Example 5
MTT cytotoxicity assays were used to assess the cytotoxicity of RGQDs/Nd-GQDs/Tm-GQDs. HeLa cells were plated in a 96-well plate with 5000 cells per well (100 μL/well) and kept in an incubator overnight at 37.1° C. while maintaining the CO2/air ratio of 1:19. After 24 h of incubation, the samples were added into each well at different concentrations for different materials (0 to 70 μg/mL, 1 mg/ml, 0.25 mg/ml for RGQDs, Nd-GQDs, Tm-GQDs, respectively). After 24 h of incubation, the medium was replaced by 100 μL of 1 mg/mL thiazolyl blue tetrazolium bromide. After 4 h of further incubation, MTT (3-(4-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) was replaced with 100 μL of DMSO (dimethyl sulfoxide) to solubilize the precipitation. Reduction in MTT influences the metabolic activity of living cells, which can be assessed with absorbance measurements because living cells metabolize the MTT and form a highly absorbing purple colored byproduct known as formazan. The absorbance (essentially the cell viability) of the final sample was measured at 540 nm wavelength using the FLUOstar Omega microplate reader.
