Construction of a multi-signal near-infrared fluorescent probe for sensing of hypochlorite concentration fluctuation in living animals

Hypochlorite (HClO/ClO−) is highly oxidizing and plays important roles in the immune system of living organisms. Up- or down-regulation of HClO/ClO− concentrations may induce many diseases. However, it remains a big challenge to track HClO/ClO− concentration fluctuation in situ because of its low content and high reactivity. Herein, we present the rational design of a powerful ratiometric fluorescent probe (Cy7-Nil) for measuring HClO/ClO− concentrations for the first time. The advantageous features of Cy7-Nil include the composition of two near-infrared chromophores, possessing three emission signals (560 nm, 650 nm and 780 nm), HClO/ClO− concentration dependent fluorescence, and two-photon excitation property. These superior features of Cy7-Nil enable the ratiometric detection of HClO/ClO− concentration range in dual ratiometric channels (I650 / I560 and I650 / I780) and ratiometric detection of endogenous HClO/ClO− concentrations in living animals for the first time. This work provides a universal approach to fabricate novel ratiometric probes for monitoring levels of reactive small molecular species in living animals.