Gold Nanoparticle Dendrimer Conjugates for Gene Therapy

Abstract

Gene therapy is a promising treatment that has enormous potential for the management of numerous diseases of acquired and innate origin. Viral delivery vectors are successful in delivering therapeutic DNA, but their efficacy is circumvented by immunogenicity and cost. Non-viral vectors face other issues of inflammatory response, colloidal stability, and low transfection efficiency. Gold nanoparticles (AuNPs) have emerged as attractive nanocarriers for gene delivery. AuNPs are bioinert, easily synthesized, and possess rich surface chemistry that facilitates versatile functionalization. Therefore, AuNPs provide an excellent platform for gene delivery. Polyamidoamine (PAMAM) dendrimers are commercially available cationic branched polymers in which growth branches from a core molecule. Their physiochemical properties make PAMAM dendrimers well suited for gene delivery applications. In this thesis, PAMAM dendrimers are functionalized on the surface of small AuNPs yielding a unique class of gene delivery vectors termed AuPAMAM vectors. We begin by establishing the synthesis and characterization of AuPAMAM vectors, showing that AuPAMAM colloidal stability and DNA condensation ability are dependent on the PAMAM conjugation reaction rate, and that this reaction rate can be altered to enhance transfection efficiency in vitro. Then, we further investigate the influence of each chemical component of the bottom-up AuPAMAM synthesis process by systematically probing each step of the reaction and analyzing its effect on the overall transfection efficiency and cytotoxicity. Finally, in order to clarify the mechanism underlying the differential transfection efficiency seen across many cell lines and tissues, the AuPAMAM vectors are tracked intracellularly over time in vitro using confocal imaging, cellular TEM and flow cytometry. Together, this thesis demonstrates that AuPAMAM conjugates present attractive candidates for non-viral gene delivery due to their commercial availability, ease of fabrication and scale-up, high yield, high transfection efficiency and low cytotoxicity. Additionally, this thesis demonstrates the need to characterize the tissue-specific transfection hurdles vectors face in order to improve application-specific non-viral vector design.