Nature Nanotech. doi:10.1038/nnano.2008.110 (2008)

Those who worry about nanotechnology do so partly because of its potential environmental impact. So David Holbrook and a team from the US National Institute of Standards and Technology, in Gaithersburg, Maryland, have tested whether quantum dots (tiny blobs of semiconducting material) accumulate in a simple invertebrate food web.

Over a series of experiments, they put bacteria (Escherichia coli), rotifers (Brachionus calyciflorus) and ciliates (Tetrahymena pyriformis) in flasks with carboxylated and biotinylated quantum dots, which may find a use in computing and solar cells.

The nanomaterials could only stick to clumps of bacterial cells — aggregates too large for ciliates to gobble. However, ciliates took up quantum dots directly from the media, retaining the biotinylated dots for more than twice as long as the carboxylated ones. Rotifers, which eat ciliates, thus consumed quantum dots, but emptied the dots from their guts fast enough to avoid accumulating them.