‘Fungus ghost’ protects skin, dust against toxins, radiation

The idea of ​​selectively creating porous materials has been attracting the attention of pharmacists for decades. Now, new research from Northwestern University shows that fungi have done exactly that for millions of years.

When Nathan Gianneschi’s laboratory was planning to synthesize melanin that would mimic those formed by certain fungi known to contain unusual, hostile environments, including spaceships, dishwashers, and even Chernobyl, they initially did not expect the materials to be very porous. would not be – a property that allows the material to store and capture molecules.

Melanin is found in living organisms, on our skin and on 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 the turtles’ snakes become darker, for example in the presence of polluted water; moths that live in industrial areas turn black because their cells absorb toxins in soot. The researchers asked them if this type of biomaterial could become spongy to optimize these properties. And in turn whether sponge-like melanins existed in nature.

“The function of Melanin is not fully and in all cases fully known,” said Gianneschi, the corresponding author of the study. “It is definitely a radical scavenger in human skin and protects against UV damage. Now, through synthesis we have encountered this exciting material that can occur very well in nature. Fungi can cause this material to add mechanical strength to their cells, but are porous so that nutrients are left. “

The study will be presented on Friday 5 March 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 in the materials science and biomedical engineering division at McCormick Engineering, Gianneschi is also co-director of the International Institute of Nanotechnology.

The ability to create this material in a laboratory is encouraging for several reasons. In typical non-porous materials, particles adsorb only superficially on the surface. But porous materials like allomelanin absorb and hold in unwanted toxins while allowing good things like air, water and nutrients to pass through. This can enable manufacturers to create breathable, protective covers for uniforms.

“You’re always excited to discover something that might be useful,” Gianneschi said. “But there is also the intriguing idea that, by discovering it, perhaps more such materials already exist in biology. There are not many examples where chemical synthesis leads to a biological discovery. It is mostly the other way around.”

Naneki McCallum, a graduate researcher in the laboratory and first author on paper, noted that melanin looks hollow under the right conditions, or is made visible by electron microscopy. When the team came across the synthetic material, they started experimenting with porosity and selectivity of the materials to adsorb molecules in the voids.

In an important demonstration, the team, who worked with researchers from the Naval Research Laboratory, was able to show that the new porous melanin would serve as a protective layer and prevent simulants from passing through nerve gas. Inspired by this result, they then isolated naturally occurring melanin from fungal cells. This was done by etching away biomaterial from the inside and leaving a shell containing melanin. They call these structures ‘fungus ghosts’ for the elusive, hollow shape’s ‘Casper’ -like quality. The material derived from fungi can also be used as a protective layer in material. Strikingly, the material breathes so that water can pass through while trapping toxins.

Another advantage of this material is its simplicity, as it can be easily manufactured and scaled from simple molecular precursors. In the future, it can be used to make protective masks and face shields and can be used during long-haul flights. With the coating material in space, astronauts can store toxins that they exhale while protecting themselves from harmful radiation, which produces less waste and weight.

It is also a step towards selective membranes, a very complex field of study aimed at taking compounds such as water and permeating healthy minerals while blocking heavy metals such as mercury.

“Fungi can thrive in places where other organisms are struggling, and they have melanin to help them do that,” McCallum said. “So, we ask, what are the properties we can utilize by recreating such materials in the laboratory?”

The article is entitled “Allomelanin: A Biopolymer of Intrinsic Microporosity.”

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