Natural hyperoside based novel light-up fluorescent probe with AIE and ESIPT characteristics for on-site and long-term imaging of β-galactosidase in living cells†

Fluorescence-based on-site and long-term sensing and bioimaging of biomarkers are highly desired for effective diagnosis. Aggregation-induced emission luminogens (AIEgens) with excited-state intramolecular proton transfer (ESIPT) characteristics have outstanding advantages in biological applications for their large Stokes shift, and low background signal in aggregated state. However, most reported AIEgens are fabricated through rational design and complex synthesis procedures. Importantly, with rich structural skeletons and easy access, natural products have superiority in developing promising AIEgens with ESIPT. Here, hyperoside (quercetin-3-O-β-galactoside) has been easily obtained from Hedyotis diffusa. After incubation hyperoside with β-galactosidase (β-Gal), the hydrolysis product, hydrophobic quercetin, is in situ aggregated, which presents AIE and ESIPT characteristics with large Stokes shift (170 nm). Then, a novel light-up fluorescent probe has been fabricated for detection of β-Gal with a good linear relationship (0.03–12 U mL-1), high sensitivity (detection limit of 0.013 U mL-1) and superior selectivity. Meanwhile, excellent biocompatibility, low cytotoxicity, outstanding photostability, and good intracellular retention demonstrate the superiorities for on-site and long-term (about 8 h) imaging of β-Gal in SKOV-3 cells. Results demonstrate the application of hyperoside in sensing and imaging of β-Gal in biological samples, and propose the great possibility of natural products for finding of novel AIE-based fluorescence probes.