Reactive
oxygen species (ROS) play an important role in cell metabolism,
but they can cause oxidative damage to biomolecules. Among ROS, the
hydroxyl radical (·OH) is one of the most reactive molecules
in biological systems because of its high reaction rate constant.
Therefore, imaging of ·OH could be useful for evaluation of the
redox mechanism and diagnosis of oxidative diseases. In vivo dynamic
nuclear polarization-magnetic resonance imaging (DNP-MRI) is a noninvasive
imaging method to obtain spatiotemporal information about free radicals
with MRI anatomical resolution. In this study, we investigated the
visualization of hydroxyl radicals generated from the Fenton reaction
by combining DNP-MRI with a spin-trapping agent (DMPO: 5,5-dimethyl-1-pyrroline N-oxide) for ·OH. Additionally, we demonstrated the
radical-scavenging effect using four thiol-related reagents by DNP-MRI.
We demonstrated that DNP enhancement could be induced by the DMPO-OH
radical using the DNP-MRI/spin-trapping method and visualized ·OH
generation for the first time. Maximum DNP enhancement was observed
at an electron paramagnetic resonance irradiation frequency of 474.5
MHz. Furthermore, the radical-scavenging effect was simultaneously
evaluated by the decrease in the DNP image value of DMPO-OH. An advantage
of our methods is that they simultaneously investigate compound activity
and the radical-scavenging effect.
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