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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]

In this work, we reported an efficient platinum nanoparticles functionalized nitrogen doped graphene (PtNPs@NG) nanocomposite for devising novel electrochemical glucose biosensor for the first time. The fabricated PtNPs@NG and biosensor were characterized using transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, static water contact angle, UV–vis spectroscopy, electrochemical impedance spectra and cyclic voltammetry, respectively. PtNPs@NG showed large surface area and excellent biocompatibility, and enhanced the direct electron transfer between enzyme molecules and electrode surface. The glucose oxidase (GOx) immobilized on PtNPs@NG nanocomposite retained its bioactivity, and exhibited a surface controlled, quasi-reversible and fast electron transfer process. The constructed glucose biosensor showed wide linear range from 0.005 to 1.1 mM with high sensitivity of 20.31 mA M −1 cm −2 . The detection limit was calculated to be 0.002 mM at signal-to-noise of 3, which showed 20-fold decrease in comparison with single NG-based electrochemical biosensor for glucose. The proposed glucose biosensor also demonstrated excellent selectivity, good reproducibility, acceptable stability, and could be successfully applied in the detection of glucose in serum samples at the applied potential of −0.33 V. This research provided a promising biosensing platform for the development of excellent electrochemical biosensors. [ABSTRACT FROM AUTHOR]

A tetragonal columnar-shaped TiO2 (TCS-TiO2) nanorods are synthesized via a facile route for the immobilization of glucose oxidase (GOx). A novel electrochemical glucose biosensor is constructed based on the direct electrochemistry of GOx at TCS-TiO2 modified glassy carbon electrode. The fabricated biosensor is characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, electrochemical impedance spectra and cyclic voltammetry. The immobilized enzyme molecules on TCS-TiO2 nanorods retain its native structure and bioactivity and show a surface controlled, quasi-reversible and fast electron transfer process. The TCS-TiO2 nanorods have large surface area and provide a favorable microenvironment for enhancing the electron transfer between enzyme and electrode surface. The constructed glucose biosensor shows wide linear range from 5.0×10−6 to 1.32×10−3 M with a high sensitivity of 23.2mAM−1 cm−2. The detection limit is calculated to be 2.0×10−6 M at signal-to-noise of 3. The proposed glucose biosensor also exhibits excellent selectivity, good reproducibility, and acceptable operational stability. Furthermore, the biosensor can be successfully applied in the detection of glucose in serum sample at the applied potential of −0.50V. The TCS-TiO2 nanorods provide an efficient and promising platform for the immobilization of proteins and development of excellent biosensors. [ABSTRACT FROM AUTHOR]

Abstract: Multi-walled carbon nanotubes (MWCNTs)–nanoflake-like SnS2 nanocomposite were designed for immobilization of glucose oxidase (GOx). The direct electrochemistry of GOx and glucose sensing at MWCNTs–SnS2 modified glassy carbon electrode were studied. Compared with single MWCNTs or SnS2, the MWCNTs–SnS2 film has larger surface area and provides a more favorable microenvironment for facilitating the electron transfer between enzyme and electrode surface. The properties of GOx/MWCNTs–SnS2 were examined by scanning electron microscopy, UV–vis spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry. The immobilized enzyme on MWCNTs–SnS2 composite film retained its native structure and bioactivity and showed a surface controlled, reversible two-proton and two-electron transfer reaction with a apparent electron transfer rate constant of 3.96s−1. The constructed glucose biosensor exhibits wider linear range from 2.0×10−5 M to 1.95×10−3 M, much lower detection limit of 4.0×10−6 M at signal-to-noise of 3 and higher sensitivity of 21.65mAM−1 cm−2 than our previous nanoflake-like SnS2-based glucose sensor. The proposed biosensor has excellent selectivity, good reproducibility, and acceptable operational stability and can be successfully applied in the reagentless glucose sensing at −0.43V. This MWCNTs–SnS2 composite provides a new avenue for immobilizing proteins and fabricating excellent biosensors. [Copyright &y& Elsevier]

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]

Abstract: A novel immunoaffinity column used as an immunosensor for flow-injection chemiluminescent (CL) immunoassay was prepared by immobilizing antibody on carboxylic resin beads. The immunosensor could fast recognize and trap the immunocomplex of horseradish peroxidase (HRP)-labeled antibody and antigen, which was firstly formed with a micro-bubble accelerated pre-incubation process, to produce a sandwich immunocomplex. The HRP introduced in the immunoaffinity column could catalyze the CL reaction to produce enzyme-enhanced emission. With α-fetoprotein (AFP) as a mode, a flow-injection CL immunoassay was proposed. The whole assay for one sample, including the pre-incubation and the regeneration of immunoaffinity column, could be performed within 16min. The linear range was 1.0–80ng/ml with a correlation coefficient of 0.998 and a detection limit of 0.1ng/ml at a signal/noise ratio of 3. The intra- and inter-assay coefficients of variation at 20ng/ml AFP were 1.2% and 8.5%, respectively. The storage stability of the immunoaffinity column and the accuracy for sample detection were acceptable. This flexible, sensitive, low-cost, and rapid method is valuable for clinical immunoassay. [Copyright &y& Elsevier]

In this research, dual-strategy biosensing of glucose was proposed based on multifunctional CuWO4 nanoparticles (CuWO4 NPs), which were prepared for the application of electrochemical and colorimetric sensing of glucose. CuWO4 NPs show large specific surface area and good conductivity as well as excellent peroxidase-like activity. A sensitive and selective electrochemical glucose biosensor was fabricated with the immobilization of glucose oxidase (GOx) on a CuWO4 NP modified electrode for enhancing the direct electron transfer behavior. A wide linear range of 0.005–1.8 mM with a low detection limit of 1.5 μM and a high sensitivity of 28.02 mA M−1 cm−2 were achieved by using the electrochemical biosensor. Meanwhile, a colorimetric and visual glucose biosensor was constructed based on the GOx/CuWO4 cascade nanozyme, which shows a linear range of 0.05–1.0 mM with excellent selectivity. CuWO4 NPs as a promising matrix open up a dual-strategy biosensor for sensitive and selective detection of glucose. [ABSTRACT FROM AUTHOR]

Efficient urchin-like Pt nanoparticles@Bi2S3 (PtNPs@Bi2S3) composite materials were prepared by a composite soft template synthesis of urchin-like Bi2S3 and then the microwave-assisted growth of PtNPs onto the Bi2S3 nanostructure. For the first time, an accurate electrochemical glucose biosensor was fabricated via immobilizing glucose oxidase (GOx) on PtNPs@Bi2S3. The PtNPs@Bi2S3 composite was investigated via scanning electron microscopy, electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy, and cyclic voltammetry. The PtNPs@Bi2S3 composite provides a large surface area to load a large number of enzyme molecules, which maintains the biological activity. PtNPs loaded on Bi2S3 enhanced the conductivity and improved the direct electron transfer of the proposed biosensor with the synergistic effect. The fabricated electrochemical biosensor possesses high sensitivity, and a wide linear range from 0.003 mM to 0.1 mM and 0.1 mM to 1.9 mM. Moreover, the biosensor has outstanding stability, superior selectivity and good repeatability, which can be utilized to monitor the glucose level in practical human serum. The PtNPs@Bi2S3 composite supplies a special matrix for immobilizing proteins and potential for establishing other effective biosensors. [ABSTRACT FROM AUTHOR]

Abstract: A mesoporous silica nanoshpere (MSN) was proposed to modify glassy carbon electrode (GCE) for the immobilization of protein. Using glucose oxidase (GOD) as a model, direct electrochemistry of protein and biosensing at the MSN modified GCE was studied for the first time. The MNS had large surface area and offered a favorable microenvironment for facilitating the direct electron transfer between enzyme and electrode surface. Scanning electron microscopy, transmission electron microscopy, UV–vis spectroscopy and cyclic voltammetry were used to examine the interaction between GOD and the MSN matrix. The results demonstrated that the immobilized enzyme on the MSN retained its native structure and bioactivity. In addition, the electrochemical reaction showed a surface controlled, reversible two-proton and two-electron transfer process with the apparent electron transfer rate constant of 3.96s−1. The MNS-based glucose biosensor exhibited the two linear ranges of 0.04–2.0mM and 2.0–4.8mM, a high sensitivity of 14.5mAM−1 cm−2 and a low detection limit of 0.02mM at signal-to-noise of 3. The proposed biosensor showed excellent selectivity, good reproducibility, acceptable stability and could be successfully applied in the reagentless detection of glucose in real samples at −0.45V. The work displayed that mesoporous silica nanosphere provided a promising approach for immobilizing proteins and fabrication of excellent biosensors. [Copyright &y& Elsevier]

A novel hedgehog-shaped bismuth sulfide (HS-Bi2S3) nanostructure was for the first time explored as an electrode material for biosensing. Using cetyltrimethyl ammonium bromide (CTAB)-trimellitic acid as a composite soft template, the HS-Bi2S3 nanostructure was synthesized by a hydrothermal route. Using glucose oxidase (GOx) as the model, the HS-Bi2S3 nanostructure was employed to immobilize GOx for the development of a sensitive electrochemical glucose biosensor. The characterization of HS-Bi2S3 and the biosensor was performed by scanning electron microscopy, X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry. The hedgehog-shaped nanostructure of Bi2S3 has a large specific surface area to trap a large number of enzyme molecules, and at the same time greatly enhances the direct-electron-transfer action of enzymes. The HS-Bi2S3-based biosensor shows a wide linear range of 0.005–1.7 mmol L−1 and a low detection limit of 1.6 μmol L−1 for glucose at −0.37 V, which presents much better assay performance in comparison with the glucose biosensor without HS-Bi2S3. The present electrochemical biosensor displays high selectivity, good repeatability and stability, which can be used to measure blood glucose in real serum samples. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of novel nanosized reduced graphene oxide@polystyrene nanospheres (rGO@PS NSs) through an electrostatic interaction method, and further their exploitation for highly sensitive label-free electrochemical immunoassay applications. These rGO@PS NSs provide a universal and promising carrier platform to develop excellent biosensors for clinical screening and diagnostic applications. [ABSTRACT FROM AUTHOR]

In this work, SrTiO 3 nanoparticles (SrTiO 3 NPs), a novel and effective perovskite-type material, are synthesized to modify electrode for the development of sensitive enzymatic electrochemical biosensor applications. The electrochemical behavior of glucose oxidase (GOx) immobilized on SrTiO 3 NPs-modified glassy carbon electrode is investigated. Scanning electron microscopy and cyclic voltammetry are used to characterize the morphology and assay property of different modified electrodes. Results illustrate that SrTiO 3 NPs possess large surface area and apparently enhance the direct electron transfer between GOx and modified electrode. The SrTiO 3 NPs-based enzyme biosensor shows a high sensitivity of 15.6 mA·M − 1 ·cm − 2 , wide linear range from 0.01 mM to 1.2 mM, and a low detection limit of 3 μM (S/N = 3). Furthermore, the resultant glucose biosensor has excellent selectivity, acceptable repeatability, practicality and stability. The perovskite SrTiO 3 NPs provide a very attractive and potential electrode material to develop electrochemical biosensors. [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]

In this work, novel perovskite-type calcium titanate nanoparticles (CaTiO 3 NPs) were for the first time exploited for the immobilization of proteins and the development of electrochemical biosensor. The CaTiO 3 NPs were synthesized with a simple and cost-effective route at low temperature, and characterized by scanning electron microscopy, X-ray photoelectron spectroscopic spectrum, electrochemical impedance spectrum, UV–visible spectroscopy, Fourier transform infrared spectrum, and cyclic voltammetry, respectively. The results indicated that CaTiO 3 NPs exhibited large surface area, and greatly promoted the direct electron transfer between enzyme molecules and electrode surface. The immobilized enzymes on this matrix retained its native bioactivity and exhibited a surface controlled, quasi-reversible two-proton and two-electron transfer reaction with an electron transfer rate of 3.35 s −1 . Using glucose oxidase as model, the prepared glucose biosensor showed a high sensitivity of 14.10±0.5 mA M −1 cm −2 , a wide linear range of 7.0×10 −6 to 1.49×10 −3 M, and a low detection limit of 2.3×10 −6 M at signal-to-noise of 3. Moreover, the biosensor also possessed good reproducibility, excellent selectivity and acceptable storage life. This research provided a new-type and promising perovskite nanomaterials for the development of efficient biosensors. [ABSTRACT FROM AUTHOR]

This article describes an electrochemical glucose biosensor that is based on the immobilization of the enzyme glucose oxidase (GOx) on a glassy carbon electrode that was modified with silver-ZnO hybrid nanorods (HNRs). The HNRs containing different fractions of silver were synthesized by a one-step solvothermal method. Transmission electron microscopy, energy dispersive spectroscopy and X-ray diffraction confirmed the formation of these HNRs. FTIR spectroscopy and cyclic voltammetry demonstrated that the enzyme on the HNRs retained its native structure and bioactivity. The HNRs containing 11.26 wt% silver produced the best electrochemical response and direct electron transfer between enzyme and electrode surface. The sensor responds to glucose with two linear ranges (from 0.01 to 0.1 mM and from 0.1 to 1.5 mM). The sensitivity is 18.7 mA∙ M ∙ cm, and the detection limit is 5 μM (at an SNR of 3). The biosensor is selective, acceptably stable, and well reproducible. It was successfully applied to the quantitation of glucose in human serum, and results were within −8.1 % and +6.5 % of data obtained with a reference method. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We have developed an impedimetric immunosensor for the determination of bovine interleukin-4, a cytokine involved in the immune response to certain parasites and the development of some bovine diseases. Monoclonal antibody against bovine interleukin-4 was immobilized on a glassy carbon electrode modified with reduced graphene oxide and chitosan. Transmission electron microscopy, static contact angle measurement, and electrochemical impedimetry are used to characterize the immunosensor. The nanocomposite possesses a high surface area that is well suited for the immobilization of antibody. The relative increase in impedance on exposure of the sensor to solutions containing bovine interleukin-4 is linearly proportional to its logarithmic concentration in the 0.1 to 50 ng mL and the detection limit is 80 pg mL. The immunosensor is selective, well reproducible, and acceptably stable. It presents a useful tool for further studies on the role of this cytokine in the immunology and pathogenesis of bovine diseases. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A novel glucose electrochemical biosensor was constructed based on the immobilization of glucose oxidase (GOx) in cage-like PbS nanostructure. The fabricated biosensor was characterized by scanning electron microscopy, UV–vis spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry, respectively. The direct electrochemistry of GOx at cage-like PbS nanostructure modified glassy carbon electrode was for the first time studied. The cage-like PbS nanostructure has larger surface area and provides a favorable microenvironment for facilitating the direct electron transfer between enzyme and electrode surface. The immobilized enzymes on PbS cage-like nanostructure retains its native structure and bioactivity and shows a surface controlled, reversible two-proton and two-electron transfer reaction with a apparent electron transfer rate constant of 2.85s−1. The biosensor shows wide linear range for glucose from 5.0×10−5 M to 1.45×10−3 M with high sensitivity of 11.02mAM−1 cm−2. The detection limit was calculated to be 1.0×10−5 M at signal-to-noise of 3. Moreover, the proposed glucose biosensor displays excellent selectivity, good reproducibility, and acceptable operational stability and can be successfully applied in the detection of glucose in serum sample. The cage-like PbS nanostructure provides a promising approach for immobilizing proteins and fabricating excellent biosensors. [ABSTRACT FROM AUTHOR]

Abstract: This work reports a new method for the preparation and application of a kind of biocompatible calcium phosphate–gold nanoparticles (Ca3(PO4)2–AuNPs) nanocomposite. UV–vis spectroscopy and transmittance electron microscopy (TEM) have been used to monitor the formation process of the nanocomposite and to examine the interaction between calcium phosphate and gold nanoparticles (AuNPs). The nanocomposite has multiple sites and improved conductivity which make it suitable for the binding of proteins to construct electrochemical sensors. Myoglobin (Mb) adsorbed on the nanocomposite retained its native structure which was proved by Fourier transform infrared spectroscopy (FTIR). Direct electron transfer between the adsorbed Mb and the electrode was observed. Further results demonstrated that the adsorbed Mb has good electrocatalytic activity towards the reduction of H2O2 in the absence of any mediator. [Copyright &y& Elsevier]