Delaware Study: Plants Can Accumulate Nanoparticles in Tissues

Researchers at the University of Delaware have provided what is believed to be the first experimental evidence that plants can take up nanoparticles and accumulate them in their tissues, according to a Nov. 11 press release.

The laboratory study, which involved pumpkin plants, indicates a possible pathway for nanoparticles to enter the food chain. The research also reveals a new experimental approach for studying nanoparticles and their potential impacts.

Yan Jin, professor of soil physics in the University of Delaware College of Agriculture and Natural Resources, and John Xiao, professor of physics and astronomy in the College of Arts and Sciences, led the study, working with colleagues Jung-youn Lee and Harsh Bais at the Delaware Biotechnology Institute.

The results were published in a cover article in the Journal of Environmental Monitoring and also were highlighted in Chemical Biology, a journal of the Royal Society of Chemistry.

Because chemical compounds can take on different properties at such a reduced size--lead in a pencil reportedly becomes stronger than steel, for example--there is concern that these invisible particles could easily be breathed in by humans and animals, with damaging or toxic effects.

"Plants serve as a foundation of the food chain," noted Jin, who was recently named a fellow of the Soil Society of America. "We demonstrated this possible route for nanoparticles in the environment--whether it poses potential harm to human health depends on many factors. This is a preliminary study, which we hope will spur additional interdisciplinary research by the scientific community."

The researchers chose pumpkins for the study, Jin said, because they take in a lot of water and are easy to grow.

The plants were grown hydroponically in an aqueous medium to which nanoparticles of iron oxide, or magnetite, a magnetic form of iron ore, were added.

After 20 days of growth, the plants were cut into pieces and dried in a vacuum dessicator. A magnetometer was then used to detect if any of the particles had been absorbed by the plant.

"Our study was a worst-case scenario in order to test the feasibility of our approach in being able to detect the particle," Xiao noted. "It really provides a new technique for doing this kind of research."

The magnetometer subjected the dried pumpkin plants to a low-frequency monotone to vibrate them. The vibration revealed each tiny particle of magnetite's unique magnetic signal and, thus, exact location inside the plant.

The researchers noted that in their initial screening tests, no magnetic signals were detected in lima bean plants compared to the strong signals in pumpkin plants, which suggests that different plants have varied responses to nanosized particles.

The project was funded by the Delaware Experimental Program to Stimulate Competitive Research (EPSCoR), which is supported by the National Science Foundation and the state of Delaware.

Jin and Xiao also recently won a STAR grant from the Environmental Protection Agency to examine the fate and transport of engineered nanoparticles in porous media, including soil and groundwater.

For more information, visit http://www.udel.edu/udaily/2009/nov/pumkpkins111108.html.

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