title: Nanostructure of polyplexes formed between cationic diblock copolymer and antisense oligodeoxynucleotide and its influence on cell transfection efficiency.
abstract: Although various cationic polymers have been used to condense anionically charged DNA to improve their transfection efficiency, there is still a lack of fundamental understanding about how to control the nanostructure and charge of the polyplexes formed and how to relate such information to cell transfection efficiency. In this work, we have synthesized a weak cationic and phosphorylcholine-containing diblock copolymer and used it as a model vector to deliver an antisense oligodeoxynucleotide (ODN) into HeLa cells. Small angle neutron scattering (SANS) was used to determine the copolymer/ODN polyplex structure. The SANS data revealed the formation of polyplex nanocylinders at high copolymer (N)/ODN (P) charge ratios, where N symbolizes the amine groups on the copolymer and P symbolizes the phosphate groups. However, the cylindrical lengths remained constant, indicating that the ODN binding over this region did not alter the cylindrical shape of the copolymer in solution. As the N/P ratio decreased and became close to unity the polyplex diameters remained constant, but their lengths increased substantially, suggesting the end-to-end bridging by ODN binding between copolymer cylinders. As the N/P ratios went below unity (with ODN in excess), the polyplex diameters increased substantially, indicating different ODN bridging to bundle the small polyplexes together. Transfection studies from HeLa cells indicated a steady increase in transfection efficiency with increasing cationic charge and decreasing polyplex size. Cell growth inhibition assay showed significant growth inhibition by the polyplexes coupled with weak cytotoxicity, indicating effective ODN delivery. While this study has confirmed the overall charge effect, it has also revealed progressive structural changes of the polyplexes against varying charge ratio, thereby providing useful insight into the mechanistic process behind the ODN delivery.
authors.affiliation: Biological Physics, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester, United Kingdom.
authors.forename: Xiubo
authors.initials: X
authors.lastname: Zhao
authors.forename: Fang
authors.initials: F
authors.lastname: Pan
authors.forename: ZhuoQi
authors.initials: Z
authors.lastname: Zhang
authors.forename: Colin
authors.initials: C
authors.lastname: Grant
authors.forename: YingHua
authors.initials: Y
authors.lastname: Ma
authors.forename: Steven P
authors.initials: SP
authors.lastname: Armes
authors.forename: YiQing
authors.initials: Y
authors.lastname: Tang
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Lewis
authors.forename: Thomas
authors.initials: T
authors.lastname: Waigh
authors.forename: Jian R
authors.initials: JR
authors.lastname: Lu
mesh_terms: D017209:Apoptosis; D002412:Cations / Q000737:chemistry; D004587:Electrophoresis, Agar Gel; D006367:HeLa Cells; D006801:Humans; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry*; D009502:Neutrons; D020319:Oligodeoxyribonucleotides, Antisense / Q000737:chemistry* / Q000235:genetics*; D011108:Polymers / Q000737:chemistry*; D013057:Spectrum Analysis; D014162:Transfection / Q000379:methods*
chemical_list: D002412:Cations; D020319:Oligodeoxyribonucleotides, Antisense; D011108:Polymers