A fluorescence signal amplification and specific energy transfer strategy for sensitive detection of β-galactosidase based on the effects of AIE and host-guest recognition

Benefit from the efficient energy transfer, aggregation-induced emission (AIE) and host-guest recognition as strategies of signal amplification and specific binding have been applied to establish the sensing system; however, the application of these two attractive strategies in one system is rare. Herein, we propose a turn-on to turn-off' fluorescent strategy for sensitive detection of beta-galactosidase (beta-Gal) based on the application of AIE and host-guest recognition. In this work, a novel red-emitted (635 nm) copper nanoclusters (CuNCs) protected by dithioerythritol (DTE) and beta-cyclodextrin (beta-CD) has been found to possess AIE property induced by aluminum cations to achieve the turn-on process, and the coordinated behavior between aluminum cations and DTE/beta-CD CuNCs is also discussed. As the hydrolysis product of beta-Gal and 4-nitrophenyl-D-galactopyranoside, p-nitrophenol can combine with beta-CD in DTE/beta-CD CuNCs by the host-guest recognition to realize the efficient photoelectron transfer to turn-off' the fluorescence. This strategy performs the exciting linear range of 0.0-50.0 U/L and detection limit of 0.56 U/L (S/N = 3) for sensitive detection of beta-Gal and further applies in biologic samples successfully. As far as we know, this is the first work to combine AIE and host-guest recognition in one system to construct the sensing platform, which can achieve efficient and specific energy transfer to improve the sensitivity of the system.