pH-sensitive imaging by low-frequency EPR: a model study for biological applications.
The use of pH-sensitive nitroxides, in conjunction with low-frequency EPR, offers a unique opportunity for non-invasive assessment of pH values (in the range 0 to 14) in living animals. In the present study, we have investigated the potential use of pH-sensitive nitroxide free radicals in conjunction with EPR imaging techniques at low and very low frequencies (280 MHz-2.1 GHz). In particular, we have measured the hyperfine splitting (hfs) of a pH-sensitive probe at three different EPR frequencies: 280 MHz, 1.1 GHz and 2.1 GHz. We have also developed EPR imaging experiments with phantoms simulating in vivo conditions, using pH-sensitive probes at 280 MHz (spatial-spatial) and 1.1 GHz (spectral-spatial). Finally, we discuss the actual sensitivity/resolution limits of the EPR imaging techniques at low frequencies. Practical applications of this method in the biomedical field are suggested for the continuous and non-invasive localization of pH in vivo.
Dipartimento di Scienze e Tecnologie Biomediche, Universita' dell'Aquila, Italy. sotgiu@fismed.univaq.it
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Sotgiu
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Mäder
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Placidi
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Colacicchi
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Ursini
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Alecci
D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005609:Free Radicals / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D009589:Nitrogen Oxides / Q000378:metabolism; D019047:Phantoms, Imaging; D011846:Radio Waves; D051381:Rats; D013113:Spin Labels
D005609:Free Radicals; D009589:Nitrogen Oxides; D013113:Spin Labels