DYNAMIC ELECTRON-SPIN-RESONANCE (ESR) IMAGING OF THE DISTRIBUTION OF SPIN-LABELED DEXTRAN IN A MOUSE

The nitroxide group 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was c ovalently bound to a dextran via an N-acetamido linkage to produce a n ovel spin probe, TEMPO-dextran (TEMPO-DX), which circulates for long t ime periods in an animal without metabolic degradation, TEMPO-DX was s table in mice, while small TEMPO analogs quickly disappeared after adm inistration, Since dextran was reduced somewhat in size during synthes is, the resultant spin-labeled dextran could be excreted through the k idney, A strong L-band electron spin resonance signal was obtained sho rtly after intravenous administration of TEMPO-DX into the tail vein o f a mouse, from which three-dimensional images of specific organs were calculated, The signal was found to persist for well over 1 h.