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

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

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

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. (C) 2019 Water Environment Federatio

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

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

Determination of Uric Acid in Co-Presence of Dopamine and Ascorbic Acid Using Cuprous Oxide Nanoparticle-Functionalized Graphene Decorated Glassy Carbon Electrode

Cuprous oxide nanoparticles (Cu2O NPs) were dispersed into a graphene oxide (GO) solution to form a homogeneous Cu2O-GO dispersion. After this, the cuprous oxide nanoparticles were functionalized to electrochemically reduce the graphene oxide decorated glassy carbon electrode (Cu2O-ErGO/GCE). This was prepared by coating the Cu2O-GO dispersion onto the surface of the glassy carbon electrode (GCE), which was followed by a potentiostatic reduction process. An irreversible two-electron reaction of uric acid (UA) was observed at the voltammetric sensor. Moreover, the high concentrations of dopamine (DA) and ascorbic acid (AA) hardly affected the peak current of UA, which suggested that Cu2O-ErGO/GCE have excellent selectivity for UA. This is probably because the response peaks of the three compounds are well-separated from each other. The oxidation peak current was proportional to the concentration of UA in the ranges of 2.0 nM−0.6 μM and 0.6 μM−10 μM, respectively, with a low limit of detection (S/N = 3, 1.0 nM) after an accumulation time of 120 s. Cu2O-ErGO/GCE was utilized for the rapid detection of UA in human blood serum and urine samples with satisfactory results

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