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

The short half-life of Bi and Bi limits the application of these radionuclides in α radionuclide therapy. The labeling of biomolecules with Pb (mother nuclide of Bi) instead of Bi or Bi has the advantage of obtaining a conjugate with a half-life of 10.6 h, compared with of 60 min for Bi or 46 min for Bi. Previous attempts to prepare a potential in vivo generator with 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 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 Pb labeling yields but only Pb-DOTP complex is stable in isotonic solution of sodium chloride making this way radioactivity level of released 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 M.