Sludge Watch ==> Nanotechnology - what is the fate of such material in the environment?

[Maureen Reilly]

US: Yale scientists use nanotechnology to fight E. coli
30.aug.07
from a press release
http://www.eurekalert.org/pub_releases/2007-08/yu-ysu083007.php#

New Haven, Conneticut --

Single-walled carbon nanotubes (SWCNTs) can kill bacteria like the common 
pathogen E. coli by severely damaging their cell walls, according to a 
recent report from Yale researchers in the American Chemical Society (ACS) 
journal Langmuir.

“We began the study out of concerns for the possible toxicity of nanotubes 
in aquatic environments and their presence in the food chain,” said Menachem 
Elimelech, professor and chair of chemical and environmental engineering at 
Yale and senior author on the paper. “While nanotubes have great promise for 
medical and commercial applications there is little understanding of how 
they interact with humans and the environment.”

“The nanotubes are microscopic carbon cylinders, thousands of times smaller 
than a human hair that can be easily taken up by human cells,” said 
Elimelech. “We wanted to find out more about where and how they are toxic.”

This “nanoscience version of a David-and-Goliath story” was hailed in an ACS 
preview of the work as the first direct evidence that “carbon nanotubes have 
powerful antimicrobial activity, a discovery that could help fight the 
growing problem of antibiotic resistant infections.”

Using the simple E. coli as test cells, the researchers incubated cultures 
of the bacteria in the presence of the nanotubes for up to an hour. The 
microbes were killed outright – but only when there was direct contact with 
aggregates of the SWCNTs that touched the bacteria. Elimelech speculates 
that the long, thin nanotubes puncture the cells and cause cellular damage.

The study ruled out metal toxicity as a source of the cell damage. To avoid 
metal contaminants in commercial sources, the SWCNTs were rigorously 
synthesized and purified in the laboratory of co-author Professor Lisa 
Pfefferle.

“We're now studying the toxicity of multi-walled carbon nanotubes and our 
preliminary results show that they are less toxic than SWCNTs,” Elimelech 
said. “We are also looking at the effects of SWCNTs on a wide range of 
bacterial strains to better understand the mechanism of cellular damage.”

Elimelech projects that SWCNTs could be used to create antimicrobial 
materials and surface coatings to improve hygiene, while their toxicity 
could be managed by embedding them to prevent their leaching into the 
environment.