Parallel Synthesis Of Poly (Maleic Acid Alkyl Ester-Alkyl Amino Side Chain) Cationic Polymer Library And Its Application In Cancer Gene Therapy

Gene therapy is the delivery of therapeutic genes to target cells to correct defects and disorders in the genetic level.For the past decades,gene therapy has been proven to be an effective cancer treatment approach with low side effects.Non-viral vectors including cationic polymers,liposomes,dendrimers and polypeptides have become research hotspots due to biocompatiblity,low immunogenicity,ease-of-production and the potential for modification of their chemical structures.However,compared with the viral vectors,their clinic application is still bottlenecked by the low efficiency of gene transfection.Cationic polymers neutralize anionic charged DNA and thus pack large DNA coils into small DNA/polymer complex(polyplex),protecting the DNA from degradation,promoting cell uptake,and delivering DNA into the target cells for transfection.Extensive efforts have been devoted to develop degradable polycations with different synthetic routines by parallel synthesis.Parallel synthesis has attracted increasing attention as a means to facilely synthesize large numbers of polymers with functional diversity by tailoring the structures of monomers.After high throughput screening,polymers with high transfection efficiency were selected and the relationship between polymer structures and transfection efficiency can be clearly elaborated,which is of great significance for designing non-viral vectors with high gene delivery efficiency.The current approaches for parallel synthesis including reacting amine with acrylate or epoxy,aminothiols with valerolactones or using passerini reaction.Designing a new synthesis route is badly needed for preparing a series of cationic polymers for gene delivery with high transfection efficiency.Herein,we report a post-modification method for facile synthesis of esterase-responsive cationic polymers for gene delivery.A library of 126 degradable cationic polymers have been successfully synthesized by directly conjugating 18 mercaptamine side chains to 7 poly(maleic acid alkyl esters)backbones,thereby overcoming current limitations in functionality and scalability and demonstrating the effects of different structural features on gene delivery.Initially,the gene expression level of cationic polymers was evaluated through semi-high-throughput screening method using the luciferase-encoding plasmid as the report gene.7 out of 126 cationic polymers had high luciferase expression level with remarkably serum resistant property.Subsequently,the transfection efficiency of 7 polymers was evaluated by measuring the percentage of expressing cells using enhanced green fluorescent proteins-encoding plasmid as the report gene.We summarized the effects of polymer structures on DNA packing ability,transfection efficiency and polyplex sizes.Finally,the best performing polymer G-1 was selected to deliver the therapeutic gene pTRAIL to the intraperineal tumors and exhibited significant inhibition on tumor growth compared with PEI25k/pTRAIL.