Effects of CdSe/ZnS and InP/ZnS QDs on cell viability in ML-1 and HeLa cell lines measured by XTT reagents. ML-1 thyroid cancer cells or HeLa cells were cultured with varying doses of green and red CdSe/ZnS or InP/ZnS QDs for 24 h, then cell proliferation/viability levels were measured at each concentration using a spectrophotometer at 7 h after XTT treatment. (A) ML-1 thyroid cancer cells showed no significant reduction in cell viability at all concentrations of green or red CdSe/ZnS QDs. NTC, non-treated control. DMSO, positive control. (B) There was no significant decrease in ML-1 thyroid cancer cells at all concentrations of green or red InP/ZnS QDs. (C) Reduced viability was observed in HeLa cells at 167 µg/mL of green CdSe/ZnS QD treatment. (D) HeLa cells show a reduction in cell viability at 167 µg/mL of green InP/ZnS QD treatment and 167 µg/mL of red InP/ZnS QD treatment. (E) Cell viability test with green and red CdSe/ZnS in mouse-derived non-cancerous fibroblast cells. (F) Cell viability test with green and red InP/ZnS in mouse-derived non-cancerous fibroblast cells. Statistically significant results are indicated based on p-values: * = p < 0.05, ** = p < 0.01, *** = p < 0.001, **** = p < 0.0001.