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Engineers at MIT have embedded nanoparticles into the leaves of a watercress plant, which induces them to give off a dim light that lasts for a few hours. With further development, the group hopes that these plants will one day be bright enough to illuminate an entire workplace.
The engineers have also discovered a way to switch off this light by adding nanoparticles that contain an inhibitor. Their work appears in the journal Nano Letters.
The vision is to make a plant that will function as a desk lamp. The light is powered by the energy metabolism of the plant itself.
Michael Strano, Professor of Chemical Engineering, MIT
The way the plants glow is by using the enzyme luciferase. Luciferase is the enzyme that is famous for causing the glow of fireflies, and it works by acting on the molecule luciferin. To stop the reaction, co-enzyme A removes the by-product to inhibit the luciferase activity. All of these three molecules were packaged into different nanoparticle carriers that are then put into the plant leaves. The team used 10 nanometer silica nanoparticles for luciferase, and polymers of PLGA and chitosan for luciferin and coenzyme A. The nanoparticle carriers were then suspended with the plants in a solution exposed to high pressure, allowing the particles to enter the leaves through the stomata pores.
Particles that released the luciferin and coenzyme A accumulate in the extracellular space of the mesophyll, while the smaller particles carrying luciferase enter the cells of the mesophyll itself. The PLGA particles release the luciferin into the plant cells, where the luciferase enzymes carry out the chemical reaction to make luciferin glow.
The light generated by the watercress seedlings is currently not strong enough to read by, but the researchers believe they can optimize this by changing the concentrations and release rates of each component. This optimization boosts the amount of light emitted, as well as the duration of light. Early efforts only yielded a 45 minute glow, but now the team have manged to improve that to an impressive three and a half hours.
Previous studies used genetic engineering of plants to express the luciferase gene, but this was found to be a long process that yielded very little light. Those studies were also only performed on tobacco plants and Arabidopsis thaliana, but the method developed by Strano’s lab has shown success with many different plant types. The list of successful plants so far include arugula, kale, spinach and watercress.
Plant nanobionics is a relatively new area of research for the group, but they have previously designed plants that can monitor drought conditions, as well as plants that can detect explosives and communicate with smartphones. They moved on to lighting as the next target due to the fact it accounts for roughly 20 percent of worldwide energy consumption. “Plants can self-repair, they have their own energy, and they are already adapted to the outdoor environment,” Strano says. The group’s goal is to engineer plants to take over many of the functions now performed by electrical devices.
Our work opens up the doorway to streetlamps that are nothing but treated trees, and to indirect lighting around homes.
Michael Strano
The engineers hope to develop a way to spray the nanoparticles onto plant leaves, which would make it possible to transform larger plants and even trees into light sources. The technology could provide low-intensity indoor lighting, or mean that trees could be transformed into self-powered streetlights. The research could eventually enable the creation of plants that can shut off their light emission in response to environmental conditions such as sunlight.
Image Credit: Seon-Yeong Kwak/ MIT
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