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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]

Possessing prominent customization in structural design as well as unique physicochemical properties, covalent organic frameworks (COFs) show great potential in the biosensing field. In this study, we prepared a novel COF-based electrochemical enzymatic composite (denoted as Fe3O4@COF@HRP), where spherical magnetic COF was functionalized with horseradish peroxidase (HRP). The resultant composite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Thereinto, the Fe3O4 nanoparticles with remarkable conductivity could accelerate the charge transfer, while HRP with good catalytic activity could enhance the sensitivity of the as-prepared biosensor. With such a design, the Fe3O4@COF@HRP-based biosensor exhibits excellent analytical properties for the determination of hydroquinone. The extended linear detection range was 0.5–300 μmol L−1, and the limit of detection was down to 0.12 μmol L−1 (S/N = 3). Furthermore, the electrochemical enzymatic biosensor was used to detect low-abundance hydroquinone in environmental water samples with a satisfactory consequence, suggesting great promise in sensing applications. [ABSTRACT FROM AUTHOR]

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]

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]

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 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]

An electrochemical non-enzymatic glucose sensor was fabricated by electrodeposition of copper nanoparticles (CuNPs) onto a poly( o-phenylenediamine) (PoPD) film-modified glassy carbon electrode (CuNPs/PoPD/GCE). We had studied some factors such as the pH value of supporting electrolyte, the amount of PoPD and applied potentials and optimize the experiment conditions. Under the optimum conditions, the as-obtained sensor for glucose sensing had achieved a wide linear range, low detection limit, and fast response time. The current response of the as-obtained sensor towards electrochemical oxidation of glucose was linear with the concentration of glucose in the range of 5.0 μM to 1.6 mM ( R = 0.998) in the solution of 0.1 M NaOH at the applied potential of 0.5 V. The detection limit is 0.25 μM and the fast response achieves within 1 s. The sensor exhibits good sensitivity, selectivity, and reproducibility. The proposed non-enzymatic glucose was successfully employed to determine glucose in blood samples. [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]

We report on label-free immunosensors for the highly sensitive detection of avian influenza virus. The method makes use of the microcantilevers of an atomic force microscope onto which monoclonal antibodies against avian influenza virus were covalently immobilized. The factors influencing the performance of the resulting immunosensors were optimized by measuring the deflections of the cantilever via optical reflection, and this resulted in low detection limits and a wide analytical range. The differential deflection signals revealed specific antigen binding and their intensity is proportional to the logarithm of the concentrations of the virus in solution. Under optimal conditions, the immunosensors exhibit a linear response in the 7.6 ng mL to 76 μg mL concentration range of avian influenza virus, and the detection limit is 1.9 ng mL. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A novel chemiluminescent immunosensor for carbohydrate antigen 19-9 (CA19-9) based on the immobilization of CA19-9 on the cross-linked chitosan membrane was developed. The different membranes were characterized by atomic force microscopy (AFM) and infrared spectrum, respectively. Based on a noncompetitive immunoassay format, this proposed chemiluminescent immunosensor enabled a low-cost, flexible and rapid determination for CA19-9 in combination with flow injection analysis (FIA). After an off-line incubation of the analyte CA19-9 with horseradish peroxidase (HRP)-labeled anti-CA19-9, the mixture was injected into the immunosensor, which led to the trapping of free HRP-labeled anti-CA19-9 by the immobilized antigen in the immunosensor. The trapped HRP-labeled antibody was detected by chemiluminescence due to its catalytic activity following the reaction of luminol and H2O2. Under optimal conditions, the decreased chemiluminescent signal of the immunosensor was proportional to the CA19-9 concentration in the range of 2.0–25 U/ml with a detection limit of 1.0 U/ml. The immunosensor showed an acceptable accuracy and good reproducibility. The results of 20 human serum samples detected by this method were in acceptable agreement with those obtained by immunoradiometric assay. The proposed immunosensor provided a new promising tool for practical clinical detection of the serum CA19-9 level. [Copyright &y& Elsevier]

Abstract A novel NH 4 + voltammetric electrochemical biosensor was constructed by immobilizing glutamate dehydrogenase (GLDH)/Fe 3 O 4 /graphene (GR)/chitosan (CS) nanobiocomposite onto a glassy carbon electrode (GCE). On the GLDH/Fe 3 O 4 /GR/CS/GCE, GLDH catalyzed the reversible reaction, i.e., the reductive amination of α-ketoglutaric acid and the oxidative deamination of L-glutamate. The electrons produced in the enzymatic reactions were transferred to the surface of the electrode via the [Fe(CN) 6 ]3−/4− couple, which helped for the amplification of the electrochemical signal. The electrochemical detection of NH 4 + was based on the fact that the enhanced response current was proportional to the NH 4 + concentration. Owing to the combination of the advantages of the synergistic effects of Fe 3 O 4 nanospheres, GR and CS, a promising platform for NH 4 + sensing was provided. Under optimum conditions, the introduced biosensor had a linear range of 0.4–2.0 μM for NH 4 + with the detection and quantification limits of 0.08 and 0.27 μM, respectively. Moreover, the biosensor exhibited good sensitivity and excellent reproducibility. It could retain 91.8% of its original response after two weeks of storage at 4 °C, suggesting satisfactory stability. Additionally, the proposed biosensor was successfully applied to detect NH 4 + levels in PM 2.5 samples, indicating its feasibility for application in NH 4 +monitoring in the environmental fields. Graphical abstract fx1 Highlights • Fe 3 O 4 /graphene/chitosan nanocomposite was synthesized and characterized. • The proposed composite provided a good loading platform for glutamate dehydrogenase. • NH 4 + in PM 2.5 was successfully assayed by the developed biosensor. • This biosensor provided a convenient and low-cost method for NH 4 + detection in PM 2.5. [ABSTRACT FROM AUTHOR]

Graphical abstract TAPB-DMTP-COFs/AuNPs composites were synthesized and investigated as a novel electrochemical probe for chlorogenic acid detection. Highlights • COFs/AuNPs composites were synthesized using a solution infiltration method. • Results exhibited high sensitivity and good stability to chlorogenic acid detection. • Satisfactory results were achieved in real samples. • This research expands the applications of COFs based composites in biosensor. Abstract In this work, novel gold nanoparticles-doped TAPB-DMTP-COFs (TAPB, 1,3,5-tris(4-aminophenyl)benzene; DMTP, 2,5-dimethoxyterephaldehyde; COFs, covalent organic frameworks) composite was successfully prepared via COFs as the host matrix to support the growth of gold nanoparticles. With the strong electrostatic interaction between gold nanoparticles and unsaturated amine group present on TAPB-DMTP-COFs, the gold nanoparticles were successfully immobilized onto the surface of TAPB-DMTP-COFs under vigorously stirring. Then, this novel composite was used to constitute an advanced electrochemical sensor and presented a good electrocatalytic activity toward the oxidation of chlorogenic acid (CGA) in the phosphate buffer solution (pH 7.0). After a series of experiments, this electrochemical sensor displays a wide linear range of 1.0 × 10−8 – 4.0 × 10−5 mol L−1, low detection limit of 9.5 × 10−9 mol L−1 as well as a good repeatability of 4.1% in 2.0 × 10−5 mol L−1 CGA after ten scanning rounds. Moreover, the sensor exhibits an excellent stability and maintains its catalytic activity at least 100 cycles. Our work not only provides a simple way to detect CGA quantitatively in real samples, but paves a new platform for COFs-based composite in biosensor. [ABSTRACT FROM AUTHOR]

This work developed a novel sulfate biosensor based on arylsulfatase (AS) inhibition. AS mixed with glutaraldehyde and bovine serum albumin was immobilized on glassy carbon electrode (GCE), which was first modified with poly- l -lysine (PLL)/graphene (GR) hybrid and electrodeposited gold nanoparticles (AuNPs). The characterizations were performed by TEM, SEM, FTIR, Raman spectroscopy and cyclic voltammetry. AS can catalyze 4-nitrocatechol sulfate (NCS) to hydrolyze to sulfate and 4-nitrocatcchol (NC), which is electroactive and an anodic current occurs at ∼0.42 V vs. SCE. However, the production of NC would decrease in the presence of sulfate due to its inhibition effect on the enzymatic hydrolysis reaction, thus leading to a decrease in the oxidation current. The inhibition measurements were carried out by detecting this current decrease after adding sulfate. At optimal conditions, the inhibition rate was linear to −log [sulfate] in the concentration range from 1.0 × 10 −7 to 1.0 × 10 −5 M with the detection limit of 4.0 × 10 −8 M. The introduced biosensor was further applied to assay the sulfate constituent in PM 2.5 , and the results were verified by employing ion chromatography as a reference. It showed that the new biosensor has a promising application for sulfate detection in real samples. [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]

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]

In this work, the fabrication and performances of a glucose biosensor based on the electrodeposited gold nanoparticle–polyvinylpyrrolidone–polyaniline (AuNP–PVP–PANI) nanocomposites have been demonstrated. The nanocomposites were electrodeposited on a glassy carbon electrode (GCE) in a homogeneous three-component solution consisting of aniline, PVP and AuNPs. Glucose oxidase (GOx) was subsequently immobilized on the as-prepared AuNP–PVP–PANI nanocomposites using Nafion as the preventing layer. The electrochemical and electrocatalytic properties of the Nafion/GOx/AuNP–PVP–PANI modified GCE were researched. It exhibited good electrocatalytic performances with a large linear range from 0.05 mM to 2.25 mM, a low detection limit of 1.0 × 10 − 5 M (S/N = 3), and a high sensitivity of 9.62 μA mM − 1 cm − 2 . This sensor with excellent stability and reproducibility was also allowed for the detection of glucose in human serum samples with satisfactory results. [ABSTRACT FROM AUTHOR]

The flexible electrochemical sensor is a key component of the health monitoring system which can continuously track the physiological signals of the human body, while there is no obvious discomfort and invasiveness. Therefore, it has great potential in personalized medical testing. However, the development of flexible electrochemical sensors currently faces many difficulties, such as the limitations of conductive material properties and manufacturing methods, and the disadvantages of commonly used flexible substrates that are not resistant to high temperatures. In this work, inorganic nanomaterials commonly used to make flexible electrochemical sensors were classified to zero-dimensional (0D) nanomaterials, one-dimensional (1D) nanomaterials, two-dimensional (2D) nanomaterials, and hybrid nanomaterials according to their morphology. The fabrication method of the nanomaterials-based flexible electrochemical sensors was also introduced. Furthermore, the application of flexible electrochemical sensors for chemical and biological sensing and their detection performance were summarized. The detection targets were classified to ion, small molecule, biomacromolecule, and bacteria, respectively. [Display omitted] • The flexible electrochemical sensor can replace the bulky and expensive analytical instruments used in the medical field. • Inorganic functional nanomaterials that commonly used to make flexible electrochemical sensors was introduced. • Inorganic functional nanomaterials were classified to 0D, 1D, 2D and hybrid nanomaterials. • The fabrication method of the nanomaterials-based flexible electrochemical sensors was also introduced. • The application of flexible electrochemical sensors for chemical and biological sensing was summarized. [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]

An enzymatic procedure based on a catalase biosensor for the detection of forchlorfenuron (CPPU) has been reported in this work. Catalase was immobilized on boron nitride (BN) sheets dispersed in chitosan by adsorption. The immobilized catalase exhibited direct electron transfer character and excellent electrocatalytic activity towards H 2 O 2 reduction. After introducing CPPU into the H 2 O 2 containing phosphate buffer solution, the catalase-catalyzed H 2 O 2 reduction current decreased. By measuring the current decrease, CPPU can be determined in the range of 0.5–10.0 µM with the detection limit of 0.07 μM. The non-competitive inhibition behavior of CPPU towards catalase was verified by the Lineweaver–Burk plots. Long stability character has been ascribed to this biosensor. Possible use of this biosensor in flow systems is illustrated. The proposed biosensor has been successfully applied to CPPU determination in fruits samples with satisfactory results. [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: An electrochemical sensor based on a copolymer poly(4-vinylpyridine)-co-poly(acrylonitrile), P4VP-co-PAN, and Fe2O3 nanoparticle film modified glassy carbon electrode was developed for the determination of glucose. We studied the response of glucose with the proposed electrode, and determined the optimum conditions by changing the potential, pH and P4VP-co-PAN. The current response measurements were performed in PBS (c=0.1M) with a potential of 0.7V. The current response of this glucose sensor showed a linear relationship with the concentration in the range of 2.5μM–0.58mM (r=0.997). The experimental results demonstrate that this method has such merits as simple operation, low cost, high sensitivity, long term stability and good reproducibility, with satisfactory results. [Copyright &y& Elsevier]

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: 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: Electrochemical impedance immunosensor, with its high sensitivity from electrochemical impedance analysis and ideal specificity from the immunoassay, is increasingly used in the detection of a kind of phenoxy acid herbicides which is 2,4-Dichlorophenoxybutyric acid (2,4-DB). In this experiment, synthetic 2,4-DB antibodies were immobilized on the electrode by the crosslinking of l-Cysteine/glutaraldehyde, and 2,4-DB were measured by the increase of electron-transfer resistance when the immune reaction occurred, with Fe(CN)6 3−/Fe(CN)6 4− as the probe. Under optimal conditions, the change of resistance is in a linear relationship with the logarithm of the concentration in the range of 1.0×10−7–1.0×10−3 g/L (R=0.994) with the detection limit of 1.0×10−7 g/L (0.1ppb). This method bears such merits as simplicity in operation, high sensitivity, wide linear range, specificity, reproducibility and good stability. The actual soybean samples were analyzed with the recovery of 82.8%–102.3%. [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]

A novel immunosensor for rapid separation-free determination of carcinoembryonic antigen (CEA) in human serum is proposed. The immunosensor is prepared by co-immobilizing thionine and horseradish peroxidase (HRP)-labeled CEA antibody on a glassy carbon electrode (GCE) through covalently binding them to GCE with a glutaraldehyde (GA) linkage. The electrochemical behavior of the immobilized thionine displays a surface-controlled electrode process with an average electron transfer rate constant of 4.74±2.99 s−1. It can be used as an electron transfer mediator for enzymatic activity detection of the HRP-labeled antibody to CEA. After the immunosensor is incubated with CEA solution at 23 °C for 40 min, the access of activity center of the HRP to thionine is partly inhibited, which leads to a linear decrease in the catalytic efficiency of the HRP to the oxidation of immobilized thionine by H2O2 at −300 mV over two CEA concentration ranges from 0.5 to 3.0 and 3.0 to 167 ng/ml. Under optimal conditions, the detection limit for the CEA immunoassay is 0.1 ng/ml at three times background noise. The immunosensor shows good accuracy and acceptable storage stability, precision and reproducibility with intra-assay CVs of 6.1% and 5.8% at 2.5 and 50 ng/ml CEA, respectively, and an inter-assay CV of 6.3% at 50 ng/ml. This method is economical and shortens the analytical time, making it potentially attractive for clinical immunoassays. [Copyright &y& Elsevier]