Preparation of Medical 228 Th- 224 Ra Radionuclide Generator Based on SiO 2 @TiO 2 Microspheres.

224 Ra ( T 1/2 = 3.63 d), an α-emitting radionuclide, holds significant promise in cancer endoradiotherapy. Current 224 Ra-related therapy is still scarce because of the lack of reliable radionuclide supply. The 228 Th- 224 Ra radionuclide generator can undoubtedly introduce continuous and sustainable availability of 224 Ra 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 SiO 2 @TiO 2 microspheres were proposed to develop as column materials for the construction of a 228 Th- 224 Ra generator. SiO 2 @TiO 2 microspheres were well prepared and systematically characterized, which has also been demonstrated to have good adsorption capacity to 228 Th and very weak binding affinity toward 224 Ra via simulated chemical separation. Upon introducing 228 Th-containing solution onto the SiO 2 @TiO 2 functional column, a 228 Th- 224 Ra generator with excellent retention of the parent radionuclide and ideal elution efficiency of daughter radionuclide was obtained. The prepared 228 Th- 224 Ra generator can produce 224 Ra 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.