Tracey Bryant



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.


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, a premier research center at the University of Delaware.

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.

Nanoparticles are bits of chemicals a thousand times smaller than a human
cell. While nanoparticles occur naturally in the environment, they
increasingly are being manufactured for use in electronics to cosmetics,
fuel cells to medical procedures.

Yet the human and environmental health risks associated with these tiny
engineered particles are not well known. 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.?

Xiao, who directs the Center for Spintronics and Biodetection at the
University of Delaware, noted that the magnetometer used in his physics
research is similar to magnetic resonance imaging (MRI), which uses a
powerful magnetic field and radio-frequency pulses to produce images of
internal structures in the human body.

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.

Additionally, while the pumpkins were studied primarily in aqueous media,
the researchers also tested the plants in sand to which nanoparticles were
added, where there was little uptake, and in soil, where there was no uptake
of nanoparticles at all, according to Jin.

Jin noted how important interdisciplinary collaboration has been to the
research and said she hopes to see plant scientists and molecular biologists
involved in future studies to see how nanoparticles actually get into
plants.

?Some believe it is a passive process; others are convinced it is an active
one,? Jin said. ?There could be whole other lines of research,? she noted.

?It's like a saying we have in Chinese,? Jin added. ?You throw out a brick
and hope to attract a jade.?

The saying, which is a Chinese way of showing humility, demonstrates the
speaker's hope that others will improve on an idea.

?We want to stress that our study is very preliminary, and we hope it will
stimulate more research in this area,? she said.

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.

www.checkbiotech.org