An iminocoumarin based covalent-assembly red-emitting fluorescent probe for detection of β-galactosidase activity in ovarian cancer cells

Upregulation of β-Galactosidase (β-Gal) has been generally found in primary ovarian cancer cells, making the intra-cellular β-Gal as a valuable biomarker for related tumors. In this study, we synthesized an iminocoumarin based covalent-assembly probe, Gal–IC–2, which has been designed to be activated by β-Gal and then rapidly afford to a fluorescent chromophore via a covalent-assembly mechanism with red emission for specific and sensitive detection of β-Gal activity. Gal–IC–2 showed significant fluorescence enhancement and a large Stokes shift in the presence of recombinant β-Gal, and the detection limit of this probe was 1.97 × 10⁻² UmL⁻¹. Notably, Gal–IC–2 also exhibits great stability in a broad pH range and is capable of detecting the reactivity of β-Gal in ovarian cancer cells. This is the first report, to the best of our knowledge, describing a covalent-assembly red-emitting probe for the detection and imaging of β-Gal both in vitro and in ovarian cancer cells.