What’s the News: The next generation of bomb detectors may come from an unusual source: bee venom, the stuff that hurts like all get-out when you get stung. A team of researchers at MIT have used fluorescent carbon nanotubes and venom proteins called bombolitins
that bind to single molecules of explosives like TNT to create an exquisitely sensitive detector. How the Heck:
The team already has a lot of experience building detectors from carbon nanotubes. Their method is to coat a naturally fluorescent nanotube with proteins that bind to whatever they’re trying to detect—their previous targets have included nitric oxide, the nerve gas sarin, and hydrogen peroxide. Once the target binds to the proteins on the nanotube, the light the tube emits can either brighten or change wavelengths, depending on how they’ve set up the system.
In this sensor, when molecules of nitroaromatic explosives like TNT bind to the bee proteins, the tubes change the wavelength they emit, which the lead researcher points out is easier to detect accurately than a change in brightness. The sensor also detects two nitroaromatic pesticides, which suggests it could used for environmental purposes.
Even a single molecule of explosive is enough to set the sensor off, meaning that it’s extremely sensitive, moreso than the detectors currently used in airports, which use spectrometry to identify compounds.
Why bees? Well, we’re not really sure—this is the first time anyone’s studied this aspect of these proteins before, and why bee venom might have proteins that bind to nitroaromatics is still up in the air.
What’s the Context:
Since 9/11, bomb detectors using everything from worms to plants have been suggested. But this bee-venom strategy seems closer to application than most, not to mention more practical: the plants took hours to register the presence of explosives, which could make that detector moot, if the bomb's already exploded.
For more about how the wavelength change works, read up on solvatochromism—how the polarity of a solvent changes the color a substance emits.
Not So Fast: The color change is only detectable with a specially built microscope, so there’s a lot of work still to be done before any commercial applications are possible. Reference: Daniel A. Heller, George W. Pratt, Jingqing Zhang, Nitish Nair, Adam J. Hansborough, Ardemis A. Boghossian, Nigel F. Reuel, Paul W. Barone, and Michael S. Strano. Peptide secondary structure modulates single-walled carbon nanotube fluorescence as a chaperone sensor for nitroaromatics. PNAS, May 9, 2011 DOI: 10.1073/pnas.1005512108
Image credit: nickodoherty/flickr