Font Size: a A A

Synthesis Of Polyethyleneimine Derivatives And Their Application As Carriers For Nucleic Acids

Posted on:2014-02-02Degree:DoctorType:Dissertation
Country:ChinaCandidate:J SunFull Text:PDF
GTID:1221330401460158Subject:Materials science
Abstract/Summary:PDF Full Text Request
Polyethylenimine (PEI), as a classic cationic polymer, has become one of themost promising and widely studied gene carriers, but its significant cytotoxicity andpoor biocompatibility severely limit its applications. Particles modified byzwitterionic compounds have strong resistance to non-sepcific protein absorption,excellent anti-clotting properties owing to the super-hydrophilicity of zwitterioniccompounds. In view of the biocompatibility of zwitterionic compounds, we designand synthesize a variety of gene carriers based on zwitterionic-compound-modifiedPEI derivatives. For these PEI derivatives, their complexation with nucleic acid,biocompatibility, cytotoxicity and transfection efficiency were investigatedexperimentally. The contents of the thesis were divided as follows:(1) Gene carrier PEI-PMPC was prepared by traditional radical polymerizationof PEI and2-methacryloyloxy ethyl phosphorylcholine (MPC). Sulfobetaine polymerswith relatively low molecular weight were synthesized by reversible addition-fragmentation chain transfer polymerization (RAFT), and were used to modify PEI25K to the gene carrier PEI-g-PDMMAPS. The resultant polymers were characterizedby1H NMR. The polymer/pDNA complexes were assessed by agarose gelelectrophoresis, dynamic light scattering (DLS), and Zata potential. Compared tounmodified PEI25K, they could exhibit enhanced resistance to serum protein; MTTassays show that the carriers modified by zwitterionic polymers have goodbiocompatibility, lower cytotoxicity, and higher transfection efficiency even in thepresence of serum.(2) PEI-DMAAPS were prepared by Michael addition reaction between PEI25Kand DMAAPS monomer. Three kinds of betaine modified gene carriers weresynthesized and characterized by1H NMR. The complexes were assessed by agarosegel electrophoresis, DLS, and Zata potential. The mean diameters of the complexeswere found to be in the range of200-400nm. Zeta potentials slowly increase andreach a plateau at about60mV as N/P increased. The protein adsorption amounts forthe three PEI-DMAAPS conjugates were at similar level, about half of that for PEI 25K. PEI-DMAAPS shows no hemolytic effects in the test. In Hela cells and HepG2cells, MTT assays show that PEI-DMAAPS have much lower cytotoxicity than PEI25K. The transfection efficiencies of PEI-DMAAPS23%and PEI-DMAAPS55%weremuch higher than PEI25K with or without serum; and the maximum genetransfection efficiency was reached at the N/P ratio of60.(3) Carboxybetaine CBAA was adopted as a cross-linking agent to crosslink PEI1800, and then the crosslinked oligomers were used to synthesize new gene carriersPEI-CBAA2.8and PEI-CBAA4.5. Their structure was characterized by1H NMR. Gelelectrophoresis experiments showed that PEI-CBAA2.8and PEI-CBAA4.5canefficiently condense pDNA even similar to PEI25K. DLS and Zata potential testsshowed that the complexes sizes were in the range of260-500nm. MTT assayshowed that the the PEI-CBAA polymers amolst have no cytotoxicity against Helacells and HepG2cells. They could effectively mediated gene transfection, thetransfection efficiency of both complexes were even higher than PEI25K in Hela andHepG2cells. With increased mass ratio, the transfection efficiency increased as well.In summary, we synthesized a variety of gene vector systems based on PEI andzwitterionic compounds. They exhibit good biocompatibility, low cytotoxicity, andhigh transfection efficiency, especially in the presence of serum. Hence these PEIderivatives have great potential to become a new type of safe and efficient genecarriers.
Keywords/Search Tags:gene delivery, polyethylene imine, zwitterionic compound, biocompatibility, cytotoxicity, transfection efficiency, serum
PDF Full Text Request
Related items