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An ultrasensitive sandwich-type electrochemical immunosensor was designed for the quantitative detection of alpha fetoprotein (AFP). The β-cyclodextrins functionalized graphene sheets (CD-GS) were used as the sensing matrix for immobilizing adamantine-1-carboxylic acid functionalized primary anti-AFP (ADA–Ab 1 ) and enhanced the electron transfer. PdNi alloy nanoparticles decorated N-doped graphene nanoribbons (PdNi/N-GNRs) were used as labels of secondary anti-AFP (Ab 2 ), and PdNi alloy nanoparticles (PdNi NPs) exhibited high catalytic performance towards the reduction of H 2 O 2 . Meanwhile, with good dispersion, large specific surface area and good catalytic performance, N-doped graphene nanoribbons (N-GNRs) significantly amplified the electrochemical signal. Under the optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.0001–16 ng/mL with a low detection limit of 0.03 pg/mL. Additionally, the proposed immunosensor showed high specificity, good reproducibility and long-term stability, which have promising application in bioassay analysis. [ABSTRACT FROM AUTHOR]

A novel and sensitive electrochemical immunosensor for ultrasensitive detection of pancreatic cancer biomarker carbohydrate antigen 199 (CA199) was proposed by using Au@Cu x OS yolk–shell nanostructures with porous shells as labels for signal amplification. Au@Cu x OS yolk–shell nanostructures exhibit high electrocatalytic activity toward the reduction of hydrogen peroxide (H 2 O 2 ) as analytical signal. Moreover, secondary antibody (Ab 2 ) can adsorb on the surface of Au@Cu x OS with porous shells which has large surface area and could greatly increase the probability of Ab 2 –antigen interactions thereby leading to higher sensitivity. Reduced graphene oxide–tetraethylene pentamine (rGO–TEPA), containing abundant amine groups, was supported Au nanoparticles as a support platform to immobilize the primary antibody (Ab 1 ). The resulting sensing interface of rGO–TEPA/AuNPs could provide a large electroconductive surface area, allowing high loadings of the biological recognition elements as well as the occurrence of electrocatalytic and electron-transfer processes. Under optimal conditions, the immunosensor exhibited a wide linear response to CA199 ranging from 0.001 to 12 U/mL with a low detection limit of 0.0005 U/mL. The designed immunosensor displayed good precision, high sensitivity, acceptable stability and reproducibility, and has been applied to the analysis of serum with satisfactory results. The proposed method provides a new promising platform of clinical immunoassay for other biomolecules. [ABSTRACT FROM AUTHOR]

Abstract: A novel and sensitive sandwich electrochemical biosensor based on the amplification of magnetic microbeads and Au nanoparticles (NPs) modified with bio bar code and PbS nanoparticles was constructed in the present work. In this method, the magnetic microspheres were coated with 4 layers polyelectrolytes in order to increase carboxyl groups on the surface of the magnetic microbeads, which enhanced the amount of the capture DNA. The amino-functionalized capture DNA on the surface of magnetic microbeads hybridized with one end of target DNA, the other end of which was hybridized with signal DNA probe labelled with Au NPs on the terminus. The Au NPs were modified with bio bar code and the PbS NPs were used as a marker for identifying the target oligoncleotide. The modification of magnetic microbeads could immobilize more amino-group terminal capture DNA, and the bio bar code could increase the amount of Au NPs that combined with the target DNA. The detection of lead ions performed by anodic stripping voltammetry (ASV) technology further improved the sensitivity of the biosensor. As a result, the present DNA biosensor showed good selectivity and sensitivity by the combined amplification. Under the optimum conditions, the linear relationship with the concentration of the target DNA was ranging from 2.0×10−14 M to 1.0×10−12 M and a detection limit as low as 5.0×10−15 M was obtained. [Copyright &y& Elsevier]

Abstract A high sensitivity photoelectrochemical (PEC) immunosensor for amyloid beta (Aβ) detection, which has great neurotoxic effect on the progression of Alzheimer's disease (AD), was presented based on the sensitization of Mn2+ doped CdSe (Mn:CdSe) to Bi 2 WO 6 /CdS electrode. Bi 2 WO 6 was synthesized successfully with a unique flower-like amorphous structure, providing a merit to load functional CdS for obtaining an expected PEC response. Mn:CdSe was used to label Aβ for acquiring Mn:CdSe-Aβ bioconjugate and enhancing the detection sensitivity via the competitive immunoreaction of Mn:CdSe-Aβ and Aβ with antibody immobilized on Bi 2 WO 6 /CdS electrode. The doped of Mn2+ in CdSe nanoparticles could induce energy defect that impeded the recombination of photo-generated charges, and greatly enhanced PEC response for ultrasensitive detection of Aβ. The proposed immunosensor for Aβ showed a linear range of 0.2 pg mL−1–50 ng mL−1 with a detection limit of 0.068 pg mL−1, also with good stability, high selectivity, and acceptable reproducibility. The sensitization of Mn:CdSe provided a new way for preparation of highly sensitive protein biosensors. Highlights • A novel PEC immunosensor for ultrasensitive detection of Aβ was proposed at Bi 2 WO 6 /CdS modified electrode. • Aβ was labeled with Mn2+ doped CdSe for signal amplification. • The sensitization of Mn:CdSe to Bi 2 WO 6 /CdS remarkably enhanced the PEC intensity. • The biosensor for Aβ exhibited the detection limit of 0.068 pg mL−1. [ABSTRACT FROM AUTHOR]

Titanium-zirconium-molybdenum (TZM) alloy was fabricated by using powder metallurgy and rolling techniques. Electrochemical corrosion behavior of the alloy was studied quantitatively using potentiodynamic polarization and scanning electron microscope. Effect of different chloride ions concentrations on corrosion resistance and electrochemical corrosion mechanism on TZM alloy was investigated. Results show that pitting corrosion and intergranular corrosion of TZM alloy mainly occurs in sodium chloride solution. Corrosion generates firstly in the form of pitting corrosion around second phase particles and increases with corrosive media Cl − concentration increasing, and then the intergranular corrosion occurs along grain boundaries and defects. Cl − corrosion can effectively destroy the passive film formed on the sample surface. As the Cl − concentration of corrosive media increases, the corrosion rate of TZM alloy increases until 1.0 mol/L and then decreases. TZM alloy exhibits good corrosion resistance when the concentration of Cl − in corrosive media is 0.5 mol/L or 1.5 mol/L. [ABSTRACT FROM AUTHOR]

A novel non-enzymatic immunoassay was designed for ultrasensitive electrochemical detection of carcino-embryonic antigen (CEA) using β-cyclodextrin functionalized Cu@Ag (Cu@Ag-CD) core–shell nanoparticles as labels and β-cyclodextrin functionalized graphene nanosheet (CD-GN) as sensor platform. CD-GN has excellent conductivity which promoted the electric transmission between base solution and electrode surface and enhanced sensitivity of immunosensor. In addition, owing to supramolecular recognition of CD-GN for the guest molecule, quite a few synthesized adamantine-modified primary antibodies (ADA-Ab 1 ) were immobilized on the CD-GN by supramolecular host–guest interaction between CD and ADA. Cu@Ag-CD as a signal tag could be captured by ADA-modified secondary antibody (ADA-Ab 2 ) through a host–guest interaction, leading to a large loading of Cu@Ag nanoparticles with high electrical conductivity and catalytic activity. The fabricated immunosensor exhibits excellent analytical performance for the measurement of CEA with wide range linear (0.0001–20 ng/mL), low detection limit (20 fg/mL), good sensitivity, reproducibility and stability, which provide an enormous application prospect in clinical diagnostics. [ABSTRACT FROM AUTHOR]

Abstract: Constructions of versatile electroactive labels are key issues in the development of electrochemical immunosensors. In this study, copper-doped titanium dioxide nanoparticle (Cu@TiO2) was synthesized and used as labels for fabrication of sandwich-type electrochemical immunosensors on glassy carbon electrode (GCE). Due to the presence of copper ions, Cu@TiO2 shows a strong response current when coupled to an electrode. The prepared nanocomposite also shows high electrocatalytic activity towards reduction of hydrogen peroxide (H2O2). The dual functionality of Cu@TiO2 enables the fabrication of immunosensor using different detection modes, that is, square wave voltammetry (SWV) or chronoamperometry (CA). While Cu@TiO2 was used as labels of secondary antibodies (Ab2), carboxyl functionalized graphene oxide (CFGO) was used as electrode materials to immobilize primary antibodies (Ab1). Using human immunoglobulin G (IgG) as a model analyte, the immunosensor shows high sensitivity, acceptable stability and good reproducibility for both detection modes. Under optimal conditions, a linear range from 0.1pg/mL to 100ng/mL with a detection limit of 0.052pg/mL was obtained for SWV analysis. For CA analysis, a wider linear range from 0.01pg/mL to 100ng/mL and a lower detection limit of 0.0043pg/mL were obtained. The proposed metal ion-based enzyme-free and noble metal-free immunosensor may have promising applications in clinical diagnoses and many other fields. [Copyright &y& Elsevier]