Promising strategies for Gd-based responsive magnetic resonance imaging contrast agents.

Magnetic resonance imaging is a powerful imaging modality that is often coupled with paramagnetic contrast agents based on gadolinium to enhance sensitivity and image quality. Responsive contrast agents are key to furthering the diagnostic potential of MRI, both to provide anatomical information and to discern biochemical activity. Recent design of responsive gadolinium-based T₁ agents has made interesting progress, with the development of novel complexes which sense their chemical environment through changes in the coordination of water molecules, the molecular tumbling time or the number of metal centres. Particular promising design strategies include the use of multimeric systems, and the development of dual imaging probes.