In vivo biodistribution and accumulation of ⁸⁹Zr in mice

Introduction: The present investigation focuses on the chemical and biological fate of ⁸⁹Zr in mice. Electrophoreses of ⁸⁹Zr solvated or chelated in different conditions are here presented. The biological fate of mice injected with [⁸⁹Zr]Zr-oxalate, [⁸⁹Zr]Zr-chloride, [⁸⁹Zr]Zr-phosphate, [⁸⁹Zr]Zr-desferrioxamine and [⁸⁹Zr]Zr-citrate is studied with the biodistribution, the clearances and positron emission tomography images. A special focus is also given regarding the quality of ⁸⁹Zr bone accumulation. Methods: Electrophoreses were carried out on chromatography paper and read by gamma counting. Then, the solutions were intravenously injected in mice, imaged at different time points and sacrificed. The bones, the epiphysis and the marrow substance were separated and evaluated with gamma counts. Results: The clearances of [⁸⁹Zr]Zr-chloride and [⁸⁹Zr]Zr-oxalate reached 20% of injected dose (ID) after 6 days whereas [⁸⁹Zr]Zr-phosphate was only 5% of ID. [⁸⁹Zr]Zr-citrate and [⁸⁹Zr]Zr-DFO were noticeably excreted after the first day postinjection (p.i.). [⁸⁹Zr]Zr-chloride and [⁸⁹Zr]Zr-oxalate resulted in a respective bone uptake of ~15% ID/g and~20% ID/g at 8 h p.i. with minor losses after 6 days. [⁸⁹Zr]Zr-citrate bone uptake was also observed, but [⁸⁹Zr]Zr-phosphate was absorbed in high amounts in the liver and the spleen. The marrow cells were insignificantly radioactive in comparison to the calcified tissues. Conclusion: Despite the complexity of Zr coordination, the electrophoretic analyses provided detailed evidences of Zr charges either as salts or as complexes. This study also shows that weakly chelated, ⁸⁹Zr is a bone seeker and has a strong affinity for phosphate.