Reduction of Cd2+/Ag+-induced toxicity by 3-mercaptopropionic acid-CdSe/ZnS quantum dots and glutathione-CdSe/ZnS quantum dots in human liver cancer cells

In the present study, we investigated the interactions between CdSe/ZnS core/shell quantum dots (QDs) and Cd-2(+) and Ag+ in HepG2 cells. Two typical QDs, 3-mercaptopropionic acid-CdSe/ZnS QDs (QD-MPA) and glutathione-CdSe/ZnS QDs (QD-GSH) were applied and proved to be stable, as no fluorescence changes and Cd2+ releasing were detected during 24-h incubation. Both QDs tended to accumulate in HepG2 cells, and significantly reduced the harmful effects of Cd(2+ )and Ag+. Correspondingly, the intracellular and extracellular concentrations of free metal ions decreased by 2-5 folds due to their adsorption on QDs. On the other hand, both QDs exhibited no significant adsorption on cell fragments, suggesting that they accumulated inside cells but not on the membrane. Therefore, they did not hinder the uptake of free Cd2+ or Ag+. After all, the results revealed that highly stable QDs could extensively reduce the toxicity of heavy metals by absorption of heavy metal ions.