Differences in subcellular distribution and toxicity of green and red emitting CdTe quantum dots
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Quantum dots (QDs) are emerging as alternative or complementary tools to the organic fluorescent dyes currently used in bioimaging. QDs hold several advantages over conventional fluorescent dyes including greater photostability and a wider range of excitation/emission wavelengths. However, recent work suggests that QDs exert deleterious effects on cellular processes. This study examined the subcellular localization and toxicity of cadmium telluride (CdTe) QDs and pharmacological means of preventing QD-induced cell death. The localization of CdTe QDs was found to depend upon QD size. CdTe QDs exhibited marked cytotoxicity in PC12 and N9 cells at concentrations as low as 10 µg/ml in chronic treatment paradigms. QD-induced cell death was characterized by chromatin condensation and membrane blebbing and was more pronounced with small (2r=2.2±0.1 nm), green emitting positively charged QDs than large (2r=5.2±0.1 nm), equally charged red emitting QDs. Pretreatment of cells with the antioxidant N-acetylcysteine and with bovine serum albumin, but not Trolox, significantly reduced the QD-induced cell death. These findings suggest that the size of QDs contributes to their subcellular distribution and that drugs can alter QD-induced cytotoxicity.
KeywordsQuantum dots Fluorescence Toxicity Cell death Antioxidants
Bovine serum albumin
3-(4,5-Dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide
This work was supported by the Juvenile Diabetes Research Foundation (Canada) and NanoQuebec. We thank Dr. E. Kumacheva (Department of Chemistry, University of Toronto) for helpful discussions and for suggestions on the preparation of water soluble QDs. J.L. also thanks J. Tam and R. Aikin for useful discussion and stylistic revisions of the manuscript.
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