Trityl Radicals as Persistent Dual Function pH and Oxygen Probes for in Vivo Electron Paramagnetic Resonance Spectroscopy and Imaging:  Concept and Experiment

2007 ◽  
Vol 129 (23) ◽  
pp. 7240-7241 ◽  
Author(s):  
Andrey A. Bobko ◽  
Ilirian Dhimitruka ◽  
Jay L. Zweier ◽  
Valery V. Khramtsov
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Dual Function ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Oxygen Probes ◽  
Electron Paramagnetic

The Measurement of Temperature With Electron Paramagnetic Resonance Spectroscopy

1996 ◽  
Vol 118 (2) ◽  
pp. 193-200 ◽  
Author(s):  
J. J. Eckburg ◽  
J. C. Chato ◽  
K. J. Liu ◽  
M. W. Grinstaff ◽  
H. M. Swartz ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Fatty Acid ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
In Vivo Studies ◽  
Acid Mixture ◽  
Resonance Spectroscopy ◽  
Temperature Sensitive ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

An electron paramagnetic resonance (EPR) technique, potentially suitable for in vivo temperature measurements, has been developed based on the temperature response of nitroxide stable free radicals. The response has been substantially enhanced by encapsulating the nitroxide in a medium of a fatty acid mixture inside a proteinaceous microsphere. The mixture underwent a phase transition in the temperature range required by the application. The phase change dramatically altered the shape of the EPR spectrum, providing a highly temperature sensitive signal. Using the nitroxide dissolved in a cholesterol and a long-chain fatty acid ester, we developed a mixture which provides a peakheight ratio change from 3.32 to 2.11, with a standard deviation of 0.04, for a temperature change typical in biological and medical applications, from 38 to 48°C. This translated to an average temperature resolution of 0.2°C for our experimental system. The average diameter of the nitroxide mixture-filled microspheres was ≈2 μm. Therefore, they are compatible with in vivo studies where the microspheres could be injected into the microvasculature having a minimum vessel diameter of the order of 8 μm. This temperature measuring method has various potential clinical applications, especially in monitoring and optimizing the treatment of cancer with hyperthermia. However, several problems regarding temperature and spatial resolution need to be resolved before this technique can be successfully used to monitor temperatures in vivo.

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