SPINACH: A BOMB-DETECTING SUPERFOOD

To detect explosive compounds, researchers have designed plants that communicate with us. Scientists from MIT added carbon nanotubes to spinach plant leaves, causing the plants to emit infrared light when they’re near nitroaromatics, compounds often used in explosives. Researchers believe their augmented plants represent early successes in an emerging ield called plant nanobionics, which could fundamentally change the way we detect bombs, droughts, toxins and more.

GIVING PLANTS SUPERPOWERS

The same team debuted this technology a few years ago when it used nanoparticles embedded in plant leaves to detect nitric oxide, a hallmark of pollution. Since then, these scientists have developed polymers that bind to a variety of molecules, including hydrogen peroxide, TNT and sarin, a potent nerve toxin. They wrap their custom polymers around carbon nanotubes and apply them as a solution to the undersides of leaves. The nanotubes are then absorbed into the mesophyll, a part of the plant involved in photosynthesis, where they are exposed to all the chemicals lowing through the plant. The researchers used spinach plants, but the same technology could work on any plant, they say.

Plants have a highly developed vascular system that distributes water and nutrients from the roots to the tip of the stem. They also are highly sensitive to minute environmental changes, necessary for responding to impending catastrophes such as droughts.

Everything the plant absorbs cycles through its system, and molecules absorbed by the roots or leaves will eventually make their way to the nanotubes sitting in the spinach plants’ leaves. In this iteration of the project, when nitroaromatics were present, they attached to the nanotube. This caused the structure to luoresce differently when a laser was trained on it, emitting near-infrared radiation picked up by a nearby camera. A computer attached to the camera registered the presence of a dangerous compound and sent out an email alert warning of a possible threat.

“This is a novel demonstration of how we have overcome the plant/human communication barrier,” Michael Strano, a professor of chemical engineering at MIT and co-author of the study, says in a news release. The team published its research in Nature Materials.

STILL IN EARLY STAGES

There are still a few kinks to work out. The team didn’t conduct trials using solely airborne compounds, which presumably would be how most commercial applications of this technology would need to operate. The researchers also didn’t reveal the minimum concentration of nitroaromatic compounds needed to trigger a detection, so it’s unclear how sensitive their plants are.

The researchers say their system takes about 10 minutes to detect the presence of nitroaromatics when they are added to the roots, and the infrared sensor works from up to a meter away, although they hope to boost that range in the future. They have also increased the detector’s reliability by adding in separate nanotubes that constantly luoresce, which they say helps avoid false-positive detections.

Written by Nathaniel Scharping in "Strange Science" USA, Fall 2018, excerpt p.14. Digitized, adapted and illustrated to be posted by Leopoldo Costa.