Sensitive Detection Of Cysteine Research Articles

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.

The fluorescent detection of biothiols and antimicrobial study based on copper(I) iodide coordination polymer

Luminescent copper(I) iodide (CuI)-based coordination polymers (CPs) are well-known for their structural diversity and strong photoluminescence and are considered as promising candidates for optical applications. Here, a fluorescent Cu2I2(2-ap)2(1) (2-ap = 2-aminopyridine) CP was designed, synthesized, and applied to the effective detection of biothiols and antimicrobial study. Based on the strong thiaphilicity of copper (I), the CP 1 was used as a fluorescent probe to detect biothiols, which play important roles in regulating normal physiological processes due to their vital biological functions. Results revealed that the probe was able to achieve selective and sensitive detection of cysteine (Cys), glutathione (GSH), and homocysteine (Hcy) with low detection limits of 1.013 μM, 1.051 μM, and 1.034 μM, respectively. Moreover, the probe was successfully applied to the detection of thiols in human urine, fetal bovine serum, and bovine serum albumin, which demonstrated the potential application in biological samples. Furthermore, a CP/cellulose nanofibers (CP/CNFs) composite film was fabricated for visual detection of biothiols and antimicrobial study. The developed composite film showed good antimicrobial activity against tested bacteria in vitro conditions, thus opening up the antimicrobial application of CP-doped composite film and providing a new perspective and prospect for potential application in food packaging.

Development of a NIR fluorescent probe for highly selective and sensitive detection of cysteine in living cells and in vivo

Cysteine (Cys) plays important physiological roles in the human body, and abnormal Cys concentrations can cause a variety of diseases. Thus, detecting Cys with high selectivity and sensitivity in vivo is important. Near-infrared (NIR) fluorescent probes are widely employed in biological detection because of their excellent optical properties such as minimal damage to biological samples, low background interference and high signal-to-noise ratio. However, few NIR fluorescent probes that can detect Cys over homocysteine (Hcy) and glutathione (GSH) have been reported because of their similar reactivity and structure. In this work, a highly water-soluble NIR probe (CYNA) for detecting Cys whose structure is similar to that of indocyanine green and is based on cyanine skeleton was synthesized and via aromatic nucleophilic substitution–rearrangement (SNAr-rearrangement) to specific recognize the cysteine. The probe showed high selectivity toward Cys and superior biosecurity, excellent biocompatibility and prolonged dynamic imaging. It also has long fluorescence emission wavelength (820 nm), low detection limit (14 nM) and was successfully applied for visualizing Cys in living cells and mice, which has great promise for applications in noninvasive vivo biological imaging and detection.

Three asymmetric BODIPY derivatives as fluorescent probes for highly selective and sensitive detection of cysteine in living cells.

Biothiols are widely involved in various important physiological activities and play a significant role in maintaining redox homeostasis in living organisms. Herein, we designed and synthesized three new asymmetric fluorescent probes (BDP-S-Ph, BDP-S-ENE and BDP-S-R) to discriminate Cys from Hcy/GSH. These probes reacted with Cys to form meso-amino-BODIPYs via SNAr substitution-rearrangement, thereby inducing a fluorescence turn-on effect. Moreover, they could selectively and sensitively detect Cys in solution with low detection limits (50 nM, 28 nM and 87 nM, respectively). Through comparing the response rates of the three probes to Cys, we concluded that the increase of conformational restrictions led to a decrease in probe reactivity. Besides, the sensing mechanism was demonstrated by mass spectrometry. Furthermore, cell experiments indicated that the probes were able to image exogenous and endogenous Cys through green or red channels in living cells.

Fluorescence switch of gold nanoclusters stabilized with bovine serum albumin for efficient and sensitive detection of cysteine and copper ion in mice with Alzheimer's disease

The near-infrared fluorescence of gold nanoclusters stabilized with bovine serum albumin (BSA -AuNCs) centered at 675 nm could be enhanced by cysteine and then effectively quenched by copper ion (Cu2+), therefore, cysteine and copper ion could be detected in sequence. At “on” state, fluorescence enhancement of BSA-AuNCs is generated due to the reaction between cysteine and BSA-AuNCs, via filling the surface defect of gold nanoclusters, while Cu2+ can further oxidize the reductive sulfydryl of cysteine and interact with amino acids presented in the BSA chain, inducing gold nanoclusters to aggregate, thus causing “off” state with fluorescence quenching. Fluorescence switch of BSA-AuNCs can be used for cysteine and Cu2+ detection in mice brain with Alzheimer's disease (AD) in vitro, with fast response, high chemical stability and sensitivity. Besides, it was able to image the endogenous Cu2+ in liver and heart of AD mice in situ. The results are promising, especially in the framework of early diagnosis of Alzheimer's disease.

A turn-on fluorescence strategy for biothiols determination by blocking Hg(II)-mediated fluorescence quenching of adenine-rich DNA-templated gold nanoclusters.

Fluorescent adenine (A)-rich DNA-templated gold nanoclusters were demonstrated to be a novel probe for determination of biothiols (including cysteine, glutathione, and homocysteine). Fluorescence intensity of adenine-rich DNA-templated gold nanoclusters could be greatly quenched by Hg(II) ions through the formation of a gold nanoclusters-Hg(II) system. When biothiols (cysteine as the model) were introduced into the system, the fluorescence intensity recovered due to the formation of a more stable Hg(II)-thiol coordination complex using Hg-S metal-ligand bonds, which inhibited the Hg(II)-mediated fluorescence quenching of adenine-rich DNA-templated gold nanoclusters. Based on this fluorescence phenomenon, an on-off-on fluorescence strategy was designed for the sensitive determination of biothiols. The method allowed sensitive detection of cysteine with a linear detection range from 100 nM to 5 μM and a limit of detection of 30 nM. Additionally, the assay can be applied for detection of biothiol levels in human plasma samples. Therefore, it can provide a simple and rapid fluorescent platform for biothiol detection.

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.

Development of near-infrared xanthene fluorescence probe for the highly selective and sensitive detection of cysteine

Abnormal levels of the biological thiol cysteine (Cys) have been shown to be associated with growth retardation, skin lesions, and neurotoxicity in humans. In order to fully elucidate the role of Cys in biological systems, its levels must be monitored through in vitro assays as well as in living cells and animals. Herein, we designed and synthesized a novel near-infrared xanthene fluorescence probe (NOF1) with an acrylate group as a trigger moiety to detect Cys over homocysteine and glutathione. The NOF1 probe exhibited a good selectivity and a high sensitivity toward Cys, with a detection limit of 210 nM. Additionally, NOF1 retained good sensitivity and selectivity in human plasma, with a good recovery of Cys within the range 98%–102%. Importantly, the NOF1 probe was successfully applied to the fluorescence imaging of Cys in living cells, zebrafish, and mice, showing great potential for applications involving the detection of Cys both in vitro and in vivo.

Fluorometric determination and intracellular imaging of cysteine by using glutathione capped gold nanoclusters and cerium(III) induced aggregation.

A turn-on fluorometric method is described for selective and sensitive detection of cysteine (Cys). Gold nanoclusters (Au NCs) capped with glutathione (GSH) are used as afluorescent probe. If Ce3+ ion are present, they will bind to the carboxy groups of theGSH-capped Au NC. This results in aggregation-induced emission enhancement (AIEE), best measured at excitation/emission wavelengths of 360/575nm. On addition of Cys, which has less steric hindrance compared with GSHand higher affinity for Ce3+, it will bind toCe3+ through the carboxyl group and link with Au NCs via Au-S bond. Hence, the AIEE is increased and Cys can be quantified via this effect with a linear response in the 0.4-120μmolL-1 Cys concentration range and a detection limit of 0.15μmolL-1. Graphical abstract Schematic presentation of cysteine detection via the Ce3+-triggered aggregation of glutathione capped gold nanoclusterswhich leads to increased yellow fluorescence.

Silicon quantum dot-coated onto gold nanoparticles as an optical probe for colorimetric and fluorometric determination of cysteine.

Silicon quantum dots (SiQDs) were synthesized from N-[3-(trimethoxysilyl)propyl]-ethylenediamine and catechol by a hydrothermal method. Transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the morphology and structure of quantum dots. The SiQDs were then placed on gold nanoparticles (AuNPs). When Cys is added to this solution, Cys will penetrate the SiQDs "shell" of the SiQDs/AuNP composite. This is due to the interaction and conformational differences of Cys and other substance with AuNPs and leads to the dispersion of the aggregated SiQD/AuNPs. A color change from purple to red can be visually observed, and the (green) fluorescence of SiQDs (with excitation/emission peaks at 430/520nm) is restored. This dual-readout nanoprobe was successfully applied to the selective and sensitive detection of cysteine (Cys) in (spiked) serum and urine samples. The detection limit is 3.5nmol·L-1 (at an S/N ratio of 3), and the method works on the 0.01 to 2μM Cys concentration range. Graphical abstract Schematic illustration of a method forsynthesizing silicon quantum dots (SiQDs) and coating them on gold nanoparticles (AuNPs) as an optical probe for colorimetric and fluorometric determination of cysteine.

Molecular switch-modulated fluorescent copper nanoclusters for selective and sensitive detection of histidine and cysteine.

A novel assay for histidine and cysteine has been constructed based on modulation of fluorescent copper nanoclusters (CuNCs) by molecular switches. In our previous work, a dumbbell DNA template with a poly-T (thymine) loop has been developed as an excellent template for the formation of strongly fluorescent CuNCs. Herein, for the first time, we established this biosensor for sensing two amino acids by using dumbbell DNA-templated CuNCs as the single probe. Among 20 natural amino acids, only histidine and cysteine can selectively quench fluorescence emission of CuNCs, because of the specific interaction of these compounds with copper ions. Furthermore, by using nickel ions (Ni2+) and N-ethylmaleimide as the masking agents for histidine and cysteine respectively, an integrated logic gate system was designed by coupling with the fluorescent CuNCs and demonstrated selective and sensitive detection of cysteine and histidine. Under optimal conditions, cysteine can be detected in the concentration ranges of 0.01-10.0μM with the detection limit (DL) of as low as 98pM, while histidine can be detected in the ranges of 0.05-40.0μM with DL of 1.6nM. In addition, histidine and cysteine can be observed with the naked eye under a hand-held UV lamp (DL, 50nM), which can be easily adapted to automated high-throughput screening. Finally, the strategy has been successfully utilized for biological fluids. The proposed system can be conducted in homogeneous solution, eliminating the need for organic cosolvents, separation processes of nanomaterials, or any chemical modifications. Overall, the assay provides an alternative method for simultaneous detection of cysteine and histidine by taking the advantages of high speed, no label and enzyme requirement, and good sensitivity and specificity, and will satisfy the great demand for determination of amino acids in fields such as food processing, biochemistry, pharmaceuticals, and clinical analysis. Graphical abstract.

A novel fluorescent probe with a large stokes shift for cysteine based on dicyanoisophorone

In this work, a dicyanoisophorone-based turn-on fluorescent probe, DCIP, for highly selective and sensitive detection of cysteine was designed based on nucleophilic substitution mechanism. Moreover, compared with typical cysteine probes, DCIP showed great selectivity and sensitivity for cysteine over other amino acids including the similar structured homocysteine (Hcy) and glutathione (GSH). Further, the detection limit toward cysteine was calculated to be as low as 0.70 μM. In addition, the utility of DCIP as a bioanalytical molecular tool was demonstrated by fluorescence imaging of biothiols in living cells.

Selective and sensitive detection of cysteine in water and live cells using a coumarin–Cu2+ fluorescent ensemble

A coumarin–Cu2+ ensemble based fluorescent chemosensor was developed for the selective detection of cysteine in aqueous media and live cells.

Highly selective and sensitive detection of cysteine with a graphene quantum dots-gold nanoparticles based core-shell nanosensor

Reduced graphene quantum dots (r-GQDs) coated gold nanoparticles (AuNPs) core-shell structure is developed as a nanosensor for highly selective and sensitive colorimetric detection of cysteine. The reduction of nitrogen doped GQDs (N-GQDs) by NaBH4 produces r-GQDs, which serve as reductant for facilitating the conversion of HAuCl4 to AuNPs. The abundant hydroxyl groups and amino groups of r-GQDs not only promote the reduction of Au (III) into Au (0), but also facilitate the effective coating of r-GQDs onto AuNPs. The obtained core-shell structured AuNPs@r-GQDs are well dispersed and exhibit an intensive surface plasma band at 525nm. After the adsorption of Ag+ on the surface of AuNPs@r-GQDs, cysteine as cross-linking agent induces the aggregation of AuNPs@r-GQDs and leads to their color change, which allows the sensitive colorimetric detection of cysteine and offers a detection limit low to 5.6nM. More importantly, AuNPs@r-GQDs nanosensor exhibits very high detection selectivity towards cysteine against glutathione (GSH), even at a GSH concentration of 10000-fold higher than that of cysteine. The practicability of this nanosensor is demonstrated by the discriminative determination of cysteine in human plasma.

A selective and sensitive fluorescent sensor for cysteine detection based on bi-8-carboxamidoquinoline derivative and Cu2+ complex.

In this paper, a novel fluorescent sensor 1 for selective and sensitive detection of cysteine was developed based on a complex between bi-8-carboxamidoquinoline derivative ligand (L) and Cu2+ . The interaction of Cu2+ with the ligand causes a dramatic fluorescence quenching most likely due to its high affinity towards Cu2+ and a ligand-metal charge transfer (LMCT) process. The in situ generated L-Cu2 complex was utilized as a chemosensing ensemble for cysteine. In the presence of cysteine, the fluorophore, L, was released from L-Cu2 complex because of the strong affinity of cysteine to Cu2+ via the Cu-S bond, leading to the fluorescence recovery of the ligand. The proposed displacement mechanism was confirmed by the results of mass spectrometry (MS) study. Under optimized conditions, the recovered fluorescence intensity is linear with cysteine concentrations in the range 1×10-6 mol/l to 8×10-6 mol/l. The detection limit for cysteine is 1.92×10-7 mol/l. Furthermore, the established method showed a highly sensitive and selective response to cysteine among the 20 fundamental α-amino acids used as the building blocks of proteins, after Ni2+ was used as a masking agent to eliminate the interference of His. The proposed sensor is applicable in monitoring cysteine in practical samples with good recovery rate.

A novel pyrene based fluorescent probe for selective detection of cysteine in presence of other bio-thiols in living cells

This manuscript reports the synthesis of pyrene-based fluorescent probe (PA-1) containing α,β-unsaturated carbonyl moiety and its application towards the selective and sensitive detection of cysteine (Cys) over other bio-thiols. The probe, 3-(2-hydroxyphenyl)-1-pyrenyl-2-propenone (PA-1) was synthesized through Claisen-Schmidt condensation between acetyl pyrene and salicylaldehyde. The formed product was characterized by 1H NMR, 13C NMR and GC–MS techniques. The probe exhibited absorption maximum at 374nm and emission maximum at 467nm (λex=342nm). The emission intensity of PA-1 was greatly enhanced while adding 2.5nM Cys. This can be attributed to the nucleophilic attack of Cys to the α,β-unsaturated ketone resulting in switching off, intramolecular charge transfer (ICT) from pyrene moiety to the phenolic nucleus. This was confirmed by DFT measurements. The PA-1 exhibited an excellent selectivity towards the determination of 40nM cys in the presence of 250,000-fold higher concentration of common interferents. The emission intensity was linearly increased and the limit of detection was found to be 10pM/L (S/N=3). Interestingly, the response of the PA-1 towards Cys is less than 1min. The confocal laser scanning micrographs of HeLa cells confirmed the cell permeability of the PA-1 and its ability to selectively detect Cys in living cells. In addition, the proposed probe was successfully applied for the determination of Cys in blood serum samples.

A novel colorimetric assay for rapid detection of cysteine and Hg2+ based on gold clusters

Inhibition and recovery of the catalytic activity of bovine serum albumin-capped gold nanoclusters (BSA-AuNCs) is observed for the first time by introduction of cysteine and Hg2+. The prepared BSA-AuNCs possess highly intrinsic peroxidase-like activity. It can catalyze the oxidation of 3, 3, 5, 5-tetramethylbenzidine by H2O2 to produce a blue colored product. Based on this phenomenon, a new colorimetric assay for rapid, selective and sensitive detection of cysteine and Hg2+ in aqueous solution has been demonstrated. The interaction process between target molecule and BSA-AuNCs is very fast, so that the whole test can be completed within ten minutes. Moreover, the fabricated colorimetric sensor is simple and cost-effective, without the need of nucleic acid based recognition element and complicated washing, separation and labeling process, thus holds great promise for routine analysis of cysteine and Hg2+ in real samples.

Surface plasmon coupled emission as a novel analytical platform for the sensitive detection of cysteine

Abstract Thiolated amino acids are biologically important molecules due to their role in protein folding and structure. One such molecule is cysteine (Cys) which acts as a biomarker for diseases like Cancer, HIV, Sepsis, etc. making its rapid detection imperative and essential. In this study, we report the sensitive detection of the thiolated amino acid Cys, from the non-thiolated amino acid arginine (Arg), using the novel Surface Plasmon Coupled Emission (SPCE) platform, characterized with high signal to noise ratios. Our studies were performed on the conventional silver (Ag) SPCE substrate, where Cys was detected to a nanomolar level which is a major improvement to the previously reported level of sensitivity. This can be attributed to the highly sensitive SPCE platform and the unique thiol-Ag interactions associated specifically with Cys. We have also shown the role and influence of the coating process on sensitivity of detection, and substantiated the advantages of SPCE over the SPR based strategy of detection. The simplistic and economical SPCE platform enabled the sensitive detection of Cys that is of biological and medical relevance.

Bio-functionalized silver nanoparticles: a novel colorimetric probe for cysteine detection.

Chemical interactions between nanoparticles and biomolecules are vital for applying nanoparticles in medicine and life science. Development of sensitive, rapid, low-cost, and eco-friendly sensors for the detection of molecules acting as disease indicator is need of an hour. In the present investigation, a green trend for silver nanoparticle synthesis was followed using leaf extract of Calotropis procera. Silver nanoparticles exhibited surface plasmon absorption peak at 421 nm, spherical shape with average size of 10 nm, and zeta potential of -22.4 mV. The as-synthesized silver nanoparticles were used for selective and sensitive detection of cysteine. Cysteine induces aggregation in stable silver nanoparticles owing to selective and strong interaction of -SH group of cysteine with silver nanoparticle surface. Cysteine-induced silver nanoparticle aggregation can be observed visually by change in color of silver nanoparticles from yellow to pink. Cysteine concentration was estimated colorimetrically by measuring absorption at surface plasmon wavelength. Limit of detection for cysteine using silver nanoparticles is ultralow, i.e., 100 nM. The mechanistic insight into cysteine detection by silver nanoparticles was investigated using FT-IR, TEM, DLS, and TLC analysis. Proposed method can be applied for the detection of cysteine in blood plasma and may give rise to a new insight into development of eco-friendly fabricated nanodiagnostic device in future.

Intriguing manipulation of metal-enhanced fluorescence for the detection of Cu(II) and cysteine.

Commercially available salicylaldehyde, in alkaline medium, exhibits strong fluorescence after one hour of UV exposure in the presence of Ag(I) . The phenolic group of salicylaldehyde is converted into the quinone form under alkaline conditions in the presence of AgNO3 , resulting in aggregated Ag(0), which causes approximately 250 times fluorescence enhancement of the in situ produced quinone. Such high silver-enhanced-fluorescence (SEF) is selectively quenched by cysteine, arginine, histidine, methionine, and tryptophan. In contrast to the other amino acids, ageing brings selectivity of the cysteine-induced quenching effect. Interestingly, Cu(II) is found to be the only metal ion that exclusively regenerates the lost fluorescence. Thus, quenching and recovery of fluorescence (Turn Off/On) can be used for the selective and sensitive detection of cysteine as well as Cu(II) ions in one pot. Alteration of the electric field density around the fluorophore (lightening rod effect) and scattering/absorption cross-section have been proposed to account for the Off/On fluorescence.