Near-Infrared Aggregation-Induced Emission-Active Probe Enables in situ and Long-Term Tracking of Endogenous β-Galactosidase Activity

Abstract

High-fidelity tracking of specific enzyme activities is critical for the early diagnosis of diseases such as cancers. However, most of the available fluorescent probes are difficult to obtain in situ information because of tending to facile diffusion or inevitably suffering from aggregation-caused quenching (ACQ) effect. In this work, we developed an elaborated near-infrared (NIR) aggregation-induced emission (AIE)-active fluorescent probe, which is composed of a hydrophobic 2-(2-hydroxyphenyl) benzothiazole (HBT) moiety for extending into the NIR wavelength, and a hydrophilic β-galactosidase (β-gal) triggered unit for improving miscibility and guaranteeing its non-emission in aqueous media. This probe is virtually activated by β-gal, and then specific enzymatic turnover would liberate hydrophobic AIE luminogen (AIEgen) QM-HBT-OH. Simultaneously, brightness NIR fluorescent nanoaggregates are in situ generated as a result of the AIE-active process, making on-site the detection of endogenous β-gal activity in living cells. By virtue of the NIR AIE-active performance of enzyme-catalyzed nanoaggregates, QM-HBT-βgal is capable of affording a localizable fluorescence signal and long-term tracking of endogenous β-gal activity. All results demonstrate that the probe QM-HBT-βgal has potential to be a powerful molecular tool to evaluate the biological activity of β-gal, attaining high-fidelity information in preclinical applications.

Enzyme-activatable fluorescent probes for β-galactosidase: from design to biological applications

“…5b ). 64 The results of the Cell experiment revealed that QM-HBT-βgal could realize long-term NIR fluorescence imaging in SKOV-3 cells. Considering the high performance of QM-HBT-βgal and QM-βgal, it was believed that the AIE-active strategy provides a new pathway to design enzyme-activatable probes for on-site sensing and long-term tracking in living samples.…”

Fluorescent small organic probes for biosensing

“…In 2019, Guo et al reported a probe for monitoring β -gal activity, designed around the commonly used AIE quinoline–malononitrile fluorophore. 114 A 2-(2-hydroxyphenyl)benzothiazole moiety was conjugated to both increase lipophilicity and extend the π-system to favour NIR emission. A galactose residue was attached to the probe to act as the recognition moiety, to give the probe QM-HBT-βgal .…”

In Situ Generated Novel 1H MRI Reporter for β-Galactosidase Activity Detection and Visualization in Living Tumor Cells

“…Thus, β-gal activity detection has been exploited with diverse techniques including colorimetric assays (James et al, 2000;Browne et al, 2010;Zeng et al, 2012;Yeung et al, 2013;Chen et al, 2016; Abbreviations: NMR, nuclear magnetic resonance; MRS, magnetic resonance spectroscopy; MRI, magnetic resonance imaging; TR, repetition time; TE, echo time; β-gal, β-galactosidase; FAC, ferric ammonium citrate, TBAB, tetrabutylammonium bromide; CH2Cl2, dichloromethane; HRMS, high-resolution mass spectrometry; PBS, phosphate-buffered saline; X-Gal, 5bromo-4-chloro-3-indolyl-β-D-galactopyranoside; S-Gal, 3,4-cyclohexenoesculetin β-D-galactopyranoside; DMSO, dimethyl sulfoxide; TLC, thin-layer chromatography. 2017), fluorescence (Tung et al, 2004;Urano et al, 2005;Josserand et al, 2007;Kamiya et al, 2007;Feng et al, 2009;Koide et al, 2009;Kamiya et al, 2011;Oushiki et al, 2012;Han et al, 2013;Sakabe et al, 2013;Lee et al, 2014;Asanuma et al, 2015;Peng et al, 2015;Zeng et al, 2015;Doura et al, 2016;Gu et al, 2016;Zhang C. et al, 2016;Zhang X. X. et al, 2016;Jiang et al, 2017;Kim et al, 2017;Nakamura et al, 2017;Wei et al, 2017;Zhang et al, 2017;Tang et al, 2017;Chen et al, 2018;Ito et al, 2018;Liu et al, 2018;Yang et al, 2018;Chen et al, 2019;Fu et al, 2019;Gu et al, 2019;…”