IN-VIVO AND IN-VITRO EPR OXIMETRY WITH FUSINITE - A NEW COAL-DERIVED,PARTICULATE EPR PROBE

The peak-to-peak line width (LW) of the first derivative electron spin resonance (EPR) spectrum of the coal maceral fusinite is reversibly b roadened by O-2. The extent of broadening per unit of partial pressure of oxygen (pO(2)) is unusually large, exceeding that of nitroxides by almost two orders of magnitude. This paramagnetic property of fusinit e, combined with its very stable physicochemical properties and low to xicity, is shown to be of utility in the measurement of pO(2) in vitro and in vivo. Fusinite particles are endocytosed by chinese hamster ov ary (CHO) cells in vitro; this is useful for intracellular O-2 measure ments with commercially available EPR spectrometers operating at 9.1-9 .3 GHz. For measurement of oxygen in vivo using low frequency EPR (1.1 -1.3 GHz), fusinite provides a sensitive and persistent means to measu re pO(2) in tissues. Particles implanted into the gastrocnemius muscle of A/J mice remained interstitially in the same position for months w ith undiminished sensitivity to pO(2) and no specific toxic effects.