Visualization of endogenous ß-galactosidase activity in living cells and zebrafish with a turn-on near-infrared fluorescent probe.

ß-Galactosidase (ß-gal) is an important biomarker for primary ovarian cancers. Developing noninvasive bioimaging probes for studying the activity of ß-gal is highly desirable for cancer diagnosis. Herein, a turn-on near-infrared (NIR) fluorescent probe， 2-((6-(((2S, 3R, 4S, 5R, 6R)-3,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran -2-yl)oxy)-2,3-dihydro-1H-xanthen-4-yl)methylene)malononitrile named DXM-ßgal, was rationally designed based on enzymatic reaction for the detection of ß-gal activity both in vitro and in vivo. Upon incubating with ß-gal, DXM-ßgal displayed a significant fluorescence enhancement at 640 nm, accompanying by a color change of solution color from red to purple. DXM-ßgal exhibited high selectivity and sensitively to ß-gal with low limit of detection (2.92 × 10-4 U mL-1). Besides, based on its advantages of long-wavelength emission and excellent biocompatibility, DXM-ßgal was successfully applied to imaging ß-gal in living cells and zebrafish. Given these prominent properties, we believe that DXM-ßgal will be a potential tool for investigating ß-gal activity in biomedical research.