K‐Edge‐Inspired Selenomelanin Hydrogel: An X‐Ray Filtering Biomaterial for Skin Protection in Radiotherapy

Abstract

Abstract Radiotherapy is widely employed in cancer treatment, yet its inevitable side effects, particularly radiation dermatitis (RD), remain a significant concern. Numerous studies focus on alleviating RD symptoms, but approaches to minimize the radiation dose to the skin are underexplored. Shielding skin‐damaging photons (10–20 keV) holds promise for skin dose reduction; however, this strategy is hindered by inadequate shielding efficiency of current RD biomaterials and overshielding by conventional high‐ Z materials which attenuate therapeutic high‐energy photons. Here, inspired by the strong absorption of near‐threshold‐energy photons at the K‐edge, an energy‐selective shielding strategy by integrating selenium‐containing melanin nanoparticles with a carbomer hydrogel is proposed, developing an X‐ray filtering skin dressing (SeMNPs@Car). It exhibits up to 96% shielding for low‐energy X‐ray (10–20 keV) while maintaining over 98% transmission for high‐energy photons. In RD animal models, the SeMNPs@Car achieves 100% prevention of ulceration and the longest delay in the onset of RD (≈20 days), outperforming clinical RD treatments. Furthermore, Monte‐Carlo‐based reconstruction of radiotherapy scenarios demonstrates its clinical applicability. This work incorporates photoelectric absorption properties into hydrogel design, providing valuable insights for RD management and the creation of soft‐material‐based X‐ray filters.