Issue Date: June 22, 2009
Quantum Dots Linger In Mouse Tissue
Quantum dots could become fantastic contrast agents for medical imaging, but the glittering nanoparticles typically are made from toxic metals, and researchers don't know how long they remain in the body or whether they gradually dissolve. To shed light on those questions, Marcel P. Bruchez and colleagues of Carnegie Mellon University injected ZnS-coated CdSe quantum dots into mice and examined them with fluorescence imaging techniques (Nano Lett., DOI: 10.1021/nl901534q). Within days, the dots were undetectable in liver tissue, but they remained in bone marrow for months. Two years later, new images disclosed that some quantum dots still lingered in the animals' lymph nodes. The nanoparticles' emission spectra changed considerably, however, raising the possibility that they partially dissolved. The researchers conclude that quantum dots don't spill their metal contents quickly enough to pose an acute health risk, but it is unclear if the nanoparticles might cause chronic metal toxicity. They argue that quantum dots should be engineered to exit the body rapidly and should not be made from toxic metals, even if they have a sturdy shell.
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