Stable and high-yielding intrinsic ⁵⁹Fe-radiolabeling of the intravenous iron preparations Monofer and Cosmofer: Intrinsic 59Fe-radiolabeling of Monofer and Cosmofer

Commercial iron supplements Monofer((R)) and Cosmofer((R)) were intrinsically radiolabeled with Fe-59 for the purpose of tracing iron absorption in vivo. Optimized procedures aimed at introducing Fe-59 into the macromolecular construct in a form that was as chemically equivalent to the matrix iron as possible. This was determined by challenging the labeled constructs with diethylenetriaminepentaacetic acid (DTPA) followed by separation by size-exclusion and measurements of radioactivity and iron in the eluted fractions. The final procedures were simple and involved heating aqueous dispersions of the supplements in the presence of [Fe-59]FeCl3 for 24h at 95 degrees C for Monofer, and 85 degrees C for Cosmofer, resulting in radiochemical yields greater than 94%. High performance size exclusion chromatography, UV-VIS spectroscopy, and dynamic light scattering were used to show that the supplements remained unchanged after radiolabeling, underscoring the applicability of the methodology for radiolabeling commercial iron preparations.