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

A novel and efficient method for preparing the 188Re(I) tricarbonyl precursor [188Re(OH2)3(CO)3]+ has been developed by reaction of 188Re perrhenate with Schibli's reagent in the presence of borohydride exchange resin (BER) as a reducing agent and an anion scavenger. The precursor was produced in more than 97% yield by reacting a solution of BER (3 mg), borane ammonia (BH3·NH3, 3 mg) and potassium boranocarbonate (K2[BH3CO2], 3 mg) in 0.9% saline with a solution of sodium perrhenate (Na188ReO4) with up to 50 MBq of activity and concentrated phosphoric acid (85%, 7 μL) at 60 deg C for 15 min. HPLC and TLC revealed the complete consumption of unreacted 188Re perrhenate ion and less than 3% colloidal 188ReO2. The precursor is produced with high radiochemical purity and labelling efficiency under milder conditions than those required for conventional reducing agents. (author)