Polyplexes assembled with internally quaternized PAMAM-OH dendrimer and plasmid DNA have a neutral surface and gene delivery potency.
Interior tertiary amine groups of PAMAM-OH dendrimers (hydroxyl-terminated polyamidoamine, PAMAM) were modified by methylation to make these polymers have a more cationic character, which enabled electrostatic interaction between PAMAM-OH and plasmid DNA. A methylation reaction was dose-dependent, producing internally quaternized PAMAM-OH (QPAMAM-OH), thereby making tertiary amine/quaternary amine ratio adjustment possible. More highly condensed particles of plasmid DNA were formed as the degree of quaternization increased, whereas unmodified polymer (PAMAM-OH) could not. The location of positive charges in the internal position of QPAMAM-OH resulted in the formation of neutral polyplexes in which zeta potential leveled off near the zero value even at high charge ratios (+/-) of 10. A light scattering experiment showed that the polyplex formed by QPAMAM-OH was very small with the size of 53.3 nm at the optimum condition. QPAMAM-OH/DNA polyplexes were round-shaped with the more compact and small particles formed as the charge ratio increased. QPAMAM-OH showed much reduced cytotoxicity compared with starburst PAMAM and branched polyethyleneimine (PEI) in which shielding of interior positive charges by surface hydroxyls might be the reason for this favorable result. These results suggest that QPAMAM-OH could be a promising tool as a nonviral vector both by itself and in conjugated form with targeting ligands.
Lee
Jung Hoon
JH
School of Chemistry & Molecular Engineering, Seoul National University, Kwanak-ku, Seoul 151-742, Korea.
Lim
Yong-beom
YB
Choi
Joon Sig
JS
Lee
Yan
Y
Kim
Tae-il
TI
Kim
Hyun Jin
HJ
Yoon
Jae Keun
JK
Kim
Kwan
K
Park
Jong-sang
JS
D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D050091:Dendrimers; D004996:Ethidium / Q000737:chemistry; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006801:Humans; D008027:Light; D008745:Methylation; D018625:Microscopy, Atomic Force; D015394:Molecular Structure; D010957:Plasmids / Q000378:metabolism*; D011073:Polyamines / Q000138:chemical synthesis / Q000378:metabolism* / Q000633:toxicity; D012542:Scattering, Radiation; D013499:Surface Properties; D014162:Transfection
D050091:Dendrimers; C104700:PAMAM Starburst; D011073:Polyamines; D004247:DNA; D004996:Ethidium