Nanomedicine is a hugely promising field, but while remarkable new treatments and diagnostic tests are being developed, questions remain about the long term effects of nanoparticles on our bodies. Adding to our understanding of these issues, researchers have now reported that the use of quantum dots - tiny luminescent crystals that can be used to monitor disease at a cellular level - appears to be safe in primates over a one-year period.

The toxicity study was conducted by the University at Buffalo (UB), the Chinese PLA General Hospital, China's ChangChun University of Science and Technology, and Singapore's Nanyang Technological University.

With the aim of accessing the effect of quantum dots on humans, the study saw four rhesus monkeys injected with cadmium-selenide quantum dots. The findings showed that the" acute toxicity of these quantum dots in vivo can be minimal" with the monkeys remaining in normal health over 90 days. Two monkeys were also kept under observation for an additional year and showed no signs of illness.

While this is good news for that application of nanotechnology in medicine, the authors make it clear that more research is needed to determine the long-term effects of cadmium-selenide quantum dots in primates.

"This is the first study that uses primates as animal models for in vivo studies with quantum dots," said paper coauthor Paras Prasad, UB professor of chemistry and medicine, and executive director of UB's Institute for Lasers, Photonics and Biophotonics (ILPB). "So far, such toxicity studies have focused only on mice and rats, but humans are very different from mice. More studies using animal models that are closer to humans are necessary."

A key point of concern is the fact that most of the potentially toxic heavy metal cadmium was retained in the liver, spleen and kidneys during the the 90-day test period.

"The cadmium build-up, in particular, is a serious concern that warrants further investigation," said Ken-Tye Yong, a Nanyang Technological University assistant professor who began working with Prasad on the study as a postdoctoral researcher at UB.

The research was published online last month in the journal Nature Nanotechnology.

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