Selective Detection Of Cysteine Research Articles

A novel fluorescent probe with a large Stokes shift for colorimetric and selective detection of cysteine in water, milk, cucumber, pear and tomato.

Cysteine is an important amino acid that is related to human health and food safety. How to effectively detect Cys in food has received widespread attention. Compared with other methods, fluorescent probes have the advantages of simple operation, high sensitivity, and good selectivity. Therefore, a selective fluorescence probe 2 for Cys in food was designed and synthesized. Probe 2 employed the acrylate group as a thiol-recognition site for Cys, which endowed probe 2 with better selectivity for Cys over Hcy and GSH. The recognition pathway underwent Michael addition, intramolecular cyclization, and concomitant release of the piperideine-based fluorophore, along with a chromogenic change from yellow to orange. This pathway was supported by 1H NMR analysis and DFT calculations. In addition, probe 2 displays a linear response to Cys concentrations (0-30 μM), low detection limit (0.89 μM), and large Stokes shift (125 nm). Overall, probe 2 showed great application potential for the quantitative determination of Cys in water, milk, cucumber, pear and tomato.

Selective detection of Cysteine via plasmonic silver nanotriangles in the presence of KI with an emphasis on mechanism

Silver nanotriangles (Ag NTs), as the plasmonic sensor, were synthesized for the selective and sensitive detection of Cysteine in the aqueous media in the presence of KI. The identification of Cysteine, among other biogenic amino acids, was achieved within the range of 5–80 μM using UV–Vis spectroscopy; i.e., a red-shift was observed in the wavelength of the dipole plasmon resonance (λDPR) in the presence of Cysteine. The detection limit of the sensor was estimated 120 nM. The mechanism behind this selective detection was attributed to the inhibition effect of the Cysteine in the oxidation of the sharp corners of Ag NTs that would happen in the presence of KI. The concentration of Cysteine was correlated with the λDPR red-shift that stems from the Cysteine stabilization of Ag NTs against KI.

A coumarin‐modified graphene quantum dot‐based luminogen for the detection of cysteine in aqueous media

AbstractA biocompatible fluorescence sensor for cysteine detection receives wide appreciation recently, because of its importance in the medical field. Functionalized graphene quantum dots (GQDs) are recently emerging biocompatible quantum dots, which are considered as suitable candidates for biomolecule detection. Motivated by this concept, here we have developed a versatile fluorescent probe based on 3‐aminocoumarin (AMC) functionalized GQDs for the detection of cysteine (Cys). Modification on GQD with AMC resulted in a stable fluorescent probe with an enhancement in quantum yield of about 84% and 40 nm redshift in emission peak compared with bare GQD. The modified GQD is then used for the sensitive and selective detection of cysteine in aqueous media. The detection of Cys within the linear range of 50 nM to 1.5 μM was achieved with a detection limit (LOD) of 0.86 nM. Here, the AMC‐GQD exhibit a turn‐off fluorescence sensing behavior. The quenching mechanism was also explored. The sensing process follows dynamic quenching mechanism, which is attributed to the photoinduced charge transfer from AMC‐GQD to Cys. The Stern–Volmer plot, energy‐level alignment obtained from cyclic voltammetry measurements and density functional theory predictions give a valid proof for this. Furthermore, the sensor was applied efficiently to the determination of Cys in real water samples.

Ultrasmall Pt Nanozymes Immobilized on Spherical Polyelectrolyte Brushes with Robust Peroxidase-like Activity for Highly Sensitive Detection of Cysteine.

Distinct platinum (Pt) nanozymes as peroxidase mimics have received extensive interest owing to their outstanding catalytic activity, high environmental tolerance, lower consumption, and great potential in replacing natural enzymes. However, easy agglomeration of Pt nanoparticles (Pt NPs) resulting from the high surface free energy significantly decrease their peroxidase-like activity. Herein, spherical polyelectrolyte brush (SPB)-stabilized ultrasmall Pt NPs (SPB@Pt NPs) were prepared by a novel synthetic strategy where the SPB not only performed as a nanoreactor for the synthesis of ultrasmall Pt NPs but also greatly stabilized Pt NPs against aggregation. The well-defined SPB@Pt NP nanozymes exhibited outstanding peroxidase-like activity for the catalytic oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized TMB and were then used to establish a colorimetric sensor for rapid detection of cysteine, giving a limit of detection of 0.11 μM. Moreover, the colorimetric detection system was demonstrated with outstanding performance in sensitive and selective detection of cysteine in the presence of several interference molecules. From these results, SPB@Pt NPs have been regarded as promising peroxidase mimics for a large number of applications such as in biosensing, biomedicine, the food industry, and environmental chemistry.

The Two-Steps Reaction Fluorescent Probe for the Selective Detection of Cysteine and Its Applications.

We reported the specific fluorescent probe (MC-BOD-XDS) with two-steps reaction based on monosulfanyl-coumarin-BODIPY for selective detection of cysteine, high activity sulfanyl-coumarin as the multiple reaction group instead of a group internal standard fluorophore. The reaction mechanism of MC-BOD-XDS for detecting cysteine was different from the reported probes about the nucleophilic aromatic substitution reaction (SNAr) of chlorinated BODIPY. The fluorescent color of MC-BOD-XDS changed from yellow to red, and then to orange. The linear calibration diagram showed that it can potentially be used for quantitatively detection of Cys. Its potential applications were demonstrated by employing it for detection of Cys in artificial urine and in fluorescent imaging in HeLa cells.

A novel rosamine-based fluorescent probe for the rapid and selective detection of cysteine in BSA, water, milk, cabbage, radish, apple, and pear

A novel fluorescent probe (RA), based on the rosamine skeleton bearing acrylate group, has been reasonably designed and prepared, which employed an addition-cyclization-elimination sequence reaction mechanism to detect cysteine. RA displayed rapid response to cysteine within 1.5 min, and exhibited satisfactory selectivity for cysteine over H2S, glutathione (Glu), and homocysteine (Hcy), due to the formation of seven-membered lactam favored kinetically. Fluorescence ratio was utilized to detect cysteine from 6.0 to 20.0 μM with a detection limit of 0.29 μM. More, RA was used to monitor cysteine in BSA, water, milk, milk powder, cabbage, radish, apple, and pear.

A simple probe with visible color change for selective detection of cysteine

In this work, we synthesized a simple fluorescent probe, which can selectively detect cysteine. With addition of cysteine, the probe solution showed marked color change from pale yellow to orange color by naked eye. There was an excellent linear relationship between fluorescence intensity of probe and cysteine concentration. Moreover, the probe displayed satisfactory detection limit. Low toxicity and cellular imaging offered the important conditions for detecting cysteine in biological system.

A near-infrared excitation/emission fluorescent probe for imaging of endogenous cysteine in living cells and zebrafish.

The fluorescence imaging technique provides an essential tool for studying biological systems. However, due to the interference of autofluorescence of biological tissues, the application of short-wavelength fluorescent probes in biological imaging was limited. The near-infrared (NIR) excitation/emission fluorescent probe possesses unique advantages in optical imaging in vivo, including less light scattering, minimal photo-damage to biological samples, deep tissue penetration, and weak autofluorescence interference from complicated biological systems. In this work, a convenient fluorophore (E)-2-[2-(6-hydroxy-2,3-dihydro-1H-xanthen-4-yl)vinyl]-3- methylbenzo[d]thiazol-3-ium iodide (DXM-OH) with NIR excitation and emission was rationally designed and developed. What's more, DXM-OH was applied to construct an "OFF-ON" fluorescent probe (E)-2-{2-[6-(acryloyloxy)-2,3-dihydro-1H- xanthen-4-yl]vinyl}-3-methylbenzo[d]thiazol-3-ium iodide (DXM) for sensitive and selective detection of cysteine (Cys). The experimental results showed that DXM had the advantages of good cell permeability, low toxicity, and excellent optical properties (NIR excitation/emission) and it was successfully applied to image Cys of living cells and zebrafish.

Selective Detection of Cysteine at a Mesoporous Silica Film Electrode Functionalized with Ferrocene in the Presence of Glutathione

AbstractUnmodified and ferrocene‐functionalized mesoporous silica layers exhibiting vertical nanochannels have been grown through electrochemically assisted self‐assembly onto indium‐tin oxide (ITO), and the resulting film electrodes have been applied for the electrochemical detection of cysteine. When using the unmodified film electrode and ferrocenedimethanol (Fc(MeOH)2) as a mediator in solution, both cysteine and glutathione can be oxidized by the Fc(MeOH)2+ generated at the electrode surface, but the electron transfer rates were three times faster with cysteine than with glutathione. This can be exploited for the reagent‐free selective detection of cysteine over glutathione by using a ferrocene‐functionalized mesoporous silica film on an ITO electrode, based on a combination of charge transfer kinetic and mass transport limitations through the oriented nanochannels. This has been demonstrated here by using cyclic voltammetry and amperometry in flow‐injection analysis mode. A sensitivity of 1.28 mA M−1 was measured for the cysteine concentration range of 3–20 μM with a repeatability of the signal between 3 and 12 %. The lowest concentration of cysteine experimentally detected was 3 μM.

A water-soluble near-infrared fluorescent probe for sensitive and selective detection of cysteine

A near-infrared (NIR) fluorescent probe (Cys-AN) for selective and sensitive detection of cysteine (Cys) was designed and synthesized. The fluorescent probe was water-soluble and had a large Stokes shift of 150 nm, whose detection limit could reach to 0.96 μM in PBS buffer. After we analyzed the HRMS, TLC and optical data, a proposed sensing mechanism for the detection of Cys could result from the Michael addition and intramolecular cyclization reactions between the probe and Cys, followed by intramolecular charge transfer (ICT) process to afford the NIR fluorescent signal at 674 nm. Meanwhile, Cys-AN exhibited low cytotoxicity, and was successfully applied for bioimaging of Cys in living cells.

A Asp/Ce nanotube-based colorimetric nanosensor for H2O2-free and enzyme-free detection of cysteine

A novel colorimetric nanosensor has been developed for high sensitive and selective detection of cysteine (Cys) based on the intrinsic oxidase-like activity of cerium nanotube coordinated with aspartic acid (Asp/Ce-NT). Under the function of Asp/Ce-NT, colorimetric reaction of TMB (3,3′,5,5′-tetramethylbenzidine) takes place within five minutes without the assistance of additional oxidizing agents (e.g. H2O2). The oxidase-like activity of Asp/Ce-NT can be modulated by adjusting the ratio of Asp to Ce(NO3)3 during preparation process as well as the chirality of Asp (levogyration/L and dextrorotation/D). Compared with D-Asp/Ce-NT, L-Asp/Ce-NT exhibits more excellent activity which can be specifically depressed by Cys. According to the developed strategy, limit of detection for Cys reaches as low as 33.2 nM. The avoiding use of H2O2 would improve the repeatability and reliability. Nice recoveries from 92.5% to 100.8% are found for Cys detection in serum samples. The developed sensing assay is cost-effective and operated in H2O2-free and enzyme-free condition, providing an effective rapid detection way for practical application in disease monitoring and diagnosis.

A novel near-infrared fluorescent probe with a “donor–π–acceptor” type structure and its application in the selective detection of cysteine in living cells

A novel “donor–π–acceptor” type fluorescent probe has been prepared for the detection of Cys. This probe shows great fluorescent performance and obvious response to Cys, and has been successfully applied in visualizing Cys in living cells.

Chemical etching of pH-sensitive aggregation-induced emission-active gold nanoclusters for ultra-sensitive detection of cysteine.

This study reports the utilization of thiol-induced chemical etching of aggregation-induced emission (AIE)-active Au nanoclusters (NCs) for the facile, sensitive, and selective detection of cysteine. The AIE-active Au NCs were formed in an acidic solution containing excess Au(i)-thiolate complexes. At an acidic pH (2.0), the emission of these Au NCs was enhanced by cysteine at a concentratioin below 1 mM. However, the emission was quenched by cysteine at a high concentration, e.g., 500 mM, via the thiol-induced etching of gold, although the process occurred very slowly. Interestingly, in the absence of cysteine, increasing the solution pH enhanced the emission, while the presence of cysteine remarkably accelerated the etching-induced quenching process. The complete quenching of the emission by excess cysteine at pH 2.0 and the enhancement of the emission by the increasing pH in the absence of cysteine indicated that aurophilicity might not be involved in the AIE of the Au NCs prepared using glutathione (GSH) both as the reducing and protecting reagent. On the other hand, the etching process involved the penetration of cysteine molecules through the Au(i)-thiolate complexes, which could assemble or disassemble around the embedded Au NCs in response to the solution pH to get access to the innermost Au(0) cores. Therefore, a facile, sensitive, and selective method for the detection of cysteine was established. This method exhibited an extremely wide linear range as wide as nine orders of magnitude above the cysteine concentration, including two linear regions of the relative emission intensity of the Au NCs versus the logarithm of cysteine concentration, from 10 pM to 150 μM (correlation coefficient, 0.99851) and from 150 μM to 2 mM (correlation coefficient, 0.99866). An ultra-low limit of detection of 6.3 pM (S/N = 3) was also achieved. The developed method showed superior selectivity for cysteine relative to the 19 other natural amino acids and GSH. The method was applied for the analysis of human serum samples spiked with cysteine with satisfactory results. This study demonstrates the potential of the thiol-induced chemical etching approach as a powerful tool for studying luminescent metal NCs.

A near-infrared fluorescent probe for direct and selective detection of cysteine over homocysteine and glutathione

In this work, we have designed and synthesized the fluorescent probe 1, which showed a highly selective and sensitive response to Cys over Hcy/GSH in the test. Moreover, the color of probe solution has changed dramatically from colorless to pink with the addition of Cys within 10 min. Meanwhile, the fluorescence intensity exhibited perfectly positive correlation with concentration of Cys from 0 to 200 μM, which offered the important condition for quantitative analysis. Finally, the bioimaging and fluorescence response of probe 1 for fetal calf serum are a powerful safeguard for practical detection of Cys. Therefore, this near-infrared probe will be of great benefit for detecting Cys in the biological systems.

N-Doped Graphene Quantum Dots-Decorated V2O5 Nanosheet for Fluorescence Turn Off-On Detection of Cysteine.

The development of a fast-response sensing technique for detection of cysteine can provide an analytical platform for prescreening of disease. Herein, we have developed a fluorescence turn off-on fluorescence sensing platform by combining nitrogen-doped graphene quantum dots (N-GQDs) with V2O5 nanosheets for the sensitive and selective detection of cysteine in human serum samples. V2O5 nanosheets with 2-4 layers are successfully synthesized via a simple and scalable liquid exfoliation method and then deposited with 2-8 nm of N-GQDs as the fluorescence turn off-on nanoprobe for effective detection of cysteine in human serum samples. The V2O5 nanosheets serve as both fluorescence quencher and cysteine recognizer in the sensing platform. The fluorescence intensity of N-GQDs with quantum yield of 0.34 can be quenched after attachment onto V2O5 nanosheets. The addition of cysteine triggers the reduction of V2O5 to V4+ as well as the release of N-GQDs within 4 min, resulting in the recovery of fluorescence intensity for the turn off-on detection of cysteine. The sensing platform exhibits a two-stage linear response to cysteine in the concentration range of 0.1-15 and 15-125 μM at pH 6.5, and the limit of detection is 50 nM. The fluorescence response of N-GQD@V2O5 exhibits high selectivity toward cysteine over other 22 electrolytes and biomolecules. Moreover, this promising platform is successfully applied in detection of cysteine in human serum samples with excellent recovery of (95 ± 3.8) - (108 ± 2.4)%. These results clearly demonstrate a newly developed redox reaction-based nanosensing platform using N-GQD@V2O5 nanocomposites as the sensing probe for cysteine-associated disease monitoring and diagnosis in biomedical applications, which can open an avenue for the development of high performance and robust sensing probes to detect organic metabolites.

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.

A novel fluorescent probe for highly sensitive and selective detection of cysteine and its application in cell imaging

A new fluorescent probe (ABPA) based on 1,8-naphthalimide, which designed on the “receptor1-fluorophore-spacer-receptor2” model and employed conjugated addition/cyclization sequence mechanism for Cys detection was reported. The probe shows high selectivity and sensitivity for cysteine (Cys) over other amino acids including the similar structured homocysteine (Hcy) and glutathione (GSH). It displays a highly sensitive fluorescence emission to Cys with a detection limit of 0.12μM (S/N=3), which is far below the normal level of Cys (30–200μM) in living cells. Furthermore, ABPA was successfully applied to bioimage intracellular Cys in living cells with low cytotoxicity.

Synthesis and evaluation of a new fluorescein and rhodamine B-based chemosensor for highly sensitive and selective detection of cysteine over other amino acids and its application in living cell imaging

A new fluorescent probe (TRDM-F) based on a molecular chain of open-loop maleic anhydride, rhodamine B and fluorescein was designed, synthesized and evaluated to develop a chemosensor. Photochemical studies show that fluorescence properties of TRDM-F are dominated by fluorescein group in the pH range of 2–10. UV–vis absorption and fluorescence spectroscopic studies further display a high selectivity towards Cys over GSH/Hcy and other amino acids and a high sensitivity towards Cys (0.088–270μM) with 95-fold fluorescence enhancement in a HEPES buffer solution (10mM, pH=7.4) containing 20% MeCN at room temperature. We further demonstrated that the proposed method was satisfactorily applied to the discrimination of Cys in living Hela cells with low cell toxicity.

Selective detection of cysteine over homocysteine and glutathione by a simple and effective probe

A simple fluorescent probe, with a latent coumarin fluorophore and an acrylate recognition site, is able to selectively and quantificationally detect cysteine over other biothiols, such as homocysteine and glutathione.

Diketopyrrolopyrrole-based ratiometric fluorescent probe for the sensitive and selective detection of cysteine over homocysteine and glutathione in living cells

A new fluorescent probe (DPP-AC) based on diketopyrrolopyrrole with an acrylate group was designed and synthesized for the sensitive and selective detection of biological thiols.