Cyclopentadienyl technetium (Tc-99m) tricarbonyl piperidine conjugates: biodistribution and imaging studies

Synthesis of organometallic complexes of Tc-99m using the precursor ligands N-methylpiperidino-4[(bispentahaptocyclopentadienyl)iron] carboxylate and N-(isopropyl)-piperidino-4[(bispentahaptocyclopentadienyl)iron]carboxylate is described. The labelling method involved reaction of the ligands with (T cO4-)-Tc-99m in the presence of Mn(CO)(5)Br in dimethyl formamide at 150 de greesC for 1 h in an oil bath. The purification of the complexes was carrie d out by preparative TLC using ether/n-butyl methyl amine (95:5) solvent sy stem. The purified complexes were characterized by HPLC using acetonitrile: water (80:20) solvent system in a PRP-1 column in which both the complexes were eluted as single peaks. Biodistribution studies carried out in rats s howed 2.4 +/- 0.14 and 1.1 +/- 0.42% of the injected activity in the brain tissue 5 min p.i. for cytectrene I and II, respectively. The brain to blood activity ratio was > 15:1 for both the complexes at 5 min p.i. Scintigraph ic studies in rabbits showed significant uptake of the activity in the brai n with fast clearance from blood. The complexes warrant further investigati on as agents for brain imaging. Copyright (C) 2001 John Wiley & Sons, Ltd.