Influence of metal ions on the 44Sc-labeling of DOTATATE

Abstract

The aim of the study was to evaluate the labeling yield of 44Sc-DOTATATE radiobioconjugate when the labeling is performed in the presence of various amounts of competing metallic impurities. In the case of Ca2+ and Al3+ the effect is irrelevant, which is understandable considering the low stability constant of Ca2+-DOTA and Al3+-DOTA complexes. However, the presence of Fe2+/3+, Zn2+ and Cu2+ cations very strongly influences the efficiency of the 44Sc-DOTATATE formation. Surprisingly, while the Zn2+-DOTA stability constants is the smallest, Zn2+ cations competes more strongly with Sc3+ than Fe2+,3+ and Cu2+ at the DOTATATE coordination site.