In vivo free radical imaging in pre-clinical models of disease is now possible. Free radicals have traditionally been characterized by ESR or EPR spin trapping spectroscopy. The disadvantage of the ESR/EPR approach is that spin adducts are short-lived due to biological reductive and/or oxidative processes. Immuno-spin trapping (IST) involves the use of an antibody that recognizes macromolecular DMPO-spin adducts (anti-DMPO antibody), regardless of the oxidative/reductive state of trapped radical adducts. The IST approach has been extended to an in vivo application that combines IST with molecular magnetic resonance imaging (mMRI). This combined IST-mMRI approach involves the use of a spin trapping agent, DMPO, to trap free radicals in disease models, and administration of a mMRI probe, an anti-DMPO probe, that combines an antibody against DMPO-radical adducts and a MRI contrast agent, resulting in targeted free radical adduct detection. The combined IST-mMRI approach has been used in several rodent disease models, including diabetes, ALS, gliomas, and septic encephalopathy. The advantage of this approach is that heterogeneous levels of trapped free radicals can be detected directly in vivo and in situ to pin-point where free radicals are formed in different tissues. The approach can also be used to assess therapeutic agents that are either free radical scavengers or generate free radicals. The focus of this review will be on the different applications that have been studied, advantages and limitations, and future directions.
Part of the book: Free Radicals, Antioxidants and Diseases