Selective Detection Method Research Articles

Barcode signal amplifying strategy for sensitive and accurate protein detection on LC-MS/MS.

Protein drugs showing strong pharmaceutical activity, high specificity, and low toxicity and side effects have drawn extensive attention in the field of life sciences and medicine. Precise evaluation of the function of these drugs requires accurate and sensitive detection methods. Here, we report a novel chromatography-tandem mass spectrometry (LC-MS/MS) method for sensitive and selective detection of protein drugs. Magnetic nanoparticles (Apt29@MNPs) were functionalized by thrombin aptamers, and quantum dots (Apt15@ss@QDs) were dual-functionalized with quantitative thrombin aptamers and small molecules with high ionization efficiency as the mass barcode. After Apt29@MNPs specifically purify and enrich thrombin from biological samples, they can form a nano "sandwich structure" when Apt15@ss@QDs are added, resulting in the release of the mass barcode for LC-MS/MS analysis via the cutting of the disulfide bond. Since there is a higher quantitative molecular ratio of mass barcode to thrombin in the nano-"sandwich structure", quantitative detection of thrombin with high sensitivity and selectivity can be achieved via the LC-MS/MS detection of the mass barcode with high ionization efficiency rather than thrombin, which effectively avoids the disadvantages of direct protein detection by mass spectrometry. The established method for thrombin detection shows a good linear relationship in a concentration range of 0.00115-1.15 nM with a limit of detection (LOD) of 0.0007 nM. The present work provides a new approach for the effective and sensitive quantitative analysis of protein drugs and would be of great significance in promoting the development of protein drugs and clinical applications.

Cuttlefish ink-based N and S co-doped carbon quantum dots as a fluorescent sensor for highly sensitive and selective para-nitrophenol detection.

Para-nitrophenol (PNP) is an important raw material for organic synthesis and its extensive use has produced a series of environmental problems. Here, we develop a highly sensitive and selective fluorescent detection method for PNP with cuttlefish ink-based carbon quantum dots (CQDs). The cuttlefish ink, which is rich in eumelanin, is utilized as the only precursor to synthesize the CQDs via a one-step hydrothermal method. The resultant CQDs were co-doped with nitrogen and sulfur and exhibited excellent fluorescence properties. Two optimal emissions can be observed at the excitation/emission wavelengths of 320/385 nm and 390/465 nm, respectively. In the presence of PNP, the two emissions are remarkably quenched. PNP can be measured in the linear detection concentration range of 1.25-50 μM (Em = 385 nm and R2 = 0.9884) or 1.25-27.5 μM (Em = 465 nm and R2 = 0.9818) with a detection limit of 0.05 μM. Significantly, it is found that a much wider linear detection range of 0.05-125 μM with a lower detection limit of 0.039 μM (3σ/k) can be achieved when log(I385 nm + I465 nm) was utilized to quantify PNP. The investigations of the sensing mechanism suggested that the inner filter effect and photoinduced electron transfer of PNP and N,S-CQDs leads to fluorescence quenching. The sensing method is successfully applied for PNP detection in real water samples with satisfactory recoveries (91.18-103.14%). A new sustainable waste-prevention strategy of cuttlefish ink and a feasible alternative to PNP detection methods is provided in this article.

In situ creation of ZnO@CdS nanoflowers on ITO electrodes for sensitive photoelectrochemical detection of copper ions in blood.

A highly selective and sensitive photoelectrochemical (PEC) detection method has been developed for the analysis of copper (Cu2+) ions using nanoflower-like ZnO@CdS heterojunctions, of which ZnO was first in situ grown onto the indium tin oxide electrodes by a hydrothermal method and then coated with CdS through the chemical bath deposition route. It was discovered that the ZnO@CdS heterojunction so formed could serve as a photosensitive catalyst with improved charge separation for visible-light-driven PEC responses. Enhanced visible-light harvesting of nanocomposites could also be expected with CdS as the visible-light sensitizer. Furthermore, the introduction of Cu2+ ions could cause a rational decrease in the photocurrents of nanocomposites through the specific interaction between CdS and Cu2+ ions. A ZnO@CdS heterojunction-based PEC sensor was thereby developed for the detection of Cu2+ ions in blood in the linear concentrations ranging from 0.50 to 80 nM, with a limit of detection of 0.18 nM. Such a heterojunction-based PEC detection platform constructed using two photocatalytic materials with matched band structures are promising for a wide range of applications for sensing Cu2+ ions in clinical diagnostics, food monitoring, and environmental analysis.

Screening method of mildronate and over 300 doping agents by reversed-phase liquid chromatography-high resolution mass spectrometry

Considering the huge amount of substances associated with athletic performance improvement, current doping control analysis requires a comprehensive screening method, which leads to the detection of prohibited substances of different physico-chemical properties. This comprehensiveness associated with instrumental approaches based on high resolution mass spectrometry has allowed the development of extremely sensitive and selective detection methods. Furthermore, it is desirable the method to be simple, fast and straightforward. Mildronate is a highly polar quaternary amine, classified as metabolic modulator by the World Anti-Doping Agency (WADA). The inclusion of mildronate in the screening strategy is a challenge considering its singular physicochemical properties, compared to numerous doping agents of low and medium polarity. For this purpose, a method combining solid-phase extraction (SPE) and dilute-and-shoot approach has been developed and validated, allowing the detection of mildronate and other 332 prohibited substances. In the sample preparation protocol, the enzymatic deconjugation step and SPE conditions were stressed to enable the recovery of mildronate without jeopardizing the detection of other doping agents. The C18/18% SPE cartridge without any type of ionic interaction, associated with the dilute-and-shoot approach proved to be effective for all monitored substances. The instrumental method employed was based on liquid chromatography using a reversed-phase column in a 12-minute gradient coupled to a high-resolution mass spectrometry in full scan with positive and negative switching and fragmentation in the positive mode, for the most critical detection compounds. The performance of the method was evaluated regarding selectivity, precision, recovery, carry-over, limit of detection and stability, following the recommendations of WADA.

LC-MS/MS Quantification of Nevirapine and Its Metabolites in Hair for Assessing Long-Term Adherence.

The adherence assessment based on the combination of nevirapine (NVP) and its two metabolites (2-hydroxynevirapine and 3-hydroxynevirapine) would more comprehensively and accurately reflect long-term adherence than that of a single prototype. This study aimed to develop a specific, sensitive and selective method for simultaneous detection of the three compounds in hair and explore whether there was consistency among the three compounds in assessing long-term adherence. Furthermore, 75 HIV-positive patients who were taking the NVP drug were randomly recruited and divided into two groups (high-and low-adherence group). All participants self-reported their days of oral drug administration per month and provided their hair strands closest to the scalp at the region of posterior vertex. The concentrations of three compounds in the hair were determined using a developed LC-MS/MS method in multiple reaction monitoring. This method showed good performances in limit of quantification and accuracy with the recoveries from 85 to 115% and in precision with the intra-day and inter-day coefficients of variation within 15% for the three compounds. The population analysis revealed that patients with high-adherence showed significantly higher concentrations than those with low-adherence for all three compounds. There were significantly moderate correlations of nevirapine with 2-hydroxynevirapine and 3-hydroxynevirapin and high correlation between 2-hydroxynevirapine and 3-hydroxynevirapin. The two NVP’s metabolites showed high consistency with NVP in evaluating long-term adherence.

Paper-based upconversion fluorescence aptasensor for the quantitative detection of immunoglobulin E in human serum

Immunoglobulin E (IgE), a biomarker of allergic diseases, plays a critical role in allergic mechanism. Because of its low abundance in serum, the demand of developing sensitive, selective and simple methods for IgE detection is still very urgent. Paper-based analytical devices using upconversion nanoparticles (UCNPs) as the label can be promising point-of-care test (POCT) methods in rapid diagnosis, owing to their NIR-excitation and visible light emission nature, which can avoid the interference of autofluorescence and scattering light from biological samples and paper substrates. In this work, we proposed a paper-based analytical device for the sensitive, selective and accurate detection of total immunoglobulin E (IgE) in human serum. The assay was based on resonance energy transfer between UCNPs and organic dye tetramethylrhodamine (TAMRA), and IgE aptamer with stem-loop structure was used as the recognizing probe. The existence of IgE change the conformation of IgE aptamer, enlarge the distance between donor and acceptor, and block the energy transfer process. Thus, the luminescence of UCNPs recovered with an IgE concentration independent manner. A linear calibration was obtained in the range of 0.5–50 IU/mL, with a detection limit of 0.13 IU/mL. The results of our method were well correlated with that of commercial ELISA kit (20 human serum samples). This work suggests promising prospect of the paper-based UC-LRET analytical devices in real samples and may promote the application of paper-based analytical devices in clinical diagnosis.

A smartphone-integrated method for visual detection of tetracycline

• A multi-color fluorescence nanosensor based on Lap was manufactured. • It can realize the detection of tetracycline from 30 nM to 54 μM. • It was highly desirable for fulfilling the requirement for food quality. • Tetracycline can be recognized by chromaticity analysis APP on the smartphone. • It provided the possibility for the application in the field of intelligent devices. The emergence of “superbugs”, which can cause great panic, has been proved to be related to the pollution of antibiotics in the environment water and food. It is of great research value to develop a portable, on-site and simple method for sensitive and selective detection of antibiotics. In this work, a laponite-based dual-channel fluorescent nanoprobe for the detection of tetracycline (TC) was manufactured through a simple assembly process. The nanoprobe can detect TC within two concentration channel from as low as 30 nM up to 54 μM with a detection limit of 9.5 nM, which met the needs in various analytical samples and showed excellent selectivity over various interferers. More significantly, the paper-based and glove-based visual probes were devised for the detection of TC by multi-color fluorescence change. And the tetracycline was also measured in milk, honey and lake after post-treatment of the samples. Combined with smartphone chromaticity analysis application (APP), the portable and disposable detection of TC can be realized. In addition, according to the fluorescence color change of the probe corresponding to the concentration of TC, two logic gates were also designed, which provided the possibility for the application of the probe in the field of smart devices.

Novel Platinum(II) Complex-based Luminescent Probe for Detection of Hypochlorite in Cancer Cells.

Hypochlorite (ClO⁻) is of great importance either for the metabolism of living organisms or as disinfectant in daily life. However, improper concentration levels of ClO⁻ lead to serious health problems including erythrocyte damage, cardiovascular problems, neuron degeneration, lung/kidney injury and cancer. Therefore, a sensitive and selective detection method is required for the visualization and measurement of ClO⁻. In this work, a novel platinum(II) complex-based luminescent probe Pt-CHO was synthesized and utilized to detect ClO⁻. This "turn-off" probe exhibits high sensitivity, excellent selectivity, good pH stability, low limit of detection and instantaneous response ability. Moreover, the luminescent response is caused by the oxidation of aldehyde into carboxyl groups combined with the coordination of hydroxyl groups at the Pt center, which is rarely reported. The cell imaging of HeLa cells proved the considerable potential of the probe for ClO⁻ imaging in living cells.

Voltammetric determination of ethinylestradiol using screen-printed electrode modified with functionalized graphene, graphene quantum dots and magnetic nanoparticles coated with molecularly imprinted polymers

The present work reports the development of a sensitive and selective method for ethinylestradiol detection using screen-printed electrode (SPE) modified with functionalized graphene (FG), graphene quantum dots (GQDs) and magnetic nanoparticles coated with molecularly imprinted polymers (mag@MIP). The performance of the mag@MIP sensor was compared with that of a non-molecularly imprinted sensor (mag@NIP). Chemical and physical characterizations of the mag@NIP and mag@MIP sensors were performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Brunauer-Emmett-Teller (BET) techniques. The electrochemical behavior of the electrodes investigated, which included (mag@MIP)-GQDs-FG-NF/SPE, (mag@NIP)-GQDs-FG-NF/SPE, GQDs-FG-NF/SPE and FG-NF/SPE, was evaluated by cyclic voltammetry. The results obtained show a significant increase in peak current magnitude for (mag@MIP)-GQDs-FG-NF/SPE. Using square wave voltammetry experiments, the efficiency of the (mag@MIP)-GQDs-FG-NF/SPE sensor was also tested under optimized conditions. The linear response range obtained for ethinylestradiol concentration was 10 nmol L−1 to 2.5 μmol L−1, with limit of detection of 2.6 nmol L−1. The analytical signal of the (mag@MIP)-GQDs-FG-NF/SPE sensor suffered no interference from different compounds and the sensor exhibited good repeatability. The proposed sensor was successfully applied for ethynilestradiol detection in river water, serum and urine samples, where recovery rates between 96 to 105% and 97–104% were obtained for environmental and biological samples, respectively.

Facile synthesis of CuS nanoparticles on two-dimensional nanosheets as efficient artificial nanozyme for detection of Ibuprofen in water

This work reports a selective and sensitive method for detection of Ibuprofen (Ibu), a nonsteroidal anti-inflammatory drug (NSAID) based on the peroxidase mimic activity of CuS nanoparticles (NPs) decorated on 2D graphitic carbon nitride (g-C3N4) and hexagonal boron nitride nanosheets (h-BN). CuS/g-C3N4 and CuS/h-BN nanocomposites are synthesized by simple hydrothermal technique and characterized by different sophisticated analytical techniques like XRD, BET, HRTEM and XPS analysis. The surface charge of the nanocomposites is determined by zeta potential analysis. The peroxidase mimic activity of the nanocomposites are analyzed by carry out the catalytic oxidation of 3, 3ʹ, 5, 5ʹ-tetramethylbenzidine (TMB) in presence of H2O2 to produce a blue colored oxidized product (oxTMB). The synthesized nanocomposites are employed for the colorimetric detection of Ibu a model pharmaceutical pollutant in an aqueous medium. Ibu is commonly used by human beings to cure certain ailments and excreted in environmental wastewaters that have several bad effects. The principle of sensing is the inhibition of the peroxidase mimic activity of the nanozymes by Ibu. The detection limit of Ibu achieved in the colorimetric detection technique is found to be 16.01 and 21.20 mg/L (ppm) within the linear range of 0−100 mg/L in presence of CuS/g-C3N4 and CuS/h-BN nanocomposites, respectively. The practical application of the proposed sensor is successfully demonstrated using various environmental water samples spiked with different concentrations of Ibu. The proposed sensing probes exhibit high specificity and anti-interfering ability over other water contaminates and considerable feasibility in real water systems.

A portable selective electrochemical sensor amplified with Fe3O4@Au-cysteamine-thymine acetic acid as conductive mediator for determination of mercuric ion

Mercury ion (Hg2+) is considered to be one of the most toxic heavy metal ions and can cause adverse effects on kidney function, the central nervous system, and the immune system. Therefore, it is important to develop a fast and simple method for sensitive and selective detection of Hg2+ in the environment. This research proposes a portable electrochemical sensor for rapid and selective detection of Hg2+. The sensor platform is designed based on thymine acetic acid anchored with cysteamine-conjugated core shell Fe3O4@Au nanoparticles (Fe3O4@Au/CA/T-COOH) immobilized on a sensing area of a screen-printed carbon electrode (SPCE) with the aid of an external magnetic field embedded in a homemade electrode holder for ease of handling. In the presence of Hg2+, the immobilized thymine combines specifically with Hg2+ and forms a thymine-Hg2+-thymine mismatch (T-Hg2+-T). The resulting amount of Hg2+ was determined by differential pulse anodic stripping voltammetry (DPASV). Under optimal conditions, the sensor exhibited two wide linearities in a range from 1 to 200 μg L−1 and 200–2200 μg L−1 with the reliability coefficient of determination of 0.997 and 0.999, respectively. The detection limit (LOD) and the quantification limit (LOQ) were also determined to be 0.5 μg L−1 and 1.0 μg L−1, respectively. The sensor was further applied for determination of Hg2+ in water samples, a certified reference material and fish samples. The results were compared with flow injection atomic spectroscopy-inductively coupled plasma-optical emission spectroscopy (FIAS-ICP-OES) systems as a reference method. Results obtained with the proposed sensor were relatively satisfactory, and they showed no significant differences at a 95% confidence level by t-test from the standard method. Therefore, considering its fast and simple advantages, this novel strategy provides a potential platform for construction of a Hg2+ electrochemical sensor.

An exceptionally intense turn-on fluorescence sensor in the far-red region for common milk allergen, β-lactoglobulin

Common milk allergens, such as, β-lactoglobulin (β-LG), poses a major health concern for public, particularly in children. Thus, sensitive and selective methods for detection of common milk allergens are highly warranted. To the best of our knowledge, detection and quantification of β-lactoglobulin, a common milk allergen, by fluorescence based technique has not been reported till date. Herein, we present the first ever fluorescence based report for the selective detection and quantification of milk allergen, β-LG, using LDS-798 as a fluorogenic probe, which registers an exceptionally large fluorescence enhancement of ∼2900 fold in the far-red region upon binding with β-LG with LOD of ∼6.3 (±0.3) nM for β-LG in aqueous buffer solution and 0.67 (±0.04) μM in 5% bovine milk matrix respectively. High sensitivity and selectivity, fast response, high repeatability and reproducibility, easy operation, along with emission in the technologically advantageous far-red region make the fluorometric quantification of β-LG, using LDS-798 as a fluorogenic probe, far more advantageous than the other techniques, generally used for β-LG quantification. Importantly, we have demonstrated the applicability of this probe for quantification of β-LG in real milk samples which has been validated by an established method.

Selective Nonenzymatic Amperometric Detection of Lactic Acid in Human Sweat Utilizing a Multi-Walled Carbon Nanotube (MWCNT)-Polypyrrole Core-Shell Nanowire.

Lactic acid plays an important role as a biochemical indicator for sports medicine and clinical diagnosis. The detection of lactic acid in sweat is a promising technique without any intrusive inconvenience or risk of infection. In this study, we present a selective nonenzymatic amperometric detection method for lactic acid in human sweat utilizing a multi-wall carbon nanotube (MWCNT)-polypyrrole core-shell nanowire. Because polypyrrole is a p-type conducting polymer, onto which anions are exclusively doped, leading to charge transfer, it offers selective detection for lactate anions at a specific potential, while being inert to the neutral and cationic species contained in human sweat. A chronoamperometric study reveals good sensing performance for lactic acid with a high sensitivity of 2.9 μA mM−1 cm−2 and detection limit of 51 μM. Furthermore, the MWCNT-polypyrrole nanowire exhibits excellent selectivity for lactic acid over interfering species, such as sodium chloride, glucose, urea, and riboflavin, which coexist with lactic acid in sweat. Finally, a nonenzymatic amperometric sensor for the selective detection of lactic acid in human sweat is demonstrated on commercial flexible electrodes. The results demonstrate the potential applications of the MWCNT-polypyrrole core-shell nanowire as a nonenzymatic amperometric lactate sensor.

Determination of 2-chloroethylphosphonic acid and its intermediate vinylphosphonic acid from artificially ripened sapota fruit by modified dispersive solid-phase extraction cleanup and gas chromatography/mass spectrometry analysis.

Fruit is generally ripened after harvesting using artificial ripeners such as ethylene, calcium carbide, and ethephon (2-chloroethylphosphonic acid), which can release some residues into the fruits. These residues must be within the maximum levels described in various international standards. The presence of the residues of artificial ripeners must be verified using sensitive and selective detection methods. The residues of ethephon and vinylphosphonic acid (VPA) were extracted from the pulp of sapota fruit using acetone, and the extract was treated with MgSO4 to remove residual water. The extract was subjected to dispersive solid-phase extraction cleanup using DSC-6S sorbent and graphitized carbon black mix, and the cleaned sample was evaporated to dryness and reconstituted in ether containing diazomethane. The analytes were quantitatively identified using gas chromatography/mass spectrometry. The developed method was observed to be linear in the concentration range of 1-5000 ng/g, and the limits of detection and quantification of the method were 1 and 2 ng/g, respectively, for both ethephon and VPA residues. The inter-day and intra-day precision was below 15%. The developed method was used for the quantification of ethephon residues from sapota fruit ripened with 100, 200, 500, 1000, 5000, and 10 000 mg/L solutions of ethephon, and ethephon residues were detected in the pulp samples up to a concentration of 5 ng/g. VPA residues were not detected in the fruit pulp; however, the washing solution of fruit ripened with a 10 000 mg/L ethephon solution showed VPA residues. The validated method exhibited high sensitivity for the analytes with a limit of quantification of 2 ng/g, which is lower than the described maximum residue level of 0-5 μg/g. The ethephon residues were below the maximum residue limits in the pulp of sapota fruit ripened with ethephon solutions up to 10 000 mg/L concentration.

Nitrosonaphthol reaction-assisted SERS assay for selective determination of 5-hydroxyindole-3-acetic acid in human urine

Urinary 5-hydroxyindole-3-acetic acid (5-HIAA) is a marker for diagnosis of patients with carcinoid tumors. In clinical practice, a simple colorimetric assay has widely been utilized for urinary 5-HIAA via its reaction with 1-nitroso-2-naphthol (NNa) in nitrous acid medium. However, this colorimetric assay has been criticized for lack of specificity. Herein, we proposed a novel SERS-based method for selective detection of urinary 5-HIAA by the use of a modified nitrosonaphthol reaction, in which hydrochloric acid is substituted for nitric acid to control the reaction conditions. This slight modification is crucial to be able to detect the cationic products in the acidic reaction mixture, because the chloride-aggregated Ag colloids not only create enormous hot spots for SERS enhancement, but also improve the chemical stability of nanostructured Ag substrates in acidic environment. Under optimized conditions, the present method can detect 5-HIAA within 12 min at concentrations as low as 1.2 ng/mL, which is 1000 times lower than that of conventional colorimetric method. And more importantly, the present method exhibits specific response toward 5-HIAA against other metabolites with similar structures in the urine. The relative standard deviation (RSD) of the present method is less than 5%, suggesting the acceptable reproducibility. The recoveries ranging from 89.6% to 106.3% were obtained for spiked human urine samples with RSD of 3.7–4.9%. Furthermore, several healthy person’s urine samples were also analyzed using the present method, and experimental results are in compliance with the levels recorded in a healthy population. On the basis of these results we can conclude that the present SERS-based method can provide a valuable alternative to conventional colorimetric assay for clinical diagnosis, evaluating prognosis, and monitoring of treatment in carcinoid tumors.

Rapid colorimetric detection of arsenic (III) by glutathione functionalized gold nanoparticles based on RGB extracting system

A sensitive and selective method for the colorimetric detection of arsenic (AsIII) ions has been demonstrated using glutathione functionalized gold nanoparticles (GSH-AuNPs). When arsenic ions are added to the GSH-AuNPs solution, the binding of arsenic ions with GSH ligands induces the aggregation of AuNPs, resulting in a rapid color change of the solution. With the implementation of a home-developed RGB extracting software, excellent linear correlation has been established between the calculated RGB color values and the arsenic concentrations (R2 = 0.99488). The limit of detection (LOD) of arsenic ions is as low as 0.12 ppb. More significantly, the GSH-AuNPs solution shows excellent detection selectivity to other metal ions (Fe3+, Co2+, Ni2+, K+, Na+, Mg2+, Ca2+, Cu2+, Hg2+, and Pb2+). This method could be applied to on-site and real-time fast detection of low level arsenic ions.

A polymerase chain reaction based lateral flow test strip with propidium monoazide for detection of viable Vibrio parahaemolyticus in codfish

Vibrio parahaemolyticus is one of the most important foodborne pathogens that cause various life-threatening diseases in human and animals. A selective method for detection of viable V. parahaemolyticus in codfish was created by combining propidium monoazide Polymerase Chain Reaction, and nucleic acid lateral-flow test strip. The VP1332 gene of V. parahaemolyticus was used as the detection target in PCR, and the 5′-end of the primers were labeled with biotin and digoxygenin, respectively. The PMA-PCR-LFS assay was further applied for detection of viable V. parahaemolyticus cells in codfish. The results showed that the PCR assay exhibited superior specificity (100%) on 70V. parahaemolyticus strains and 37 non-V. parahaemolyticus strains examined in the inclusivity and exclusivity tests; and the limit of detection of the PCR-LFS reached 50 CFU/mL. The optimized conditions for PMA treatment were 40 µM PMA, with light exposure at 40% for 3 min. Furthermore, the PMA-PCR-LFS assay accurately detected as low as 50 CFU/g of viable V. parahaemolyticus in the presence of a large number of non-viable cells in spiked codfish after a 2-hour enrichment, which provides a selective, simple and economically method for field detection of viable V. parahaemolyticus in codfish.

Measuring Reactive Sulfur Species and Thiol Oxidation States: Challenges and Cautions in Relation to Alkylation-Based Protocols.

Significance: Redox biology is gaining ground in research related to human physiology (metabolism, signaling), pathophysiology (cancer, cardiovascular disease, neurodegeneration), and toxicology (radiation- or xenobiotic-induced damage). A major hurdle in advancing redox medicine is the current lack of understanding the mechanisms underpinning the observed detrimental or beneficial in vivo effects. To gain deeper insights into the underlying molecular pathways of redox regulation, we need to appreciate the strengths and limitations of the currently available methods. Recent Advances: Reactive sulfur species (RSS), including cysteine derivatives of peptides and proteins along with small molecules such as hydrogen sulfide or inorganic polysulfides, are major players in redox biology. RSS-mediated regulation of protein functions is a widely studied mechanism in the field, and considerable efforts have been devoted to the development of selective detection methods. Critical Issues: A large number of available methods rely on an alkylation step to freeze the dynamism of consecutive oxidation and reduction events among RSS at a particular time point inside the cell. This process uses the assumption that alkylation blocks all redox events instantaneously. We argue that unfortunately this is often not the case, which could have serious impacts on detected sulfur species speciation and confound experimental results. Future Directions: Novel technologies and prudent optimization of existing methods to accurately characterize the dynamic redox status of the thiol proteome as well as detailed understanding of regulatory and signaling capacities of protein polysulfidation are crucial to open new routes toward therapeutic interventions.

Controlling over the terminal functionalities of thiol-capped CdZnTe QDs to develop fluorescence nanosensor for selective discrimination and determination of Fe(II) ions

Development of highly sensitive and selective methods for metal ions detection has been considered as one of the basic issues for environmental protection and human health. On basis of our success in one-pot hydrothermal route synthesized thiol-capped CdZnTe quantum dots (QDs) with different terminal functionalities, we demonstrated that N-acetyl-l-cysteine capped CdZnTe QDs (NAC-CdZnTe QDs) were quite stable to all of the tested metal ions, l-cysteine capped CdZnTe QDs (Lcys-CdZnTe QDs) exhibited quenched fluorescence behavior towards both Fe2+ and Ag+ ions while 3-mercaptopropionic acid capped CdZnTe QDs (MPA-CdZnTe QDs) featured to highly selective fluorescence response towards Fe2+ ions. The mechanism of the fluorescence behavior of thiol-capped CdZnTe QDs towards different metal ions has been discussed in depth. Such designed nanosensor based on MPA-CdZnTe QDs showed decreased fluorescence upon the introduction of increasing concentrations of Fe2+. There was a good linear relationship between the fluorescence intensity of MPA-CdZnTe QDs over a wide concentration range of 0.64−48 μM with a low detection limit of 0.2 μM on basis of S/N=3. The developed nanosensor could distinctly discriminate between two oxidation states of Fe (Fe2+ and Fe3+), and has succeeded in dissolved Fe fertilizer (FeSO4) for potted flower and spiked water samples analysis. This study not only offers a general route for the surface-engineering of ternary alloyed QDs to have desired terminal functionalities but also highlights the significance of surface chemistry in controlling the fluorescence behavior of QDs towards metal ions detection.

Phytosynthesis of Palladium Nanoclusters: An Efficient Nanozyme for Ultrasensitive and Selective Detection of Reactive Oxygen Species.

Hydrogen peroxide is a low-reactivity reactive oxygen species (ROS); however, it can easily penetrate cell membranes and produce highly reactive hydroxyl radical species through Fenton’s reaction. Its presence in abnormal amounts can lead to serious diseases in humans. Although the development of a simple, ultrasensitive, and selective method for H2O2 detection is crucial, this remains a strategic challenge. The peroxidase mimetic activity of palladium nanoclusters (PdNCs) has not previously been evaluated. In this study, we developed an ultrasensitive and selective colorimetric detection method for H2O2 using PdNCs. An unprecedented eco-friendly, cost-effective, and facile biological method was developed for the synthesis of PdNCs. This is the first report of the biosynthesis of PdNCs. The synthesized nanoclusters had a significantly narrow size distribution profile and high stability. The nanoclusters were demonstrated to possess a peroxidase mimetic activity that could oxidize peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB). Various interfering substances in serum (100 μM phenylalanine, cysteine, tryptophan, arginine, glucose, urea, Na+, Fe2+, PO43−, Mn+2, Ca2+, Mg2+, Zn2+, NH4+, and K+) were included to evaluate the selectivity of the assay, and oxidation of TMB occurred only in the presence of H2O2. Therefore, PdNCs show an efficient nanozyme for the peroxidase mimetic activity. The assay produced a sufficient signal at the ultralow concentration of 0.0625 µM H2O2. This colorimetric assay provides a real-time, rapid, and easy-to-use platform for the detection of H2O2 for clinical purposes.