Scientists have developed a way to further protect human skin from space radiation

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The Earth is a cocoon of radiation. Inside this cocoon, the atmosphere and the magnetosphere mainly protect us from the sun’s rays. Ultraviolet light passes through and can damage us. But reasonable precautions, such as simply reducing exposure, can keep sunlight away.But space is another matter entirely. Among the many dangers it represents for astronauts, ubiquitous radiation is one that needs a solution.

Today, a team of researchers has developed a new biomaterial to protect astronauts.

This new development is focused on melanins, pigments found in most living things on Earth, including animals like us. Melanins are responsible for red hair, browning of fruits and darkening of the skin after exposure to UV rays from the sun. And it is this last point which is crucial for this work.

The title of the new study is “Selenomelanin: an analog of the abiotic selenium of pheomelanin”. Nathan Gianneschi, professor of chemistry at Northwestern University and associate director of the International Institute for Nanotechnology, led the research. Wei Cao of the Northwestern Department of Chemistry is the first author of the article. The study is published in the Journal of the American Chemical Society.

As ambitious space travel plans keep astronauts away from Earth for longer periods of time, astronauts face increased risks. Leaving aside Hollywood-style disasters, some of the risks are chronic rather than serious. Just like here on Earth, protection from solar radiation over time is important.

“Given the increased interest in space travel and the general need for light, multifunctional and radioprotective biomaterials, we are excited about the potential of melanin.”

Principal investigator Nathan Gianneschi, professor of chemistry, Northwestern University

But the risk in space is much greater. Once outside the cocoon of Earth, astronauts are exposed to much more radiation. Not only from the regular and regular production of the Sun, but also from solar flares and even cosmic rays. The space is flooded with dangerous ionizing radiation.

Ionizing radiation can move in the form of particles or waves. It has enough energy to detach electrons from atoms and molecules, which is bad news for living things. Radiation such as radio waves, microwaves and wifi are not ionizing, while ultraviolet, X-rays and gamma rays are ionizing. Image credit: By Spazturtle – Personal work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=45834629

When astronauts spend time outside low Earth orbit, they face greater risks of exposure to this radiation: cancer and other degenerative diseases, radiation disease, and even central nervous effects, according to NASA . In fact, NASA claims that astronauts can be exposed to radiation doses ranging from 50 to 2,000 milli-Sieverts (mSv). But even 1mSv is equivalent to about three chest x-rays, so it’s like astronauts are exposed to between 150 and 6000 chest x-rays. (Would you like to sign up for this?)

We could put astronauts in lead – or put them behind lead screens like radiology technicians in hospitals – and they would be protected. The problem is, how can astronauts accomplish all of their tasks, while being protected from all harmful radiation?

Lead is also extremely heavy and it is not practical to throw lead into space for radiation shielding. “We are unlikely to be able to fly on a mass dedicated to radiation protection,” for missions like Artemis, said Kerry Lee of NASA’s Johnson’s Space Radiation Analysis Group in a press release.

Lead is commonly used to protect people and things from strong radiation. The reason it is so effective is its high density and weight. It also makes its use problematic. Image credit: by Changlc – Personal work, public domain, https://commons.wikimedia.org/w/index.php?curid=599629

This is what sparked interest in melanin.

“Given the increased interest in space travel and the general need for light, multifunctional and radioprotective biomaterials, we are excited about the potential of melanin,” said lead researcher Nathan Gianneschi said in a statement. hurry. “It came to our mind of our postdoctoral fellow Wei Cao that melanin containing selenium would offer better protection than other forms of melanin. This raised the intriguing possibility that this undiscovered melanin could very well exist in nature, used in this way. So we ignored the discovery part and decided to do it ourselves. ”

On Earth, when our skin is exposed to UV rays, we produce more melanin. This darkens the skin and the pigmentation of melanin is effective in absorbing light. In fact, it can absorb up to 99.9% of UV rays.

Researchers already know that melanin has the potential to protect astronauts from radiation. A separate research team is experimenting with samples of it on the International Space Station, to see how it reacts to radiation there, which is not only UV radiation, but more energetic radiation like X-rays.

Illustration of the Artemis astronauts on the Moon. The Moon has neither a magnetosphere nor a protective atmosphere, so Artemis astronauts, and all astronauts working on a future lunar base, will need protection against ionizing radiation. Credits: NASA

But there are different types of melanins. The one tested on the ISS is in fact a composite of fungal melanin and polymers. The main researcher on this work is Radamés JB Cordero de Johns Hopkins. “The goal will be to take melanin and create nature-inspired biomaterials,” said Cordero. “We are seeing if we can imitate biology and learn from biology to our advantage. ”

But this new research is going in a slightly different direction, looking at melanin enriched in selenium. Selenium has an interesting relationship with light and is used as a pigment, in the manufacture of glass, in X-ray detectors and in solar cells. Obviously, something is going on with selenium when it comes to radiation.

Previous research has shown that selenium compounds can protect animals from X-rays. The team behind the new work therefore wondered whether combining melanin and selenium would offer a new way to protect astronauts.

Rather than spending who knows how long trying to find the compound somewhere in the wild, they decided to make their own compounds in a laboratory. They have synthesized a new biomaterial which they call “selenomelanin”. They treated cells with the new material, alongside cells treated with synthetic pheomelanin and eumelanin. They also used cells without protective melanin as a control group.

Then came the radiation. They exposed all cells to a dose of radiation that would be fatal to a human. The result? Only the cell treated with their synthesized selenomelanin showed normal cell cycles.

Human cells treated with selenomelanin nanoparticles.  Image credit: Northwestern University
Human cells treated with selenomelanin nanoparticles. Image credit:
Northwestern University

“Our results have shown that selenomelanin provides superior radiation protection,” said Gianneschi. “We also found that it was easier to synthesize selenomelanine than pheomelanin, and what we created was closer than the synthetic pheomelanin to melanin found in nature. ”

It gets better.

The team also discovered that unlike samples sent to the ISS by a separate research team, which is expensive to produce, the team’s selenomelanin can be bio-synthesized. This means that living cells can produce it when they are fed the right nutrients. And the biosynthesized selenomelanin retains its protective properties.

“With an abundant source of selenium in the environment, some organisms have been able to adapt to extreme circumstances such as radiation by the beneficial effects of selenomelanin, “said Gianneschi.

“Our work indicates the possibility that melanin may act as a reservoir of selenium, thereby contributing to the benefit of organisms,” said Cao. “Selenomelanin can play an important role in how selenium is metabolized and distributed biologically. This is an area to deepen. ”

This discovery could lead to better protection for astronauts – and radiation-sensitive materials – in space. The research team is considering a topical material such as sunscreen, which can be applied to the skin or protective materials.

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