Supramolecular immobilization of glucose oxidase on gold coated with cyclodextrin-modified cysteamine core PAMAM G-4 dendron/Pt nanoparticles for mediatorless biosensor design

Cysteamine core polyamidoamine G-4 dendron branched with β-cyclodextrins was chemisorbed on the surface of Au electrodes and further coated with Pt nanoparticles. Adamantane-modified glucose oxidase was subsequently immobilized on the nanostructured electrode surface by supramolecular association. This enzyme electrode was used to construct a reagentless amperometric biosensor for glucose, making use of the electrochemical oxidation of H₂O₂ generated in the enzyme reaction. The amperometric response of the biosensor was rapid (6 s) and a linear function of glucose concentration between 5 and 705 μmol?L^?1. The biosensor had a low detection limit of 2.0 μmol?L^?1, sensitivity of 197 mA?mol^?1?L?cm^?2, and retained 94 % of its initial response after storage for nine days at 4 °C.     

Disposable Amperometric Biosensor Based on Poly‐L‐lysine and Fe3O4 NPs‐chitosan Composite for the Detection of Tyramine in Cheese

An amperometric tyramine biosensor based on poly‐L‐lysine (PLL) and Fe₃O₄ nanoparticles (Fe₃O₄NP) modified screen printed carbon electrode (SPCE) was developed. PLL was formed on the SPCE by the electropolymerization of L‐lysine. Subsequently, Fe₃O₄NP suspension prepared in chitosan (CH) solution was casted onto the PLL/SPCE. Tyrosinase (Ty) enzyme was immobilized onto the modified Fe₃O₄?CH/PLL/SPCE and the electrode was coated with Nafion to fabricate the Ty/Fe₃O₄?CH/PLL/SPCE. Different techniques including scanning electron microscopy, chronoamperometry (i–t curve), cyclic voltammetry and electrochemical impedance spectroscopy were utilized to study the fabrication processes, electrochemical characteristics and performance parameters of the biosensor. The analytical performance of the tyramine biosensor was evaluated with respect to linear range, sensitivity, limit of detection, repeatability and reproducibility. The response of the biosensor to tyramine was linear between 4.9×10^?7–6.3×10^?5 M with a detection limit of 7.5×10^?8 M and sensitivity of 71.36 μA mM^?1 (595 μA mM^?1 cm^?2). The application of the developed biosensor for the determination of tyramine was successfully tested in cheese sample and mean analytical recovery of added tyramine in cheese extract was calculated as 101.2±2.1 %. The presented tyramine biosensor is a promising approach for tyramine analysis in real samples due to its high sensitivity, rapid response and easy fabrication.     

Development of Silver Nanowires Based Highly Sensitive Amperometric Glucose Biosensor

The fabrication of a highly sensitive amperometric glucose biosensor based on silver nanowires (AgNWs) is presented. The electrochemical behavior of glassy carbon electrode modified by Ag NWs exhibits remarkable catalytic performance towards hydrogen peroxide (H₂O₂) and glucose detection. The biosensor could detect glucose in the linear range from 0.005 mM to 10 mM, with a detection limit of 50 µM (S/N=3). The glucose biosensor shows high and reproducible sensitivity of 175.49 µA cm^?2 mM and good stability. In addition, the biosensor exhibits a good anti‐interference ability and favorable stability over relatively long‐term storage (more than 21 days).     

MnO<Subscript>2</Subscript> Nanoparticles and Carbon Nanofibers Nanocomposites with High Sensing Performance Toward Glucose

By combining the advantages of manganese dioxide nanoparticles (MnO₂ NPs) and carbon nanofibers (CNFs), a biosensing electrode surface as a high-performance enzyme biosensor is designed in this work. MnO₂ NPs and CNFs nanocomposites (MnO₂–CNFs) were prepared by using a simple hydrothermal method and then were characterized by scanning electron microscopy, powder X-ray diffraction, fourier transform infrared spectroscopy, energy dispersive spectrometry and electrochemisty. The results showed that MnO₂ NPs are uniformly attached to the surface of CNFs. Meanwhile, the MnO₂–CNFs nanocomposites as a supporting matrix can provide an efficient and advantageous platform for electrochemical sensing applications. On the basis of the improved sensitivity of MnO₂–CNFs modified electrode toward H₂O₂ at low overpotential, a MnO₂–CNFs based glucose biosensor was fabricated by monitoring H₂O₂ produced by an enzymatic reaction between glucose oxidase and glucose. The constructed biosensor exhibited a linear calibration graph for glucose in a concentration range of 0.08–4.6 mM and a low detection limit of 0.015 mM. In addition, the biosensor showed other excellent characteristics, such as high sensitivity and selectivity, short response time, and the relative low apparent Michaelis–Menten constant. Analysis of human urine spiked with glucose at different concentration levels yielded recoveries between 101.0 and 104.8%.     

Development of a Novel Silver Nanoparticles-Enhanced Screen-Printed Amperometric Glucose Biosensor

Abstract

A disposable glucose biosensor is developed by immobilizing glucose oxidase into silver nanoparticles-doped silica sol-gel and polyvinyl alcohol hybrid film on a Prussian blue-modified screen-printed electrode. The silver nanoparticles-enhanced biosensor shows a linear amperometric response to glucose from 1.25 × 10^?5 to 2.56 × 10^?3 with a sensitivity of 20.09 mA M^?1 cm^?2, which is almost double that of the biosensors without silver nanoparticles. The immobilized glucose oxidase retained 91% of its original activity after 30 days of storage in phosphate buffer (pH 6.9; 0.1 M) at 4°C. Blood glucose in a rabbit serum sample was successfully measured with the biosensor.     

Glucose Chemiluminescence Biosensor Based on Covalent Immobilization of Enzyme in Glutaraldehyde-Functionalized Glass Cell and Direct Coupling of Chitosan-Induced Au/Ag alloy Nanoparticles

We report herein the development of a novel glucose chemiluminescence (CL) biosensor based on covalent immobilization of glucose oxidase (GOD) in glutaraldehyde-functionalized glass cell and direct coupling of chitosan-induced Au/Ag alloy nanoparticles on it, and how it may be useful for determination of glucose due to CL detection of enzymatically generated H₂O₂. In addition, the nanoalloy offers excellent catalytic activity toward hydrogen peroxide generation in enzymatic reaction between GOD and glucose and increases stability of covalent-linked enzyme. Chitosan molecules act as both the reducing and stabilizing agents for the preparation of nanoparticles (NPs) and also as a coupling agent between GOD and Au/Ag alloy NPs, which made possible the fabrication of a sensitive, accurate and stable biosensor for glucose. Under the optimum conditions, the biosensor can be used for the determination of glucose in the range of 1.2 × 10^–6 to 6.25 × 10^–3 M with a detection limit of 5.0 × 10^–7 M. The CL biosensor exhibited good storage stability, i.e., 90% of its initial response was retained after 2 months storage at pH 7.0. The present CL biosensor has been used to determine glucose in real serum and urine samples and validated against colorimetric spectrophotometry method.     

Polythiophene–Chitosan Magnetic Nanocomposite as a Novel Sorbent for Disperse Magnetic Solid Phase Extraction of Triazine Herbicides in Aquatic Media

In this paper, polythiophene/chitosan magnetic nanocomposite as a novel adsorbent is proposed for the preconcentration of triazines in aqueous samples prior to gas chromatography. The synthesized nanoparticles, magnetic chitosan and polythiophene–chitosan magnetic nanocomposite were characterized by scanning electron microscopy. The magnetic polythiophene–chitosan nanocomposite containing analytes could be removed from the sample solution by applying a permanent magnet. The major factors influencing the extraction efficiency including desorption conditions, nanocomposite components ratio, sorbent amount, extraction time, ionic strength and sample pH were optimized. The developed method proved to be rather convenient and offers sufficient sensitivity and good reproducibility. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) of the method under optimized conditions were 10–30 and 100 ng L⁻¹, respectively. Under the optimum conditions, good linearity was obtained within the range of 100–5000 ng L⁻¹ for all triazines with correlation coefficients >0.9994. The relative standard deviation at a concentration level of 150 ng L⁻¹ was 7–12 %. Furthermore, the method was successfully applied to the determination of triazines in real samples, where relative recovery percentages of 96–102 % were obtained. Compared with other methods, the current method is characterized by easy, fast separation and low detection limits.

     

Nylon Nanofibrous Biosensors for Glucose Determination

Nanofibrous membranes have been produced by electrospinning to develop first generation glucose biosensors. The direct immobilization of glucose oxidase onto the polyamide nanofibrous surfaces by drop coating revealed a simple and efficient method for the development of sensitive, stable, and reproducible electrochemical biosensors. The biosensor showed a linear response over the range 1–9×10^?3 glucose (R²=0.9997) with a sensitivity of 1.11 μA/mM and a limit of detection of 2.5×10^?6 M (S/N=3). The uncertainty of repeatability was 2% (RSD%, n=30). After one month of storage, the signal decreased of 35%. The recovery of glucose, evaluated in real samples of honey, was 98% (RSD%=1%, n=3).     

Glucose biosensor based on glucose oxidase immobilized on unhybridized titanium dioxide nanotube arrays

A glucose biosensor has been fabricated by immobilizing glucose oxidase (GOx) on unhybridized titanium dioxide nanotube arrays using an optimized cross-linking technique. The TiO₂ nanotube arrays were synthesized directly on a titanium substrate by anodic oxidation. The structure and morphology of electrode material were characterized by X-ray diffraction and scanning electron microscopy. The electrochemical performances of the glucose biosensor were conducted by cyclic voltammetry and chronoamperometry measurements. It gives a linear response to glucose in the 0.05 to 0.65 mM concentration range, with a correlation coefficient of 0.9981, a sensitivity of 199.6 μA mM^?1 cm^?2, and a detection limit as low as 3.8 µM. This glucose biosensor exhibited high selectivity for glucose determination in the presence of ascorbic acid, sucrose and other common interfering substances. This glucose biosensor also performed good reproducibility and long-time storage stability. This optimized cross-linking technique could open a new avenue for other enzyme biosensors fabrication.

Glucose Biosensor Using Glucose Oxidase and Electrospun Mn2O3‐Ag Nanofibers

The highly porous Mn₂O₃‐Ag nanofibers were fabricated by a facile two‐step procedure (electrospinning and calcination). The structure and composition of the Mn₂O₃‐Ag nanofibers were characterized by SEM, TEM, XRD, EDX and SAED. The as‐prepared Mn₂O₃‐Ag nanofibers were then employed as the immobilization matrix for glucose oxidase (GOD) to construct an amperometric glucose biosensor. The biosensor shows fast response to glucose, high sensitivity (40.60 µA mM^?1 cm^?2), low detection limit (1.73 µM at S/N=3), low K_m,app value and excellent selectivity. These results indicate that the novel Mn₂O₃‐Ag nanfibers‐GOD composite has great potential application in oxygen‐reduction based glucose biosensing.     

An amperometric uric acid biosensor based on chitosan-carbon nanotubes electrospun nanofiber on silver nanoparticles

A novel amperometric uric acid biosensor was fabricated by immobilizing uricase on an electrospun nanocomposite of chitosan-carbon nanotubes nanofiber (Chi–CNTsNF) covering an electrodeposited layer of silver nanoparticles (AgNPs) on a gold electrode (uricase/Chi–CNTsNF/AgNPs/Au). The uric acid response was determined at an optimum applied potential of ?0.35 V vs Ag/AgCl in a flow-injection system based on the change of the reduction current for dissolved oxygen during oxidation of uric acid by the immobilized uricase. The response was directly proportional to the uric acid concentration. Under the optimum conditions, the fabricated uric acid biosensor had a very wide linear range, 1.0–400 μmol L^?1, with a very low limit of detection of 1.0 μmol L^?1 (s/n?=?3). The operational stability of the uricase/Chi–CNTsNF/AgNPs/Au biosensor (up to 205 injections) was excellent and the storage life was more than six weeks. A low Michaelis–Menten constant of 0.21 mmol L^?1 indicated that the immobilized uricase had high affinity for uric acid. The presence of potential common interfering substances, for example ascorbic acid, glucose, and lactic acid, had negligible effects on the performance of the biosensor. When used for analysis of uric acid in serum samples, the results agreed well with those obtained by use of the standard enzymatic colorimetric method (P?>?0.05).

A novel amperometric inhibition biosensor based on HRP and gold sononanoparticles immobilised onto Sonogel-Carbon electrode for the determination of sulphides

A novel inhibition biosensor used for the detection of sulphides (Na₂S) has been developed. The biosensor is based on the immobilisation of horseradish peroxidase (HRP) on the Sonogel-Carbon (SNGC) electrode using glutaraldehyde, Poly(4-vinylpyridine) and gold sononanoparticles (AuSNPs). The Poly(4-vinylpyridine) was used due to its high affinity for sulphide anions, while the presence of gold sononanoparticles enhances the electron transfer reaction and improves the analytical performance of the biosensor. The amperometric measurements were performed at an applied potential of ?0.15 V vs. Ag/AgCl in 50 mM sodium acetate buffer solution pH = 6.0. The apparent kinetic parameters (K_mapp, V_max) of immobilised HRP were calculated in the absence of inhibitor (sulphide) using caffeic acid as substrate. Under the optimal experimental conditions, the determination of sulphide can be achieved in a dynamic range of 0.4–2.8 µM with a low limit of detection of 0.15 µM. The electrochemical impedance spectroscopy (EIS) was also used to characterise the interactions of substrate and inhibitor with the enzyme-modified electrode. The developed biosensor exhibited high sensitivity, selectivity and stability, and can be successfully applied to the detection of sulphide in water.     

Amperometric biosensor based on hemoglobin immobilized on Cu2S nanorods/nafion nanocomposite film for the determination of polyphenols

A novel biosensor was fabricated based on hemoglobin (Hb) immobilized onto cuprous sulfide (Cu₂S) nanorods/nafion nanocomposite film for the detection of polyphenols in the presence of hydrogen peroxide (H₂O₂). The nanostructured inorganic–organic hybrid material formed by Cu₂S nanorods and nafion provided a biocompatible microenvironment for Hb and increased the sensitivity for polyphenols detection. The modified electrodes were characterized by electrochemical impedance spectroscopy and linear sweep voltammetry. Parameters such as pH, H₂O₂ concentration, and the applied potential were optimized. Under optimum conditions, the biosensor gave linear response ranges of 7.0–110, 0.6–10, and 8–100 μM for catechol, hydroquinone, and resorcin, with the detection limits of 0.5, 0.03, and 0.6 μM (S/N?=?3), respectively. The developed biosensor exhibited a short response time within only 8 s with good stability and reproducibility. Such a novel biosensor showed great promise for rapid, simple analysis of polyphenols contents in real samples.     

Laccase-based amperometric biosensor enhanced by Ni/Au/PPy-COOH multisegmental nanowires for selective dopamine detection

One-dimensional Ni/Au/PPy-COOH nanowires with multiple segments were synthesized in this study. Smooth surfaces and magnetic properties of nanowires were investigated by scanning transmission electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), and Electron Spin Resonance (ESR) techniques. The nanowires were used to modify the screen-printed electrode surface and as a micro-environment for Trametes versicolor laccase. The ability of this enzyme biosensor to detect dopamine change in human biological samples was demonstrated by a wide linear range (0.01–50 μM) and a low LOD (2.265 nM). In addition, the biosensor exhibited excellent selectivity allowing the detection of dopamine in the presence of ascorbic acid, uric acid, L-Cys, serotonin, and glucose, with high sensitivity of reduction currents obtained at −0.2 V (vs. Ag/AgCl). The proposed biosensor allowed the detection of dopamine in commercial serum and artificial urine with recovery values close to 100 %. It also demonstrated reproducibility, reusability, and long-term storage stability. The sensitivity, K_m^app, and I_max values of the biosensor were determined as 2.05 μM and 1.03 μA, respectively. The LAC-Ni/Au/PPy-COOH/NAF/SPE biosensor is a reliable design for detecting dopamine with a wide linear range.     

Laccase-Nafion Based Biosensor for the Determination of Polyphenolic Secondary Metabolites

A laccase-based biosensor was developed by specific enzyme adsorption on screen-printed working electrodes of DROPSENS cells, and stabilized with Nafion 0.1% membrane. The electrode was characterized with respect to response time, sensitivity, linear range, detection limit, pH dependence, interferences, and long-term stability. The tested substrates were catechol, rosmarinic acid, caffeic acid, chlorogenic acid, and gallic acid. The optimized biosensor proved the following characteristic performances: the apparent Michaelis Menten calculated considering rosmarinic acid substrate 8.3 × 10^?6 mol L^?1 (r = 0.995, n = 6); the dynamic range of biosensor response for rosmarinic acid 7 × 10^?7 ? 1.5 × 10^?6 mol L^?1; the detection limit for rosmarinic acid 1.19 × 10^?7 mol L^?1 (RSD = 1.08%, n = 3). It was noticed that the biosensor reaches systematically 90% to 94.3% from the response obtained by LC-DAD-ESI-MS for real samples.     

Sol–gel immobilized enzymatic glucose biosensor on gold interdigitated array (IDA) microelectrode

An enzymatic glucose biosensor with good sensitivity, selectivity and stability employing interdigitated array microelectrode (IDA μ-electrode) was reported. IDA μ-electrode was prepared by photolithography method with its surface immobilized with a layer of glucose oxidase (GOx), entrapped in a three-dimensional network composed of chitosan and tetraethyl orthosilicate sol–gel. The surface of the as-prepared IDA μ-electrode was characterized by scanning electron microscope, electron spectroscopy for chemical analysis, and atomic force microscopy. The experimental parameters for the best glucose sensing performance were optimized according to the loading of GOx, the applied voltages, the concentration of mediator, and the pH for glucose detection. The resulted biosensor exhibited a good response to glucose with a wide linear range from 0 to 35 mM and a low detection limit of 1 mM. The glucose sensor also showed a short response time (within 5 s) that the fast response was reflected by the small Michaelis–Menten constant (K_M ^app) with a value of 2.94 mM. The reported glucose biosensor exhibited good sensitivity (8.74 μA/mM.cm²), reproducibility, and stability.     

Catalyzed Determination of Glucose with a Mimic Enzyme Constructed of Bis‐[‐6‐O‐(‐β‐ethyloic‐butanedioic Acid‐1,4‐ester‐4‐)]β‐Cyclodextrin · Fe3+

Abstract

Catalyzed determination of glucose with mimic glucose oxidase is constructed by the reaction of β‐cyclodextrin, maleic anhydride, and chloroacetic acid with iron trichloride in hydrogen peroxide. The method is simple and convenient, and sensitivity and repeatability are ideal. Beer's law is obeyed in a concentration range of 30–197 µg · ml^?1 glucose with an excellent correlation coefficient (r=0.9994), while the detection limit is 4.10 µg · ml^?1, the RSD is 0.98% (n=8). The recovery of sample is 95.8–103.1%.     

Pt nanoparticles modified Au nanowire array for amperometric and potentiometric detection of glucose

A new glucose biosensor, based on the modification of highly ordered Au nanowire arrays (ANs) with Pt nanoparticles (PtNPs) and subsequent surface adsorption of glucose oxidase (GOx), is described. Morphologies of ANs and ANs/PtNPs were observed by scanning electron microscope. The electrochemical properties of ANs, ANs/GOx, ANs/PtNPs, and ANs/PtNPs/GOx electrodes were compared by cyclic voltammetry. Results obtained from comparison of the cyclic voltammograms show that PtNPs modification enhances electrochemical catalytic activity of ANs to H₂O₂. Hence, ANs/PtNPs/GOx biosensor exhibits much better sensing to glucose than ANs/GOx. Optimum deposition time of ANs/PtNPs/GOx biosensor for both amperometric and potentiometric detection of glucose was achieved to be 150 s at deposition current of 1?×?10^?6 A. A sensitivity of 0.365 μA/mM with a linear range from 0.1 to 7 mM was achieved for amperometric detection; while for potentiometric detection the sensitivity is 33.4 mV/decade with a linear range from 0.1 to 7 mM.     

Amperometric Glucose Biosensor Based on Ultrafine Platinum Nanoparticles

Abstract

In the present paper the ultrafine and highly dispersed platinum nanoparticles (average size 3 nm) were used for the construction of a glucose biosensor in a simple method. An excellent response to glucose has been obtained with a high sensitivity (137.7 µA mM^?1 cm^?2) and fast response time (5 s). The biosensor showed a detection limit of 5 µM (at the ratio of signal to noise, S/N=3) and a linear range form 0.2 to 3.2 mM with a correlation coefficient r=0.999. The apparent Michaelis–Menten constant (k _m) and the maximum current were estimated to be 9.36 and 1.507 mA mM^?1 cm^?2, respectively. In addition, effects of pH value, applied potential and the interferents on the amperometric response of the sensor were investigated and discussed.     

Pure copper vs. mixed copper and palladium hexacyanoferrates for glucose biosensing applications

A glucose amperometric biosensor was developed. Glucose oxidase enzyme was immobilized by means of a Nafion membrane on glassy carbon modified with an electrochemically deposited mixed Cu and Pd hexacyanoferrate (CuPdHCF). According to the data provided by X-ray atomic spectroscopy measurements, this Cu- and Pd-based hexacyanoferrate is likely to be a mixture of single CuHCF and PdHCF pure phases. The biosensor performances were evaluated by recording the steady-state currents due to submillimolar additions of glucose to a potassium buffer solution (pH 5.5) and exploiting the electrocatalytic reduction of the enzymatically produced hydrogen peroxide. The CuPdHCF-based biosensor exhibited a sensitivity of 8.1?±?0.6 A M^?1 m^?2, a limit of detection of 1.4?×?10^?5 M, and a linear response range extending between 5?×?10^?5 and 4?×?10^?4 M, with a dynamic response range up to 4?×?10^?3 M glucose. Electrode sensitivity and signal stability resulted more satisfactory as compared to those of a CuHCF-based biosensor fabricated according to the same procedure. The selectivity was investigated through an interference study. The response to easily oxidizable species was found to be low enough to allow glucose determination in biological samples.