Selenomelanin

[rakaydos]

Gianneschi’s team synthesized the new biomaterial, which they called “selenomelanin,” and used it to treat living cells. For comparison, they also prepared cells treated with synthetic pheomelanin and eumelanin, as well as cells with no protective melanin.

After receiving a dose of radiation that would be lethal to a human being, only the cells treated with selenomelanin still exhibited a normal cell cycle.

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

https://news.northwestern.edu/stories/2020/07/new-biomaterial-could-shield-against-harmful-radiation-selenomelanin/

Northwestern‘s Nathan Gianneschi, who led the research, said, “Our results demonstrated that selenomelanin offers superior protection from radiation. We also found that it was easier to synthesize selenomelanin than pheomelanin, and what we created was closer than synthetic pheomelanin to the melanin found in nature.”

In experiments with bacteria, scientists found that the selenomelanin can be biosynthesized. It means live cells fed with appropriate nutrients can then produce selenomelanin on their own — and retain its radioprotective properties.

Although scientists synthesized selenomelanin in their lab, they believe that it may be already present in nature.

https://www.techexplorist.com/biomaterial-shield-harmful-radiation/33617/

https://www.materialstoday.com/biomaterials/news/new-melanin-offers-protection-against-radiation/

New radiation shielding materials are always of interest to spaceflight, of course. The sources keep talking about it  as a "sunscreen", applied externally, or as a genetic manipulation to make rad-hardened life. But if organic films are sufficent to prevent lethal doses (of Xrays), including at least a layer of it in space radiation shields may save significant weight.

[Twark_Main]

It could be a good supplement therapy for use in-transit, but as a "sunscreen" it's hard to imagine it having higher mass efficiency than a polyethylene suit (possibly with some B¹⁰ sprinkled in).

https://www.nasa.gov/sites/default/files/atoms/files/niac_2011_phasei_thibeault_radiationshieldingmaterials_tagged.pdf

[Welsh Dragon]

Interesting work. The biology in this is way better than in most chemistry heavy papers. They actually used primary cells rather than cell lines for once, which means it's not automatically pointless. Next step would obviously be in vivo. But I agree, it's probably going to be more efficient and safer to use external shielding.

[rakaydos]

What really interests me, is if this compound can handle the backscatter radiation from a stainless steel structure, more easilly than a bulk radiation absorber. They tested vs Xrays, and high energy neutrons produce gamma ray backscatter, which is quite a bit more powerful.

[sanman]

What really interests me, is if this compound can handle the backscatter radiation from a stainless steel structure, more easilly than a bulk radiation absorber. They tested vs Xrays, and high energy neutrons produce gamma ray backscatter, which is quite a bit more powerful.

Is there any danger of some kind of weird resonance effect happening when your space vessel is a metal chamber?

[Vahe231991]

What really interests me, is if this compound can handle the backscatter radiation from a stainless steel structure, more easilly than a bulk radiation absorber. They tested vs Xrays, and high energy neutrons produce gamma ray backscatter, which is quite a bit more powerful.

Given that the Starship is not just made from stainless steel but is also intended for manned flights to the Moon and Mars, it'd be interesting to see if human passengers shielded with selenomelanin will be protected from harmful radiation if they travel to Mars aboard Starship.

[Genial Precis]

I think the lede may have been deeply buried here. The supporting info isn't behind a paywall, see here: https://pubs.acs.org/doi/10.1021/jacs.0c05573?goto=supporting-info
If you look at tables S1-S3 on pp. 39-41, selenomelanin appears to be a powerful protective agent for these cells against x-rays. Unlike conventional melanin, when the selenomelanin-loaded cells were exposed to 6 Gray of x-rays in a short period (near the LD50 for human exposure over the whole body), they didn't become nonviable or enter this G2/M state.

You can make radiation shielding out of many things, but maybe there are prospects of making people and/or other relevant organisms a lot more tolerant of ionizing radiation with this or other biochemicals. Even then it might not be worth doing, but that's a very different prospect to mere shielding.

The cells in question were only loaded with 0.004 mg/mL of selenomelanin nanoparticles. That would be less than a gram to load a whole human at that concentration. Even a kilogram of selenomelanin might not be out of the question if it really worked like that, but such a small amount is so astonishing I wonder if there's an error somewhere in this.

I'm glad I bothered to read the original research behind this post.

[Robotbeat]

I believe this is a biological effects not a blocking Effect.

Very radiation-tolerant microbes exist on Earth. Because there are biological mechanisms for repairing damage from radiation.

In principle, it’s not obvious that humans would necessarily even require radiation shielding if these mechanisms are well understood and engineered.

Now, a word of caution: the primary fear of space radiation is not cell death but long term carcinogenicity, ie cancer. It’s possible that you could INCREASE carcinogenicity by preventing cells from dying which have been exposed to a lot of harmful radiation.