Synthesis, characterization and comparative study of aminophosphonate chelates of gadolinium(III) ions as magnetic resonance imaging contrast agents

Abstract

Gadolinium(III) complexes of aminophosphonates, including a novel ligand L⁴H₈, have been investigated as potential contrast agents for NMR imaging. Water ¹H relaxivities at 10 and 200 MHz were determined and luminescence measurements, on Tb^III complexes, allowed the determination of the number of coordinated H₂O molecules. The complexes bound strongly to hydroxyapatite, suggesting possible targetting to bone <i>in vivo</i>. This was confirmed by ¹⁵³Gd tracer studies with the most favourable biodistribution in rats being shown by gadolinium(III) ethylenediamine-N,N,N′,N′-tetrakis(methylenephosphonate).