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Paper Strips Detect Toxin in Water

Engineers at the University of Michigan led the development of a new biosensor - a strip of paper infused with carbon nanotubes - that can quickly and inexpensively detect a toxin produced by algae in drinking water.

The paper strips perform 28 times faster than the method most commonly used today to detect microcystin-LR, a chemical compound produced by cyanobacteria, or blue-green algae. Cyanobacteria is commonly found on nutrient-rich waters.

Microcystin-LR (MC-LR) is suspected to cause liver damage and possibly liver cancer, and is among the leading causes of biological water pollution.

Water treatment plants can't always remove MC-LR completely, nor can they test for it often enough, said Nicholas Kotov, a professor in the departments of Chemical Engineering, Biomedical Engineering, and Materials Science and Engineering. The biosensor he and his colleagues developed provides a quick, cheap, portable and sensitive test that could allow water treatment plants and individuals to verify the safety of water on a more regular basis.

The technology could easily be adapted to detect a variety harmful chemicals or toxins.


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, and results appear in under 12 minutes.

To adapt the biosensor for other toxins, scientists could simply replace the antibodies that bond to the toxin. The university is pursuing patent protection for the intellectual property, and is seeking commercialization partners to help bring the technology to market.

(University of Michigan)