Researchers from the Lawrence Berkeley National Laboratory have created a self-assembling “molecular paper” that may be used for various biological applications in the future.
In an April 11 study published in the journal Nature Materials, researchers described the “nanosheet” they created as the first two-dimensional synthetic membrane that might be engineered in the future to sequester carbon dioxide, detect pathogens in the air and allow for the more efficient construction of electronics. The material used to develop the membrane would give scientists unprecedented control over the membrane’s shape and purpose.
“Membranes themselves are very useful,” said Ronald Zuckermann, lab researcher and co-author of the study. “(The nanosheet) could be used to collectively pass carbon dioxide through the membrane but not water or other gases, and that would be useful in carbon sequestration to remove carbon dioxide from the atmosphere. You need precise control over a material to be able to do something like that.”
The nanosheets are composed of billions of aligned peptoid chains, which are building blocks of artificial proteins, Zuckermann said. Each peptoid chain is a special sequence of artificial amino acids, which allows the nanosheet to be programmed for different applications.
Zuckermann said once the peptoid chains form and are placed in water, they self-assemble into a sheet form.
“What’s new is that we’ve been able to make sequence-specific polymers, and when you form a polymer with a new level of information content, it controls the shape of the molecules and it controls the type of material you can make; so, we’re giving the polymer a little instruction,” he explained.
The ability to hold information-similar to the capabilities of an actual cell membrane-is what differentiates the nanosheet from other material built from similar synthetics, Zuckermann said.
“A normal polymer-a plastic bag or something-has zero information content because they have the same monomer over and over,” Zuckermann said. “We’ve introduced this idea of information content into non-natural polymers.”
The membrane still has to be engineered for a specific function, said Ki Tae Nam, a graduate student in Zuckermann’s lab and co-author of the study.
According to Zuckermann, the study was funded by the U.S. Department of Energy and the Defense Threat Reduction Agency, which was interested in how the membrane could be engineered as a sensor to detect pathogens or toxins in biological warfare.
“Peptoids are very similar to … proteins, but have some amazing potential advantages for nanoscience: their structures are typically resistant to organic solvents, high temperatures, and salt conditions that would unfold almost any protein structure,” said Modi Wetzler, a bioengineering graduate student at Stanford University, in an e-mail. “Thus, if peptoid nanomaterials could be made in that size range, they could be much stabler and more broadly applicable than protein nanomaterials.”
Zuckermann said the researchers would like to increase the size of the membrane in the future and develop coding that would allow the membrane to be used in its intended environmental and biological applications.
“This research is a good combination of human technology and biology systems to make a better system and not just mimic nature,” Nam said.