Carnegie Mellon University
April 15, 2014

Scanning for Silver: Investigating Nanoparticle Absorption in Plants

Scanning for Silver:  Investigating Nanoparticle Absorption in Plants

PhD Student John Stegemeier  and Dr. Clement Levard at CERGE in Aix en ProvencePhD Student John Stegemeier and Dr. Clement Levard at CERGE in Aix en Provence

There might be metal in your gym socks. That’s because nanosilver—silver particles that are a million times smaller than a centimeter on a standard ruler—are being increasingly added to a variety of household products. While its antibacterial properties may be great for keeping sweat socks odor-free, researchers are still working to understand nanosilver’s effects on the environment. As part of this effort, CEE professor Greg Lowry and his PhD student John Stegemeier are studying nanosilver uptake in aquatic plants.

“Nanoparticles in the environment are going to end up in aquatic systems and soil, so one of the key questions right now is: ‘Do aquatic or terrestrial plants take up these nanoparticles?’ If so, they might enter the food web this way,” Lowry explains. Stegemeier has already collected some data suggesting that aquatic plants do absorb nanosilver particles. Now, with the help of a National Science Foundation funded NEEP-IGERT (Integrative Graduate Education and Research Traineeship) travel grant, he is working in France to investigate exactly where within the plants those nanoparticles end up.

In collaborator Clement Levard’s lab, Stegmeier has been growing duckweed, a fairly common breed of aquatic plant. To some batches, he adds a solution that includes silver nanoparticles. He then takes tiny slivers of the duckweed and inserts them into the Nano CT, a machine that uses X-rays to develop a three dimensional picture of each piece. Because silver is about ten times more dense than water—the primary component of duckweed—Lowry says that some high-density areas should be visible in slivers of the plant that contain nanoparticles. 

At least, that’s what he and Stegemeier are hoping—no one has ever used the Nano CT for this purpose before. “We’re pushing the capabilities of this instrument. If it works, it will be the first time anyone has ever done this and more importantly, it will tell us where in the plant root these nanomaterials reside,” he says. 

This work is just a small part of a long-standing working relationship and friendship between Lowry and Levard. Both are members of the Center for Environmental Implications of Nanotechnology (CEINT), a National Science Foundation funded center that combines the expertise of researchers from all over the world. Lowry says that the partnership between CEINT and France’s Centre de Recherche et d’Enseignement de Géosciences de l’ Environnement (CEREGE), where Levard is also a full-time research scientist, has been “particularly fruitful” because the two centers often conduct complementary research projects. 

The information from this particular project will help researchers and eventually government policy makers to evaluate the risks associated with using nanosilver. Lowry says, “Nanotechnology is one of the first technologies where we’re really considering the potential effects as it’s rolled out. We have not yet realized the potential of nanoparticles and we’re trying to provide feedback for safe design."

PhD Student John Stegemeier and Dr. Clement Levard at CERGE in Aix en Provence

PhD Student John Stegemeier collects samples at the CEINT facility