Detection Limit For Glucose Research Articles

MHealth Dipstick Analyzer for Monitoring of Pregnancy Complications

Dipstick-based urinalysis is routinely used for the detection of early signs of such pregnancy complications, as preeclampsia and gestational diabetes. Usually it is done in doctor's office using an automatic dipstick analyzer. Here, we present a novel smartphone-based colorimeter and demonstrate its application to the measurements of glucose and protein concentrations in biological samples. The key innovations of our approach was to combine powerful image processing encoded into a mobile phone application with a low cost 3-D printed sample holder that allowed to control lighting conditions and significantly improved sensitivity. Different solutions with protein and glucose concentrations ranging from 0 to 2000 mg/dL were prepared and analyzed using our system. The detection limit for glucose was 40 mg/dL and for protein -6mg/dL The smartphone-based colorimeter always correctly classified the corresponding reagent strip pads, what confirms that it can be used as a low cost alternative for commercial dipstick analyzers.

High-Performance Liquid Chromatography with Refractive Index Detection for the Determination of Inulin in Chicory Roots

ABSTRACTHigh-performance liquid chromatography (HPLC) with refractive index detection was used for the rapid direct determination of inulin with adequate sensitivity, quantitative recoveries, no matrix interferences, and good precision without acidic or enzymatic pretreatment. This method was shown to be reliable by good correlation with acidic hydrolysis of inulin. The new method includes extraction of inulin with hot water in an ultrasonic bath at 70°C for 1 h, followed by direct determination of inulin, fructose, glucose, and sucrose and comparison with acidic hydrolysis of inulin to fructose and glucose by 0.2 mol L−1 hydrochloric acid at 80°C for 1 h. The released total fructose and glucose were also determined by HPLC. The concentration ranges of inulin from 20 samples were from 89.78 to 143.95 g kg−1. For fructose, glucose, and sucrose, the linear ranges were from 1.52 to 5.86, 0.09 to 1.95, and 3.52 to 8.59 g kg−1, respectively. The recoveries were from 80.75 to 110.90%. An internal standard of L-rhamnose was used to quantify free saccharides and total fructose and glucose. The limits of detection for fructose, glucose, sucrose, and inulin were 0.14, 0.20, 0.09, and 0.23 g kg−1, respectively, with average relative standard deviations of 1.05% for repeatability and 3.82% for reproducibility. Chicory root cakes contain many elements, 62.9 to 141.4 g kg−1 crude protein, and 37.6 to 61.2 g kg−1 ash, and are a suitable livestock feed.

Color-tunable luminescent macrofibers based on CdTe QDs-loaded bacterial cellulose nanofibers for pH and glucose sensing

The incorporation of quantum dots into the nanoscale host matrices and assembly of fluorescent building blocks with well-organized structure are critical for the preparation of highly sensitive sensor device. Color-tunable luminescent macrofibers were obtained using wet spinning by assembling CdTe-loaded bacterial cellulose (BC) nanofibers onto one-dimensional structure. BC nanofibers are able to integrate luminescent properties of CdTe quantum dots (QDs) and extend their advantages to fiber-based structures. The luminescent macrofibers with green, yellow and orange fluorescence could be tuned easily by controlling the size of CdTe QDs. This luminescent material with moderate oriented nanofibers was used to detect pH and glucose. The resulting macrofibers exhibited a sigmoidal dependence with pH and high sensitivity to glucose concentrations. The detection limit of glucose is 0.026mM, and the response range and sensitivity of the enzyme-modified macrofibers can be regulated through changing the reaction time which is suitable for different situations. Furthermore, the assay did not require addition of external reagents because all components were deposited onto the fiber substrate. The comparison with commercialized glucose meter indicated that this system is reliable and suitable for practical application. The paper would provide a new platform for the fabrication of fiber-based biosensor based on BC nanofibers, possessing great potential for the development of flexible and wearable biosensing devices.

A TiO2 nanosheet-g-C3N4 composite photoelectrochemical enzyme biosensor excitable by visible irradiation

In this work, g-C3N4 and TiO2 nanosheets were synergistically employed as a novel composite for developing a scaffold of a photoelectrochemical enzyme biosensor. In this way, we have improved the poor visible light excitation of TiO2 and retarded the photo-generated charge recombination on g-C3N4 to achieve an enhanced response at the photoelectrochemical biosensor, compared to that generated by the corresponding biosensors consisting of each individual component. Using glucose oxidase as a model enzyme, the biosensor was demonstrated to show strong visible light activity towards the enzyme mediated glucose oxidation. We have also observed a 350% enhanced photocurrent compared to that at a g-C3N4 based ITO electrode. In addition, the high specific surface area and excellent biocompatibility of TiO2 nanosheets have also positively contributed to the performance of the photoelectrochemical enzyme biosensor with a 0.05–16 mM linear range and a 0.01 mM glucose detection limit.

Detection of hydrogen peroxide and glucose by using Tb2(MoO4)3 nanoplates as peroxidase mimics

Tb2(MoO4)3 nanostructures are demonstrated for the first time to have an intrinsic peroxidase-like activity. Tb2(MoO4)3 nanoplates could efficiently catalyse the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to generate a blue dye (with an absorbance maximum at 652nm) in the presence of H2O2. Based on the highly efficient catalytic of Tb2(MoO4)3 nanoplates, a novel system for optical determination of H2O2 and glucose was successfully established under optimized conditions. The assay had 0.0.08μM and 0.1μM detection limit for H2O2 and glucose, respectively. In our opinion, this enzyme mimetic has a potential to use in other oxidase based assays.

Time-resolved Fluorescent Detection for Glucose Using a Complex of Luminescent Layered Titanates and Enzymes.

Luminescent europium-doped layered titanates (Eu-TiOx) were synthesized and complexed with horseradish peroxidase (HRP) and glucose oxidase (GOx). The emission of a resultant Eu-TiOx/HRP/GOx complex decreased upon the addition of glucose in the presence of guaiacol. The emission decrease was dependent on the concentrations of glucose, and the detection limit for glucose was 3.1 μM. The proposed system would be promising as a new detection method for glucose.

One-step self-assembled epoxide-containing nanodots as an enzyme-immobilized platform for biosensing

3-Glycidoxypropyl trimethoxysilane-containing self-assembled SiOx nanodots (GPS-SANDs) bearing epoxide functional groups were successfully fabricated via a facile one-step heat treatment process. The GPS-SANDs possessed spherical-like particles with an average diameter of 3.1±0.3nm. This material exhibited a broad band, and a multicolor. Glucose oxidase (GOx) enzyme was further immobilized on GPS-SANDs via aminolysis of the epoxide groups to detect glucose using photoluminescence (PL) spectroscopy. The PL intensity changed inversely with the glucose concentration. The glucose detection limit of GOx-immobilized GPS-SANDs was determined to be 100μM. Therefore, GPS-SANDs provide a promising GOx-immobilized platform for the design of optical glucose biosensors with high sensitivity. In addition, this platform may allow for the further development of enzyme biosensing systems through conjugations between GPS-SANDs and a target enzyme.

Native carbon nanodots as a fluorescent probe for assays based on the use of glucose oxidase or horseradish peroxidase

We report on a sensitive and selective fluorescent assay utilizing native carbon dots (CDs) as signal transducers. The optical probes 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) or 3,3′-diaminobenzidine (DAB) were employed as substrates of horseradish peroxidase (HRP). It was found that the corresponding oxidation products (ox-ABTS or ox-DAB) quench the fluorescence of CDs, mainly via photoinduced electron transfer in case of ox-ABTS, and via aggregation and inner filter effect in case of ox-DAB. By coupling with bienzyme (glucose oxidase and HRP)-mediated biocatalytic reactions, the method was applied to the determination of hydrogen peroxide and glucose. In case of ABTS as the substrate of HRP, a wide linear range (0.05 to 100 μM) and a very low detection limit (10 nM) for glucose were attained. The method was applied to the determination of glucose in human serum and the results were found to agree well with data provided by a local hospital.

Capillary electrophoresis method for the simultaneous determination of carbohydrates and proline in honey samples

A capillary electrophoresis method with indirect UV detection for the simultaneous determination of three carbohydrates (fructose, glucose and sucrose) and the amino acid proline in honey samples was developed. This method included the use of a background electrolyte consisting of 10mM sodium benzoate and 1.5mM cetyltrimethylammonium bromide, pH12.4. Under optimal capillary electrophoresis conditions, the separation of the investigated substances was achieved in less than 5min and single dilution of each sample was employed. The detection limits for fructose, glucose and sucrose were 0.58gL−1, 0.67gL−1 and 0.12gL−1 respectively, and 0.72mgL−1 for proline. Precision measurements calculated in terms of %RSD in the range of 0.92 to 5.43%, were obtained. The proposed method was applied to honey samples from Argentina and Sweden and enables the determination of the three carbohydrates and the amino acid proline. The results show that the proposed method is simple, requires short analysis times, low consumption of reagents and sample, minimum waste and that there is no need to perform any sample pre-treatment. This method is a good alternative to carry out the quality control of honey samples. Finally, it is a promising methodology for achieving green chemistry goals.

Highly Sensitive Metabolite Biosensor Based on Organic Electrochemical Transistor Integrated with Microfluidic Channel and Poly(N‐vinyl‐2‐pyrrolidone)‐Capped Platinum Nanoparticles

Organic electrochemical transistors (OECTs) are used as highly sensitive glucose and lactate sensors by modifying the gate electrode with glucose oxidase/lactate oxidase and poly(n‐vinyl‐2‐pyrrolidone)‐capped platinum nanoparticles (Pt NPs). The Pt NPs are deposited by using a two‐step dip coating method without bias instead of the conventional electrodeposition method and followed by an UV‐Ozone post treatment to enhance the catalytic ability of the Pt NPs. The modified OECT sensors have extremely high sensitivity, and can achieve a detection limit of glucose and lactate down to 10−7 and 10−6m, respectively. A polydimethylsiloxane microfluidic channel is successfully integrated with the OECT sensors, which provides a compact chip size of the sensors, a short detection time of around 1 min and extremely low consumption of analyte (30 L). The cross talk between individual sensors in multianalyte sensing devices is also reduced by the dual microfluidic channel structure. Practical applications, such as for detecting glucose in saliva, can therefore be realized, and a prototype of a portable glucose sensor has been successfully created in this study. This portable glucose sensor has excellent potential for real‐time and noninvasive glucose sensing applications.

Platinum nanoparticles decorated dendrite-like gold nanostructure on glassy carbon electrodes for enhancing electrocatalysis performance to glucose oxidation

Platinum nanoparticles decorated dendrite-like gold nanostructure, bimetal composite materials on glassy carbon electrode (Pt/DGNs/GC) for enhancing electrocatalysis to glucose oxidation was designed and successfully fabricated by a facile two-step deposition method without any templates, surfactants, or stabilizers. Dendrite-like gold nanostructure was firstly deposited on the GC electrode via the potentiostatic method, and then platinum nanoparticles were decorated on the surface of gold substrate through chemical reduction deposition. X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDS) were applied to characterize the evolution of morphology and structure of the as-prepared Pt/DGNs/GC. Based on electrochemical measurements such as cyclic voltammetry, linear voltammetry and chronoamperometry, Pt/DGNs/GC exhibited significantly enhanced electrocatalytic performance to glucose oxidation compared those of pure dendrite-like Au nanoparticles in our previous report. Controlling chemical reduction deposition time, the amount of platinum nanoparticles on Au surface could be regulated, which further tuned electrocatalytic properties toward glucose oxidation. The dendrite-like gold surface partially covered by platinum nanoparticles dramatically enhanced the electrocatalytic performance for the oxidation of glucose because of excellent synergetic effects between gold and platinum species and the increased electrochemical active area from Pt nanoparticles loading. The non-enzymatic glucose biosensor based on Pt/DGNs/GC showed a rapid respond time (within 2s), wide linear range (from 0.1mM to 14mM), low detection limit (0.01mM), supernal sensitivity (275.44μAcm−2mM−1, R=0.993), satisfactory reproducibility and good stability for glucose sensing. It was demonstrated that Pt/DGNs/GC could work as promising candidate for factual non-enzymatic glucose detection.

A paper based graphene-nanocauliflower hybrid composite for point of care biosensing

We demonstrate the first report of graphene paper functionalized with fractal platinum nanocauliflower for use in electrochemical biosensing of small molecules (glucose) or detection of pathogenic bacteria (Escherichia coli O157:H7). Raman spectroscopy, scanning electron microscopy and energy dispersive spectroscopy show that graphene oxide-coated nanocellulose was partially reduced by both thermal treatment, and further reduced by chemical treatment (ascorbic acid). Fractal nanoplatinum with cauliflower-like morphology was formed on the reduced graphene oxide paper using pulsed sonoelectrodeposition, producing a conductive paper with an extremely high electroactive surface area (0.29±0.13cm2), confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. The platinum surface was functionalized with either glucose oxidase (via chitosan encapsulation) or a RNA aptamer (via covalent linking) for demonstration as a point of care biosensor. The detection limit for both glucose (0.08±0.02μM) and E. coli O157:H7 (≈4 CFUmL−1) were competitive with, or superior to, previously reported devices in the biosensing literature. The response time (6s for glucose and 12min for E. coli) were also similar to silicon biochip and commercial electrode sensors. The results demonstrate that the nanocellulose-graphene-nanoplatinum material is an excellent paper-based platform for development of electrochemical biosensors targeting small molecules or whole cells for use in point of care biosensing.

CTAB modified dellite: A novel support for enzyme immobilization in bio-based electrochemical detection and its in vitro antimicrobial activity

A novel support material for enzyme immobilization based on cetyltrimethylammonium bromide modified Dellite (CTAB-Del) was successfully synthesized and used to manufacture pyranose oxidase (PyOx) biosensors (CTAB-Del/PyOx). The intercalation of CTAB into Dellite was confirmed by FTIR, XRD and TGA techniques. PyOx was immobilized onto the glassy carbon electrode, via glutaraldehyde crosslinking, by using CTAB-Del as a support. In order to test the analytical performance of CTAB-Del/PyOx biosensors, chronoamperometric measurements were carried out using three electrodes configurations, at a constant potential of −0.7V in working buffer, under stirring, with successive addition of glucose. The linear response for CTAB-Del/PyOx biosensor ranged from 0.01 to 0.50mM with an equation of y=4.42x+0.004 (R2=0.998), and the limit of detection for glucose was calculated to be 0.081μM (S/N=3). In order to confirm its practical use, the CTAB-Del/PyOx biosensor was also applied for glucose measurement in various beverages. In addition, the antimicrobial activities of Del and CTAB-Del were screened in vitro by means of the disc diffusion susceptibility test, selecting a yeast, three different Gram-positive, and five different Gram-negative bacteria. The obtained results showed a moderate antibacterial activity of CTAB-Del against Gram-positive bacteria.

Fast and Effective Turn‐on Paper‐based Phosphorescence Biosensor for Detection of Glucose in Serum

AbstractIn this study, a turn‐on paper‐based optical analytical system with a rapid, sensitive and quantitative response for glucose was developed. The luminescence sensing material, crystalline iridium(III)‐Zn(II) coordination polymers, or Ir‐Zne, was grown electrochemically on stainless steel mesh and then deposited on filter paper. This sensing substrate was subsequently built up under glucose oxidase encapsulated in hydrogel and then immobilized on egg membrane with the layer‐by‐layer method. Once the glucose solution was dropped onto the paper, the oxygen content was depleted simultaneously with a concomitant increase in the phosphorescence of Ir‐Zne. The detection limit for glucose was 0.05 mM. The linear dynamic range for the determination of glucose was 0.05–8.0 mM with a correlation coefficient (R2) of 0.9956 (y=68.11 [glucose]−14.72). The response time was about 0.12 s, and the sample volume was less than 5 μL. The effects of mesh size, buffer concentration, pH, enzyme concentration, temperature, and interference, and the stability of the biosensor, have also been studied in detail. Finally, the biosensor was successfully applied to the determination of glucose in human serum.

Fabrication of a liquid-gated enzyme field effect device for sensitive glucose detection

This study presents fabrication of a liquid-gated enzyme field effect device and its implementation as a glucose biosensor. The device consisted of four electrodes on a glass substrate with a channel functionalized by carboxylated multi-walled carbon nanotubes-polyaniline nanocomposite (MWCNTCOOH/PAn) and glucose oxidase. The resistance of functionalized channel increased with increasing the concentration of glucose when an electric field was applied to the liquid gate. The most effective and stable performance was obtained at the applied electric field of 100 mV. The device resistance, R, exhibited a linear relationship with the logarithm of glucose concentration in the range between 0.005 and 500 mM glucose. The detection limit (S/N = 3) for glucose was about 0.5 μM. Large effective area and good conductivity properties of MWCNTCOOH/PAn nanocomposite were the key features of the fabricated sensitive and stable glucose biosensor.

Raman Analysis of Dilute Aqueous Samples by Localized Evaporation of Submicroliter Droplets on the Tips of Superhydrophobic Copper Wires.

Raman analysis of dilute aqueous solutions is normally prevented by their low signal levels. A very general method to increase the concentration to detectable levels is to evaporate droplets of the sample to dryness, creating solid deposits which are then Raman probed. Here, superhydrophobic (SHP) wires with hydrophilic tips have been used as supports for drying droplets, which have the advantage that the residue is automatically deposited at the tip. The SHP wires were readily prepared in minutes using electroless galvanic deposition of Ag onto copper wires followed by modification with a polyfluorothiol (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluoro-1-decanethiol, HDFT). Cutting the coated wires with a scalpel revealed hydrophilic tips which could support droplets whose maximum size was determined by the wire diameter. Typically, 230 μm wires were used to support 0.6 μL droplets. Evaporation of dilute melamine droplets gave solid deposits which could be observed by scanning electron microscopy (SEM) and Raman spectroscopy. The limit of detection for melamine using a two stage evaporation procedure was 1 × 10(-6) mol dm(-3). The physical appearance of dried droplets of sucrose and glucose showed that the samples retained significant amounts of water, even under high vacuum. Nonetheless, the Raman detection limits of sucrose and glucose were 5 × 10(-4) and 2.5 × 10(-3) mol dm(-3), respectively, which is similar to the sensitivity reported for surface-enhanced Raman spectroscopy (SERS) detection of glucose. It was also possible to quantify the two sugars in mixtures at concentrations which were similar to those found in human blood through multivariate analysis.

An Enzyme Free Potentiometric Detection of Reducing Sugars Based on a Poly(3-hydroxyphenylboronic acid-co-phenol) Molecularly Imprinted Polymer Modified Electrode

An enzyme free potentiometric sensor for reducing sugars (glucose and fructose) based on molecularly imprinted polymer (MIP) modified on glassy carbon electrode was systematically investigated. It was expected to work like a solid ion selective electrode (ISE) where the specific carrier are the imprinted sites. The polymer for the selective recognition of glucose and fructose were synthesized by coelectropolymerizing the 3-hydroxyphenyl boronic acid and phenol with reducing sugar (glucose or fructose) complex. The phenol could not only provide more hydroxyl but also promote the electron transfer because of its benzene ring structure and oxygen. The principle of reducing sugars detection at the MIP modified glassy carbon electrode (MIP/GCE) was to form a covalent binding which was reversible when changing the binding conditions and had a quick response to the electrochemical potential of the fabricated sensor. The imprinted polymer films covered on the electrode surface could improve the sensitivity of the sensor response remarkably. Under the optimal experimental conditions, the potential change and the concentration of glucose and fructose were linearly related from 0.75 to 18 mM. The detection limit of glucose and fructose was 0.23 mM and 0.35 mM, respectively. In addition, we had successfully evaluated the applicability of the sensitive sensor according to detect reducing sugars in practical samples.

Enhanced peroxidase-like activity of MoS2/graphene oxide hybrid with light irradiation for glucose detection

Construction of novel enzyme-free mimetic is very important in improving the sensitivity of biosensor. Here, an intrinsic peroxidase-like activity of MoS2 and graphene oxide (MoS2/GO) hybrid is demonstrated and the hybrid is also used to detect glucose with high sensitivity. Firstly, the peroxidase-like activity of hydrid is compared with that of two components alone, the mixture of two components and horseradish peroxidase. The results show that the hydrid has highest catalytic activity and the Michaelis constant of this hybrid is 4.35 times lower and the maximal reaction velocity is 3.34 times higher than those of horseradish peroxidase, respectively. Electrochemical technologies are used to investigate the enhancing mechanism. The results show that the excellently catalytic performance could be attributed to the fast electron transfer on the surface of MoS2/GO and the synergistic interaction of two components. Secondly, the effect of visible light and near-infrared light on the peroxidase-like activity of hybrid is also investigated. The results show that the limit of detection for H2O2 can be reduced from 10nM to 2.5nM with visible light. Thirdly, the hybrid is further used to detect glucose in serum with and without light. The results show that the hybrid has high selectivity and sensitivity for glucose detection in serum and the limit of detection for glucose is reduced from 0.83μM to 65nM with visible light. Therefore, the hybrid may have a potential application in glucose detection in serum with high sensitivity and selectivity.

Polystyrene@Au@prussian blue nanocomposites with enzyme-like activity and their application in glucose detection

Abstract Prussian blue (PB) and gold modified polystyrene (PS) nanocomposites (PS@Au@PB) were synthesized and characterized by TEM, SEM, FTIR, UV–vis and EDS. The formation mechanism of PB induced by gold nanoparticles on PS nanospheres was proposed. The peroxidase-like and catalase-like activities of the synthesized nanocomposites were investigated. Peroxidase-like activity was found to follow Michaelis–Menten kinetics. The calculated kinetic parameters indicated that the PS@Au@PB nanocomposites possess strong affinity with the substrates and high catalytic activity. A sensitive method for glucose detection was developed using glucose oxidase (GO x ) and PS@Au@PB nanocomposites. The detection limit for glucose was determined to be as low as 3.9 μM and the linear range was from 15.6 to 250.0 μM. It suggests that PS@Au@PB nanocomposites can serve as a useful reagent in some biological detections.

Highly sensitive colorimetric detection of glucose in a serum based on DNA-embeded Au@Ag core–shell nanoparticles

Glucose is a key energy substance in diverse biology and closely related to the life activities of the organism. To develop a simple and sensitive method for glucose detection is extremely urgent but still remains a key challenge. Herein, we report a colorimetric glucose sensor in a homogeneous system based on DNA-embedded core–shell Au@Ag nanoparticles. In this assay, a glucose substrate was first catalytically oxidized by glucose oxidase to produce H2O2 which would further oxidize and gradually etch the outer silver shell of Au@Ag nanoparticles. Afterwards, the solution color changed from yellow to red and the surface plasmon resonance (SPR) band of Au@Ag nanoparticles declined and red-shifted from 430 to 516 nm. Compared with previous silver-based glucose colorimetric detection strategies, the distinctive SPR band change is superior to the color variation, which is critical to the high sensitivity of this assay. Benefiting from the outstanding optical property, robust stability and well-dispersion of the core–shell Au@AgNPs hybrid, this colorimetric assay obtained a detection limit of glucose as low as 10 nM, which is at least a 10-fold improvement over other AgNPs-based procedures. Moreover, this optical biosensor was successfully employed to the determination of glucose in fetal bovine serum.