Dynamic nuclear polarization studies of nitroxyl spin probes in agarose gel using Overhauser‐enhanced magnetic resonance imaging. (4th July 2017) - Meenakumari, V.
Abstract : Agarose is a tissue‐equivalent material and its imaging characteristics similar to those of real tissues. Hence, the dynamic nuclear polarization studies of 3‐carboxy‐2, 2, 5, 5‐tetramethyl‐pyrrolidine‐1‐oxyl (carboxy‐PROXYL) in agarose gel were carried out. The dynamic nuclear polarization parameters such as spin lattice relaxation time, longitudinal relaxivity, leakage factor, saturation parameter and coupling parameter were estimated for 2 mM carboxy‐PROXYL in phosphate‐buffered saline solution and water/agarose mixture (99 : 1). From these results, the spin probe concentration was optimized as 2 mM, and the reduction in enhancement was observed for carboxy‐PROXYL in water/agarose mixture (99 : 1) compared with phosphate‐buffered saline solution. Phantom imaging was also performed with 2 mM concentration of carboxy‐PROXYL in various concentrations of agarose gel at various radio frequency power levels. The results from the dynamic nuclear polarization measurements agree well with the phantom imaging results. These results pave the way for designing model system for human tissues suited to the biological applications of electron spin resonance/Overhauser‐enhanced magnetic resonance imaging. Abstract : Phantom images of 2mM carboxy‐PROXYL in different concentrations of agarose gel obtained by varying RF power. (a) Schematic shows the arrangement of seven phantom tubes. Five tubes contain various concentrations of agarose gel (1.5–4%). PBS represents phosphate‐buffered saline solution without 2mM carboxy‐PROXYL, 0 represents 2mM carboxy‐PROXYL/PBS solution without agarose, and M represents marker, it is a capillary tube that contains 2mM carboxy‐PROXYL/PBS solution without agarose. (b)–(h) Phantom images for various RF power levels.