The “ fungal ghosts ” protect the skin, the tissue from toxins, radiation

The idea of ​​creating selectively porous materials has captured the attention of chemists for decades. Now, new research from Northwestern University shows that mushrooms may have been doing just that for millions of years.

When Nathan Gianneschi’s lab set out to synthesize melanin that would mimic that formed by certain fungi known to inhabit unusual and hostile environments, including spaceships, dishwashers, and even Chernobyl, they didn’t expect initially that the materials turn out to be very porous – a property that allows the material to store and capture molecules.

Melanin has been found in living organisms, on our skin and the backs 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 turtle-headed sea snakes darken, for example, in the presence of polluted water; moths living in industrial areas turn black when their cells absorb toxins from soot. The researchers wondered if this type of biomaterial could be made more like a sponge, to optimize these properties. And, in turn, if the sponge-like melanins already existed in nature.

“The function of melanin is not fully understood all of the time and in all cases,” said Gianneschi, the corresponding author of the study. “It is certainly a radical scavenger in human skin and protects against UV damage. Now, through synthesis, we came across this exciting material that may very well exist in nature. Fungi could make this material for add mechanical strength to their cells, but is porous, allowing nutrients to pass through. “

The study will be published on Friday March 5 in the Journal of the American Chemical Society.

Gianneschi is Jacob and Rosaline Cohn Professor of Chemistry at Weinberg College of Arts and Sciences. With appointments in the Materials Science and Biomedical Engineering Departments of the McCormick School of Engineering, Gianneschi is also Associate Director of the International Institute for Nanotechnology.

The possibility of creating this material in a laboratory is encouraging for a number of reasons. In typical non-porous materials, the particles adsorb only superficially to the surface. But porous materials like allomelanin absorb and hold unwanted toxins while letting good things like air, water, and nutrients pass through. This can allow manufacturers to create breathable protective coverings for uniforms.

“You are always excited to discover something that is potentially useful,” Gianneschi said. “But there’s also the intriguing idea that by finding out about this, maybe more materials like this already exist in biology. There aren’t many instances where chemical synthesis leads to a discovery. biological. It is most often the reverse. “

Naneki McCallum, a graduate student researcher in the lab and first author of the article, had noticed that under the right conditions, melanin appeared to be hollow, or could be made to contain what looked like voids by electron microscopy. When the team discovered the synthetic material, they began to experiment with the porosity and selectivity of materials to adsorb molecules in these voids.

In a key demonstration, the team, working with researchers at the Naval Research Laboratory, were able to show that the new porous melanin would act as a protective coating, preventing nerve gas simulants from passing through. Inspired by this result, they then isolated natural melanin from fungal cells. This was done by stripping the biomaterial from the inside out, leaving a shell containing melanin. They call these structures “fungal ghosts” for the “Casper” quality of the elusive, hollow shape. The material, derived from fungi, could in turn also be used as a protective layer in tissues. Remarkably, the material remains breathable, allowing water to pass through, while trapping toxins.

Another advantage 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 shields and could be used for long-distance spaceflight. Coating materials in space would allow astronauts to store the toxins they exhale while protecting themselves from harmful radiation, which would reduce waste and weight.

It’s also a step towards selective membranes, a very complex area 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 are struggling, and they have melanin to help them do that,” McCallum said. “So, we ask, what are the properties that we can exploit by recreating such materials in the laboratory?”

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

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