A new study published in the recent edition of Nature Nanotechnology is being widely touted as great evidence that one of the darlings of the nanotechnology world – Quantum Dots – are finally proven safe for use in medicine.

We don’t agree.

Quantum dots are tiny luminescent crystals and are suggested to be a possible tool for treating and detecting diseases like cancer. However, according to the researchers “Cadmium-Selenium nanocrystals are among the brightest, best-studied and most widely available quantum dots for bioimaging, but there are significant toxicity concerns because of their cadmium content”.

Concerns are largely based on in vitro studies which demonstrate cadmium toxicity, although in vivo studies with mice do not show the same dangers.

So these researchers decided to inject cadmium-based quantum dots into four rhesus macaque monkeys to measure the toxic effect.

The headlines that have resulted:

AZONanoNews – “Toxicity Study Ensures Safety of Quantum Dots in Nanomedicine Applications

University at Buffalo – “Good News for Nanomedicine: Quantum Dots Appear Safe in Pioneering Study on Primates

Basically, the study found a number of blood and biochemical markers suggested these monkeys stayed healthy over 90 days, whilst maintaining weight and found “no abnormalities were observed in important organs“. The researchers also tested two other monkeys for a period of an additional year and “observed no signs of abnormalities.

That is, apart from the observation that “more than 90% of the injected cadmium remains in the animals’ organs after 90 days”.

With the authors cautioning that “more research is needed to determine quantum dots’ long-term effect on health”, how can these sources responsibly conclude that quantum dots “Appear Safe” or this study “Ensures Safety” ??