Investigations into the Effects of Linker Length Elongation on the Behaviour of Calcium-responsive MRI Probes

Understanding the relationship between chemical structure and the effectiveness of bioresponsive magnetic resonance imaging contrast agents can offer help to identify key components required for the future development of such probes. Here, we report the development and characteristion of two novel monomeric bifunctional chelators, whose paramagnetic metal complexes can serve as calcium-responsive smart contrast agent (SCA). Specifically, relaxometric titrations, luminescence lifetime measurements, NMR studies and NMR diffusion experiments were carried out to assess the behaviour of each system. Overall, our findings demonstrate the impact of subtle changes to the structure of such probes, affecting a range of properties and their coordination behaviour. Through the understanding of such changes, fine tuning of future SCA designs which show optimal changes in relaxivity can be achieved.