Near-infrared fluorescent probe with a large Stokes shift for bioimaging of β-galactosidase in living cells and zebrafish develop at different period

Overexpression of β-galactosidase (β-gal) in tumor cells may serve as a valuable biomarker for the early diagnosis of some cancers (such as ovarian cancer). In addition, abnormal accumulation of β-gal is also considered an essential marker of cell senescence. Therefore, it is important to construct fluorescent probes with excellent fluorescence properties to visualize β-gal in biological systems. Here, we designed and screened a novel fluorescent probe XM for the detection of β-gal. Spectral data show that the probe has a good affinity (Km = 2.6 μM) for β-gal, large stokes shift (190 nm), fast response speed (stable within 20 min), and low detection limit (6.7 × 10-3 U/mL). Based on the above advantages, XM can not only detect β-gal content in cancer cells but also track the changes of β-gal content in zebrafish at different developmental period. We believe XM will become a powerful tool for the early cancer diagnosis and cellular senescence.