Researchers are hoping a new biosensor may help farmers and regulatory officials detect herbicides in soil and water samples. The device relies on living organisms or their byproducts to identify traces of chemical residues in a matter of minutes.
Heavy applications of herbicides can leave environmentally unsafe residues in soil and water. The biosensor is made of a chlorophyll-protein complex--the green proteins in plants used for photosynthesis--fixed on electrodes that specifically measure oxygen levels. The complex produces oxygen in the presence of certain chemicals and light.
A liquid sample is passed through the biosensor. If the sample contains a herbicide, the chemical will react with the biosensor's proteins and inhibit oxygen production. The electrode in the biosensor detects oxygen levels and sends the information to a computer that displays the data in graph form.
The test is ultrasensitive and works well at room temperature or above. But "the chlorophyll-protein complex from plants such as potatoes, peas, and broad beans can't withstand high temperatures, so they are unsuitable for use as biosensors," says molecular biologist Autar K. Mattoo who heads the Agricultural Research Service Vegetable Laboratory in Beltsville, Maryland.
The new device instead uses a protein complex from a particular cyanobacteriuma bacterium that can fix carbon dioxide in the presence of light and can grow at very high temperatures--that isn't inactivated at warmer temperatures a user might encounter in the field.
"If a biosensor is to be used repeatedly, especially in the field, it requires a biosensing device that is stable at ambient temperatures and doesn't require cooling," says Mattoo.
The new biosensor is easy to use and economical--distinct advantages over currently available herbicide detectors. "Other sensors are reliable," says Mattoo. "But they require expensive equipment and lab analysis, limiting the number of samples that can be analyzed."
This biosensor can run repeated tests in the field. The scientists are working on a miniaturized commercial version that should be available within the next 2 to 3 years. Mattoo co-developed the biosensor with scientists from the Czech Republic and Italy through a grant supported by the North Atlantic Treaty Organization. More detailed information about this research will soon be published in the journal "Biotechnology and Bioengineering."--By Tara Weaver, Agricultural Research Service Information Staff.
"Biosensor Detects Chemical Residues" was published in the November 1998 issue of Agricultural Research magazine. Click here to see this issue's table of contents.