NIR-H2O2 is a cell-permeable near-infrared (NIR) fluorescent turn-on sensor. It responds to H2O2 with a large turn-on NIR fluorescence signal upon excitation in the NIR region.

NIR-H2O2 is highly selective to H2O2 over other typical ROS and bio relevant species. HeLa cells incubated with NIR-H2O2 (5 μM) for 30 min at 37 °C provide almost no fluorescence. However, when the living HeLa cells loaded with NIR-H2O2 are further treated with H2O2, they give strong fluorescence. When stimulated by phorbol myristate acetate (PMA), macrophage cells may produce endogenous H2O2. The living RAW264.7 macrophage cells loaded with only the NIR sensor NIR-H2O2 (1 μM) display almost no fluorescence. However, the macrophage cells coincubated with PMA (3.0 μg/mL), and the sensor NIR-H2O2 (1 μM) exhibit a dramatic enhancement in the red emission. NIR-H2O2 is capable of fluorescent imaging of endogenously produced H2O2 in the living RAW264.7 macrophage cells.

In a lipopolysaccharide (LPS) model of acute inflammation, the H2O2 production in vivo was generated by activated macrophages and neutrophils. The mice treated with both LPS and NIR-H2O2 exhibit a significantly higher fluorescence readout than the mice untreated or treated with only NIR-H2O2. The mice loaded with LPS and NIR-H2O2 have approximately 10- and 20-fold higher fluorescence intensity than the mice loaded with saline and the sensor and the mice loaded with saline, respectively.