Polymeric Nanomaterial As Nucleic Acid And Drug Delivery System For Cancer Therapy

Polymeric nanoparticles for target gene and drug delivery are the new drug delivery system for cancer therapy. It is safe and effective for cancer therapy through incorporating functionalities to polymeric materials for achieving target specificity, controlled therapeutic drug release and improved the bioavalability. Due to the positive zeta potential and amenable to surface modification, the cationic polymers become the focus for the ability of interacting with the cell membrane and effective gene transfection. In this dissertation, we sysnthesized a PEI-based polymer PC composed of β-cyclodextrin (β-CyD) cross-linked by low molecular weight PEI (600Da). I have investigated the mechanism of the intracellular pathway and nuclear entry of PC mediated gene delivery, following evaluated the CC9peptides modified PC for microRNA based cancer therapy and further explored the positive effect of PC for combined cancer therapy.The main content and conclusion of this dissertation are summarized below:In part I, PC transfected DNA is internalized by binding membrane-associated proteoglycans. The endocytic pathway of the PC particles is caveolae-and clathrin-dependent with both pathways converging to the lysosome and escape from the lysosome because of the "proton sponge effect". Lysosomal inhibition with chloroquine has no effect on PC mediated transfection implying that nuclear entry is the limiting factor. To improve the nuclear delivery of PC transfected DNA, nuclear localization signal (NLS) peptides are chosen to conjugate and combine with the PC. Compared to PC/pDNA, PC-NLS/pDNA, and PC/pDNA/NLS can effectively improve gene transfection in dividing and non-dividing cells.In part II, miR-34a-delivering therapeutic nanocomplexes with a tumor-targeting and-penetrating bifunctional CC9peptide were proposed for efficient treatment of pancreatic cancers. The nanoparticle-based miR-34a delivery systems could effectively facilitate in vitro and in vivo targeting. The multifunctional nanoparticles for miR-34a delivery could greatly up-regulate the mRNA level of miR-34a in PANC-1cell lines. The upregulation of miR-34a remarkably induced cell cycle arrest and apoptosis, suppressed the tumor cell migration and inhibited the target gene expressions such as E2F3, Bcl-2, c-myc and cyclin D1. More importantly, the in vivo systemic administration of the developed targeting miR-34a delivery systems in a pancreatic cancer model significantly inhibited tumor growth and induced cancer cell apoptosis.In partⅢ, suparmolecular polymer self-assembled from the host PC and guest adamantine conjugated PTX (Ada-PTX) for simultaneous delivery of siRNA and a chemotherapeutic drug were prepared. The Ada-PTX is encapsulated inside the core and shRNA sticks to the shell surface to improve the drug sensitivity. The physicochemical properties of these supramolecular nanoparticles are favorable to cell uptake and intracellular trafficking. Moreover, PTX and shRNA simultaneously delivered to SKOV-3cells lead to efficient reduction in the survivin and Bcl-2expression as well as synergistic cell apoptotic induction in the in vitro study. In particular, co-delivery of survivin shRNA and PTX suppresses cancer growth more effectively than delivery of either paclitaxel or shRNA in ovarian cancer therapy.In part IV, we explored a new strategy of generating hybrid vectors that coated attenuated salmonella with PEI-based polyplexes via electrostatic interaction. Low dose PEI-based polyplexes coating on the surface of the salmonella (2.5μg/1×106) could be achieved, while retaining the vitality of the bacterial. The cationic nanoparticles coating salmonella showed enhanced cellular uptake and multi-pathways of cell endocytosis to track to lysosome in RAW264.7cells. In addition, compare to the naked salmonella, the cationic nanoparticles coating salmonella could escape from the lysosome and induce lower pH in peritoneal macrophage, which is useful for gene expression. Moreover, the cationic polyplexes coating salmonella could promote the highest immune response and induce lowest toxicity to the small intestines of mice.