In vitro cytotoxicity assay

The standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method was used for detection of nanoparticle cytotoxicity. MTT was reduced by succinate dehydrogenase in the mitochondria into a blue-purple precipitate that is insoluble in water, while dead cells have no such function. The blue-purple precipitate can be dissolved by DMSO, and the absorbance at 490 nm was determined to reflect the living cell number as well as its proliferation. In the experiment, 96-well plates were used to foster different concentrations of the nanoparticle suspension and HepG2 for 24 h. Only nanoparticle suspensions were added to the control group. Then, each well was supplied with MTT solution (20 μl, 5 mg/ml) and incubated for 4 h. Finally, we aspirated the medium out and added 150 μl of DMSO, followed by testing the absorbance value for each well.