Researchers Explore Interaction of Engineered Nanoparticles with Environment and Live Systems

Our understanding of the creation and use of nanomaterials is growing, but so much about our long-term relationship with their tiny component particles remains little understood.

"We know that nanoparticles can be toxic. We know that they can get into living things," says Robert Hamers, a University of Wisconsin-Madison chemistry professor and director of the new Center for Sustainable Nanotechnology. "But in some sense we need to shrink the questions of environmental safety down to the way nanoparticles interact with the individual atoms and molecules of the organisms they encounter."

In partnership with researchers from four Midwestern universities and a national laboratory, Hamers hopes to scale the outer walls of living things — their cell membranes — and watch nanoparticles of various compositions, sizes and shapes knock on the door.

The vantage point is a shift from typical nanotechnology toxicology research.

"A lot of studies have been conducted with whole organisms examining rather severe effects — like death — that only appear at high concentrations," says Joel Pedersen, an environmental chemistry professor in UW-Madison's Soil Science Department. "Some of the more subtle effects are only beginning to be examined."

Pedersen, whose research includes creating layers of molecules that function as a cell membrane, will — with chemists Franz Geiger of Northwestern University and Christy Haynes of the University of Minnesota — provide testing grounds for nanoparticles created by labs run by Hamers and Catherine Murphy of the University of Illinois.

"We will also work with two freshwater organisms, the water flea Daphnia and a bacterium called Shewanella oneidensis, to watch their genomic response to nanoparticles. Their genetic readouts after exposure will give us more clues to which molecules the nanoparticles are interacting with once they are inside the organisms," says Pedersen, who has conducted studies of nanoparticle uptake in zebra fish. University of Wisconsin-Milwaukee ecologist Rebecca Klaper is developing genetic markers to track changes in aquatic organisms exposed to water contaminants like nanoparticles.

At a National Science Foundation-sponsored workshop he organized last year, Hamers and other leaders in the field laid out some of the obstacles in the way of a deeper understanding of nanotechnology's environmental footprint.

"One of the things that came up repeatedly was the need for more analytical tools that can tell us what our nanoparticles are doing inside an organism or in any environment, really," Hamers says.

First among those tools may be a way to see on the nanoscale — particles less than 10 nanometers (each a billionth of a meter) long — when that length is just a fraction of the wavelength of light.

"There are tricks you can play to get instruments down to about 10 nanometers of spatial resolution," Hamers says. "Galya Orr from Pacific Northwest National Laboratory is a real expert in this state-of-the-art sub-diffraction microscopy. We'll be exploring some of those to see how we can actually produce images of what a 10-nanometer or 5-nanometer nanoparticle is doing inside a Shewanella cell or a Daphnia."

The group will start with relatively stable diamond and gold nanoparticles, with hopes to move into monitoring slipperier reactive nanoparticles should their three-year, $1.75 million Phase I Center for Chemical Innovation grant transition to a Phase II center with greater funding.

"One of the key limitations in understanding what happens to nanoparticles in the environment and organisms is that the nanoparticles are not static. They're dynamic," Hamers says. "It gets very difficult to track what's going on if the particles are changing as you're going. We will use very small, ultra-stable nanoparticles of diamond and gold, and vary the exterior surfaces with molecular groups that will control the interactions and enable us to follow what happens when they are interacting with organisms in a controlled environment."

The Center for Sustainable Nanotechnology represents a collaborative environment that NSF is encouraging through competitive, tiered processes like the Center for Chemical Innovation grants.

"Understanding how engineered nanoparticles interact with the environment and with living systems is a complex, challenging and important chemical question," says Katharine Covert, CCI program director in NSF's Division of Chemistry. "Hamers has assembled a team of talented scientists willing to tackle this grand challenge."

And Hamers has brought them together to do more than just pass materials and technology back and forth.

"I can't just make nanoparticles and throw them over a fence to somebody. That just doesn't work. It's important for this to be a real collaboration," he says. "One of the unique features of the center is that it provides new modes of training for graduate students, and begins to draw a very strong group of scientists together on an issue of real importance to us. We're ideally suited near the Great Lakes to be studying the implications for freshwater organisms."