*2.4. Cell Transfection*

The Ca9-22 cells were seeded on 24-well culture plates and incubated for 12 h before transfection. Normally, 0.6 μg of nanoparticles and 0.2 μg of siRNA were diluted with 20 μL of Opti-MEM Reduced Serum Medium separately and then mixed together. The mixtures were incubated at room temperature for 10 min and added to the cells. The cells were incubated under the magnetic field for 30 min (Mag0201, Nanoeast, Nanjing, China) and then under normal conditions. The transfection of siRNA using Lipofectamine 3000 Transfection Reagent (L3000015, Invitrogen, Shanghai, China) was carried out according to the manufacturer's instructions, serving as a positive control. FAM-siRNAs were used for observation of the cellular uptake of siRNA by fluorescence microscope (Observer A1, Carl Zeiss, Oberkochen, Germany). All the siRNA duplexes were chemically synthesized by GenePharma (Shanghai, China) and the sequences were as follows: siBCL2—5 -GGGAGAACAGGGUACGAUATT-3 ; siBIRC5—5 -GAAGCAGUUUGAAGAAUUATT-3 ; NC (non-targeting siRNA serving as a negative control) 5 -UCCGAACGUGUCACGUTT-3 .
