Novel and efficient preparation of precursor [188Re(OH2)3(CO)3]+ for the labeling of biomolecules

A novel and efficient method for preparing Re-188(1) tricarbonyl precursor [Re-118(OH2)(3)(CO)(3)](+) has been developed by reacting [Re-188]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 (BH(3)center dot NH3, 3 mg), and potassium boranocarbonate (K-2[H3BCO2], 3 mg) in 0.9% saline with a solution of sodium perrhenate ((NaReO4)-Re-188) with up to 50 MBq and concentrated phosphoric acid (85%, 7 mu L) at 60 degrees C for 15 min. HPLC and TLC revealed 0% unreacted [Re-188]perrhenate ion and < 3% of colloidal (ReO2)-Re-188. 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.