Highly sensitive glucose biosensor using new glucose oxidase based biocatalyst

Glucose, which is a primary energy source of living organisms, can induce diabetes or hypoglycemia if its concentration in blood is irregular. It is therefore important to develop glucose biosensor that reads the concentration of glucose in blood precisely. In the present work, we suggest new glucose oxidase (GOx) based catalysts that can improve the sensitivity of the glucose biosensor and make glucose measurements over a wide concentration ranges possible. For synthesizing such catalysts, a composite including pyrenecarboxaldehyde (PCA) and GOx is attached to substrate including carbon nanotube (CNT) and polyethyleneimine (PEI) (CNT/PEI/[PCA/GOx]). Catalytic activity and stability of the catalyst are then evaluated. According to the investigation, the catalyst shows excellent glucose sensitivity of 47.83 μAcm^?2mM^?1, low Michaelis-Menten constant of 2.2 mM, and wide glucose concentration detection, while it has good glucose selectivity against inhibitors, such as uric acid and ascorbic acid. Also, its activity is maintained to 95.7% of its initial value even after four weeks, confirming the catalyst is stable enough. The excellence of the catalyst is attributed to hydrophobic interaction, C=N bonds, and π-hydrogen interaction among GOx, PCA and PEI/CNT. The bindings play a role in facilitating electron transport between GOx and electrode.     

Highly sensitive and selective electrochemical determination of dopamine and ascorbic acid at Ag/Ag2S modified electrode

A biosensor electrode possessing highly sensitive and selective determination of dopamine (DA) is fabricated. This electrode, a silver (Ag) thin film on indium-tin-oxide glass, is treated with a silver sulfide (Ag₂S) film using electrochemical deposition. Active Ag ion is easier to form on Ag₂S than on pristine Ag, which prefers to attract ascorbic acid (AA). The Ag₂S layer reduces the oxidation potential of AA due to the electrostatic interaction, which results in well-separation of mixed oxidation responses to both of DA and AA. Besides, the Ag₂S-modified electrode exhibits dramatic electrocatalytic effect on the oxidation of DA in the presence of AA. In 0.1 M phosphate buffer solution at pH ∼ 7.0, the differential pulse voltammetric peak intensity linearly correlates with DA concentration in two regions, viz. 1.0–10, and 10–100 μM, with correlation coefficient of 0.998 and 0.995, respectively. The lowest concentration limit of 1.0 μM DA can be detected. The interference of AA effectively diminishes in the mixed solution. These features make the Ag₂S significant for selective and sensitive measurement of DA in the presence of excess AA.     

A highly sensitive electrochemical biosensor based on zinc oxide nanotetrapods for L-lactic acid detection

An amperometric biosensor based on zinc oxide (ZnO) nanotetrapods was designed to detect L-lactic acid. The lactate oxidase was immobilized on the surface of ZnO nanotetrapods by electrostatic adsorption. Unlike traditional detectors, the special four-leg individual ZnO nanostructure, as an adsorption layer, provides multiterminal charge transfer channels. Furthermore, a large amount of ZnO tetrapods are randomly stacked to form a three-dimensional network naturally that facilitates the exchange of electrons and ions in the phosphate buffer solution. Utilizing amperometric response measurements, the prepared ZnO nanotetrapod L-lactic acid biosensor displayed a detection limit of 1.2 μM, a low apparent Michaelis-Menten constant of 0.58 mM, a high sensitivity of 28.0 μA cm(-2) mM(-1) and a good linear relationship in the range of 3.6 μM-0.6 mM for the L-lactic acid detection. This study shows that the biosensor based on ZnO tetrapod nanostructures is highly sensitive and able to respond rapidly in detecting lactic acid.     

Amperometric tyrosinase biosensor based on Fe3O4 nanoparticles-coated carbon nanotubes nanocomposite for rapid detection of coliforms

A tyrosinase (Tyr) biosensor was developed based on Fe₃O₄ magnetic nanoparticles (MNPs)-coated carbon nanotubes (CNTs) nanocomposite and further applied to detect the concentration of coliforms with flow injection assay (FIA) system. Negatively charged MNPs were absorbed onto the surface of CNTs which were wrapped with cationic polyelectrolyte poly(dimethyldiallylammonium chloride) (PDDA). The Fe₃O₄ MNPs-coated CNTs nanocomposite was modified on the surface of the glassy carbon electrode (GCE), and Tyr was loaded on the modified electrode by glutaraldehyde. The immobilization matrix provided a good microenvironment for retaining the bioactivity of Tyr, and CNTs incorporated into the nanocomposite led to the improved electrochemical detection of phenol. The Tyr biosensor showed broad linear response of 1.0 × 10⁻⁸-3.9 × 10⁻⁵ M, low detection limit of 5.0 × 10⁻⁹ M and high sensitivity of 516 mA/M for the determination of phenol. Moreover, the biosensor integrated with a FIA system was used to monitor coliforms, represented by Escherichia coli (E. coli). The detection principle was based on determination of phenol which was produced by enzymatic reaction in the E. coli solution. Under the optimal conditions, the current responses obtained in the FIA system were proportional to the concentration of bacteria ranging from 20 to 1 × 10⁵ cfu/mL with detection limit of 10 cfu/mL and the overall assay time of about 4 h. The developed biosensor with the FIA system was well suited for quick and automatic clinical diagnostics and water quality analysis.     

A new amperometric glucose biosensor based on platinum nanoparticles/polymerized ionic liquid-carbon nanotubes nanocomposites

A new amperometric glucose biosensor has been developed based on platinum (Pt) nanoparticles/polymerized ionic liquid-carbon nanotubes (CNTs) nanocomposites (PtNPs/PIL-CNTs). The CNTs was functionalized with polymerized ionic liquid (PIL) through directly polymerization of the ionic liquid, 1-vinyl-3-ethylimidazolium tetrafluoroborate ([VEIM]BF₄), on carbon nanotubes and then used as the support for the highly dispersed Pt nanoparticles. The electrochemical performance of the PtNPs/PIL-CNTs modified glassy carbon (PtNPs/PIL-CNTs/GC) electrode has been investigated by typical electrochemical methods. The PtNPs/PIL-CNTs/GC electrode shows high electrocatalytic activity towards the oxidation of hydrogen peroxide. Taking glucose oxidase (GOD) as the model, the resulting amperometric glucose biosensor shows good analytical characteristics, such as a high sensitivity (28.28 μA mM⁻¹ cm⁻²), wide linear range (up to 12 mM) and low detection limit (10 μM).     

Highly sensitive nano-aerosol detection based on the whispering-gallery-mode in cylindrical optical fiber resonators

Highly sensitive detection of nanoscale aerosols, or nano-aerosols, is a difficult challenge. Here, we report a fiber optical technique that is capable of detecting trace-level nano-aerosols. Our method is based on monitoring the nano-aerosol-induced resonance shift due to the optical Whispering-Gallery-Mode (WGM) in a cylindrical optical fiber resonator. A nearly linear relationship between the WGM resonance shift and the aerosol coverage ratio of silica nanoparticles (40–50 nm dia.) on the fiber resonator was identified in the low coverage regime. Our experimental results imply sensitivity at the level of ～2 nanoparticles per μm² deposited on the fiber resonator, which corresponds to pg-level sensitivity in the total aerosol mass within the effective detection area. The response of this fiber optical sensor is further confirmed by using silica nanoparticles deposited on the fiber surface via electrostatic self-assembly. The fiber optical technique for nanoparticle detection may ultimately lead to an instrument capable of real-time in situ aerosol detection with ultrahigh sensitivity.

Copyright © 2016 American Association for Aerosol Research     

基于花状ZnO-CHIT复合材料的安培型过氧化氢生物传感器

将水热法制备的纳米花状结构ZaO分散在壳聚糖中构成ZnO-壳聚糖复合膜来固定辣根过氧化物酶(HRP)构建安培型过氧化氢生物传感器.结果表明,在相同过氧化氢浓度下,加入纳米颗粒的电极的电流响应值比未加颗粒的高约40倍.ZnO-壳聚糖修饰电极对过氧化氢具有明显的增敏效应,线性范围为1.0×10～5.0×10-3mol/L,关系数为0.9977;检测下限为1.0×10-7mg/L(信噪比S/N=3).     

Highly sensitive electrochemical sensor based on zirconium oxide-decorated gold nanoflakes nanocomposite 2,4-dichlorophenol detection

Journal of Applied Electrochemistry - In this study, a sensitive and selective electrochemical sensor based on a zirconia oxide-decorated gold nanoflake nanocomposite-modified glassy carbon...     

Alcohol dehydrogenase amperometric biosensor based on a colloidal gold-carbon nanotubes composite electrode

A novel ethanol biosensor based on the bulk incorporation of alcohol dehydrogenase (ADH) into a colloidal gold (Au_coll)-multiwalled carbon nanotubes (MWCNTs) composite electrode using Teflon as binding material is reported. The composite Au_coll-MWCNTs-Teflon electrode exhibited significantly improved electrooxidation of NADH when compared with other carbon composite electrodes, including those based on carbon nanotubes. Amperometric measurements for NADH at +0.3 V showed significant differences in sensitivity between Au_coll-MWCNTs-Teflon and MWCNTs-Teflon composite electrodes. Incorporation of ADH into the bulk electrode material allowed the construction of a mediatorless ethanol biosensor. Both the enzyme loading and the NAD⁺ concentration in solution were optimized. The ADH-Au_coll-MWCNTs-Teflon biosensor allowed a limit of detection for ethanol of 4.7 μmol l⁻¹, which is remarkably better than those reported for other CNTs-based ADH biosensors. The apparent Michaelis-Menten constant was 4.95 mmol l⁻¹, which is much lower than that reported by immobilization of ADH onto a gold electrode. Both repeatability of the ethanol amperometric measurements, reproducibility with different biosensors, lifetime and storage ability can be, in general, advantageously compared with other ADH-CNTs biosensors. The biosensor was applied for the rapid determination of ethanol in commercial and certified beer samples.     

Development of an amperometric biosensor based on a redox‐mediator‐doped polypyrrole film

An amperometric biosensor was developed for the quantitative estimation of phenolic compounds in aqueous media. The enzyme tyrosinase [poly(phenol oxidase) (PPO)] was adsorbed onto a hexacyanoferrate(II)‐ion‐doped conducting polypyrrole (PPY) film deposited on an indium tin oxide (ITO) coated glass‐plate support. The PPO activity in the PPO/Fe²⁺‐PPY/ITO film was assayed as a function of the concentration of phenolic compounds. Cyclic voltammetric studies were carried out on this enzyme electrode, and the surface morphology of the enzyme‐immobilized polymer film was studied with scanning electron microscopy. The results of the amperometric response of the PPO/Fe²⁺‐PPY/ITO film showed sensitivities of 0.14, 0.21, and 0.36 A M^?1cm^?2 and linear response ranges of 9.9–84.7, 6.7–72.6, and 3.9–48.8 μM for phenol, catechol, and p‐chlorophenol, respectively. The PPO/Fe²⁺‐PPY/ITO electrode exhibited a response time of about 50 s and was stable for about 12 weeks at 4°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 927–933, 2004     

A sensitive amperometric bromate sensor based on multi-walled carbon nanotubes/phosphomolybdic acid composite film

An amperometric sensor for bromate was developed based on multi-walled carbon nanotubes (MWNTs)/phosphomolybdic acid (PMo₁₂) composite film coated on a pyrolytic graphite (PG) electrode. MWNTs are dispersed in PMo₁₂ aqueous solution through spontaneous and strong chemisorption between carbon and polyoxometalate, which results in a homogeneous MWNTs/PMo₁₂ composite. Due to the unique electronic and electrocatalytic properties of MWNTs and PMo₁₂, the combination of MWNTs and PMo₁₂ results in a remarkable synergistic augmentation on the response current. The bromate sensor based on the PG/MWNTs/PMo₁₂ electrode has excellent characteristics, such as a detection limit of 0.5 μM, a sensitivity of 760.9 μA mM⁻¹ cm⁻², a response time less than 2 s and a linear range from 5 μM to 15 mM.     

基于f-OMC-CoMoS_2/IL/GCE的亚硝酸盐电化学传感器

采用f-OMC-CoMoS_2/IL/GCE构建了一种新型的亚硝酸盐电化学传感器,采用循环伏安法和电流-时间法对传感器的检测性能进行探究。该传感器对亚硝酸盐展现出了很高的电催化氧化活性,重现性好、抗干扰能力强。在1~6700μmol/L呈良好的线性关系,检测限低至0.04μmol/L。     

Enzymatic biosensor for nitrite detection based on direct electron transfer by CPO-ILEMB/Au@MoS2/GC

Journal of Applied Electrochemistry - A novel nitrite electrochemical biosensor is constructed by glassy carbon electrodes (GC) coated by chloroperoxidase (CPO) -Au nanoparticles-MoS2 nanoflowers...     

A novel DNA biosensor based on ssDNA/Cyt c/l-Cys/GNPs/Chits/GCE

A novel DNA biosensor was fabricated by modified multilayer of ssDNA, cytochrome c, l-cysteine, metal gold nanoparticles and Chitosan (denoted as ssDNA/Cyt c/l-Cys/GNPs/Chits/GCE). The behavior of the DNA biosensor was then investigated by voltammetry, impedance spectrum and atomic force microscope (AFM), and the morphologic differences among each layer of the DNA biosensor were also observed. Results revealed that two well-defined redox peaks exhibited at 0.120 V and 0.362 V, and the amount of adsorbed DNA was 1.672 × 10⁻¹⁰ mol cm⁻². We concluded that the modified electrode could be used to detect DNA with the indicator daunomycin.     

A H2O2 biosensor based on immobilization of horseradish peroxidase in electropolymerized methylene green film on GCE

A novel H2O2 sensor is achieved by immobilizing horseradish peroxidase (HRP) in an electropolymerized methylene green (PMG) redox film. The electropolymerization of MG is carried out in a neutral phosphate buffer solution with 5×10–5m methylene green (MG) by using a two-step method. The polymer film only occurs on glassy carbon (electrodes and the reason for this is identified. The critical factor for the electropolymerization of MG lies in the preanodization on a glassy carbon) electrode, because a large amount of positive charges are accumulated and used to create the cation radicals form the polymer film. The formal potentials of PMG is pH dependent with a slope of 57mV per pH unit between pH6.0 and 8.0, which is close to the anticipated Nernstian value of 59mV for a two-electron, two-proton process. The PMG itself and the PMG on the H2O2 sensor show electrochemical behaviour with a linear plot of peak current against scan rate in the range 20 to 100mVs–1.     

Selective detection of dopamine on poly(indole-5-carboxylic acid)/tyrosinase electrode

We report here on a simple tyrosinase (TYR) modified electrode designed through the covalent bonding of the enzyme with poly (indole-5-carboxylic acid) (PIn5COOH) conducting polymer. This electrode was applied to the amperometric detection of dopamine (DA) in the presence of ascorbic acid (AA), uric acid (UA) and their mixtures, in the concentration range and ratios similar to those found in blood serum. Our experiments demonstrate that the presence of these interferents (AA, UA) does not affect the selectivity of such electrode towards dopamine with linear concentration dependence in the range of 0.5–20 μM, depending on the experimental conditions, however its sensitivity depends on the type and amount of interferent present. The lower limit of detection of DA in the presence of high AA (1000 fold) or UA (500 fold) concentration was found to be 0.1–0.5 μM. The sensitivity for DA detection is 6.2 A/M cm² with UA and 2.3 A/M cm² with AA present as interfering agents. For both interferents present in the ratio 12.5:1 (AA:UA), the sensitivity drops to the value of ca. 1.3 A/M cm². The Michaelis–Menten (K_M) constant and I_max values were evaluated, showing improved electrode sensitivity towards dopamine as judged from the decrease of the Michaelis–Menten constant.     

Ferrocenium hexafluorophosphate-induced nanofibrillarity of polyaniline-polyvinyl sulfonate electropolymer and application in an amperometric enzyme biosensor

The formation of nanofibrillar polyaniline-polyvinyl sulfonate (Pani-PVS) composite by electropolymerization of aniline in the presence of ferrocenium hexafluorophophate (FcPF₆) and its application in mediated-enzyme biosensor using the horseradish peroxidase/hydrogen peroxide (HRP/H₂O₂) enzyme-substrate system is reported. The electropolymerization was carried out at glassy carbon electrodes (GCE) and screen printed carbon electrodes (SPCE) in a strongly acidic medium (HCl). Scanning electron microscopy (SEM) images showed that 100 nm diameter nanofibrils were formed on the SPCE in contrast to the 800-1000 nm cauliflower-shaped clusters which were formed in the absence of FcPF₆. A model biosensor (GCE//Pani-PVS/BSA/HRP/Glu), consisting of horseradish peroxidase (HRP) immobilized by drop coating atop the GCE//Pani-PVS in the presence of bovine serum albumin (BSA) and glutaraldehyde (glu) in the enzyme layer casting solution, exhibited voltammetric responses characteristic of a mediated-enzyme system. The biosensor response to H₂O₂ was very fast (5 s) and it exhibited a detection limit of 30 μM (3σ) and a linearity of up to 2 mM (R² = 0.998). The relatively high apparent Michaelis-Menten constant value () of the sensor indicated that the immobilized enzyme was in a biocompatible microenvironment. The freshly prepared biosensor was successfully applied in the determination of the H₂O₂ content of a commercial tooth whitening gel with a very good recovery rate (97%).     

Mn2O3 nanoparticle-porous silicon nanocomposite based amperometric sensor for sensitive detection and quantification of Acetaminophen in real samples

Acetaminophen (AcP) commonly known as paracetamol is the most extensively used non-prescribed medication for the treatment of fever and different kinds of pain. Due to the wide range of use, the determination of AcP contents in commercial tablets, residual AcP present in human blood serum, and the presence of AcP in the environment from the unavoidable leakage during the industrial production becomes crucial. Therefore, we proposed an AcP sensor utilizing a novel Mn₂O₃-embedded mesoporous silicon (Mn₂O₃@PSi) nanocomposite fabricated glassy carbon electrode (GCE). Modern characterization techniques including FESEM, TEM, EDXS, XRD, XPS, and FTIR spectroscopy were employed to characterize the fabricated Mn₂O₃@PSi nanocomposite. XRD and XPS analysis confirmed the fruitful development of nanocomposite consisting of PSi, and Mn₂O₃. TEM images revealed that Mn₂O₃ nanoparticles were randomly distributed onto the PSi matrix. In the electrochemical investigations via the most reliable amperometric technique, the Mn₂O₃@PSi/GCE sensor showed excellent sensitivity (0.7948 μAμM^?1cm^?2), a wide LDR (0.3–138.7 μM), and a very low detection limit (LOD ～0.033 μM). The newly developed AcP sensor was further used to check the potential chemical interference using several closely related chemicals, presenting an extreme selectivity towards the AcP detection. The Mn₂O₃@PSi/GCE sensor electrode was also employed to determine the AcP in commercial paracetamol tablets and showed ～100% quantitative recovery. During the AcP determination, the Mn₂O₃@PSi/GCE sensor also displayed excellent reproducibility, repeatability, and stability. It is anticipated that this Mn₂O₃@PSi/GCE assembly will emerge as an efficient route in developing an effective AcP sensor.     

Highly sensitive acetone sensor based on Eu-doped SnO2 electrospun nanofibers

In this study, a series of undoped and Eu-doped SnO₂ nanofibers were synthesized via a simple electrospinning technique and subsequent calcination treatment. Field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were carefully used to characterize the morphologies, structures and chemical compositions of these samples. The results reveal that the as-prepared nanofibers are composed of crystallite grains with an average size of about 10 nm and Eu³⁺ ions are successfully doped into the SnO₂ lattice. Compared with pure SnO₂ nanofibers, Eu-doped SnO₂ nanofibers demonstrate significantly enhanced sensing characteristics (e.g., large response value, short response/recovery time and outstanding selectivity) toward acetone vapor, especially, the optimal sensor based on 2 mol% Eu-doped SnO₂ nanofibers shows the highest response (32.2 for 100 ppm), which is two times higher than that of the pure SnO₂ sensor at an operating temperature of 280 °C. In addition, the sensor exhibits a good sensitivity to acetone in sub-ppm concentrations and the detection limit could extend down to 0.3 ppm, making it a potential candidate for the breath diagnosis of diabetes.