Labelling of ethylenediaminetetramethylene phosphonic acid (EDTMP) with ¹⁷⁵Yb

Ytterbium-175 (¹⁷⁵Yb) is one of radioisotopes that can be used for therapy due to its β-particle emission (T_1/2 = 4.2 d, E_β(max) = 480 keV). Beside that, this radioisotope also emits γ-rays of 113 keV (1.9%), 282 keV (3.1%) and 396 keV (6.5%) which are suitable energy for imaging as long as therapeutic applications. EDTMP could be labeled with radionuclide of ¹⁷⁵Yb as an alternative radiopharmaceutical for bone pain palliation due to bone metastases. Labeling of ethylenediaminetetramethylenephosphonic acid with ¹⁷⁵Yb has been studied. Various influential parameters in labeling conditions i.e. the amount of EDTMP ligand, the pH of labeling, incubation time and the amount of ¹⁷⁵Yb solution were studied in order to obtain high labeling efficiency of ¹⁷⁵Yb-EDTMP. The labeling efficiency was obtained by radiochemical purity that was determined by paper chromatography and paper electrophoresis techniques. The optimum labeling condition was obtained at pH 7, 4 mg of EDTMP ligand, 100 µL (105 µg; 0.6 µmol) of ¹⁷⁵Yb solution and 30 minutes incubation time at room temperature. The complex formed was gave maximum labeling efficiency of 98.81 ± 0.15%. Owing to the results, EDTMP ligand can be labeled with ¹⁷⁵Yb radionuclide with labeling efficiency more than 95%. (author)