ocompatibility and effective cell uptake. Moreover, the vehicles can delivered siRNA to liver cancer cells *in vivo* and did not activate an innate immune response. Consequently, the mPEG-PE/CaP hybrid nanoparticles are promising siRNA loading systems thatcan be used for cancer treatment.

MATERIALS AND METHODS {#s4}
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Materials {#s4_1}
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L-α-phosphatidylethanolamine (Soy) was purchased from Avanti Polar Lipids, Inc. (Alabaster, AL). mPEG-COOH was purchased from Shanghai Yare Biotech, Inc. n-Hydroxysuccinimide (NHS) and 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) were obtained from GL Biochem (Shanghai) Ltd. Hepes, sodium hydroxide (NaOH), tris(hydroxylmethyl)aminomethane (Tris), 3- (4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and hydrochloric acid (HCl) were purchased from Sigma-Aldrich. Calcium chloride (CaCl~2~), trisodium phosphate (Na~3~PO~4~), sodium chloride (NaCl) and trichloromethane (TCM) were obtained from Sinopharm Chemical Reagent Co., Ltd. Foetal bovine serum (FBS), trypsin, penicillin, streptomycin, and high-glucose Delbecco\'s modified Eagle medium (DMEM) were obtained from Biosera.

The human liver cancer cell line SMMC-7721 was obtained from the Institute of Biochemistry and Cell Biology at the Chinese Academy of Sciences (Shanghai, China). SMMC-7721 cells were cultured in DMEM containing 10% FBS and 1% penicillin/streptomycin at 37°C in a humidified atmosphere containing 5% CO~2~.

Nude Balb/c mice (6 weeks old) were purchased from the Shanghai Silaike Laboratory Animal Ltd (Shanghai, China). All care and handling of animals were performed according to a research protocol approved by the Animal Care and Use Committee of the Shanghai Cancer Institute.

Synthesis and characterization of mPEG-PE {#s4_2}
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mPEG-COOH (1 g) and PE (0.4 g) were dissolved in 4 mL of TCM. After the mixture was stirred for 1 h at 25°C, and EDC·HCl (192 mg) and NHS (115 mg) were added to the solution