Chitosan for DNA and gene therapy

Gene therapy is a prospective treatment modality for a wide spectrum of genetic diseases. Nevertheless, the basic challenge with gene therapy is the design of an appropriate gene delivery vector that is both safe and efficient. Viral vectors offer adequate transfection of genes, but concerns about the safety profile restrict their therapeutic applications. Among nonviral vectors, chitosan and chitosan-based systems have gained increasing interest because of their good safety profile and favorable physicochemical properties as gene carriers. However, weak transfection efficiency and poor cell specificity of chitosan are challenges that currently limit clinical applications. The core objective of this chapter is summarizing the applications of chitosan-based formulations for gene transfer and particularly the influence of various formulation parameters on efficacy, including molecular weight and degree of deacetylation of chitosan, stoichiometry of chitosan/DNA polyplex, pH of the transfection medium, and serum concentration. A special focus is bestowed on diverse structural modifications of chitosan to improve its gene transfer efficacy and cell specificity. Furthermore, we also illustrate the preparation, physicochemical, and in vitro characterization techniques of chitosan/DNA polyplexes in detail.