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

Abstract

Co-55 (T 1/2 =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 [55 Co]diethylenetriaminepentacetate ([ 55 Co]DTPA). Optimization studies were performed using Co-57 due to its longer half-life. Cobalt-57 (T 1/2 =271.79 d) was produced by irradiation of a natural nickel target with 150 μA current of 22 MeV protons. The 57 Co was separated from the irradiated target material using a no carrier added method with a radiochemical yield of >97%. The 55 Co 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 [ 55 Co]complex were prepared (radiochemical yield>80%) starting with 55 CoOAc 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 stable in the final product and in the presence of human serum at 37°C up to 15 h. [55 Co]DTPA was successively used in the radiolabeling of red blood cells for PET 1 diagnostic studies.

Capture of Co(II) from its aqueous EDTA-chelate by DTPA-modified silica gel and chitosan

“…The idea behind the mechanisms presented here was that the most unstable solution chelate reacted with the surface group with the highest affinity towards positive metal ions. It was also assumed that DTPA surface groups formed rather similar coordination compounds with Co(II) ions as they would have formed in the solution phase [39], and the above equations are simplified presentations of coordination. If the stability constant of surface DTPA-groups was assumed to be near that of the solution species (pK: 26.53 [32]) the previous mechanisms would also be favorable since the stability constants of Co(II)EDTA-chelates varied from 18 to 23.5 [32], [Table S2].…”

Yields of Photo-Proton Reactions on Nuclei of Nickel and Separation of Cobalt Isotopes from Irradiated Targets

“…At the same time, there are works dedicated to the separation of cobalt isotopes from cyclotron-irradiated nickel targets. In these works, Ni(II) and Co(II) were separated using anion exchange resin Dowex AG-1X8 [11,14,[19][20][21][22][23][24][25][26][27] and using extraction chromatography sorbent based on diglycolamide, where Co(II) was obtained in 3 M HCl [28]. The best results were achieved in the last case, the yield of cobalt was 92%, separation factors of cobalt from different impurities varied from 8•10 2 to 2•10 4 , Cobalt isotopes (including 55 Co) can also be obtained using an electron accelerator-by irradiation of nickel.…”

“…At the same time, there are works dedicated to the separation of cobalt isotopes from cyclotron-irradiated nickel targets. In these works, Ni(II) and Co(II) were separated using anion exchange resin Dowex AG-1X8 [11,14,[19][20][21][22][23][24][25][26][27] and using extraction chromatography sorbent based on diglycolamide, where Co(II) was obtained in 3 M HCl [28]. The best results were achieved in the last case, the yield of cobalt was 92%, separation factors of cobalt from different impurities varied from 8•10 2 to 2•10 4 , and the process lasted for 2 h. It is worth mentioning that the main task of these works was more difficult than just separation of cobalt and nickel: first, irradiation of nickel also results in the formation of copper isotopes; second, nickel was usually applied via electrodeposition as a coating to a metal plate, irradiation of which also led to impurities.…”