[tt] 'Buckyballs' Have High Potential To Accumulate In Living Tissue

[Eugen Leitl]

http://www.sciencedaily.com/releases/2008/09/080918171148.htm

'Buckyballs' Have High Potential To Accumulate In Living Tissue

ScienceDaily (Sep. 19, 2008) — Research at Purdue University suggests
synthetic carbon molecules called fullerenes, or buckyballs, have a high
potential of being accumulated in animal tissue, but the molecules also
appear to break down in sunlight, perhaps reducing their possible
environmental dangers.

Buckyballs may see widespread use in future products and applications, from
drug-delivery vehicles for cancer therapy to ultrahard coatings and military
armor, chemical sensors and hydrogen-storage technologies for batteries and
automotive fuel cells.

"Because of the numerous potential applications, it is important to learn how
buckyballs react in the environment and what their possible environmental
impacts might be," said Chad Jafvert, a professor of civil engineering at
Purdue.

The researchers mixed buckyballs in a solution of water and a chemical called
octanol, which has properties similar to fatty tissues in animals. Jafvert
and doctoral student Pradnya Kulkarni were the first to document how readily
buckyballs might be "partitioned," or distributed into water, soil and fatty
tissues in wildlife such as fish.

Findings indicated buckyballs have a greater chance of partitioning into
fatty tissues than the banned pesticide DDT. However, while DDT is toxic to
wildlife, buckyballs currently have no documented toxic effects, Jafvert
said.

"This work points out the need for a better understanding of where the
materials go in the environment," he said. "Our results show they are going
to be taken up by fish and other organisms, possibly to toxic levels. This,
however, indicates only the potential of buckyballs to bioaccumulate. They
could break down in the environment or in an organism once taken up."

Researchers do not yet know whether buckyballs will break down in the
environment or will be metabolized by animals, which would reduce the risk of
accumulating in fatty tissues.

"For example, we don't bioaccumulate sugars because we process sugars, but we
do bioaccumulate other compounds that we don't metabolize," Jafvert said. "If
we have the ability to metabolize buckyballs, we won't bioaccumulate them."

Findings were detailed in a research paper that appeared in August in the
journal Environmental Science and Technology. The paper was written by
Jafvert and Kulkarni.

The researchers determined the "octanol-water partition coefficient," which
enables them to show how readily buckyballs would be partitioned.

"The bottom line is, if buckyballs partition favorably from water to octanol,
they are also likely to partition favorably from water to fatty tissues,"
Jafvert said.

The researchers also are investigating whether sunlight breaks down
buckyballs and other structures called carbon nanotubes, which also could
have widespread industrial applications.

"We need to learn how reactive these materials are in the environment,"
Jafvert said. "Do they break down? What kinds of products do they form? We
have learned so far that buckyballs absorb light, and they do photoreact.
That's potentially a good thing because it means it won't hang around for a
long period of time, reducing the exposure concentration, which would then
reduce any potential toxicity that it may or may not have."

Named after architect R. Buckminster Fuller, who designed the geodesic dome,
buckminsterfullerenes, or buckyballs, are soccer-ball-shaped molecules
containing 60 carbon atoms. A buckyball has a width of about 1 nanometer, or
one-billionth of a meter, which is roughly 10 atoms wide.

The researchers determined precisely how soluble the buckyballs are in water
and confirmed that the molecules form clusters, which complicates efforts to
understand how they might be dispersed by water in the environment.

"Typically, buckyballs are not found in water because their solubility is so
low, but the same could be said of DDT," Jafvert said. "DDT is found in
sediment, so you would assume buckyballs would also end up in sediments. That
means there is also a chance that marine organisms, like worms that are
eating sediment, are going to be potentially accumulating buckyballs unless
they break down in the environment."

The research is affiliated with the Center for the Environment and the Birck
Nanotechnology Center at Purdue's Discovery Park and is funded by the
Environmental Protection Agency and the National Science Foundation through
the NSF's Nanoscale Interdisciplinary Research Team, or NIRT. The work is
part of a larger NIRT project at Purdue involving researchers in agronomy,
civil engineering, agricultural and biological engineering, mechanical
engineering, food science, and earth and atmospheric sciences.

Adapted from materials provided by Purdue University.