Preparation and evaluation of samarium (III) phosphate [153Sm] colloid (SMPC) for possible therapeutic use

A simple method of preparation of a new therapeutic colloid, samarium(III) phosphate-153Sm (SMPC), is reported involving the reaction of carrier-added 153SmCl3 with phosphoric acid. Recovery of the colloid was accomplished by dialysis leading to purification and a radiochemical (RC) yield of more than 90%. The RC purity of purified colloid formulated in isotonic phosphate buffer was more than 99% as assessed by paper chromatography. The product retained its RC purity throughout the period of stability study of 7 days. Complete retention of radioactivity instilled in the rabbit knee joint was observed over the study period of 6 days, with radioactivity in the blood being indistinguishable from the natural background activity. Ninety-six percent of colloidal particles were in the size range of 0.3–2 μm. The promising results demonstrated warrant further studies on SMPC for assessing the suitability for therapy.