Quantum-Dot Ceramic Composites for Oxidative Stress Mitigation under Broad-Spectrum Radiation Exposure

Nanomaterials offer a promising approach to mitigating radiation-induced oxidative stress by scavenging reactive oxygen species (ROS). However, developing a nanomaterial that provides protection across a wide range of radiation conditions is challenging due to the photoelectric effects linked to the atomic number (Z) of the materials. Quantum dots (QDs) in a composite system, owing to their small size and when used at low concentrations, minimize photoelectric effects and secondary electron generation. In this study, cerium oxide (CeO₂) QDs were combined with low-Z yttrium oxide (Y₂O₃) to create a nanocomposite (NC) (henceforth CeO₂ QDs-Y₂O₃) that exploits the synergistic effects of both materials, providing protection across a broader spectrum of radiation. CeO₂ QDs-Y₂O₃ demonstrated superior ROS scavenging than individual CeO₂ and Y₂O₃ under nonradiative conditions, particularly for hydroxyl radicals (^•OH) and hydrogen peroxide (H₂O₂), two primary ROS generated under radiation. This improved performance, due to increased oxygen vacancies and a higher Ce³⁺/Ce⁴⁺ ratio, indicates that these properties could help protect cells from oxidative stress during radiation exposure. Radioprotection analysis using the linear-quadratic (LQ) model revealed that the NC provided effective protection at both 150 kVp and 10 MV radiation energies. At 150 kVp, the obtained protection enhancement ratio (PER) values at 10% cell survival for CeO₂ QDs-Y₂O₃, Y₂O₃, and CeO₂ were 1.07, 1.16, and 0.89, respectively, suggesting that the radioprotection afforded by Y₂O₃ in the NC outweighed the radiosensitization of the encrusted CeO₂ QDs. Additionally, despite the higher PER of Y₂O₃, the NC displayed increased biocompatibility toward the human keratinocyte HaCaT cell line in the absence of radiation compared to Y₂O₃. At 10 MV, where photoelectric effects are minimal, the NC outperformed both individual components, yielding a PER of 1.28, or a 28% dose enhancement compared to 12% for Y₂O₃ alone and 19% for CeO₂. This study highlights the potential of CeO₂ QDs-Y₂O₃ as a broad-spectrum radioprotective agent, offering enhanced biocompatibility and effective protection against radiation-induced oxidative stress across broad-ranging radiation conditions.