Synergetic Sensing Effect of Sodium Carboxymethyl Cellulose and Bismuth on Cadmium Detection by Differential Pulse Anodic Stripping Voltammetry.

In the present work, a novel electrochemical sensor was developed for the detection of trace cadmium with high sensitivity and selectivity in an easy and eco-friendly way. Firstly, a glassy carbon electrode (GCE) was modified with nontoxic sodium carboxymethyl cellulose (CMC) by a simple drop-casting method, which was applied to detect cadmium by differential pulse anodic stripping voltammetry (DPASV) in a solution containing both target cadmium and eco-friendly bismuth ions, based on a quick electro-codeposition of these two metal ions on the surface of the modified electrode (CMC-GCE). Investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR), both CMC (with good film-forming ability) and bismuth (with well-defined stripping signal) were found to be well complexed with target cadmium, leading to vital signal amplification for cadmium detection at a sub-nanomolar level. Under the optimal conditions, the proposed sensor exhibited a good linear stripping signal response to cadmium (Ⅱ) ion, in a concentration range of 0.001 µmol/L-1 µmol/L with a limit of detection of 0.75 nmol/L (S/N = 3). Meanwhile, the results demonstrate that this novel electrochemical sensor has excellent sensitivity and reproducibility, which can be used as a promising detection technique for testing natural samples such as tap water.

Rapid and Sensitive Determination of Vanillin Based on a Glassy Carbon Electrode Modified with Cu2O-Electrochemically Reduced Graphene Oxide Nanocomposite Film.

A facile cuprous oxide nanoparticles functionalized electro-reduced graphene oxide modified glassy carbon electrode (denoted as Cu2O NPs-ERGO/GCE) was fabricated via a simple physical adsorption and electrochemical reduction approach. Cyclic voltammetry and second-order derivative linear scan voltammetry were used to investigate the electrocatalysis oxidation of vanillin on the Cu2O NPs-ERGO/GCE. The compound yielded a well-defined voltammetric response in 0.1 M H2SO4 at 0.916 V (vs. saturated calomel electrode (SCE)). A linear calibration graph was obtained in the concentration range of 0.1 µM to 10 µM and 10 µM to 100 µM, while the detection limit (S/N = 3) is 10 nM. In addition, the Cu2O NPs-ERGO/GCE presented well anti-interference ability, stability, and reproducibility. It was used to detect vanillin sensitively and rapidly in different commercial food products, and the results were in agreement with the values obtained by high performance liquid chromatography.

Abnormal Anionic Porphyrin Sensing Effect for HER2 Gene Related DNA Detection via Impedance Difference between MWCNTs and Single-Stranded DNA or Double-Stranded DNA.

Human epidermal growth factor receptor 2 (HER2) is a key tumor marker for several common and deadly cancers. It is of great importance to develop efficient detection methods for its over-expression. In this work, an electrochemical impedance spectroscopy (EIS) method adjustable by anionic porphyrin for HER2 gene detection has been proposed, based on the impedance difference between multi-walled carbon nanotubes (MWCNTs) and DNA. The interesting finding herein is that with the addition of anionic porphyrin, i.e., meso-tetra(4-sulfophenyl)-porphyrin (TSPP), the impedance value obtained at a glass carbon electrode (GCE) modified with MWCNTs and a single stranded DNA (ssDNA), the probe DNA that might be assembled tightly onto MWCNTs through π-π stacking interaction, gets a slight decrease; however, the impedance value from a GCE modified with MWCNTs and a double stranded DNA (dsDNA), the hybrid of the probe DNA with a target DNA, which might be assembled loosely onto MWCNTs for the screening effect of phosphate backbones in dsDNA, gets an obvious decrease. The reason may be that on the one hand, being rich in negative sulfonate groups, TSPP will try to push DNA far away from CNTs surface due to its strong electrostatic repulsion towards DNA; on the other hand, rich in planar phenyl or pyrrole rings, TSPP will compete with DNA for the surface of CNTs since it can also be assembled onto CNTs through conjugative interactions. In this way, the "loosely assembled" dsDNA will be repelled by this anionic porphyrin and released off CNTs surface much more than the "tightly assembled" ssDNA, leading to a bigger difference in the impedance value between dsDNA and ssDNA. Thus, through the amplification effect of TSPP on the impedance difference, the perfectly matched target DNA could be easily determined by EIS without any label. Under the optimized experimental conditions, this electrochemical sensor shows an excellent linear response to target DNA in a concentration range of 2.0 × 10-11⁻2.0 × 10-6 M with a limit of detection (LOD) of 6.34 × 10-11 M (S/N = 3). This abnormally sensitive electrochemical sensing performance resulting from anionic porphyrin for DNA sequences specific to HER2 gene will offer considerable promise for tumor diagnosis and treatment.

SiO2 Stabilized Magnetic Nanoparticles as a Highly Effective Catalyst for the Degradation of Basic Fuchsin in Industrial Dye Wastewaters.

Catalytic degradation of organic pollutants by nanomaterials is an effective way for environmental remediation. The Fenton reaction involving H2O2 oxidation catalysed by Fe3+ is an advisable way for wastewater degradation. Herein, Fe3O4/SiO2 core-shell nanoparticles were prepared as catalyst by coprecipitation and sol-gel methods, and this catalyst is used for degradation of fuchsin in wastewater by H2O2. The Fenton reaction between H2O2 and Fe3O4 is proposed to explain the catalytic performance. The coating of SiO2 on Fe3O4 nanoparticles could dramatically stabilize the Fe3O4 in aqueous solution and prevent their oxidation. More importantly, the magnetic property of Fe3O4 nanoparticles endows them with good recyclability. Thus, due to the outstanding catalytic results, almost 100% removal degradation was achieved within 5 min over a wide pH value range at room temperature, which is better than that without catalysts. Temperature is a positive factor for improving the degradation rate, but room temperature is selected as the best temperature for economic and energy savings reasons, because more than 98% of fuchsins can still be degraded at room temperature. Moreover, these Fe3O4/SiO2 core-shell nanoparticles exhibit excellent magnetic recyclability and stable properties after repeated utilization. Therefore, these as-presented Fe3O4/SiO2 core-shell nanoparticles with low-cost and high performance are expected to be applied in practical industry wastewater degradation.

Ultrasensitive Electrochemical Sensor Based on Polyelectrolyte Composite Film Decorated Glassy Carbon Electrode for Detection of Nitrite in Curing Food at Sub-Micromolar Level.

To ensure food quality and safety, developing cost-effective, rapid and precision analytical techniques for quantitative detection of nitrite is highly desirable. Herein, a novel electrochemical sensor based on the sodium cellulose sulfate/poly (dimethyl diallyl ammonium chloride) (NaCS/PDMDAAC) composite film modified glass carbon electrode (NaCS/PDMDAAC/GCE) was proposed toward the detection of nitrite at sub-micromolar level, aiming to make full use of the inherent properties of individual component (biocompatible, low cost, good electrical conductivity for PDMDAAC; non-toxic, abundant raw materials, good film forming ability for NaCS) and synergistic enhancement effect. The NaCS/PDMDAAC/GCE was fabricated by a simple drop-casting method. Electrochemical behaviors of nitrite at NaCS/PDMDAAC/GCE were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimum conditions, the NaCS/PDMDAAC/GCE exhibits a wide linear response region of 4.0 × 10-8 mol·L-1~1.5 × 10-4 mol·L-1 and a low detection 1imit of 43 nmol·L-1. The NaCS/PDMDAAC shows a synergetic enhancement effect toward the oxidation of nitrite, and the sensing performance is much better than the previous reports. Moreover, the NaCS/PDMDAAC also shows good stability and reproducibility. The NaCS/PDMDAAC/GCE was successfully applied to the determination of nitrite in ham sausage with satisfactory results.

Mapping inhibitor response to the in-frame deletions, insertions and duplications of epidermal growth factor receptor (EGFR) in non-small cell lung cancer.

Human epidermal growth factor receptor (EGFR) has become a well-established target for the treatment of non-small cell lung cancer (NSCLC). However, a large number of in-frame deletion, insertion and duplication mutations in the EGFR tyrosine kinase (TK) domain have been observed to alter drug response to such a kinase target. Thus, a systematic investigation of the intermolecular interactions between the clinical small-molecule agents and various EGFR in-frame mutants would help to establish a complete picture of drug response to kinase mutations in lung cancer, and to design new EGFR inhibitors with high potency and selectivity to target drug-resistant mutants. Here, we describe a combined pipeline to explore the drug response of five representative EGFR inhibitors, including three FDA-approved agents (gefitinib, erlotinib and lapatinib) and two compounds under clinical development (AEE788 and TAK-285) to a number of clinically relevant EGFR in-frame mutations, aiming at a comprehensive understanding of molecular mechanism and biological implication underlying drug resistance and sensitivity to EGFR in-frame mutations. It was found that the insertion and duplication mutations in exon 20 can generally cause drug resistance to EGFR due to the reduced size of kinase's active pocket, while deletion mutations in exon 19 associate closely with increased inhibitor sensitivity to EGFR by establishing additional non-bonded interactions across complex interface, including hydrogen bonds, cation-π interactions and hydrophobic contacts.

A high performance Pb(II) electrochemical sensor based on spherical CuS nanoparticle anchored g-C3N4.

A new electrochemical sensor has been constructed for ultra-sensitive detection of lead ions (Pb2+) by square wave anodic stripping voltammetry (SWASV), based on the copper sulfide/graphitic carbon nitride nanocomposite modified glassy carbon electrode (CuS/g-C3N4/GCE). First, spherical CuS nanoparticles with good electrical conductivity were anchored on layered g-C3N4 with high coordination activity, affording an excellent electrode modifier CuS/g-C3N4 nanocomposite. Then, the performance of the CuS/g-C3N4/GCE and its electrochemical response to Pb2+ were thoroughly studied, and the sensing mechanism was investigated. On the one hand, the CuS/g-C3N4 nanocomposite has greatly improved the electron transportation and electrode performance through functional complementarity - CuS endows g-C3N4 with a good electrical conductivity and a large active specific surface area, while g-C3N4 endows CuS with high dispersibility and strong adsorption. On the other hand, the CuS/g-C3N4 modifier has effectively promoted the deposition of trace Pb2+ from the solution onto the electrode surface by means of synergistic enrichment (crucial for amplification of detection signals) - g-C3N4 can coordinate with Pb2+ by its large number of conjugated triazine heterocyclic rings in its molecular framework, while CuS can adsorb Pb2+ due to its inherent size effect of nanomaterials. The proposed sensor can efficiently detect Pb2+ in the concentration range of 0.050-5.000 µM with a limit of detection (LOD) as low as 4.00 nM, and can be well applied for the detection of trace Pb2+ in actual tea samples.

A Water-soluble Fluorescent Probe for Rapid Detection of Sulfur Dioxide Derivatives.

The content of sulfur dioxide derivatives in cells is closely related to life and health. Therefore, it is essential to detect the content of sulfur dioxide derivatives in cells under physiological conditions to ensure life and health. In this paper, a novel sulfur dioxide derivative fluorescent water-soluble probe ((E)-1,1,3-trimethyl-2-(2-(naphthalen-1-yl)vinyl)-1H-3λ4-benzo[e]indole, TNB) was synthesized by using naphthalene formaldehyde (1) and 1,1,2,3-tetramethyl-1H-3λ4-benzo[e]indole (2) as raw materials. Based on the intramolecular charge transfer (ICT) mechanism of the naphthalene ring to benzoindole, TNB exhibits very weak fluorescence emission in PBS buffer (pH 7.4). The olefin unit of TNB can be combined with HSO3-/SO32- with high selectivity to make the π-π conjugate interrupt. ICT is blocked, TNB produces a strong fluorescence emission, and the color visible to the naked eye changes from yellow to colorless. The effect of TNB on HSO3-/SO32- can be completed in 40 s, the fluorescence intensity is increased by 91 times, and the detection limit is as low as 0.089 µM. It is expected to be able to rapidly detect low levels of sulfur dioxide derivatives in cells, which has important application prospects in maintaining life and health.

3-Bromo-N'-(2-hydr-oxy-3,5-diiodo-benzyl-idene)benzohydrazide monohydrate.

Crystals of the title compound, C(14)H(9)BrI(2)N(2)O(2)·H(2)O, were obtained from a condensation reaction of 3-bromo-benzohydrazide with 3,5-diiodo-salicylaldehyde. The Schiff base mol-ecule assumes an E configuration with respect to the C=N bond, and the dihedral angle between the two benzene rings is 6.9 (2)°. An intra-molecular O-H⋯N hydrogen bond is observed in the Schiff base mol-ecule and may contribute to its overall near planarity. In the crystal structure, mol-ecules are linked through inter-molecular O-H⋯O and N-H⋯O hydrogen bonds, forming layers parallel to the bc plane. Short inter-molecular I⋯O contacts [2.930 (5) Å] are also found, linking the mol-ecules into zigzag chains along b.

A new indicator of ionic polymeric flocculants for the removal of heavy metals anions: Specific charge density.

Ionic polymeric flocculants, as useful and widely used technology, have been applied for heavy metal pollution control. However, although molecular weight is an important indicator, it is not a comprehensive indicator for evaluating flocculation efficiencies of ionic flocculants. Herein, specific charge density (SCD), defined as charge density of unit molecular weight, is a new indicator to evaluate the performance of ionic polymer flocculants. Polydiallyldimethylammonium chloride (PDADMAC) as coagulant aid is investigated to flocculate different anionic pollutants. The results indicate that PDADMAC with a high SCD value could benefit to the flocculation efficiency of anionic pollutants. According to statistical analysis, the average pollutants residual could decrease to 8.64%-32.27% by that with high SCD value, especially for high valence pollutants with a decrease from 58.97%-60.40% to 27.35%-32.27%. The indicator of SCD values not only could characterize the performance of polymer flocculants but also provide a new sight of the flocculation mechanism of polymeric flocculants. PRACTITIONER POINTS: Specific Charge Density (SCD) is defined as charge density of unit molecularweight. SCD as a new indicator to evaluate comprehensively the performance of flocculants. Removal efficiencies by flocculation increase with SCD value of PDADMAC increase. Effect of SCD of PDADMAC on removal of pollutant with high valence is significant. SCD of PDADMAC is less indicative for removal of pollutant with low valence.

Structural and energetic insights into sequence-specific interaction in DNA-drug recognition: development of affinity predictor and analysis of binding selectivity.

Although the molecular mechanism and thermodynamic profile of a wide variety of chemical agents have been examined intensively in the past decades in terms of specific recognition of their protein receptors, to date the physicochemical nature of DNA-drug recognition and association still remains largely unexplored. The present study focused on understanding the structural basis, energetic landscape, and biological implications underlying the binding of small-molecule ligands to their cognate or non-cognate DNA receptors. First, a new method to capture the structural features of DNA-drug complex architecture was proposed and then used to correlate the extracted features with binding affinity of the complexes. By employing this method, a statistical regression-based predictor was developed to quantitatively evaluate the interaction potency of drug compounds with DNA in a fast and reliable manner. Subsequently, we use the predictor to examine the binding behavior of a number of structure-available, affinity-known DNA-drug complexes as well as a large pool of randomly generated DNA decoys in complex with the same drugs. It was found that (1) as compared with protein-DNA recognition, small-molecule agents have relatively low specificity in selecting their cognate DNA targets from the background of numerous random decoys; (2) the abundance of A-T base pairs in the DNA core motif exhibits a significant positive correlation with the affinity of drug ligand binding to the DNA receptor; and (3) high affinity seems not to be closely related to high selectivity for a DNA-targeting drug, although high-affinity drug entities have a greater possibility of being ranked computationally as top binders. We hope that this work will provide a preliminary insight into the molecular origin of sequence-specific interactions in DNA-drug recognition.