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Near-field communication (NFC) was used to control a portable glucose biosensor for diabetes diagnosis. The system comprised a smartphone and an NFC potentiostat connected to a screen-printed carbon electrode (SPCE) modified with Prussian blue-graphene ink and functionalized with gold nanoparticles-embedded poly (3,4ethylene dioxythiophene):polysulfonic acid coated with glucose oxidase (GOx-AuNPs-PEDOT:PSS/PB-G). GOx catalyzed the glucose redox reaction while the conductivity and sensitivity of the AuNPs-PEDOT:PSS composite enhanced electron transfer to the PB‐G, which was used as a mediator. The fabrication process was characterized by scanning electron microscopy (SEM) with energy dispersibe x-ray analysis (EDX). The platform was electrochemically characterized by electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The NFC biosensing device was then applied to quantify glucose in human blood serum by amperometry. The linear concentration range and detection limit for glucose were 0.5–500 μM and 0.15 μM, respectively. The accuracy of the device was good and results were in agreement with the results obtained from the standard hospital method. This NFC glucose sensing device can be a simple, sensitive, selective and portable platform for medical diagnosis. [Display omitted] • A smartphone-based biosensor was developed for real-time diabetes diagnosis. • Prussian blue mediates a glucose oxidase-catalyzed redox reaction. • The device exhibited good linearity and selectivity with a low detection limit. • Near-field communication transmits blood glucose data at point of care. [ABSTRACT FROM AUTHOR]

We report a novel amperometric glucose biosensor based on glucose oxidase (GOx) immobilized on a carbon nanotube (CNTs)–poly(diallyldimethyl-ammonium chloride) (PDDA)–platinum nanoparticle (PtNPs) modified carbon-paste electrode (CNTs–PDDA–PtNPs/CPE). The CNTs–PDDA–PtNPs composite materials were characterized by TEM and electrochemical techniques. Cyclic voltammetric results reveal direct electron transfer of the immobilized GOx, indicated by two quasi-reversible redox peaks at a potential of 0.37 V (vs. Ag/AgCl) in phosphate buffered solution (PBS) (0.10 M, pH 7). The biosensor provides good glucose oxidation activity and retention of GOx electrocatalytic activity due to CNTs–PDDA–PtNPs enhancement of the redox response. The carbon paste electrode was installed as working electrode in a flow through electrochemical cell of a flow injection (FI) system. Glucose was quantified using amperometric measurements at 0.5 V vs. Ag/AgCl and PBS carrier (0.10 M, pH 7.0) at a flow rate of 1.0 mL min −1 . The linear working ranges for glucose measurements were 0.1–3 mM ( r 2 =0.995) and 5–100 mM ( r 2 =0.997), with corresponding sensitivities of 0.127 and 0.060 (μA s) mM −1 , respectively. The system provides good precision of 2.8% R.S.D with a calculated detection limit (3 S/N) of 15 μM. The proposed method was successfully applied to determination of glucose in food and pharmaceutical samples with throughput of 200 samples h −1 . [ABSTRACT FROM AUTHOR]

A novel amperometric glucose biosensor was proposed in flow injection analysis (FIA) system using glucose oxidase (GOD) and Quantum dot (ZnS–CdS) modified Pencil Graphite Electrode (PGE). After ZnS–CdS film was electrochemically deposited onto PGE surface, GOD was immobilized on the surface of ZnS–CdS/PGE through crosslinking with chitosan (CT). A pair of well-defined reversible redox peak of GOD was observed at GOD/CT/ZnS–CdS/PGE based on enzyme electrode by direct electron transfer between the protein and electrode. Further, obtained GOD/CT/ZnS–CdS/PGE offers a disposable, low cost, selective and sensitive electrochemical biosensing of glucose in FIA system based on the decrease of the electrocatalytic response of the reduced form of GOD to dissolved oxygen. Under optimum conditions (flow rate, 1.3 mL min −1 ; transmission tubing length, 10 cm; injection volume, 100 μL; and constant applied potential, −500 mV vs. Ag/AgCl), the proposed method displayed a linear response to glucose in the range of 0.01–1.0 mM with detection limit of 3.0 µM. The results obtained from this study would provide the basis for further development of the biosensing using PGE based FIA systems. [ABSTRACT FROM AUTHOR]

Abstract: A highly-sensitive glucose biosensor amenable to ultra-miniaturisation was fabricated by immobilisation of glucose oxidase (GOx), onto a poly(2,6-diaminopyridine)/multi-walled carbon nanotube/glassy carbon electrode (poly(2,6-DP)/MWNT/GCE). Cyclic voltammetry was used for both the electrochemical synthesis of poly-(2,6-DP) on the surface of a MWNT-modified GC electrode, and characterisation of the polymers deposited on the GC electrode. The synergistic effect of the high active surface area of both the conducting polymer, i.e., poly-(2,6-DP) and MWNT gave rise to a remarkable improvement in the electrocatalytic properties of the biosensor. The transfer coefficient (α), heterogeneous electron transfer rate constant and Michaelis–Menten constant were calculated to be 0.6, 4s−1 and 0.20mM at pH 7.4, respectively. The GOx/poly(2,6-DP)/MWNT/GC bioelectrode exhibited two linear responses to glucose in the concentration ranging from 0.42μM to 8.0mM with a correlation coefficient of 0.95, sensitivity of 52.0μAmM−1 cm−2, repeatability of 1.6% and long-term stability, which could make it a promising bioelectrode for precise detection of glucose in the biological samples. [Copyright &y& Elsevier]

Abstract: A mediatorless glucose biosensor was developed by the immobilization of glucose oxidase (GOx) to graphene-functionalized glassy carbon electrode (GCE). The surface of GCE was functionalized with graphene by incubating it with graphene dispersed in 3-aminopropyltriethoxysilane (APTES), which acted both as a dispersion agent for graphene and as an amine surface modification agent for GCE and graphene. This was followed by the covalent binding of GOx to graphene-functionalized GCE using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) based crosslinking. Graphene provided signal enhancement by providing greater surface area for GOx binding, while APTES-functionalization led to a higher GOx immobilization density by providing free amino groups for crosslinking. The developed biosensor used a redox potential of −0.45V (vs. Ag/AgCl) for detecting glucose in the diabetic pathophysiological range 0.5–32mM. There was no interference from endogenous electroactive substances and drug metabolites. The developed biosensor was further validated for detecting blood glucose in commercial artificial blood glucose linearity standards in the range 1.4–27.9mM. Therefore, it is ideal for diabetic blood glucose monitoring. The developed bioanalytical procedure for preparation of GOx-bound graphene-functionalized GCEs had high production reproducibility and high storage stability, which is appropriate for the commercial mass production of enzyme-bound electrodes. [Copyright &y& Elsevier]

Abstract: Ordered mesoporous carbon–Au nanoparticles (OMC–Au) nanocomposites were synthesized by a one-step chemical reduction route. Due to the large surface area and high conductivity of OMC, good biocompatibility of OMC and Au nanoparticles, a mediator-free glucose biosensor was fabricated by immobilizing glucose oxidase (GOD) on the OMC–Au nanocomposites modified glassy carbon (GC) electrode. Direct electron transfer between GOD and the electrode was achieved and the electron transfer rate constant (k s ) was calculated to be 5.03s−1. The Michalis–Menten constant value of GOD immobilized on the OMC–Au/GC electrode surface was found to be 0.6mM. The glucose biosensor exhibits a linear range from 0.05 to 20.0mM. This biosensor also shows good reproducibility, excellent stability and the negligible interferences from ascorbic acid and uric acid. [ABSTRACT FROM AUTHOR]

Abstract: NiO hollow nanospheres were synthesized by controlled precipitation of metal ions with urea using carbon microspheres as templates, which were for the first time adopted to construct a novel amperometric glucose biosensor. Glucose oxidase was immobilized on the surface of hollow nanospheres through chitosan-assisted cross-linking technique. Due to the high specific active sites and high electrocatalytic activity of NiO hollow nanospheres, the constructed glucose biosensors exhibited a high sensitivity of 3.43μA/mM. The low detection limit was estimated to be 47μM (S/N=3), and the Michaelis–Menten constant was found to be 7.76mM, indicating the high affinity of enzyme on NiO hollow nanospheres to glucose. These results show that the NiO hollow nanospheres are a promising material to construct enzyme biosensors. [Copyright &y& Elsevier]

Abstract: A membrane was prepared using polyvinyl alcohol (PVA) with low and high degree of polymerization (DOP), acetone, benzoic acid (BA) and was cross-linked by UV treatment. Membrane composition was optimized on the basis of swelling index. Membrane prepared with 12% low DOP and 8% high DOP of PVA, 2% BA, dissolved in buffer containing 20% acetone and cross-linked with UV treatment exhibited lower swelling index. Fourier transform infrared (FTIR) study of the membranes showed appearance of a strong band at ∼2337cm−1 when UV was used for cross-linking in the presence of benzoic acid. Scanning electron microscope (SEM) study revealed that membrane cross-linked with UV treatment was smoother. Glucose oxidase (GOD)–PVA membrane was associated with the dissolved oxygen (DO) probe for biosensor reading. Glucose was detected on the basis of depletion of oxygen, when immobilized GOD oxidizes glucose to gluconolactone. A wide detection range, 0.9–225mg/dl was estimated from the linear range of calibration plot of biosensor reading. Membranes were reused for 32 reactions without significant loss of activity and stored for 30 days (∼90% activity) at 4°C. Membranes were also used with real blood samples. [Copyright &y& Elsevier]

Abstract: A wide size range of SiO2 particles were synthesized and were used as enzyme immobilization carriers to fabricate glucose biosensors. The size of the particles was in the range of 17–520nm. These biosensors could be operated under physiological conditions (0.1M phosphate buffer, pH 7.2). Particle size could affect the performance of SiO2 modified glucose biosensors drastically. The smaller particles had higher performance. The smallest SiO2 modified biosensor could work well in the glucose concentration range of 0.02–10mM with a correlation coefficient of 0.9993. Its sensitivity was 2.08μA/mM and the detection limit was 1.5μM glucose. [Copyright &y& Elsevier]

Abstract: C/Fe nanocomposite (CFN) was synthesized by a procedure similar to an exfoliation/adsorption process to intercalate Fe3+ into graphite oxide (GO) layers and would be reduced in a H2 atmosphere. The results of X-ray diffractometry (XRD) and transimission electron microscopy (TEM) show that the form of CFN is carbon nanotube–Fe nanoparticle composite with α-Fe distributed on the nanotube wall. Paste electrode has been constructed using CFN mixed with paraffin. The electrochemical characteristics of such carbon–Fe nanocomposite paste electrode (CFNPE) has been compared with that of carbon paste electrode (CPE) and evaluated with respect to the electrochemistry of potassium ferricyanide, ascorbic acid and cysteine by cyclic voltammetry. CFNPE can accelerate the electron-transfer to improve the electrochemical reaction reversibility. To fabricate the third-generation glucose biosensor, glucose oxidase (GOD) was immobilized on CFNPE surface with Nafion covered after a pretreatment. Oxygen, ascorbic acid and uric acid have no interference with the glucose detection. The biosensor displays a remarkable sensitivity and stability and the results used in the determination of glucose in the human serum samples are satisfactory. [Copyright &y& Elsevier]

Abstract: The performance of amperometric glucose biosensors based on the dispersion of glucose oxidase (GOx) and copper oxide within a classical carbon (graphite) paste composite is reported in this work. Copper oxide promotes an excellent electrocatalytic activity towards the oxidation and reduction of hydrogen peroxide, allowing a large decrease in the oxidation and reduction overpotentials, as well as an important enhancement of the corresponding currents. Therefore, it is possible to perform the glucose biosensing at low potentials where there is no interference even in large excess of ascorbic acid, uric acid or acetaminophen. The influence of the copper oxide and glucose oxidase content in the paste on the analytical performance of the bioelectrode is discussed. The resulting biosensor shows a fast response, a linear relationship between current and glucose concentration up to 1.35 × 10−2 M (2.43gL−1) and a detection limit of 2.0 × 10−5 M. The effect of the presence of the enzyme in the composite material on the dispersion of the copper oxide particles is also discussed. [Copyright &y& Elsevier]

A glucose biosensor using an enzyme-immobilized eggshell membrane and oxygen electrode for glucose determination has been fabricated. Glucose oxidase was covalently immobilized on an eggshell membrane with glutaraldehyde as a cross-linking agent. The glucose biosensor was fabricated by positioning the enzyme-immobilized eggshell membrane on the surface of a dissolved oxygen sensor. The detection scheme was based on the depletion of dissolved oxygen content upon exposure to glucose solution and the decrease in the oxygen level was monitored and related to the glucose concentration. The effect of glutaraldehyde concentration, pH, phosphate buffer concentration and temperature on the response of the glucose biosensor has been studied in detail. Common matrix interferents such as ethanol, d-fructose, citric acid, sodium benzoate, sucrose and l-ascorbic acid did not give significant interference. The resulting sensor exhibited a fast response (100 s), high sensitivity (8.3409 mg L-1 oxygen depletion/mmol L-1 glucose) and good storage stability (85.2% of its initial sensitivity after 4 months). The linear response is 1.0×10-5 to 1.3×10-3 mol L-1 glucose. The glucose content in real samples such as commercial glucose injection preparations and wines was determined, and the results were comparable to the values obtained from a commercial glucose assay kit based on a spectrophotometric method. [Copyright &y& Elsevier]

A glucose biosensor with enzyme immobilised by sol–gel technology was constructed and evaluated. The glucose biosensor reported is based on encapsulated GOX within a sol–gel glass, prepared with 3-aminopropyltriethoxy silane, 2-(3,4-epoxycyclohexyl)-ethyltrimetoxy silane and HCl. A flow system incorporating the amperometric biosensor constructed was developed for the determination of glucose in the 1×10−4–5×10−3 mol l−1 range with a precision of 1.5%. The results obtained for the analysis of electrolytic solution for iv administration and human serum samples showed good agreement between the proposed method and the reference procedure, with relative error <5%. [Copyright &y& Elsevier]

A highly-sensitive glucose biosensor amenable to ultraminiaturisation was fabricated by immobilization of glucose oxidase (GOX), onto a poly(2,6-diaminopyridine)/multi-walled carbon nanotube/glassy carbon electrode (poly(2,6-DP)/MWCNT/GCE). Cyclic voltammetry was used for both the electrochemical synthesis of poly-(2,6-DP) on the surface of a MWCNT-modified GC electrode, and characterization of the polymers deposited on the GC electrode. The synergistic effect of the high active surface area of both the conducting polymer, i.e., poly-(2,6-DP) and MWCNT gave rise to a remarkable improvement in the electrocatalytic properties of the biosensor. The transfer coefficient ( α ), heterogeneous electron transfer rate constant and Michaelis-Menten constant were calculated to be 0.6, 4 s−1 and 0.22 mM at pH 7.4, respectively. The GOx/poly(2,6-DP)/MWCNT/GC bioelectrode exhibited two linear responses to glucose in the concentration ranging from 0.42 μM to 8.0 mM with a correlation coefficient of 0.95, sensitivity of 52.0 μAmM-1 cm-2, repeatability of 1.6% and long-term stability, which could make it a promising bioelectrode for precise detection of glucose in the biological samples. [ABSTRACT FROM AUTHOR]