An edoplasmic reticulum-targeted NIR fluorescent probe with a large Stokes shift for hypoxia imaging

[Display omitted] •ISO-NTR is the first endoplasmic reticulum-targeted fluorescent probe with long-wavelength emission and large Stokes shift (185 nm) for hypoxia imaging.•The probe shows high sensitivity and selectivity towards nitroreductase.•The probe ISO-NTR could monitor the degree of hypoxia in the living system. Hypoxia is closely linked to various diseases, including solid tumors. The level of nitroreductase (NTR) is usually abnormally upregulated in hypoxic conditions, which can be a biomarker of hypoxia. Herein, the first endoplasmic reticulum-targeting NIR fluorescent probe, ISO-NTR, was developed for highly selective and sensitive detection of NTR. It shows a large Stokes shift (185 nm) and a 5-fold increases in fluorescence intensity. Meanwhile, the ISO-NTR probe with a dicyanoisophorone derivative has excellent endoplasmic reticulum targeting in living systems with high Pearson’s correlation coefficients (Rr = 0.9489). Molecular docking calculations and high binding energy between the probe and NTR (−10.78 kcal·mol−1) may explain the high selectivity of ISO-NTR. Additionally, it has been successfully applied to NTR imaging in vitro and vivo due to its good sensitivity, high selectivity and large Stokes shift, which may provide an effective method for studying the physiological and pathological functions of NTR in living systems. This probe could be developed as a potential imaging tool to further explore the pathogenesis of hypoxia-related diseases in endoplasmic reticulum stress.