Preparation of Medical ²²⁸Th-²²⁴Ra Radionuclide Generator Based on SiO₂@TiO₂ Microspheres

²²⁴Ra (T_1/2 = 3.63 d), an α-emitting radionuclide, holds significant promise in cancer endoradiotherapy. Current ²²⁴Ra-related therapy is still scarce because of the lack of reliable radionuclide supply. The ²²⁸Th-²²⁴Ra radionuclide generator can undoubtedly introduce continuous and sustainable availability of ²²⁴Ra for advanced nuclear medicine. However, conventional metal oxides for such radionuclide generators manifest suboptimal adsorption capacities for the parent nuclide, primarily attributable to their limited surface area. In this work, core-shell SiO₂@TiO₂ microspheres were proposed to develop as column materials for the construction of a ²²⁸Th-²²⁴Ra generator. SiO₂@TiO₂ microspheres were well prepared and systematically characterized, which has also been demonstrated to have good adsorption capacity to ²²⁸Th and very weak binding affinity toward ²²⁴Ra via simulated chemical separation. Upon introducing ²²⁸Th-containing solution onto the SiO₂@TiO₂ functional column, a ²²⁸Th-²²⁴Ra generator with excellent retention of the parent radionuclide and ideal elution efficiency of daughter radionuclide was obtained. The prepared ²²⁸Th-²²⁴Ra generator can produce ²²⁴Ra with high purity and medical usability in good elution efficiency (98.72%) even over five cycles. To the best of our knowledge, this is the first time that the core-shell mesoporous materials have been applied in a radionuclide generator, which can offer valuable insights for materials chemistry, radiochemical separation, and biological medicine.