Gadolinium-based contrast agents: From gadolinium complexes to colloidal systems

Nowadays, most of the clinically used contrast agents are based on the use of gadolinium molecular complexes like Dotarem®, Magnevist®…. Nevertheless, developing new gadolinium based contrast agents with enhanced relaxivity properties while avoiding gadolinium release in human tissue is still of paramount importance. We describe here two promising families of contrast agents which meets these criteria and compared their properties to the ones of clinically used Gd complexes. The first one is based on contrast agents obtained by covalent or non-covalent interactions of gadolinium molecular complexes with polymers, nanoparticles or liposomes. The second family is based on the formation of gadolinium particles (Gd2O3, GdPO4, NaGdF4, GdF3…) of controlled morphology and composition. The performance of these two families is described as well as their development perspective.