(510a) Degradable And Charge Density-Changing Polyethylenimine For Controlled And Targeted Intracellular Delivery Of Plasmid DNA And Sirna

Endosomal escape and dissociation of nucleic acids from their carriers are rate-determining intracellular steps in nonviral gene delivery. Among many forms of nonviral vectors, polyethylenimine (PEI) has been widely used to deliver plasmid DNA, siRNA, and oligonucleotides due to its superior ability of nucleic acids condensation and buffering capacity. However, PEI is well-known for its intolerable cytotoxicity. Moreover, high molecular weight PEI, which is more potent than low molecule weight ones, is not bio-degradable and there is no evidence of clearance from the body. Degradable and charge-changing PEI was synthesized to obtain improved gene delivery efficiency through enhanced endosomal escape by proton sponge effect-independent ways, efficient dissociation of nucleic acids in intracellular targets after cationic branches become neutral, and reduced cytotoxicity. Characterizations of the PEI/nucleic acid polyplexes and ex vivo studies confirmed that the new PEI successfully condensed nucleic acids, rapidly freed nucleic acids, and transfected model cells with significantly increased efficiency. The new PEI also showed substantially decreased cytotoxicity even at high N/P ratios. More interestingly, controlled delivery of plasmid DNA and siRNA to the nucleus and cytosol, respectively, was achieved by modulating molecular weights and structures of the PEI. The talk will present synthesis and analysis of the new PEI, characterization of the new PEI/nucleic acids polyplexes using TEM, AFM, and dynamic light scattering (DLS), differentially controlled intracellular delivery of plasmid DNA and siRNA, and a model explaining the findings.