Cationic Star Polymers-Based Gene Delivery

Thanks to the advantages such as low-cost,facile functionalization,and good safety,non-viral gene carriers are of great potential in the field of gene therapy.Cationic polymers have been one of the most developed non-viral gene carriers,however,hurdled by their low transfection efficiency.Herein,focused on the research about cationic gene carriers,we designed and synthesized biodegradable polypeptide derivatives and water-soluble conjugated polyelectrolytes,characterized the polyplex particle structures,and studied their in vitro gene delivery performance.This dissertation consists of three arms listed as below:Arm 1.Two biodegradable star cationic polymers(SP1-DET and SP2-DET)were synthesized by clean NCA-ROP reaction and explored for targeted gene delivery to macrophage RAW 264.7 cells after mannosylation and folate functionalization.These polymers are able to condense plasmid DNA into nano-sized globular particles.The particles were visualized with a distinct core-shell like morphology using transmission electron microscopy.Star polymers without the targeting ligand modification have poor in vitro macrophage transfection capability.However,by taking advantage of receptor-mediated internalization,gene delivery efficiency is significantly improved by folate-or mannose-functionalization on the side chains of star polymers.The optimization on chemical structures of star polymers is benifical for enhancement of gene delivery efficiency.Arm 2.We designed and synthesized a series of cationic polythiophenes(cPTs)for the study of gene delivery.Photophysical studies show cPTs are in well dispersed state in aqueous medium,and could be activated to induce ROS generation under white light irradiation.A small quantity of cPTs could form stable nanocomposites by assembling with SP/plasmid polyplex and enhance in vitro transgene efficacy by raising endo-lysosomal permeability.Moderate photosensitization of oxygen was correlated to successful gene delivery.Short cPTs such as linear cLPT-2(GPC-based MW<10 KDa)and hyperbranched cBPT-3(GPC-based MW<5 KDa)with weak photosensitization capability were found to enhance polyplex stability and contribute to the best performance as transgene enhancer.Our strategy to employ biocompatible polythiophenes as gene delivery enhancer provides a generalized simple,economic and efficient platform for nonviral gene delivery applications.Arm 3.Four cationic poly(phenylene-ethynylene)(P-O-3,P-C-3,PIM-2,PIM-4)with different side chains were explored for gene delivery.The rigid backbone and ionic side chain of these cPPEs ensure them both photoelectronic properties and water solubility.In this chapter,we introduced a tiny amount of cPPEs into SP/DNA complexes system to form multicomponent nanocomposites,and further studied the effect on the gene delivery efficiency when adding rigid conjugated polyelectrolyte into relatively flexible polyaspartates.All of the cPPEs could assemble with SP/plasmid polyplex to form stable nanocomposites and enhance transgene efficacy in HeLa cells.The quantitative data showed that the transfection efficiency was improved by 2-3 times in dark with only 0.1%added cPPEs.Besides,with increasing amounts of cPPEs,the transfection efficiency reached a maximum at 0.25%cPPEs and then went down.Remarkably,transfection efficiency of the multicomponent nanocomposites containing 0.25%P-C-3 in SP/DNA was enhanced by 17 fold in comparison with SP alone.In conclusion,the addition of cPPEs in tiny quantities could significantly promote gene delivery outcome,which strongly supports our strategy that can be generalized for enhancing transgene performance of star polymers using conjugated polyelectrolytes as enhancer.Meanwhile,our strategy is useful to reduce the consumption of gene carrier materials and nucleic acids.