Lanthanide-Based Organic Salts: Synthesis, Characterization, and Cytotoxicity Studies

Abstract

The formulation of magnetic ionic liquids (MILs) or organic salts based on lanthanides as anions has been explored. In this work, a set of choline-family-based salts, and two other, different cation families, were combined with Gadolinium(III) and Terbium(III) anions. Synthetic methodologies were previously optimized, and all organic salts were obtained as solids with melting temperatures higher than 100 °C. The magnetic moments obtained for the Gd(III) salts were, as expected, smaller than those obtained for the Tb(III)-based compounds. The values for Gd(III) and Tb(III) magnetic salts are in the range of 6.55-7.30 MB and 8.22-9.34 MB, respectively. It is important to note a correlation between the magnetic moments obtained for lanthanides, and the structural features of the cation. The cytotoxicity of lanthanide-based salts was also evaluated using 3T3, 293T, Caco2, and HepG2 cells, and it was revealed that most of the prepared compounds are not toxic.

Keywords: MRI contrast agents; cytotoxicity; gadolinium salts; magnetic organic salts; terbium salts.

Figure 1

The structures of the biocompatible organic salts synthesized in this work.

Scheme 1

The synthetic methodology adopted to develop lanthanide-based magnetic salts.

Figure 2

The variation in μ_eff with the cation structural properties for (a) Gd(III)-, and (b) Tb(III)-based magnetic organic salts.

Figure 3

The cytotoxicity of Gd(III)- and Tb(III)-based organic salts (100 µg/mL) on 3T3 and 293T cells’ viability after treatment for 24 h. Values represent mean ± standard error of the mean (SEM) of at least three independent experiments carried out in triplicate. Symbols represent significant differences (ANOVA, Dunnett’s test, p < 0.05) compared to the control (*).

Figure 4

The cytotoxicity of Gd(III)- and Tb(III)-based organic salts (100 µg/mL) on HepG2 and Caco-2 cells’ viability after treatment for 24 h. Values represent mean ± standard error of the mean (SEM) of at least three independent experiments carried out in triplicate. Symbols represent significant differences (ANOVA, Dunnett’s test, p < 0.05) compared to the control (*).