[1] Measurement of absolute oxygen levels in cells and tissues using oxygen sensors and 2-nitroimidazole EF5

Despite the enormous range and variety of chemical, biochemical, and biological effects of oxygen, accurate control and assessment of the “oxygen concentration” remain extremely difficult experimental tasks in all but the simplest of systems. The difficulty of such control and assessment increases greatly as the oxygen concentration decreases below physiological levels, often the range of greatest biological significance. This chapter discusses possible approaches to these difficult tasks using quantitative measurements of binding of a metabolic marker of hypoxia, the 2-nitroimidazole EF5 [2-(2-nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)acetamide]. The accuracy, dynamic range, and specificity of the pO2 measurement capability of EF5 is discussed in the context of an accurate polarographic pO2 sensor used as a calibration source. Present results suggest that it is indeed possible to assess tissue PO2 at high accuracy and spatial resolution.