A Near-Infrared Ratiometric Fluorescent Probe for Highly Selective Recognition and Bioimaging of Cysteine

Abstract

A benzothiazole-based near-infrared (NIR) ratiometric fluorescent probe (HBT-Cys) was developed for discriminating cysteine (Cys) from homocysteine (Hcy) and glutathione (GSH). The probe was designed by masking phenol group in the conjugated benzothiazole derivative with methacrylate group that could be selectively removed by Cys, and therefore an intramolecular charge transfer (ICT) fluorescence was switched on in the NIR region. In the absence of Cys, the probe exhibited a strong blue fluorescence emission at 431 nm, whereas a NIR fluorescence emission at 710 nm was significantly enhanced accompanied by a decrease of emission at 431 nm in the presence of Cys, allowing a ratiometric fluorescence detection of Cys. The fluorescence intensity ratio (I710nm/I431nm) showed a good linear relationship with Cys concentration of 1–40 μM with the detection limit of 0.5 μM. The sensing mechanism was explored based on MS experimental analysis and DFT theoretical calculation. Moreover, the fluorescent probe was successfully used for fluorescence bioimaging of Cys in living cells.

Activity-Based Photosensitizers with Optimized Triplet State Characteristics Toward Cancer Cell Selective and Image Guided Photodynamic Therapy

“…In this direction, we caged the phenolic group, as in the case of DCM-based imaging probes, by utilizing a cysteine (Cys) responsive acrylate moiety as a masking unit and designed the first example of a Cys activatable DCM-based PS (DCM O -I-Cys) (Figure ). Cys serves as an intracellular antioxidant and is known to be overexpressed in most cancer cells (up to 200 μM) to reduce the high oxidative stress. − Therefore, it is accepted as a tumor marker and has been used extensively in activity-based fluorescent sensor designs. , However, Cys-responsive therapeutic agents have remained elusive. Recently, we published a Cys activatable hemicyanine-based PS, which marks the first example of a Cys responsive phototherapy agent .…”

A Förster Resonance Energy Transfer Switchable Fluorescent Probe With H2S-Activated Second Near-Infrared Emission for Bioimaging

“…With the increasing water content, the degree of aggregation of the probe intensifies, accompanying the increase of TPE fluorescence while the occurrence of ACQ for BODIPY chromophore. As is well-known, a ratiometric fluorescence mode has higher accuracy than turn-on or turn-off fluorescence detection mode (Wang et al, 2015; Zhang et al, 2019), we here selected Tris/CH 3 CN buffer solution (0.5 M Tris, 40% CH 3 CN, pH = 7.4) as the next testing condition in order to obtain the ratiometric fluorescent responsiveness. The aggregation of our probe under this buffer solution was proven by dynamic light scattering (Figure S1).…”

A Near-infrared Benzothiazole-based Chemodosimeter for Rapid and Selective Detection of Hydrogen Sulfide

“…On the other side, near-IR (NIR) emitting probes are quite attractive as the NIR signal does not interfere with the biological fluorophores as well as allows deeper tissue penetration (20). Thus, a great deal of effort has been put to develop H2S-selective NIR chemodosimeters, (15,(20)(21)(22)(23), however there are still some challenges need to be addressed in order to improve the impact of NIR probes such as slow response rates, low fluorescence quantum yields and small Stokes shifts. Donor--acceptor (D--A) dyes have attracted great interest as fluorescent probes in recent years since they possess strong NIR emission signals and large Stokes' shifts in aqueous solutions, and they can be easily obtained through a well-established chemistry (24)(25)(26)(27).…”

“…This causes a remarkable red-shift in the absorption signal of the probe and generates a strong NIR emission, which allows both ratiometric and OFF-ON type detection (24). Benzothiazole is among the promising acceptor units, which have been used successfully in the design of D--A type chemodosimeters for imaging of several analytes (23,28,29). In this study, a H2S selective benzothiazole-based chemodosimeter (HP-1) (Figure 1) was developed as a (D--A) type probe and its H2S detection capabilities were evaluated in detail by UV-Vis and fluorescence spectroscopies in aqueous solutions.…”