Can spinach be used to detect bombs?

Spinach that can detect explosives and wirelessly relay the info to a smartphone-like device? Now that’s a superfood.

MIT scientists have embedded spinach leaves with carbon nanotubes, transforming them into sensors. It’s one of the first demonstrations of “plant nanobionics,” engineering electronic systems into plants.

The plants were designed to detect chemical compounds known as nitroaromatics, which are often used in landmines and other explosives. When one of these chemicals is present in the groundwater sampled naturally by the plant, carbon nanotubes embedded in the plant leaves emit a fluorescent signal that can be read with an infrared camera. The camera can be attached to a small computer similar to a smartphone, which then sends an email to the user.

"This is a novel demonstration of how we have overcome the plant/human communication barrier," Michael Strano, Carbon P. Dubbs Professor of Chemical Engineering at MIT and the leader of the research team, said in an MIT release. who believes plant power could also be harnessed to warn of pollutants and environmental conditions such as drought.

Plants are ideally suited for monitoring the environment because they already take in a lot of information from their surroundings, said the researcher. With extensive root networks in the soil, plants are constantly sampling groundwater, making them very good analytical chemists.

"Plants are very environmentally responsive," Strano said. "They know that there is going to be a drought long before we do. They can detect small changes in the properties of soil and water potential. If we tap into those chemical signaling pathways, there is a wealth of information to access."

For the study, the researchers embedded sensors for nitroaromatic compounds into the leaves of spinach plants. They used a technique called vascular infusion, which involves applying a solution of nanoparticles to the underside of the leaf. They also embedded carbon nanotubes that emit a constant fluorescent signal that serves as a reference. This allows the researchers to compare the two fluorescent signals, making it easier to determine if the explosive sensor has detected anything. If there are any explosive molecules in the groundwater, it takes about 10 minutes for the plant to draw them up into the leaves, where they encounter the detector. To read the signal, the researchers shine a laser onto the leaf, prompting the nanotubes in the leaf to emit near-infrared fluorescent light. The results of the study were published in the journal Nature Materials.

In addition to saving lives and limbs from landmines, nanobionics could also help botanists learn more about the inner workings of plants, monitor plant health and maximize the yield of rare compounds synthesized by plants such as the Madagascar periwinkle, which produces drugs used to treat cancer.