Oral Delivery of DNA Vector Conjugated with Chitosan and Its Effect on Th1 Polarized Inflammation

Gene therapy can be defined as the transfer of genetic materials to specific cells in order to exert a therapeutic effect. Gene therapy is a promising approach to the treatment of a wide range of diseases by compensating for defective genes or producing beneficial proteins (Zhao et al., 2009; Mansouri et al., 2004). Gene vectors play many important roles in gene therapy. Recently, nonviral vectors have been increasingly proposed as safer alternatives to viral vectors because of their potential advantages such as ease of synthesis, cell/tissue targeting, low immune response, and unrestricted plasmid size (Leong et al., 1998). Among nonviral systems, cationic polymers have attracted a great deal of attention because they can easily form self-assembling polyelectrolyte complexes between plasmid DNA and cationic polymers and mediate transfection via condensing DNA into nanoparticles, protecting DNA from enzymatic degradation, and facilitating cell uptake and endolysosomal escape (Wang et al., 2002). Among cationic polymers, polyethylenimine (PEI) and chitosan are widely used as nonviral vectors for gene delivery. These compounds have the same ability to enter cells by binding to proteoglycans on cell surfaces and undergoing endocytosis (Lungwitz et al., 2005; Köping-Höggard et al., 2001; Mansouri et al., 2006). However, after uptake, they have very different transfection efficiencies. PEI is considered to be the most effective cationic polymer for gene delivery (Densmore et al., 2009). However, PEI is also associated with dose-dependent toxicity, especially at high molecular weights, which probably explains why it has not yet been used in human studies (Kunath et al., 2003). Conversely, chitosan is degraded in the endosome and the material is then released into the cytoplasm. The material is then transported to the nucleus. Therefore, chitosan is generally considered less effective in gene delivery systems than PEI in vitro and in vivo. However, it is well known as a biocompatible, biodegradable, and relatively non toxic material with high cationic potential (Lee et al.,1998). Therefore, chitosan nanoparticles could be applied to vectors for gene delivery. In addition, chitosan is a widely available orally administered protein that can also be readily formed into nanoparticles able to entrap plasmid DNA and promote gene expression (Bowman & Leong , 2006). The purpose of this study was to evaluate chitosans of different molecular weights as DNA complexing agents based on their efficiency at transfecting RAW 264.7 cells and their in vivo