Development and characterization of chitosan-based novel gene carrier systems
Date of Issue2012
School of Mechanical and Aerospace Engineering
Gene delivery has abundant potential applications both clinically and for fundamental science research. However, the lack of effective carriers is a major barrier for development of human gene therapy. The aim of our study is to develop efficient non-viral gene carrier systems by using natural polysaccharide (i.e. chitosan (CS)), because of its biocompatibility, biodegradability, low toxicity, and high cationic potential. One of the challenges of using CS as a gene carrier is to overcome its low specificity and low transfection efficiency. This thesis mainly focuses on fabricating new CS-based gene delivery systems via chemical modifications. Grafting of synthetic polymers onto CS backbone can introduce desired properties and broaden its potential applications, while maintaining CS’s intrinsic biocompatibility. We successfully synthesized novel pH- and thermo-sensitive graft CS copolymers, using atom transfer radical polymerization (ATRP) and two “grafting onto” methods. These approaches to well-defined comb-shaped cationic copolymers provide a versatile means for tailoring the functional structure of non-viral gene carriers. Based on the understanding of copolymers’ association behavior in different environments, the thermo-responsive transfection of DNA using selected CS terpolymers was fully explored. The term multidrug resistance (MDR) is used to define a resistance phenotype where cancer cells become resistant simultaneously to multiple drugs with no obvious structural resemblance and with different molecular targets. Gene therapy has been reported to offer a promise to overcome MDR. Thus, combining of anti-cancer drug and gene therapies would be an effective strategy to enhance the therapeutic effectiveness. Under this background, we prepared CS-functionalized graphene oxide (named as CS-GO) as a hybrid nanocarrier and used it to deliver a water-insoluble anti-cancer drug and a reporter DNA into human cancer cell lines.