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

The short half-life of (212)Bi and (213)Bi limits the application of these radionuclides in α radionuclide therapy. The labeling of biomolecules with (212)Pb (mother nuclide of (212)Bi) instead of (212)Bi or (213)Bi has the advantage of obtaining a conjugate with a half-life of 10.6 h, compared with of 60 min for (212)Bi or 46 min for (213)Bi. Previous attempts to prepare a potential in vivo generator with (212)Pb 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 (212)Pb complexes with eight selected polydentate ligands, which demonstrate high affinity for 3+ metal cations. From the ligand studied DOTP and BAPTA show a sufficient (212)Pb labeling yields but only (212)Pb–DOTP complex is stable in isotonic solution of sodium chloride making this way radioactivity level of released (212)Bi 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.