Radiolabeling of Amberlite IRA-68 Resin Microspheres with Rhenium-188: Optimization and Biodistribution in...

Rhenium-188 (¹⁸⁸Re) is a therapeutic radionuclide with favorable nuclear properties, including high beta energy and a suitable half-life, making it attractive for radiopharmaceutical applications. Solid carriers, such as ion-exchange resins, may improve radionuclide stability, loading efficiency, and controlled delivery.

This study aimed to activate Amberlite IRA-68 anion-exchange resin microspheres, optimize their labeling with rhenium and ¹⁸⁸Re, and evaluate the biodistribution of the radiolabeled microspheres following intratumoral injection in tumor-bearing mice at 24 and 48 h post-administration.

The effects of contact time, temperature, pH, and initial rhenium concentration on labeling efficiency were systematically investigated. Resin labeling was evaluated by elemental composition analysis using a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray (EDX) analyzer. Radiochemical purity was assessed by instant thin-layer chromatography (ITLC). Activity distribution in mouse organs was assessed using the ISOMED 1010 dose calibrator.

The results demonstrated high labeling efficiency; under optimal conditions (rhenium initial concentration 10 ppm, pH 7, 25 °C, 120 min), rhenium uptake reached approximately 98%. Following intratumoral administration, the radiolabeled microspheres showed high tumor retention (5.39%ID/g at 24 h), whereas radioactivity in the blood and normal organs remained relatively low. This retention indicates localized persistence of the injected microspheres rather than active biological targeting. These findings support the potential of Amberlite IRA-68 resin microspheres as an effective carrier for ¹⁸⁸Re-based radiopharmaceutical applications.

In this study, Amberlite IRA-68 anion-exchange resin microspheres were successfully evaluated as a carrier system for rhenium and rhenium-188. The results demonstrated high labeling efficiency, reaching approximately 98% under optimized conditions (10 ppm, pH 7, 25 °C, 120 min), indicating a strong affinity between the resin and perrhenate ions. The biodistribution study demonstrated that ¹⁸⁸Re-labeled Amberlite IRA-68 microspheres showed favorable in vivo characteristics following intratumoral administration. The radiopharmaceutical showed high tumor accumulation at 24 h (%ID/g = 5.39), with persistent retention at 48 h and low blood activity, indicating minimal systemic leakage and limited uptake in critical organs.