Engineers at the University of Michigan have developed a biosensor consisting of 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 to detect microcystin-LR (MC-LR), a chemical compound produced by cyanobacteria, or blue-green algae. Cyanobacteria is commonly found on nutrient-rich waters. Even in very small quantities, MC-LR is suspected to cause liver damage and possibly liver cancer. The substance and others like it are among the leading causes of biological water pollution and believed to be a culprit of mass poisonings going back to early human history, says Nicholas Kotov, PhD, project leader and professor in the U-M departments of chemical engineering, biomedical engineering, and materials science and engineering.
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 toxin. This spreading apart of the nanotubes changes their electrical conductivity, which is measured by an external monitor. The whole device is about the size of a home pregnancy test, and results appear in fewer than 12 minutes, Kotov says.
The biosensor provides a quick, cheap, portable, and sensitive test that could allow water treatment plants and individuals to verify the safety of water on a regular basis. “The safety of drinking water is a vital issue in many developing countries and in many parts of the United States,” Kotov points out. “We’ve developed a simple and inexpensive technology to detect multiple toxins.” A paper about the technique appeared online in Nano Letters. The university is pursuing patent protection for the IP and is seeking commercialization partners to help bring the technology to market.
Source: Science Daily