Tc-99m and Re-186 complexes of tetraphosphonate ligands and their biodistribution pattern in animal models

The syntheses of four cr-aminomethyl phosphonates and their complexation studies with Tc-99m and Re-186/188 are reported. Complexation conditions were standardized to give maximum yields, which ranged from 90-97%. The yields of complexation were estimated by paper chromatography, The Tc-99m complexes were stable for more than 4 h, while the Re-186/188 complexes were stable for 3-8 days when stored at 4 degreesC. Biodistribution of these complexes in Wistar rats were carried out, and the uptake in bone and other soft tissue are detailed. Bone uptake of the Tc-99m complexes varied from 40-60% at 30 min postinjection depending on the ligands. The uptake in soft tissue was minimum with all the complexes. A comparison of the biodistribution studies of the Tc-99m complexes with that of the well-established radiopharmaceutical Tc-99m-MDP was carried out for the purpose of evaluating the efficacy of the radiopharmaceutical preparation with the complexes of these ligands. The bone uptake of the Re-186/188 complexes varied from 19-28% corresponding to 1.6-3% per g at 3 h postinjection. The residual activity in both Tc-99m and Re-186/188 complexes showed renal clearance. (C) 2001 Elsevier Science Inc. All rights reserved.