An Activatable Manganese-Based MR Contrast Agent for the Imaging of Redox Environment

Shreya Mukherjee¹, Galen S. Loving¹, Peter Caravan²

Redox reactions are ubiquitous in biochemical activities. However, the lack of suitable redox responsive probes has hindered the non-invasive observation of intracellular redox activities through molecular imaging. We hypothesized that a redox-activated MR probe based on Mn2+/Mn3+ couple would be stable with respect to metal dissociation in both oxidation states, sensitive to biological reductants, and sufficiently reactive to act as an in vivo sensor. Here we report the design and characterization of a potential redox probe. The feasibility of this probe to act as redox responsive MR agents was tested under physiologically relevant reducing conditions. We anticipate that the probe activation would be limited primarily to regions where the normal mechanisms that regulate extracellular redox have been severely impaired.