Rare earth oxide ternary systems of Ce, Nd, Sm, La, Pr, and Si: potential use in anticancer drugs

Rare earth elements play an important role in industrial and biomedical applications due to their outstanding optical, electrical, and magnetic properties. Here, we report the first-time synthesis of ternary oxide systems based on CeO₂–SiO₂ doped with LaO_x, PrO_x, NdO_x, and SmO_x, using a low-temperature sol–gel method that allows better incorporation of rare earth elements into the silica network without the need for surfactants or organic ligands, differing from conventional nanoparticle-based approaches. EDS and XRD analyses confirmed the successful integration of rare earth elements, and SEM revealed micron-sized particles (2–20 μm) instead of the typically reported nanoscale systems. Thermal analysis showed that these ternary systems possess enhanced thermal stability compared to CeO₂–SiO₂ binary systems, supporting potential high-temperature applications. Importantly, cytotoxicity assays against HCT-116 colorectal cancer cells demonstrated that CeO₂–SiO₂ and CeO₂–SiO₂–NdO_x systems exhibited superior anticancer activity (IC₅₀ values lower than that of the standard drug etoposide), a bioactivity level not previously observed for similar oxide systems. This work introduces a novel material platform with dual optoelectronic and biomedical potential, opening new pathways for rare-earth-based cancer therapeutics.