Very-low-frequency electron paramagnetic resonance (EPR) imaging of nitroxide-loaded cells.
Recent advances in electron paramagnetic resonance (EPR) imaging have made it possible to image, in real time in vivo, cells that have been labeled with nitroxide spin probes. We previously reported that cells can be loaded to high (millimolar) intracellular concentrations with (2,2,5,5-tetramethylpyrrolidin-1-oxyl-3-ylmethyl)amine-N,N-diacetic acid by incubation with the corresponding acetoxymethyl (AM) ester. Furthermore, the intracellular lifetime (t(1/e)) of this nitroxide is 114 min-sufficiently long to permit in vivo imaging studies. In the present study, at a gradient of approximately 50 mT/m, we acquire and compare EPR images of a three-tube phantom, filled with either a 200-microM solution of the nitroxide, or a suspension of cells preincubated with the nitroxide AM ester. In both cases, 3-mm resolution images can be acquired with excellent signal-to-noise ratios (SNRs). These findings indicate that cells well-loaded with nitroxide are readily imageable by EPR imaging, and that in vivo tracking studies utilizing such cells should be feasible.
Kao
Joseph P Y
JP
Medical Biotechnology Center, University of Maryland Biotechnology Institute, Baltimore, Maryland 21201, USA. jkao@umaryland.edu
Barth
Eugene D
ED
Burks
Scott R
SR
Smithback
Philip
P
Mailer
Colin
C
Ahn
Kang-Hyun
KH
Halpern
Howard J
HJ
Rosen
Gerald M
GM
D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D001330:Electronic Data Processing; D006801:Humans; D019169:Jurkat Cells; D008214:Lymphocytes / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000032:analysis
D003497:Cyclic N-Oxides; D009589:Nitrogen Oxides; C039900:nitroxyl