Investigators at the National Institute of Standards and Technology decided to take a look at whether two types of quantum dots (carboxylated and biotinylated ones) can be transferred up a food chain, and whether they tend to biomagnify as they go toward the top of the pyramid. The answer on question of transfer is yes. Regarding biomagnification, the answer seems to be no.
In their study, the NIST team investigated the dietary accumulation, elimination and toxicity of two types of fluorescent quantum dots using a simple, laboratory-based food chain with two microscopic aquatic organisms—Tetrahymena pyriformis, a single-celled ciliate protozoan, and the rotifer Brachionus calyciflorus that preys on it. The process of a material crossing different levels of a food chain from prey to predator is called “trophic transfer.”
Quantum dots are nanoparticles engineered to fluoresce strongly at specific wavelengths. They are being studied for a variety of uses including easily detectable tags for medical diagnostics and therapies. Their fluorescence was used to detect the presence of quantum dots in the two microorganisms.
The researchers found that both types of quantum dots were taken in readily by T. pyriformis and that they maintained their fluorescence even after the quantum dot-containing ciliates were ingested by the higher trophic level rotifers. This observation helped establish that the quantum dots were transferred across the food chain as intact nanoparticles and that dietary intake is one way that transfer can occur. The researchers noted that, “Some care should be taken, however, when extrapolating our laboratory-derived results to the natural environment.”
“Our findings showed that although trophic transfer of quantum dots did take place in this simple food chain, they did not accumulate in the higher of the two organisms,” says lead author David Holbrook. “While this suggests that quantum dots may not pose a significant risk of accumulating in aquatic invertebrate food chains in nature, additional research beyond simple laboratory experiments and a more exact means of quantifying transferred nanoparticles in environmental systems are needed to be certain.”
Abstract: Trophic transfer of nanoparticles in a simplified invertebrate food web Nature Nanotechnology doi:10.1038/nnano.2008.110
Full story: Research Measures Movement of Nanomaterials in Simple Model Food Chain…