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Abstract:
Two DO3A-based ligands appended with the propylphosphonate side arm and their Ln3+ complexes were investigated. Proton relaxometric in vitro studies at 20 MHz and 60 MHz and 37 °C of the Gd3+ complex containing free acid exhibited relative changes of up to 56 in r1 relaxivity when the pH of the medium was changed from 4 to 7. This change is explained by the decrease in the number of coordinated water molecules from two to one. Temperature-dependent relaxivity and NMRD profiles of Gd3+ complexes showed a fast water exchange and a slightly increased rotational correlation time, which is characteristic of phosphonate-containing compounds. Thermodynamic and kinetic studies of the Gd3+ and Eu3+ complexes were performed by means of potentiometry and luminescence spectroscopy. The results indicate that the thermodynamic stability and kinetic inertness of these complexes are sufficient for their in vivo application.
