“We insert nanotubes into bacteria,” explains Professor Ardemis Boghossian from the School of Basic Sciences of EPFL. “It doesn’t seem exciting at first glance, but it’s a big deal. The researchers put the nanotubes into the mammalian cells (Nanotubes light up the photovoltaics way of life) using a process like endocytosis, which is specific for those types of cells. Bacteria, on the other hand, lack these mechanisms and face additional challenges in transporting molecules through their hard surfaces. Despite these obstacles, we have succeeded in doing this, and it has a very interesting effect in terms of applications.
Boghossian’s research focuses on integrating engineered (Nanotubes light up the photovoltaics way of life) nanomaterials, including biological cells. The resulting “nanobionic” technologies combine the benefits of the living and non-living worlds. For many years, his team has been working on nanomaterial applications of single-walled carbon nanotubes (SWCNTs), tubes of carbon atoms with interesting mechanical and optical properties.
These properties make SWCNTs suitable for many new applications in the field of nanobiotechnology. For example, SWCNTs have been implanted into mammalian cells to monitor their metabolism using near-infrared imaging. The incorporation of SWCNTs into tissue cells has also enabled new technologies to deliver therapeutic drugs to their intracellular targets, while in plant cells they have been used for genome editing. SWCNTs have also been implanted into living mice to demonstrate their ability to see living tissue inside the body.
Fluorescent nanotubes in bacteria: a first
In a paper published in Nature Nanotechnology, the Boghossian team and their colleagues succeeded in “convincing” bacteria to simultaneously lift SWCNTs by “decorating” them with proteins. those with positive (Nanotubes light up the photovoltaics way of life) charges that are attracted to the negative charges of the skin. The two types of bacteria examined in the study, Synechocystis and Nostoc, belong to the phylum Cyanobacteria, a large group of bacteria that derive their energy from photosynthesis – just like plants. They are also “gram-negative” meaning that their cell walls are thin and have an outer membrane that “gram-positive” bacteria do not have.
The researchers found that cyanobacteria penetrate SWCNTs through a passive, length-dependent process. This method allowed SWCNTs to penetrate the cell walls of unicellular Synechocystis and long, multicellular snakes such as Nostoc.
After this success, the team wanted to see if nanotubes could be used to image cyanobacteria – just like in human cells. “We built a custom setup that allows us to photograph the unique near-infrared fluorescence we get from the nanotubes inside the bacteria,” says Boghossian. Alessandra Antonucci, a former PhD student in Boghossian’s lab, adds: “When the nanotubes are inside the bacteria, you can see them clearly, even though the bacteria emit their own light. In fact, the wavelength of nanotubes is far in the red, near infrared.
You will get a clear and stable signal from nanotubes that you cannot get from any other nanoparticle sensor. We are excited because we can now use nanotubes to see what is happening inside cells that is difficult to see using particles or proteins. Nanotubes emit light that no natural living thing emits, not at these wavelengths, and that makes the nanotubes actually appear in these cells.
“inherited nanobionics”
Scientists can monitor cell growth and division by directly examining bacteria. Their findings show that SWCNTs are shared by the daughter cells of the dividing microbe. “When bacteria divide, the daughter cells inherit the nanotubes and the characteristics of the nanotubes,” says Boghossian. “We call it ‘hereditary nanobionics.’ It’s like having an artificial limb that gives you abilities beyond what you can achieve naturally. And now, imagine that your children will inherit his property when they are born. Not only did we pass this behavior on to bacteria, but this behavior was also inherited by their offspring. This is our first demonstration of legacy nanobionics.
photovoltaic living
“Another interesting thing is that when we put the nanotubes inside the bacteria, the bacteria show a great improvement in the electricity it produces when the light shines,” said Melania Reggente, student post -doctoral from Boghossian explains. “But our lab is currently working on the idea of using these nanobionic bacteria to make living photovoltaics.”
“Living” photovoltaics are living energy production devices that use photosynthetic micro-organisms. Although it is still in the early stages of development, these devices represent a good solution to our current energy problems and our efforts against climate change.
“There is a dirty secret in the photovoltaic community,” says Boghossian. “It’s green energy, but the carbon footprint is really high; A lot of CO2 is released just to power most standard photovoltaics. But the great thing about photosynthesis is not only that it uses solar energy, but that it also has a negative carbon footprint. Instead of releasing CO2, it absorbs it. So it solves two problems at the same time: the conversion of solar energy and the processing of CO2. And these solar cells are alive. You don’t need a factory to build any bacterial cell; These bacteria produce themselves. They automatically absorb CO2 to produce more of themselves. It’s a material scientist’s dream.
Boghossian is responsible for a living photovoltaic device based on cyanobacteria that has automatic electrical control that does not depend on the addition of foreign materials. “In terms of implementation, the current obstacles are the cost and environmental impact of introducing nanotubes into cyanobacteria on a large scale.”
Considering the large-scale implementation, Boghossian and his team are turning to synthetic molecular methods for answers: “Our lab is currently working on the bioengineering of cyanobacteria that can produce electricity without the need for nanoparticle additions.Advances in synthetic biology allow us to reprogram these cells to behave in a more precise way. We can think of them as the power that is actually in their DNA.
