A Massachusetts Institute of Technology research team has embedded nanoparticles into spinach and used infrared light to detect explosives.
Photo courtesy of Rosalie Sinclair

In October 2016, the Massachusetts Institute of Technology (MIT) announced that university engineers had discovered how to detect explosives using spinach.

The peculiarity of the research allowed it to gain considerable media coverage. “Talk about spinach as superfood, Popeye!” wrote the Washington Post. Fox25 News in Boston ran a story with the headline, “Bomb detecting spinach could be the future of anti-terrorism.” NPR’s Science Friday interviewed the research team’s leader, Dr. Michael Strano, in a segment titled, “No Nose, but a Heck of a Sniffer.”

In an interview with Greenhouse Management, Strano, who is the Carbon P. Dubbs professor of chemical engineering at MIT, explains he didn’t have any specific military or industrial applications in mind when conducting the research — which falls under the umbrella of a whole new scientific field he has coined “plant nanobionics.” Strano wanted people to be able to understand the concept that plants can be imparted with non-native functions by inserting nanoparticles into them at specific locations. “We chose explosives because it’s an example of a molecule that is foreign to the plant, and if it shows up in the environment, I think people would understand right away that it’s something foreign. It's a chemical that is obviously important to detect,” he says.

Dr. Michael Strano’s research group has created a new field called plant nanobionics that improves the functions of plants.
Photo courtesy of Rosalie Sinclair

Strano’s research group has been placing nanoparticles in various wild type plants and using infrared light to detect bombs as well as other non-native objects. They have also turned the sensors inside the plants to see what’s happening within them. Already, they have detected dopamine and nitric oxide.

“We think these mechanisms are very generic,” he says. “We have developed methods that can get nanoparticles into the plastid, so it can work with any plant — dicots, monocots — it can work with ornamental plants.”

Strano sees two basic impacts that the new technology can have. First, the sensors turned toward the plants will be able to simplify scientific research and precision agriculture. The second — and even more impactful — vision is that nanoparticle-equipped plants will be able to replace plastics, circuit boards and other technologies used in daily life.

The benefits of boosting botany with bionics

Plant biologists and other scientists will be able to transfer information from plants to their smartphone and other devices, and automate processes that are currently difficult and costly, Strano says. For instance, they will be able to bypass the sampling and grinding of plant tissue and sending it to mass spectrometers and laboratories.

Strano says commercial growers will benefit from plant nanobionics because they will be able to use the sensors to detect an array of plant conditions. Turning the sensors within the plant could allow them to determine the onset of drought, monitor soil-water potential and gauge which nutrients are present.

The MIT lab has functionalized suspended carbon nanotubes, such as those used in the explosive-sensing plant, for sensors.
Photo courtesy of Rosalie Sinclair

The cost for growers to use the technology will be negligible. The bomb-detecting spinach takes about 10 minutes to do its job, and a Raspberry Pi — a handheld mini-computer used in the MIT team’s research — costs about $35. Growers could also detect signals with their smartphones if they remove the infrared filter.

The MIT researchers don’t want to place nanoparticles into plants that are going to be harvested for agriculture, Strano says, although “sentinel plant” use in agriculture dates back hundreds of years or more. “If you go to vineyards in, say, Bordeaux, France, they put a delicate rose at the head of every vine row,” he says. The rose shows symptoms of bacterial infection and other adverse conditions before the grapes do, and warns when infections are present in the vineyard.

“I think, in the 21st century, plant nanobionics is going to give us sentinel plants that tell us an exquisite amount of information,” Strano says. “We’re going to be able to forecast drought, local changes in soil potential, the jasmonate response — we’re able to look at pests. All of this is going to be digital. We’re going to be able to collect data in real time.”

The research team is still collecting information and is interested in partnering with growers, Strano says. If growers have problems or applications, the team would be interested in working with them to develop solutions.

A catalyst for nature’s comeback?

A credit card-sized computer called a Raspberry Pi and a camera that were used in the MIT team’s research
Photo courtesy of Rosalie Sinclair

Strano has his sights set on another goal: using plants as a starting point for creating new technology that can be used in a variety of applications. He says he is the first engineer to do this.

Plants perform functions that outwit human technology, Strano says. “For example, plants harvest energy from the sun — and we have solar panels that do that — but plants harvest energy from the sun and store it as a chemical fuel,” he says. “And they can use that chemical fuel on demand. So, they have their own energy harvesting plus storage. Plus, they use some of that solar radiance to pump water up from the ground. We don’t have human-made analogs to that.”

What’s more, plants have environmental benefits, and they repair themselves, Strano says. “Things that humans make — my iPhone, and my smoke detector at home — they don’t repair themselves,” he says. “They’re actually fairly rigid. So, the larger vision is to start to ask the question, ‘What devices that we currently have can we replace with a living plant?’”

Scientists are also asking how exactly they can perform the required engineering techniques and calculations, Strano says. “These are revolutionary ideas,” he says. “They are outside the bounds of conventional science.”