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Posted on January 11, 2010 by  & 

Carbon nanotubes detect toxins in drinking water

Clean water is one of the most pressing needs in developing countries. Despite the fact that there are many methods to evaluate water quality, finding a quick, simple low-cost method for detection of toxins is still a challenge.
Microcystin-LR is a chemical compound produced by cyanobacteria, or blue-green algae found in freshwater reservoirs in places like Northern Thailand, where a high proportion of the population consume untreated surface water. Even in small quantities, Microcystin is suspected of causing liver damage and possibly liver cancer. Scientists at Michigan University may soon be able to detect the toxin quickly and cheaply with the development of a new biosensor, using a strip of paper infused with carbon nanotubes.
The sensor works by measuring the electrical conductivity of the nanotubes in the paper. Before the nanotubes are impregnated in the paper, they are mixed with antibodies for MC-LR. When the paper strips come in contact with water contaminated with MC-LR, those antibodies squeeze in between the nanotubes to bond with the MC-LR. This spreading apart of the nanotubes changes their electrical conductivity.
An external monitor measures the electrical conductivity. The whole device is about the size of a home pregnancy test with results appearing in fewer than 12 minutes. The process is 28 times faster than the complicated method most commonly used today to detect microcystin-LR.
The substance and others like it are among the leading causes of biological water pollution. It is believed to be a culprit of mass poisonings going back to early human history, said Nicholas Kotov, a professor in the departments of Chemical Engineering, Biomedical Engineering and Materials Science and Engineering who led the project.
Water treatment plants even in developed countries like the US can't always remove MC-LR completely, nor can they test for it often enough. The biosensor Kotov and his colleagues developed provides a quick, cheap, portable and sensitive test that could allow water treatment plants and individuals to detect multiple toxins, verifying the safety of water on a more regular basis.
The technology could also be adapted to detect a variety of harmful chemicals or toxins in water or food. To adapt the biosensor for other toxins, Kotov said, scientists could simply replace the antibodies that bond to the toxin.
The research was in collaboration with the laboratory of Professor Chuanlai Xu at Wuxi University in China.
The university is now pursuing patent protection for the intellectual property, and is seeking commercialization partners to help bring the technology to market.

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Business Development Director, Research

Posted on: January 11, 2010

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