In this work, we report on the development of nitroxide and trityl radicals to measure enzyme activity directly in vivo using EPR imaging. This new concept is based on a modification of the EPR spectra of a spin probe substrate of a particular enzyme upon enzymatic transformation. The shift in EPR resonance between the enzyme substrate and product can be used to image both substrate and enzyme independently using 4D spectral-spatial EPR imaging. Our first example depicts a nitroxide-based radical whose spectrum is sensitive to alkaline phosphatase (ALP). This radical was used to image ALP activity in vitro using a homemade rapid-scan EPR imager operating at 800 MHz. However, the in vivo use of nitroxide radicals are limited by their fast bioreduction. Therefore, we are developing the first trityl radicals sensitive to enzyme activity. Indeed, trityl radicals are well known for their extraordinary stability in biological media, the narrow linewidth of trityl radicals also increases the sensitivity of detection and the spectral resolution between substrate and product. We report on the synthesis and characterization of an ALP sensitive trityl spin probe.

Development of enzyme responsive spin probes for non-invasive imaging of enzyme activity by EPR

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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