Highly sensitive “off/on” EPR probes to monitor enzymatic activity by OMRI

Abstract

New stable organic radicals probes have been proposed in this study to perform Molecular Imaging by monitoring by Overhauser Magnetic Resonance Imaging (OMRI) the enzymatic activity. The radicals used are Tempo-containing esters forming stable micelles that are practically EPR silent. The hydrolysis of the ester bond catalyzed by Carboxyl esterases generates a narrow and intense EPR signal as a consequence of the release of the nitroxide radical from the micelle. Thus we have prepared a off/on probe responsive to the carboxylesterase activity that can be detected quantitatively in the OMR image.