Enzyme‐free Glucose Sensor Fabricated by Nanorods Decorated Nanopore Arrays on Biomedical Stainless Steel

A novel enzyme‐free glucose sensor was proposed by preparation of nanorods decorated nanopore arrays (NRs/NPAs) on 316L stainless steel simply by electrochemical treatments. The NRs/NPAs sensor displays two linear ranges towards glucose determination, one range from 1 μM to 1.2 mM with a sensitivity of 202.2 μA ? cm^?2 ? mM^?1, another range from 1.2 mM to 7.7 mM with a sensitivity of 59.18 μA?cm^?2 ? mM^?1. The detection limit is 0.5 μM. The NRs/NPAs electrode exhibits excellent stability, good selectivity and reproducibility, rendering it suitable for glucose monitoring.     

Electrochemical Fabrication of Cobalt Oxides/Nanoporous Gold Composite Electrode and its Nonenzymatic Glucose Sensing Performance

A nonenzymatic glucose sensor was successfully established by electrochemically decorating cobalt oxides (CoO_x) on a nanoporous gold electrode (NPG) using cobalt hexacyanoferrate (CoHCF) as a precursor. It exhibited high sensitivity and long‐term stability as well as satisfactory quantification of glucose concentration in human serum samples. The morphology and surface analysis of the resulting CoO_x/NPG were carefully characterized. Two detection methods, cyclic voltammetry and amperometry, were employed to evaluate the performance of CoO_x/NPG towards glucose sensing in alkaline solution. Using cyclic voltammetry, at ?0.5 V, the glucose partial oxidation peak current is linear to the glucose concentration up to 14 mM with a sensitivity of 283.7 µA mM^?1 cm^?2. A linear amperometric response at 0.55 V was obtained in the glucose concentration range from 2 µM to 2 mM with a sensitivity of 2025 µA mM^?1 cm^?2 and a response time <3 s.     

α‐Fe2O3 Film with Highly Photoactivity for Non‐enzymatic Photoelectrochemical Detection of Glucose

A non‐enzyme photoelectrochemical (PEC) glucose sensor based on α‐Fe₂O₃ film is investigated. The α‐Fe₂O₃ film was fabricated via a simple spin coating method. The proposed glucose sensor exhibits good selectivity, a fast response time of <5 s, a linear range of 0.05 to 6.0 mM, sensitivity of 17.23 μA mM^?1 cm^?2 and a detection limit of 0.05 μM. Meanwhile, the excellent performances of the α‐Fe₂O₃ sensor were obtained in reproducibility and the long‐term stability under ambient condition. The linear amperometric response of the sensor covers the glucose levels in physiological and clinical for diabetic patients. Therefore, this non‐enzyme PEC sensor based on α‐Fe₂O₃ film has a great potential application in the development of glucose sensors.     

Glucose Biosensors Based on Electrodes Modified with Ferrocene Derivatives Intercalated into Mg/Al Layered Double Hydroxides

Two amperometric biosensors based on glassy carbon electrodes (GC) modified with Mg/Al layered double hydroxides (LDHs) containing ferrocene‐carboxylate (Fc? CO₂H) or ferrocene‐sulfonate (Fc? SO₃H), as interlayer anions, and glucose oxidase (GOx) are presented. Amperometric detection of glucose involves the electrochemical oxidation of H₂O₂ mediated by the ferrocene derivative. Optimization of the biosensors construction and of the operative conditions was investigated and is discussed herein. The performances of the two biosensors were evaluated by chronoamperometry, working at low anodic potentials (+0.400 V for Fc? CO₂H and +0.500 V for Fc? SO₃H vs. SCE). The linearity extended up to 1.5 mM and 10.0 mM in batch and in flow conditions, respectively, for both biosensors, whereas the sensitivity was higher for the one based on Fc? CO₂H (4.8±0.3 versus 2.0±0.3 μA mM^?1cm^?2 in batch mode, and 63.9±0.4 versus 25.8±0.4 μA mM^?1cm^?2 in flow mode). The biosensors display rapid response time (less than 20 s), good reproducibility, as well as good operational stability. Glucose can be accurately determined in the presence of the most common interferences that coexist in blood serum if an oxidative membrane containing nanoparticles of MnO₂ is applied on the biosensors' surface.     

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.     

Hydrothermal Synthesis of Titanium‐Supported Nickel Nanoflakes for Electrochemical Oxidation of Glucose

Titanium‐supported nanoscale flaky nickel electrode (nanoNi/Ti) was prepared by a hydrothermal process using hydrazine hydrate as a reduction agent. Its electrocatalytic activity as an electrocatalyst for the electrooxidation of glucose was evaluated in alkaline solutions using cyclic voltammetry (CV), chronoamperometric responses (CA) and electrochemical impedance spectra (EIS). The nanoNi/Ti electrode exhibits significantly high current density of glucose oxidation. A high catalytic rate constant of 1.67×10⁶ cm³ mol^?1 s^?1 was calculated from amperometric responses on the nanoNi/Ti electrode. Low charge transfer resistances on the nanoNi/Ti in 0.5 M NaOH containing various concentrations of glucose were obtained according to the analysis for EIS. Furthermore, amperometric data show a linear dependence of the current density for glucose oxidation upon glucose concentration in the range of 0.05–0.6 mM with a sensitivity of 7.32 mA cm^?2 mM^?1. A detection limit of 0.0012 mM (1.2 μM) M glucose was found. Results show that the prepared nanoNi/Ti electrode presents high electrocatalytic activity for glucose oxidation.     

An enzyme-free highly glucose-specific assay using self-assembled aminobenzene boronic acid upon polyelectrolytes electrospun nanofibers-mat

A highly selective enzyme-free amperometric glucose sensor based on electrostatic self-assembling of 3-aminobenzene boronic acid (ABBA) onto a poly(styrene-co-acrylamide)/polystyrene sulfonic acid (PSA/PSSA) electrospun nanofibers-mat was investigated. Emerging ability of phenylboronic acid to bind with the diols of sugars has been extended for rapid response of glucose with a pH-sensitive redox mediator, hematein natural dye. ABBA was adsorbed on the PSA/PSSA nanofibers-mat/Pt-disc electrode that resulted in an ABBA/PSA/PSSA glucose active electrode. The interaction of ABBA onto the PSA/PSSA nanofibers-mat/Pt-disc electrode was characterized with Fourier transform infrared spectroscopy (FT-IR), ζ-potential, scanning electron microscopy (SEM), contact angle and cyclic voltammetry (CV) measurements. The prepared enzyme-free sensor exhibited a fast amperometric response, i.e., about 4 s and linearity ranging from 0.75 to 14 mM to glucose with a sensitivity of 0.987 μA mM⁻¹ cm⁻². Compared to other types of glucose biosensors viz. use glucose oxidase as sensing elements, present glucose sensor offers basic advantages including ease of fabrication, high affinity-selectivity to the glucose upon the electrode surface and quick response.     

Nonenzymatic Glucose Detection with Good Selectivity Against Ascorbic Acid on a Highly Porous Gold Electrode Subjected to Amalgamation Treatment

A nonenzymatic glucose sensor with good selectivity for the ascorbic acid oxidation is presented. After the gold polycrystalline electrode was subjected to amalgamation treatment, two advantageous effects were observed. One is the enhancement of the surface roughness and the other is an increase in the catalytic current in the glucose oxidation. Besides the known first effect, the latter provided another advantageous effect in a fabrication of nonenzymatic glucose sensor. Using a gold electrode subjected to amalgamation treatment for 60 s, two calibration curves for glucose oxidation at two different potentials of ?0.1 V and 0.25 V were obtained and compared. At the potential of ?0.1 V, at which no ascorbic acid was oxidized and no interference effect was observed, a current sensitivity of 16 μA cm^?2 mM^?1 from zero to 10 mM glucose concentration range was obtained. At the other potential of 0.25 V, at which ascorbic acid was easily oxidized, a satisfactory calibration curve with negligible ascorbic acid interference was also obtained together with a more enhanced current sensitivity of 32 μA cm^?2 mM^?1.     

Gold Nanoparticles Modified Titania Nanotube Arrays for Amperometric Determination of Ascorbic Acid

Development and use of highly ordered, vertically aligned TiO₂ nanotube arrays modified with gold nanoparticles for the selective detection of ascorbic acid (AA) in the presence of uric acid and glucose are reported here. Gold nanoparticles were electrodeposited on the Nanotube arrays by CV. The sensor was characterized using SEM, EDS, CV, and EIS. It showed very good performance with a sensitivity of 46.8 μA mM^?1 cm^?2, response time below 2 seconds and linearity in the range of 1 μM to 5 mM with a detection limit of 0.1 μM and was tested for the AA concentration in pharmaceutical preparations.     

Synthesis of Novel CuO Nanosheets with Porous Structure and Their Non‐Enzymatic Glucose Sensing Applications

Novel CuO thin films composed of porous nanosheets were in situ formed on indium tin oxide (ITO) by a simple, low temperature solution method, and used as working electrodes to construct nonenzymatic glucose sensor after calcinations. Cyclic voltammetry revealed that the CuO/ITO electrode calcinated at 200 °C exhibited better electrocatalytic activity for glucose. For the amperometric glucose detection, such prepared electrode showed low operating potential of 0.35 V and high sensitivity of 2272.64 μA mM^?1 cm^?2. Moreover, the CuO/ITO electrode also showed good stability, reproducibility and high anti‐interference ability. Thus, it is a promising material for the development of non‐enzymatic glucose sensors.     

Amperometric nonenzymatic glucose sensor based on a glassy carbon electrode modified with a nanocomposite made from nickel(II) hydroxide nanoplates and carbon nanofibers

We report on a highly sensitive and selective nonenzymatic glucose sensor based on a glassy carbon electrode modified with a composite prepared from nickel(II) hydroxide nanoplates and carbon nanofibers. The nanocomposite was characterized by scanning electron microscopy and powder X-ray diffraction. Electrodes modified with pure Ni(OH)₂ and with the nanocomposite were characterized by electrochemical impedance spectroscopy. Cyclic voltammetric and amperometric methods were used to investigate the catalytic properties of the modified electrodes for glucose electrooxidation in strongly alkaline solution. The sensor exhibits a wide linear range (from 0.001 to 1.2 mM), a low detection limit (0.76 μM), fast response time (< 5 s), high sensitivity (1038.6 μA?·?mM^?1?·?cm^?2), good reproducibility, and long operational stability. Application of the nonenzymatic sensor for monitoring glucose in real samples was also demonstrated.

Commercial Copper Foam as an Effective 3D Porous Electrode for Nonenzymatic Glucose Detection

Commercially available copper foam (CF) was used as a 3D porous electrochemical sensing platform for nonenzymatic glucose detection. CF shows high electrocatalytic activity towards glucose oxidation and can be used directly for glucose electrochemical sensing without any pretreatment. The sensor exhibits high performance towards glucose in 0.1 M NaOH solution with the linear range from 1 μM to 0.5 mM, the sensitivity of 5.85 mA mM^?1 cm^?2 and the detection limit of 0.5 μM (S/N=3) simultaneously. Furthermore, the sensor shows a high selectivity for glucose against the common interferences and good reliability for glucose detection in human serum samples.     

Non-enzymatic analysis of glucose on printed films based on multi-walled carbon nanotubes

We report on the fabrication of an enzyme–free electrochemical sensor for glucose based on a printed film consisting of multi–walled carbon nanotubes (MWCNTs). The MWCNT–based film can be produced by means of a flexographic printing process on a polycarbonate (PC) substrate. The electrochemical response of the MWCNT–based film (referred to as MWCNT–PC) towards the oxidation of glucose at pH 7 was studied by means of cyclic voltammetry and electrochemical impedance spectroscopy. The MWCNT–PC film exhibits substantial electrocatalytic activity towards the oxidation of glucose at an anodic potential of 0.30?V (vs. Ag/AgCl). The findings reveal that the MWCNT–PC film enables non–enzymatic sensing of glucose with a detection limit as low as 2.16?μM and a sensitivity of 1045?μA?mM^?1?cm^?2.

Selective and sensitive electrochemical detection of glucose in neutral solution using platinum-lead alloy nanoparticle/carbon nanotube nanocomposites

Electrodeposition of Pt-Pb nanoparticles (PtPbNPs) to multi-walled carbon nanotubes (MWCNTs) resulted in a stable PtPbNP/MWCNT nanocomposite with high electrocatalytic activity to glucose oxidation in either neutral or alkaline medium. More importantly, the nanocomposite electrode with a slight modification exhibited high sensitivity, high selectivity, and low detection limit in amperometric glucose sensing at physiological neutral pH (poised at a negative potential). At +0.30 V in neutral solution, the nanocomposite electrode exhibited linearity up to 11 mM of glucose with a sensitivity of 17.8 μA cm⁻² mM⁻¹ and a detection limit of 1.8 μM (S/N = 3). Electroactive ascorbic acid (0.1 mM), uric acid (0.1 mM) and fructose (0.3 mM) invoked only 23%, 14% and 9%, respectively, of the current response obtained for 3 mM glucose. At −0.15 V in neutral solution, the electrode responded linearly to glucose up to 5 mM with a detection limit of 0.16 mM (S/N = 3) and detection sensitivity of ∼18 μA cm⁻² mM⁻¹. At this negative potential, ascorbic acid, uric acid, and fructose were not electroactive, therefore, not interfering with glucose sensing. Modification of the nanocomposite electrode with Nafion coating followed by electrodeposition of a second layer of PtPbNPs on the Nafion coated PtPbNP/MWCNT nanocomposite produced a glucose sensor (poised at −0.15 V) with a lower detection limit (7.0 μM at S/N = 3) and comparable sensitivity, selectivity and linearity compared to the PtPbNP/MWCNT nanocomposite. The Nafion coating lowered the detection limit by reducing the background noise, while the second layer of PtPbNPs restored the sensitivity to the level before Nafion coating.     

Pt Nanoparticle‐modified Carbon Fiber Microelectrode for Selective Electrochemical Sensing of Hydrogen Peroxide

We report a simple approach to the production of carbon fiber‐based amperometric microbiosensors for selective detection of hydrogen peroxide (H₂O₂), which was achieved by electrometallization of carbon fiber microelectrodes (CFMs) by electrodeposition of Pt nanoparticles. The Pt‐carbon hybrid sensing interface provided a sensitivity of 7711±587 μA ? mM^?1 ? cm^?2, a detection limit of 0.53±0.16 μM (S/N=3), a linear range of 0.8 μM–8.6 mM, and a response time of <2 sec. The morphologies of the Pt nanoparticle‐modified CFMs were characterized by scanning electron microscopy. To achieve selectivity, permseletive layers, polyphenylenediamine (PPD) and Nafion, were deposited resulting in exclusion of the anionic and cationic interferents, ascorbic acid and dopamine, respectively, at their physiologically relevant concentrations. The resultant sensors displayed a sensitivity to hydrogen peroxide of 1381±72 μA ? mM^?1 ? cm^?2, and a detection limit of 0.86±0.19 μM (S/N=3). This simple and rapid metallization method converts carbon fiber microelectrodes, which are readily accessible, to microscale Pt electrodes in 2 min, providing a platform for oxidase‐based amperometric biosensors with improved spatial resolution over more commonly used platinum electrode array microprobes.     

An electrochemical sensor for sensitive determination of nitrites based on Ag-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-graphene oxide magnetic nanocomposites

A functional Ag-Fe₃O₄-grapheme oxide magnetic nanocomposite was synthesized and used to prepare a nitrite sensor. Morphology and composition of the nanocomposites were characterized by a transmission electron microscope, UV-VIS spectroscopy, X-ray diffraction, and Fourier transform infrared spectra. Electrochemical investigation indicated that the nanocomposites possess excellent electrochemical oxidation ability towards nitrites. The sensor exhibited two linear ranges: one from 0.5 µM to 0.72 mM with a correlation coefficient of 0.996 and sensitivity of 1996 µA mM^?1 cm^?2; the other from 0.72 mM to 8.15 mM with a correlation coefficient of 0.998 and sensitivity of 426 µAmM^?1 cm^?2. The limit of detection of this sensing system was 0.17 µM at the signal-to-noise ratio of 3. Additionally, the sensor exhibited long-term stability, good reproducibility, and anti-interference.     

Minimally‐invasive Microneedle‐based Biosensor Array for Simultaneous Lactate and Glucose Monitoring in Artificial Interstitial Fluid

Here we report the first mediated pain free microneedle‐based biosensor array for the continuous and simultaneous monitoring of lactate and glucose in artificial interstitial fluid (ISF). The gold surface of the microneedles has been modified by electrodeposition of Au‐multiwalled carbon nanotubes (MWCNTs) and successively by electropolymerization of the redox mediator, methylene blue (MB). Functionalization of the Au‐MWCNTs/polyMB platform with the lactate oxidase (LOX) enzyme (working electrode 1) and with the FAD‐Glucose dehydrogenase (FADGDH) enzyme (working electrode 2) enabled the continuous monitoring of lactate and glucose in the artificial ISF. The lactate biosensor exhibited a high sensitivity (797.4±38.1 μA cm^?2 mM^?1), a good linear range (10–100 μM) with a detection limit of 3 μM. The performance of the glucose biosensor were also good with a sensitivity of 405.2±24.1 μA cm^?2 mM^?1, a linear range between 0.05 and 5 mM and a detection limit of 7 μM. The biosensor array was tested to detect the amount of lactate generated after 100 minutes of cycling exercise (12 mM) and of glucose after a normal meal for a healthy patient (10 mM). The results reveal that the new microneedles‐based biosensor array seems to be a promising tool for the development of real‐time wearable devices with a variety of sport medicine and clinical care applications.     

Single step modification of copper electrode for the highly sensitive and selective non-enzymatic determination of glucose

A non-enzymatic sensor was developed for the determination of glucose in alkaline medium by anodisation of copper in sodium potassium tartrate solution. The morphology of the modified copper electrode was studied by scanning electron microscopy, and its electrochemical behavior by cyclic voltammetry and electrochemical impedance spectroscopy. The electrode enables direct electrocatalytic oxidation of glucose on a CuO/Cu electrode at 0.7 V in 0.1 M sodium hydroxide. At this potential, the sensor is highly selective to glucose even in the presence of ascorbic acid, uric acid, or dopamine which are common interfering species. The sensor displays a sensitivity of 761.9 μA mM^?1 cm^?2, a linear detection range from 2 μM to 20 mM, a response time of <1 s, and a detection limit of 1 μM (S/N = 3). It was tested for determination of glucose level in blood serum.     

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.     

Nonenzymatic Electrochemical Glucose Sensor Based on Pt Nanoparticles/Mesoporous Carbon Matrix

A nonenzymatic amperometric sensor for sensitive and selective detection of glucose has been constructed by using highly dispersed Pt nanoparticles supported onto mesoporous carbons (MCs). The Pt nanoparticles/mesoporous carbons (Pt/MCs) composites modified electrode displayed high electrocatalytic activity towards the oxidation of glucose. At an applied potential of 0.1 V, the Pt/MCs electrode has a linear dependence (R=0.996) in the glucose concentration up to 7.5 mM with a sensitivity of 8.52 mA M^?1 cm^?2. The Pt/MCs electrode has also shown highly resistant toward poisoning by chloride ions and without interference from the oxidation of common interfering species.