Flexible Ultrathin PolyDVB/EVB Composite Membranes for the Optimization of a Whole Blood Glucose Sensor

An ultrathin composite membrane has been developed as the outer covering barrier in a model amperometric glucose oxidase enzyme electrode. The membrane was formed by cathodic electropolymerization of divinylbenzene/ethylvinylbenzene at the surface of a gold coated polyester support membrane. Permeability coefficients were determined for O₂ and glucose across membranes with a range of polymer thicknesses. Anionic interferents (such as ascorbate), were screened from the working electrode via a charge exclusion mechanism. The enzyme electrode showed an initial 10% signal drift when first exposed to whole human blood over a period of 2 hours, after which responses remained essentially stable. Whole blood patient glucose determinations yielded a correlation coefficient of r²=0.99 compared to standard hospital analyses.     

Polydivinylbenzene/Ethylvinylbenzene Composite Membranes for the Optimization of a Whole Blood Glucose Sensor

A novel ultra thin polydivinylbenzene/ethylvinylbenzene composite membrane has been developed for use as the outer covering barrier in a model amperometric glucose oxidase enzyme electrode. The composite membrane was formed via the cathodic electropolymerization of divinylbenzene/ethylvinylbenzene at the surface of gold sputter coated host alumina membranes, (serving solely as a mechanical support for the thin polymer film). Permeability coefficients were determined for the enzyme substrates, O₂ and glucose, across composite membranes formed with a range of polymer thicknesses. Due to the highly substrate diffusion limiting nature of the composite membrane, it was found that anionic interferents present in blood (such as ascorbate), were effectively screened from the working electrode via a charge exclusion mechanism, in a manner similar to previous findings within our laboratory. The enzyme electrode showed an initial 32% signal drift when first exposed to whole human blood over a period of 2 hours, after which time enzyme electrode responses remained essentially stable. Whole blood patient glucose determinations yielded a correlation coefficient of r²=0.97 in comparison to standard hospital analyses.     

Glucose and urea biosensors based on all solid-state PVC-NH2 membrane electrodes

Miniaturized urea and glucose sensors prepared by immobilization of glucose oxidase or urease directly onto all solid-state contact PVC-NH₂ membrane ammonium and hydrogen ion selective electrodes are described. The resulting biosensing membranes function equivalently to normal PVC membranes in terms of potentiometric response properties. The most important features of the glucose and urea sensors were high sensitivity, long life-time, easily built at a low cost, micro-construction and short response time. The characteristics of the glucose and urea sensors were examined in several buffer solutions at different concentrations and pH values. The influence of immobilization conditions on the dynamic response properties and life-time of the electrodes was studied. Under optimal conditions, the urea electrode showed a linear response between 5×10⁻² and 5×10⁻⁴ M urea, while the glucose electrode showed a linear response between 5×10⁻² and 1×10⁻⁴ M glucose.     

Preparation and characterization of Prussian blue nanowire array and bioapplication for glucose biosensing

Prussian blue nanowire array (PBNWA) was prepared via electrochemical deposition with polycarbonate membrane template for effective modification of glassy carbon electrode. The PBNWA electrode thus obtained was demonstrated to have high-catalytic activity for the electrochemical reduction of hydrogen peroxide in neutral media. This enabled the PBNWA electrode to show rapid response to H₂O₂ at a low potential of −0.1 V over a wide range of concentrations from 1 × 10⁻⁷ M to 5 × 10⁻² M with a high sensitivity of 183 μA mM⁻¹ cm⁻². Such a low-working potential also substantially improved the selectivity of the PBNWA electrode against most electroactive species such as ascorbic acid and uric acid in physiological media. A detection limit of 5 × 10⁻⁸ M was obtained using the PBNWA electrode for H₂O₂, which compared favorably with most electroanalysis procedures for H₂O₂. A biosensor toward glucose was then constructed with the PBNWA electrode as the basic electrode by crosslinking glucose oxidase (GOx). The glucose biosensor allowed rapid, selective and sensitive determination of glucose at −0.1 V. The amperometric response exhibited a linear correlation to glucose concentration through an expanded range from 2 × 10⁻⁶ M to 1 × 10⁻² M, and the response time and detection limit were determined to be 3 s and 1 μM, respectively.     

Structure of the Blend Membrane of Regenerated Silk Fibroin and Glucose Oxidase and Its Application to Glucose Sensor

Abstract

Regenerated silk fibroin was successfully used to immobilize glucose oxidase and the structure of the blend membrane was investigated. The molecules of glucose oxidase in the membrane were in aggregates. Glucose sensor was fabricated by coupling the blend membranes with Clark electrode. Its kinetic constants such as apparent Michael's constants K_m ^app, maximal current response ΔS_max and apparent activation energies Ea of the reaction, effects of pH, temperature and ethanol on the sensor were examined.     

Preparation and application of a new glucose sensor based on iodide ion selective electrode

An electrode for glucose has been prepared by using an iodide selective electrode with the glucose oxidase enzyme. The iodide selective electrode used was prepared from 10% TDMAI and PVC according our previous study. The enzyme was immobilized on the iodide electrode by holding it at pH 7 phosphate buffer for 10 min at room temperature. The H₂O₂ formed from the reaction of glucose was determined from the decrease of iodide concentration that was present in the reaction cell. The iodide concentration was followed from the change of potential of iodide selective electrode. The potential change was linear in the 4×10⁻⁴ to 4×10⁻³ M glucose concentration (75-650 mg glucose/100ml blood) range. The slope of the linear portion was about 79 mV per decade change in glucose concentration. Glucose contents of some blood samples were determined with the new electrode and consistency was obtained with a colorimetric method. The effects of pH, iodide concentration, the amount of enzyme immobilized and the operating temperature were studied. No interference of ascorbic acid, uric acid, iron(III) and Cu(II) was observed. Since the iodide electrode used was not an AgI-Ag₂S electrode, there was no interference of common ions such as chloride present in biological fluids. The slope of the electrode did not change for about 65 days when used 3 times a day.     

Trans-membrane electron transfer in red blood cells immobilized in a chitosan film on a glassy carbon electrode

We have studied the trans-membrane electron transfer in human red blood cells (RBCs) immobilized in a chitosan film on a glassy carbon electrode (GCE). Electron transfer results from the presence of hemoglobin (Hb) in the RBCs. The electron transfer rate (k _s) of Hb in RBCs is 0.42 s^?1, and <1.13 s^?1 for Hb directly immobilized in the chitosan film. Only Hb molecules in RBCs that are closest to the plasma membrane and the surface of the electrode can undergo electron transfer to the electrode. The immobilized RBCs displayed sensitive electrocatalytic response to oxygen and hydrogen peroxide. It is believed that this cellular biosensor is of potential significance in studies on the physiological status of RBCs based on observing their electron transfer on the modified electrode.

Electrochemical Selective Determination of Uranyl Ions Using PVC Membrane Sensor

A UO₂²⁺‐PVC membrane electrode was constructed using 2‐thenoyltrifluoroacetone as ionophore and its electrochemical response performance was characterized. The effect of membrane composition on the electrode performance was studied and best results were obtained using dioctylsebacate as a mediator and potassium tetrakis(4‐chlorophenyl)borate as anion excluder. The optimized UO₂²⁺‐sensor exhibited a Nernstian response with a slope of 29.5±0.5 mV decade⁻¹ over the concentration range 5.0×10⁻⁷−1.0×10⁻¹ mol L⁻¹ at 25 °C with a detection limit of 3.1×10⁻⁷ mol L⁻¹. The optimized electrode showed very good selectivity towards UO₂²⁺ relative to a wide variety of other cations and fast response time. Surface morphology of the optimized membrane electrode at different stages of its development and use was investigated and discussed. Quantum chemical calculations for geometrical optimization of the ionophore were carried out to investigate the interaction between the ionophore and UO₂²⁺ using DFT B3LYP/6‐31++G(d,p) level of theory and the obtained data confirmed the proposed response mechanism. The developed sensor was successfully applied for UO₂²⁺ selective determination in real water samples and the obtained results were compared to those obtained by spectrophotometric method indicating no significant difference.     

Study on Electrosynthesis of Nonconducting Polyaniline Used as a Permselective Membrane in Glucose Oxidase Electrode*

Nonconducting polyaniline (PANI) is electrosynthesized at the Au electrode in 0.05 mol/l aniline solution (pH 7.0) by the potential-scan methods of 0.0–0.9 V (vs. SCE) and = 0.14 V/s. This polyaniline membrane has permselectivity to H₂O₂ and can prevent uric and ascorbic acids from diffusing to electrode surface. The glucose oxidase (GOD) electrode is prepared with the nonconducting polyaniline as an exclusive membrane. The response time, linear response range, and sensitivity of the PANI–GOD electrode are 30–35 s, 0.02–22.0 mmol/l, and 2.5 nA/mmol/l, respectively. Responses for glucose at GOD and PANI–GOD electrodes are similar. But oxidation currents of uric and ascorbic acids at PANI–GOD are smaller. The response currents of these two interferences will be restrained if the PANI–GOD electrode is used to detect the glucose in human blood.     

Glucose nanosensors based on redox polymer/glucose oxidase modified carbon fiber nanoelectrodes

This paper describes glucose nanosensors based on the co-electrodeposition of a poly(vinylimidazole) complex of [Os(bpy)₂Cl]^+/2+ and glucose oxidase (GOD) on a low-noise carbon fiber nanoelectrodes (CFNE). The SEM image shows that the osmium redox polymer/enzyme composite film is uniform. The film modified CFNE exhibits the classical features of a kinetically fast redox couple bound to the electrode surface. A strong and stable electrocatalytic current is observed in the presence of glucose. Under the optimal experimental conditions, the nanosensor offers a highly sensitive and rapid response to glucose at an operating potential of 0.22 V. A wide linear dynamic rang of 0.01-15 mM range was achieved with a detection limit of 0.004 mM. Compared with the conventional gold electrode, the nanosensor possessed higher sensitivity and longer stability. Successful attempts were made in real time monitoring rabbit blood glucose levels.     

Amperometric Biosensors Based on Platinum Nanowires

Abstract

Platinum nanowires (PtNW) were prepared by an electrodeposition strategy using nanopore alumina template. The nanowires prepared were dispersed in chitosan (CHIT) solution and stably immobilized onto the surface of glassy carbon electrode (GCE). The electrochemical behavior of PtNW‐modified electrode and its application to the electrocatalytic reduction of hydrogen peroxide (H₂O₂) are investigated. The modified electrode allows low potential detection of hydrogen peroxide with high sensitivity and fast response time. As an application example, the glucose oxidase was immobilized onto the surface of PtNW‐modified electrode through cross‐linking by glutaric dialdehyde. The detection of glucose was performed in phosphate buffer at –0.2 V. The resulting glucose biosensor exhibited a short response time (<8 s), with a linear range of 10^?5?10^?2 M and detection limit of 5×10^?6 M.     

A mercury(II) ion-selective electrode based on neutral salicylaldehyde thiosemicarbazone

A new ion-selective PVC membrane electrode based on salicylaldehyde thiosemicarbazone as an ionophore is developed successfully as sensor for mercury(II) ions. The electrode shows excellent potentiometric response characteristics and displays a linear log[Hg²⁺] versus EMF response over a wide concentration range of 1.778×10⁻⁶-1.0×10⁻¹ M with Nernstian slope of 29 mV per decade with the detection limit of 1.0×10⁻⁶ M. The response time of the electrode is less than 30 s and the membrane electrode operates well in the pH range of 1.0-3.0. The lifetime of the sensor is about 2 months. The electrode shows better selectivity towards Hg²⁺ ions in comparison with the alkali, alkaline and some heavy metal ions; most of these metal ions do not show significant interference (K^Pot_Hg,M values of the order of 10⁻³-10⁻⁴). The present sensor showed comparable or even better performance vis-à-vis similar PVC based ion-selective electrodes reported in literature. The sensor was also applied as an indicator electrode for potentiometric titration of Hg²⁺ions with I⁻ and Cr₂O₇²⁻.     

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.     

Entrapment of glucose oxidase in non-porous poly(vinyl chloride)

We have used solvent casting techniques to immobilise glucose oxidase (GOD) within unplasticised and plasticised poly(vinyl chloride) (PVC) matrices. The plasticisers studied were the cationic surfactant, tricaprylmethylammonium chloride (Aliquat 336s), the anionic surfactant bis(2-ethylhexyl) hydrogenphosphate (BEP) and the lipid, isopropylmyristate (IPM). The activity of the enzyme-membrane was tested by amperometric electrode. Changes in enzyme-membrane electrode response are rationalised on the basis of membrane permselective properties. The Aliquat and IPM modified PVC membranes gave amplified signals due to better retention and subsequent concentration of the H₂O₂ signal species. Effectively, less was being lost to the bulk solution. In the case of the BEP-modified membrane, while there was a linear step change in response up to 50 mM, at higher concentrations, responses did not reach steady-state; they were characterised by an upward drift in response of 0.050 nA/min. This characteristic is thought to be due to a build up of gluconic acid resulting in a pH reduction in the membrane microenvironment and hydrogen bonding between neighbouring BEP molecules. Under these conditions, we have previously shown that the membrane permeability to hydrophilic species is attenuated and it is tentatively suggested that the upward drift due to the build up of H₂O₂ on the electrode side with less permeating through the acidified membrane into bulk solution.The results were compared against using variously plasticised PVC (but no enzyme entrapped) as an outer membrane of a classical dual-membrane glucose enzyme electrode construct. In the latter case, the enzyme was chemically crosslinked between the membranes using glutaraldehyde.     

Nonenzymatic glucose sensor based on glassy carbon electrode modified with a nanocomposite composed of nickel hydroxide and graphene

We report on a nonenzymatic glucose sensor based on a glassy carbon electrode that was electrochemically modified with a nanocomposite prepared from nickel hydroxide and graphene. Scanning electron microscopy revealed that the nickel hydroxide in the nanocomposite was present in the form of a nanostructure of three-dimensional spheres that were assembled by many densely arranged nanosheets. The electrocatalytic activity of the electrode toward the oxidation of glucose was investigated by chronoamperometry. The current response was linearly related to the glucose concentration in the range from 1 to 10?μM, with a sensitivity of 494?μA?mM^–1?cm^–2 and a correlation coefficient of 0.9990, and a second range (from 10 to 1000?μM with a sensitivity of 328?μA?mM^–1?cm^–2 and a correlation coefficient of 0.9990). The detection limit was 0.6?μM at a signal-to-noise ratio of 3, and the response time was as short as 2?s.

Biosensing Membrane Base on Ferulic Acid and Glucose Oxidase for an Amperometric Glucose Biosensor

A biosensing membrane base on ferulic acid and glucose oxidase is synthesized onto a carbon paste electrode by electropolymerization via cyclic voltammetry in aqueous media at neutral pH at a single step. The developed biosensors exhibit a linear response from 0.082 to 34 mM glucose concentration, with a coefficient of determination R² equal to 0.997. The biosensors display a sensitivity of 1.1 μAmM⁻¹ cm⁻², a detection limit of 0.025 mM, and 0.082 mM as glucose quantification limit. The studies reveal stable, repeatable, and reproducible biosensors response. The results indicate that the novel poly-ferulic acid membrane synthesized by electropolymerization is a promising method for glucose oxidase immobilization towards the development of glucose biosensors. The developed glucose biosensors exhibit a broader linear glucose response than other polymer-based glucose biosensors.     

Response Characteristics of a Glucose Electrode with a Sensing Membrane Prepared by Plasma Polymerization

A glucose electrode was composed of a dissolved oxygen electrode and an immobilized glucose oxidase membrane prepared by plasma polymerization of propargyl alcohol as a monomer. Fairly good precision of the electrode response to sample solutions was obtained by measurements using the steady-state method or the reaction rate method. Activity of the glucose oxidase immobilized within the membrane and mounted on the electrode lasted for 50 consecutive measurements over 5 days, and, if the membrane was stored in a buffer solution of pH 7.0 at a temperature of 0°C, the activity was preserved for more than 2 months. Such immobilization of the glucose oxidase with the plasma polymer effectively suppressed interference from Cu²⁺ions, which would seriously interrupt oxidation of the glucose in homogeneous solutions, in the sample solutions.     

Real‐time Selective Detection of Hydrogen Peroxide Based on a Tantalum Deposited Pencil Lead Electrode for Evaluation of Enzyme Activities

In this study, we have carried out electrodeposition of tantalum (Ta) nanostructures on pencil lead electrode in non‐aqueous media at room temperature by applying a constant potential. The deposited Ta on pencil lead was examined for the catalytic effect regarding hydrogen peroxide (H₂O₂) reduction with voltammetry and amperometry. Ta/pencil lead electrode exhibited amperometric sensitivity of 0.317 μA mM⁻¹ cm⁻² and fast response time of 0.75 s, where selective detection of H₂O₂ was fulfilled without interruption from common electroactive biomaterials such as O₂, uric acid, ascorbic acid, dopamine, acetamidophenol, and glucose. For practical applications, the dynamic concentration changes of H₂O₂ during catalase and glucose oxidase‐involved reactions, either eliminating or producing H₂O₂, were successfully traced in real time with as‐prepared electrode. From the kinetics study for catalase and glucose oxidase, we evaluated Michaelis constants (K _m^app) as 7.8 mM for catalase and 37 mM for glucose oxidase, respectively.     

A Glucose Biosensor Based on Immobilization of Glucose Oxidase into 3D Macroporous TiO2

3D macroporous TiO₂ inverse opals have been derived from a sol‐gel procedure using polystyrene colloidal crystals as templates. EDS and SEM showed a face‐centered cubic (FCC) structure TiO₂ inverse opal was obtained. Glucose oxidase (GOx) was successfully immobilized on the surface of indium‐tin oxide (ITO) electrode modified by TiO₂ inverse opal (TiO_2(IO)). Electrochemical properties of GOx/TiO_2(IO)/ITO electrode were characterized by using the three electrodes system. The result of cyclic voltammetry showed that a couple of stable and well‐defined redox peaks for the direct electron transfer of GOx in absence of glucose, and the redox peak height enhanced in presence of 0.1 μM glucose. Compare with the ordinary structured GOx/TiO₂/ITO electrode, inverse opal structured GOx/TiO_2(IO)/ITO electrode has a better respond to the glucose concentration change. Under optimized experimental conditions of solution pH 6.8 and detection potential at 0.30 V versus saturated calomel electrode (SCE), amperometric measurements were performed. The sensitivity and the detection limit of glucose detection was 151 μA cm^?2 mM^?1 and 0.02 μM at a signal‐to‐noise ratio of 3, respectively. The good response was due to the good biocompatibility of TiO₂ and the large effective surface of the three‐dimensionally ordered macroporous structure.     

A Novel Enzymatic Glucose Biosensor and Nonenzymatic Hydrogen Peroxide Sensor Based on (3‐Aminopropyl) Triethoxysilane Functionalized Reduced Graphene Oxide

In the present study, a novel enzymatic glucose biosensor using glucose oxidase (GOx) immobilized into (3‐aminopropyl) triethoxysilane (APTES) functionalized reduced graphene oxide (rGO‐APTES) and hydrogen peroxide sensor based on rGO‐APTES modified glassy carbon (GC) electrode were fabricated. Nafion (Nf) was used as a protective membrane. For the characterization of the composites, Fourier transform infrared spectroscopy (FTIR), X‐ray powder diffractometer (XRD), and transmission electron microscopy (TEM) were used. The electrochemical properties of the modified electrodes were investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The resulting Nf/rGO‐APTES/GOx/GC and Nf/rGO‐APTES/GC composites showed good electrocatalytical activity toward glucose and H₂O₂, respectively. The Nf/rGO‐APTES/GC electrode exhibited a linear range of H₂O₂ concentration from 0.05 to 15.25 mM with a detection limit (LOD) of 0.017 mM and sensitivity of 124.87 μA mM⁻¹ cm⁻². The Nf/rGO‐APTES/GOx/GC electrode showed a linear range of glucose from 0.02 to 4.340 mM with a LOD of 9 μM and sensitivity of 75.26 μA mM⁻¹ cm⁻². Also, the sensor and biosensor had notable selectivity, repeatability, reproducibility, and storage stability.