Addition of poly (propylene glycol) to multiblock copolymer to optimize siRNA delivery

Dai, Zhi; Arévalo, Maria T; Li, Junwei; Zeng, Mingtao

Methoxypolyethylene glycol amine (PEG-NH 2 , Mw 5000), Poly(ethylene glycol) bis(amine) (H 2 N-PEG-NH 2 , Mw 3400), O,O'-Bis(2-aminopropyl) polypropylene glycol-blockpolyethylene glycol-block-polypropylene glycol (H 2 N-PPG-PEG-PPG-NH 2 , Mw 1900), Nε-benzyloxycarbonyl-l-lysine, bis(trichloromethyl) carbonate, hexane, diethyl ether, tetrahydrofuran (THF), trifluoroacetic acid (TFA), N,Ndimethylformamide (DMF), hydrogen bromide (30% in acetic acid), and other chemical reagents were purchased from Sigma-Aldrich. Lipofectamine™ 2000 transfection reagent and 3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) were purchased from Life Technologies. GFP-targeted siRNAs were synthesized by Integrated DNA Technologies and the sequence used was 5′-AAGCUGACCC UGAAGUUC AdTdT-3′ for the sense strand and 5′-UGAACUUCAG GGUCAGCU UdTdT-3′ for the anti-sense strand. For cellular uptake studies, the 5′ end of the sense strand was modified with Cy3 fluorescent dye.