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Abstract: In this paper, 2-(2′-hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), a typical compound that exhibits excited state intramolecular proton transfer (ESIPT) reaction and possesses good photophysical properties, is synthesized and used as fluoroionophore for Fe3+ sensitive optochemical sensor. The decrease of fluorescence intensity of HPQ membrane upon the addition of Fe3+ was attributed to the blocking of ESIPT reactions of HPQ and quenching its fluorescence. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensor shows a linear response toward Fe3+ in the concentration range of 7.1×10−7 M to 1.4×10−4 M with a limit of detection of 8.0×10−8 M, and a working pH range from 2.5 to 4.5. It shows excellent selectivity for Fe3+ over a large number of cations such as alkali, alkaline earth and transitional metal ions. The proposed sensor is applied to the determination of the content of iron ions in pharmaceutical preparations samples with satisfactory results. [Copyright &y& Elsevier]

Abstract: The design and synthesis of a porphyrin-appended terpyridine, 5-(4-([2,2′:6′,2″]-terpyridin-4-yl-carboxyamidyl)phenyl)-10,15,20-triphenylporphyrin (H2TPPTPy) and its application as potential fluoroionophore for recognition of metal ions are reported. For preparation of the fluoroionophore, a novel simple strategy with improved total yield has been applied for the synthesis of 2,2′:6′,2″-terpyridine-4′-carboxylic acid as a ligand. H2TPPTPy shows chelation-enhanced fluorescence effect with cadmium ion via the interruption of photoinduced electron transfer (PET) process, which has been utilized as the basis of the fabrication of the Cd(II)-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Cd(II)-sensitive chemosensor were investigated. It shows a linear response toward Cd(II) in the concentration range of 3.2×10−6 to 3.2×10−4 M with a limit of detection of 1.2×10−6 M. The chemosensor shows good selectivity for Cd(II) over a large number of cations, such as alkali, alkali earth and transitional metal ions except Cu(II) and Zn(II). The sensor has been used for determination of Cd(II) in water samples with satisfactory recoveries. [Copyright &y& Elsevier]

Abstract: An electrochemical immunoassay technique has been developed based on the sensitive detection of the enzyme-generated product with a bi-electrode signal transduction system. The system uses two separate electrodes, an immunoelectrode and a detection electrode to form a galvanic cell to implement the redox reactions on two different electrodes, that is the enzyme-generated reductant in the anode region is electrochemically oxidized by an oxidant (silver ions) in the cathode apartment. Based on a sandwich procedure, after immunoelectrode with antibody immobilized on its surface bound with the corresponding antigen and alkaline phosphatase conjugated antibody successively, the immunoelectrode was placed in enzyme reaction solution and wired to the detection electrode which was immerged into a silver deposition solution. These two solutions are connected with a salt bridge. Thus a bi-electrode signal transduction system device is constructed in which the immunoelectrode acts as anode and the detection electrode serves as cathode. The enzyme bound on the anode surface initiates the hydrolysis of ascorbic acid 2-phosphate to produce ascorbic acid in the anode region. The ascorbic acid produced in the anodic apartment is electrochemically oxidized by silver ions coupled with the deposition of silver metal on the cathode. Via a period of 30min deposition, silver will deposited on the detection electrode in an amount corresponding to the quantity of ascorbic acid produced, leading to a great enhancement in the electrochemical stripping signal due to the accumulation of metallic silver by enzyme-generated product. Compared with the method using chemical deposition of silver, the electrochemical deposition of silver on a separate detection electrode apartment avoids the possible influence of silver deposition on the enzyme activity. [Copyright &y& Elsevier]

Abstract: A fluorescent chemical sensor for Hg(II) using 5,10,15-tris(pentafluorophenyl)corrole (H3(tpfc)) as fluorophore is described in this paper. The response of the sensor is based on the fluorescence quenching of H3(tpfc) by coordination with Hg(II). H3(tpfc) based sensor shows a linear response towards Hg(II) in the concentration range from 1.2×10−7 to 1.0×10−4 M, with a working pH range from 5.0 to 8.0. The response time for Hg(II) concentration ≤1.0×10−5 M is less than 5min. The sensor shows good selectivity for Hg(II) over alkali, and alkaline earth, and most of transition metal cations. The effect of the composition of the sensor membrane has been studied and the experimental conditions optimized. The corrole based sensor membrane can be easily regenerated just by washing with blank buffer solution after each measurement. The sensor has been used for determination of Hg(II) in water samples with satisfactory results. [Copyright &y& Elsevier]

The construction of versatile functional hydrogel interfaces holds promising prospects in biosensing and bioengineering. Herein, we introduced a light-induced protein conjugation strategy for on-demand surface modification of hydrogel interface based on the photoclick cyclization between primary amine and o -nitrobenzyl alcohol. We achieved the on-demand protein conjugation by grafting the molecular plugin, 4-(hydroxymethyl)-3-nitrobenzoic acid (HNBA), onto the hydrogel surface, followed by the mask-aided photoclick reaction with the protein of interest. This method enables the creation of protein patterns on hydrogel interface with a lower limit of pattern width at ∼70 μm. With this method, we demonstrated the surface engineering of epidermal growth factor (EGF) on hydrogel interface for selective capture of EGF receptor-positive cancer cells with an efficiency over 80%. Moreover, we applied the mask-aided photoclick conjugation method for antigen capture and developed a photoclickable hydrogel interface-based dot blotting assay. Due to the high-efficient antigen capture of photoclick conjugation, the photoclickable hydrogel interface-based dot blotting assay shows improved sensitivity for antigen detection with a limit of detection as 0.065 ng. We believed that this light-induced protein conjugation method holds the potential as a robust strategy for the construction of bioactive hydrogel interfaces for various bio-related applications. A light-induced protein conjugation strategy was proposed for the on-demand surface modification of hydrogel interface, which relies on the photoclick cyclization between primary amine in protein of interest and 4-(hydroxymethyl)-3-nitrobenzoic acid grafted on the hydrogel interface. [Display omitted] • A photoclickable hydrogel interface was constructed by grafting a molecular plugin, 4-(hydroxymethyl)-3-nitrobenzoic acid. • With a mask-aided photoclick conjugation strategy, the on-demand surface modification of hydrogel interface with desirable patterns can be achieved with a lower limit of pattern width at ∼70 μm. • EGF-functionalized hydrogel interface was constructed with the light-induced protein conjugation strategy for selective capture of EGFR-positive cancer cells with an efficiency over 80%. • A photoclickable hydrogel interface-based dot blotting assay was developed for antigen detection with a limit of detection as 0.065 ng. [ABSTRACT FROM AUTHOR]

Lysosomes contains numerous enzymes and proteins closely linked with cellular metabolism. The variation of lysosomal pH is closely related to cell homeostasis while hydrogen sulfide (H 2 S) has been regarded as an important gasotransmitter. Herein, via rational design, a high-sensitivity fluorescent probe ANp-Rh-Lys was synthesized for logical detection and bioimaging of H 2 S and pH in lysosomes of living cells. The probe showed different fluorescence signals towards H 2 S and lysosomal pH. Significantly, ANp-Rh-Lys is membrane-permeable and suitable for visualization of both pH variations and endogenous H 2 S in lysosomes. This logical design strategy may have great potential for detection of multiple analytes in complicated biological systems. A promising ratiometric fluorescent probe for logical imaging of H 2 S and pH in lysosomes was first proposed. Image 1 • As a proof-of-concept, to design the dual-sites for orthometric response by two species is of great challenge. • With different output fluorescence signals, a single fluorescent probe can realize logical imaging of pH and H 2 S in lysosome. • Our probe may serve as the basis for independently or concurrently detection of key biomolecules in the signal transduction and diseases formation. [ABSTRACT FROM AUTHOR]

The monitoring of K + is very important and emergency because of their unique relationship in various disease diagnosis and treatment. G-quadruplex analogue is a classical recognition unit for K + detection and has been widely applied in K + relevant research. Common fluorescent dyes were employed for design of G-quadruplex structure-based K + probes which suffered from the aggregation-caused quenching effect, and possibly limited the biological applications in living systems. Herein, we report an aggregation-induced emission (AIE) effect-based fluorescent probe for cellular K + analysis and imaging. Benefitting from the K + triggered AIE phenomenon, the designed TPE derivative modified guanine (G)-rich oligonucleotide fluorescent probe (TPE-oligonucleotide probe) exhibits high sensitivity (∼10-fold higher than most reported G-quadruplex-based probes) with extended photostability which facilitates the prolonged fluorescence observations of K + in living cells. On the basis of these advantages, the TPE-oligonucleotide probe serves as a promising candidate for the functional study and analysis of K + . [ABSTRACT FROM AUTHOR]

In this work we use a water-soluble cationic perylene derivative (compound 1) as the G-quadruplex (G4) structure fluorescence indicator to construct a fluorescent biosensor for simple, rapid and label-free detection of Pb 2+ . In the absence of Pb 2+ , strong electrostatic interactions between compound 1 and the G-rich DNA probe (PW17) induced the aggregation of compound 1 and resulted in the fluorescence quenching. In the presence of Pb 2+ , the PW17 formed Pb 2+ -stabilized G4 structure, which reduced the aggregation of compound 1 and gave rise to high fluorescence. This allowed us to use convenient “mix-and-detect” protocol for quantitative analysis of Pb 2+ . Since Pb 2+ can specially induce PW17 to form compact DNA fold, our proposed biosensor displayed high selectivity for Pb 2+ . It also exhibited a high sensitivity to Pb 2+ , with a limit of detection of 5.0 nM observed. Furthermore, the biosensor was applied for the detection of Pb 2+ in urine and paint samples, and both showed satisfactory results. [ABSTRACT FROM AUTHOR]

DNAzyme-based catalytic beacons have been widely studied for both in vivo and in vitro molecular detection. However, only a few label-free catalytic beacons with excellent analytical performance have been reported so far. In this work, by combining a catalytic DNAzyme for amplified sensing through enzymatic turnover with cleavage-induced G-quadruplex formation, a label-free DNAzyme biosensor was developed for amplified “turn-on” fluorescence detection of Pb 2+ with a detection limit of 3 nM. The method is very competitive compared to many other labeled or label-free methods with or without signal amplification. Due to the inherent specificity of the GR-5 DNAzyme, the method also exhibits excellent selectivity. This biosensor successfully detected Pb 2+ in river water samples with high sensitivity and selectivity. Such a method might provide a universal DNAzyme-based sensing platform for sensitive detection of various targets both in environmental and biomedical fields. [ABSTRACT FROM AUTHOR]

Abstract: Development of fluorescent probes for Hg2+ has become a hot topic in modern chemical research due to its high toxicity. In this paper, we for the first time report the synthesis and application of a thioether spirocyclic rhodamine B derivative (TR) as an efficient fluorescent probe for Hg2+. TR was synthesized using a simple procedure under mild condition. By employing a thioether spirocycle instead of classic spirolactam as recognition unit, our proposed probe TR is acidity-insensitive, and exhibits a pH-independent and ultrasensitive response to Hg2+. The probe works well within a wide pH range from 3.5 to 11.5, and exhibits a 350-fold fluorescence enhancement upon 0.5equiv of Hg2+ triggered, with a detection limit of 2.5nM estimated for Hg2+. In virtue of the strong thiophilic characteristic of Hg2+, the response of the probe to Hg2+ is instantaneous and highly selective, which make it favorable for cellular Hg2+ imaging applications. It has been preliminarily used for highly sensitive monitoring of Hg2+ level in living cells with satisfying resolution, demonstrating its value of the practical applications in biological systems. [Copyright &y& Elsevier]

Abstract: A new and facile strategy using double-stranded DNA-copper nanoparticles (dsDNA-Cu NPs) as fluorescence reporters for the highly sensitive and selective detection of l-histidine was demonstrated. In the dsDNA-Cu NPs-based sensing system, the fluorescence was quenched considerably upon the addition of l-histidine. Under the optimized experimental conditions, the probe exhibits excellent performance (e.g., a satisfactory detection limit of 5μM and high specificity). Our in situ method requires no covalent attachment of DNA to a fluorophore, which could significantly reduce the cost and simplify the procedure for l-histidine detection. Moreover, the proposed sensing system could be applicable for the detection of target biomolecule in complex biological samples. These striking properties make it an attractive platform for the direct detection of l-histidine. [Copyright &y& Elsevier]

Abstract: A sensitive immunosensor using colloidal gold as electrochemical label is described. In this method, the capture protein was first immobilized on a carbon paste electrode surface through passive adsorption to bind quantitatively with corresponding antigen and colloidal gold labeled antibody to perform a sandwich assay. To detect the amount of the colloidal gold captured on the electrode surface, the colloid was first oxidized electrochemically to produce AuCl4 − ions which were adsorbed strongly on the electrode surface. Adsorptive voltammetry was then employed for the determination of the adsorbed AuCl4 − ions. A linear relationship between reduction wave peak current and the antigen concentration (human IgG) from 10 to 500ng/ml is obtained with a detection limit of 4.0ng/ml. [Copyright &y& Elsevier]

Here we report the peroxidase-like Au@Pt nanozyme as an integrated nanosensor for selective detection of silver ions (Ag+), where the nanozyme plays the roles as both the signal trigger and reporter simultaneously. This method relies on two critical chemical reactions, including (1) the unique inhibitory effect of Ag+ on the nanozyme triggered H 2 O 2 decomposition at weak acid environment and (2) H 2 O 2 induced Ag+ reduction onto the nanozyme surface at basic environment, leading to a blueshift in the localized surface plasmonic resonance wavelength (LSPR λ max) of the nanosensor. With this simple strategy, we demonstrated the sensitive and selective detection of Ag+ over a dynamic range from 0.5 to 1000 μM with a limit of detection (LOD) of 500 nM by UV–visible spectroscopy, which is below the permitted level of Ag+ in drinking water by U.S. Environmental Protection Agency (EPA). This method also exhibits satisfying recovery efficiency for Ag+ detection both in tap water and spring water from the Yuelu Mountain. With this satisfying sensing performance and excellent stability of nanoprobes, this strategy is promising for the detection of Ag+ in environment monitoring and food safety analysis. The peroxidase-like Au@Pt nanozyme was proposed as a novel integrated nanosensor for selective and sensitive detection of Ag+ by LSPR spectroscopy, which relies on the unique inhibitory effect of Ag+ on the nanozyme triggered H 2 O 2 decomposition at weak acid environment and residual H 2 O 2 induced Ag+ reduction onto the nanozyme surface at basic environment. Image 1 • The unique inhibitory effect of Ag+ on the Au@Pt nanozyme triggered H 2 O 2 decomposition was disclosed. • A new nanosensor was constructed with Au@Pt nanozyme which acts as the signal trigger and reporter. • Facile Ag+ sensing by LSPR spectroscopy with satisfying sensing performances was achieved. [ABSTRACT FROM AUTHOR]