April 1, 2008 -- The job market for military working dogs is about to shrink: Scientists have created an artificial "nose" that sniffs out the explosive TNT with genetically engineered viruses.
The eNose, which will probably first be used to protect soldiers and identify terrorists, is based on a technology that has a whole host of potential uses. In the consumer landscape, the eNose could offer sniff tests against allergens or help foodies match a meal with the perfect wine.
"We use the similar approach and materials that nature uses for smell sensing," said Seung-Wuk Lee, a professor of bioengineering at the University of California, Berkeley, and an author of a recent paper describing the technology, which appeared in the journal Langmuir.
The scientists created the eNose by coating a virus with billions of specialized proteins, in different combinations. Each of the proteins, much like the antibodies produced by the human immune system, recognizes and responds to a different substance upon exposure.
Among the multitude of modified viruses, the scientists found a few that recognize TNT and injected them into bacteria. Inside their hosts, the viruses replicated, creating millions of TNT-sensitive clones. The researchers then took those viral sentries and embedded them into a Jello-like hydrogel, which can be used to test for TNT.
The virus can only infect bacteria and is harmless to humans. Lee notes that the Food and Drug Administration recently approved the use of similar viruses to kill deadly bacteria, such as e.coli, in food.
While other available sensors detect a range of chemicals, from explosives to bad food, nearly all suffer from high numbers of false positives, which trigger an alarm when there is no problem and limit their use.
The key to the eNose, notes Lee, is its high selectivity, which makes it more accurate and triggers fewer false alarms.
The researchers also note the eNose could be used for more everyday tasks, such as matching food with wine or detecting peanuts in food for children who could die from a peanut allergy.
Wine, explosives, peanuts -- all contain volatile organic compounds, or VOCs, that are constantly released into the air. Our noses, and the eNose, detect them. Anything that releases VOCs -- in other words, anything with an odor -- the eNose could theoretically be designed to detect.
But national security comes first, say the developers of eNose.
"Achieving chemical selectivity has been a major challenge, especially for detection of small molecules such as TNT in vapor," said Thomas Thundat, a scientist at the Oak Ridge National Laboratory who develops miniature sensors that detect explosives. Thundat estimates that it will be two to three years before the technology is widely used.
"Introducing inexpensive sensors that can be mass produced will cut down the terrorist threats," said Thundat. "Right now terrorists have a huge economic advantage."
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