Intracellular microenvironment responsive nanogels for gene delivery

Abstract

Gene therapy is a modern technology applied by using therapeutic nucleic acids to treat or prevent diseases. The therapeutic nucleic acids can either be expressed to recombinant proteins for disease treatments or correct the genetic mutations in gene therapy for the treatments of various diseases. However, the development of gene therapy is greatly impeded by the limitation of gene delivery systems. Delivery of gene to eukaryotic cells is a multi-step process. Several barriers including cell membrane, nuclear pore complex (NPC) and intracellular enzymes have inhibited the transfection efficiency of gene. Therefore, the exploring of safe and high efficient gene carriers is essential for the development of gene therapy. In this thesis, one of the widely studied cationic polymers, polyehtylenimine (PEI), was employed for modifications in the gene delivery application. High molecular weight PEI (HMW PEI) is able to perform high efficient gene transfection to eukaryotic cells due to its good buffering capacity. However, it also has high cytotoxicity to cells owing to its non-biodegradability and its molecular weight related high positive charge density. On the other hand, low molecular weight PEI (LMW PEI) such as PEI800 shows negligible cytotoxicity to cells, but has low transfection efficiency. In order to reduce the cytotoxicity of PEI-based gene carrier while keep or improve the transfection efficiency, two biodegradable PEI-based gene carriers have been designed and successfully synthesized. The physical and chemical properties of both synthetic carriers were measured. The gene delivery performances of both carriers were also evaluated against Hela and HEK 293 cells. The synthetic biodegradable gene carriers display good gene binding ability, low cytotoxicity and good buffering capacity. In addition, both carriers are able to perform gene transfection with high efficiency.