Lutetium-177 and iodine-131 loaded chelating polymer microparticles intended for radioembolization of liver malignancies

Microspheres as a Carrier System for Therapeutic Embolization Procedures: Achievements and Advances

The targeted delivery of anti-cancer drugs and isotopes is one of the most pursued goals in anti-cancer therapy. One of the prime examples of such an application is the intra-arterial injection of microspheres containing cytostatic drugs or radioisotopes during hepatic embolization procedures. Therapy based on the application of microspheres revolves around vascular occlusion, complemented with local therapy in the form of trans-arterial chemoembolization (TACE) or radioembolization (TARE). The broadest implementation of these embolization strategies currently lies within the treatment of untreatable hepatocellular cancer (HCC) and metastatic colorectal cancer. This review aims to describe the state-of-the-art TACE and TARE technologies investigated in the clinical setting for HCC and addresses current trials and new developments. In addition, chemical properties and advancements in microsphere carrier systems are evaluated, and possible improvements in embolization therapy based on the modification of and functionalization with therapeutical loads are explored.

Neutron Activated Samarium-153 Microparticles for Transarterial Radioembolization of Liver Tumour with Post-Procedure Imaging Capabilities

Introduction

Samarium-153 (¹⁵³Sm) styrene divinylbenzene microparticles were developed as a surrogate for Yttrium-90 (⁹⁰Y) microspheres in liver radioembolization therapy. Unlike the pure beta emitter ⁹⁰Y, ¹⁵³Sm possess both therapeutic beta and diagnostic gamma radiations, making it possible for post-procedure imaging following therapy.

Methods

The microparticles were prepared using commercially available cation exchange resin, Amberlite IR-120 H⁺ (620–830 μm), which were reduced to 20–40 μm via ball mill grinding and sieve separation. The microparticles were labelled with ¹⁵²Sm via ion exchange process with ¹⁵²SmCl₃, prior to neutron activation to produce radioactive ¹⁵³Sm through ¹⁵²Sm(n,γ)¹⁵³Sm reaction. Therapeutic activity of 3 GBq was referred based on the recommended activity used in ⁹⁰Y-microspheres therapy. The samples were irradiated in 1.494 x 10¹² n.cm^-2.s^-1 neutron flux for 6 h to achieve the nominal activity of 3.1 GBq.g^-1. Physicochemical characterisation of the microparticles, gamma spectrometry, and in vitro radiolabelling studies were carried out to study the performance and stability of the microparticles.

Results

Fourier Transform Infrared (FTIR) spectroscopy of the Amberlite IR-120 resins showed unaffected functional groups, following size reduction of the beads. However, as shown by the electron microscope, the microparticles were irregular in shape. The radioactivity achieved after 6 h neutron activation was 3.104 ± 0.029 GBq. The specific activity per microparticle was 53.855 ± 0.503 Bq. Gamma spectrometry and elemental analysis showed no radioactive impurities in the samples. Radiolabelling efficiencies of ¹⁵³Sm-Amberlite in distilled water and blood plasma over 48 h were excellent and higher than 95%.

Conclusion

The laboratory work revealed that the ¹⁵³Sm-Amberlite microparticles demonstrated superior characteristics for potential use in hepatic radioembolization.