MIT turns living plants into desk lamps

CHEMICAL ENGINEERS at MIT have engineered a living plant to emit green light, with the eventual hope of creating living, self-repairing, sustainable lighting solutions, like desk lamps.

The development is from the laboratory, run by chemical engineering professor Michael Strano, that also brought us bionic spinach that can detect explosives and communicate the information to a handheld device, and plants that can monitor drought conditions. Lighting currently accounts for 20% of worldwide energy consumption, and Strano said that as such, lighting was an ideal next target for their research. The plant they experiment with is watercress.

The technology developed by Strano and the team involves embedding nanoparticles into plants. In this case, the team developed nanoparticles containing three different molecules – an enzyme called luciferase, luciferin, and co-enzyme A. Luciferase breaks down luciferin, a reaction which emits light. This is the same reaction that makes fireflies glow. Co-enzyme A removes a byproduct from the reaction which can inhibit the activity of luciferase.

Each of the molecules is encased in a different carrier to ensure it can get to the right part of the plant and prevent toxicity to the plant. Luciferase is carried in silica nanoparticles about 10 nm in diameter. These enter cells in the part of the plant known as the mesophyll, an inner layer of the leaf. The luciferin and co-enzyme A is carried in nanoparticles made of the polymers PLGA and chitosan, which are slightly larger. These nanoparticles move into the extracellular space of the mesophyll.

The nanoparticles are embedded into the plants by suspending them in a solution and then immersing the plants in the solution. Once in the plants, the PLGA particles release the luciferin and co-enzyme A, which infuse into the cells of the mesophyll, where the luciferase acts and light is produced.

At present the plants can glow for around 3.5 hours. While not long, this is a large improvement on the first attempts, which only glowed for 45 minutes. The light is not quite enough to read by yet, with a 10 cm watercress plant emitting only a tenth of the necessary light. However, the researchers say that further optimisation, through optimising the concentration of the components and the release rates, can boost this.

The team has also created glowing kale, rocket and spinach. In future, they hope to be able to simply spray or paint the nanoparticles on to plant leaves.

“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.”

Nano Letters doi.org/chm7