Development of a near-infrared fluorescent probe for the selective detection of severe hypoxia

Severely hypoxic environments with oxygen concentrations around 1% are often found in serious diseases such as ischemia and cancer. However, existing near-infrared (NIR) fluorescent probes that can visualize hypoxia are also activated in mildly hypoxic environments (around 5% oxygen). Here, in order to selectively detect severe hypoxia, we used julolidine-based SiR (JSiR) as a NIR fluorophore and developed T-azoJSiR640 as a fluorescent probe. T-azoJSiR640 was able to detect severe hypoxia (around 1% oxygen concentration or less) in live cell imaging. Furthermore, the ischemic liver in a portal-vein-ligated mouse model was successfully visualized in vivo.