Design And Application Of Bio-degradable Polyethyleneimine As Gene Delivery Vectors

Gene therapy has become a new targeted and low-cytotoxic method for treating diseases,which has shown great application prospects in the medical field.Because of its low immunogenicity,simple synthesis and high transfection efficiency,cationic polymers has become a hotspot in the field of gene carriers.But the irreversible correlation between the transfection efficiency and cytotoxicity of polycations has always been a significant obstacle that severely limited the efficiency of gene delivery.This is mainly due to the molecular weight(MW)of the polycations.The higher the molecular weight,the higher the positive charge densities,and the polymers exhibited enhanced transfection efficiency but with higher cytotoxicity.PEI as a typical cationic polymeric carrier,its high cytotoxicity limits its further application in the field of gene delivery.To address this critical challenge,we have designed and developed a degradable high molecular weight PEI polymer that can efficiently condense DNA for cellular internalization and release DNA under responsive conditions.The research work is as follows:(1)In order to make the PEI polymer degradable,we synthetic two responsive dienes as the polymerization monomers,which have an acid-sensitive ester groups or reactive oxygen-sensitive thiol ketal groups.(2)Two degradable PEI polymers were prepared by Michael addition polymerization of PEI 600 and dienes.The PEI polymers could condense DNA tightly and form into nanocomplex(~180 nm).Compared to the commercially available transfection reagent PEI25 k,PEI-based degradable polymers exhibited improved gene delivery efficiency which increased nearly 3 times.Rapid degradation of the polymer upon acid or ROS triggering induces intracellular release of DNA,which can be greatly reduced cytotoxicity of the polymer,cell viability increased from 60% to over 90%.Particularly in cancer cells,ROS-responsive PEI polymers had also shown potential applications,exhibiting enhanced levels of in vivo gene expression.Therefore,our study can effectively balance the relationship between transfection efficiency and cytotoxicity of polycations,thereby providing an effective idea for rational design of non-viral gene delivery vectors.