Researchers at Northwestern University have synthesized a new form of melanin enriched in selenium. This new biomaterial, called selenomelanin, demonstrates an extraordinary perspective as a protection of human tissues from harmful radiation. The study publishes The Journal of the American Chemical Society.
Given the increased interest in space travel and the general need for light, multifunctional, and radioprotective biomaterials, scientists are encouraged by the potential of melanin. It occurred to researchers that melanin-containing selenium would provide better protection than other forms of melanin.
Melanin is found in most organisms in the plant and animal world, as well as in bacteria and fungi. Although melanin is known as a high molecular weight pigment, it also provides valuable protection against radiation. In nature, there are five types of melanin, and pheomelanin (a pigment in red hair) absorbs X-rays more efficiently than the more common eumelanin (black and brown pigments in dark hair).
Unwanted exposure occurs during many simple steps, from air travel to x-ray diagnostics and clinical radiation therapy. There are more dangerous cases – a malfunction of a nuclear reactor or a man’s journey into space. A NASA study showed DNA damage to astronaut Scott Kelly in a year spent in orbit. An astronaut flying to Mars can receive 700 times more radiation than on Earth.
Compared to the mass of traditional radioprotective materials such as lead, melanin is easier and more flexible to use. Melanin samples are currently in orbit at the International Space Station and are being studied by another research group to determine how the material reacts to radiation. Recent studies have focused on pheomelanin, which contains sulfur as the best candidate for this purpose.
However, a team of researchers Nathan Dzhanneski from Northwestern University, USA, hypothesized that a new type of melanin – enriched with selenium instead of sulfur – will provide better protection against x-rays. Selenium is a trace element that plays an important role in cancer prevention, and previous studies have reported that selenium compounds can protect animals from radiation. These compounds are found in normal human proteins, but previously they were not associated with melanin.
A team of scientists synthesized a 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 without protective melanin.
After receiving a dose of radiation that would be fatal to humans, only the cells treated with selenomelanin still showed a normal cell cycle.
Our results have shown that selenomelanin provides superior radiation protection. We also found that it was easier to synthesize selenomelanin than pheomelanin, and what we created was closer than synthetic pheomelanin to melanin found in nature.
Nathan Janneski, Team Leader, Northwestern University
Further testing with bacteria showed that selenomelanin can be biosynthesized, which means that living cells that feed on the appropriate nutrients can then produce selenomelanin on their own and maintain its radioprotective properties. In fact, although researchers synthesized selenomelanin in their laboratory, they believe that it can already be present in nature.
Janneski and his team suggest that this new biomaterial can be applied to human skin, like melanin-based sunscreen. It can also be used as a protective film to protect materials from radiation during transportation.