Identification of Hypoxic Cells Using an Organotellurium Tag Compatible with Mass Cytometry

Mass cytometry (MC) offers unparalleled potential for the development of highly parameterized assays for characterization of single cells within heterogeneous populations. Current reagents compatible with MC analysis employ antibody‐metal‐chelating polymer conjugates to report on the presence of biomarkers. Here, we expand the utility of MC by developing the first activity‐based probe designed specifically for use with the technology. A compact MC‐detectable telluroether is linked to a bioreductively sensitive 2‐nitroimidazole scaffold, thereby generating a probe sensitive to cellular hypoxia. The probe exhibits low toxicity and is able to selectively label O2‐deprived cells. A proof‐of‐concept experiment employing metal‐bound DNA intercalators demonstrates that a heterogeneous mixture of cells with differential exposure to O2 can be effectively discriminated by the quantity of tellurium‐labeling. The organotellurium reagents described herein provide a general approach to the development of a large toolkit of MC‐compatible probes for activity‐based profiling of single cells. Tellurium tattletale: The identification of a compact telluroether scaffold has allowed the development of a new class of mass‐cytometry‐compatible reagents that do not rely on bulky metal‐chelating polymers for detection. Using cellular hypoxia as a proof‐of‐concept target, this study demonstrates that the first‐generation tellurium‐bearing probe is synthetically accessible, stable under biological assay conditions, and exhibits low toxicity.