Removal of Gadolinium Ions Using Modified Sea Sand Substrate From Water Environment and Impact of Ions on Gadolinium Replacement From Contrast MRI Agent

ABSTRACT Gadolinium in the form of complex compounds is used as a contrast agent in medicine diagnostic for magnetic resonance imaging. Gadolinium‐based contrast agents are divided into linear and macrocyclic substances in ionic or nonionic forms. Gd 3+ toxic ions can be replaced from these compounds by cations such as Fe 3+ and Cu 2+ . Gadolinium inhibits the activity of some enzymes dependent on calcium. The macrocyclic compound binds Gd 3+ more strongly than the linear complexes. The influence of Fe 3+ and Cu 2+ ions on the displacement of Gd 3+ from the macrocyclic MRI contrast agent Gadovist (Gadobutrol) was studied. For comparison with Gadovist transmetallation of Gd 3+ ions, also the removal experiments of Gd 3+ ions themselves from the water environment were performed. For this purpose, sea sand modified by 3‐aminopropyltriethoxysilane was used. These molecules are capable to capture Gd 3+ ions, as was confirmed by ICP‐MS measurements. The prepared samples of modified sea sand were characterized by FTIR and TGA measurements. In the case of Gd 3+ ions alone, a significant decrease in Gd 3+ ions concentration was observed when using the modified sea sand. Depending on the preparation, method used (change of temperature and mixing time, 2 h at 60°C, 20 h at 20°C), different properties were observed regarding the morphology of the sea sand particles and also the amount of APTES molecules bound to the sea sand surface. The efficiency of capture (elimination) of Gd 3+ ions in the case of tap water was almost 90%–100% in the range of pH values between 5 and 9. Initial concentration of Gd 3+ ions was 0.1 mg∙L −1 . The experiments carried out for Gadovist proved that almost no release of Gd 3+ ions to the water environment was observed when testing the influence of two different weight concentrations of Fe 3+ and Cu 2+ , 1 or 10 mg·L −1 for possible displacement Gd 3+ ions (0.1 mg·L −1 ) from the Gadovist and release to the water environment which was confirmed using ICP‐MS measurements and determined concentration of Gd 3+ ions was at the level 1 µg·L −1 .