Detection Limit For Glucose Research Articles

Electrodeposition and electrocatalytic properties of Pt/Ni–Co nanowires for non-enzymatic glucose detection

A nanowire arrays system consisting of an ordered configuration of Pt, Ni and Co was constructed in single-bath solution through pulse electrodeposition. This structure was evaluated as a potential amperometric non-enzymatic sensor to detect glucose in alkaline solution. We observed a strong and fast amperometric response at low applied potential of 0.4V vs. SCE over linear ranges of 0–0.2mM and 0.2–8mM glucose with sensitivities of 1125 and 333μAmM−1cm−2, respectively. We also observed a low detection limit for glucose of 1μM. Correlation of the electronic and geometric modifications with the electrochemical performance characteristics enhanced catalytic activity of the electrode by applying the Ni and Co components to Pt nanowires structure. The electrode showed good analytical performance and high selectivity with no interference from other oxidable species, demonstrating its promise for developing an effective glucose sensor.

A new approach for paper-based analytical devices with electrochemical detection based on graphite pencil electrodes

Abstract The present work describes for the first time the coupling of graphite pencil electrodes with paper-based analytical devices (μPADs) for glucose biosensing. Electrochemical measurement for μPADs using a two-electrode system was also developed. This dual-electrode configuration on paper provides electrochemical responses similar to those recorded by conventional electrochemical systems (three electrode systems). A wax printing process was used to define hydrophilic circular microzones by inserting hydrophobic patterns on paper. The microzones were employed one for filtration, one for an enzymatic reaction and one for electrochemical detection. By adding 4-aminophenylboronic acid as redox mediator and glucose oxidase to the reaction microzone, it was possible to reach low limits of detection for glucose with graphite pencil electrodes without modifying the electrode. The limit of detection of the proposed μPAD was found to be 0.38 μmol L −1 for glucose. Low sample consumption (40 μL) and fast analysis time (less than 5 min) combined with low cost electrodes and paper-based analytical platforms are attractive properties of the proposed μPAD with electrochemical detection. Artificial blood serum samples containing glucose were analyzed with the proposed device as proof of concept.

Glassy carbon electrode modified with glucose oxidase–graphene–nano-copper composite film for glucose sensing

We report on the modification of a glassy carbon electrode with graphene and Cu nanoparticles (Cunano), and how this electrode can serve as a platform for the construction of a novel electrochemical biosensor for the study of the direct electrochemistry of glucose oxidase and then application for glucose detection. To obtain the biosensor, the glucose oxidase was immobilized on the surface of the graphene and Cunano modified electrode, and this process was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. A sensitive biosensor with a detection limit of 5μM glucose was achieved, which was thought to result from a combination of beneficial effects including the biocompatibility and large surface area of the Cunano, the high conductivity of the graphene, the synergistic effects of composite film, and the increased quantity of glucose oxidase adsorbed on the electrode surface. The voltammetric responses were proportional to the concentration of glucose in the range from 0.05mM to 12mM. The biosensor was sensitive and stable.

Chemiluminescence flow biosensor for glucose using Mg-Al carbonate layered double hydroxides as catalysts and buffer solutions

In this work, serving as supports in immobilizing luminol reagent, catalysts of luminol chemiluminescence (CL), and buffer solutions for the CL reaction, Mg-Al-CO3 layered double hydroxides (LDHs) were found to trigger luminol CL in weak acid solutions (pH 5.8). The silica sol–gel with glucose oxidase and horseradish peroxidase was immobilized in the first half of the inside surface of a clear quartz tube, and luminol-hybrid Mg-Al-CO3 LDHs were packed in the second half. Therefore, a novel CL flow-through biosensor for glucose was constructed in weak acid solutions. The CL intensity was linear with glucose concentration in the range of 0.005–1.0mM, and the detection limit for glucose (S/N=3) was 0.1μM. The proposed biosensor exhibited excellent stability, high reproducibility and high selectivity for the determination of glucose and has been successfully applied to determine glucose in human plasma samples with satisfactory results. The success of this work has broken the bottleneck of the pH incompatibility between luminol CL and enzyme activity.

Application of Polymer Quantum Dot-Enzyme Hybrids in the Biosensor Development and Test Paper Fabrication

Both glutathione capped CdTe quantum dots (QDs) and enzymes were encapsulated with poly(diallyldimethylammonium chloride) (PDDA) via electrostatic attraction to form hybrid films. The obtained PDDA QD-enzyme hybrids feature both high fluorescence and biorecognition. In the obtained hybrid materials, the fluorescence emission of the QDs was stable for at least 3 months, and the structure and activity of the enzyme was also well maintained as the Michaelis constant of tyrosinase was determined to be 0.90 mmol/L, which is just 2 times higher than that of free enzyme. This hybrid material was then utilized as a platform for the development of biosensors based on the quenching effects of the enzymatic products on the emission of the QDs with a kind of phenol (catechol) and glucose as example analytes. The detection limits of catechol and glucose were 1.0 × 10(-5) and 5.0 × 10(-6) mol/L, respectively. Moreover, this hybrid material was applied to the fabrication of test paper for these two analytes. The test paper was very stable with respect to the fluorescence of the QDs and the activity of the enzyme maintained for at least 1 month.

Controllable Deposition of a Platinum Nanoparticle Ensemble on a Polyaniline/Graphene Hybrid as a Novel Electrode Material for Electrochemical Sensing

We demonstrate for the first time an interfacial polymerization method for the synthesis of high-quality polyaniline-modified graphene nanosheets (PANI/GNs), which represents a novel type of graphene/polymer heterostructure. The interfacial polymerization at a liquid-liquid interface allows PANI to grow uniformly on the surface of the GNs. An ultra-high loading of Pt nanoparticles was then controllably deposited on the surface of the PANI/GNs to form a Pt/PANI/GNs hybrid. The obtained composites were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The Pt/PANI/GNs hybrid shows excellent electrocatalytic activity toward methanol oxidation and oxygen reduction. H(2)O(2) and glucose were used as two representative analytes to demonstrate the sensing performance of a Pt/PANI/GNs-modified electrode. It is found that this sensing element shows high sensitivity and a low detection limit for H(2)O(2) and glucose. The results demonstrate that the Pt/PANI/GNs hybrid may be an attractive and advanced electrode material with potential applications in the construction of electrochemical sensors and biosensors.

Glucose sensing in human epidermis using mid-infrared photoacoustic detection

No reliable non-invasive glucose monitoring devices are currently available. We implemented a mid-infrared (MIR) photoacoustic (PA) setup to track glucose in vitro in deep epidermal layers, which represents a significant step towards non-invasive in vivo glucose measurements using MIR light. An external-cavity quantum-cascade laser (1010–1095 cm−1) and a PA cell of only 78 mm3 volume were employed to monitor glucose in epidermal skin. Skin samples are characterized by a high water content. Such samples investigated with an open-ended PA cell lead to varying conditions in the PA chamber (i.e., change of light absorption or relative humidity) and cause unstable signals. To circumvent variations in relative humidity and possible water condensation, the PA chamber was constantly ventilated by a 10 sccm N2 flow. By bringing the epidermal skin samples in contact with aqueous glucose solutions with different concentrations (i.e., 0.1–10 g/dl), the glucose concentration in the skin sample was varied through passive diffusion. The achieved detection limit for glucose in epidermal skin is 100 mg/dl (SNR=1). Although this lies within the human physiological range (30–500 mg/dl) further improvements are necessary to non-invasively monitor glucose levels of diabetes patients. Furthermore spectra of epidermal tissue with and without glucose content have been recorded with the tunable quantum-cascade laser, indicating that epidermal constituents do not impair glucose detection.

Characteristics of third-generation glucose biosensors based on Corynascus thermophilus cellobiose dehydrogenase immobilized on commercially available screen-printed electrodes working under physiological conditions

In this article, we describe a third-generation amperometric glucose biosensor working under physiological conditions. This glucose biosensor consists of a recently discovered cellobiose dehydrogenase from the ascomycete Corynascus thermophilus (CtCDH) immobilized on different commercially available screen-printed electrodes made of carbon (SPCEs), carboxyl-functionalized single-walled carbon nanotubes (SPCE–SWCNTs), or multiwalled carbon nanotubes (SPCE–MWCNTs) by simple physical adsorption or a combination of adsorption followed by cross-linking using poly(ethyleneglycol) (400) diglycidyl ether (PEGDGE) or glutaraldehyde (GA). The CtCDH-based third-generation glucose biosensor has a linear range between 0.025 and 30mM and a detection limit of 10μM glucose. Biosensors based on SWCNTs showed a higher sensitivity and catalytic response than the ones functionalized with MWCNTs and the SPCEs. A drastic increase in response was observed for all three electrodes when the adsorbed enzyme was cross-linked with PEGDGE or GA. The operational stability of the biosensor was tested for 7h by repeated injections of 50mM glucose, and only a slight decrease in the electrochemical response was found. The selectivity of the CtCDH-based biosensor was tested on other potentially interfering carbohydrates such as mannose, galactose, sucrose, and fucose that might be present in blood. No significant analytical response from any of these compounds was observed.

Development of quantitative enzymatic method and its validation for the assay of glucose in human serum

ObjectiveTo develop a simple, rapid, sensitive and affordable assay method for the determination of glucose in blood samples using a novel approach. Design and methodsA spectrophotometric method for glucose quantification in human serum samples based on self-coupling of activated 2,5-dimethoxyaniline (DMA) in the presence of peroxidase (POD)/glucose oxidase (GOD) and H2O2 is described. H2O2 generated in situ by catalytic reaction between GOD and glucose, activates DMA in the presence of POD to form a green-colored product, which has a strong absorption at λmax=740nm at room temperature (30°C) in a 100mmol/L acetate/acetic acid buffer of pH 4.2. ResultsThe linearity ranges for the quantification of glucose by rate and one-time detection method are 0.017–0.740 and 0.017–0.478mmol/L, respectively. Within-day and day-to-day precision were 0.98–1.4% (n=10) and 1.33–2.89% (n=15), respectively. Glucose recoveries ranged from 96.6 to 102%, indicating minimal interference by commonly present interferants in serum samples. Accuracy results were between 90 and 102%. The detection and quantification limits of glucose were 2.376 and 7.923μmol/L, respectively. The proposed method has good correlation coefficient of 0.999 with the enzymatic kit method. ConclusionsThis is a rapid and convenient method to determine serum glucose using simple spectrophotometer with excellent recovery and minimal interference by interferants in serum samples with low detection limit. Therefore, this method can be considered for adoption by the clinical diagnostic laboratories.

Determination of Sugars in β-Amylase Hydrolysates by High Performance Liquid Chromatography

Abstract. The chromatographic conditions for the separation of glucose, maltose and maltotriose on a ZORBAX Eclipse XDB-C18 column (4 um, 4.6×250mm) by use of a 2414 differential refractometer detector were determined. The square of the correlation coefficient of glucose, sucrose, maltose and maltotriose was 0.9973, 0.9981, 0.9977 and 0.9987, respectively. When the ratio of signal and noise was 3, the detection limit of glucose, sucrose, maltose and maltotriose was 0.3, 0.3, 0.20, 0.20 mg/mL the β-amylase hydrolysates consisted mainly of maltose, and maltotriose next, glucose only in trace amount, and no sucrose. The RSD of glucose, maltose and maltotriose was 2.08%, 2.41% and 2.61%, respectively. And the recovery of glucose, maltose and maltotriose was 101.3%, 98.4% and 93.5%. It was credible to separate sugars from hydrolysates. The method is important for improving the inducible enzymes activity.

Enhanced glucose detection using enzyme-immobilized ZnO/ZnS core/sheath nanowires

The role of ZnS shell was explored in the enhancement of fluorescent glucose sensing of enzyme-conjugated ZnO/ZnS core/sheath nanowires. High-density ZnO nanowires were vertically grown on Si substrates by carbothermal method and they were coated with almost monolayer ZnS nanocrystals to obtain ZnO/ZnS core/sheath nanowire structures. The surface of ZnO nanowires and ZnO/ZnS nanowires was modified with mercapto-acetic acid (MAA) and MAA-terminated nanowires were activated by esterification of n-hydroxysulfo-succinimide (Sulfo-NHS). Glucose oxidase (GOx), an enzyme, could be covalently combined with NHS-terminated nanowires to form ZnO–MAA–GOx and ZnO/ZnS–MAA–GOx bioconjugates. Due to the surface passivation of ZnO by ZnS sheath, ZnO/ZnS–MAA–GOx showed increased band-edge emission compared to ZnO–MAA–GOx. Glucose detection characteristics were investigated monitoring the change in PL intensity (∼380 nm) and the results were compared to each other. Both samples showed almost linear increase in PL intensity with glucose concentration from ∼3.51 to ∼24.1 mM. However, ZnO/ZnS–MAA–GOx showed about two-times higher sensitivity to glucose and lower detection limit (0.14 mM) compared to ZnO–MAA–GOx (0.23 mM). This is most possibly due to more effective electron injection into the conduction band of ZnO nanowires, arising from the passivation of surface defects and surface dangling bonds of ZnO by ZnS sheath formation. Also, both ZnO–MAA–GOx and ZnO/ZnS–MAA–GOx showed fast glucose response time of <10 and <5 s, respectively.

Glucose detection with surface plasmon resonance spectroscopy and molecularly imprinted hydrogel coatings

Molecularly imprinted hydrogel membranes were developed and evaluated for detection of small analytes via surface plasmon resonance spectroscopy. Imprinting of glucose phosphate barium salt into a poly(allylamine hydrochloride) network covalently bound to gold surfaces yielded a selective sensor for glucose. Optimization of relative amounts of chemicals used for preparation of the hydrogel was performed to obtain highest sensitivity. Addition of gold nanoparticles into the hydrogel matrix significantly amplified its response and sensitivity due to the impact of gold nanoparticles on the refractive index of the sensing layer. Evaluation of its selectivity showed that the sensor displayed preferential recognition to glucose compared to structurally related sugars in addition to being unaffected by phosphate as well as compounds containing amine groups, like creatinine. The detection limit of glucose in deionized water was calculated to be 0.02mg/mL. The developed sensor was finally exposed to human urine spiked with glucose illustrating the coating's ability to re-bind the analyte in complex matrices. While the working concentration range in water was determined to be suitable for glucose monitoring in diabetic individuals at physiological levels, the detection in urine was determined to be 0.12mg/mL. The decreased performance in urine provided an initial perspective on the difficulties associated with measurements in complex media.

Colorimetric detection of glucose and an assay for acetylcholinesterase with amine-terminated polydiacetylene vesicles

The colorimetric response of amine-terminated polydiacetylene (PDA) vesicles was initially demonstrated by varying the pH of the solution. Convenient colorimetric methods to detect glucose and acetylcholinesterase (AChE) activity were successfully established using amine-terminated PDA vesicles by taking advantage of the following features: (1) the amine-terminated PDA vesicles undergo a colorimetric transition as the pH of the solution changes; (2) glucose can be oxidized to gluconic acid in the presence of glucose oxidase; and (3) AChE catalyzes the hydrolysis of acetylcholine to acetic acid. The visual detection of glucose levels and AChE activity showed good selectivity and acceptable sensitivity. The detection limit of glucose was ∼2.5 μmol/L and the level of AChE activity was assayed as low as 10.0 mU/mL. Moreover, the amine-terminated PDA vesicles can be used for screening the activity of inhibitors against AChE.

Aligned SWCNT-copper oxide array as a nonenzymatic electrochemical probe of glucose

Copper oxide nanoparticles (COs) were electrochemically deposited on horizontally aligned single-walled carbon nanotube arrays (COs-aSWCNT) on SiO 2/Si wafer, where X-ray photoelectron spectroscopy shows that compositions of COs are Cu 2O and CuO with a ratio of 2 to 1. The as-prepared COs-aSWCNT electrode exhibited synergistic electrocatalytic activity on the oxidation of glucose in alkaline media with a rapid response time of less than 2 s and a high sensitivity of 16.2 μA μM − 1 . This new sensor has two useful linear regions of glucose concentration and has an experimental detection limit of 20 nM. In the presence of physiological level ascorbic acid (0.1 mM), the experimental detection limit of glucose increases to 50 nM with a sensitivity of 1.31 μA μM − 1 .

Electrochemical biosensor for glucose detection using zinc oxide nanotetrapods

Wurtzite structural zinc oxide (ZnO) nanotetrapods were synthesised by a thermal evaporation method. These ZnO nanotetrapods were used for the construction of an electrochemical biosensor for detecting glucose. In the biosensor, the ZnO nanotetrapods acted as supporting materials for glucose oxidase (GOx) enzyme loading because of the large surface area to volume ratio. The results indicated that the biosensor with the structure of [polystyrene mixed with ZnO powder/GOx/ZnO nanotetrapod powder/Au electrode] exhibited the lowest glucose detection limit (∼0.5 mM). These results demonstrate that zinc oxide nanostructures have potential applications in biosensors.

Fabrication of Bienzymatic Glucose Biosensor Based on Novel Gold Nanoparticles‐Bacteria Cellulose Nanofibers Nanocomposite

AbstractAn exploration of gold nanoparticles–bacterial cellulose nanofibers (Au‐BC) nanocomposite as a platform for amperometric determination of glucose is presented. Two enzymes, glucose oxidase (GOx) and horseradish peroxidase (HRP) were immobilized in Au‐BC nanocomposite modified glassy carbon electrode at the same time. A sensitive and fast amperometric response to glucose was observed in the presence of electron mediator (HQ). Both of GOx and HRP kept their biocatalytic activities very well in Au‐BC nanocomposite. The detection limit for glucose in optimized conditions was as low as 2.3 µM with a linear range from 10 µM to 400 µM. The biosensor was successfully applied to the determination of glucose in human blood samples.

Enzymatically synthesized polyaniline layer for extension of linear detection region of amperometric glucose biosensor

In this article a new method for fabrication of enzymatic electrodes suitable for design of amperometric glucose biosensor and/or anode of biofuel cell powered by glucose is presented. Glucose oxidase (GOx) E.C. 1.1.3.4. from Penicillium vitale was immobilized on the carbon rod electrode by cross-linking it with glutaraldehyde (GOx-electrode). Catalytic activity of immobilized GOx was exploited for polymerisation of aniline by taking a high concentration of hydrogen peroxide produced during the catalytic action of immobilized GOx and locally lowered pH due to the formation of gluconic acid; it created optimal conditions for the polymerisation of aniline. The GOx layer was self-encapsulated within formed polyaniline (PANI) matrix (GOx/PANI-electrode). Properties of the GOx/PANI-electrode have been studied and results were compared with GOx-electrode. The results show that the upper detection limit of glucose using GOx-electrode was dramatically changed by the formation of PANI layer. An increase in the upper detection limit, optimal pH region for operation and stability of GOx based electrode modified by PANI was detected when comparing that of an unmodified GOx-electrode.

Determination of Glucose on Free Enzyme-based Poly(dimethylsiloxane) Microchip

Abstract Microfluidic enzyme-based reactor could be used to detect biomolecules with high sensitivity and selectivity. Based on the electrophoretic-mediated microanalysis (EMMA) method, a novel free enzyme-based microchip was developed to detect glucose. Online catalysis reaction of glucose by glucose oxidase was carried out on the chip. The product H 2 O 2 was detected using amperometric method. The working electrode, single carbon fibre cylindrical electrode, was held at a constant potential of +1.4 V versus Ag/AgCl electrode. The results indicated that the peak current had a good linear relationship with glucose concentration in the range of 0.1–20 mM ( R = 0.997) with good reproducibility (RSD = 2.02%, n = 10). The detection limit of glucose was 19.8 μM ( S/N = 3). This free enzyme-based reactor was easy to fabricate and operate, which showed great potential application in bioanalysis.

Amperometric glucose biosensor based on gold nanorods and chitosan comodified Au electrode

Au nanorods were prepared by a seeding growth approach and used in fabricating the nanorod-enhancing glucose biosensor. The high affinity of chitosan for Au nanorods associated with its amino groups resulted in the formation of a layer of Au nanorods on the surface of Au electrode. It served as an intermediator to retain high efficient and stable immobilization of the enzyme. The performance of biosensors was investigated by cyclic voltammetry (CV), in the presence of artificial redox mediator, ferrocenecarboxaldehyde. The biosensor had a fast response to glucose, and the response time was less than 10 s. The results indicated that the gold nanorods could enhance the current response to glucose. The detection limits of glucose can reach 10 mM, and the Michaelis-Menten constant K app m is 13.62 mM.

Nano-yarn carbon nanotube fiber based enzymatic glucose biosensor

A novel brush-like electrode based on carbon nanotube (CNT) nano-yarn fiber has beendesigned for electrochemical biosensor applications and its efficacy as an enzymaticglucose biosensor demonstrated. The CNT nano-yarn fiber was spun directlyfrom a chemical-vapor-deposition (CVD) gas flow reaction using a mixture ofethanol and acetone as the carbon source and an iron nano-catalyst. The fiber, 28 µm in diameter, was made of bundles of double walled CNTs (DWNTs) concentricallycompacted into multiple layers forming a nano-porous network structure. Cyclicvoltammetry study revealed a superior electrocatalytic activity for CNT fiber compared tothe traditional Pt–Ir coil electrode. The electrode end tip of the CNT fiber wasfreeze-fractured to obtain a unique brush-like nano-structure resembling a scale-downelectrical ‘flex’, where glucose oxidase (GOx) enzyme was immobilized using glutaraldehydecrosslinking in the presence of bovine serum albumin (BSA). An outer epoxy-polyurethane(EPU) layer was used as semi-permeable membrane. The sensor function was tested againsta standard reference electrode. The sensitivities, linear detection range and linearityfor detecting glucose for the miniature CNT fiber electrode were better thanthat reported for a Pt–Ir coil electrode. Thermal annealing of the CNT fiber at250 °C for 30 min prior to fabrication of the sensor resulted in a 7.5 fold increase in glucosesensitivity. The as-spun CNT fiber based glucose biosensor was shown to bestable for up to 70 days. In addition, gold coating of the electrode connectingend of the CNT fiber resulted in extending the glucose detection limit to 25 µM. To conclude, superior efficiency of CNT fiber for glucose biosensing was demonstratedcompared to a traditional Pt–Ir sensor.