A highly efficient siRNA carrier of PBLG modified hyperbranched PEI

In search for effective non-viral gene vectors for the delivery of siRNA, a copolymer was designed and synthesized by grafting hydrophobic poly(gamma-benzyl L-glutamate) segment (PBLG) to hyperbranched polyethylenimine (PEI-PBLG). PEI-PBLG could efficiently deliver siRNA to cells to silence the targeted gene. Markedly, PEI-PBLG caused lower cytotoxicity in comparison to unmodified PEI. The siRNA complexed with PEI-PBLG showed a remarkable knockdown (75.23% relative to untreated cells, without changing the medium after 6 h of incubation) of the targeted luciferase gene in stable expressing luciferase CT26 cells while the Lipofectamine2000 and unmodified PEI could only achieve knockdown rates of 57.92% and 15.31%, respectively. The siRNA complexed with PEI-PBLG also demonstrated that it had greater gene silencing ability than unmodified PEI and Lipofectamin2000 in both 4T1 cells stably transfected with the luciferase gene and HeLa cells transiently transfected with the luciferase gene. The internalization efficiency of carrier/Alexa647-labeled siRNA was quantified using flow cytometry. PEI-PBLG/Alexa647-labeled siRNA showed internalization efficiency of 52.67% while PEI and Lipofectamine2000 demonstrated 27.23% and 37.91%, respectively. Confocal laser scanning microscopy (CLSM) assay also indicated that PEI-PBLG induced higher cell uptake efficiency than other commercial reagents. PEI-PBLG was shown to be a promising siRNA carrier with potential application in cancer therapy.