The idea of creating selectively porous materials has captured the attention of chemists for decades. Now, a new study from Northwestern University shows that mushrooms may have been doing just that for millions of years.
When Nathan Janesky̵
Melanin is found in living organisms, on our skin and in the back of our eyes, and as pigments for many animals and plants. It also plays a role in protecting species from environmental stressors. The stripes of sea snakes with a turtle darken, for example, in the presence of polluted water; moths living in industrial areas turn black as their cells absorb toxins in soot. The researchers wondered if this type of biomaterial could be improved on a sponge to optimize these properties. And in turn whether mushroom-like melanins already existed in nature.
“Melanin’s function is not fully known all the time and in all cases,” said Janeski, the study’s author. “It is certainly a radical scavenger in human skin and protects against ultraviolet damage. Now, through synthesis, we have encountered this exciting material that can very well exist in nature. Fungi can make this material to add mechanical strength to cells. its but porous, allowing nutrients everywhere.
The study will be published on Friday, March 5, in Journal of the American Chemical Society.
Janeski is a professor of chemistry at Jacob and Rosalyn Cohn at the Weinberg College of Arts and Sciences. With his appointments in the departments of materials science and biomedical engineering at the McCormick School of Engineering, Janeski is also an associate director of the International Institute of Nanotechnology.
The ability to create this material in a laboratory is encouraging for a number of reasons. In typical non-porous materials, the particles are adsorbed only on the surface. But porous materials such as allomelanin absorb and retain unwanted toxins while leaking good things like air, water and nutrients. This can allow manufacturers to create breathable, protective coatings for uniforms.
“You’re always excited about finding something that is potentially useful,” Janeski said. “But there’s also the intriguing idea that when we find this, there may be more materials like this that already exist in biology. There aren’t many examples where chemical synthesis leads to biological discovery. It’s often the other way around.”
Naneki McCallum, a research student in the lab and the first author of the paper, had noticed that under the right conditions, melanin looked hollow or could be made to contain something like cavities by electron microscopy. When the team came across the synthetic material, they began experimenting with the porosity and selectivity of the materials to adsorb molecules in these cavities.
In a key demonstration, the team working with researchers from the Naval Research Laboratory was able to show that the new porous melanin will act as a protective coating, preventing the penetration of nerve gas simulators. Inspired by this result, they then isolated natural melanin from fungal cells. This was done by etching the biomaterial from the inside, leaving a shell containing melanin. They call these structures “fungal ghosts” for their elusive, hollow, Casper-like quality. The material obtained from the fungus can also in turn be used as a protective layer in the tissues. Remarkably, the material remains breathable, allowing water to pass while trapping toxins.
Another advantage of this material is its simplicity, as it is easily produced and scaled by simple molecular precursors. In the future, it can be used to make protective masks and face shields and has the potential for long-range space applications. Covering materials in space would allow astronauts to store the toxins they exhale, while protecting themselves from harmful radiation by reducing waste and weight.
It is also a step towards selective membranes, an extremely complex area of research that aims to accept compounds such as water and allow healthy minerals to pass while blocking heavy metals such as mercury.
“Mushrooms can thrive in places where other organisms are fighting, and they have melanin to help them do that,” McCallum said. “So we ask, what are the properties we can use by recreating such materials in the lab?”
The paper is entitled “Allomelanin: A Biopolymer with Intrinsic Microporosity”.
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Provided by Northwestern University
Quote: “Fungal ghosts” protect skin, tissues from toxins, radiation (2021, March 5), extracted on March 6, 2021 from https://phys.org/news/2021-03-fungal-ghosts-skin- fabric-toxins.html
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