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

Wei Fu,Yiyu Ma,Zhiqian Guo,Yutao Zhang,Chenxu Yan,Wei-Hong Zhu

doi:10.3389/fchem.2019.00291

Wei Fu, Yiyu Ma + Show 4 more

Open Access

https://doi.org/10.3389/fchem.2019.00291

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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.

Highlights

Specific enzymes play vital roles in a wide range of biological processes
QM is employed as the aggregation-induced emission (AIE) building block along with generating modifiable sites for functionalization, which could perform controllable NIR emission via tuning electron–donor ability (Shi et al, 2013; Shao et al, 2014, 2015; Wang M. et al, 2018)
After being hydrolyzed by β-gal, hydrophobic QM-HBT-OH can be released and aggregated with a remarkable light-up AIE-active fluorescent signal, which could be well retained in the reaction site and emit strong fluorescence for long-term tracking endogenous β-gal activity

Summary

Introduction

Specific enzymes play vital roles in a wide range of biological processes. Among them, β-galactosidase (β-gal) is overexpressed in primary ovarian cancers, which has been regarded as an important biomarker for cell senescence and ovarian cancer diagnosis (Dimri et al, 1995; Spergel et al, 2001). By virtue of the NIR AIEactive performance of enzyme-catalyzed nanoaggregates, QMHBT-βgal is capable of affording a localizable fluorescence signal and long-term tracking of endogenous β-gal activity. It could be interpreted that the QM-HBT-βgal can be hydrolyzed by β-gal and spontaneously form nanoaggregates QMHBT-OH with a remarkable AIE-active fluorescent signal, which is confirmed by Figures S2, S3, and we observe in situ generation of about 200-nm nanoaggregates by DLS and SEM characterization.

Results

Conclusion