Fabrication of a Sensitive Impedance Biosensor of DNA Hybridization Based on Gold Nanoparticles Modified Gold Electrode

In this work, we report on the preparation of a simple, sensitive DNA impedance sensor. Firstly gold nanoparticles were electrodeposited on the surface of a gold electrode, and then probe DNA was immobilized on the surface of gold nanoparticles through a 5′‐thiol‐linker. Electrochemical impedance spectroscopy (EIS) was used to investigate probe DNA immobilization and hybridization. Compared to the bare gold electrode, the gold nanoparticles modified electrode could improve the density of probe DNA attachment and the sensitivity of DNA sensor greatly. The difference of electron transfer resistance (ΔR_et) was linear with the logarithm of complementary oligonucleotides sequence concentrations in the range of 2.0×10^?12 to 9.0×10^?8 M, and the detection limit was 6.7×10^?13 M. In addition, the DNA sensor showed a fairly good reproducibility and stability during repeated regeneration and hybridization cycles.     

A Sensitive Biosensor for Determination of Cu2+ by One‐step Electrodeposition

A simple one‐step electrodeposition method is described to fabricate three dimensional ordered macroporous chitosan?prussian blue?single walled carbon nanotubes (3DOM CS?PB?SWCNTs) film onto the gold electrode surface to fabricate a copper ions (Cu²⁺)‐specific DNAzyme biosensor. The new sensing strategy for sensitive and selective detection of Cu²⁺ was based on Au nanorods (AuNRs) as signal amplification labels. The electrochemical signal of glucose increased with the concentration of Cu²⁺ increasing. The morphologies and electrochemistry of the composites were investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical techniques including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and so on. Linear correlations of copper ion concentration were obtained in the range from 10^?18 M to 10^?5 M, achieving with a limit of detection of 10^?19 M (S/N=3). Parameters affecting the biosensor response such as temperature, the cleavage time and the time of hybridization were optimized. This biosensor showed a wide range, low detection limit, good reproducibility and high stability. Additionally, these striking properties endow the biosensor with a great promise for analytical applications.     

纳米铂颗粒修饰薄膜金电极的新型葡萄糖传感器研究

在没有引入电子媒介体条件下,为了提高传感器的响应灵敏度,降低工作电位,利用电化学沉积法在薄膜金电极表面修饰纳米铂颗粒,并通过戊二醛固定酶的方法制备了一种新型生物传感器。研究了在薄膜金电极上修饰纳米铂颗粒前后传感器对低浓度葡萄糖的响应影响。结果表明,纳米铂颗粒修饰后所制备的葡萄糖传感器工作电位下降为0.4 V,测定葡萄糖的检出限从100μmol/L下降到10μmol/L。传感器对10~1300μmol/L低浓度葡萄糖的响应灵敏度为50.8 nA/(cm2μmol/L);响应时间30 s;r为0.9974;传感器精密度为2.1%,并具有较好的稳定性。     

A Sensitive Hydrogen Peroxide Sensor Based on Hemoglobin Immobilized on Gold Nanoparticles and 1,6-hexanedithiol Modified Gold Electrode

Hemoglobin (Hb) was successfully immobilized on a gold electrode modified with gold nanoparticles (AuNPs) via a molecule bridge 1,6-hexanedithiol (HDT). The AFM images suggested that the HDT/gold electrode could adsorb more AuNPs. UV-vis spectra indicated that Hb on AuNPs/HDT film retained its near-native secondary structures. The electrochemical behaviors of the sensor were characterized with cyclic voltammetric techniques. The resultant electrode displayed an excellent electrocatalytical response to the reduction of hydrogen peroxide (H₂O₂). The linear relationship existed between the catalytic current and the H₂O₂ concentration ranging from 5.0 × 10^?8 to 1.0 × 10^?6 mol · L^?1. The detection limit (S/N = 3) was 1.0 × 10^?8 mol · L^?1.     

Safranal Induces Vasorelaxation by Inhibiting Ca2+ Influx and Na+/Ca2+ Exchanger in Isolated Rat Aortic Rings

Introduction: Safranal, which endows saffron its unique aroma, causes vasodilatation and has a hypotensive effect in animal studies, but the mechanisms of these effects are unknown. In this study, we investigated the mechanisms of safranal vasodilation. Methods: Isolated rat endothelium-intact or -denuded aortic rings were precontracted with phenylephrine and then relaxed with safranal. To further assess the involvement of nitric oxide, prostaglandins, guanylate cyclase, and phospholipase A₂ in safranal-induced vasodilation, aortic rings were preincubated with L-NAME, indomethacin, methylene blue, or quinacrine, respectively, then precontracted with phenylephrine, and safranal concentration–response curves were established. To explore the effects of safranal on Ca²⁺ influx, phenylephrine and CaCl₂ concentration–response curves were established in the presence of safranal. Furthermore, the effect of safranal on aortic rings in the presence of ouabain, a Na⁺-K⁺ ATPase inhibitor, was studied to explore the contribution of Na⁺/Ca²⁺ exchanger to this vasodilation. Results: Safranal caused vasodilation in endothelium-intact and endothelium-denuded aortic rings. The vasodilation was not eliminated by pretreatment with L-NAME, indomethacin, methylene blue, or quinacrine, indicating the lack of a role for NO/cGMP. Safranal significantly inhibited the maximum contractions induced by phenylephrine, or by CaCl₂ in Ca²⁺-free depolarizing buffer. Safranal also relaxed contractions induced by ouabain, but pretreatment with safranal totally abolished the development of ouabain contractions. Discussion/Conclusion: Inhibition of Na⁺-K⁺ ATPase by ouabain leads to the accumulation of Na⁺ intracellularly, forcing the Na⁺/Ca²⁺ exchanger to work in reverse mode, thus causing a contraction. Inhibition of the development of this contraction by preincubation with safranal indicates that safranal inhibited the Na⁺/Ca²⁺ exchanger. We conclude that safranal vasodilation is mediated by the inhibition of calcium influx from extracellular space through L-type Ca²⁺ channels and by the inhibition of the Na⁺/Ca²⁺ exchanger.     

基于MCM-41负载联吡啶钌的电致化学发光传感器

利用静电吸附作用将联吡啶钌[Ru(bpy)₃²⁺]负载到巯基化MCM-41介孔二氧化硅纳米颗粒上, 通过金-巯键修饰法将负载后的MCM-41固定在金电极表面, 发展了一种基于MCM-41负载联吡啶钌的电致化学发光传感器, 并研究了其电化学及电致化学发光行为. 基于三聚氰胺与增敏剂三正丙胺氨基结构的相似性, 将负载Ru(bpy)₃²⁺的MCM-41电致化学发光传感器用于三聚氰胺的检测, 获得了良好的检测效果, 为检测三聚氰胺提供了一种快速、简便的方法. 同时, 该研究为Ru(bpy)₃²⁺在电极表面的固定化提供了新思路.     

Thermal investigations of nitrate-hydrates and deuterates of Ca2+, Cd2+ and Mg2+

DTA and DSC were used to study the thermal behaviour of Ca(NO₃)₂·4H₂O, Cd(NO₃)₂·4H₂O, Mg(NO₃)₂·6H₂O and their deuterated analogues. Evidence was found concerning the process of melting of the initial hydrates and deuterates, followed by a one-stage dehydration of the melt to vield the respective anhydrous salt. T _m, ΔH _m ^o , ΔS _m ^o and ΔH _deh ^o were determined and the ΔH _f ^o values for the investigated hydrates were calculated from the ΔH _deh ^o data.

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Zusammenfassung DTA und DSC wurden zur Untersuchung des thermischen Verhaltens von Ca(NO₃)₂·4H₂O, Cd(NO₃)₂·4H₂O, Mg(NO₃)₂·6H₂O und ihrer deuterierten Analoge eingesetzt. Man fand Aussagen bezüglich des Schmelzvorganges der Ausgangshydrate und Deuterate, gefolgt von einer Einschritt-Dehydratation der Schmelze unter Bildung der entsprechenden wasserfreien Salze. T _m, ΔH _m ^o , ΔS _m ^o und ΔH _deh ^o wurden ermittelt und die ΔH _f ^o Werte für die untersuchten Hydrate wurden anhand der ΔH _deh ^o berechnet.

     

“两面神”型金纳米粒子比色检测铁离子的新方法

制备了一种聚乙二醇(PEG)和柠檬酸根不对称修饰的"两面神"型金纳米粒子(Janus AuNPs)比色传感器,并基于此建立了铁离子(Fe~(3+))比色检测的新方法。首先,利用柠檬酸钠还原法制备了粒径相对较大的金纳米粒子,随后,以玻片为基底,将大粒径金纳米粒子修饰在玻片上,利用玻片掩蔽部分柠檬酸根位点,并进一步在金纳米粒子非接触区域上修饰大量PEG链,得到柠檬酸根和PEG不对称修饰的Janus AuNPs。引入Fe~(3+)后,有限区域内的柠檬酸根诱导Janus AuNPs发生定向聚集,形成金纳米粒子寡聚体并在水溶液中保持稳定。Janus AuNPs溶液吸光度比值与Fe~(3+)浓度在1μmol/L～10 mmol/L范围内呈线性变化(y=0.129x+0.317),检出限为715 nmol/L。与同类方法相比,该方法操作简便、灵敏度高,且可极大拓宽检测的线性范围。     

Electrochemical Morphine Sensor Based on Gold Nanoparticles Metalphthalocyanine Modified Carbon Paste Electrode

Composites of gold nanoparticles (Au) electrochemically deposited and different metal phthalocyanines (Co, Ni, Cu, and Fe) were chemically prepared. The composites were used as modifiers for carbon paste electrodes and were used for the determination of morphine in presence of ascorbic acid and uric acid. Central metal atoms of phthalocyanine moiety affected the rate of electron transfer. Thus, the electroactivity of different modifiers were evaluated towards morphine oxidation. Au‐CoPcM‐CPE possessed the highest rate for charge transfer rate in all studied pH electrolytes. Limit of detection was 5.48×10^?9 mol L^?1 in the range of 4.0×10^?7 to 9.0×10^?4 mol L^?1.     

Glassy Carbon Electrode Modified with Citrate Stabilized Gold Nanoparticles for Sensitive Arsenic (III) Detection

The electrochemical detection of As(III) was investigated on the novel citrate stabilized gold nanoparticle modified glassy carbon electrode (AuNPs/GCE) in 1 M HCl by square wave anodic stripping voltammetry. AuNPs/GCE was prepared by simply casting citrate stabilized gold nanoparticles onto the well-polished glassy carbon electrode. Gold modification was evaluated by cyclic voltammetry, while transmission electron microscopy and UV-vis Spectroscopy revealed the size and distribution of gold nanoparticles. Anodic stripping voltammetry was performed with the modified electrode in As(III) solution. Electrochemical experiments proved that AuNPS/GCE exhibited good performance for As(III) analysis, the linear range were obtained between 0.05 and 1 ppb for trace level of As(III) as well as 1 to 15 ppb, with a limit of detection of 0.025 ppb. In terms of reproducibility, the precision of the aforementioned method in %RSD was calculated at 7.78% (n = 10), and the repeatability of the proposed method was calculated to be 1.59%. The application of the method to analyze As(III) in tap water was investigated.     

Fabrication of a Sensitive Electrochemical Biosensor for Detection of DNA Hybridization Based on Gold Nanoparticles/CuO Nanospindles Modified Glassy Carbon Electrode

In this work, a sensitive electrochemical DNA biosensor for the detection of sequence‐specific target DNA was reported. Firstly, CuO nanospindles (CuO NS) were immobilized on the surface of a glassy carbon electrode (GCE). Subsequently, gold nanoparticles (Au NPs) were introduced to the surface of CuO NS by the electrochemical deposition mode. Probe DNA with SH (HS‐DNA) at the 5′‐phosphate end was covalently immobilized on the surface of the Au NPs through Au? S bond. Scanning electron microscopy (SEM) was used to elucidate the morphology of the assembled film, and electrochemical impedance spectroscopy technique (EIS) was used to investigate the DNA sensor assembly process. Hybridization detection of DNA was performed with differential pulse voltammetry (DPV) and the methylene blue (MB) was hybridization indicator. Under the optimal conditions, the decline of reduction peak current of MB (ΔI) was linear with the logarithm of the concentration of complementary DNA from 1.0×10^?13 to 1.0×10^?6 mol·L^?1 with a detection limit of 3.5×10^?14 mol·L^?1 (S/N=3). In addition, this DNA biosensor has good selectivity, and even can distinguish single‐mismatched target DNA.     

Amperometric Glucose Biosensor Based on Electrochemically Deposited Gold Nanoparticles Covered by Polypyrrole

Graphite rod (GR) modified with electrochemicaly deposited gold nanoparticles (AuNPs) and adsorbed glucose oxidase (GOx) was used in amperometric glucose biosensor design. Enzymatic formation of polypyrrole (Ppy) on the surface of GOx/AuNPs/GR electrode was applied in order to improve analytical characteristics and stability of developed biosensor. The linear glucose detection range for Ppy/GOx/AuNPs/GR electrode was dependent on the duration of Ppy‐layer formation and the linear interval was extended up to 19.9 mmol L⁻¹ after 21 h lasting synthesis of Ppy. The sensitivity of the developed biosensor was determined as 21.7 μA mM⁻¹ cm⁻², the limit of detection – 0.20 mmol L⁻¹. Ppy/GOx/AuNPs/GR electrodes demonstrated advanced good stability (the t _1/2 was 9.8 days), quick detection of glucose (within 5 s) in the wide linear interval. Additionally, formed Ppy layer decreased the influence of electroactive species on the analytical signal. Developed biosensor is suitable for the determination of glucose in human serum samples.     

A Reagentless Amperometric Immunosensor for Alpha‐Fetoprotein Based on Gold Nanoparticles/TiO2 Colloids/Prussian Blue Modified Platinum Electrode

A novel reagentless amperometric immunosensor for the determination of alpha‐fetoprotein (AFP) was prepared by immobilizing TiO₂ colloids on Prussian blue (PB) modified platinum electrode, which yielded a positively charged interface with strong adsorption to deposit gold nanoparticles for immobilization of alpha‐fetoprotein antibody (anti‐AFP). The factors influencing the performance of the proposed immunosensors were studied in detail. Under the optimized conditions, cyclic voltammograms determination of AFP showed a specific response in two concentration ranges from 3.0 to 30.0 ng/mL and from 30.0 to 300.0 ng/mL with a detection limit of 1.0 ng/mL at a signal‐to‐noise ratio of 3. The proposed immunosensor exhibited high selectivity, good reproducibility, long‐term stability (>2 months) and good repeatability.     

Lable‐Free Electrochemical DNA Sensor Based on Gold Nanoparticles/Poly(neutral red) Modified Electrode

We present a new strategy for the label‐free electrochemical detection of DNA hybridization based on gold nanoparticles (AuNPs)/poly(neutral red) (PNR) modified electrode. Probe oligonucledotides with thiol groups at the 5‐end were covalently linked onto the surface of AuNPs/PNR modified electrode via S‐Au binding. The hybridization event was monitored by using differential pulse voltammetry (DPV) upon hybridization generates electrochemical changes at the PNR‐solution interface. A significant decrease in the peak current was observed upon hybridization of probe with complementary target ssDNA, whereas no obvious change was observed with noncomplementary target ssDNA. And the DNA sensor also showed a high selectivity for detecting one‐mismatched and three‐mismatched target ssDNA and a high sensitivity for detecting complementary target ssDNA, the detection limit is 4.2×10^?12 M for complementary target ssDNA. In addition, the DNA biosensor showed an excellent reproducibility and stability under the DNA‐hybridization conditions.     

基于金纳米粒子/聚阿魏酸/多壁碳纳米管修饰电极的DNA计时库仑法生物传感器的制备

构建了基于金纳米粒子/聚阿魏酸/多壁碳纳米管(AuNPs/PFA/MWCNTs)修饰电极的DNA计时库仑法生物传感器.利用循环伏安技术在多壁碳管修饰的玻碳电极表面上聚合一层阿魏酸,在恒电位条件下,在阿魏酸表面沉积金纳米粒子,巯基DNA作为探针通过金硫键固定在金纳米粒子表面.电化学交流阻抗技术(EIS)与扫描电镜(SEM...     

天青Ⅰ为电子媒介体金纳米颗粒修饰葡萄糖生物传感器

用纳米金溶胶与聚乙烯醇缩丁醛(PVB)构成复合固酶基质,采用溶胶凝胶法固定葡萄糖氧化酶(GOx)于铂金电极表面,并在葡萄糖溶液中加入天青Ⅰ作为电子媒介体,制成了新型葡萄糖生物传感器。实验证明,葡萄糖氧化酶吸附在纳米金颗粒表面上稳定且保持其生物活性;而电子媒介体的存在,显著提高了传感器的响应灵敏度。该传感器对葡萄糖响应的线性范围为2.5×10-5～7.5×10-3mol/L;检出限为8.5×10-6mol/L(S/N=3)。该生物传感器用于人体血清中的葡萄糖测定,结果令人满意。     

A Simple Fluorometric Method Using Chlorophyll a for Determination of Hg2+ Ion

A simple and green analytical procedure based on chlorophyll a is presented for the determination of Hg²⁺ ion. Chlorophyll a was extracted and purified from the leaves of pea and is employed as a reagent for analysis of Hg²⁺ ion. It displays remarkable fluorescence emission at 674 nm when excited at 412 nm. The emission intensity decreased significantly on exposure to various concentrations of Hg²⁺ ion. This forms the basis for the determination of Hg²⁺ ion. The proposed method was evaluated for sensitivity and selectivity. The linear concentration range was found to be 2.0–10 μM with r² = 0.997 and the limit of detection for Hg²⁺ ion was 1.3 μM. Ions including Pb²⁺, Cd²⁺, Ag⁺, Zn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Mg²⁺, Mn²⁺, Ru³⁺, Er³⁺, K⁺, Na⁺, NH₄⁺, Cl⁻, NO₃⁻, CH₃COO⁻ and SO₄²⁻ did not interfere with the measurement of Hg²⁺ ion even at 500-fold excess. Since chlorophyll a is widely available in the leaves of most plants, and the extraction and purification process is simple, this technique can provide an alternative, sensitive and economical way to determine Hg²⁺ ion.     

Fabrication of Hemoglobin/Ionic Liquid Modified Carbon Paste Electrode Based on the Electrodeposition of Gold Nanoparticles/CdS Quantum Dots and Its Electrochemical Application

A novel H₂O₂ amperometric biosensor based on the electrodeposition of gold nanoparticles (AuNPs) and CdS quantum dots (CdS QDs) onto a carbon paste electrode (CPE) and immobilizing hemoglobin (Hb) with ionic liquid (IL), is presented in this article. The modification process of the electrode was monitored by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to synergistic effects of AuNPs, CdS QDs and IL, the biosensor exhibited high stability and good bioelectrocatalytic ability to H₂O₂ with a linear concentration range from 10 to 750 µM and a detection limit of 4.35 µM (S/N=3).     

Electrochemical Sensors Based on Au Nanoparticles Decorated Pyrene-Reduced Graphene Oxide for Hydrazine, 4-Nitrophenol and Hg2+ Detection in Water

Monitoring hazardous chemical compounds such as hydrazine (N₂H₄), 4-nitrophenol (4-NP) and Hg²⁺ in natural water resources is a crucial issue due to their toxic effects on human health and catastrophic impact on the environment. Electrochemical nanostructured platforms integrating hybrid nanocomposites based on graphene derivatives and inorganic nanoparticles (NPs) are of great interest for such a purpose. In this work, disposable screen-printed carbon electrodes (SPCEs) have been modified with a hybrid nanocomposite formed by reduced graphene oxide (RGO), functionalized by 1-pyrene carboxylic acid (PCA), and decorated by colloidal Au NPs. These hybrid platforms have been tested for the electrocatalytic detection of N₂H₄ and 4-NP by differential pulse voltammetry and have been modified with an electropolymerized film of Hg²⁺ ions imprinted polycurcumin for the electroanalytical detection of Hg²⁺ by DPV. LODs, lower and in line with the lowest ones reported for state-of-the-art electrochemical sensors, integrating similar Au-graphene < nanocomposites, have been estimated. Additionally, good repeatability, reproducibility, and storage stability have been assessed, as well as a high selectivity in the presence of a 100-fold higher concentration of interfering species. The applicability of the proposed platforms for the detection of the compounds in real complex matrices, such as tap and river water samples, has been effectively demonstrated.     

基于铂纳米颗粒电沉积镁铝水滑石修饰电极的电化学葡萄糖生物传感器

采用成核/晶化隔离法合成了镁铝水滑石纳米颗粒,将其修饰到氧化铟锡导电玻璃电极表面;在此修饰电极基础上,利用电沉积还原氯铂酸盐法制备了铂纳米颗粒/水滑石复合修饰电极.由于水滑石层板表面的外限域作用有效抑制了铂纳米颗粒的聚集,使该电极对过氧化氢具有较好的电催化性能.基于镁铝水滑石良好的生物相容性,将葡萄糖氧化酶进一步修饰到该电极表面,实现了对葡萄糖高灵敏的电化学检测,检出限(S/N=3)达1.0μmol/L.