Search of ligands suitable for 212Pb/212Bi in vivo generators.

The short half-life of 212Bi and 213Bi limits the application of these radionuclides in α radionuclide therapy. The labeling of biomolecules with 212Pb (mother nuclide of 212Bi) instead of 212Bi or 213Bi has the advantage of obtaining a conjugate with a half-life of 10.6 h, compared with of 60 min for 212Bi or 46 min for 213Bi. Previous attempts to prepare a potential in vivo generator with 212Pb complexed by the DOTA chelator failed, because about 36 % of Bi was reported to escape as a result of the radioactive decay [Formula: see text]. Herein, we report studies on the stability of the 212Pb complexes with eight selected polydentate ligands, which demonstrate high affinity for 3+ metal cations. From the ligand studied DOTP and BAPTA show a sufficient 212Pb labeling yields but only 212Pb-DOTP complex is stable in isotonic solution of sodium chloride making this way radioactivity level of released 212Bi is below the limit of detection. It should be emphasized that the DOTP complex is stable only in the case when the concentration of free DOTP exceeds 10-4 M.