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Interferon gamma (IFN‐γ) released by T lymphocytes, plays an important role in immune regulation and is also an important biomarker for the early diagnosis of bovine tuberculosis. In this work, an electrochemical immunosensor based on gold nanoparticles (AuNPs)/chitosan composite was developed for highly sensitive determination of bovine IFN‐γ. AuNPs/chitosan composite shows high surface area and good hydrophilicity. The bovine IFN‐γ immunosensor was prepared by immobilizing IFN‐γ antibody on AuNPs/chitosan composite‐modified glassy carbon electrode. The immunosensors were characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry (CV). Using horseradish peroxidase (HRP)‐labeled IFN‐γ antibody as amplification probe, the concentration of bovine IFN‐γ can be monitored via the increasing current signal, which can be attributed to the specific immune binding between bovine IFN‐γ antigen and HRP‐labeled IFN‐γ antibody, as well as the efficient catalysis reaction between thionine and HRP with the presence of H2O2. The developed electrochemical immunosensor exhibited a wide linear range of 0.01 to 30 ng/mL, and low detection limit of 0.003 ng/mL with good specificity and stability. This study provides a simple and promising method for diagnosis of bovine tuberculosis, which can be expanded to determine other biomarkers. [ABSTRACT FROM AUTHOR]

A novel nanorod-like MoS2 semiconductor nanostructure was synthesized through a simple two-step method. The nanorod-like MoS2 nanostructure was exploited as an electrode material to immobilize enzymes and for electrochemical sensing application. Characterization of the nanorod-like MoS2 nanostructure and the resultant biosensor was performed by scanning electron microscopy, Fourier transform infrared spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. Enzyme molecules loaded at the MoS2 nanostructure retained their native structure and bioactivity. The direct electron transfer of glucose oxidase at the MoS2 nanostructure coated glassy carbon electrode was enhanced greatly. At an optimal potential of −0.45 V, the electrochemical glucose sensor had wide linear ranges of 1.5 × 10−5–3.25 × 10−4 M and 3.25 × 10−4–1.43 × 10−3 M, and a low detection limit of 0.005 mM (S/N = 3) with a high sensitivity of 25.06 ± 0.5 mA M−1 cm−2. At the same time, the present biosensor showed excellent selectivity, reproducibility and stability for glucose. What's more, the biosensor was successfully applied to the determination of practical samples. [ABSTRACT FROM AUTHOR]

In this research, a novel manganese dioxide nanorod-anchored graphene oxide (MnO2 NRs/GO) composite was synthesized by a simple hydrothermal method for electrochemical sensing application. A highly sensitive electrochemical sensor for dopamine (DA) was constructed by modifying glassy carbon electrode (GCE) with MnO2 NRs/GO. The morphology and performance of the composite material and modified GCEs were investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV), respectively. The resultant MnO2 NRs/GO composite has a large electroactive area and shows excellent electrochemical activity toward DA. Under the optimal conditions, the DA sensor shows a linear response in the DA concentration ranges of 0.1 μM–0.08 mM and 0.08–0.41 mM with a low detection limit of 0.027 μM and a high sensitivity of 602.4 μA·mM−1·cm−2. The MnO2 NRs/GO composite provides a promising platform for the construction of a highly sensitive and selective sensor of DA. [ABSTRACT FROM AUTHOR]

A cage-like PbS nanostructure was functionalized with platinum nanoparticles, and the resulting material (PtNP@PbS) was deposited on a glassy carbon electrode in order to study the direct electron transfer to FADH in glucose oxidase (GOx) and further to construct a glucose biosensor. The PtNP@PbS nanostructure and the biosensor were characterized using scanning electron microscopy, UV-vis and electrochemical impedance spectroscopy, and by cyclic voltammetry. Compared to the use of cage-like PbS alone, the PtNP@PbS nanostructure shows much higher electrochemical activity and an enhanced direct electron transfer rate. The GOx loaded onto the nanostructure displays good enzymatic activity and an apparent electron transfer rate constant of 3.0 s. The glucose biosensor is operated best at −0.4 V (vs. SCE) and then exhibits a linear range that extends from 4 μM to 1.1 mM, with a detection limit as low as 1 μM (at an S/N ratio of 3). The biosensor is selective, acceptably repeatable and stable. It was applied to the determination of glucose in human serum samples. [ABSTRACT FROM AUTHOR]

We describe a highly sensitive electrochemical enzymatic glucose biosensor. A glassy carbon electrode was modified with cylinder-shaped titanium dioxide nanorods (TiO-NRs) for the immobilization of glucose oxidase. The modified nanorods and the enzyme biosensor were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The glucose oxidase on the TiO-NRs displays a high activity and undergoes fast surface-controlled electron transfer. A pair of well-defined quasi-reversible redox peaks was observed at −0.394 and −0.450 V. The TiO-NRs provide a good microenvironment to facilitate the direct electron transfer between enzyme and electrode surface. The biosensor has two linear response ranges, viz. from 2.0 to 52 μM, and 0.052 to 2.3 mM. The lower detection limit is 0.5 μM, and the sensitivity is 68.58 mA M cm. The glucose biosensor is selective, well reproducible, and stable. In our perception, the cylindrically shaped TiO-NRs provide a promising support for the immobilization of proteins and pave the way to the development of high-performance biosensors. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Biomorphic calcium phosphate (CaP) microspheres with hierarchical porous structure were synthesized using natural cole pollen grains as templates and were further employed for the immobilization of horseradish peroxidase (HRP). Scanning electron microscopy and Fourier transform infrared spectroscopy revealed (a) the porous structure of the CaP microspheres, (b) the effective immobilization, and (c) the retention of the conformation of HRP on CaP. The immobilized HRP was placed on a glassy carbon electrode where it underwent a direct, fully reversible, and surface-controlled redox reaction with an electron transfer rate constant of 1.96 s. It also exhibits high sensitivity to the reduction of HO The response to HO is linear in the 5.00 nM to 1.27 μM concentration range, and the sensitivity is 30357 μA⋅mM⋅cm. The detection limit (at an SNR of 3) is as low as 1.30 nM. The apparent Michaelis-Menten constant ( K) of the immobilized enzyme is 0.92 μM. This new CaP with hierarchical porous structure therefore represents a material that can significantly promote the direct electron transfer between HRP and an electrode, and is quite attractive with respect to the construction of biosensors. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Urchin-like InS nanostructures were functionalized with multi-walled carbon nanotubes (MWCNTs) and deposited on a glassy carbon electrode (GCE) to obtain a new kind of sensor for dopamine (DA). The new electrode was characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, cyclic voltammetry and differential pulse voltammetry. It is found that the current response toward DA is significantly enhanced compared to that of a bare GCE or a GCE modified with MWCNTs. The peak separation between DA and ascorbic acid (AA) is up to 225 mV. The new electrode also has improved selectivity for DA over AA compared to the bare electrode. The new DA sensor has a wide linear range (0.5-300 μM), high sensitivity (594.9 μA mM cm) and low detection limit (0.1 μM). CNTs wrapped on urchin-like nanostructures remarkable improve its electrocatalytic activity and thus provide a promising strategy to develop excellent composite materials for electrochemical sensing. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: A novel urchin-like In2O3–chitosan modified glassy carbon electrode (GCE) is for the first time prepared. The direct electrochemistry of glucose oxidase (GOD) immobilized on the surface of modified GCE and biosensing are studied. The urchin-like In2O3 nanostructure-based matrix has large specific surface area and provides a favorable and biocompatible microenvironment for promoting the direct electron transfer between proteins and electrode surface. The properties of different modified electrode are characterized by scanning electron microscopy (SEM), electrochemical impedance spectra (EIS), UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry, respectively. The constructed glucose biosensor shows wide linear range (5.0×10−6 to 1.3×10−3 M), low detection limit (1.9×10−6 M), a Michaelis–Menten constant of 0.37mM. The proposed biosensor has good sensitivity, excellent selectivity, good reproducibility and stability. This urchin-like In2O3–chitosan matrix provides a new approach and efficient matrix for the direct electrochemistry of proteins and developing novel types of biosensors. [Copyright &y& Elsevier]

Abstract: A novel biosensor is developed based on immobilization of proteins on nanoflake-like SnS2 modified glass carbon electrode (GCE). With glucose oxidase (GOD) as a model, direct electrochemistry of the GOD/nanoflake-like SnS2 is studied. The prepared SnS2 has large surface area and can offer favorable microenvironment for facilitating the electron transfer between protein and electrode surface. The properties of GOD/SnS2 are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry (CV), respectively. The immobilized enzyme on nanoflake-like SnS2 retains its native structure and bioactivity and exhibits a surface-controlled, reversible two-proton and two-electron transfer reaction with the apparent electron transfer rate constant (k s) of 3.68s−1. The proposed biosensor shows fast amperometric response (8s) to glucose with a wide linear range from 2.5×10−5 M to 1.1×10−3 M, a low detection limit of 1.0×10−5 M at signal-to-noise of 3 and good sensitivity (7.6±0.5mAM−1 cm−2). The resulting biosensor has acceptable operational stability, good reproducibility and excellent selectivity and can be successfully applied in the reagentless glucose sensing at −0.45V. It should be worthwhile noting that it opens a new avenue for fabricating excellent electrochemical biosensor. [Copyright &y& Elsevier]

Three-dimensional Cu@Cu2O aerogels with excellent electrocatalytic activity were prepared and used as electrode matrix for constructing novel electrochemical glucose sensors. The aerogels were obtained by adding a fresh solution of NaBH4 into a mixture of CuCl2 and NaOH aqueous solutions under stirring at room temperature. The aerogels were assembled with Cu or Cu2O nanoparticles. The materials show superfine spongy-like structures with large surface-to-volume ratio, numerous active sites and good solubility. The Cu@Cu2O aerogels show highly efficient electrochemical activity toward glucose oxidation with a relatively low-onset potential (0.25 V) in 0.1 M NaOH solution. This non-enzymatic glucose sensor offers a low detection limit of 0.6 μM (S/N = 3), a high sensitivity (195 mA M−1 cm−2), and two wide linear ranges (0.001-5.2 mM, 5.2-17.1 mM) at a working voltage of 0.6 V (vs. Ag/AgCl) in alkaline solution. While in neutral pH values, the respective data are a linear analytical range from 0.1 to 10 mM; a detection limit of 54 μM (S/N = 3) and a sensitivity of 12 mA M−1 cm−2 at scan rate of 100 mV s−1. The sensor possesses high selectivity, good reproducibility and long-time stability. It was utilized to determine glucose levels in (spiked) human serum samples, and satisfactory results were obtained.Schematic presentation of a glassy carbon electrode modified with 3D porous Cu@Cu2O aerogels. The aerogels were obtained by a reduction reaction at room temperature (Scheme 1A). The aerogel networks were used to develop a highly sensitive electrochemical sensing platform for the detection of glucose (Scheme 1B). [ABSTRACT FROM AUTHOR]