Curry: Now Good for Detecting Explosions, Not Just Causing Them

by Katie Pratt

Growing up, curry night was always one of my favorite family dinners. Mum would throw together an Indian chicken jalfrezi with rice and poppadums and mango chutney. Delicious! But little did I know that hidden in that curry was a multi-talented chemical.

One of the main ingredients in curry powder is turmeric. Turmeric powder is derived from the root of Curcuma longa, a perennial plant of the ginger family. While its leaves and roots are used fresh in the parts of southern Asia where it grows, in the west it is generally only found as a powder made from the dried root. It has a peppery, mustardy taste, but is used more for its bright yellow color. The molecule responsible for this color is curcumin, and it is rapidly rising to fame in various areas of scientific research.

Turmeric has been used for centuries for a variety of purposes besides the culinary, including medicinal applications that we are finally starting to understand. Indeed the last few years have seen reports published detailing the effects of curcumin in the treatment of Alzheimer’s and cancer, and more generally in the treatment of inflammation.

But most recently curcumin has hit the headlines due to its ability to “sniff out” bombs. As a polyphenol it has the natural capacity to absorb and emit light at certain wavelengths. And these qualities can be modified in a number of ways. Perhaps the best-characterized way is in the use of curcumin as a pH indicator. In acidic solutions it appears yellow, whereas in basic solutions above pH 8.6 it looks bright red. Therefore, in this instance it is its environment that influences the wavelength of colored light that curcumin emits.

The fluorescence signatures of various molecules can also be changed through the covalent attachment of other chemical groups. Last week, at the American Physical Society meeting in Dallas, TX, Abhishek Kumar presented his newest research into the exploitation of curcumin Kumar and his team at U.Mass, Lowell, have developed a way to use its optical properties to detect very low levels of the explosive TNT.

Down boy - wrong explosion.

Currently the most commonly used means of bomb detection is trained sniffer dogs. In fact for the last 20 years explosive manufacturers have been required to include “taggant” molecules that make explosives more easily detectable by trained animals. But the use of dogs has its limitations, particularly in the detection of the 60-70 million land mines that the US State Department estimates are currently deployed around the world. Therefore the development of a sensitive, portable, and cheap device that can detect explosives would be extremely useful (not to mention lucrative).

And that’s what Kumar and his colleagues have done. Basically, curcumin was conjugated to a chemical previously known to bind tightly to TNT. In the absence of the explosive it was able fluoresce normally, but with TNT bound its fluorescence measurably diminished. The researchers have made significant progress in turning this into a very useful bomb-detection tool by immobilizing the modified curcumin in a gel-like substrate on a small chip, and the light needed to generate fluorescence is provided by an L.E.D. In addition, by changing the groups conjugated to curcumin different explosive molecules can be detected. Work is ongoing to increase the sensitivity of these devices, but it is hoped they will be ready to use in the field in the near future.

So next time you’re tucking into your vindaloo, remember that turmeric could be serving a bigger purpose. Or not, depending on how much you love curry…

Katie Pratt is a graduate student in Molecular Biology at Brown University. She has a passion for science communication, and in an attempt to bring hardcore biology and medicine to everyone, she blogs jargon-free at www.katiephd.com. Follow her escapades in the lab and online on Twitter.

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