Polyion complex micelles of pDNA with acetal-poly(ethylene glycol)-poly(2-(dimethylamino)ethyl methacrylate) block copolymer as the gene carrier system: physicochemical properties of micelles relevant to gene transfection efficacy.
An acetal-poly(ethylene glycol)-poly(2-(dimethylamino)ethyl methacrylate) (acetal-PEG-PAMA) block copolymer spontaneously associated with plasmid DNA (pDNA) to form water-soluble complexes (polyion complex micelle: PIC micelle) in aqueous solution. Physicochemical characteristics and transfection efficiency of the PIC micelles thus prepared were studied here, focusing on the residual molar mixing ratio (N/P ratio) of AMA units in acetal-PEG-PAMA to the phosphate units in pDNA. With the N/P ratio increasing to unity, acetal-PEG-PAMA cooperatively formed complex micelles with pDNA through electrostatic interaction, allowing pDNA to condense effectively. Dynamic light scattering measurements revealed that the PIC micelle at N/P > or = 3 had a constant size of approximately 90-100 nm. Eventually, acetal-PEG-PAMA/pDNA micelles underwent no precipitation even after long-term storage for more than 1 month at all N/P ratios. The PIC micelles were stable even in the presence of excess polyanions, poly(vinyl sulfate), in contrast to polyplexes based on the PAMA homopolymer, yet this stabilization effect was highly dependent on the N/P ratio to reach a plateau at N/P = 3-4. This character may be attributed to the increased hydrophobicity in the vicinity of the complexed pDNA. Furthermore, the pDNA in the micelle was adequately protected from DNase I attack. The transfection ability of the PIC micelles toward 293 cells was remarkably enhanced with an increasing N/P ratio as high as 25. The zeta-potential of the micelles with a high N/P ratio was an appreciably large positive value, suggesting a noncooperative micelle formation. This deviated micellar composition with an excess cationic nature as well as the presence of free acetal-PEG-PAMA may play a substantial role in the enhanced transfection efficiency of the PIC micelle system in the high N/P ratio (approximately 25) region.
Wakebayashi
Daisuke
D
Department of Materials Science and Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Nishiyama
Nobuhiro
N
Itaka
Keiji
K
Miyata
Kanjiro
K
Yamasaki
Yuichi
Y
Harada
Atsushi
A
Koyama
Hiroyuki
H
Nagasaki
Yukio
Y
Kataoka
Kazunori
K
D002412:Cations; D002460:Cell Line; D004247:DNA / Q000737:chemistry; D003850:Deoxyribonuclease I / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D004996:Ethidium / Q000494:pharmacology; D005822:Genetic Vectors; D006801:Humans; D008027:Light; D046911:Macromolecular Substances; D008689:Methacrylates / Q000737:chemistry; D008823:Micelles; D010957:Plasmids / Q000737:chemistry* / Q000378:metabolism; D000071228:Polyelectrolytes; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D012542:Scattering, Radiation; D055672:Static Electricity; D013997:Time Factors; D014162:Transfection
D002412:Cations; D004247:DNA; D003850:Deoxyribonuclease I; D004996:Ethidium; D046911:Macromolecular Substances; D008689:Methacrylates; D008823:Micelles; D000071228:Polyelectrolytes; D011092:Polyethylene Glycols; D011108:Polymers; C049840:2-(dimethylamino)ethyl methacrylate