Paramagnetic transition metal ion complexes with multiple oxidation states are of interest as MRI probes for registration of reactive oxygen species (ROS) as important biomarkers for inflammation, a characteristic of many diseases including atherosclerosis and cancer. Probes that are responsive to inflammation would be an important addition to diagnostic imaging procedures. Research in our laboratory is exploring two types of MRI probes including Co(II) complexes that produce highly shifted intraliposomal water protons for liposome based CEST (lipoCEST) agents. Neutral macrocyclic Co(II) complexes with anionic pendant amide groups are effectively loaded into liposomes or bilayer at high millimolar concentrations to produce lipoCEST agents. Oxidation of high spin Co(II) complexes modulates the CEST effect as detected by the magnetic asymmetry of the liposomal z-spectrum. An alternative for monitoring redox processes is based on Fe(II) complexes that are oxidized to high spin Fe(III) complexes for enhanced water proton T<sub>1</sub> relaxation. Incorporation of Fe(II) or Fe(III) complexes into liposomes produces lipoCEST and T<sub>1</sub> agents for imaging ROS. MRI studies of the liposomal agents injected in mice will be presented.

Redox-responsive MRI contrast agents based on cobalt and iron complexes

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.