Separation of ~(90)Nb from zirconium target for application in immuno-PET

摘要

Fast progressing immuno-PET asks to explore new radionuclides. One of the promising candidates is ~(90)Nb. It has a half-life of 14.6 h that allows visualizing and quantifying biological processes with medium and slow kinetics, such as tumor accumulation of antibodies and antibodies fragments or drug delivery systems and nanoparticles. ~(90)Nb exhibits a positron branching of 53% and an average kinetic energy of emitted positrons of E_(mean) = 0.35MeV. Currently, radionuclide production routes and Nb~V labeling techniques are explored to turn this radionuclide into a useful imaging probe.However, efficient separation of ~(90)Nb from irradiated targets remains in challenge. Ion exchange based separation of ~(90)Nb from zirconium targets was investigated in systems AG 1 × 8 – HCl/H_2O_2 and UTEVA-HCl. 95Nb (t_(1/2)= 35.0 d), ~(95)Zr (t_(1/2)= 64.0 d) and ~(92)mNb (t_(1/2)= 10.15 d) were chosen for studies on distribution coefficients. Separation after AG 1 × 8 anion exchange yields 99% of ~(90/95)Nb. Subsequent use of a solidphase extraction step on UTEVA resin further decontaminates ~(90/95)Nb from traces of zirconium with yields 95% of ~(90/95)Nb. A semi-automated separation takes one hour to obtain an overall recovery of ~(90/95)Nb of 90%. The amount of Zr was reduced by factor of 10~8. The selected separation provides rapid preparation (< 1h) of high purity ~(90)Nb appropriate for the synthesis of ~(90)Nb-radiopharmaceuticals, relevant for purposes of immuno-PET. Applying the radioniobium obtained, ~(90/95)Nb-labeling of a monoclonal antibody (rituximab) modified with desferrioxamine achieved labeling yields of> 90%after 1 h incubation at room temperature.