Chapter 4: Spin Probes and Imaging Using Nitroxides

Nitroxyl radicals, NRs, represent the most diverse class of stable organic radicals varying in stability, spectral properties and functionality which have been successfully used as spin labels and probes in numerous electron paramagnetic resonance (EPR)-based spectroscopic and imaging applications. The stability of N–O group of the NRs allows chemical reactions which do not destroy the radical center and, therefore, opens the opportunity to design NR probes for sensing specific chemical reagents such as oxygen, protons (pH), glutathione, nitric oxide and specific enzymatic activities. In this chapter we overview the principles of NR applications as probes to assess the local chemical microenvironment with a focus on their in vivo functional imaging.