Preparation and In Vitro Evaluation of Neutron-Activated, Theranostic Samarium-153-Labeled Microspheres for Transarterial Radioembolization of Hepatocellular Carcinoma and Liver Metastasis.

INTRODUCTION

Transarterial radioembolization (TARE) has been proven as an effective treatment for unresectable liver tumor. In this study, neutron activated, Sm-labeled microspheres were developed as an alternative to Y-labeled microspheres for hepatic radioembolization. Sm has a theranostic advantage as it emits both therapeutic beta and diagnostic gamma radiations simultaneously, in comparison to the pure beta emitter, Y.

METHODS

Negatively charged acrylic microspheres were labeled with Sm ions through electrostatic interactions. In another formulation, the Sm-labeled microsphere was treated with sodium carbonate solution to form the insoluble Sm carbonate (SmC) 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 Sm- and SmC-labeled microspheres achieved activity of 2.53 ± 0.08 and 2.40 ± 0.13 GBq·g, respectively, immediate after 6 h neutron activation in the neutron flux of 2.0 × 10 n·cm·s. 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 Sm in the SmC-labeled microspheres was excellent (99% in distilled water and saline; ~97% in human blood plasma), which was higher than the Sm-labeled microspheres (95% and ~85%, respectively).

CONCLUSION

SmC-labeled microspheres have demonstrated excellent properties for potential application as theranostic agents for hepatic radioembolization.