Remarkably Amplifying Gene Delivery Using Photoresponsive Conjugated Polymers

Conjugated polymers have light harvesting properties and can be used as exceptional photosensitizers in biomedical applications.However,one concern arises from their potential phototoxicity to cells and particularly delivery cargos such as nucleic acids for gene delivery.In the present approach,we investigated the optical properties of six cationic PPEs that differ in side chains or charge density or self-assembly,and applied them as a component of BPEI/DNA or SP/DNA polyplexes in trace amounts by the sequential mix method to boost gene delivery in tumor cells.This dissertation consists of three arms listed as below:Arm1.Cationic conjugated polymers,such as cationic poly(phenylene ethynylene)s(cPPEs),in trace amount are able to accumulate in the polymeric shell of branched polyethylenimine(BPEI)/DNA complexes,and photodamage of supercoiled DNA by light-induced singlet oxygen generation is completely suppressed,independent on the singlet generation capability of conjugated polymers.We reported that cPPEs polyplexes prepared by a sequential method could greatly amplify transfection of gene green fluorescence protein(GFP)by BPEI on tumor cells with efficiency from 14%to 86%without decreasing cell viabilities,well solving the problem with poor transfection capability of BPEI under low DNA loading condition.Our strategy to take advantage of conjugated polymers as photosensitizing agents in gene delivery system is simple,safe and efficient,and promising for broad application in gene delivery areas.Arm2.Considering that BPEI is more cytotoxic than other cationic polymer carriers,we tried another biocompatible carrier,SP.The modification of the diethylene triamine group on the side group allowed SP with capability of proton sponge effect,SP prevails over BPEI in gene delivery.We found that the introduction of trace amount of cPPEs into the polymeric shell of polyplexes can still significantly improve the transfection efficiency through PCI,PCI-effective 0.5 N/P%PIM-2 could improve the transfection efficiency of expressed Luc in cells by 17.3-fold.Our data indicate that the PCI effect by light harvesting cPPEs are highly Φ△ dependent and different host cationic polymer carriers will not obviously influence the enhanced transfection of cPPEs by means of PCI.The method of enhancing the transfection of genes by means of photochemical internalization is remarkably simple,universal and effective and paves a way for the construction of other novel non-viral gene delivery systems.Arm3.Polymer with the guanidinium groups modified side chains(P-OE-GUA)and polymer with the helical conformation(M-P-O-2)are two new cPPEs,P-OE-GUA is para-linked PPE-type polymer with guanidinium groups modified side chains,which makes P-OE-GUA facilitate cellular uptake.While,M-P-O-2 is meta-linked PPE-type polymer and could self-assemble into a helical conformation in aqueous solution,significantly different from above five cPPEs which tend to self-assemble into the lamellar structures in water.The solubility of P-OE-GUA in water is extremely small,so we followed the method of the previous two chapters and introduced trace amount of P-OE-GUA to the SP/DNA nanocomposite surface to examine the ability of P-OE-GUA of enhancing gene delivery.P-OE-GUA could help enhance the SP/DNA gene transfection in the absence of light radiation,which has a great relationship with the guanidinium groups.For M-P-O-2,material toxicity to HeLa cells,imaging,and intracellular distribution were studied,and we found that M-P-O-2 has excellent biocompatibility.At the same time,as the incubation time with cells increases,cellular uptake doesn’t increase accordingly.However,the material seems to be less likely to interfere with the cell membrane due to helical morphology,and is basically distributed in the cell membrane.Our research for P-OE-GUA and M-P-O-2 is still in the primary stage,and further investigation in in vitro gene delivery performance needs to be done.