Multifunctional triblock co-polymer mP3/4HB-b-PEG-b-lPEI for efficient intracellular siRNA delivery and gene silencing

Abstract A non-viral siRNA carrier composed of mono-methoxy-poly (3-hydroxybutyrate-co-4-hydroxybutyrate)-block-polyethylene glycol-block-linear polyethyleneimine (mP3/4HB-b-PEG-b-lPEI) was synthesized using 1800 Da linear polyethyleneimine and evaluated for siRNA delivery. Our study demonstrated that siRNA could be efficiently combined with mP3/4HB-b-PEG-b-lPEI (mAG) co-polymer and was protected from nuclease degradation. The combined siRNA were released from the complexes easily under heparin competition. The particle size of the mAG/siRNA complexes was 158 nm, with a ζ-potential of around 28 mV. Atomic force microscopy images displayed spherical and homogeneously distributed complexes. The mAG block co-polymer displayed low cytotoxicity and efficient cellular uptake of Cy3–siRNA in A549 cells by flow cytometry and confocal microscopy. In vitro transfection efficiency of the block co-polymer was assessed using siRNA against luciferase in cultured A549-Luc, HeLa-Luc, HLF-Luc, A375-Luc and MCF-7-Luc cells. A higher transfection efficiency and lower cytotoxicity was obtained by mAG block co-polymer in five cell lines. Furthermore, a remarkable improvement in luciferase gene silencing efficiency of the mAG complex (up to 90–95%) over that of Lipofectamine™ 2000 (70–82%) was observed in HLF-Luc and A375-Luc cells. Additionally, a mAG/p65-siRNA complex also showed a better capability than Lipofectamine™ 2000/p65-siRNA complex to drastically reduce the p65 mRNA level down to 10–16% in HeLa, U251 and HUVEC cells at an N/P ratio of 70.