2.9. Cell toxicity assay

MTT assay was performed to evaluate the toxicity of GCE against MCF-7 cells. MCF-7 cells (5 × 10³ cells/well) were seeded and incubated for 24 h. The cells were treated with GCE at various concentrations (10–150 µg/ml). After incubation for 2 d, 25 µl, 5 mg/ml of MTT was added and the cells were incubated at 37 °C with 5% CO₂ for 4 h. The absorbance of each well was tested by microplate reader (EnSpire, PerkinElmer Inc., USA), and the detection wavelength was 570 nm.

The antitumor activity of different complexes in vitro was also tested by MTT test. The cells were treated respectively with naked NC, naked siRNA, GCE/NC, GCE/siRNA, Lipo/NC, Lipo/siRNA (containing 20, 40, 80, 120 and 160 nM siRNA).