Rational Construction of a Two-Photon NIR Ratiometric Fluorescent Probe for the Detection of Bisulfite in Live Cells, Tissues, and Foods

Fluorescence based metabisulfite sensing: New aspects of ion sensing by a styryl benzothiazolium dye and understanding nitrite interference

Detection of specific ions using fluorescent probes has relevance in several areas of therapeutics development and environmental science. Here, we provide new perspectives to the sensing of a styryl benzothiazolium-based fluorescent compound 1 and report that sensing properties are for sulfite ions in general with highest preference for metabisulfite ions (S2O52-) adding to its previously determined role as a bisulfite ion sensor. This probe exhibits its sensing action via an addition reaction in which the styryl double bond gets reduced. The interference studies highlighted that the sequence of addition of nitrite and metabisulfite has a bearing on the overall interference outcome. Spectroscopic studies revealed that the order of preferential sensing of sulfites and sulfide ion is S2O52- > HSO3- > SO32- > S2-. Although this probe displays robust sensing on its own through fluorescence quenching, its fluorescence emission can be enhanced at much lower concentrations in the presence of a G-quadruplex DNA without compromising the outcome of the sensing.

Dual-responsive fluorescence probe for measuring HSO3- and viscosity and its application in living cells and real foods

Microenvironmental indicators in organisms drive the operation of different physiological functions. In contrast, disruption of microenvironmental homeostasis is often closely associated with various pathological processes. A novel dual-response fluorescent probe based on hemicyanine dye (HT-Bzh) was designed and synthesized for the detection of HSO3- and viscosity changes. The probe not only provides high sensitivity (limit of detection = 0.2526 μM) for the detection of HSO3- using the Michael addition reaction, but also allows the observation of fluorescence emission at 528 nm and thus the monitoring of viscosity changes through hindering of the twisted intramolecular charge transfer (TICT) mechanism. Additionally, dual-response probe has been successfully used to image living cells and detect real food samples. As a new designed tool, HT-Bzh shows excellent anti-interference capability and biocompatibility, which makes it have application potential in other biological systems and in-vivo imaging.

Bifunctional near-infrared fluorescent probe for the selective detection of bisulfite and hypochlorous acid in food, water samples and in vivo

We report the development of a bifunctional near-infrared fluorescent probe (QZB) for selective sensing of bisulfite (HSO3-) and hypochlorous acid (HOCl). The synergistic detection of HSO3- and HOCl was achieved via a C=C bond recognition site. In comparison with the red-fluorescence QZB, two different products with non-fluorescence and paleturquoise fluorescence were produced by the recognition of QZB towards HSO3- and HOCl respectively, which can realize effectively the dual-functional detection of HSO3- and HOCl. QZB features prominent preponderances of dual-function response, near-infrared emission, reliability at physiological pH, low cytotoxicity and high sensitivity to HSO3- and HOCl. The detection of HSO3- in actual food samples has been successfully achieved using QZB. Utilization of QZB-based test strip to semi-quantitatively detect HSO3- and HOCl in real-world water samples by the "naked-eye" colorimetry are then demonstrated. Simultaneously, the determination of HSO3- and HOCl in real-world water sample has been achieved by smartphone-based standard curves. Additionally, the applications of QZB for imaging HSO3- and HOCl in vivo are successfully demonstrated. Consequently, the successful development of QZB could be promising as an efficient tool for researching the role of HSO3-/HOCl in the regulation of redox homeostasis regulation in vivo and complex signal transduction and for future food safety evaluation.

Development of a Ratiometric Fluorescent Probe with Zero Cross-Talk for the Detection of SO2 Derivatives in Foods and Live Cells

Sulfur dioxide (SO2) derivatives are extensively utilized as both a preservative for foods and an active gaseous signal molecule in various physiological and pathological processes, but their excessive intake would bring harmful effects on human health; so, the determination of SO2 derivatives is of great importance. Herein, we developed a ratiometric fluorescent probe named 2-(2'-hydroxyphenyl)benzothiazole-3-ethyl-1,1,2-trimethyl-1H-benzo[e]indolium (HBT-EMBI) by introducing a hemicyanine unit of EMBI to an HBT group for the detection of SO2 derivatives via an excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) effects. The probe displays some advantages, such as a colorimetric change from purple to colorless, a ratiometric fluorescence with zero cross-talk, and a remarkably large emission shift (Δλ = 164 nm) under a single-wavelength excitation. Accordingly, the probe HBT-EMBI has been successfully employed for the colorimetric and ratiometric determination of SO2 derivatives in real food samples and the quantitative visualization of SO2 derivative variations in HepG2 cells.

"One stone, two birds": a mitochondria-targeted fluorescent probe for the detection of viscosity and HSO3- in living cells

The material transport and physiological events of mitochondria need to be supported by a suitable microenvironment. For example, high viscosity will seriously hinder material exchange, and SO2, as the precursor of HSO3-, is an endogenous signal molecule that plays a key role in information transmission. It is very important to detect viscosity and HSO3- in mitochondria. Here, we developed a dual-responsive fluorescent probe (named Hcy-NT) to image the changes in mitochondrial viscosity and HSO3- in a "killing two birds with one stone" manner. Hcy-NT showed an OFF-ON fluorescence signal for the increase in cell viscosity induced by nystatin, while an ON-OFF fluorescence signal for intracellular and endogenous HSO3-. Its limits of detection for HSO3- were calculated by both absorption and fluorescence methods, which were 1.200 and 1.291 μM, respectively. This work provides a valuable tool for the study of viscosity and HSO3- related physiological processes and the diagnosis of potential diseases.

Construction of a novel ESIPT and AIE-based fluorescent sensor for sequentially detecting Cu2+ and H2S in both living cells and zebrafish

The development of effective methods for tracking Cu²⁺ and H₂S in living organisms is urgently required due to their vital function in a variety of pathophysiological processes. In this work, a new fluorescent sensor BDF with excited-state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) features for the successive detection of Cu²⁺ and H₂S was constructed by introducing 3,5-bis(trifluoromethyl)phenylacetonitrile into the benzothiazole skeleton. BDF showed a fast, selective and sensitive fluorescence "turn off" response to Cu²⁺ in physiological media, and the situ-formed complex can serve as a fluorescence "turn on" sensor for highly selective detection of H₂S through the Cu²⁺ displacement approach. In addition, the detection limits of BDF for Cu²⁺ and H₂S were determined to be 0.05 and 1.95 μM, respectively. Encouraged by its favourable features, including strong red fluorescence from the AIE effect, large Stokes shift (285 nm), high anti-interference ability and good function at physiological pH as well as a low toxicity, BDF was successfully applied for the consequent imaging of Cu²⁺ and H₂S in both living cells and zebrafish, making it an ideal candidate for detecting and imaging of Cu²⁺ and H₂S in live systems.

Cascade reaction-based highly sensitive fluorescent sensing systems applicable for dual-pattern fluorescence visualizing of thiophenol flavors in meat products and condiments

Thiophenols (ArSHs) are widely used as popular flavoring ingredients for making daily dishes. Dissecting the ArSHs contents in common foodstuffs is meaningful in the field of food safety science. Herein, a novel small-molecule sensor 2-(1H-benzo[d]imidazol-2-yl)-3-(2-(2,4-dinitrophenoxy)-4-morpholinophenyl)acrylonitrile (NOSA) has been tailored. The NOSA is able to respond to ArSHs, spontaneously yielding highly green-emissive fluorescent iminocoumarin (I₅₀₀). This cascade reaction-based strategy is sensitive (limit-of-detection = 2.8 nM), rapid (within 5 min), and selective toward ArSH flavors. Probe NOSA has been applied to the determination of ArSHs in real-life meat products and condiments. Moreover, a far-red fluorescent compound, 2-(7-(diethylamino)-4-(4-(methylthio)styryl)-2H-chromen-2-ylidene)malononitrile (CMMT), has been first combined with NOSA to construct a composite probe NOSA@CMMT for the ratiometric detection of ArSHs (I₅₀₀/I₆₃₀). System NOSA@CMMT exhibits a conspicuous fluorescence change from deep-red to light-green. Benefitted from the gorgeous chromatic fluctuation, a smartphone-integrated analysis platform is established for the real-time evaluation of ArSHs level.

A turn-on fluorescent probe based on ESIPT and AIEE mechanisms for the detection of butyrylcholinesterase activity in living cells and in non-alcoholic fatty liver of zebrafish

Butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) are two important cholinesterase enzymes in human metabolism which are closely related to various diseases of the liver. BChE and AChE are difficult to be distinguished due to their similarity in biochemical properties. Therefore, developing BChE-specific probes with high sensitivity and low background reading is desirable for the relevant biological applications. Herein, we reported the design and synthesis of a fluorescent probe HBT-BChE for biological detection and imaging of BChE. The probe is triggered by BChE-mediated hydrolysis, releasing a fluorophore that holds AIEE and ESIPT properties with large Stokes shift (>100 nm), rendering the probe features of low background interference and high sensitivity. The probe can also distinguish BChE from AChE with a low detection limit of 7.540 × 10^-4 U/mL. Further in vitro studies have shown the ability of HBT-BChE to detect intracellular BChE activity, as well as to evaluate the efficiency of the BChE inhibitor. More importantly, the in vivo studies of imaging the BChE activity level in liver tissues using zebrafish as the model animal demonstrated the potential of HBT-BChE as a powerful tool for non-alcoholic fatty liver disease.

A dual-site multifunctional fluorescent probe for selective detection of endogenous H2O2 and SO2 derivatives based on ICT process and its bioimaging application

In this paper, we reported a coumarin-based fluorescent probe for selective detection of H₂O₂/SO₂ derivatives via ICT process. To the best of our knowledge, it was few reported with the same probe to enable visual detection of H₂O₂/SO₂ derivatives in vivo and in vitro. H₂O₂ and SO₃^2- were selectively sensed over other analytes, and the probe displayed 20-fold and 220-fold relative fluorescence intensity respectively, as well as the good linear relationship and the excellent detection limits of 2.7 * 10³ nM and 19.3 nM. Furthermore, the probe was successfully used for fluorescence imaging of the HeLa cells and the mice to monitor exogenous and endogenous H₂O₂ and SO₃^2-, suggesting its potential biomedical application for investigation and detection the intermediate indicator of oxidative stress in vitro and in vivo.

Differentiation of HSA and BSA and Instantaneous Detection of HSO3 - Using Confined Space of Serum Albumins and Live Cell Imaging of Exogenous/Endogenous HSO3. ACS OMEGA 2023;8:2639-2647. [PMID: 36687064 PMCID: PMC9851030 DOI: 10.1021/acsomega.2c07163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The limitations of prevailing probes for the detection of human serum albumin (HSA) and HSO3 - make it challenging to apprehend the cooperative effect of both HSA and HSO3 - in biological systems. Herein, we present a multi-responsive fluorescent probe MGTP, which distinguishes HSA from bovine serum albumin (BSA) through an ∼104-fold fluorescence enhancement at an emission maximum of 595 nm with HSA and only an ∼10-fold increase at an emission maximum of 615 nm with a shoulder at 680 nm with BSA. The absorbance spectrum of MGTP also discriminates HSA and BSA with the respective absorption maxima at 543 nm and at 580 nm. MGTP in the confined space of HSA or BSA undergoes instantaneous conjugate addition of HSO3 - and results in a ratiometric change in fluorescence intensity with diminishing of red fluorescence (600 nm) and emergence of green fluorescence (515 nm). MGTP in the absence of SAs does not react with HSO3 - in phosphate-buffered saline buffer and reacts sluggishly in the dimethyl sulfoxide-water 1:1 mixture. The limit of detection values for the detection of HSA and HSO3 - are 4 and 6.88 nM, respectively. The drug binding studies reveal that MGTP preferably confines itself at the bilirubin site of HSA. In MCF-7 cancer cells, MGTP is localized into mitochondria and reveals both exogenous and endogenous visualization of HSO3 - through a change in fluorescence from the red to green channel.