Not only is spinach a superfood because of its nutritional value, but also because of its ability to detect explosives. Yes, spinach today can tell if there’s a bomb around. MIT engineers have transformed spinach plants into sensors that can detect explosives by embedding their leaves with carbon nanotubes. After sensing dangerous chemicals, the plant will send an alert by wirelessly relaying that information to a handheld device similar to a smartphone.
The researchers are calling this approach of engineering electronic systems into plants, “plant nanobionics.” The spinach example is one of the first demonstrations of this new technology. A paper describing the nanobionic plants was published in Nature Materials. Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and the leader of the research team says:
“The goal of plant nanobionics is to introduce nanoparticles into the plant to give it non-native functions.”
In the case of this demonstration, the spinach plants were designed to specifically detect chemical compounds known as nitroaromatics, which are often used in landmines and other explosives. If any one of the chemicals found in this compound is present in the groundwater the plant will naturally sample it. When the target molecule binds to a polymer wrapped around the nanotube, it alters the tube’s fluorescence.
The carbon nanotubes embedded in the plant leaves will 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. 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. The signal can be picked up from a distance of about 1 meter away from the plant. The research team is now working on increasing that distance.
Strano believes plant power could also be harnessed to warn of pollutants and environmental conditions such as drought. He says:
“This is a novel demonstration of how we have overcome the plant/human communication barrier.”
There was already a previous demonstration (the first experiment) of plant nanobionics where Strano and Juan Pablo Giraldo, a former MIT postdoc who is now an assistant professor at the University of California at Riverside, used nanoparticles to enhance plants’ photosynthesis ability and to turn them into sensors for nitric oxide, a pollutant produced by combustion. Strano says:
“Plants are ideally suited for monitoring the environment because they already take in a lot of information from their surroundings… Plants are very good analytical chemists. They have an extensive root network in the soil, are constantly sampling groundwater, and have a way to self-power the transport of that water up into the leaves.”
So far, they have been able to use the plants to detect a wide range of molecules, including hydrogen peroxide, the explosive TNT, dopamine, and the nerve gas sarin.
Michael McAlpine, an associate professor of mechanical engineering at the University of Minnesota who was not involved in the research says:
“When you have manmade materials infiltrated into a living organism, you can have plants do things that plants don’t ordinarily do. Once you start to think of living organisms like plants as biomaterials that can be combined with electronic materials, this is all possible.”
These sensors are also helpful to botanists. By using them, they could 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. Min Hao Wong, an MIT graduate student who has started a company called Plantea to further develop this technology explains:
“These sensors give real-time information from the plant. It is almost like having the plant talk to us about the environment they are in. In the case of precision agriculture, having such information can directly affect yield and margins.”
No matter how this technology is used, it works well because plants work well. Strano strongly believes in the massive potential of using plants because:
“Plants are very environmentally responsive. 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.”