Sensor For Cys Research Articles

A metal–organic framework composite loaded with coumarin guests as a turn-on luminescent sensor for detection of cysteine in aqueous solution

In this work, a composite material (ACE@UiO-66-NH2) has been synthesized conveniently by loading a cysteine-responsive molecular probe Acrylic acid 3-acetyl-2-oxo-2H-chromen-7-yl ester (ACE) on a UiO-type zirconium-based metal–organic framework (UiO-66-NH2). Furthermore, the resulting ACE@UiO-66-NH2 demonstrated to be a fluorescent turn-on probe for selective recognition of Cys from other amino acids in aqueous HEPES buffer systems. Additionally, the proposed recognition mechanism has been confirmed by 1H NMR and TLC. The study provided a promising approach to rationally design MOF-based fluorescent sensor for Cys in aqueous system.

Sustainable Synthesis of MIL-53(Al)-Cys Based Chemosensor for the Fluoro-Chromogenic Detection of Copper

Copper is the third most abundant heavy metal in the environment important for human survival. However, in excess it can have deleterious effects on aquatic as well as terrestrial beings. The detection of Cu2+ has huge significance in food safety and environment monitoring. The conventional detection methods are costly and complex. Therefore, we have designed a waste derived material for Cu2+ determination in complex samples. Our work is based on the eco-friendly synthesis of waste derived Al-MOF with remarkable properties grafted with L-Cysteine to develop the novel MIL-53(Al)-Cys sensor. The formation of the sensing probe was verified by various characterization techniques including FE-SEM, HR-TEM, PXRD, FTIR, UV-Vis and Photoluminescence spectroscopies. The developed waste-derived probe showed multifunctional properties with the visual and fluorescent detection of Cu2+ ions with high sensitivity and fast response time. The proposed waste-derived fluoro-chromogenic sensor exhibited a “turn of” detection response mechanism with a visual color change only the presence of Cu2+ ions. The results showed reproducible, selective and stable response with a LOD of 0.2 ng/mL, which is lower than the permissible levels. Therefore, the observed results highlight the potential of developed waste-derived MIL-53(Al)-Cys chemosensor as a promising platform in water remediation applications.

Enhanced cysteine sensor based on modified gold nanoparticles with synergistic role of pH-responsive poly (N,N-dimethylaminoethyl methacrylate)

The development of a highly sensitive and easy-to-prepare sensor for the detection of cysteine (Cys) is of great importance. Gold nanoparticles (AuNPs) have been frequently utilized as a Cys sensor owing to high affinity of the thiol group to gold. However, the presence of additional materials, such as stabilizers, can impact the sensitivity of this sensor. Herein, pH-sensitive gold nanoparticles (Au-PDA) were synthesized using poly (N,N-dimethylaminoethyl methacrylate) (PDMAEMA) for the purpose of Cys detection based on the aggregation size-dependent optical property of gold nanoparticles. Detection of cysteine was also followed by UV–Vis analysis, showing a decrease in intensity of localized surface plasmon resonance (LSPR) peak, a red shift from 525 to 550 nm as well as the appearance of a new peek at 650 nm. To enhance sensor performance, systematic investigations were conducted to optimize sensing conditions, focusing on pH, gold concentration, and ionic strength of the medium. Remarkably, the proposed sensor exhibited excellent selectivity towards Cys compared to other amino acids. The sensitivity of the sensor was evaluated using two methods: changes in the absorption intensity and the LSPR shift. The pH-sensitivity of PDMAEME led to a significant improvement in sensing parameters through a synergistic effect on the Au-Cys interaction, leading to a remarkably low LOD of 0.0004 nM, which is the lowest ever reported LOD for detection of Cys. Finally, practical application of the proposed sensor was validated in human blood serum.

A new 7-(diethylamino)coumarin and 4-(diethylamino)phenol appended unsymmetrical thiocarbohydrazone: Detection of moisture in organic solvent and sequential fluorimetric detection of Cu2+ ions and cysteine

A novel 7-(diethylamino)coumarin and 4-(diethylamino)phenol appended unsymmetrical thiocarbohydrazone (2) was designed and synthesized successfully. The probe 2 forms an interesting three dimensional hydrogen bonded network results in an interesting supramolecular network. The compound, 2 showed fluorometric and colorimetric response towards fluoride anion via deprotonation process due to the presence of phenolic –OH and –NH groups. The anionic species 2-F− was successfully employed for the detection of moisture in organic solvents through the reprotonation process. The moisture detection features of 2-F− were explored by using UV–vis and emission experiments in DMF solvent and the corresponding mechanism was effectively confirmed by 1H NMR spectral analysis. Moreover, the synthesized probe 2 exhibits highly selective and sensitive detection for Cu2+ ions. Furthermore, the 2-Cu2+ ensemble might be used as a highly selective sensor for Cys in the presence of other amino acids without any interference. Further, the potential reversible sensing feature of Cu2+ and Cys by 2 were recognized to develop the INHIBIT logic gate function and on-site detection of Cu2+ ions and Cys by a paper strip applications.

Dual-functional electrochemical bio-sensor built from Cu2O for sensitively detecting the thiols and Hg2+

Electrochemical bioanalysis has been drawing more attention in recent years, due to the advantages of fast and effective detection capabilities. Intracellular thiols including biothiols (glutathione (GSH), cysteine (Cys) and homocysteine (Hcy)) and endogenous H2S play important biological roles in physiological processes. Therefore, the development of a method for detecting biothiols and distinguishing from endogenous H2S has become a challenge to be addressed. In this work, Cu2O nanostructure was successfully synthesized by electrodeposition process and employed as core part of electrochemical sensing platform for sensitive detecting thiols. The sensor exhibits excellent sensing performance, which is due to the interaction of -SH with Cu (I) via the formation of Cu-S bond. Significantly, the sensor establishes a novel approach for distinguishing biothiols and S2- via different peak current responses for the first time. The limit of detections of the sensor for Cys and S2- have achieved to 6.2 nM and 11.3 nM, respectively. The practical applicability of the sensor was assessed in human urine samples. It is noteworthy that Cu2O-S and Cu2O-Cys systems have been found significant response toward Hg2+, which can be used for detecting Hg2+. The detection limit of Cu2O-S system for Hg2+ was realized at 0.3 nM.

Nanostructured electrochemical cysteine sensor based on carbon nanotube supported Ru, Pd, and Pt catalysts

At present, a voltammetric L-Cystein (Cys) sensor is developed based on carbon nanotube (MWCNT) supported Ru, Pd, and Pt monometallic catalyst modified glassy carbon electrodes (GCE). Ru/MWCNT, Pd/MWCNT, and Pt/MWCNT catalysts are prepared via sodium borohydride reduction method and characterized with advanced surface analytical techniques as inductively coupled plasma mass spectrometry (ICP-MS), N2 adsorption-desorption, X-ray diffraction (XRD), and transission electron microscopy (TEM). Characterization results reveal that these catalysts are succesfully sythesized at desired metal loadings. For electrochemical studies, GCE is modified with Ru/MWCNT, Pd/MWCNT, and Pt/MWCNT catalysts to obtain a disposable, inexpensive, and sensitive sensor for Cys. The electrochemical behavior of the modified GCE is investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Ru/MWCNT modified GCE electrode exhibits best Cys electro-oxidation activity and thus, further electrochemical studies as sensitivity and limit of detection determination, intereference study, and real sample analysis are performed on Ru/MWCNT modified GCE electrode. The Cys sensor has a linear response within the range of 0–200 μM with current sensitivity 0.3058 μA/μM (4307.05 μA/mMcm2), and 0.353 lowest detection limit at (S/N = 3) signal to noise ratio. Interference studies reveal that Ru/MWCNT modified GCE electrode is not affected by d-glucose, uric acid, l-Tyrosine, l-Trytophane, H2O2, homocysteine, and glutathione as common interfering species. The developed sensor based on Ru/MWCNT modified GCE electrode is also employed to quantify Cys in acetylcysteine drug sample. This novel study reports a strategy to sense Cys on Ru/MWCNT modified GCE electrode.

A bond energy transfer based difunctional fluorescent sensor for Cys and bisulfite

In living cells, cysteine (Cys) and bisulfite are involved in many important physiological processes. Their unbalance in vivo would lead to multiple diseases. So, it is vital to develop difuntional sensor for Cys and bisulfite. As we known, cysteine could metabolized into bisulfite by the metabolic processes of cysteine in the animal level. Therefore, we designed and synthesized a mitochondria-targeted long-wavelength ratio fluorescence sensor Z2 for Cys and bisulfite simultaneous detection. Z2 exhibitted excellent selectivity, good anti-interference, fast response and low detection limit. The sensor exhibited obviously two channels fluorescence response for Cys and bisulfite orderly. Z2 is widely used for imaging Cys and bisulfite in MCF-7 cells, zebrafish, and mice, and successfully imaging Cys metabolism in these livings. We hope this bifunctional ratio fluorescence sensor Z2 will be a useful tool to monitor Cys and SO2 levels in living systems.

A novel indanone-derivated fluorescence sensor for Cysteine detection and biological imaging

Unlike normal “regulating” process on linear-arranged donor-π-acceptor system, this work provided a concept of using modified groups to impact the optical properties of the primary fluorophore. Using this concept, we set the hydroxyl-containing indanone as the fluorophore, and introduced various arylidene units to influence the electron withdrawing potential of the CO unit on indanone. Accordingly, a novel indanone-derivated fluorescence sensor for Cys, IND-Cys1, was provided with the structural modification. The linear correlation was applicative for physiological monitoring of Cys (1.0–7.0 equiv. to cover 30–200 μM). The LOQ was tested as 80 nM (0.008 equiv.). IND-Cys1 also had high selectivity for Cys, especially for distinguishing high concentrated GSH (100-fold). It was successfully applied to detect Cys in living cells. Far more than providing a useful tool, this work might supply important information for further systematic optimization of corresponding monitoring implements.

Ultrasound-promoted specific chiroptical sensing of cysteine in aqueous solution and cells

The quantity and chirality of cysteine (Cys) are correlated with diseases and have crucial implications in physiology and pathology. A selective chiral sensor for Cys based on electronic circular dichroism and UV detection was developed, and the sensing reaction takes place rapidly in aqueous solution with the aid of ultrasound. This sensing approach can simultaneously determine the absolute optical purity and total concentration of Cys. The limit of detection is 0.25 μM, and the detection is not impeded by other naturally occurring amino acids or common biothiols. This method is simple to operate and has the advantages of fast detection, high sensitivity and selectivity, and the measurement error is no more than 4%, with application potential for high-throughput screening. A kit containing this sensor was prepared and successfully applied in a sensing study of cells and peptides containing N-terminal Cys residues to detect endogenous and exogenous Cys in cells and determine the absolute configuration of N-terminal Cys in polypeptides. This work has important application prospects for the study of Cys with the aim of diagnosing related diseases.

Electrochemical sensor for L-cysteine by using a cobalt(II)/aluminum(III) layered double hydroxide as a nanocatalyst.

A voltammetric sensor is described for the determination of L-cysteine (Cys). A pencil graphite electrode (PCE) was modified with a Co(II)-Al(III) layered double hydroxide (LDH) to obtain a disposable, inexpensive and sensitive sensor for Cys. The LDH was electrochemically deposited on the PGE by chronoamperometry. The electrochemical behavior of the modified PGE was investigated by cyclic voltammetry, differential pulse voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry. The structure and morphology of the electrodes surface were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Experiments were conducted in optimal condition, scan rate of 10mV. s-1 and the oxidation peak potential 0.15V vs. saturated calomel electrode. The sensor has a linear response in the 100 pM to 0.1μM Cys concentration range and a 100 pM detection limit. It was used to quantify Cys in a drug sample. Graphical abstract Schematic presentation of pencil graphite electrode modification with Co-Al layered double hydroxide nanaocatalyst by chronoamperometry, and its usage as an electrochemical sensor for L-cysteine determination.

Fast electrochemical deposition of CuO/Cu2O heterojunction photoelectrode: Preparation and application for rapid cathodic photoelectrochemical detection of L-cysteine

Cathodic photoelectrochemical (PEC) bioanalysis has been drawing more attention in recent years due to the advantages of excellent anti-interference capability. l-cysteine (Cys) is an essential sulfur-containing amino acid and has been intensively addressed as targets in previous anodic PEC bioanalysis. Herein a novel and simple cathodic PEC l-cysteine (Cys) sensor is reported, on the basis of facile electrochemical fabrication of CuO/Cu2O heterojunction photocathode and the selective interaction between the copper and Cys via the formation of CuS bond. The as-prepared sensor exhibited excellent biosensing performance in terms of high sensitivity, selectivity and stability. In such a sensor, the binding-induced decrease of cathodic photocurrent can be related to target concentration from 0 and 1.5 μM. This cathodic PEC Cys sensor exempted the use of expensive equipment and required no laborious sensor development procedures. We hope it can inspire more interest for further development of simple and practical PEC sensor toward important biomolecules.

Multiple dye-doped silica cross-linked micellar nanoparticles for colour-tuneable sensing of cysteine in an aqueous media and living cells

This work demonstrated the design and synthesis of multiple dye-doped silica cross-linked micellar nanoparticles (MD-SCMNPs) by encapsulating three organic dyes (fluorescein derivative (FCD), coumarin derivative (HCE) and Rhodamine b (RhB)) in SCMNPs cores for colour-tuneable sensing of cysteine (Cys) in aqueous media and in living cells. In the presence of Cys, HCE exhibited blue emission, and RhB exhibited purple emission, while FCD reacted with Cys and exhibited green fluorescence “turn-on” in the core of MD-SCMNPs. This green-light-emitting sensing product may cause “step by step” fluorescent resonance energy transfer (FRET) from HCE to the sensing product and then to RhB. Based on the FRET process in the core, MD-SCMNPs can quantitatively detect Cys by a colour change with a low limit of detection (LOD) of 0.3 μM in living cells. Furthermore, MD-SCMNPs exhibited ultrasmall size (∼12 nm) and excellent dispersity and biocompatibility, which could potentially be used as a visualized Cys sensor for health monitoring and disease prediction in the human body.

Oligo(p-phenylene ethynylene) with Cyanoacrylate Terminal Groups and Graphene Composite as Fluorescent Chemical Sensor for Cysteine.

A chemical sensor for cysteine (Cys) was fabricated based on a fluorescent oligo(p-phenylene ethynylene)s (OPEs) and OPE-graphene oxide (GO) composite. OPE with cyanoacrylate terminal groups were synthesized by a Pd-catalyzed Sonogashira coupling reaction and Knoevenagel condensation for use as a chemical sensor for Cys. The optical properties and Cys sensing capability of the cyanoacrylate modified OPE and OPE-GO composite were investigated. In addition of Cys, the fluorescence of OPE was blue-shifted and decreased (fluorescence turn-off), while the fluorescence of the OPE-GO composite was enhanced (fluorescence turn-on). Thus, OPE with cyanoacrylate terminal groups and OPE-GO composite acts a highly sensitive fluorescent chemical sensor for Cys.

A water-soluble and retrievable ruthenium-based probe for colorimetric recognition of Hg(II) and Cys

A new ruthenium-based complex 1 [(bis(4,4′-dimethylphosphonic-2,2′-bipyridine) dithiocyanato ruthenium (II))] was developed as a colorimetric probe for the detection of Hg(II) and Cys (Cysteine). The obtained compound 1 can give interconversional color changes upon the alternating addition of Hg(II) and Cys in 100% aqueous solution. The specific coordination between NCS groups with Hg(II) can lead to the formation of 1-Hg2+ complex, which can induce a remarkable spectral changes of probe 1. Afterwards the formed 1-Hg2+ complex can act as effective colorimetric sensor for Cys. Owing to the stronger binding affinity of sulfhydryl group to Hg2+, Cys can extract Hg2+ from 1-Hg2+ complex resulting in the release of 1 and the revival of absorption profile of the probe 1. By introducing the hydrophilic phosphonic acid groups, the proposed probe exhibited excellent water solubility. The limits of detection (LODs) of the assay for Hg2+ and Cys are calculated to be 15nM and 200nM, respectively.

Benzothiazole‐Pyimidine‐Based BF2 Complex for Selective Detection of Cysteine

Due to the similar structure and reactivity of cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), the simultaneous discrimination of Cys over Hcy and GSH by a single fluorescent sensor is still a great challenge. In this work, a benzothiazole-pyimidine-based boron difluoride complex (BPB) was developed as a new fluorescent sensor for Cys. The sensor exhibits a highly selective "turn-on" response to cysteine over Hcy, GSH and other amino acids in aqueous solution at physiological pH. The observed pseudo-first-order rate constant for the reaction of BPB with Cys was calculated to be about 0.062 min(-1) . The detection limit of this sensor for Cys was determined to be 332 nm, and bioimaging of exogenous Cys by this sensor was successfully applied in living cells, thus indicating that this sensor holds great potential for biological applications.

Triplex DNA logic gate based upon switching on/off their structure by Ag(+)/cysteine.

The formation of intramolecular triplex DNA can be regulated by Ag(+) and Cys (cysteine), which switch off/on the fluorescence of the oligonucleotides, 5'-TAMRA-TTC TCT TCC TCT TCC TTC TGA CGA CAG TTG ACT CTT CCT TCT CCT TCT CTT-BHQ-2-3' (Oligo 1) and 3'-GAA GGA AGA GGA AGA GAA-5' (Oligo 2). Based on this principle, sensors for Ag(+) and Cys are developed. The sensor for Ag(+) has a linear range of 2.5 nM-40 nM and a detection limit of 1.8 nM, whereas the sensor for Cys has a linear range of 10.0 nM-120.0 nM and a detection limit of 8.2 nM. Furthermore, the fluorescence is reversible with the alternate addition of Ag(+) and Cys. We constructed a DNA logic gate using Ag(+) and Cys as the input, and the fluorescence intensity as the output. The DNA logic gate is simple; moreover, it has a fast response and good reversibility.

A highly selective colorimetric Cys sensor based on core-substituted naphthalene diimides

This study presents the core-substituted naphthalenediimide based probe 1 for the selective detection of cysteine via photoinduced electron transfer (PET) effect.

Ethynyl and π-stacked thymine–Hg2+–thymine base pairs enhanced fluorescence quenching via photoinduced electron transfer and simple and sensitive mercury ion sensing

Ethynyl triggered enhanced fluorescence quenching effect was first reported based on photoinduced electron transfer (PET) between fluorophore and ethynyl. Ethynyl and 6-carboxyl-fluorescein (FAM) were labeled at the 5′- and 3′-termini of a poly d(T) sequence containing three thymine units, respectively. In the presence of Hg2+, Hg2+ binds to two thymine residues through T–Hg2+–T interactions and the formed T–Hg2+–T base pairs bring FAM and ethynyl from two matched sequences into close proximity. On the one hand, π-stacked T–Hg2+–T mediates and accepts electron transfer of the excited state of FAM and quenches the fluorescence through PET. On the other hand, π-stacked interactions between ethynyl and FAM also provide a de-excitation process for the excited state of FAM via PET and trigger an enhanced fluorescence quenching. On the basis of fluorescence quenching, a simple, rapid, and sensitive Hg2+ sensor was constructed; under optimum conditions, a good linear relationship was obtained over the concentration range of 5–150nM for Hg2+ and a very low detection limit (0.42nM) was reached. The developed system was further designed as a cysteine (Cys) sensor based on fluorescence recovery resulted from the strong interaction between Cys and Hg2+; the proposed Cys sensor has a linear range of 10–550nM and a detection limit of 2.5nM. The two sensors were used for analysis of real samples and the satisfactory results were achieved.

Glutathione-Protected Silver Nanoclusters as Cysteine-Selective Fluorometric and Colorimetric Probe

The integration of the unique thiol-Ag chemistry and the specific steric hindrance from the organic layer of fluorescent Ag nanoclusters (AgNCs) was first developed in this work to achieve a simple detection of cysteine (Cys) with high selectivity and sensitivity. The key design is a strongly red-emitting AgNC protected by the interference biothiol, glutathione, or GSH (hereafter referred to as GSH-AgNCs), where both the physicochemical properties (Ag surface chemistry and fluorescence) of the NC core and the physical properties (e.g., steric hindrance) of the organic shell were fully utilized for Cys detection with three major features. First, owing to the specific thiol-Ag interaction, the fluorescent GSH-AgNCs showed superior selectivity for Cys over the other 19 natural amino acids (nonthiol-containing). Second, the GSH protecting layer on the NC surface made possible the differentiation of Cys from GSH (or other large-sized thiol molecules) simply by their size. Third, the ultrasmall size of GSH-AgNCs and the high affinity of the thiol-Ag interaction provided high sensitivity for Cys detection with a detection limit of <3 nM. The assay developed in this study is of interest not only because it provides a simple Cys sensor with high selectivity and sensitivity but also because it exemplifies the utilization of the physical properties of organic ligands on the nanomaterial surface to further improve the sensor performance, which could open a new design strategy for other sensor development.