Novel and Efficient Preparation of Precursor [¹⁸⁸Re(OH₂)₃(CO)₃]⁺ for the Labeling of Biomolecules

A novel and efficient method for preparing 188Re(I) tricarbonyl precursor [188Re(OH2)3(CO)3]+ has been developed by reacting [188Re]perrhenate with Schibli’s kit in the presence of borohydride exchange resin (BER) as a reducing agent and an anion scavanger. The precursor was produced in more than 97% yield by reacting a solution of tetrahydroborate exchange resin (BER, 3 mg), borane-ammonia (BH3âNH3, 3 mg), and potassium boranocarbonate (K2[H3BCO2], 3 mg) in 0.9% saline with a solution of sodium perrhenate (Na188ReO4) with up to 50 MBq and concentrated phosphoric acid (85%, 7 íL) at 60 °C for 15 min. HPLC and TLC revealed 0% unreacted [188Re]-perrhenate ion and <3% of colloidal 188ReO2. Since the precursor is produced with high radiochemical purity and labeling efficiency under the milder conditions than those required for the conventional reducing agents, the latter can be replaced.