Bionic plants could light the future
Researchers harness the energy and potential of plants
Instead of mobile phone towers and street lights, imagine a world where trees light our way at night and branches are antennae.
This vision to harness plants as a source of energy has its roots in a groundbreaking paper published today by Professor Michael Strano and his team at the Massachusetts Institute of Technology.
Their research into "bionic plants", reported in Nature Materials, shows how they inserted nanoparticles into plants to enhance or deliver non-native properties.
In experiments on chloroplasts extracted from baby spinach leaves and thale cress, the researchers demonstrate they can make plants sensitive to certain substances, opening the path to their use as sensors; boost the plants' photosynthesis activity so they are at least three times more effective than control plants; and enhance plant repair, allowing for the possible harnessing of plant energy as a fuel.
Strano says these advances rely on their development of two innovative techniques through which to deliver the nanoparticles to the plant.
The first technique is known as "vascular infusion" and involves forcing under pressure a nanoparticle solution through the pores in the leaf from which water normally evaporates, he says.
In the second method, known as lipid exchange envelope penetration or LEEP, nanoparticles are coated with a highly negative or highly positive polymer coating that promotes absorption of the nanoparticle through the chloroplast membrane.
Strano says as the membrane "re-heals" after absorption the nanoparticle is trapped within the chloroplast, which he calls the "engine of the plant".
Plants as technology
The work is the first step, he says, in harnessing the energy and potential of plants.
"It is important we start to see plants as the starting point of technology. They have these advantages of self-repair and are made of materials that survive harsh environments and have their own water source," he says.
Strano says one of the main uses they are currently investigating is turning a living plant into a chemical sensor.
It is important we start to see plants as the starting point of technology. They have these advantages of self-repair and are made of materials that survive harsh environments and have their own water source,- Researcher Michael Strano
"Plants have the ability to sample through gas exchange a large portion of their environment and water ... so are a great place to put a sensor," he says.
Using the new nanobionic techniques the team can inject particles into the plant that are sensitive to pollutants such as nitrous oxide.
If the pollutant is detected the nanobionically altered plant emits light in the near infrared which is then detected by imaging cameras.
Strano says his team has been successful in increasing photosynthetic activity in the plants by a factor of three. The enhancement occurs because the nanoparticles broaden the spectrum of captured light.
However, he says they are still trying to evaluate whether this increase will lead to an enhanced plant growth rates, which would be a valuable tool in agriculture.
But Strano sees other potential for the technique.
If you "supercharge the growth of plants you could generate excess power that you could use for other functions in the plant", he says.
Similarly enhancing plant repair could lead to "bags of chlorophyll" being used as a fuel source.
"Chlorophyll is essentially a bag of proteins that converts carbon dioxide into fuel using sunlight," says Strano.
"Given our situation today that is probably one of the most important chemistries to be able to do."
However, while the extraction of chlorophyll is simple, after about an hour outside the plant it will stop functioning and no longer produce sugars [fuel].
"We are trying to re-engineer them because what I would really like is to develop a chlorophyll that can sit on the shelf and be active," he adds.
Strano says his team is working on a range of ideas and should be ready to publish work on the sensor concept in the next year.
However, he sees unlimited potential in the new field.
"In the US when we put a cell phone tower near a forest area we try to disguise it with fake branches," he says.
"Why can't a real tree be the cell-phone tower ... we can give it the ability to absorb and emit gigahertz radiation."
Similarly he sees avenues of trees replacing unsightly street lights.
"Suppose we could put nanoparticles [in trees] that catalyzed chemiluminescence - you could make trees that essentially glow in the dark and are powered by the plant."