each and every constituent domain of cationic lipids, that is, the chemical structure of the headgroup, linker and hydrophobic moieties, and on the specific effect on the assembly with nucleic acids. Since the complexity of such systems is known to affect their performances, the role of formulation, stability and phase behavior on the transfection efficiency of such assemblies will be thoroughly discussed. Our objective is to provide a conceptual framework for the development of ever more performing lipid gene delivery vectors.

Enhancement of Liposomal Plasmid DNA and siRNA Delivery by Itraconazole through Intracellular Cholesterol Accumulation

PURPOSE

Efficient and safe vehicle that can enhance gene transfer is still needed. Since intracellular cholesterol is known to have an important role in gene delivery and itraconazole alters intracellular cholesterol trafficking, we investigated the effect of itraconazole on pDNA and siRNA delivery.

METHODS

The pDNA and Bcl2 siRNA transfection efficiency was measured by luciferase assay and cytotoxicity. Cellular cholesterol was observed using filipin staining, and intracellular uptake was analyzed by flow cytometry. Lipoplex localization was observed by fluorescent labeling of DNA and lysosome after treatment of itraconazole or co-treatment of itraconazole and bafilomycin A1.

RESULTS

Itraconazole enhanced the transfection efficiency of pDNA and siRNA compared to that of control through the accumulation of cholesterol. Bafilomycin A1 diminished the effect of itraconazole on gene delivery and the increment of cholesterol. Itraconazole did not increase the cellular uptake of lipoplex, but increased free pDNA during the endosome-lysosome pathway was observed during the endosome-lysosome pathway. Treating cells with both imipramine and itraconazole caused an additive effect in pDNA and siRNA delivery.

CONCLUSIONS

Itraconazole enhanced gene delivery of pDNA and siRNA, and it can be used to potentiate nucleic acid therapeutics.

Synthesis and Properties of Low-Molecular-Weight PEI-Based Lipopolymers for Delivery of DNA

Rapid enzymatic degradation and fragmentation during DNA administration can result in limited gene expression, and consequently, poor efficacy. It is necessary to use novel vectors for DNA delivery. Herein, we aimed to design useful carriers for enhancing transfection efficiency (TE). These lipopolymers were prepared through Michael addition reactions from low-molecular-weight (LMW) polyethyleneimine (PEI) and linkers with three kinds of steroids. Agarose gel electrophoresis assay results displayed that the three lipopolymers could condense plasmid DNA well, and the formed polyplexes had appropriate sizes around 200⁻300 nm, and zeta potentials of about +25⁻40 mV. The results of in vitro experiments using HeLa, HEK293, and MCF-7 cells showed that these lipopolymers present higher TE than 25-kDa PEI, both in the absence and presence of 10% serum. Flow cytometry and confocal microscopy studies also demonstrated that these lipopolymer/DNA complexes present higher cellular uptake and intracellular distribution. The measurement of critical micelle concentration (CMC) revealed that these lipopolymers could form micelles, which are suited for drug delivery. All results suggest that the three materials may serve as hopeful candidates for gene and drug delivery in future in vivo applications.

Strategies for the enhanced intracellular delivery of nanomaterials

The intracellular delivery of nanomaterials and drugs has been attracting increasing research interest, mainly because of their important effects and functions in several organelles. Targeting specific organelles can help treat or decrease the symptoms of diabetes, cancer, infectious, and autoimmune diseases. Tuning biological and chemical properties enables the creation of functionalized nanomaterials with enhanced intracellular uptake, ability to escape premature lysosome degradation, and to reach a specific target. Here, we provide an update of recent advances in the intracellular delivery mechanisms that could help drugs reach their target more efficiently.

A comprehensive mathematical model of drug release kinetics from nano-liposomes, derived from optimization studies of cationic PEGylated liposomal doxorubicin formulations for drug-gene delivery

This study focuses on the development of a universal mathematical model for drug release kinetics from liposomes to allow in silico prediction of optimal conditions for fine-tuned controlled drug release. As a prelude for combined siRNA-drug delivery, nanoliposome formulations were optimized using various mole percentages of a cationic lipid (1,2-dioleoyl-3-trimethylammonium-propane, DOTAP) in the presence or absence of 3 mol% distearoyl phosphoethanolamine, polyethylene glycol (PEG-2000mDSPE). Outcome parameters were particle size, zeta potential, entrapment efficiency, in vitro drug release, and tumor cell kill efficiency. The optimized formula (containing 20% DOTAP with 3% DSPE-mPEG(2000) was found to be stable for six months, with round-shaped particles without aggregate formation, an average diameter of 71 nm, a suitable positive charge, and 89% drug encapsulation efficiency (EE). The 41% drug release during 6 h confirmed controlled release. Furthermore, the release profiles as functions of pH and temperature were investigated and the kinetics of the drug release could adequately be fitted to Korsmeyer-Peppas' model by multiple regression analysis. The statistical parameters confirmed good conformity of final models. Functionality of the novel cationic liposome formulations (± DOX) was tested on osteosarcoma (OS) cell lines. Increased OS cell toxicity (1.3-fold) was observed by the DOX-loaded vs. the free DOX. A feasibility pilot showed that siRNA could be loaded efficiently as well. In conclusion, we have established a predictive mathematical model for the fine-tuning of controlled drug release from liposomal formulations, while creating functional drug-delivery liposomes with potential for siRNA co-delivery to increase specificity and efficacy.

IgA response and protection following nasal vaccination of chickens with Newcastle disease virus DNA vaccine nanoencapsulated with Ag@SiO2 hollow nanoparticles

Newcastle disease caused by ND virus (NDV) is a highly contagious disease of birds. Vaccine for effective protection of poultry animals from NDV infection is urgently needed. Mucosal immunity plays a very important role in the antiviral immune response. In this study, a NDV F gene-containing DNA vaccine encapsulated in Ag@SiO2 hollow nanoparticles (pFDNA-Ag@SiO2-NPs) with an average diameter of 500 nm were prepared to assess the mucosal immune response. These nanoparticles exhibited low cytotoxicity and did not destroy the bioactivity of plasmid DNA, which could be expressed in vitro. The plasmid DNA was sustainably released after an initial burst release. In vivo immunization showed that the intranasal immunization of chickens with pFDNA-Ag@SiO2-NPs induced high titers of serum antibody, significantly promoted lymphocyte proliferation and induced higher expression levels of IL-2 and IFN-γ in a dose-dependent manner. These results indicated that the Ag@SiO2 hollow nanoparticles could serve as an efficient and safe delivery carrier for NDV DNA vaccine to induce mucosal immunity. This study has provided promising results for the further development of mucosal vaccines encapsulated in inorganic nanoparticles.

Cholesterol derived cationic lipids as potential non-viral gene delivery vectors and their serum compatibility

Cholesterol derivatives M1-M6 as synthetic cationic lipids were designed and the biological evaluation of the cationic liposomes based on them as non-viral gene delivery vectors were described. Plasmid pEGFP-N1, used as model gene, was transferred into 293T cells by cationic liposomes formed with M1-M6 and transfection efficiency and GFP expression were tested. Cationic liposomes prepared with cationic lipids M1-M6 exhibited good transfection activity, and the transfection activity was parallel (M2 and M4) or superior (M1 and M6) to that of DC-Chol derived from the same backbone. Among them, the transfection efficiency of cationic lipid M6 was parallel to that of the commercially available Lipofectamine2000. The optimal formulation of M1 and M6 were found to be at a mol ratio of 1:0.5 for cationic lipid/DOPE, and at a N/P charge mol ratio of 3:1 for liposome/DNA. Under optimized conditions, the efficiency of M1 and M6 is greater than that of all the tested commercial liposomes DC-Chol and Lipofectamine2000, even in the presence of serum. The results indicated that M1 and M6 exhibited low cytotoxicity, good serum compatibility and efficient transfection performance, having the potential of being excellent non-viral vectors for gene delivery.

Novel cholesterol-based cationic lipids as transfecting agents of DNA for efficient gene delivery

The design, synthesis and biological evaluation of the cationic lipid gene delivery vectors based on cholesterol and natural amino acids lysine or histidine are described. Cationic liposomes composed of the newly synthesized cationic lipids 1a or 1b and neutral lipid DOPE (1,2-dioleoyl-l-α-glycero-3-phosphatidyl-ethanolamine) exhibited good transfection efficiency. pEGFP-N₁ plasmid DNA was transferred into 293T cells by cationic liposomes formed from cationic lipids 1a and 1b, and the transfection activity of the cationic lipids was superior (1a) or parallel (1b) to that of the commercially available 3β-[N-(N',N'-dimethylaminoethyl)-carbamoyl] cholesterol (DC-Chol) derived from the same cholesterol backbone with different head groups. Combined with the results of agarose gel electrophoresis, transfection experiments with various molar ratios of the cationic lipids and DOPE and N/P (+/−) molar charge ratios, a more effective formulation was formed, which could lead to relatively high transfection efficiency. Cationic lipid 1a represents a potential agent for the liposome used in gene delivery due to low cytotoxicity and impressive gene transfection activity.