Electrochemical Immunosensor for α‐Fetoprotein Based on Gold Nanoparticles/Graphene‐Prussian Blue

The electrochemical immunosensor for α‐fetoprotein (AFP) was fabricated based on the platform of gold nanoparticles (GNP)/graphene (Gr)‐prussian blue (PB). By electrodeposition, GNP were modified on the surface of the prepared Gr‐PB. The anti‐AFP‐1,1′‐ferrocenedicarboxylic acid (FcDA) as label was directly immobilized on the platform of GNP/Gr‐PB. And after the immunoreactions, the formed complex inhibited the electron transfer and decreased the catalytic current of FcDA toward the reduction of H₂O₂. And in the range of 10–3200 pg·mL^?1, the decreased current is linear with the concentration of AFP, with a detection limit of 3 pg·mL^?1. The developed immunoassay method showed good precision, high sensitivity, acceptable stability and reproducibility, and could be used for the detection of real samples with consistent results in comparison with those obtained by the enzyme linked immunosorbent assay (ELISA) method.     

基于聚硫堇/亚甲基蓝和纳米金放大的免疫传感器检测贝类毒素大田软海绵酸

采用聚硫堇(PTH)修饰电极为传感界面提供一个生物修饰功能基质膜,借助纳米金(GNPs)的导电性、生物相容性与高比表面积特性实现抗体的有效固定,并以亚甲基蓝(MB)为电子媒介加速电极表面电化学反应的电子传递,构建了一种高灵敏的非标记电化学免疫传感器,用于贝类毒素大田软海绵酸(OA)的检测。当分子结构中含有羧基和酚基的OA与其抗体特异性结合后,生成以阴离子形式存在的抗原-抗体复合物,阻碍了传感器表面电子的传递,导致峰电流下降。利用免疫反应前后峰电流的变化,可对OA进行特异性识别和准确定量。在优化实验条件下,OA浓度的对数在0.2~100 μg/L范围内与其峰电流的变化值(ΔI)呈线性相关,线性方程为ΔI=1.721 7+1.083 6lgρ,相关系数为0.992 0,检出限为0.1 μg/L。该免疫传感器重现性好、特异性强,用于实际贝类样品的测定,回收率为85.3%~112%。     

石墨烯-壳聚糖复合物修饰电极构建电化学免疫传感器对1-芘丁酸的检测研究

采用石墨烯(GS)和壳聚糖(CS)复合膜修饰玻碳电极(GS-CS/GCE),利用1-乙基-(3-二甲基氨基丙基)碳二亚胺盐酸盐(EDC)和N-羟基丁二酰亚胺(NHS)(4∶1)活化GS-CS/GCE,共价固定多环芳烃抗体(anti-PAHs),构建灵敏度高、稳定性好的非标记电流型免疫传感器,用于1-芘丁酸(PBA)的检测。运用扫描电子显微镜对GS-CS复合膜的形貌进行表征。在pH 7.0含10 mmol/L K3Fe(CN)6和0.1 mmol/L KCl的磷酸盐溶液中,通过循环伏安法和示差脉冲伏安法研究修饰电极表面的电化学性质,并考察了免疫传感器的电化学性能。研究表明,由于石墨烯和壳聚糖的协同作用,GS-CS修饰的玻碳电极在Fe(CN)64-/3-溶液中的峰电流明显增大,有利于提高免疫传感器的灵敏度。在优化实验条件下,电极表面的anti-PAHs抗体固定量显著提高,增强了电极的分子识别性能。由于anti-PAHs抗体-抗原结合物的导电性较差,免疫传感器的峰电流随着待测溶液中PBA浓度的增大而减小,PBA浓度在0.1～80μg/L范围内呈良好的线性关系,检出限为0.03μg/L。该免疫传感器重现性好、特异性强,用于实际样品的测定,回收率为90%～105%。     

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.     

基于新型聚钙羧酸修饰电极的甲胎蛋白电化学免疫传感器研究

通过电聚合制得新型聚钙羧酸修饰电极并用于构建检测甲胎蛋白（AFP）的高灵敏电化学免疫传感器. 采用扫描电镜（SEM）、电化学交流阻抗（EIS）观察、表征修饰电极和AFP单克隆抗体（Ab1）固定前后的差异. 固定Ab1的电极与一定浓度的AFP、辣根过氧化物酶联AFP单克隆抗体（HRP-Ab2）反应,形成夹心型免疫复合物. 辣根过氧化物酶（HRP）催化3,3',5,5'-四甲基联苯胺（TMB）底物产生电流信号,实现AFP浓度的测定. 本检测方法灵敏度高,重现性好.     

An Electrochemical Impedance Immunosensor Based on Gold Nanoparticle‐Modified Electrodes for the Detection of HbA1c in Human Blood

A label‐free immunosensor for the detection of HbA1c was developed based on gold nanoparticle (AuNP)‐aryl diazonium salt modified glassy carbon (GC) electrode where transduction is achieved using electrochemical impedance spectroscopy (EIS). GC electrodes were first modified with 4‐aminophenyl (Ph‐NH₂) layers to which AuNPs were attached. Thereafter an oligo(ethylene glycol) (OEG‐COOH) species were covalently attached to the remaining free amine groups on the Ph‐NH₂ surface. The AuNP surfaces were further modified with Ph‐NH₂ followed by attachment of a glycosylated pentapeptide (GPP), an analogon to HbA1c. Exposure of this interface to anti‐HbA1c IgG resulted in a change in charge transfer resistance (R_ct) due to the anti‐HbA1c IgG selectively complexing to the surface bound GPP. To detect the amount of HbA1c, a competitive inhibition assay was employed where the surface bound GPP and HbA1c in solution compete for the anti‐HbA1c IgG antibodies. The higher the concentration of HbA1c, the less antibody binds to the sensing interface and the lower the change of R_ct. The response of the immunosensor is linear with the HbA1c% of total haemoglobin in the range of 0%–23.3%. This competitive inhibition assay can be used for the detection of HbA1c in human blood. The performance of the immunosensor for detection of HbA1c in human blood is comparable to the clinical laboratory method.     

基于普鲁士蓝-碳纳米管-纳米金复合材料的电化学免疫传感器的构建

构建一个基于普鲁士蓝–碳纳米管–纳米金复合物(PB–CNTs–CNPs)增效的新型免疫传感器检测大肠杆菌。普鲁士蓝–碳纳米管–纳米金复合物能够增强电子的传递效率和电极的稳定性。当大肠杆菌抗存在时,辣根过氧化氢酶(HRP)标记的大肠杆菌抗体也通过特异性作用结合到PB–CNTs–CNPs修饰的金电极表面,形成一个夹心型结构。通过大肠杆菌抗体上标记的HRP酶催化底夜中双氧水的还原对大肠杆菌进行定量。该传感器具有很好的特异性、重现性和稳定性。在最优条件下,大肠杆菌浓度在10~1×107 cfu/mL的范围内与该传感器的电流响应I存在I=33.68 lg C_(E.coli)+7.19的线性关系,检出限为9.2 cfu/mL(S/N=3)。将该传感器应用于实际样品中大肠杆菌的检测,样品加标回收率为91.3%~103.0%,与平板计数法的实验结果相比较,结果具有高度一致性。     

Characterization of Formation Kinetics of Self-Assembled Thiol Monolayers on Gold by Electrochemical Impedance Spectroscopy

Interest in the properties of organized monolayers has grown enormously in recent years because these monolayers can provide a means to control the interface at a molecular level1. The self-assemblies of alkanethiols and their derivatives were probably the most intensively studied due to their stability, well-packed structure, ease in preparation, and flexibility in designing the tail group2. The adsorption kinetics of thiol monolayer has been studied by using several techniques, including con…     

Highly Sensitive Electrochemical Immunosensor Based on Mesoporous PdPt Nanoparticles Anchored on a Three-dimensional PANI@CNTs Network as Nanozyme Labels

In this study, a novel strategy to amplify electrochemical signals by mesoporous PdPt nanoparticles with core-shell structures anchored on a three-dimensional PANI@CNTs network as nanozyme labels (PdPt/PANI@CNTs) was proposed for the sensitive monitoring of α-fetoprotein (AFP, Ag). First, the mesoporous PdPt nanoparticles prepared by a facile chemical reduction method had excellent biocompatibility with biomolecules, which could capture a large amount of AFP-Ab₂ (Ab₂) and exhibit plentiful pores to entrap more thionine (Thi) into mesoporous PdPt nanoparticles with enhanced loading and abundant active sites. Furthermore, the resulting mesoporous PdPt nanoparticles were abundantly dotted on the surface of a three-dimensional PANI@CNTs network with excellent conductivity and a high specific surface area through the bonding of the amino group to form PdPt/PANI@CNTs nanozyme labels. Most importantly, the as-prepared PdPt/PANI@CNTs nanozyme labels exhibited unexpected enzyme-like activity towards the reduction of hydrogen peroxide owing to the highly indexed facets, enhancing the current response to realize signal amplification. In view of the advantages of nanozyme labels and the involvement of gold nanoparticles (AuNPs, which behave as electrode materials) for the sensitive determination of AFP, the as-developed immunosensor could obtain a dynamic working range of 0.001 ng mL^−1–100.0 ng mL⁻¹ at a detection limit of 0.33 pg mL⁻¹ via DPV (at 3σ). Furthermore, the nanozyme-based electrochemical immunosensor exhibited remarkable analytical performance, which brought about feasible ideas for disease diagnosis in the future.     

Si／C复合材料电极首次嵌锂过程的电化学阻抗谱研究

采用球磨法制备了Si／C复合材料,X射线衍射（XRD）和扫描电子显微镜（SEM）测试结果显示Si／C复合材料中硅保持着良好的晶体结构且均匀的分散于炭黑基体中．充放电测试结果表明Si／C复合材料首次放电容量高达3393mAh／g,4周之后可逆容量均保持在1000mAh／g左右,表现出较好的循环性能．电化学阻抗谱测试结果显...     

以聚吡咯和纳米金为基质基于电化学交流阻抗测试的乙肝表面抗原免疫传感器研究

A novel simple immunosensing strategy for fabrication of hepatitis B surface antigen detection has been developed via electrochemical impedance spectroscopy （EIS） as a platform. At first, the conductive polymer polypyrrole （PPy） film was electrodeposited on a platinum electrode surface to adsorb the gold nanoparticles （nano-Au） via the opposite-charged adsorption technique, and then hepatitis B surface antibodies were adsorbed onto the surface of nano-Au. The modification procedure was characterized by EIS. Such spectroscopy is attributed to the concomitant conductivity changes of the polymerized pyrrole film and gold nanoparticles. The factors influencing the performance of resulting immunoelectrode were studied in detail. The linear range of the resulting immunoelectrode is from 2.6 to 153.6 ng.mL^-1 with a detection limit of 1.3 ng·mL^-1 at 3σ. In addition, the experiment results indicate that antibody immobilized on this way exhibits a good sensitivity, selectivity, high stability and a long-term maintenance of bioactivity, implying a great promising alternative approach for reagentless immunosensing analysis in the clinical diagnosis.     

BisPNA‐assisted Detection of Double‐stranded DNA via Electrochemical Impedance Spectroscopy

A highly effective strategy for quantification of plasmid which was a special dsDNA based on bisPNA by electrochemical impedance spectroscopy was presented in this work. Firstly, through Au?S bond, thiol‐terminated bisPNA probes were immobilized onto the gold electrode surface. Then bisPNA probes directly hybridized with target plasmid DNA pBR322 based on the PNA.DNA‐PNA invasion triplex without denaturation. In the presence of redox electroactive ions [Fe(CN)₆]^3?/4? as hybridization indicator, the charge transfer resistance (R_ct) was produced, and R_ct was measured via electrochemical impedance spectroscopy. Under optimal conditions, this strategy showed a good linear relationship between the ΔR_ct which was the difference of R_ct obtained before and after bisPNA hybridized with plasmid pBR322, and logarithm of the concentration of plasmid pBR322 within the range from 1 nM to 100 nM (R²=0.993), with a limit of detection (LOD) of 0.1 nM. Furthermore, this bisPNA‐assisted biosensor showed good stability and satisfactory analytical reliability. In addition, this novel bisPNA‐assisted biosensor also exhibited excellent analytical results in human serum.     

Impedimetric Biosensor for Bovine Herpesvirus Type 1‐Antigen Detection

The bovine herpesvirus type 1 (BHV‐1) is a pathogen of great economic impact for livestock, which is related multi‐systemic infections that leads to mortality or morbidity of cattles. Thus, the search for cheap and practical methodologies that allow the selective detection of BHV‐1 antigen (BHV‐1 AG) is of utmost relevance. Therefore, an impedimetric label‐free immunosensor was herein, developed and its performance evaluated in biological samples enriched with BHV‐1 AG. Briefly, the biosensor construction was based on the immobilization of BHV‐1 antibody (BHV‐1 AB) and casein on the activated glassy carbon electrode surface. The BHV‐1 AB was isolated from egg yolk of immunized chickens, which is a less stressful protocol. The bio sensing principle was based on Electrochemical Impedance Spectroscopy by using Fe(CN)₆^4?/3? probe, which were also used to check variation of charge transfer resistance (?R_ct), when the electrode surface was increasingly blocked by immune complex. A linear relationship between ?R_ct and BHV‐1 AG concentration was verified in the range from 10 to 50 TCID₅₀ mL^?1, with LOQ of 2.00 TCID₅₀ mL^?1 and LOD of 0.66 TCID₅₀ mL^?1. Besides the suitable sensitivity, the immunosensor displayed accuracy, stability, and specificity to detect BHV‐1 AG in biological samples of serum, nasal secretions, semen and urine. Moreover, to the best of our knowledge this is the first immunosensor applied to BHV‐1 diagnostic.     

基于纳米金固定半抗原的电化学免疫传感器灵敏检测克伦特罗

研制了一种基于纳米金固定半抗原的间接竞争电化学免疫传感器,可灵敏检测克伦特罗.在金电极表面组装1,6-己二硫醇单分子膜,通过Au-S共价作用连接纳米金颗粒,通过吸附作用固定克伦特罗牛血清白蛋白偶联物.样品中的待测组分与固定化的克伦特罗偶联物竞争结合单克隆抗体,碱性磷酸酯酶标记的二抗选择性地与电极表面捕获的一抗反应,进而催化底物1-萘酚磷酸酯水解生成1-萘酚,在电极表面氧化产生电信号.在优化的实验条件下,克伦特罗浓度在0.1～1000 μg/L范围内与电流强度线性相关,线性方程为I(A)-8.79× 10-7-2.66× 10-7logC (μg/L),相关系数0.9960,检出限达20 ng/L.同时测定了猪肉及猪肝样品中克伦特罗含量,相对标准偏差平均值为7.0％,加标回收率在89.1％～105.6％之间,与传统的间接竞争酶联免疫吸附法对照,结果无显著性差异.     

基于纳米金／壳聚糖掺杂碳纳米管修饰金电极非标记免疫传感器的研究

应用吸附法将羊抗人IgG抗体直接固定于纳米金(GNPs)/壳聚糖(Chit)掺杂碳纳米管(CNTs)修饰的金电极表面,制备了用于人IgG抗原检测的非标记电化学免疫传感器.利用循环伏安法和交流阻抗研究了修饰电极表面的电化学特性,用差分脉冲伏安法研究了测试底液的pH值对免疫传感器性能的影响.实验表明,在含不同浓度人IgG的...     

基于碳纳米管和离子液体复合物修饰电极的免疫传感器检测莱克多巴胺

建立了一种新的电化学免疫传感器方法, 将多壁碳纳米管(MWCNTs)和室温离子液体1-丁基-3-甲基咪唑四氟硼酸盐([BMIM]BF₄)复合物, 和偶联了牛血清蛋白(BSA)的莱克多巴胺抗原, 使用Nafion固定在电极上, 利用莱克多巴胺抗体和抗原之间特定反应的竞争模式, 以K₃Fe(CN)₆为探针, 通过循环伏安法和差分脉冲伏安法监测免疫反应, 对溶液中莱克多巴胺的浓度进行检测. 线性范围宽(1～1500 ng/mL), 检测限可低至0.3 ng/mL. 同时, 我们对猪饲料实际样品进行测定, 回收率令人满意.     

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.     

Electrochemical Impedance Spectroscopic Investigation in Detecting 2,4‐dinitrophenylhydrazine Using Catalytic Effect of Copper at Glassy Electrode

This paper reports on the use of electrochemical impedance spectroscopy (EIS) allied to copper (II) for the determination of 2,4‐dinitrophenylhydrazine (DNPH) at glassy carbon electrode (GCE). The experiment measurements were carried out in methanol at a potential of 0.3 V versus Ag/AgCl. The Nyquist plots were modeled with a Randle equivalent circuit, by identifying the charge transfer resistance as the relevant concentration dependent parameter. These measurements show that the impedance spectra of DNPH increased by the formation of non‐electroactive compound produced from specific interaction between DNPH and Cu (II), which will block the electron‐transfer process of the redox probe. Therefore, the proposed methodology offers a detection limit of 4.0×10^?8 mol L^?1. The proposed methodology was satisfactorily applied to determine DNPH in industrial water samples.     

Electrochemical Impedance Spectroscopy of Oxide Layers on the Titanium Surface

The method of electrochemical impedance spectroscopy is used to study oxide layers formed at the titanium surface by a variety of methods. The sample’s polarization permitted the isolation, in an impedance spectrum, of the response caused by the capacitance of the space-charge region, which obeys the Mott-Schottky dependence. It is established that the high-frequency portion of an impedance spectrum is defined by morphological peculiarities of the porous portion of coatings. Assumptions, concerning the nature of a time constant, which reveals itself in the region of low frequencies at polarizing biases, are made. Equivalent circuits, intended for modeling impedance spectra, are proposed. The circuits take into consideration the effect of the space-charge region, as well as the peculiarities of the structure and morphology of the oxide film formed at the titanium surface.__________Translated from Elektrokhimiya, Vol. 41, No. 8, 2005, pp. 963–971.Original Russian Text Copyright © 2005 by Gnedenkov, Sinebryukhov.     

Label‐free Electrochemical Immunosensor for Cardiac Troponin T Based on Exfoliated Graphite Nanoplatelets Decorated with Gold Nanoparticles

This paper describes the application of exfoliated graphite nanoplatelets (xGnP) decorated with gold nanoparticles (AuNP) for the development of a label‐free electrochemical immunosensor for the determination of human cardiac troponin T (TnT), an important cardiac biomarker in the diagnosis of acute myocardial infarction (AMI). Heparin‐stabilized AuNP (AuNP‐Hep) were synthesized, characterized and supported on xGnP. The material obtained (AuNP‐Hep‐xGnP) was used as a platform to immobilize the anti‐TnT by adsorption and this was then applied in the construction of an immunosensor. Under optimized conditions, using differential pulse voltammetry (DPV) and an incubation time of 20 min, the proposed immunosensor showed linearity in the range of 0.050 to 0.35 ng mL⁻¹ TnT, with a calculated limit of detection of 0.016 ng mL⁻¹. The interday precision (n=7) showed a coefficient of variation of 6.5 %. Some potential interferents commonly present in blood plasma samples were investigated and the degree of interference was found to be low (less than 10 %), demonstrating adequate selectivity for analytical applications. The biosensor was successfully applied in the determination of TnT in fortified samples of human blood plasma.