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If Michael Strano has his way, homes and streets of the future will be lit up with “green” energy — literally — from glowing plants and trees. While that may sound like a lofty goal, the Massachusetts Institute of Technology (MIT) professor of chemical engineering and his team are well on their way to realizing the dream with a luminescent plant, which they hope will someday replace your bedside or table lamp!
To create the glowing plants, the scientists turned to fireflies for assistance. In the bioluminescent insects, an enzyme called luciferase reacts with a molecule called luciferin, causing it to release light. Another molecule, dubbed coenzyme A, helps the process along by getting rid of a byproduct of the reaction that inhibits luciferase activity.
The researchers began by extracting all three chemicals and packaging them in separate nanoparticle carriers. This would ensure that they would reach the appropriate areas of the leaves in the required quantities without harming the plant. The particles containing the luciferin and coenzyme A were targeted to reach the extracellular space of the mesophyll, an inner layer of the leaf, while the carrier with the luciferase, went directly into the mesophyll cells.
The final step entailed infusing the components into the plants. To achieve this, the three particle carriers were placed in a solution. The researchers then submerged some plants into the solution and applied high pressure, enabling the nanoparticles to enter through the stomata, the tiny pores found on the undersurface of the leaves. As the luciferin gradually entered the plant cells, it reacted with the already-present luciferase emitting a glow bright enough to be observed through the leaves.
While the initial luminescence lasted just 45 minutes, the researchers have since been able to increase the time to a respectable 3.5 hours. Though the light emitted by a 10-centimeter watercress seedling is too dim for reading, the team is confident that with further optimization of the chemicals, they can increase both the intensity and duration of the glow. They have even devised a way to “turn off” the glowing plant by using a luciferase inhibitor.
This is not the first time scientists have developed glowing plants. However, previous attempts have involved genetically engineering the plants, a slow, laborious process. It also worked on a limited variety of plants and resulted in very faint light. The MIT innovation, which has been successfully tested on watercress, arugula, kale, and spinach, is not only easier to implement, but also appears to be working universally.
Once the technique has been perfected, the researchers, who published the study in the ACS journal Nano Letters in November 2017, envision developing a way to paint or spray plant leaves with the nanoparticles, so that even large trees can become light sources. “Our target is to perform one treatment when the plant is a seedling or a mature plant, and have it last for the lifetime of the plant,” Strano says. “Our work very seriously opens up the doorway to streetlamps that are nothing but treated trees, and to indirect lighting around homes.”
This is not the first time the MIT Lab, a pioneer in Plant nanobionics, has transformed ordinary shrubs. Their previous inventions include explosive-detecting plants that relay the information to smartphones and ones that send out distress signals when in need of water!