(2)H,(15)N-substituted nitroxides as sensitive probes for electron paramagnetic resonance imaging.

Area of Science:

• Biomedical Imaging
• Biophysics
• Medical Physics

Background:

• Electron paramagnetic resonance imaging (EPRI) with nitroxides is an emerging technique for in vivo physiological studies.
• EPRI can map oxygen (O2) distribution in tumors and brain regions, aiding research in hypoxia and drug abuse.
• Previous work demonstrated entrapping a nitroxide anion in brain tissue for in vivo O2 quantitation.

Purpose of the Study:

• To synthesize a novel, fully isotopically substituted nitroxide to improve the sensitivity of EPRI.
• To enhance the signal-to-noise ratio for more accurate in vivo O2 measurements.
• To enable more precise O2 quantitation in various tissues using EPRI.

Main Methods:

• Synthesis of a fully isotopically substituted nitroxide: 3-carboxy-2,2,5,5-tetra((2)H(3))methyl-1-(3,4,4-(2)H(3),1-(15)N)pyrrolidinyloxyl.
• Electron paramagnetic resonance (EPR) spectroscopy for characterization.
• Evaluation of signal-to-noise ratio and sensitivity to O2 concentration.

Main Results:

• The synthesized isotopically substituted nitroxide significantly improved the signal-to-noise ratio in EPR imaging.
• This enhancement directly translates to increased sensitivity for EPRI.
• The new nitroxide demonstrated heightened sensitivity to changes in O2 concentration.

Conclusions:

• A novel, fully isotopically substituted nitroxide was successfully synthesized, enhancing EPRI sensitivity.
• This improved sensitivity allows for more accurate in vivo O2 measurements in biological tissues.
• The findings pave the way for more precise O2 mapping in conditions like tumors and hypoxic brain regions.