An electrochemical approach for removal of radionuclidic contaminants of Eu from Sm for effective use in metastatic bone pain palliation.

INTRODUCTION

Thermal neutron activation of Sm [Sm(n,γ)Sm] using natural or isotopically enriched (by Sm) samarium target is the established route for production of Sm used for preparation of Sm-EDTMP for pain palliation in cancer patients with disseminated bone metastases. However, some long-lived radionuclidic contaminants of Eu, such as, Eu (t=8.6y) are also produced during the target activation process. This leads to detectable amount of Eu radionuclidic contaminants in patients' skeleton even years after administration with therapeutic doses of Sm-EDTMP. Further, the presence of such contaminants in Sm raises concerns related to radioactive waste management. The aim of the present study was to develop and demonstrate a viable method for large-scale purification of Sm from radionuclidic contaminants of Eu.

METHODS

A radiochemical separation procedure adopting electroamalgamation approach has been critically evaluated. The influence of different experimental parameters for the quantitative removal radionuclidic contaminants of Eu from Sm was investigated and optimized. The effectiveness of the method was demonstrated by purification of ~37 GBq of Sm in several batches. As a proof of concept, Sm-EDTMP was administered in normal Wistar rats and ex vivo γ-spectrometry of bone samples were carried out.

RESULTS

After carrying out the electrolysis under the optimized conditions, the radionuclidic contaminants of Eu could not be detected in purified Sm solution by γ-spectrometry. The overall yield of Sm obtained after the purification process was >85%. The reliability of this approach was amply demonstrated in several batches, wherein the performance remained consistent. Ex vivo γ-spectrometry of bone samples of Wistar rats administered with Sm-EDTMP (prepared using electrochemically purified Sm) did not show photo peaks corresponding to radionuclidic contaminants of Eu.

CONCLUSIONS

A viable electrochemical strategy for the large-scale purification of Sm from radionuclidic contaminants of Eu has been successfully developed and demonstrated.