Selective Detection Of Cys Research Articles

A ratiometric fluorescent probe for cysteine and glutathione differentiation and its application for cysteine detection in foods

Cysteine (Cys) and glutathione (GSH) are crucial biothiols implicated in cellular redox balance, necessitating accurate detection methods. Herein, we developed a novel fluorescent probe based on the fluorescent dye pyronin (PYR), capable of monitoring both Cys-and GSH using ratiometric fluorescence signals. The probe, named PYR-CG, where "C" stands for Cys-and "G" stands for GSH, demonstrates selective detection capabilities for Cys-and GSH. UV absorption and fluorescence emission spectra changes revealed distinct shifts upon interaction with Cys-and GSH. Theoretical and experimental studies validated PYR-CG's responsiveness to Cys-and GSH, elucidating its mechanism as a ratiometric probe. Notably, PYR-CG exhibited rapid response kinetics for Cys-and GSH, with low detection limits of 88 nM and 164 nM, respectively. Importantly, PYR-CG demonstrated exceptional selectivity for Cys-and GSH over interfering analytes. Screening of molecules with similar structures to Cys-further affirmed PYR-CG's specificity, particularly towards N-terminal Cys-in peptides. Furthermore, recovery experiments underscored PYR-CG's reliability for quantitative Cys-detection in complex food samples. Our findings highlight the innovative design and practical applicability of PYR-CG, offering a valuable tool for sensitive and selective detection of Cys-in diverse biological and food samples.

Simultaneous SERS Sensing of Cysteine and Homocysteine in Blood Based on the CBT-Cys Click Reaction: Toward Precisive Diagnosis of Schizophrenia.

At present, there is a lack of sufficiently specific laboratory diagnostic indicators for schizophrenia. Serum homocysteine (Hcy) levels have been found to be related to schizophrenia. Cysteine (Cys) is a demethylation product in the metabolism of Hcy, and they always coexist with highly similar structures in vivo. There are few reports on the use of Cys as a diagnostic biomarker for schizophrenia in collaboration with Hcy, mainly because the rapid, economical, accurate, and high-throughput simultaneous detection of Cys and Hcy in serum is highly challenging. Herein, a click reaction-based surface-enhanced Raman spectroscopy (SERS) sensor was developed for simultaneous and selective detection of Cys and Hcy. Through the efficient and specific CBT-Cys click reaction between the probe containing cyan benzothiazole and Cys/Hcy, the tiny methylene difference between the molecular structures of Cys and Hcy was converted into the difference between the ring skeletons of the corresponding products that could be identified by plasmonic silver nanoparticle enhanced molecular fingerprint spectroscopy to realize discriminative detection. Furthermore, the SERS sensor was successfully applied to the detection in related patient serum samples, and it was found that the combined analysis of Cys and Hcy can improve the diagnostic accuracy of schizophrenia compared to a single indicator.

Green synthesis of silver nanoparticles from corn cob aqueous extract for colorimetric cysteine detection in serum simulated with cysteine samples

ObjectiveIn this study described a green approach for synthesizing silver nanoparticles (AgNPs) with corncob acting as a reducing and stabilizing agent to rapidly detect of L-Cysteine (Cys). To obtain an appropriate condition of synthesizing AgNPs variations in the reactant condition such as concentration, pH, and processing speed were altered. The synthesized AgNPs, that have sizes of 50–100 nm were capped by corncob extract (CCB), became virtually hexagonal and re-dispersed well in aqueous solution. AgNPs were explored for their possible structural characterization. Significantly, the CCB/AgNPs combination demonstrated very high sensitivity for Cys detection with a 30 nM limit of detection (LOD) and selective detection of Cys among 12 amino acids. Furthermore, the CCB/AgNPs combination was applied to detect Cys in human serum with an error rate of less than 5%. As a result of this work, a rapid approach for Cys detection employing green-synthesized AgNPs was developed.

Selective detection of Cys and GSH by using one fluorescent probe at two excitation wavelengths

Selective detection of Cys and GSH by using one fluorescent probe with two different excitation wavelengths is developed based on a naphthyl-coumarin aldehyde probe. Mechanistic studies indicate that the distinctively different fluorescent responses of the probe toward Cys and GSH at the two excitation wavelengths are due to two different reaction pathways that generate different products. The probe has been used to detect Cys and GSH in HeLa cells by using two emission channels.

Highly selective discrimination of cysteine from glutathione and homo-cysteine with a novel AIE-ESIPT fluorescent probe

Biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play pivotal roles in numerous physiological events, however, due to the similar structures and reactivities, differentiation of these biothiols remains a challenging task. Herein, we reported a maleimide-appended fluorescent probe ABTT-MA capable of specific sensing of Cys over other structure-alike biothiols with an ultralow detection limit (9.4 nM). Via a series of investigations into the mechanism, the high selectivity toward Cys is ascribed to a Michael addition/S,N-intramolecular rearrangement cascade reaction, in which the involvement of the mercapto and the adjacent amino groups is necessary to proceed the sensing process. Given this presupposition, Cys could be kinetically discriminated from Hcy and GSH. Upon the addition of Cys, a strong fluorescence appeared and the intensity at 503 nm was correlated with Cys concentration linearly over a wide range (0–10 μM). Thanks to the aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) activity, the selective detection of Cys was realized not only in aqueous media but in the paper-based point-of-care test (POCT). Significantly, the practicability of ABTT-MA in exogenous and endogenous Cys imaging in living cells was elucidated as well.

A New Fluorescent Probe for Selective Detection of Endogenous Cysteine and Live Cell Imaging

AbstractThe detection of biothiols has attracted extensive interest owing to their vital importance in maintaining bioprocesses. Here, we reported a fluorescent probe MANK with facile preparation and excellent water solubility, which can effectively distinguish Cys from its two analogues glutathione (GSH) and homocysteine (Hcy) with a large “turn‐on” fluorescent signal of more than 40‐fold enhancement. Importantly, during the selective detection of Cys, the large concentration differences of three biothiols in living cells had been taken into account. The maleyl group in MANK acted both as a recognition site and fluorescence quenching group. And in the presence of Cys, the thiol group of Cys reacted with maleyl group of MANK by nucleophilic addition and the resulting adduct restored fluorescence emission with a high fluorescent quantum yield of 0.40 in phosphate buffered saline (PBS). Finally, it was successfully utilized to map the endogenous Cys in living cells by confocal microscopy.

Photoluminescence and Electrochemiluminescence Dual-Signaling Sensors for Selective Detection of Cysteine Based on Iridium(III) Complexes.

Cysteine (Cys) is important in biosynthesis, detoxification, and metabolism. The selective detection of Cys over structurally similar homocysteine (Hcy) or glutathione (GSH) remains an immense challenge. Although there are many methods for detecting Cys, photoluminescence (PL) and electrochemiluminescence (ECL) techniques are well-suited for clinical diagnostics and analytical technology because of their high sensitivities. Herein, we report PL and ECL dual-channel sensors using cyclometalated iridium(III) complexes for the discrimination of Cys from Hcy and GSH. The sensors react with cysteine preferentially because of kinetic differences in intramolecular conjugate addition/cyclization, enabling phosphorescence enhancement and ECL decrease in the blue-shifted region. Sensor 1 shows ratiometric PL turn-on and ECL turn-off for Cys. In addition, unique ECL-enhancing behavior of sensor 1 toward GSH enables discrimination between Cys and GSH. Sensor 1 was successfully applied to the detection of Cys in human serum by the ECL method. We demonstrate the first case of a Cys-selective PL and ECL dual-channel chemodosimetric sensor based on cyclometalated iridium(III) complexes and expect that the rational design of efficient PL and ECL dual-channel sensors will be useful in diagnostic technology.

A dual-response fluorescent probe for the discrimination of cysteine from glutathione and homocysteine

A highly selective and sensitive turn-on fluorescent BODIPY-based probe for the simultaneous and selective detection of Cys and Hcy/GSH from dual emission channels was developed. The spatial steric hindrance of the methyl groups at 1- and 7-positions in BODIPY skeleton prevented intramolecular displacement of sulfur with amino group of Hcy but not of Cys. GSH molecular skeleton is larger and amino is far away from sulfydryl group, and the product of the reaction of probe with GSH canstay in thiol phase. Therefore, the probe was successfully applied to the detection of Cys from GSH/Hcy. The confocal microscopy experiments implied that this probe is a promising candidate for imaging of Cys and Hcy/GSH in Hela cells.

Meso-heteroaryl BODIPY dyes as dual-responsive fluorescent probes for discrimination of Cys from Hcy and GSH

Two new BODIPY-based turn-on fluorescent probes (BDP-S-1 and BDP-O-6) contained tetramethyl at 1-, 3-, 5- and 7- positions, as well as O-, or S-aryl substituent at 8-position for the simultaneous and selective detection of Cys and Hcy/GSH from dual emission channels were developed. The spatial steric hindrance of the methyl groups at 1- and 7- positions prevented intramolecular displacement of sulfur with amino group of Hcy but not of Cys. Based on different thiols-induced SNAr substitution–rearrangement reaction with Cys and Hcy/GSH, leading to the corresponding amino- and thiol-BODIPY dyes with distinct photo-physical properties, these probes could simultaneously and selectively detect Cys and Hcy/GSH. With the help of laser scanning confocal microscope, we demonstrated that these probes could simultaneously sense Cys and GSH in Hela cells using multicolor imaging.

An ion quencher operated lamp for multiplexed fluorescent bioassays.

A novel and adjustable lamp based on competitive interaction among dsDNA-SYBR Green I (SGI), ion quencher, and analyte was designed for bioanalysis. The "filament" and switch of the lamp could be customized by employing different dsDNA and ion quencher. The poly(AT/TA) dsDNA was successfully screened as the most effective filament of the lamp. Two common ions, Hg2+ and Fe3+, were selected as the model switch, and the corresponding ligand molecules cysteine (Cys) and pyrophosphate ions (PPi) were selected as the targets. When the fluorescence-quenched dsDNA/SGI-ion complex was introduced into a target-containing system, ions could be bound by competitive molecules and separate from the complex, thereby lighting the lamp. However, no light was observed if the biomolecule could not snatch the metal ions from the complex. Under the optimal conditions, sensitive and selective detection of Cys and PPi was achieved by the lamp, with practical applications in fetal bovine serum and human urine. This ion quencher regulated lamp for fluorescent bioassays is simple in design, fast in operation, and is more convenient than other methods. Significantly, as many molecules could form stable complexes with metal ions selectively, this ion quencher operated lamp has potential for the detection of a wide spectrum of analytes. Graphical abstract A novel and adjustable lamp on the basis of competitive interaction among dsDNA-SYBR Green I, ions quencher and analyte was designed for bioanalysis. The filament and switch of lamp could be customized by employing different dsDNA and ions quencher.

Mitochondria-targeted iridium (III) complexes as two-photon fluorogenic probes of cysteine/homocysteine

Fluorescent imaging of cysteine (Cys) and homocysteine (Hcy) is crucial to understand sulphur metabolism in living cells. Whereas two-photon active cyclometalated Ir(III) complex for detecting Cys/Hcy has been rarely reported. Herein, two novel cyclometalated iridium (III) complexes Ir1-Ir2 with different electron-donor were designed, synthesized and fully characterized as well as confirmed by single-crystal X-ray diffraction analysis, which could selectively react with Cys/Hcy, accompanying with an obvious one- and two-photon fluorescence enhancement in vitro. The mechanism for sensing Cys/Hcy was further analyzed in detail by mass spectra and time-dependent density functional theory calculations. It was found that Ir2, bearing ester group, exhibited higher performance on the selective detection of Cys and Hcy compared to Ir1. Notably, the two-photon action cross-section value in the near-infrared region (∼800nm) of Ir2 is significantly enhanced upon the addition of Cys/Hcy. Further application to cellular imaging indicated that Ir2 is membrane permeable and capable of monitoring the changes of intracellular mitochondrial Cys/Hcy. These results support that such two-photon active complexes might provide a promising platform for the detection of mitochondrial Cys/Hcy in living biological systems.

A novel near-infrared fluorescent probe for cysteine in living cells based on a push-pull dicyanoisophorone system

Abstract The near-infrared (NIR) fluorescent probe for rapid, highly sensitive and selective detection of cysteine (Cys) has great significance in both biological and environment sciences. In this work, a novel and specific dicyanoisophorone-based NIR probe for Cys was developed. This probe features remarkably large Stokes shift, with turn-on fluorescence property for highly sensitive and selective detection of Cys over other amino acids including the similar structured homocysteine (Hcy) and glutathione (GSH). The probe based on the conjugate addition-cyclization reaction, and has low detection limit of Cys. Furthermore, this probe shows great potential for Cys detection, which was successfully applied to bioimage Cys in living cells with low cytotoxicity.

Amino Nitrogen Quantum Dots-Based Nanoprobe for Fluorescence Detection and Imaging of Cysteine in Biological Samples.

Fluorescent amino nitrogen quantum dots (aN-dots) were synthesized by microwave-assisted method using 2-azidoimidazole and aqueous ammonia. The aN-dots have a nitrogen component up to 40%, which exhibit high fluorescence quantum yield, good photostability, and excellent biocompatibility. We further explored the use of the aN-dots combined with AuNPs as a nanoprobe for detecting fluorescently and imaging of cysteine (Cys) in complex biological samples. In this sensing system, the fluorescence of aN-dots was quenched significantly by gold nanoparticles (AuNPs), while the addition of Cys can lead to the fluorescence signal recovery. Furthermore, we have demonstrated that this strategy can offer a rapid and selective detection of Cys with a good linear relationship in the range of 0.3-3.0 μmol/L. As expected, this assay was successfully applied to the detection of Cys in human serum and plasma samples with recoveries ranging from 90.0% to 106.7%. Especially, the nanoprobe exhibits good cell membrane permeability and excellent biocompatibility by CCK-8 assay, which is favorable for bioimaging applications. Therefore, this fluorescent probe ensemble was further used for imaging of Cys in living cells, which suggests our proposed method has strong potential for clinical diagnosis. As a novel member of the quantum-dot family, the aN-dots hold great promise to broaden applications in biological systems.

A Simple and Effective Ratiometric Fluorescent Probe for the Selective Detection of Cysteine and Homocysteine in Aqueous Media.

Biothiols such as cysteine (Cys) and homocysteine (Hcy) are essential biomolecules participating in molecular and physiological processes in an organism. However, their selective detection remains challenging. In this study, ethyl 2-(3-formyl-4-hydroxyphenyl)-4-methylthiazole-5-carboxylate (NL) was synthesized as a ratiometric fluorescent probe for the rapid and selective detection of Cys and Hcy over glutathione (GSH) and other amino acids. The fluorescence intensity of the probe in the presence of Cys/Hcy increased about 3-fold at a concentration of 20 equiv. of the probe, compared with that in the absence of these chemicals in aqueous media. The limits of detection of the fluorescent assay were 0.911 μM and 0.828 μM of Cys and Hcy, respectively. 1H-NMR and MS analyses indicated that an excited-state intramolecular proton transfer is the mechanism of fluorescence sensing. This ratiometric probe is structurally simple and highly selective. The results suggest that it has useful applications in analytical chemistry and diagnostics.

Green synthesis of silver nanoparticles with bagasse for colorimetric detection of cysteine in serum samples

This work reported a green method of synthesizing silver nanoparticles (AgNPs) with bagasse acting as reducing and stabilizing agents to rapidly detect l-Cysteine (Cys). The optimal condition of synthesizing AgNPs was obtained by varying the reactant ratio, temperature, and reaction time. The obtained AgNPs with diameters of 18–28 nm were almost spherical and capped by bagasse extract (BAE), and even they were redispersed well in water after centrifugation. The content of Ag in BAE/AgNPs composite was high up to 45.4%. The possible forming mechanism of AgNPs was investigated. Importantly, the BAE/AgNPs composite showed highly sensitive detection of Cys with a limit of detection (LOD) of 35 nM and selective detection of Cys among 19 amino acids. Besides, the BAE/AgNPs composite was applied in Cys detection in human serum with the error less than 5%. Thus, this work provided a rapid method for Cys detection via green-synthesized AgNPs, and the synthesis method provided a direction for recycle of nanometal.

Rapid and selective detection of Cys in living neuronal cells utilizing a novel fluorescein with chloropropionate–ester functionalities

A chloropropionate-caged fluorescein probe allows for prompt detection of cysteine over other biothiols, e.g., homocysteine with a limit of detection of 12.8 μM.