Organic nanowires destroy the competition
Last month, we spoke of our vision of the future of humanity here at the lab. It makes sense that humanity would one-day step away from the static, non-living computer constructs we have designed. Moving us instead towards an organic alternative, one that can be readily repaired, replaced, or changed. While we cannot pretend to know what the future may hold, a new discovery helps bolster the stance we presented.
Researchers have found a microbial protein fiber transports charges at rates high enough to be applied in manmade nanotechnologies. The discovery describes the high-speed protein fiber produced by uranium-reducing Geobacter bacteria. The fibers are hair-like protein filaments called “pili” that have the unique property of transporting charges at speeds of 1 billion electrons per second.
“This microbial nanowire is made of but a single peptide subunit,” said Gemma Reguera, lead author and MSU microbiologist.
“Being made of protein, these organic nanowires are biodegradable and biocompatible. This discovery thus opens many applications in nanoelectronics such as the development of medical sensors and electronic devices that can be interfaced with human tissues.”
Pili are typically used to transfer DNA between bacteria — typically, our creepy little friend the plasmid, which is somehow not considered living. However, they are also used for cellular respiration, attachment, movement, and
possibly probably some form of bacterial communication.
Because they are organic, the cost to grow these organic nanowires is low. Currently existing nanotechnologies incorporate exotic metals into their designs. This means we can readily “grow” nanowire that is not only faster than our best technology, but it will — comparatively — cost next to nothing and is truly a renewable resource.
Geobacter bacteria in particular use their nanowires to bind and “breathe.” The process of breathing involves moving electrons out of an organism, in this case, via metal-containing minerals such as iron oxides and soluble toxic metals such as uranium. The toxins are mineralized on the nanowires’ surface, preventing the metals from permeating the cell.
The protein fibers, which are about 2 nanometers in diameter, were then used to measure the velocities at which they could pass electrons — or in other words, they tested how fast the fibers were at transporting current.
“They are like power lines at the nanoscale,” Reguera said.
“This also is the first study to show the ability of electrons to travel such long distances – more than a 1,000 times what’s been previously proven — along proteins.”
While this may give nanotech and in particular, bio-nanotech a huge head start, the researchers also found another use for the nanowires. They identified metal traps on the surface of the protein nanowires that bind uranium with great affinity and with modification could potentially trap other metals.
This gives a basis for systems that integrate protein nanowires to mine gold and other precious metals, or for scrubbers that can be deployed to immobilize uranium at remediation sites and more. Moreover, the nanowires also can be modified to seek out other materials in which to help them breathe.
“The Geobacter cells are making these protein fibers naturally to breathe certain metals. We can use genetic engineering to tune the electronic and biochemical properties of the nanowires and enable new functionalities.”
“We also can mimic the natural manufacturing process in the lab to mass-produce them in inexpensive and environmentally friendly processes,” Reguera said.
“This contrasts dramatically with the manufacturing of man-made inorganic nanowires, which involve high temperatures, toxic solvents, vacuums, and specialized equipment.
While it may be a while before you can grow your own computer system, the biotech community certainly seems to be on the right path. Besides, why upload your brain a computer when you can have a computer that incorporates your brain?
Lampa-Pastirk, S., Veazey, J., Walsh, K., Feliciano, G., Steidl, R., Tessmer, S., & Reguera, G. (2016). Thermally activated charge transport in microbial protein nanowires Scientific Reports, 6 DOI: 10.1038/srep23517