Scientists have come up with a new way to sniff out hidden explosives. They did it using something many of us have in the kitchen cupboard -- yeast. This ScienCentral News video has more.
Stinky Bombs
Anyone who traveled by plane this past holiday week witnessed the trouble the Transportation Security Administration crews take to enforce the crackdown on carry-on liquids, as 30-gallon trash bin after 30-gallon trash bin were filled with discarded spring water, hair products and cosmetics. But there may soon be a more efficient way of protecting ourselves against concealed explosive ingredients in not just liquids, but even in the air.
And the new method uses something that makes bread "explode" -- yeast cells.
Temple University researchers Venkat Radhika (left) and Danny Dhanasekaran (right) developed yeast that could "sniff out" explosives.
Using his experience in how biological cells communicate with each other, Dhanasekaran, a professor at Temple University, came up with a way to use yeast to detect explosives. While we typically use yeast for baking bread or making homemade beer, yeast is also used in research because of its simple, unicellular structure. "A simple system like yeast can be genetically altered using biotechnology so that it can behave exactly like [a] nose," Dhanasekaran says.
Since rats have a super sense of smell, Dhanasekaran's team took the genetic building blocks from a rat's nose and placed them into yeast. Rats can detect DNT, a component of TNT. Residues of DNT are also picked up by bomb sniffing dogs and electronic detection systems. Dhanasekaran thought that by using the genetic code for the olfactory glands of the rat, he could create a system for detecting a whole library of smells. "Whether it is cheese or DNT, it is a chemical molecule. One is your favorite chemical molecule, in the case of explosive, it's something [the rat] tries to avoid."
The team identified the specific gene in the rat nose for DNT detection, and constructed an elaborate "circuit" inside the cell to alert them when it detected DNT. "[We took] these building blocks from the rat and put them into the yeast," he says.
But while the olfactory building blocks recognize an explosive compound and send a signal to other building blocks, there was another challenge with using yeast. "In the case of rat, there is a brain which processes the signal so you know it is a smell. In the case of yeast, it doesn't have a brain," says Dhanasekaran.
Dhanasekaran looks at a vial of yeast cells that have been bioengineered to detect DNT, a component of TNT.
So the scientists added a special ingredient to make the yeast glow green when it detects DNT; a well-known protein from jellyfish. "It is more like putting a 60 watt bulb at the end so that when the first building block is turned on, this light ... flashes," he says.
As he wrote in Nature Chemical Biology, the engineered yeast can detect small amounts of the explosive in liquid. While this detection distance is very small, at the scale of inches, Dhanasekaran says that since they've engineered an "artificial nose" from yeast, he'll be able to take the detection to much farther distances. "If somebody sprays perfume, you can smell it," he says. "If you remember how sensitive the nose is, based on your experience, you can smell such a faint smell, a faint whiff of fragrance, food, and things like that."
Now they're using this yeast to develop an air sniffer the size of a PDA that could sniff explosives from up to 300 feet away. This could offer advantages to other electronic detectors that have been recently developed. Dhanasekaran, whose research is funded by the Defense Advanced Research Projects Agency (DARPA) , says that he has spoken to soldiers that have been frustrated by the weight of detection equipment today, typically around six pounds. "Six pounds is not a big deal, but you are wearing body armor and you are in a very hostile environment," he says. "That's one of the concerns that the defense department has, the portability of sensing equipment."
He envisions placing the yeast on a thin cartridge that can be "activated" by peeling back a strip of film. Since the yeast is a biological system, the cartridge would need to be replaced every 15 days or so. But the slide could fit into a PDA-like detection system weighing ounces, not pounds. "You can leave it in the airport or you can leave it on a highway ... and immediately as soon as [the explosive] comes you can monitor it from far away," he says.
The researchers hope to use the bomb sniffing yeast for handheld detectors.
Not only could this detector be a key tool for TSA agents inspecting luggage in airports, but Dhanasekaran says that you could make the bomb-sniffing yeast a part of the airport itself. "In the walkways, you can have strips of this yeast," he says. As soon as someone walks by with explosive material, an alert could be triggered.
After successfully constructing this circuitry in the yeast cell, Dhanasekaran says that they plan to detect other hazardous agents. "The yeast can easily be adapted to detect other agents as well ... nerve gas and other toxic agents," Dhanasekaran says. He even envisions a day where emergency responders could carry around packets of special dried yeast. By wetting it, they could use it as an instant detector of harmful substances.
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