Developers from Germany have demonstrated a "biohybrid composite" that allows direct collection of electrical charges from bacterial cells.
Marine Shewanella oneidensis is widely known as "bacteria that feed on electricity." Indeed, these microbes are able to obtain and directly use free electrons to reduce metal oxides. It is not surprising that since their unique abilities were discovered, scientists have not abandoned their attempts to turn these bacteria into living sources of "clean" electrical energy.
Unfortunately, in practice it turned out to be quite difficult to learn how to collect charges from individual cells, living and mobile. The first prototype of a device capable of performing such a task appeared only recently. Its developers - the team of Christof Niemeyer from the Karlsruhe Institute of Technology (KIT) - presented the project in an article published in ACS Applied Materials & Interfaces.
To utilize the "superpowers" of S. oneidensis, scientists have assembled a composite base - a liquid-filled hydrogel consisting of carbon nanotubes and chains of spherical silicon nanoparticles intertwined with long DNA strands.
Laboratory experiments have shown that such structures attract S. oneidensis, but not other bacteria. They populated the composite to its entire depth - while, for example, E. coli were only carefully fixed on the surface. According to scientists, the "biohybrid composite" remained stable for at least several days. In doing so, he conducted electricity.
Carbon nanotubes acted as an electrode consisting of a densely intertwined network of thin filaments, and made it possible to collect charged particles from the surface of cells entangled in it. Scientists were able to regulate the work of such a system with the help of enzymes that cut the DNA in the composite, quickly stopping its electrochemical activity.
“Taken together, this shows that potentially similar materials can find application outside the immediate areas, such as the creation of new biosensors, bioreactors and fuel cells,” summarizes Christoph Niemeyer.