Nanotubes light the way to living photovoltaics

Light-harvesting bacteria saturated with nanoparticles can produce electricity in “living photovoltaic cells”. Credit: Giulia Vattorini

“We put the nanotubes inside the bacteria,” says Professor Ardemis Boghossian of the EPFL School of Basic Sciences. “This doesn’t look very exciting on the surface, but it is actually important. Researchers have put nanotubes into mammalian cells that use mechanisms such as endocytosis, specific to those types of cells. On the other hand, our bacteria don’t do these mechanisms and we face additional challenges. “In getting the particles through their tough outer form. Despite these barriers, we’ve been able to do that, and that has very exciting implications in terms of applications.”

Boghossian’s research focuses on linking synthetic nanomaterials to biological structures, including living cells. The resulting “nano” technologies combine the advantages of the living and non-living worlds. For years, her group has worked on applications of single-walled carbon nanomaterials Nanotubes (SWCNTs), tubes of carbon atoms with remarkable mechanical and optical properties.

These properties make SWCNTs ideal for many new applications in nanobiotechnology. For example, SWCNTs were placed inside mammalian cells To monitor their metabolic processes using near-infrared imaging. The introduction of SWCNTs into mammalian cells has also led to new technologies for delivering therapeutic drugs to their intracellular targets, while they have been used in plant cells for genome editing. SWCNTs have also been implanted in live mice to demonstrate their ability to image biological tissues deep within the body.

Fluorescent nanotubes in bacteria: first

In an article published in Nature’s nanotechnologyIn this study, Boghossian’s group and their international colleagues were able to “convince” bacteria to spontaneously take up SWCNT molecules by “decorating” them with positively charged proteins that are attracted by the negative charge of the bacteria’s outer membrane. Two of the bacteria explored in the study, Synechocystis and Nostoc, belong to the phylum Cyanobacteria, an enormous group of bacteria that get their energy through photosynthesis — like plants. They are also “gram negative”, which means that cell wall It is thin and has an extra outer membrane that Gram-positive bacteria lack.

The researchers observed that cyanobacteria internalized SWCNTs through a selective, passive, length-dependent process. This process allowed SWCNTs to spontaneously penetrate the cell walls of both the unicellular Synechocystis and the long, multicellular snake-like Nostoc.

Following this success, the team wanted to see if the nanotubes could be used to image cyanobacteria – as is the case with mammalian cells. “We created the first custom setup of its kind that allowed us to image the special near-infrared fluorescence that we get from nanotubes inside bacteria,” Boghossian says.

Alessandra Antonucci, former Ph.D. A student in Boghossian lab adds, “When the nanotubes are inside the bacteria, you can see them very clearly, even though the bacteria emit their own light. This is because the wavelengths of nanotubes are far in red, and near infrared. You get a very clear and stable signal. of nanotubes you can’t get from any other nanoparticle sensor.We’re excited that we can now use nanotubes to see what’s going on inside cells that are difficult to image with more conventional particles or proteins.Nanotubes give off light that no living natural substance emits, not at these wavelengths, which makes the nanotubes really stand out in these cells.”

Inherited nanoscience

Scientists were able to track cell growth and division by monitoring bacteria in real time. Their findings revealed that SWCNTs were common to the daughter cells of the dividing microbe. “When the bacteria divide, the daughter cells acquire the nanotubes along with the properties of the nanotubes,” Boghossian says.

“We call this ‘inherited nanoscience.’ It’s like having a prosthetic that gives you capabilities beyond what you can naturally achieve. Now imagine that your children can inherit its characteristics from you when they are born. Not only did we transmit bacteria with this prosthetic behavior, but this behavior is It’s also inherited by their descendants. It’s our first demonstration of inherited nanoparticles.”

live photovoltaic cells

“Another interesting aspect is when we put the nanotubes inside the bacteria, the bacteria show a significant improvement in the electricity they produce when illuminated with light,” says Melania Regent, a postdoctoral researcher with Boghossian’s group. “And our lab is now working on the idea of ​​using these nano-bacteria in live photovoltaics.”

“Live” photovoltaic cells are biological energy production devices that use photosynthetic microorganisms. Although these devices are still in the early stages of development, they represent a real solution to the ongoing energy crisis and efforts to combat climate change.

“There is a dirty secret in the PV community,” Boghossian says. “It’s green energy, but carbon traces Really high a lot of carbon dioxide2 It was only released to make most standard photovoltaic cells. But what’s nice about photosynthesis isn’t just about harnessing it Solar energy, but also has a negative carbon footprint. Instead of releasing carbon dioxide2suck it up. So it solves two problems simultaneously: converting solar energy and carbon dioxide2 confiscation. These solar cells are alive. You don’t need a plant to build each bacteria cell individually; these bacteria It is self-replicating. They automatically take in carbon dioxide2 To produce more themselves. This is the dream of a materialist.”

Boghossian envisions a living photovoltaic device based on cyanobacteria that has automated control over the production of electricity that does not depend on the addition of foreign particles. “In terms of implementation, the obstacle now is cost and environmental effects Placing nanotubes inside cyanobacteria is widespread.”

With a focus on large-scale implementation, Boghossian and her team are looking forward to it Synthetic Biology For answers: “Our lab is now working on bioengineering cyanobacteria that can produce electricity without the need for nanoparticle additives. Advances in synthetic biology allow us to reprogram these cells to behave in completely artificial ways. We can engineer them so that electricity is literally produced in their DNA” .

Directed evolution builds nanoparticles

more information:
Ardemis Boghossian et al, Carbon nanotube adsorption in cyanobacteria for near-infrared imaging and bioelectricity generation in live photovoltaics, Nature’s nanotechnology (2022). DOI: 10.1038 / s41565-022-01198-x

the quote: Nanotubes Light the Way to Living Photovoltaics (2022, September 12), Retrieved September 12, 2022 from

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