title: Long-term exposure to CdTe quantum dots causes functional impairments in live cells.
abstract: Several studies suggested that the cytotoxic effects of quantum dots (QDs) may be mediated by cadmium ions (Cd2+) released from the QDs cores. The objective of this work was to assess the intracellular Cd2+ concentration in human breast cancer MCF-7 cells treated with cadmium telluride (CdTe) and core/shell cadmium selenide/zinc sulfide (CdSe/ZnS) nanoparticles capped with mercaptopropionic acid (MPA), cysteamine (Cys), or N-acetylcysteine (NAC) conjugated to cysteamine. The Cd2+ concentration determined by a Cd2+-specific cellular assay was below the assay detection limit (<5 nM) in cells treated with CdSe/ZnS QDs, while in cells incubated with CdTe QDs, it ranged from approximately 30 to 150 nM, depending on the capping molecule. A cell viability assay revealed that CdSe/ZnS QDs were nontoxic, whereas the CdTe QDs were cytotoxic. However, for the various CdTe QD samples, there was no dose-dependent correlation between cell viability and intracellular [Cd2+], implying that their cytotoxicity cannot be attributed solely to the toxic effect of free Cd2+. Confocal laser scanning microscopy of CdTe QDs-treated cells imaged with organelle-specific dyes revealed significant lysosomal damage attributable to the presence of Cd2+ and of reactive oxygen species (ROS), which can be formed via Cd2+-specific cellular pathways and/or via CdTe-triggered photoxidative processes involving singlet oxygen or electron transfer from excited QDs to oxygen. In summary, CdTe QDs induce cell death via mechanisms involving both Cd2+ and ROS accompanied by lysosomal enlargement and intracellular redistribution.
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montréal, QC Canada.
authors.forename: Sung Ju
authors.initials: SJ
authors.lastname: Cho
authors.forename: Dusica
authors.initials: D
authors.lastname: Maysinger
authors.forename: Manasi
authors.initials: M
authors.lastname: Jain
authors.forename: Beate
authors.initials: B
authors.lastname: Röder
authors.forename: Steffen
authors.initials: S
authors.lastname: Hackbarth
authors.forename: Françoise M
authors.initials: FM
authors.lastname: Winnik
mesh_terms: D002104:Cadmium / Q000737:chemistry / Q000494:pharmacology; D019187:Cadmium Compounds / Q000737:chemistry* / Q000633:toxicity; D002413:Cations, Divalent / Q000737:chemistry; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D053758:Nanoparticles / Q000737:chemistry; D045663:Quantum Dots; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D013691:Tellurium / Q000737:chemistry* / Q000633:toxicity; D013997:Time Factors
chemical_list: D019187:Cadmium Compounds; D002413:Cations, Divalent; D017382:Reactive Oxygen Species; D002104:Cadmium; D013691:Tellurium; C028337:cadmium telluride