Introduction: The aim of the present study was to develop and demonstrate a viable method for the reactor production of ¹⁶⁹Er with acceptable specific activity using moderate flux reactor and its purification from ¹⁶⁹Yb following electrochemical pathway based on mercury-pool cathode to avail ¹⁶⁹Er in radionuclidically pure form essential for its therapeutic use. Methods: Erbium-169 was produced in reactor by neutron bombardment of isotopically enriched (98.2% in ¹⁶⁸Er) erbium target at a thermal neutron flux of ~8 × 10¹³ n.cm^-2.s^-1 for 21 d. A thorough optimization of irradiation parameters including neutron flux, irradiation time and target cooling time was carried out. The influence of different experimental parameters for the quantitative removal ¹⁶⁹Yb from ¹⁶⁹Er was investigated, optimized and based on the results; a two-cycle electrochemical separation procedure was adopted. The suitablility of purified ¹⁶⁹Er for application in radiation synovectomy and bone pain palliation was ascertained by carrying out radiolabeling studies with hydroxypaptite (HA) particles and 1,4,7,10- tetraazacyclododecane-1,4,7,10-tetraaminomethylene phosphonic acid (DOTMP), respectively.
Results: Thermal neutron irradiation of 10 mg of isotopically enriched (98.2% in 168Er) erbium target at a flux of ~8 × 10¹³ n.cm^-2.s^-1 for 21 d followed by a two-step electrochemical separation of ¹⁶⁹Yb impurity yielded ~3.7 GBq (100 mCi) of ¹⁶⁹Er with a specific activity of ~370 MBq/mg (10 mCi/mg) and radionuclidic purity of >99.99%. The reliability of this approach was amply demonstrated by performing several production batches, where the performance of each batch remained consistent. The utility of the purified ¹⁶⁹Er was demonstrated in the radiolabeling studies with HA particles and DOTMP, wherein both the radiolabeled products were obtained with high radiolabeling yield (>99%).
Conclusions: A viable strategy for the batch production and purification of ¹⁶⁹Er, suitable for therapeutic applications, has been developed and demonstrated.