Preparation and Evaluation of [55Co](II)DTPA for Blood Cell Labeling

Abstract

Co-55 (T1/2=17.53 h) was produced by 150 μA irradiation of a natural nickel target by 15 MeV protons and was separated from the irradiated target material by two ion exchange chromatography steps and was used for the preparation of [55Co]diethylenetriaminepentacetate ([55Co]DTPA). Optimization studies were performed using Co-57 due to its longer half-life. Cobalt-57 (T1/2=271.79 d) was produced by irradiation of a natural nickel target with 150 μA current of 22 MeV protons. The 57Co was separated from the irradiated target material using a no carrier added method with a radiochemical yield of >97%. The 55Co was separated from the irradiated target material using a two step method with a radiochemical yield of >95%. Both products were controlled for radionuclide and chemical purity. The solutions of [55Co]complex were prepared (radiochemical yield>80%) starting with 55CoOAc ligand at room temperature after 30 min. RTLC showed the radiochemical purity of more than 99%. Specific activity was obtained about 9.1 TBq/mmol. The tracer showed to be sta- ble in the final product and in the presence of human serum at 37°C up to 15 h. [55Co]DTPA was successively used in the radiolabeling of red blood cells for PET1 diagnostic studies.