A 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 due to their large Stokes shift and low background signal in the aggregate state. However, most of the reported AIEgens are fabricated through rational design and complex synthesis procedures. Importantly, with rich structural skeletons and ease of access, natural products have superiority in developing promising AIEgens with ESIPT. Here, hyperoside(quercetin-3-O-β-galactoside) has been easily obtained fromHedyotis diffusa. After the incubation of hyperoside with β-galactosidase (β-Gal), the hydrolysis product, hydrophobic quercetin, is aggregatedin situ, which presents AIE and ESIPT characteristics with a large Stokes shift (170 nm). Then, a novel light-up fluorescent probe has been fabricated for the detection of β-Gal with a good linear relationship (0.03-12 U mL), high sensitivity (a detection limit of 0.013 U mL) and superior selectivity. Meanwhile, excellent biocompatibility, low cytotoxicity, outstanding photostability, and good intracellular retention demonstrate its superiority for on-site and long-term (about 8 h) imaging of β-Gal in SKOV-3 cells. The results demonstrate the application of hyperoside in the sensing and imaging of β-Gal in biological samples, and propose the great possibility of natural products for developing novel AIE-based fluorescence probes.