Cyborg seedlings grow new field of science
There is no doubt that plants are excellent, but a team of MIT engineers are looking to cutting-edge materials to make them even better.
The researchers want to augment the physical structure of plants using nano-scale materials, embedding them with advanced technology to bring some amazing new functions.
The futuristic flora could feature enhanced energy production or even have the ability to monitor environmental pollutants.
In a new Nature Materials paper, researchers report boosting plants’ ability to capture light energy by 30 per cent, by embedding carbon nanotubes in the part of the plant where photosynthesis takes place; the chloroplast.
In later tests, a different nanotube configuration modified the plants to detect the gas nitric oxide.
The developments have launched a new scientific field that the MIT team has dubbed “plant nanobionics”.
“Plants are very attractive as a technology platform,” says Michael Strano, a professor of chemical engineering and leader of the MIT research team.
“They repair themselves, they're environmentally stable outside, they survive in harsh environments, and they provide their own power source and water distribution.”
The nano-scale developments came out of an earlier quest to improve the photosynthetic ability of plants, for possible integration into solar power systems.
Chloroplasts host all of the machinery needed for photosynthesis, which occurs in two stages.
In the first stage, special pigments absorb light, which excites electrons that flow through membranes of the chloroplast. The plant captures this electrical energy and uses it to power the second stage of photosynthesis — building sugars that feed and sustain the plant.
The researchers embedded semiconducting carbon nanotubes, coated in negatively charged DNA, into the chloroplasts.
Plants typically make use of only about 10 percent of the sunlight available to them, but carbon nanotubes appear to extend their view.
This allowed the chloroplasts to capture wavelengths of light not in their normal range, such as ultraviolet, green, and near-infrared.
With carbon nanotube enhancements, the plants’ photosynthetic activity — measured by the rate of electron flow through the thylakoid membranes — was 49 percent greater than that in chloroplasts without embedded nanotubes.
The researchers then turned to living plants (rather than isolated chloroplasts) and used a technique called vascular infusion to deliver nanoparticles into Arabidopsis thaliana, a small flowering plant.
Using this method, the researchers applied a solution of nanoparticles to the underside of the leaf, where it penetrated tiny pores known as stomata, which normally allow carbon dioxide to flow in and oxygen to flow out.
In these plants, the nanotubes moved into the chloroplast and boosted photosynthetic electron flow by about 30 percent.
The researchers also showed that they could turn Arabidopsis thaliana plants into chemical sensors by delivering carbon nanotubes that detect the gas nitric oxide, an environmental pollutant produced by combustion.
When the target molecule binds to a polymer wrapped around the nanotube, it alters the tube's fluorescence.
By adapting the sensors to different targets, the researchers hope to develop plants that could be used to monitor environmental pollution, pesticides, fungal infections, or exposure to bacterial toxins. They are also working on incorporating electronic nanomaterials, such as graphene, into plants.
“Right now, almost no one is working in this emerging field,” postdoctorate and plant biologist Juan Pablo Giraldo said.
“It's an opportunity for people from plant biology and the chemical engineering nanotechnology community to work together in an area that has a large potential.”