Unexpected transformation of n.c.a. [111In]InCl3 in stock solutions into an unreactive [111In]In-species

Carolina Giammei; Nedra Jouini; Marie R Brandt; Stefanie Frey; Thomas L Mindt; Jens Cardinale

doi:10.1016/j.apradiso.2021.110037

Unexpected transformation of n.c.a. [¹¹¹In]InCl₃ in stock solutions into an unreactive [¹¹¹In]In-species

Appl Radiat Isot. 2022 Feb:180:110037. doi: 10.1016/j.apradiso.2021.110037. Epub 2021 Dec 1.

Authors

Carolina Giammei¹, Nedra Jouini¹, Marie R Brandt², Stefanie Frey³, Thomas L Mindt⁴, Jens Cardinale⁵

Affiliations

¹ Ludwig Boltzmann Institute Applied Diagnostics, General Hospital of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria; Department of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 42, 1090, Vienna, Austria; Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria.
² Ludwig Boltzmann Institute Applied Diagnostics, General Hospital of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria; Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria.
³ Ludwig Boltzmann Institute Applied Diagnostics, General Hospital of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria; Department of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 42, 1090, Vienna, Austria.
⁴ Ludwig Boltzmann Institute Applied Diagnostics, General Hospital of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria; Department of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 42, 1090, Vienna, Austria; Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria. Electronic address: Thomas.mindt@lbiad.ac.at.
⁵ Ludwig Boltzmann Institute Applied Diagnostics, General Hospital of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria.

PMID: 34864558
DOI: 10.1016/j.apradiso.2021.110037

Abstract

While performing multiple indium-111 labeling of DOTA-modified peptides from a single batch of [¹¹¹In]InCl₃, inconsistent radiochemical yields were observed. We found that the formation of a radioactive impurity in the [¹¹¹In]InCl₃ stock solution hampered the reactivity of the indium-111 during radiolabeling reactions. The formation of this unknown ¹¹¹In-species could be successfully suppressed by increasing the concentration of chloride ions in the stock solution and [¹¹¹In]InCl₃ was "recovered". Radiolabeling of DOTA-peptides with the stabilized [¹¹¹In]InCl₃ resulted again in acceptable radiochemical yields. In addition, we report convenient iTLC systems that allow distinguishing between [¹¹¹In]InCl₃, the formed unknown ¹¹¹In-species, radiocolloids, and radiolabeled peptides (DOTANOC).

Keywords: DOTA (111)In-labeling; Impurities; Indium-111; Radiochemical yield; Transformation.