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Abstract: New rhodamine derivatives bearing binaphthyl group were synthesized as selective fluorescent and colorimetric sensors for Cu2+. Highly selective “off–on” type fluorescent changes were observed upon the addition of Cu2+. Selective fluorescent enhancement of two rhodamine derivatives was attributed to ring opening from the spirolactam (nonfluorescent) to ring-opened amide (fluorescent). A chemo-sensing based on rhodamine derivative was further applied to the microfluidic system. [Copyright &y& Elsevier]

A bifunctional fluorescent pyrene-based probe, PYR , was designed by incorporating pyridine and phenolic hydroxyl moieties into pyrene fluorophore, which exhibited ratiometric fluorescent response toward Al3+. PYR underwent unique monomer-excimer conversion in ratiometric manner through the formation of a 2:1 coordination complex and accomplished with fluorescent color variation from green to blue. PYR displayed excellent selectivity, high sensitivity (LOD = 0.33 μM), rapid response (<45 s), and good cytocompatibility to Al3+. Notably, a fluorescent cellulose membrane decorated with PYR was successfully developed and applied for accurately quantify of Al3+ in diverse actual samples, and high-efficiency removal (∼96%) of Al3+ from water systems, with sustainable recycling performance up to 10 times. Bifunctional membranes also played an important role in reducing the LOD of Al3+ to 16 nM through the preconcentration process. Therefore, this study is crucial to the development of environmentally sustainable strategy for monitoring and removing pollution. [Display omitted] • A pyrene-based ratiometric probe PYR was developed for Al3+ detection. • PYR exhibited excellent selectivity and sensitivity towards Al3+ with LOD of 0.33 μM. • A fluorescent cellulose membrane modified by PYR (PC membrane) has been constructed. • PC membrane realized simultaneous visual detection and efficient removal of Al3+. • PC membrane displayed more than 96% uptake efficiency and good reusability for Al3+. [ABSTRACT FROM AUTHOR]

Precise imaging identification of tumor tissues from normal tissues is still challenging. In this study, a new dual-locked near-infrared fluorescent probe BBQ650-SS-BTZHC-E was developed for the discrimination between cancer cells and normal cells. The probe consists of a hemicyanine fluorophore conjugated to an esterase substrate and a quencher connected via a disulfide bond. The esterase substrate blocks the excited state intramolecular proton transfer (ESIPT) process, while the quenching agent forms a Förster resonance energy transfer (FRET) pair with the fluorophore. The fluorescence activation is dependent on the presence of both esterase and glutathione (GSH), resulting in the "ESIPT on" and "FRET off" states, which represent an "AND" logic. The characterizations showed that the kinetics of fluorescence activation are dependent on the concentrations of the two activators with a high specificity. Fluorescent imaging experiments using BBQ650-SS-BTZHC-E successfully distinguished cancer cells (HeLa, 4T1, RAW264.7) from normal cells (HFL1) with high contrast and specificity, and imaged 4T1 tumor on live mice. This study provides a simple platform for the development of dual-locked fluorescent probes for bio-imaging applications. [Display omitted] • A new hemicyanine-derived NIR "AND" logical dual-locked fluorescent probe. • The activation of the fluorescence is based on ESIPT and FRET processes. • The probe distinguished cancer cells from normal cells with high imaging contrast and specificity. • This work represents a platform for dual-locked NIR probes that is easy to synthesize and modify. [ABSTRACT FROM AUTHOR]

Abstract: An iminofluorescein-Cu2+ ensemble probe was prepared for the detection of thiols in aqueous solution. In HEPES buffer, among various amino acids, only cysteine (Cys) induced fluorescence enhancement of Cu2+ ensemble. The mechanism was proposed that addition of Cys induced decomplexation of Cu2+ from weak-fluorescent ensemble, followed by hydrolytic cleavage of the resulted Schiff base to give a strongly fluorescent fluoresceinaldehyde. By fluorescence titration using 2μM iminofluorescein-Cu2+ ensemble probe, the detection limit for Cys was evaluated to be 9μM with a signal-to-noise ratio of 3. Furthermore, the confocal microscopy experiments demonstrated that this sensor was potential for the imaging of thiols in living cells. [Copyright &y& Elsevier]

Photoactivatable subcellular organelles imaging offers the desirable spatiotemporal resolution in studying the complex biological processes. Developing proper and simple photoremovable protecting groups (PPGs) is the key for constructing such imaging probes. In this study, we designed and synthesized three Sanger's reagent caged fluorescent probes for specific photoactivated organelle imaging. We showed the photoactivated fluorescence recovery of the probes. The photolysis mechanism was verified by mass spectra (MS) analysis, and the highly efficient photolysis process was monitored by high performance liquid chromatography (HPLC). The probes successfully imaged their respective targeted organelle, including mitochondria, lysosomes, and endoplasmic reticulum (ER), in a photoactivated manner, and exhibited high co-localization coefficients when compared to commercially available probes. Given the high reactivity and efficient photodissociation capability of Sanger's reagent with amino groups, our examples demonstrate the potential of Sanger's reagent as a novel general PPG for constructing photoactivatable fluorescent probes. • Sanger's reagent used as a new type of photocage to construct organelle probes. • The photolysis uniquely cleaves amide bond of the Sanger's reagent caged probes. • The caged probes display high photolysis efficiency and high organelle specificity. [ABSTRACT FROM AUTHOR]

Human serum albumin (HSA) is an important biomarker for chronic kidney disease, cardiovascular disease, and liver disease, yet its measurement is subject to the routine clinical laboratories. Pioneering studies have demonstrated that few of the ratiometric fluorescent probes enable the point-of-care (POC) testing of HSA with the aid of affordable domestic apparatuses. Still, the lack of choices of fluorophores restricts the development of such assay. In the present work, we propose two design strategies on the typical donor-acceptor fluorescent probe via the structural engineering. The results suggest that replacement of the dimethylamino group in probe by the weaker electron donating thiophene group can effectively tune the fluorescence response to HSA from off-on to ratiometric, ideally suiting for the POC application. The screened fluorescent probe is capable of detecting HSA with the features of fast response (< 10 s), stable output, high sensitivity (limit of detection = 54 nM), tunable detection range, and great anti-interference. Moreover, the ratiometric fluorescence response to HSA can be recorded and analyzed by the portable miniaturized paper-based or 3D-printed devices at the point of need. The success of structural engineering in the present study provides an efficient way to rationally regulate the fluorescence response mode of the donor-acceptor probes. [Display omitted] ● A donor-acceptor-based probe STF for ratiometric detection of HSA is reported. ● The relationship between structure and spectroscopic properties of probe is revealed. ● STF enables the rapid, sensitive, and selective detection of HSA. ● The portable paper-based testing devices and 3D-printed miniaturized devices are integrated. ● The point-of-care testing of HSA is achieved. [ABSTRACT FROM AUTHOR]

A ratiometric pyrene-based fluorescence sensor PN was developed for visual detection of formaldehyde (FA) by featuring homoallylamino group as specific recognition site. Sensor PN undergo a unique FA-triggered 2-aza-Cope rearrangement, which resulted in monomer-excimer conversion in a ratiometric manner accomplished with distinguishable fluorescent color change from blue to violet. Due to the advantage of high selectivity, fast response (< 100 s), low detection limit (18 μM), wide quantitative detection range (0.018–4 mM) and large ratio enhancement (up to 10-fold), PN has been successfully applied for detecting FA in diverse food samples. Notably, novel portable devices based on paper chip and alginate gel were constructed and realized visual quantitative detection of liquid and gaseous FA, as well as nondestructive monitoring volatile FA variation of real food samples during their shelf life, which were verified with the aid of chemometrics. Most importantly, sensor PN has been proven to be capable of fluorescence imaging of FA in living cells. Therefore, the impressive sensor PN is expected to provide advice and insights in the field of food safety and biological systems analysis. [Display omitted] • A ratiometric pyrene-based fluorescence sensor was developed. • The sensor was validated for analysis of endogenous FA in foods and living cells. • Paper/gel-based devices were designed for visual detection of liquid and gaseous FA. • Portable devices realized nondestructive monitoring volatile FA variation of foods. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A polydiacetylenes-based sensor for the efficient detection of phospholipase D activity has been developed. • The sensor showed clolour and fluorescence changes in the presence of PLD and L-α-phosphatidylcholine. • The paper-based PDAs sensor also demonstrated the ability of monitoring PLD activity. Abstract Phospholipase D (PLD), as an enzyme that catalyses the hydrolysis of L-α-phosphatidylcholine to produce phosphatidic acid, plays an important role in regulating biological processes. In this work, polydiacetylenes (PDAs) bearing imidazolium as head group are reported for the efficient detection of PLD activity. Owing to the strong interaction between negatively charged phosphatidic acid and positively charged imidazolium moieties of PDAs, the PDAs were found to produce a colour transition from blue to red, and an increase in fluorescence. No obvious changes to PDAs were observed when PLD was absent in the reaction, or when the activity of PLD was inhibited by halopemide. The colour and fluorescence changes of PDAs are attributed to the generation of phosphatidic acid in the PLD-catalysed reaction. Furthermore, a paper sensor based on PDAs was constructed and exhibited convenient and sensitive detection of PLD activity. [ABSTRACT FROM AUTHOR]

This paper describes the design and synthesis of a benzothiazole-based fluorescent probe ( H 1 ) for zinc and cadmium ion detection and discrimination, using cysteine as an auxiliary reagent. Among the various metal ions tested, zinc and cadmium ions induced blue-shifted emissions of probe H 1 from 573 nm to 520 nm and 540 nm, respectively. The addition of cysteine caused the emission of H 1 -Cd 2+ to red-shift back to 573 nm. In contrast, the emission of H 1 -Zn 2+ with the addition of cysteine only decreased without any red-shift of wavelength. Furthermore, confocal laser scanning micrographs of HeLa cells demonstrated satisfactory cell permeability of H 1 and selectivity toward zinc and cadmium ions in living cells. Test strip experiments suggest that probe H 1 can recognise zinc and cadmium ions together by a remarkable fluorescence change, thus providing a convenient method for tracking zinc and cadmium ions in biological systems. [ABSTRACT FROM AUTHOR]

Two novel fluorescent chemosensors based on the benzothiazole derivative were designed, synthesized, and used as a selective hydrazine sensor in a DMSO and HEPES buffer mixture (10 mM, pH 7.4)(9:1, v/v). The probes displayed high sensitivity and selectivity of hydrazine after adding more than 18 types of analyte. The application of the probes in detecting N 2 H 4 in living cells and in the gas state was also investigated. The single crystal X-ray study of the fluorescent sensor both before and after treatment with N 2 H 4 confirmed the proposed mechanism based on excited state intramolecular proton transfer (ESIPT). [ABSTRACT FROM AUTHOR]

l -Arginine ( l -Arg) and l -lysine ( l -Lys) are both essential amino acids and paly significant roles in human beings and other living organisms. Therefore, it is necessary to develop the feasible methods with high selectivity and sensitivity for the detection of l -Arg and l -Lys. Herein, aminopyrene modified diacetylene monomer (PCDA-PY) was prepared and incorporated into diacetylene monomer (PCDA) to form polydiacetylene (PDA) vesicles. With the assist of Mg 2+ , PDAs system underwent colorimetric and fluorescent changes upon the addition of l -Arg or l -Lys. The introduction of Mg 2+ and pyrene moiety makes PDAs system more sensitive toward l -Arg or l -Lys. Furthermore, an “OR AND” logic gate was constructed based on the optical changes of PDAs system with the three elements including Mg 2+ , l -Arg and l -Lys. [ABSTRACT FROM AUTHOR]

We have developed a ratiometric fluorescent probe for hypochlorite detection with high selectivity and sensitivity. The probe 1 can rapidly turn into an oxidized form accompanied by the fluorescence changes from yellow to blue only upon the addition of hypochlorite among various reactive oxygen species (ROS) and reactive nitrogen species (RNS). The limit of detection was calculated to be as low as 8.9 nM, which showed good sensitivity to hypochlorite. Furthermore, the confocal laser scanning micrographs of HeLa cells confirmed good cell permeability of probe 1 and its application to selective detecting hypochlorite in living cells. [ABSTRACT FROM AUTHOR]

Esterases are common (biological catalyst) that play an essential role in regulating the physiological processes of organisms, in addition to contributing to disease prevention. Herein, we report the design and synthesis of an esterase-activated chemiluminescent probe (CL-EA) for the selective detection of esterases. Using the 1,2-dioxetane scaffold as the chemiluminescent platform and acetoxymethyl ether as the recognition group, the present probe was successfully lighted in the presence of esterases. As a result, a strong chemiluminescent signal was generated in an aqueous solution, thereby allowing the highly sensitive and specific detection of esterases. Furthermore, the probe is used to screen the activity of three plastic-degrading enzymes and image esterases in live cells and in a mouse model. [Display omitted] • A chemiluminescent probe for detection of esterases activity is developed. • The probe is used to screen the activity of three plastic-degrading enzymes. • The probe is applied to imaging of esterases in living cells and in vivo. [ABSTRACT FROM AUTHOR]

A new dinuclear-copper(II) complex ( Cu-L 2 ) with two ammonium arms based on bis-2-((pyridin-2-ylmethylamino)methyl)phenol as the coordinated unit was synthesized. The complex exhibited high affinity with pyrophosphate (PPi) in aqueous solution. Using pyrocatechol violet (PV) as a colorimetric indicator, the indicator displacement assay (IDA) was carried out to determine the binding constant between the complex and PPi. A ca. 784-fold enhancement was founded when compared Cu-L 2 to ammonium-free counterpart ( Cu-L 1 ) . The new dinuclear complex was successfully used to monitor the hydrolysis of PPi catalyzed by pyrophosphatase (PPase). Furthermore, by employing esculetine as a fluorescent indicator, the complex was also used to detect PPi released during polymerase chain reaction (PCR). [ABSTRACT FROM AUTHOR]

We reported a novel ECL immunosensor for detection of carcinoembryonic antigen (CEA) based on the reduced graphene Oxide-BaYF 5 :Yb, Er (rGO-BaYF 5 :Yb, Er) nanocomposites. The rGO-BaYF 5 :Yb, Er nanocomposites, used as electrode luminescence materials, were prepared by in situ hydrothermal method, and characterized by TEM, XRD, UV–vis spectra, and upconversion fluorescence spectra. Further, poly (diallyldimethylammonium chloride) (PDDA), Au nanoparticles (AuNPs), and Anti-CEA were successively assembled on the surface of rGO-BaYF 5 :Yb, Er nanocomposites modified-electrode for fabricating ECL immunosensor. The results of the ECL measurements of CEA indicated that this novel ECL immunosensor exhibited high sensitive response to CEA in a linear range of 0.001–80 ng mL −1 with a low detection limit of 0.87 pg mL −1 , good selectivity and satisfactory stability. [ABSTRACT FROM AUTHOR]

Biological thiols are crucial in biological processes. Therefore, a probe capable of targeting and imaging biothiols in living cells, as well as rapidly labelling the thiols in proteins, is desirable and imperative. Herein, we designed and synthesized FRB-T containing α , β -unsaturated ketones to recognize thiols for detecting biothiols and selectively labelling the sulfhydryl-containing proteins. The probe initially exhibited weak fluorescence and then performed 1, 4-Michael addition reaction between its α , β -unsaturated ketone and thiols, along with the spiro ring-opening, leading to remarkable fluorescence enhancement and colour changes. The specificity of FRB-T towards thiols was high, and its detection limits were 70 nM for cysteine (Cys) and 1.51 μg/mL for ovalbumin (OVA). Furthermore, FRB-T has also been successfully applied to biothiols imaging in Hela cells, and rapid labelling of the sulfhydryl-containing proteins without washing step. [Display omitted] • A biothiol-specific probe with strong fluorescence enhancement and colorimetric response. • The probe owns low LOD of 70 nM and 1.51 μg/mL for Cys and OVA respectively. • A new type of reagent for labelling sulfhydryl-containing proteins without washing. [ABSTRACT FROM AUTHOR]

Mercury is a highly hazardous and widespread heavy metal and can cause many severe health problems such as kidney failure, central nervous system damage with various cognitive and motor disorders, and even death. Efficient approach for the detection of mercury ion is very significant. In this work, a colorimetric and ratiometric fluorescent probe based on 4-chloro-7-nitrobenzo-2,1,3-oxadiazole (NBD-Cl) is developed by employing a photo-induced electron transfer mechanism. Furthermore, we were fortunate enough to obtain the single crystal structures before and after binding with Hg 2+ , which displays that two nitrogen atoms on amino and morpholine groups participate in the coordination and form a complex with a ratio of 2:2. And this probe displays a highly selective response to mercury (II) ions in an aqueous solution and possesses a distinguished capability for lysosome-targeting detection of Hg 2+ without interferences in living cells. The results suggest that Hg 2+ -selective probe has good water-solubility, biocompatibility and cell-penetrability and can serve as an efficient tool for probing cellular toxicological actions that are related to Hg 2+ . [ABSTRACT FROM AUTHOR]

Electrochemiluminescence (ECL) property of nitroolefin-based fluorescein was investigated and reported for the first time. Its ECL behaviors in acetonitrile (CH 3 CN) system and aqueous system were studied, respectively. Results indicated that nitroolefin-based fluorescein showed reversible reduction peaks on cycling voltammetric (CV) spectrum and produced ECL emission with the presence of benzoyl peroxide (BPO) as a coreactant in CH 3 CN solution. Reduction potential peaks of the substance can be observed in water solution in CV, and the intensity of ECL emission is much lower in water than that of in CH 3 CN solution. However, the ECL property of nitroolefin-based fluorescein can be used for the detection of cysteine (Cys) by using potassium persulfate (K 2 S 2 O 8 ) as coreactant in aqueous solution. Under optimum conditions, the ECL intensity has a linear relationship with the concentration of cysteine in the range of 10 −9 to 10 −8 mol L −1 and a detection limit of 4.2 × 10 −10 mol L −1 . It has a lower detection limit than the fluorescence method. Our investigation demonstrated that the proposed method provides an elegant platform for fabrication of new generation of biosensors with ultrahighsensitivity, and might have potentially broad applications in amino acids diagnostics and bioassay. [ABSTRACT FROM AUTHOR]

A new fluorescein-based fluorescent probe for the detection of Au 3+ has been developed. This probe was derived from 4′,5′-fluoresceindicarboxaldehyde and exhibited highly selective and sensitive response toward gold(III) ions in aqueous solution. There is a good linear relationship between the fluorescence intensity at 523 nm and the concentrations of Au 3+ ranging from 0 μM to 60 μM, which makes it effective for the detection of Au 3+ . The limit of detection (LOD) was evaluated to be 0.07 μM based on S/N = 3. The fluorescence enhancement was attributed to the irreversible C N bond hydrolysis that occurred to this probe in the presence of Au 3+ , generating the fluorescent 4′,5′-fluoresceindicarboxaldehyde. Furthermore, the imaging experiments indicated that this probe is cell-permeable and can be used to detect Au 3+ within living cell. [ABSTRACT FROM AUTHOR]

Abstract: A new fluorescent probe based on fluorescein fluorophore displays an excellent selectivity and sensitivity for GSH in buffer solution containing CTAB. The fluorescence intensity of sensor is linearly proportional to GSH concentrations ranging from 0 to 10μM, and as low as 22nM concentration of GSH was evaluated with 3.3 σ/s. The optical changes are attributed to the release of free fluorescein after the electron withdrawing dinitrophenyl ether reacted efficiently with GSH in CTAB micelles. The enhanced selectivity toward GSH over Cys and Hcy considered to be related to the carboxyl groups in thiols. The confocal microscopy experiments implied that this probe is a promising candidate for imaging of GSH in living cells. [Copyright &y& Elsevier]

Abstract: A quinoline-based fluorescent chemosensor was reported for the simultaneous detection of Zn2+ and Cd2+ in aqueous solution. In HEPES buffer, among various metal ions, only Zn2+ and Cd2+ exhibited fluorescence enhancement at 497nm accompanied by the red-shift emission wavelength. The mechanism was proposed that internal charge transfer effect induced by binding with Zn2+ or Cd2+ produced the fluorescence changes. With the addition of cysteine, the fluorescent solution containing sensor and Cd2+ show the decreased fluorescence at 497nm and the increased fluorescence at 420nm, which was attributed to the dissociation of the complex formed by sensor and Cd2+. In contrast, the fluorescence of solution containing sensor and Zn2+ is unchanged with the addition of Cys. Furthermore, the confocal microscopy experiments indicated that this sensor can provide real-time detection for intracellular Zn2+ and Cd2+. [Copyright &y& Elsevier]

Carbon monoxide (CO) is a colorless and odorless gas often used as a fuel and as an important raw material for the synthesis of basic organic compounds in the chemical industry. CO affects respiration and organ coordination in organisms, and is fatal at high concentration. Due to the wide range of industrial applications and biological effects of CO, its research has received considerable attention from researchers. In this study, we designed and synthesized a chemiluminescent sensor CL-CO, which can recognize CO in the presence of palladium chloride (PdCl 2), based on the Schaap's adamantylidene-dioxetane system and allyl ether as the recognition site. In both liquid and solid states, CL-CO can recognize CO gas with high sensitivity and selectivity. This work provides a convenient tool for studying CO gas, and a new application for exploring the adamantylidene-dioxetane system. [Display omitted] • A new chemiluminescence probe for detecting CO was designed. • The probe has very high sensitivity and selectivity for CO released from CORM-3 solution and CO gas. • Whether probe is liquid or solid, it can recognize CO gas. • The detection of gas by chemiluminescence probe is realized in a new way. [ABSTRACT FROM AUTHOR]

• Hydrogel microsphere sensor is fabricated by self-assembly method using microfluidic chip. • The sensor exhibits high sensitivity for Al3+ and Hg2+ with a detection limit of 70 nM and 120 nM, respectively. • The hydrogel microsphere sensor are reusable. • The hydrogel microsphere sensor has been successfully applied to the detection of real samples. Traditional fluorescent sensors for simultaneous detection of metal ions require the use of specially designed fluorescent probes. In this manuscript, we have employed a new strategy for the design of a sensor for simultaneous detection of metal ions that is based on a fluorescent probe encapsulated hydrogel matrix. An investigation designed to assess this strategy led to the development of a novel dual fluorescent encapsulated hydrogel microsphere sensor for sensitive and simultaneous detection of Al3+ and Hg2+. The hyperbranched poly (poly (ethylene glycol) diacrylate) (HB-PEGDA) and thiolated sodium alginate (SA-SH) composite hydrogel microspheres used to construct the sensor, which contain two fluorescent probes encapsulated in a highly dense manner, were prepared by using a self-assembly method in conjunction with a microfluidic device. The functionalized hydrogel microspheres were shown to exhibit high selectivity for Al3+ and Hg2+ among various metal ions with a detection limit of 70 nM and 120 nM, respectively. In addition, the hydrogel microspheres can be readily separated from test samples and utilized for repeated use by removing Al3+ and Hg2+ by addition of a solution containing EDTA and KI. Compared with previously devised sensors, the new HB-PEGDA/SA-SH composite hydrogel microspheres containing two encapsulated fluorescent probes are readily prepared and effective for simultaneous detection of two different metal ions. [ABSTRACT FROM AUTHOR]

• A dioxetane-based chemiluminescent probe for the efficient detection of fluoride ions in vitro and in vivo has been developed. • The dioxetane-based chemiluminescent probe holds superior efficiency for sensing fluoride ions in aqueous environment. • The probe was successfully applied in quantifying fluoride ions in toothpaste and in vivo imaging in living mice. Fluoride plays an important role in our daily life as it associates with a variety of biological and pathological processes. Hence, an analytic method that can detect fluoride ions under physiological conditions with high sensitivity and specificity, and fast response, is needed. Herein, we introduced a dioxetane-based chemiluminescent probe, CL-F, specifically designed for the detection of fluoride ions in physiological environment. The probe CL-F emitted strong green chemiluminescent light within 1 min when incubating with fluoride ions specifically. The linear range for sensing fluoride ions and limit of detection were determined to be 0–30 μM and 0.91 μM, respectively. The probe CL-F was then successfully applied in quantifying fluoride ions in toothpaste and in vivo imaging in living mice, demonstrating CL-F as a promising tool for sensing fluoride ion in vitro and in vivo. [ABSTRACT FROM AUTHOR]

• A novel method based on an indicator of copper reaction for tracing Cys oxidation process was developed. • The fluorescence alteration mechanism during Cu2+-catalyzed oxidation of cysteine was analyzed. • The different fluorescence alteration trajectories can be applied to discriminate Cys, GSH and Hcy. Using cyanine dye-coupling 2-pyridylmethyl chelating unit as fluorescent probe, we successfully developed an indicator of copper clock reaction to monitor the process of cysteine (Cys) oxidation. During the monitoring assay, the fluorescent changes reflected three sequential reaction and binding behaviors including oxidation of Cys, oxidation of Cu(I) and binding between Cu(II) and the oxidation product cystine (Cys-Cys). Because the different kinetic trajectories were obtained when used Cys, GSH and Hcy as the substrates, respectively, a new strategy for distinguishing Cys from GSH and Hcy was further developed using the cyanine dye-coupling Cu(II) complex. [ABSTRACT FROM AUTHOR]