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| Home > Publications database > Authentically radiolabelled Mn(II) complexes as bimodal PET/MR tracers |
| Poster (Plenary/Keynote) | FZJ-2016-07744 |
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2015
Abstract: Objectives: Hybrid PET/MR imaging will pave the way for a better understanding of physiological and disease mechanisms in preclinical and clinical settings. Authentic radiolabeling of MR contrast agents ensures a fast and simple access to such bimodal tracers. In this case, a ligand chelating a paramagnetic metal ion (e.g. Mn) spiked with the authentic PET isotope (such as 52gMn) leads to a labelled molecule which can be detected with both imaging modalities. Paramagnetic [55Mn(CDTA)]2- shows an excellent compromise between thermodynamic stability, kinetic inertness and MR contrast enhancement [1]. The aim of this work was a proof of principle study of cyclohexanediaminetetraacetic acid (CDTA) ligands as prosthetic groups for Mn-labelled PET/MR tracers.Methods: N.c.a. 52gMn [t1/2: 5.6 d; Eβ+: 575.8 keV (29.6%)] was produced by proton irradiation of a natCr target and purified by cation-exchange chromatography [2]. CDTA radiolabeling with n.c.a. 52gMn2+ was performed in NaOAc buffer (1M, pH 6) at RT and monitored by radio-TLC as well as IC. Purification of the complex was performed by RP-HPLC and a test on stability in NaOAc buffer. A hydroxyalkyl functionalized CDTA ligand was synthesized starting from 3-cyclohexene-1-methanol in 5 steps.Results: The quantitative formation of [52gMn(CDTA)]2- was observed already within 30 min at RT. The complex was stable for at least 48 h at 50 °C. If an isotopic 52g/55Mn2+ mixture was applied the first prototypical manganese based bimodal PET/MR tracer was obtained. Furthermore, the hydroxyalkyl functionalized CDTA ligand was synthesized with an overall yield of 18-25%. Conclusions: Due to the hydrolytic stability and simple preparation of [52g/55Mn(CDTA)]2-, the CDTA ligand should be highly suitable for the preparation of manganese based PET/MR bimodal tracers. Acknowledgements: The authors thank M. Buchholz for production of 52gMnCl2.References: [1] Kalman, F. et al. (2012), Inorg. Chem., 51, 10065.[2] Buchholz, M. et al. (2013), Radiochim. Acta, 101, 491.
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