Study On Novel Polycationic Gene Vector Formed Of O-phthalaldehyde And Low-molecular-weight Polyethyleneimine

The lack of safe and efficient gene delivery vectors is the main obstacle in the process of gene therapy. Comparing with viral vectors and cationic liposomes, cationic polymers possess several advantages, such as no immunogenicity and mutation danger, greater loading gene capacity and density, more stable structure, easier chemical modification and large-scale preparation. However, low transfection efficiency and high cytotoxicity greatly hinder the cationic polymers to clinical application. We designed and synthesized a novel cationic polymer, which had bisimine bonds conjugating with benzene ring. On one hand, this polymer condenses gene against degradation before transfection; on another hand, the polyplexes escape from endosome by proton sponge effect and the polymer degradates into samll compound without toxicity in the end.In this study, we designed and synthesized a novel PEI derivative(PEI-OP) by using polythylenimine 800 Da as the basic unit and a safetyknown drug metabolite o-Phthalaldehyde as the linker. The chemical structure and property were characterized by nuclear magnetic resonance(NMR), fourier transform-infrared(FT-IR) and size exclusion chromatography(SEC). The polymer’s MW=43564 Da, Mn=32751 Da, PDI=1.33. Particle size and Zeta potential of polyplexes were 50-80 nm and 5-20 mV, respectively, which were conductive to cellular uptake and form stable dispersion systems. Agarose gel electrophoresis indicated that PEI-OP can entirely condense pDNA at the w/w ratio of 0.5 or above. Luciferase reporter gene results indicated that PEI-OP had high transfection efficiency in COS-7、Hela and SMMC-7721 cells;cell cotransfection experiments proved that PEI-OP had the ability to diliver siRNA into cells to silence gene. MTT results suggested that PEI-OP had lower cytotoxicity than commercial transfection agent PEI 25 KDa at the same concentration, the cell viability in COS-7、Hela and SMMC-7721 cells were 70-90 %、80-110 % and 80-110 %, respectively.In conclusion, the novel cationic polymer can effectively package gene to nanoparticles, facilitate polyplexes timely escape from endosomal, release gene materials and metabolize itself to nontoxic species, it may be an ideal gene delivery vector.