At present, gene transfection insufficient efficiency is a major drawback of non-viral gene therapy. The 2 main types of delivery systems deployed in gene therapy are based on viral or non-viral gene carriers. Several non-viral modalities can transfer foreign genetic material into the human body. To do so, polycation-based gene delivery methods must achieve sufficient efficiency in the transportation of therapeutic genes across various extracellular and intracellular barriers. These barriers include interactions with blood components, vascular endothelial cells and uptake by the reticuloendothelial system. Furthermore, the degradation of therapeutic DNA by serum nucleases is a potential obstacle for functional delivery to target cells. Cationic polymers constitute one of the most promising approaches to the use of viral vectors for gene therapy. A better understanding of the mechanisms by which DNA can escape from endosomes and traffic to enter the nucleus has triggered new strategies of synthesis and has revitalized research into new polycation-based systems. The objective of this review is to address the state of the art in gene therapy with synthetic and natural polycations and the latest advances to improve gene transfer efficiency in cells

Currently, the major drawback of gene therapy is the gene transfection rate. The two main types of vectors that are used in gene therapy are based on viral or non-viral gene delivery systems. There are several non-viral systems that can be used to transfer foreign genetic material into the human body. In order to do so, the DNA to be transferred must escape the processes that affect the disposition of macromolecules. These processes include the interaction with blood components, vascular endothelial cells and uptake by the reticuloendothelial system. Furthermore, the degradation of therapeutic DNA by serum nucleases is also a potential obstacle for functional delivery to the target cell. Cationic polymers have a great potential for DNA complexation and may be useful as non-viral vectors for gene therapy applications. The objective of this review was to address the state of the art in gene therapy using synthetic and natural polycations and the latest strategies to improve the efficiency of gene transfer into the cell.

Background: Tumor necrosis factor-alpha (TNFα), a pro-inflammatory cytokine, has been shown to play a role in the pathophysiology of rheumatoid arthritis. Silencing TNFα expression with small interfering RNA (siRNA) is a promising approach to treatment of the condition. Methods: Towards this end, our team has developed a modified chitosan (CH) nanocarrier, deploying folic acid, diethylethylamine (DEAE) and polyethylene glycol (PEG) (folate-PEG-CH-DEAE₁₅). The gene carrier protects siRNA against nuclease destruction, its ligands facilitate siRNA uptake via cell surface receptors, and it provides improved solubility at neutral pH with transport of its load into target cells. In the present study, nanoparticles were prepared with siRNA-TNFα, DEAE, and folic acid-CH derivative. Nanoparticle size and zeta potential were verified by dynamic light scattering. Their TNFα-knockdown effects were tested in a murine collagen antibody-induced arthritis model. TNFα expression was examined along with measurements of various cartilage and bone turnover markers by performing histology and microcomputed tomography analysis. Results: We demonstrated that folate-PEG-CH-DEAE₁₅/siRNA nanoparticles did not alter cell viability, and significantly decreased inflammation, as demonstrated by improved clinical scores and lower TNFα protein concentrations in target tissues. This siRNA nanocarrier also decreased articular cartilage destruction and bone loss. Conclusion: The results indicate that folate-PEG-CH-DEAE₁₅ nanoparticles are a safe and effective platform for nonviral gene delivery of siRNA, and their potential clinical applications warrant further investigation.