METHODS: The [152Sm]Sm2O3-PS microspheres were synthesized using solid-in-oil-in-water solvent evaporation. The microspheres underwent neutron activation using a 1 MW open-pool research reactor to produce radioactive [153Sm]Sm2O3-PS microspheres via 152Sm(n,γ)153Sm reaction. Physicochemical characterization, gamma spectroscopy and in-vitro radionuclide retention efficiency were carried out to evaluate the properties and stability of the microspheres before and after neutron activation.
RESULTS: The [153Sm]Sm2O3-PS microspheres achieved specific activity of 5.04 ± 0.52 GBq·g-1 after a 6 h neutron activation. Scanning electron microscopy and particle size analysis showed that the microspheres remained spherical with an average diameter of ~33 μm before and after neutron activation. No long half-life radionuclide and elemental impurities were found in the samples. The radionuclide retention efficiencies of the [153Sm]Sm2O3-PS microspheres at 550 h were 99.64 ± 0.07 and 98.76 ± 1.10% when tested in saline solution and human blood plasma, respectively.
CONCLUSIONS: A neutron-activated [153Sm]Sm2O3-PS microsphere formulation was successfully developed for potential application as a theranostic agent for liver radioembolization. The microspheres achieved suitable physical properties for radioembolization and demonstrated high radionuclide retention efficiency in saline solution and human blood plasma.
METHODS: Negatively charged acrylic microspheres were labeled with 152Sm ions through electrostatic interactions. In another formulation, the Sm-labeled microsphere was treated with sodium carbonate solution to form the insoluble 152Sm carbonate (152SmC) salt within the porous structures of the microspheres. Both formulations were neutron-activated in a research reactor. Physicochemical characterization, gamma spectrometry, and radiolabel stability tests were carried out to study the performance and stability of the microspheres.
RESULTS: The Sm- and SmC-labeled microspheres remained spherical and smooth, with a mean size of 35 µm before and after neutron activation. Fourier transform infrared (FTIR) spectroscopy indicated that the functional groups of the microspheres remained unaffected after neutron activation. The 153Sm- and 153SmC-labeled microspheres achieved activity of 2.53 ± 0.08 and 2.40 ± 0.13 GBq·g-1, respectively, immediate after 6 h neutron activation in the neutron flux of 2.0 × 1012 n·cm-2·s-1. Energy-dispersive X-ray (EDX) and gamma spectrometry showed that no elemental and radioactive impurities were present in the microspheres after neutron activation. The retention efficiency of 153Sm in the 153SmC-labeled microspheres was excellent (~99% in distilled water and saline; ~97% in human blood plasma), which was higher than the 153Sm-labeled microspheres (~95% and ~85%, respectively).
CONCLUSION: 153SmC-labeled microspheres have demonstrated excellent properties for potential application as theranostic agents for hepatic radioembolization.