Detecting Cysteine in Bioimaging with a Near‐Infrared Probe Based on a Novel Fluorescence Quenching Mechanism

Abstract

Near-infrared (NIR) fluorescent probes are very significant for detecting cysteine in biological systems. Herein, we report a highly selective and sensitive NIR turn-on fluorescent probe (BDP-NIR) based on BODIPY with large Stokes shift (105 nm) for detecting Cys. We clarified the sensing mechanism based on the different thiol-induced S N Ar substitution/rearrangement reaction of the probe with cysteine and homocysteine/ glutathione, which leads to the corresponding amino-and thiol-BODIPY dyes with distinct photophysical properties. Moreover , a novel mechanism of fluorescence quenching was demonstrated by density functional theory calculation. The reason for the fluorescence quenching of the probe might be intersystem crossing (from singlet to triplet excited state). Moreover, BDP-NIR had a high linear dynamic range of 0-500 μM, which was promising for detecting cysteine quantificationally. Significantly, BDP-NIR was capable of sensing endogenous cysteine in living cells and in vivo.

Sensing Mechanism of Cysteine Specific Fluorescence Probes and Their Application of Cysteine Recognition

“…The suggested sensing system for Cys has been demonstrated in a prior article. , According to refs and , GSH has a flexible, longer backbone, two amide units, and more steric hindrance than Hcy/Cys. As a result of the lower p K a value of thiol functionality, Cys, which was one carbon shorter than Hcy, and displayed a greater nucleophilicity than Hcy. , In the instance of Cys, thioether BDP-S-S-Cys intermediates are formed when the p -methoxyphenthiol group of BDP-S had initially been changed by the thiol of cysteine and produced amino-BODIPY (BDP-S-N-Cys) thermodynamically have been more stable through intramolecular transformation rearrangement.…”

Direct Quantification and Visualization of Homocysteine, Cysteine, and Glutathione in Alzheimer’s and Parkinson’s Disease Model Tissues

“…Common methods of quantification of plasma total Hcy and Cys (tHcy and tCys) include high-performance liquid chromatography (HPLC)-based detection methods − and some fully automated immunological methods, such as the fluorescence polarization immunoassay (FPIA), enzyme immunoassay (EIA), and enzymatic cycling assay (ECA). − Tedious sample pretreatment, expensive enzymatic or immunogenic materials, and complex instrumentations are usually required in these approaches. Because of features such as noninvasiveness, high selectivity, high sensitivity, relatively low cost, and operational simplicity, fluorescent probes for monitoring biothiols have attracted great focus and interest recently. − Several fluorescent probes for quantifying Hcy or Cys in human serum have been reported. − However, there are still very few probes that can directly and simultaneously quantify serum tHcy and tCys. It is greatly challenging to simultaneously quantify Cys and Hcy in real samples and visualize their dynamics in the brain tissues with fluorescent probes due to their similar properties and different concentrations.…”

A molecular design towards sulfonyl aza-BODIPY based NIR fluorescent and colorimetric probe for selective cysteine detection

“…Accordingly, uorescent probes for Cys, Hcy and GSH have been utilized in molecular recognition or thiol-specic reaction strategies. [5][6][7][8][9] However, because of the structural similarity of Cys and Hcy, the selective discrimination between the two species is a challenging task. On the other hand, many sulfonyl groupsbased probes have been reported with a lack of study compared their substitution ability with biothiols.…”