Ratiometric fluorescent probes with a self-immolative spacer for real-time detection of β-galactosidase and imaging in living cells

Ratiometric fluorescent probes with a self-immolative spacer for beta-galactosidase (beta-gal) were developed. They function by beta-gal-cleaving the beta-galactoside bond of fluorescent substrates, followed by self-immolation to liberate the amino group of fluorophore. Thus, a remarkable variation in the photo-physical properties was observed and the corresponding ratiometric detection of beta-gal was realized. Our studies demonstrated that the GNPN exhibited high sensitivity for recognition of beta-gal, with a detection limit as low as 0.17 U L-1. GNPN can rapidly quantify beta-gal enzyme activity; the emission ratio F-545/F-475 for the GNPN reached maxima after approximately 4 min, which was one of the shortest response time ever reported. Furthermore, we demonstrated that these probes possess excellent biocompatibility and can be used to visualize the endogenous beta-gal in ovarian cancer cells. (C) 2018 Elsevier B.V. All rights reserved.