The concentration of naturally occurring free radicals generated in the human body by tissues or cells changes in some diseases. Detection of these free radicals is helpful for diagnosis and treatment of patient. Electron Spin Resonance (ESR) and Proton Electron Double Resonance Imaging (PEDRI) are established methods for detecting free radicals. In this project a X-band ESR spectrometer and a 59 mT PEDRI system were used for detecting free radicals. Experiments were carried out to compare the two systems ability to detect free radicals at different concentrations Proton-electron double-resonance imaging (PEDRI) is a method for detecting and imaging free radicals in biological samples or animals. PEDRI uses the Overhauser effect, and involves collecting a proton NMR image while irradiating the EPR of the free radical under study. The ESR Bruker system used microwave frequencies to irradiate the sample, while the PEDRI system used frequencies below 300MHz. The ESR irradiation frequency is 660 times the NMR frequency. Using the PEDRI technique the ESR frequency for irradiating the samples was used below 300MHz compared to 9.8GHz used in the ESR Bruker system. A non-imaging variant of PEDRI, field-cycled dynamic nuclear polarization (FC-DNP) spectroscopy allows Overhauser-detected ESR spectra to be obtained via NMR detection. In Field-cycled PEDRI (FC-PEDRI) techniques the magnetic field is switched between two levels during the pulse sequence in order to decrease non-resonant RF power deposition and to increase sensitivity. A spectroscopic version of FC-PEDRI, called field-cycled dynamic nuclear polarisation (FC-DNP) is used to obtain ESR spectra via Overhauser effect. iii This project was an attempt to investigate the sensitivity of both the Bruker ESR system and the PEDRI system. The sensitivity of each system was evaluated based on the ability to detect the minimum free radical concentration. From the experiments performed in the project, the PEDRI system was able to detect 20µM Tempol in solution, where as the Bruker ESR system was able to detect 0.01 µM Tempol in solution. The magnetic field of 59 mT was used in PEDRI system and 0.35 T in the ESR Bruker system.

TITLE - COMPARISON OF SENSITIVITY OF PEDRI AND ESR FOR DETECTION OF FREE RADICALS
AUTHOR - Mr. Sunil Kalagi
••••••IJSER Edition - March 2018

UNIVERSITY - University of Aberdeen
GUIDE NAME -
Dr. David Lurie