The idea of creating selectively porous materials has captured the attention of chemists for decades. Now, new research from Northwestern University shows that fungi may have been doing exactly this for millions of years.
When Nathan Gianneschi’s lab set out to synthesize melanin that mimicked that formed by certain fungi known to inhabit harsh and unusual environments, such as spacecraft, dishwashers, and even Chernobyl, they initially did not expect the materials to be highly porous, a property that allows the material to store and capture molecules.
Melanin has been found in living organisms, on our skin and the back of our eyes, and as pigments for many animals and plants. It also plays a role in protecting the species from environmental stressors. The stripes of turtle-headed sea snakes darken, for example, in the presence of polluted water; moths that live in industrial areas turn black when their cells absorb toxins in the soot. The researchers wondered if this type of biomaterial could be made more sponge-like to optimize these properties. And, in turn, if fluffy melanins already existed in nature.
“The function of melanin is not fully understood all the time and in all cases,” said Gianneschi, the corresponding author of the study. “It is certainly a radical scavenger on human skin and protects against UV damage. Now through synthesis we have found this exciting material that may very well exist in nature. Fungi can produce this material. to add mechanical resistance to its cells, but porous, allowing the passage of nutrients “.
The study will be published on Friday, March 5 in the Journal of the American Chemical Society.
Gianneschi is the Jacob and Rosaline Cohn Professor of Chemistry at the Weinberg College of Arts and Sciences. With appointments to the departments of materials science and biomedical engineering at the McCormick School of Engineering, Gianneschi is also associate director of the International Institute of Nanotechnology.
The ability to create this material in a laboratory is promising for several reasons. In typical non-porous materials, the particles are only superficially adsorbed on the surface. But porous materials like allomelanin absorb and retain unwanted toxins while letting good things like air, water, and nutrients pass through. This can allow manufacturers to create breathable protective coatings for uniforms.
“You are always excited to discover something that is potentially useful,” Gianneschi said. “But there is also the intriguing idea that by discovering this, perhaps more materials like this already exist in biology. There are not many examples where chemical synthesis leads to a biological discovery. Most of the time it is the other way around.” .
Naneki McCallum, a research graduate student in the lab and first author on the paper, had noted that under the right conditions, melanin appeared to be hollow, or could be made to contain what appeared to be voids by electron microscopy. When the team found the synthetic material, they began to experiment with the porosity and selectivity of the materials to adsorb molecules in those voids.
In a key demonstration, the team, in collaboration with researchers from the Naval Research Laboratory, were able to demonstrate that the new porous melanin would act as a protective layer, preventing nerve gas simulators from passing through. Inspired by this result, they isolated the natural melanin from fungal cells. This was done by etching the biomaterial from within, leaving a shell containing melanin. They call these structures “mushroom ghosts” because of the “Casper” quality of the hollow and elusive shape. The material, derived from fungi, could also, in turn, be used as a protective layer on fabrics. Surprisingly, the material remains breathable, allowing water to pass through, while trapping toxins.
Another benefit of this material is its simplicity, as it is easily produced and scaled from simple molecular precursors. In the future, it could be used to make protective masks and face masks and has potential for long-distance spaceflight applications. Cladding materials in space would allow astronauts to store the toxins they exhale while shielding themselves from harmful radiation, resulting in less waste and weight.
It is also a step towards selective membranes, a very complex field of study that aims to take compounds like water and allow healthy minerals to pass through while blocking heavy metals like mercury.
“Fungi can thrive in places where other organisms fight, and they have melanin to help them do so,” McCallum said. “So we asked, what are the properties that we can take advantage of by recreating these materials in the laboratory?”
The article is titled “Allomelanin: an intrinsic microporosity biopolymer.”
A new biomaterial could protect against harmful radiation
Provided by Northwestern University
Citation: ‘Fungal ghosts’ protect skin, fabric from toxins, radiation (March 5, 2021) Retrieved March 6, 2021 from https://phys.org/news/2021-03-fungal-ghosts- skin-fabric-toxins.html
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