Quantum dots (QD) are increasingly used in medical and biological applications promising advanced imaging tools at diagnostic and molecular levels. However, the possible toxic hazards associated with exposure to these nanoparticles are still limited to cytotoxicity studies. Therefore, this study aims to provide a fundamental understanding of the kinetics of uptake and distribution of carboxyl (negative), amine (positive) and HDA (neutral) coated cadmium-selenide/zinc-sulfide QD in human lymphoblastoid (TK6), bronchial epithelial (BEAS-2B) and skin fibroblast (HFF-1) cells and their cyto- and geno-toxic effects.
Following thorough characterisation, multiparametric imaging techniques have been used to investigate cellular uptake and distribution of these QD including flow cytometry, ImageStream analysis, confocal microscopy, transition electron microscopy and single particle tracking techniques. The long term (1, 3, 5 and 7 days) QD genotoxicity following cell uptake in correlation to the amount and form of dose delivery to the cells were also examined after separating two cell fractions (containing high and low percentages of QD) by flow cytometry (FACS Aria).
The data show that QD toxicity is charge, dose and cell dependent. In general, bronchial epithelial cells were more resistant to all three QD showing no cyto- or geno-toxic effects even in the presence of cellular uptake. Lymphoblastoid cells were more sensitive to all types of QD then the skin cells. Neutrally charged QD were highly cytotoxic and genotoxic in a dose dependent way in TK6 cells yet only cytotoxic effects were seen in HFF-1 cells. High levels of cellular uptake were clear in cells exposed to carboxyl QD especially at doses above 7.5nM which was in correlation with a significant increase in the micronucleus (MN) and mutation frequencies (hprt) detected at these doses.
These data highlight the importance of using a battery of assays to understand cellular interactions with nanomaterials in order to determine safe application parameters.