A report on Se/Eu-doped hydroxyapatite: crystal structure analysis, biological property assessment, and applications in osteosarcoma inhibition and bioimaging

Abstract

A significant clinical issue in bone diseases is the treatment of post-operative osteosarcoma and the repair of bone defects. Hydroxyapatite (HAp) is a natural bone component with pro-osteogenic properties. Selenium (Se)-doped HAp can successfully prevent osteosarcoma in vitro and in vivo. However, the in vivo distribution and metabolism of Se-doped HAp nanoparticles have not been fully analyzed. The use of europium (Eu)-doped HAp as a fluorescence bioimaging tool is possible for non-destructive observation in vitro and in vivo, but it is still uncommon in osteosarcoma therapy. This study is aimed at creating a new material that will fill the gap in both osteosarcoma inhibition and bioimaging by doping Se and Eu into HAp. In this study, HAp–Se/Eu was hydrothermally synthesized in one step, and the doping of Se as SeO₃²⁻ partially instead of PO₄³⁻ and Eu as Eu³⁺ partially instead of Ca²⁺ into the HAp lattice structures was confirmed by Rietvelt refinement, XPS, and other techniques. As a result, the inhibition rate of HAp–Se on osteosarcoma cells was up to 80%; HAp–Eu showed red light at 396 nm excitation; HAp–Se–Eu showed improved anti-tumor performance and fluorescence, and its osteosarcoma cell inhibition rate exceeded 90%, allowing for tumor cell imaging. These findings demonstrate that Se and Eu double-element-doped HAp successfully conferred nanomaterials with osteosarcoma inhibition and bioimaging properties, and these nanoparticles could be used for postoperative treatment and imaging of osteosarcoma resection.