Preventing radiation damage with melanin-based material

Radiotherapy for abdominal and pelvic cancers almost always leads to small-intestine injuries that are difficult to heal, eroding the quality of life of patients. To counteract this, researchers have developed an orally consumable material made from melanin—the pigment in our skin that protects us from ultraviolet rays—that can shield the intestines from ionizing radiation (Cell Biomater. 2025, DOI: 10.1016/j.celbio.2025.100214).

“Some microorganisms in high-dose radiation environments are rich in melanin, which sparked our interest in melanin’s role in radiation protection,” says Wei Cao, a professor of chemistry at Beijing Normal University. Cao and his team synthesized selenium-modified melanin nanoparticles (SeMNPs) through the oxidative polymerization of two naturally occurring amino acids: selenocysteine and L-dopa. Selenium is an essential trace element that plays a critical role in the intracellular antioxidant system. Back in 2020, an unrelated group found that selenomelanin-treated cells withstood radiation exposure better than untreated cells.

Cao’s group found that SeMNPs adequately tolerate gastric juices and intestinal enzymes for up to 6 h. When the researchers incubated human cells with SeMNPs and irradiated them, the nanoparticles protected the cells, suppressed the generation of superoxide free radicals, scavenged reactive oxygen species that cause cell damage, and relieved cell-cycle arrest due to radiation-induced DNA damage.

To gauge the radioprotective strength of the SeMNPs, the researchers injected them intraperitoneally into mice and then subjected the animals to whole-body radiation. All the mice who received injection survived for 30 days, while 80% of those who weren’t injected died within 6 days.

The researchers also fed mice some SeMNPs before irradiating their whole body. Examination of their intestines after 7 days showed relatively healthy tissues with reduced DNA damage. Analysis of intestinal proteins showed that SeMNPs had suppressed inflammatory pathways, and the gene expression profile was almost similar to that of nonirradiated intestines.

Current radioprotection drugs like amifostine and palifermin are not suited for protecting the gut because they must be injected, have short half-lives, and have poor stability. That’s why an orally administered molecule that can withstand the harsh environments of the stomach and intestines could be so valuable.

“This is a nice preclinical study addressing clinically relevant radiation-induced intestinal injury,” James Byrne, a radiation oncologist at the University of Iowa who wasn’t involved in the study, says in an email to C&EN. “I appreciate the antioxidant activity of the SeMNPs and believe this drove a large portion of the effect.” Byrne cautions that “radiation doses and exposure patterns in mouse models often don’t translate to fractionated radiotherapy regimens used in humans,” but the study is promising for human application, he says.