Electron-transfer mediator for a NAD-glucose dehydrogenase-based glucose sensor.

Science.gov (United States)

Kim, Dong-Min; Kim, Min-yeong; Reddy, Sanapalli S; Cho, Jaegeol; Cho, Chul-ho; Jung, Suntae; Shim, Yoon-Bo

2013-12-03

A new electron-transfer mediator, 5-[2,5-di (thiophen-2-yl)-1H-pyrrol-1-yl]-1,10-phenanthroline iron(III) chloride (FePhenTPy) oriented to the nicotinamide adenine dinucleotide-dependent-glucose dehydrogenase (NAD-GDH) system was synthesized through a Paal-Knorr condensation reaction. The structure of the mediator was confirmed by Fourier-transform infrared spectroscopy, proton and carbon nucler magnetic resonance spectroscopy, and mass spectroscopy, and its electron-transfer characteristic for a glucose sensor was investigated using voltammetry and impedance spectroscopy. A disposable amperometric glucose sensor with NAD-GDH was constructed with FePhenTPy as an electron-transfer mediator on a screen printed carbon electrode (SPCE) and its performance was evaluated, where the addition of reduces graphene oxide (RGO) to the mediator showed the enhanced sensor performance. The experimental parameters to affect the analytical performance and the stability of the proposed glucose sensor were optimized, and the sensor exhibited a dynamic range between 30 mg/dL and 600 mg/dL with the detection limit of 12.02 ± 0.6 mg/dL. In the real sample experiments, the interference effects by acetaminophen, ascorbic acid, dopamine, uric acid, caffeine, and other monosaccharides (fructose, lactose, mannose, and xylose) were completely avoided through coating the sensor surface with the Nafion film containing lead(IV) acetate. The reliability of proposed glucose sensor was evaluated by the determination of glucose in artificial blood and human whole blood samples.

A contact lens with integrated telecommunication circuit and sensors for wireless and continuous tear glucose monitoring

International Nuclear Information System (INIS)

Yao, H; Liao, Y; Lingley, A R; Afanasiev, A; Lähdesmäki, I; Otis, B P; Parviz, B A

2012-01-01

We present an integrated functional contact lens, composed of a differential glucose sensor module, metal interconnects, sensor read-out circuit, antenna and telecommunication circuit, to monitor tear glucose levels wirelessly, continuously and non-invasively. The electrochemical differential sensor module is based on immobilization of activated and de-activated glucose oxidase. We characterized the sensor on a model polymer eye and determined that it showed good repeatability, molecular interference rejection and linearity in the range of 0–2 mM glucose, covering normal tear glucose concentrations (0.1–0.6 mM). We also report the temperature, ageing and protein-fouling sensitivity of the sensor. We report the design and implementation of a low-power (3 µW) sensor read-out and telecommunication circuit to deliver wireless power and transmit data for the sensor module. Using this small chip (0.36 mm 2 ), we produced an integrated contact lens with sensors and demonstrated wireless operation of the system and glucose read-out over the distance of several centimeters. (paper)

Novel fungal FAD glucose dehydrogenase derived from Aspergillus niger for glucose enzyme sensor strips.

Science.gov (United States)

Sode, Koji; Loew, Noya; Ohnishi, Yosuke; Tsuruta, Hayato; Mori, Kazushige; Kojima, Katsuhiro; Tsugawa, Wakako; LaBelle, Jeffrey T; Klonoff, David C

2017-01-15

In this study, a novel fungus FAD dependent glucose dehydrogenase, derived from Aspergillus niger (AnGDH), was characterized. This enzyme's potential for the use as the enzyme for blood glucose monitor enzyme sensor strips was evaluated, especially by investigating the effect of the presence of xylose during glucose measurements. The substrate specificity of AnGDH towards glucose was investigated, and only xylose was found as a competing substrate. The specific catalytic efficiency for xylose compared to glucose was 1.8%. The specific activity of AnGDH for xylose at 5mM concentration compared to glucose was 3.5%. No other sugars were used as substrate by this enzyme. The superior substrate specificity of AnGDH was also demonstrated in the performance of enzyme sensor strips. The impact of spiking xylose in a sample with physiological glucose concentrations on the sensor signals was investigated, and it was found that enzyme sensor strips using AnGDH were not affected at all by 5mM (75mg/dL) xylose. This is the first report of an enzyme sensor strip using a fungus derived FADGDH, which did not show any positive bias at a therapeutic level xylose concentration on the signal for a glucose sample. This clearly indicates the superiority of AnGDH over other conventionally used fungi derived FADGDHs in the application for SMBG sensor strips. The negligible activity of AnGDH towards xylose was also explained on the basis of a 3D structural model, which was compared to the 3D structures of A. flavus derived FADGDH and of two glucose oxidases. Copyright © 2016 Elsevier B.V. All rights reserved.

Human Subcutaneous Tissue Response to Glucose Sensors: Macrophages Accumulation Impact on Sensor Accuracy.

Science.gov (United States)

Rigla, Mercedes; Pons, Belén; Rebasa, Pere; Luna, Alexis; Pozo, Francisco Javier; Caixàs, Assumpta; Villaplana, Maria; Subías, David; Bella, Maria Rosa; Combalia, Neus

2018-04-01

Subcutaneous (s.c.) glucose sensors have become a key component in type 1 diabetes management. However, their usability is limited by the impact of foreign body response (FBR) on their duration, reliability, and accuracy. Our study gives the first description of human acute and subacute s.c. response to glucose sensors, showing the changes observed in the sensor surface, the inflammatory cells involved in the FBR and their relationship with sensor performance. Twelve obese patients (seven type 2 diabetes) underwent two abdominal biopsies comprising the surrounding area where they had worn two glucose sensors: the first one inserted 7 days before and the second one 24 h before biopsy procedure. Samples were processed and studied to describe tissue changes by two independent pathologists (blind regarding sensor duration). Macrophages quantification was studied by immunohistochemistry methods in the area surrounding the sensor (CD68, CD163). Sensor surface changes were studied by scanning electron microscopy. Seven-day continuous glucose monitoring records were considered inaccurate when mean absolute relative difference was higher than 10%. Pathologists were able to correctly classify all the biopsies regarding sensor duration. Acute response (24 h) was characterized by the presence of neutrophils while macrophages were the main cell involved in subacute inflammation. The number of macrophages around the insertion hole was higher for less accurate sensors compared with those performing more accurately (32.6 ± 14 vs. 10.6 ± 1 cells/0.01 mm 2 ; P sensor-tissue interface is related with decrease in accuracy of the glucose measure.

Novel glucose fiber sensor combining ThFBG with GOD

Science.gov (United States)

Li, Mengmeng; Zhou, Ciming; Fan, Dian; Ou, Yiwen

2016-10-01

We propose a novel glucose fiber optic sensor combining a thinned cladding fiber Bragg grating (ThFBG) with glucose oxidase (GOD). By immobilizing GOD on the surface of a ThFBG, the fabricated sensor can obtain a high specificity to glucose. Because of the evanescent field, the sensor is very sensitive to the ambient refractive index change arising from the catalytic reaction between glucose and GOD. A four-level fiber model was simulated and verified the precision of the sensing principle. Two methods, glutaraldehyde crosslinking method (GCM) and 3-aminopropyl triethoxysilane covalent coupling method (ATCCM), were experimentally utilized to immobilize GOD. And sensor fabricated with the method ATCCM shows a measurement range of 0-0.82 mg/mL which is better than the sensor fabricated with the method GCM with measurement range of 0-0.67 mg/mL under the same condition. By using ATCCM to immobilize GOD with different concentrations, three sensors were fabricated and used for glucose measurement by monitoring the Bragg wavelength (λb) shifts, the results indicate a good linear relationship between wavelength shift and glucose concentration within a specific range, and the measurement range increases as GOD concentration increases. The highest sensitivity of sensor reaches up to 0.0549 nm/(mg.mL-1). The proposed sensor has distinct advantages in sensing structure, cost and specificity.

A Lab-on-a-Chip-Based Non-Invasive Optical Sensor for Measuring Glucose in Saliva

Directory of Open Access Journals (Sweden)

Dong Geon Jung

2017-11-01

Full Text Available A lab-on-a-chip (LOC-based non-invasive optical sensor for measuring glucose in saliva was fabricated. Existing glucose sensors utilizing blood require acquisition of a blood sample by pricking the finger, which is painful and inconvenient. To overcome these limitations, we propose a non-invasive glucose sensor with LOC, micro-electro-mechanical system and optical measurement technology. The proposed sensor for measuring glucose in saliva involves pretreatment, mixing, and measurement on a single tiny chip. Saliva containing glucose and glucose oxidase for glucose oxidation are injected through Inlets 1 and 2, respectively. Next, H2O2 is produced by the reaction between glucose and glucose oxidase in the pretreatment part. The saliva and generated H2O2 are mixed with a colorizing agent injected through Inlet 3 during the mixing part and the absorbance of the colorized mixture is measured in the measurement part. The absorbance of light increases as a function of glucose concentration at a wavelength of 630 nm. To measure the absorbance of the colorized saliva, a light-emitting diode with a wavelength of 630 nm and a photodiode were used during the measurement part. As a result, the measured output current of the photodiode decreased as glucose concentration in the saliva increased.

SNF3 as high affinity glucose sensor and its function in supporting the viability of Candida glabrata under glucose-limited environment

Directory of Open Access Journals (Sweden)

Tzu Shan eNg

2015-12-01

Full Text Available Candida glabrata is an emerging human fungal pathogen that has efficacious nutrient sensing and responsiveness ability. It can be seen through its ability to thrive in diverse range of nutrient limited-human anatomical sites. Therefore, nutrient sensing particularly glucose sensing is thought to be crucial in contributing to the development and fitness of the pathogen. This study aimed to elucidate the role of SNF3 (Sucrose Non Fermenting 3 as a glucose sensor and its possible role in contributing to the fitness and survivability of C. glabrata in glucose-limited environment. The SNF3 knockout strain was constructed and subjected to different glucose concentrations to evaluate its growth, biofilm formation, amphotericin B susceptibility, ex vivo survivability and effects on the transcriptional profiling of the sugar receptor repressor (SRR pathway-related genes. The SNF3Δ strain showed a retarded growth in low glucose environments (0.01% and 0.1% in both fermentation and respiration-preferred conditions but grew well in high glucose concentration environments (1% and 2%. It was also found to be more susceptible to amphotericin B in low glucose environment (0.1% and macrophage engulfment but showed no difference in the biofilm formation capability. The deletion of SNF3 also resulted in the down-regulation of about half of hexose transporters genes (4 out of 9. Overall, the deletion of SNF3 causes significant reduction in the ability of C. glabrata to sense limited surrounding glucose and consequently disrupts its competency to transport and perform the uptake of this critical nutrient. This study highlighted the role of SNF3 as a high affinity glucose sensor and its role in aiding the survivability of C. glabrata particularly in glucose limited environment.

Self-assembly of palladium nanoparticles on functional TiO{sub 2} nanotubes for a nonenzymatic glucose sensor

Energy Technology Data Exchange (ETDEWEB)

Chen, Xianlan [School of Science, Honghe University, Mengzi, Yunnan 661100 (China); College of Chemistry, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Li, Gang; Zhang, Guowei [School of Science, Honghe University, Mengzi, Yunnan 661100 (China); Hou, Keyu [College of Chemistry, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Pan, Haibo, E-mail: hbpan@fzu.edu.cn [College of Chemistry, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Du, Min [Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China)

2016-05-01

Polydiallyldimethylammonium chloride, PDDA, was used as a stabilizer and linker for functionalized TiO{sub 2} nanotubes (TiO{sub 2} NTs). Self-assembled process with palladium nanoparticles (NPs) was successfully synthesized and used for the oxidation of glucose on glassy carbon electrodes. Based on the voltammetric and amperometric results, Pd NPs efficiently catalyzed the oxidation of glucose at − 0.05 V in the presence of 0.1 M NaCl and showed excellent resistance toward interference poisoning from such interfering species as ascorbic acid, uric acid and urea. To further increase sensitivity, the Pd NPs-PDDA-TiO{sub 2} NTs/GCE was electrochemically treated with H{sub 2}SO{sub 4} and NaOH, the glucose oxidation current was magnified 2.5 times than that before pretreatments due to greatly enhancing the electron transport property of the sensor based on the increased defect sites and surface oxide species. In view of the physiological level of glucose, the wide linear concentration range of glucose (4 × 10{sup −7}–8 × 10{sup −4} M) with a detection limit of 8 × 10{sup −8} M (S/N = 3) was obviously good enough for clinical application. - Highlights: • PDDA was used as a stabilizer and linker for functionalized TiO{sub 2} nanotubes. • Self-assembled process with palladium nanoparticles was synthesized. • After treated both H{sub 2}SO{sub 4} and NaOH, the glucose response was magnified to 2.5 times. • The wide linear concentration range of glucose was obtained with a limit of 8 × 10{sup −8} M.

Continuous glucose monitoring in subcutaneous tissue using factory-calibrated sensors: a pilot study.

Science.gov (United States)

Hoss, Udo; Jeddi, Iman; Schulz, Mark; Budiman, Erwin; Bhogal, Claire; McGarraugh, Geoffrey

2010-08-01

Commercial continuous subcutaneous glucose monitors require in vivo calibration using capillary blood glucose tests. Feasibility of factory calibration, i.e., sensor batch characterization in vitro with no further need for in vivo calibration, requires a predictable and stable in vivo sensor sensitivity and limited inter- and intra-subject variation of the ratio of interstitial to blood glucose concentration. Twelve volunteers wore two FreeStyle Navigator (Abbott Diabetes Care, Alameda, CA) continuous glucose monitoring systems for 5 days in parallel for two consecutive sensor wears (four sensors per subject, 48 sensors total). Sensors from a prototype sensor lot with a low variability in glucose sensitivity were used for the study. Median sensor sensitivity values based on capillary blood glucose were calculated per sensor and compared for inter- and intra-subject variation. Mean absolute relative difference (MARD) calculation and error grid analysis were performed using a single calibration factor for all sensors to simulate factory calibration and compared to standard fingerstick calibration. Sensor sensitivity variation in vitro was 4.6%, which increased to 8.3% in vivo (P glucose monitoring is feasible with similar accuracy to standard fingerstick calibration. Additional data are required to confirm this result in subjects with diabetes.

Nonenzymetic glucose sensing using carbon functionalized carbon doped ZnO nanorod arrays

Science.gov (United States)

Chakraborty, Pinak; Majumder, Tanmoy; Dhar, Saurab; Mondal, Suvra Prakash

2018-04-01

Fabrication of highly sensitive, long stability and low cost glucose sensors are attractive for biomedical applications and food industries. Most of the commercial glucose sensors are based on enzymatic detection which suffers from problems underlying in enzyme activities. Development of high sensitive, enzyme free sensors is a great challenge for next generation glucose sensing applications. In our study Zinc oxide nanorod sensing electrodes have been grown using low cost hydrothermal route and their nonenzymatic glucose sensing properties have been demonstrated with carbon functionalized, carbon doped ZnO nanorods (C-ZnO NRs) in neutral medium (0.1M PBS, pH 7.4) using cyclic voltammetry and amperometry measurements. The C-ZnO NRs electrodes demonstrated glucose sensitivity˜ 13.66 µAmM-1cm-2 in the concentration range 0.7 - 14 mM.

Fabrication of Amperometric Glucose Sensor Using Glucose Oxidase-Cellulose Nanofiber Aqueous Solution.

Science.gov (United States)

Yasuzawa, Mikito; Omura, Yuya; Hiura, Kentaro; Li, Jiang; Fuchiwaki, Yusuke; Tanaka, Masato

2015-01-01

Cellulose nanofiber aqueous solution, which remained virtually transparent for more than one week, was prepared by using the clear upper layer of diluted cellulose nanofiber solution produced by wet jet milling. Glucose oxidase (GOx) was easily dissolved in this solution and GOx-immobilized electrode was easily fabricated by simple repetitious drops of GOx-cellulose solution on the surface of a platinum-iridium electrode. Glucose sensor properties of the obtained electrodes were examined in phosphate buffer solution of pH 7.4 at 40°C. The obtained electrode provided a glucose sensor response with significantly high response speed and good linear relationship between glucose concentration and response current. After an initial decrease of response sensitivity for a few days, relatively constant sensitivity was obtained for about 20 days. Nevertheless, the influence of electroactive compounds such as ascorbic acid, uric acid and acetoaminophen were not negletable.

A Highly Sensitive Electrochemical Glucose Sensor By Nickel-Epoxy Electrode With Non-Enzymatic Sensor

Directory of Open Access Journals (Sweden)

Riyanto Riyanto

2016-03-01

Full Text Available The preparation of new sensor for glucose was based on the fact that glucose can be determined by non-enzymatic glucose oxidase. The Ni metals (99.98% purity, 0.5 mm thick, Aldrich Chemical Company was used to prepare Ni-Epoxy electrode. The Ni-epoxy electrodes were prepared in square cut of 1 cm and 1 mm by length and wide respectively. The Ni metal electrodes were connected to silver wire with silver conducting paint prior covered with epoxy gum. The prepared of nickel-epoxy modified electrode showed outstanding electro catalytic activity toward the oxidation of glucose in alkaline solution. The result from this research are correlation of determination using Nickel-Epoxyelectrode for electroanalysis of glucose in NaOH was R2 = 0.9984. LOQ, LOD and recovery of the Nickel-Epoxy electrode towards glucose were found to be 4.4 μM, 1.48 μM and 98.19%, respectively. The Nickel-Epoxy wire based electrochemical glucose sensor demonstrates good sensitivity, wide linear range, outstanding detection limit, attractive selectivity, good reproducibility, high stability as well as prominent feasibility use of non-enzymatic sensor for monitoring glucose in human urine owing to its advantages of low cost, simple preparation and excellent properties for glucose detection.

Glucose Sensor Using U-Shaped Optical Fiber Probe with Gold Nanoparticles and Glucose Oxidase.

Science.gov (United States)

Chen, Kuan-Chieh; Li, Yu-Le; Wu, Chao-Wei; Chiang, Chia-Chin

2018-04-16

In this study, we proposed a U-shaped optical fiber probe fabricated using a flame heating method. The probe was packaged in glass tube to reduce human factors during experimental testing of the probe as a glucose sensor. The U-shaped fiber probe was found to have high sensitivity in detecting the very small molecule. When the sensor was dipped in solutions with different refractive indexes, its wavelength or transmission loss changed. We used electrostatic self-assembly to bond gold nanoparticles and glucose oxidase (GOD) onto the sensor’s surface. The results over five cycles of the experiment showed that, as the glucose concentration increased, the refractive index of the sensor decreased and its spectrum wavelength shifted. The best wavelength sensitivity was 2.899 nm/%, and the linearity was 0.9771. The best transmission loss sensitivity was 5.101 dB/%, and the linearity was 0.9734. Therefore, the proposed U-shaped optical fiber probe with gold nanoparticles and GOD has good potential for use as a blood sugar sensor in the future.

Highly Selective and Sensitive Self-Powered Glucose Sensor Based on Capacitor Circuit.

Science.gov (United States)

Slaughter, Gymama; Kulkarni, Tanmay

2017-05-03

Enzymatic glucose biosensors are being developed to incorporate nanoscale materials with the biological recognition elements to assist in the rapid and sensitive detection of glucose. Here we present a highly sensitive and selective glucose sensor based on capacitor circuit that is capable of selectively sensing glucose while simultaneously powering a small microelectronic device. Multi-walled carbon nanotubes (MWCNTs) is chemically modified with pyrroloquinoline quinone glucose dehydrogenase (PQQ-GDH) and bilirubin oxidase (BOD) at anode and cathode, respectively, in the biofuel cell arrangement. The input voltage (as low as 0.25 V) from the biofuel cell is converted to a stepped-up power and charged to the capacitor to the voltage of 1.8 V. The frequency of the charge/discharge cycle of the capacitor corresponded to the oxidation of glucose. The biofuel cell structure-based glucose sensor synergizes the advantages of both the glucose biosensor and biofuel cell. In addition, this glucose sensor favored a very high selectivity towards glucose in the presence of competing and non-competing analytes. It exhibited unprecedented sensitivity of 37.66 Hz/mM.cm 2 and a linear range of 1 to 20 mM. This innovative self-powered glucose sensor opens new doors for implementation of biofuel cells and capacitor circuits for medical diagnosis and powering therapeutic devices.

77 FR 30016 - Clinical Study Design and Performance of Hospital Glucose Sensors

Science.gov (United States)

2012-05-21

...] Clinical Study Design and Performance of Hospital Glucose Sensors AGENCY: Food and Drug Administration, HHS... Sensors.'' The purpose of this public meeting is to discuss clinical study design considerations and performance metrics for innovative glucose sensors intended to be used in hospital point of care settings...

A highly sensitive electrochemical glucose sensor structuring with nickel hydroxide and enzyme glucose oxidase

International Nuclear Information System (INIS)

Mathew, Manjusha; Sandhyarani, N.

2013-01-01

Graphical abstract: A combination of Ni 2+ /Ni 3+ redox couple and glucose oxidase has successfully been exploited for the realization of a highly sensitive glucose sensor for the first time. -- Highlights: • A multilayered glucose biosensor with enhanced sensitivity was fabricated. • Combination of Ni 2+ /Ni 3+ redox couple and glucose oxidase has been exploited for the first time. • Exhibits a lower detection limit of 100 nM with a high sensitivity of 16,840 μA mM −1 cm −2 . • The surface shows a low Michaelis–Menten constant value of 2.4 μM. • Detailed mechanism of sensing was proposed and justified. -- Abstract: A multilayered glucose biosensor with enhanced electron transport was fabricated via the sequential electrodeposition of chitosan gold nanocomposite (CGNC) and nickel hydroxide (Ni(OH) 2 ) on a bare gold electrode and subsequent immobilization of glucose oxidase. A thin film of Ni(OH) 2 deposited on CGNC modified gold electrode serves as an electrochemical redox probe as well as a matrix for the immobilization of glucose oxidase retaining its activity. Electron transport property of CGNC has been exploited to enhance the electron transport between the analyte and electrode. Electrochemical characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. Under optimal conditions the biosensor exhibits a linear range from 1 μM to 100 μM with a limit of detection (lod) down to 100 nM. The sensor shows a low Michaelis-Menten constant value of 2.4 μM indicates the high affinity of enzyme to the analyte points to the retained activity of enzyme after immobilization. The present glucose sensor with the high selectivity, sensitivity and stability is promising for practical clinical applications

POF based glucose sensor incorporating grating wavelength filters

DEFF Research Database (Denmark)

Hassan, Hafeez Ul; Aasmul, Søren; Bang, Ole

2014-01-01

AND RESEARCH IN POLYMER OPTICAL DEVICES; TRIPOD. Within the domain of TRIPOD, research is conducted on "Plastic Optical Fiber based Glucose Sensors Incorporating Grating Wavelength Filters". Research will be focused to optimized fiber tips for better coupling efficiency, reducing the response time of sensor...

Amperometric glucose sensor based on enhanced catalytic reduction of oxygen using glucose oxidase adsorbed onto core-shell Fe3O4-silica-Au magnetic nanoparticles

International Nuclear Information System (INIS)

Wang Aijun; Li Yongfang; Li Zhonghua; Feng Jiuju; Sun Yanli; Chen Jianrong

2012-01-01

Monodisperse Fe 3 O 4 magnetic nanoparticles (NPs) were prepared under facile solvothermal conditions and successively functionalized with silica and Au to form core/shell Fe 3 O 4 -silica-Au NPs. Furthermore, the samples were used as matrix to construct a glucose sensor based on glucose oxidase (GOD). The immobilized GOD retained its bioactivity with high protein load of 3.92 × 10 −9 mol·cm −2 , and exhibited a surface-controlled quasi-reversible redox reaction, with a fast heterogeneous electron transfer rate of 7.98 ± 0.6 s −1 . The glucose biosensor showed a broad linear range up to 3.97 mM with high sensitivity of 62.45 μA·mM −1 cm −2 and fast response (less than 5 s). - Graphical abstract: Core-shell structured Fe 3 O 4 -silica-Au nanoparticles were prepared and used as matrix to construct an amperometric glucose sensor based on glucose oxidase, which showed broad linear range, high sensitivity, and fast response. Highlights: ► Synthesis of monodispersed Fe 3 O 4 nanoparticles. ► Fabrication of core/shell Fe 3 O 4 -silica-Au nanoparticles. ► Construction of a novel glucose sensor with wide linear range, high sensitivity and fast response.

Toward an injectable continuous osmotic glucose sensor.

Science.gov (United States)

Johannessen, Erik; Krushinitskaya, Olga; Sokolov, Andrey; Philipp, Häfliger; Hoogerwerf, Arno; Hinderling, Christian; Kautio, Kari; Lenkkeri, Jaakko; Strömmer, Esko; Kondratyev, Vasily; Tønnessen, Tor Inge; Mollnes, Tom Eirik; Jakobsen, Henrik; Zimmer, Even; Akselsen, Bengt

2010-07-01

The growing pandemic of diabetes mellitus places a stringent social and economic burden on the society. A tight glycemic control circumvents the detrimental effects, but the prerogative is the development of new more effective tools capable of longterm tracking of blood glucose (BG) in vivo. Such discontinuous sensor technologies will benefit from an unprecedented marked potential as well as reducing the current life expectancy gap of eight years as part of a therapeutic regime. A sensor technology based on osmotic pressure incorporates a reversible competitive affinity assay performing glucose-specific recognition. An absolute change in particles generates a pressure that is proportional to the glucose concentration. An integrated pressure transducer and components developed from the silicon micro- and nanofabrication industry translate this pressure into BG data. An in vitro model based on a 3.6 x 8.7 mm large pill-shaped implant is equipped with a nanoporous membrane holding 4-6 nm large pores. The affinity assay offers a dynamic range of 36-720 mg/dl with a resolution of +/-16 mg/dl. An integrated 1 x 1 mm(2) large control chip samples the sensor signals for data processing and transmission back to the reader at a total power consumption of 76 microW. Current studies have demonstrated the design, layout, and performance of a prototype osmotic sensor in vitro using an affinity assay solution for up to four weeks. The small physical size conforms to an injectable device, forming the basis of a conceptual monitor that offers a tight glycemic control of BG. 2010 Diabetes Technology Society.

Vertically grown zinc oxide nanorods functionalized with ferric oxide for in vivo and non-enzymatic glucose detection

Science.gov (United States)

Marie, Mohammed; Manoharan, Anishkumar; Kuchuk, Andrian; Ang, Simon; Manasreh, M. O.

2018-03-01

An enzyme-free glucose sensor based on vertically grown zinc oxide nanorods (NRs) functionalized with ferric oxide (Fe2O3) is investigated. The well-aligned and high density ZnO NRs were synthesized on an FTO/glass substrate by a sol-gel and hydrothermal growth method. A dip-coating technique was utilized to modify the surface of the as-grown ZnO NRs with Fe2O3. The immobilized surface was coated with a layer of nafion membrane. The fabricated glucose sensor was characterized amperometrically at room temperature using three electrodes stationed in the phosphate buffer solution, where ZnO NRs/Fe2O3/nafion membrane was the sensing or working electrode, and platinum plate and silver/silver chloride were used as the counter and reference electrodes, respectively. The proposed non-enzymatic and modified glucose sensor exhibited a high sensitivity in the order of 0.052 μA cm-2 (mg/dL)-1, a lower detection limit of around 0.95 mmol L-1, a sharp and fast response time of ˜1 s, and a linear response to changes in glucose concentrations from 100-400 mg dL-1. The linear amperometric response of the sensor covers the physiological and clinical interest of glucose levels for diabetic patients. The device continues to function accurately after multiple measurements with a good reproducibility. The proposed glucose sensor is expected to be used clinically for in vivo monitoring of glucose.

A Robust, Enzyme-Free Glucose Sensor Based on Lysine-Assisted CuO Nanostructures

Directory of Open Access Journals (Sweden)

Qurrat-ul-Ain Baloach

2016-11-01

Full Text Available The production of a nanomaterial with enhanced and desirable electrocatalytic properties is of prime importance, and the commercialization of devices containing these materials is a challenging task. In this study, unique cupric oxide (CuO nanostructures were synthesized using lysine as a soft template for the evolution of morphology via a rapid and boiled hydrothermal method. The morphology and structure of the synthesized CuO nanomaterial were characterized using scanning electron microscopy (SEM and X-ray diffraction (XRD, respectively. The prepared CuO nanostructures showed high potential for use in the electrocatalytic oxidation of glucose in an alkaline medium. The proposed enzyme-free glucose sensor demonstrated a robust response to glucose with a wide linear range and high sensitivity, selectivity, stability, and reproducibility. To explore its practical feasibility, the glucose content of serum samples was successfully determined using the enzyme-free sensor. An analytical recovery method was used to measure the actual glucose from the serum samples, and the results were satisfactory. Moreover, the presented glucose sensor has high chemical stability and can be reused for repetitive measurements. This study introduces an enzyme-free glucose sensor as an alternative tool for clinical glucose quantification.

Polymer Optical Fiber Compound Parabolic Concentrator fiber tip based glucose sensor: In-Vitro Testing

DEFF Research Database (Denmark)

Hassan, Hafeez Ul; Janting, Jakob; Aasmul, Soren

2016-01-01

We present in-vitro sensing of glucose using a newly developed efficient optical fiber glucose sensor based on a Compound Parabolic Concentrator (CPC) tipped polymer optical fiber (POF). A batch of 9 CPC tipped POF sensors with a 35 mm fiber length is shown to have an enhanced fluorescence pickup...... efficiency with an average increment factor of 1.7 as compared to standard POF sensors with a plane cut fiber tip. Invitro measurements for two glucose concentrations (40 and 400 mg/dL) confirm that the CPC tipped sensors efficiently can detect both glucose concentrations. it sets the footnote at the bottom...

Micro-Electromechanical Affinity Sensor for the Monitoring of Glucose in Bioprocess Media

Directory of Open Access Journals (Sweden)

Lorenz Theuer

2017-06-01

Full Text Available An affinity-viscometry-based micro-sensor probe for continuous glucose monitoring was investigated with respect to its suitability for bioprocesses. The sensor operates with glucose and dextran competing as binding partner for concanavalin A, while the viscosity of the assay scales with glucose concentration. Changes in viscosity are determined with a micro-electromechanical system (MEMS in the measurement cavity of the sensor probe. The study aimed to elucidate the interactions between the assay and a typical phosphate buffered bacterial cultivation medium. It turned out that contact with the medium resulted in a significant long-lasting drift of the assay’s viscosity at zero glucose concentration. Adding glucose to the medium lowers the drift by a factor of eight. The cglc values measured off-line with the glucose sensor for monitoring of a bacterial cultivation were similar to the measurements with an enzymatic assay with a difference of less than ±0.15 g·L−1. We propose that lectin agglomeration, the electro-viscous effect, and constitutional changes of concanavalin A due to exchanges of the incorporated metal ions may account for the observed viscosity increase. The study has demonstrated the potential of the MEMS sensor to determine sensitive viscosity changes within very small sample volumes, which could be of interest for various biotechnological applications.

Biostability of an implantable glucose sensor chip

Science.gov (United States)

Fröhlich, M.; Birkholz, M.; Ehwald, K. E.; Kulse, P.; Fursenko, O.; Katzer, J.

2012-12-01

Surface materials of an implantable microelectronic chip intended for medical applications were evaluated with respect to their long-term stability in bio-environments. The sensor chip shall apply in a glucose monitor by operating as a microviscosimeter according to the principle of affinity viscosimetry. A monolithic integration of a microelectromechanical system (MEMS) into the sensor chip was successfully performed in a combined 0.25 μm CMOS/BiCMOS technology. In order to study material durability and biostability of the surfaces, sensor chips were exposed to various in vitro and in vivo tests. Corrosional damage of SiON, SiO2 and TiN surfaces was investigated by optical microscopy, ellipsometry and AFM. The results served for optimizing the Back-end-of-Line (BEoL) stack, from which the MEMS was prepared. Corrosion of metal lines could significantly be reduced by improving the topmost passivation layer. The experiments revealed no visible damage of the actuator or other functionally important MEMS elements. Sensor chips were also exposed to human body fluid for three month by implantation into the abdomen of a volunteer. Only small effects were observed for layer thickness and Ra roughness after explantation. In particular, TiN as used for the actuator beam showed no degradation by biocorrosion. The highest degradation rate of about 50 nm per month was revealed for the SiON passivation layer. These results suggest that the sensor chip may safely operate in subcutaneous tissue for a period of several months.

Biostability of an implantable glucose sensor chip

International Nuclear Information System (INIS)

Fröhlich, M; Ehwald, K E; Kulse, P; Fursenko, O; Katzer, J; Birkholz, M

2012-01-01

Surface materials of an implantable microelectronic chip intended for medical applications were evaluated with respect to their long-term stability in bio-environments. The sensor chip shall apply in a glucose monitor by operating as a microviscosimeter according to the principle of affinity viscosimetry. A monolithic integration of a microelectromechanical system (MEMS) into the sensor chip was successfully performed in a combined 0.25 μm CMOS/BiCMOS technology. In order to study material durability and biostability of the surfaces, sensor chips were exposed to various in vitro and in vivo tests. Corrosional damage of SiON, SiO 2 and TiN surfaces was investigated by optical microscopy, ellipsometry and AFM. The results served for optimizing the Back-end-of-Line (BEoL) stack, from which the MEMS was prepared. Corrosion of metal lines could significantly be reduced by improving the topmost passivation layer. The experiments revealed no visible damage of the actuator or other functionally important MEMS elements. Sensor chips were also exposed to human body fluid for three month by implantation into the abdomen of a volunteer. Only small effects were observed for layer thickness and R a roughness after explantation. In particular, TiN as used for the actuator beam showed no degradation by biocorrosion. The highest degradation rate of about 50 nm per month was revealed for the SiON passivation layer. These results suggest that the sensor chip may safely operate in subcutaneous tissue for a period of several months.

Development of a nonlinear model for the prediction of response times of glucose affinity sensors using concanavalin A and dextran and the development of a differential osmotic glucose affinity sensor

Science.gov (United States)

Reis, Louis G.

With the increasing prevalence of diabetes in the United States and worldwide, blood glucose monitoring must be accurate and reliable. Current enzymatic sensors have numerous disadvantages that make them unreliable and unfavorable among patients. Recent research in glucose affinity sensors correct some of the problems that enzymatic sensors experience. Dextran and concanavalin A are two of the more common components used in glucose affinity sensors. When these sensors were first explored, a model was derived to predict the response time of a glucose affinity sensor using concanavalin A and dextran. However, the model assumed the system was linear and fell short of calculating times representative of the response times determined through experimental tests with the sensors. In this work, a new model that uses the Stokes-Einstein Equation to demonstrate the nonlinear behavior of the glucose affinity assay was developed to predict the response times of similar glucose affinity sensors. In addition to the device tested by the original linear model, additional devices were identified and tested with the proposed model. The nonlinear model was designed to accommodate the many different variations between systems. The proposed model was able to accurately calculate response times for sensors using the concanavalin A-dextran affinity assay with respect to the experimentally reported times by the independent research groups. Parameter studies using the nonlinear model were able to identify possible setbacks that could compromise the response of thesystem. Specifically, the model showed that the improper use of asymmetrical membranes could increase the response time by as little as 20% or more as the device is miniaturized. The model also demonstrated that systems using the concanavalin Adextran assay would experience higher response times in the hypoglycemic range. This work attempted to replicate and improve an osmotic glucose affinity sensor. The system was designed to

Hydrogel-based electrochemical sensor for non-invasive and continuous glucose monitoring

Science.gov (United States)

Park, Habeen; Lee, Ji-Young; Kim, Dong-Chul; Koh, Younggook; Cha, Junhoe

2017-07-01

Monitoring blood glucose level of diabetic patients is crucial in diabetes care from life threating complications. Selfmonitoring blood glucose (SMBG) that involves finger prick to draw blood samples into the measurement system is a widely-used method of routine measurement of blood glucose levels to date. SMBG includes, however, unavoidable pain problems resulting from the repetitive measurements. We hereby present a hydrogel-based electrochemical (H-EC) sensor to monitor the glucose level, non-invasively. Glucose oxidase (GOx) was immobilized in the disc-type hydroxyethyl methacrylate (HEMA) based hydrogel and kept intact in the hydrogel. Fast electron transfer mediated by Prussian blue (PB, hexacyanoferrate) generated efficient signal amplifications to facilitate the detection of the extracted glucose from the interstitial fluid. The linear response and the selectivity against glucose of the H-EC sensor were validated by chronoamperometry. For the practical use, the outcomes from the correlation of the extracted glucose concentration and the blood glucose value by on-body extraction, as well as the validation of the hydrogel-based electrochemical (H-EC) device, were applied to the on-body glucose monitoring.

Modeling the relative impact of capsular tissue effects on implanted glucose sensor time lag and signal attenuation.

Science.gov (United States)

Novak, Matthew T; Yuan, Fan; Reichert, William M

2010-10-01

Little is known mechanistically about why implanted glucose sensors lag behind blood glucose levels in both the time to peak sensor response and the magnitude of peak sensor response. A mathematical model of glucose transport from capillaries through surrounding tissue to the sensor surface was constructed to address how different aspects of the tissue affect glucose transport to an implanted sensor. Physiologically relevant values of capsule diffusion coefficient, capsule porosity, cellular glucose consumption, capsule thickness, and subcutaneous vessel density were used as inputs to create simulated sensor traces that mimic experimental instances of time lag and concentration attenuation relative to a given blood glucose profile. Using logarithmic sensitivity analysis, each parameter was analyzed to study the effect of these variables on both lag and attenuation. Results identify capsule thickness as the strongest determinant of sensor time lag, while subcutaneous vessel density and capsule porosity had the largest effects on attenuation of glucose that reaches the sensor surface. These findings provide mechanistic insight for the rational design of sensor modifications that may alleviate the deleterious consequences of tissue effects on implanted sensor performance.

Highly sensitive glucose sensor based on monodisperse palladium nickel/activated carbon nanocomposites.

Science.gov (United States)

Koskun, Yağmur; Şavk, Aysun; Şen, Betül; Şen, Fatih

2018-06-20

Glucose enzyme biosensors have been used for a variety of applications such as medical diagnosis, bioprocess engineering, beverage industry and environmental scanning etc. and there is still a growing interest in glucose sensors. For this purpose, addressed herein, as a novel glucose sensor, highly sensitive activated carbon (AC) decorated monodisperse nickel and palladium alloy nanocomposites modified glassy carbon electrode (Ni-Pd@AC/GCE NCs) have been synthesized by in-situ reduction technique. Raman Spectroscopy (RS), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), cyclic voltammetry (CV) and chronoamperometry (CA) were used for the characterization of the prepared non-enzymatic glucose sensor. The characteristic sensor properties of the Ni-Pd@AC/GCE electrode were compared with Ni-Pd NCs/GCE, Ni@AC/GCE and Pd@AC/GCE and the results demonstrate that the AC is very effective in the enhancement of the electrocatalytic properties of sensor. In addition, the Ni-Pd@AC/GCE nanocomposites showed a very low detection limit of 0.014 μM, a wide linear range of 0.01 mM-1 mM and a very high sensitivity of 90 mA mM -1  cm -2 . Furthermore, the recommended sensor offer the various advantageous such as facile preparation, fast response time, high selectivity and sensitivity. Lastly, monodisperse Ni-Pd@AC/GCE was utilized to detect glucose in real sample species. Copyright © 2018 Elsevier B.V. All rights reserved.

An Integrated Glucose Sensor with an All-Solid-State Sodium Ion-Selective Electrode for a Minimally Invasive Glucose Monitoring System

Directory of Open Access Journals (Sweden)

Junko Kojima

2015-06-01

Full Text Available We developed a minimally invasive glucose monitoring system that uses a microneedle to permeate the skin surface and a small hydrogel to accumulate interstitial fluid glucose. The measurement of glucose and sodium ion levels in the hydrogel is required for estimating glucose levels in blood; therefore, we developed a small, enzyme-fixed glucose sensor with a high-selectivity, all-solid-state, sodium ion-selective electrode (ISE integrated into its design. The glucose sensor immobilized glucose oxidase showed a good correlation between the glucose levels in the hydrogels and the reference glucose levels (r > 0.99, and exhibited a good precision (coefficient of variation = 2.9%, 0.6 mg/dL. In the design of the sodium ISEs, we used the insertion material Na0.33MnO2 as the inner contact layer and DD16C5 exhibiting high Na+/K+ selectivity as the ionophore. The developed sodium ISE exhibited high selectivity (\\( \\log \\,k^{pot}_{Na,K} = -2.8\\ and good potential stability. The sodium ISE could measure 0.4 mM (10−3.4 M sodium ion levels in the hydrogels containing 268 mM (10−0.57 M KCl. The small integrated sensor (ϕ < 10 mm detected glucose and sodium ions in hydrogels simultaneously within 1 min, and it exhibited sufficient performance for use as a minimally invasive glucose monitoring system.

Skin-Attachable, Stretchable Electrochemical Sweat Sensor for Glucose and pH Detection.

Science.gov (United States)

Oh, Seung Yun; Hong, Soo Yeong; Jeong, Yu Ra; Yun, Junyeong; Park, Heun; Jin, Sang Woo; Lee, Geumbee; Oh, Ju Hyun; Lee, Hanchan; Lee, Sang-Soo; Ha, Jeong Sook

2018-04-25

As part of increased efforts to develop wearable healthcare devices for monitoring and managing physiological and metabolic information, stretchable electrochemical sweat sensors have been investigated. In this study, we report on the fabrication of a stretchable and skin-attachable electrochemical sensor for detecting glucose and pH in sweat. A patterned stretchable electrode was fabricated via layer-by-layer deposition of carbon nanotubes (CNTs) on top of patterned Au nanosheets (AuNS) prepared by filtration onto stretchable substrate. For the detection of glucose and pH, CoWO 4 /CNT and polyaniline/CNT nanocomposites were coated onto the CNT-AuNS electrodes, respectively. A reference electrode was prepared via chlorination of silver nanowires. Encapsulation of the stretchable sensor with sticky silbione led to a skin-attachable sweat sensor. Our sensor showed high performance with sensitivities of 10.89 μA mM -1 cm -2 and 71.44 mV pH -1 for glucose and pH, respectively, with mechanical stability up to 30% stretching and air stability for 10 days. The sensor also showed good adhesion even to wet skin, allowing the detection of glucose and pH in sweat from running while being attached onto the skin. This work suggests the application of our stretchable and skin-attachable electrochemical sensor to health management as a high-performance healthcare wearable device.

Non-Enzymatic Wearable Sensor for Electrochemical Analysis of Perspiration Glucose.

Science.gov (United States)

Zhu, Xiaofei; Ju, Yinhui; Chen, Jian; Liu, Deye; Liu, Hong

2018-05-16

We report a non-enzymatic wearable sensor for electrochemical analysis of perspiration glucose. Multi-potential steps are applied on a Au electrode, including a high negative pretreatment potential step for proton reduction which produc-es a localized alkaline condition, a moderate potential step for electrocatalytic oxidation of glucose under the alkaline condi-tion, and a positive potential step to clean and reactivate the electrode surface for the next detection. Fluorocarbon-based materials were coated on the Au electrode for improving the selectivity and robustness of the sensor. A fully integrated wrist-band is developed for continuous real-time monitoring of perspiration glucose during physical activities, and uploading the test result to a Smartphone App via Bluetooth.

Amperometric glucose sensor based on enhanced catalytic reduction of oxygen using glucose oxidase adsorbed onto core-shell Fe{sub 3}O{sub 4}-silica-Au magnetic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Wang Aijun [College of Geography and Environmental Science, College of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004 (China); Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007 (China); Li Yongfang [College of Chemistry and Chemical Engineering, Henan Institute of Science and Technology, Xinxiang 453003 (China); Li Zhonghua [Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007 (China); Feng Jiuju, E-mail: jjfengnju@gmail.com [College of Geography and Environmental Science, College of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004 (China); Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007 (China); Sun Yanli [Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007 (China); Chen Jianrong [College of Geography and Environmental Science, College of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004 (China)

2012-08-01

Monodisperse Fe{sub 3}O{sub 4} magnetic nanoparticles (NPs) were prepared under facile solvothermal conditions and successively functionalized with silica and Au to form core/shell Fe{sub 3}O{sub 4}-silica-Au NPs. Furthermore, the samples were used as matrix to construct a glucose sensor based on glucose oxidase (GOD). The immobilized GOD retained its bioactivity with high protein load of 3.92 Multiplication-Sign 10{sup -9} mol{center_dot}cm{sup -2}, and exhibited a surface-controlled quasi-reversible redox reaction, with a fast heterogeneous electron transfer rate of 7.98 {+-} 0.6 s{sup -1}. The glucose biosensor showed a broad linear range up to 3.97 mM with high sensitivity of 62.45 {mu}A{center_dot}mM{sup -1} cm{sup -2} and fast response (less than 5 s). - Graphical abstract: Core-shell structured Fe{sub 3}O{sub 4}-silica-Au nanoparticles were prepared and used as matrix to construct an amperometric glucose sensor based on glucose oxidase, which showed broad linear range, high sensitivity, and fast response. Highlights: Black-Right-Pointing-Pointer Synthesis of monodispersed Fe{sub 3}O{sub 4} nanoparticles. Black-Right-Pointing-Pointer Fabrication of core/shell Fe{sub 3}O{sub 4}-silica-Au nanoparticles. Black-Right-Pointing-Pointer Construction of a novel glucose sensor with wide linear range, high sensitivity and fast response.

A microfluidic glucose sensor incorporating a novel thread-based electrode system.

Science.gov (United States)

Gaines, Michelle; Gonzalez-Guerrero, Maria Jose; Uchida, Kathryn; Gomez, Frank A

2018-05-01

An electrochemical sensor for the detection of glucose using thread-based electrodes and fabric is described. This device is relatively simple to fabricate and can be used for multiple readings after washing with ethanol. The fabrication of the chip consisted of two steps. First, three thread-based electrodes (reference, working, and counter) were fabricated by painting pieces of nylon thread with either layered silver ink and carbon ink or silver/silver chloride ink. The threads were then woven into a fabric chip with a beeswax barrier molded around the edges in order to prevent leaks from the tested solutions. A thread-based working electrode consisting of one layer of silver underneath two layers of carbon was selected to fabricate the final sensor system. Using the chip, a PBS solution containing glucose oxidase (GOx) (10 mg/mL), potassium ferricyanide (K 3 [Fe(CN) 6 ]) (10 mg/mL) as mediator, and different concentrations of glucose (0-25 mM), was measured by cyclic voltammetry (CV). It was found that the current output from the oxidation of glucose was proportional to the glucose concentrations. This thread-based electrode system is a viable sensor platform for detecting glucose in the physiological range. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Enzymatic and non-enzymatic electrochemical glucose sensor based on carbon nano-onions

Science.gov (United States)

Mohapatra, Jeotikanta; Ananthoju, Balakrishna; Nair, Vishnu; Mitra, Arijit; Bahadur, D.; Medhekar, N. V.; Aslam, M.

2018-06-01

A high sensitive glucose sensing characteristic has been realized in carbon nano-onions (CNOs). The CNOs of mean size 30 nm were synthesized by an energy-efficient, simple and inexpensive combustion technique. These as-synthesized CNOs could be employed as an electrochemical sensor by covalently immobilizing the glucose oxidase enzyme on them via carbodiimide chemistry. The sensitivity achieved by such a sensor is 26.5 μA mM-1 cm-2 with a linear response in the range of 1-10 mM glucose. Further to improve the catalytic activity of the CNOs and also to make them enzyme free, platinum nanoparticles of average size 2.5 nm are decorated on CNOs. This sensor fabricated using Pt-decorated CNOs (Pt@CNOs) nanostructure has shown an enhanced sensitivity of 21.6 μA mM-1 cm-2 with an extended linear response in the range of 2-28 mM glucose. Through these attempts we demonstrate CNOs as a versatile biosensing platform.

Label-free glucose detection using cantilever sensor technology based on gravimetric detection principles.

Science.gov (United States)

Hsieh, Shuchen; Hsieh, Shu-Ling; Hsieh, Chiung-Wen; Lin, Po-Chiao; Wu, Chun-Hsin

2013-01-01

Efficient maintenance of glucose homeostasis is a major challenge in diabetes therapy, where accurate and reliable glucose level detection is required. Though several methods are currently used, these suffer from impaired response and often unpredictable drift, making them unsuitable for long-term therapeutic practice. In this study, we demonstrate a method that uses a functionalized atomic force microscope (AFM) cantilever as the sensor for reliable glucose detection with sufficient sensitivity and selectivity for clinical use. We first modified the AFM tip with aminopropylsilatrane (APS) and then adsorbed glucose-specific lectin concanavalin A (Con A) onto the surface. The Con A/APS-modified probes were then used to detect glucose by monitoring shifts in the cantilever resonance frequency. To confirm the molecule-specific interaction, AFM topographical images were acquired of identically treated silicon substrates which indicated a specific attachment for glucose-Con A and not for galactose-Con A. These results demonstrate that by monitoring the frequency shift of the AFM cantilever, this sensing system can detect the interaction between Con A and glucose, one of the biomolecule recognition processes, and may assist in the detection and mass quantification of glucose for clinical applications with very high sensitivity.

Novel Dry-Type Glucose Sensor Based on a Metal-Oxide-Semiconductor Capacitor Structure with Horseradish Peroxidase + Glucose Oxidase Catalyzing Layer

Science.gov (United States)

Lin, Jing-Jenn; Wu, You-Lin; Hsu, Po-Yen

2007-10-01

In this paper, we present a novel dry-type glucose sensor based on a metal-oxide-semiconductor capacitor (MOSC) structure using SiO2 as a gate dielectric in conjunction with a horseradish peroxidase (HRP) + glucose oxidase (GOD) catalyzing layer. The tested glucose solution was dropped directly onto the window opened on the SiO2 layer, with a coating of HRP + GOD catalyzing layer on top of the gate dielectric. From the capacitance-voltage (C-V) characteristics of the sensor, we found that the glucose solution can induce an inversion layer on the silicon surface causing a gate leakage current flowing along the SiO2 surface. The gate current changes Δ I before and after the drop of glucose solution exhibits a near-linear relationship with increasing glucose concentration. The Δ I sensitivity is about 1.76 nA cm-2 M-1, and the current is quite stable 20 min after the drop of the glucose solution is tested.

Enhancing the accuracy of subcutaneous glucose sensors: a real-time deconvolution-based approach.

Science.gov (United States)

Guerra, Stefania; Facchinetti, Andrea; Sparacino, Giovanni; Nicolao, Giuseppe De; Cobelli, Claudio

2012-06-01

Minimally invasive continuous glucose monitoring (CGM) sensors can greatly help diabetes management. Most of these sensors consist of a needle electrode, placed in the subcutaneous tissue, which measures an electrical current exploiting the glucose-oxidase principle. This current is then transformed to glucose levels after calibrating the sensor on the basis of one, or more, self-monitoring blood glucose (SMBG) samples. In this study, we design and test a real-time signal-enhancement module that, cascaded to the CGM device, improves the quality of its output by a proper postprocessing of the CGM signal. In fact, CGM sensors measure glucose in the interstitium rather than in the blood compartment. We show that this distortion can be compensated by means of a regularized deconvolution procedure relying on a linear regression model that can be updated whenever a pair of suitably sampled SMBG references is collected. Tests performed both on simulated and real data demonstrate a significant accuracy improvement of the CGM signal. Simulation studies also demonstrate the robustness of the method against departures from nominal conditions, such as temporal misplacement of the SMBG samples and uncertainty in the blood-to-interstitium glucose kinetic model. Thanks to its online capabilities, the proposed signal-enhancement algorithm can be used to improve the performance of CGM-based real-time systems such as the hypo/hyper glycemic alert generators or the artificial pancreas.

Design strategy of a graphene based bio-sensor for glucose

DEFF Research Database (Denmark)

Cantatore, Valentina; Pandit, Santosh; Mokkapati, V.R.S.S.

2018-01-01

A novel graphene-based glucose sensor-design is formulated and explored in silico. An ad hoc host molecule is tailored to bind to glucose by multiple hydrogen bonds. A pyridinic core is chosen for this receptor in order to allow for “socket-plug” dative bonding to boron sites of boron doped...

MWCNT-ruthenium oxide composite paste electrode as non-enzymatic glucose sensor.

Science.gov (United States)

Tehrani, Ramin M A; Ab Ghani, Sulaiman

2012-01-01

A non-enzymatic glucose sensor of multi-walled carbon nanotube-ruthenium oxide/composite paste electrode (MWCNT-RuO(2)/CPE) was developed. The electrode was characterized by using XRD, SEM, TEM and EIS. Meanwhile, cyclic voltammetry and amperometry were used to check on the performances of the MWCNT-RuO(2)/CPE towards glucose. The proposed electrode has displayed a synergistic effect of RuO(2) and MWCNT on the electrocatalytic oxidation of glucose in 3M NaOH. This was possible via the formation of transitions of two redox pairs, viz. Ru(VI)/Ru(IV) and Ru(VII)/Ru(VI). A linear range of 0.5-50mM glucose and a limit of detection of 33 μM glucose (S/N=3) were observed. There was no significant interference observable from the traditional interferences, viz. ascorbic acid and uric acid. Indeed, results so obtained have indicated that the developed MWCNT-RuO(2)/CPE would pave the way for a better future to glucose sensor development as its fabrication was without the use of any enzyme. Copyright © 2012 Elsevier B.V. All rights reserved.

Continuous glucose monitoring--a study of the Enlite sensor during hypo- and hyperbaric conditions.

Science.gov (United States)

Adolfsson, Peter; Örnhagen, Hans; Eriksson, Bengt M; Cooper, Ken; Jendle, Johan

2012-06-01

The performance and accuracy of the Enlite(™) (Medtronic, Inc., Northridge, CA) sensor may be affected by microbubble formation at the electrode surface during hypo- and hyperbaric conditions. The effects of acute pressure changes and of prewetting of sensors were investigated. On Day 1, 24 sensors were inserted on the right side of the abdomen and back in one healthy individual; 12 were prewetted with saline solution, and 12 were inserted dry. On Day 2, this procedure was repeated on the left side. All sensors were attached to an iPro continuous glucose monitoring (CGM) recorder. Hypobaric and hyperbaric tests were conducted in a pressure chamber, with each test lasting 105 min. Plasma glucose values were obtained at 5-min intervals with a HemoCue(®) (Ängelholm, Sweden) model 201 glucose analyzer for comparison with sensor glucose values. Ninety percent of the CGM systems operated during the tests. The mean absolute relative difference was lower during hyperbaric than hypobaric conditions (6.7% vs. 14.9%, Phypobaric but not during hyperbaric conditions. Clarke Error Grid Analysis showed that 100% of the values were found in the A+B region. No differences were found between prewetted and dry sensors. The Enlite sensor performed adequately during acute pressure changes and was more accurate during hyperbaric than hypobaric conditions. Prewetting the sensors did not improve accuracy. Further studies on type 1 diabetes subjects are needed under various pressure conditions.

Nonenzymatic glucose sensor based on disposable pencil graphite electrode modified by copper nanoparticles

Directory of Open Access Journals (Sweden)

Sima Pourbeyram

2016-10-01

Full Text Available A nonenzymatic glucose sensor based on a disposable pencil graphite electrode (PGE modified by copper nanoparticles [Cu(NP] was prepared for the first time. The prepared Cu(NP exhibited an absorption peak centered at ∼562 nm using UV-visible spectrophotometry and an almost homogenous spherical shape by scanning electron microscopy. Cyclic voltammetry of Cu(NP-PGE showed an adsorption controlled charge transfer process up to 90.0 mVs−1. The sensor was applied for the determination of glucose using an amperometry technique with a detection limit of [0.44 (±0.01 μM] and concentration sensitivity of [1467.5 (±1.3 μA/mMcm−2]. The preparation of the Cu(NP-PGE sensor was reproducible (relative standard deviation = 2.10%, n = 10, very simple, fast, and inexpensive, and the Cu(NP-PGE is suitable to be used as a disposable glucose sensor.

A flexible and highly sensitive nonenzymatic glucose sensor based on DVD-laser scribed graphene substrate.

Science.gov (United States)

Lin, Songyue; Feng, Wendou; Miao, Xiaofei; Zhang, Xiangxin; Chen, Sujing; Chen, Yuanqiang; Wang, Wei; Zhang, Yining

2018-07-01

Flexible and implantable glucose biosensors are emerging technologies for continuous monitoring of blood-glucose of diabetes. Developing a flexible conductive substrates with high active surface area is critical for advancing the technology. Here, we successfully fabricate a flexible and highly sensitive nonenzymatic glucose by using DVD-laser scribed graphene (LSG) as a flexible conductively substrate. Copper nanoparticles (Cu-NPs) are electrodeposited as the catalyst. The LSG/Cu-NPs sensor demonstrates excellent catalytic activity toward glucose oxidation and exhibits a linear glucose detection range from 1 μM to 4.54 mM with high sensitivity (1.518 mA mM -1 cm -2 ) and low limit of detection (0.35 μM). Moreover, the LSG/Cu-NPs sensor shows excellent reproducibility and long-term stability. It is also highly selective toward glucose oxidation under the presence of various interfering species. Excellent flexing stability is also demonstrated by the LSG/Cu-NPs sensor, which is capable of maintaining 83.9% of its initial current after being bent against a 4-mm diameter rod for 180 times. The LSG/Cu-NPs sensor shows great potential for practical application as a nonenzymatic glucose biosensor. Meanwhile, the LSG conductive substrate provides a platform for the developing next-generation flexible and potentially implantable bioelectronics and biosensors. Copyright © 2018 Elsevier B.V. All rights reserved.

In-vitro performance of the Enlite Sensor in various glucose concentrations during hypobaric and hyperbaric conditions.

Science.gov (United States)

Adolfsson, Peter; Ornhagen, Hans; Eriksson, Bengt M; Gautham, Raghavendhar; Jendle, Johan

2012-11-01

There is a need for reliable methods of glucose measurement in different environmental conditions. The objective of this in vitro study was to evaluate the performance of the Enlite® Sensor when connected to either the iPro™ Continuous Glucose Monitor recording device or the Guardian® REAL-Time transmitting device, in hypobaric and hyperbaric conditions. Sixteen sensors connected to eight iPro devices and eight Guardian REAL-Time devices were immersed in three beakers containing separate glucose concentrations: 52, 88, and 207 mg/dl (2.9, 4.9, and 11.3 mmol/liter). Two different pressure tests were conducted: a hypobaric test, corresponding to maximum 18000 ft/5500 m height, and a hyperbaric test, corresponding to maximum 100 ft/30 m depth. The linearity of the sensor signals in the different conditions was evaluated. The sensors worked continuously, and the sensor signals were collected without interruption at all pressures tested. When comparing the input signals for glucose (ISIGs) and the different glucose concentrations during altered pressure, linearity (R(2)) of 0.98 was found. During the hypobaric test, significant differences (p hyperbaric test, no differences were found. The Enlite Sensors connected to either the iPro or the Guardian REAL-Time device provided values continuously. In hyperbaric conditions, no significant differences were seen during changes in ambient pressure; however, during hypobaric conditions, the ISIG was significantly different in the low and high glucose concentrations. © 2012 Diabetes Technology Society.

An extremely sensitive monoboronic acid based fluorescent sensor for glucose

International Nuclear Information System (INIS)

Sun Xiangying; Liu Bin; Jiang Yunbao

2004-01-01

An extremely sensitive monoboronic acid based fluorescent sensor for glucose was developed. This was carried out by assembling a fluorescent monoboronic acid, 3-aminophenylboronic acid (PBA) indirectly onto gold surface via its electrostatic interaction with cysteine (Cys) that was directly assembled on the gold surface. The formation of self-assembled bilayers (SAB) was confirmed and primarily characterized by cyclic voltammetry and X-ray photoelectron spectra (XPS). The SAB containing PBA was found fluorescent and its fluorescence showed an extremely high sensitivity to the presence of glucose and other monosaccharides such as galactose and fructose with quenching constants at 10 8 M -1 order of magnitude compared to those at 10 2 M -1 in bulk solutions. The quenching constants were found to vary in the order of D-glucose>D-galactose>D-fructose>D-mannose that is different from that in bulk solution which shows the highest binding affinity toward D-fructose and very low sensitivity toward glucose. The reported monoboronic acid based SAB fluorescent sensor showed the highest sensitivity towards glucose with the capacity of detecting saccharides of concentration down to nanomolar level. It was also demonstrated that the fluorescence from PBA/Cys/Au can be easily recovered after each measurement event and therefore also represents a new reusable method for immobilizing reagent in fabricating chemosensors

A fine pointed glucose oxidase immobilized electrode for low-invasive amperometric glucose monitoring.

Science.gov (United States)

Li, Jiang; Koinkar, Pankaj; Fuchiwaki, Yusuke; Yasuzawa, Mikito

2016-12-15

A low invasive type glucose sensor, which has a sensing region at the tip of a fine pointed electrode, was developed for continuous glucose monitoring. Platinum-iridium alloy electrode with a surface area of 0.045mm(2) was settled at the middle of pointed PEEK (Polyetheretherketone) tubing and was employed as sensing electrode. Electrodeposition of glucose oxidase in the presence of surfactant, Triton X-100, was performed for high-density enzyme immobilization followed by the electropolymerization of o-phenylenediamine for the formation of functional entrapping and permselective polymer membrane. Ag/AgCl film was coated on the surface of PEEK tubing as reference electrode. Amperometric responses of the prepared sensors to glucose were measured at a potential of 0.60V (vs. Ag/AgCl). The prepared electrode showed the sensitivity of 2.55μA/cm(2) mM with high linearity of 0.9986, within the glucose concentration range up to 21mM. The detection limit (S/N=3) was determined to be 0.11mM. The glucose sensor properties were evaluated in phosphate buffer solution and in vivo monitoring by the implantation of the sensors in rabbit, while conventional needle type sensors as a reference were used. The results showed that change in output current of the proposed sensor fluctuated similar with one in output current of the conventional needle type sensors, which was also in similar accordance with actual blood sugar level measured by commercially glucose meter. One-point calibration method was used to calibrate the sensor output current. Copyright © 2016 Elsevier B.V. All rights reserved.

Modeling the Error of the Medtronic Paradigm Veo Enlite Glucose Sensor.

Science.gov (United States)

Biagi, Lyvia; Ramkissoon, Charrise M; Facchinetti, Andrea; Leal, Yenny; Vehi, Josep

2017-06-12

Continuous glucose monitors (CGMs) are prone to inaccuracy due to time lags, sensor drift, calibration errors, and measurement noise. The aim of this study is to derive the model of the error of the second generation Medtronic Paradigm Veo Enlite (ENL) sensor and compare it with the Dexcom SEVEN PLUS (7P), G4 PLATINUM (G4P), and advanced G4 for Artificial Pancreas studies (G4AP) systems. An enhanced methodology to a previously employed technique was utilized to dissect the sensor error into several components. The dataset used included 37 inpatient sessions in 10 subjects with type 1 diabetes (T1D), in which CGMs were worn in parallel and blood glucose (BG) samples were analyzed every 15 ± 5 min Calibration error and sensor drift of the ENL sensor was best described by a linear relationship related to the gain and offset. The mean time lag estimated by the model is 9.4 ± 6.5 min. The overall average mean absolute relative difference (MARD) of the ENL sensor was 11.68 ± 5.07% Calibration error had the highest contribution to total error in the ENL sensor. This was also reported in the 7P, G4P, and G4AP. The model of the ENL sensor error will be useful to test the in silico performance of CGM-based applications, i.e., the artificial pancreas, employing this kind of sensor.

Enzyme-Free Electrochemical Glucose Sensors Prepared by Dealloying Pd-Ni-P Metallic Glasses

Directory of Open Access Journals (Sweden)

Yuqiao Zeng

2014-01-01

Full Text Available We report the formation of enzyme-free electrochemical glucose sensors by electrochemical dealloying palladium-containing Pd-Ni-P metallic glasses. When metallic glasses with different Pd contents are used as the dealloying precursor alloys, palladium-based nanoporous metals with different ligament and pore sizes can be obtained. The chemical compositions of the nanoporous metals also vary according to the different precursor compositions. All the as-obtained nanoporous metals exhibit electrochemical catalytic activity towards the oxidation of d-glucose, indicating that the nanoporous metals prepared by dealloying the Pd-Ni-P metallic glasses are promising materials for enzyme-free electrochemical glucose sensor.

A selective glucose sensor based on direct oxidation on a bimetal catalyst with a molecular imprinted polymer.

Science.gov (United States)

Cho, Seong Je; Noh, Hui-Bog; Won, Mi-Sook; Cho, Chul-Ho; Kim, Kwang Bok; Shim, Yoon-Bo

2018-01-15

A selective nonenzymatic glucose sensor was developed based on the direct oxidation of glucose on hierarchical CuCo bimetal-coated with a glucose-imprinted polymer (GIP). Glucose was introduced into the GIP composed of Nafion and polyurethane along with aminophenyl boronic acid (APBA), which was formed on the bimetal electrode formed on a screen-printed electrode. The extraction of glucose from the GIP allowed for the selective permeation of glucose into the bimetal electrode surface for oxidation. The GIP-coated bimetal sensor probe was characterized using electrochemical and surface analytical methods. The GIP layer coated on the NaOH pre-treated bimetal electrode exhibited a dynamic range between 1.0µM and 25.0mM with a detection limit of 0.65±0.10µM in phosphate buffer solution (pH 7.4). The anodic responses of uric acid, acetaminophen, dopamine, ascorbic acid, L-cysteine, and other saccharides (monosaccharides: galactose, mannose, fructose, and xylose; disaccharides: sucrose, lactose, and maltose) were not detected using the GIP-coated bimetal sensor. The reliability of the sensor was evaluated by the determination of glucose in artificial and whole blood samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Non-enzymatic glucose detection based on phenylboronic acid modified optical fibers

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Sun, Xiaolan; Li, Nana; Zhou, Bin; Zhao, Wei; Liu, Liyuan; Huang, Chao; Ma, Longfei; Kost, Alan R.

2018-06-01

A non-enzymatic, sensitive glucose sensor was fabricated based on an evanescent wave absorbing optical fiber probe. The optical fiber sensor was functionalized by fixing a poly (phenylboronic acid) (polyPBA) film onto the conical region of the single mode fiber. The reflected light intensity of the polyPBA-functionalized fiber sensor increased proportionally with glucose concentration in the range of 0-60 mM, and the sensor showed good reproducibility and stability. The developed sensor possessed a high sensitivity of 0.1787%/mM and good linearity. The measurement of glucose concentration in human serum was also demonstrated.

Engineering glucose oxidase to minimize the influence of oxygen on sensor response

International Nuclear Information System (INIS)

Horaguchi, Yohei; Saito, Shoko; Kojima, Katsuhiro; Tsugawa, Wakako; Ferri, Stefano; Sode, Koji

2014-01-01

Glucose oxidase (GOx) is an important industrial enzyme and is recognized as the gold standard for monitoring blood glucose. However, due to its inherent oxidase property, the presence of oxygen affects electrochemical measurements of venous blood glucose employing artificial electron mediators. We therefore attempted to engineer Penicillium amagasakiense-derived GOx into a dehydrogenase by focusing on the amino acid residues predicted to interact with oxygen. Our rational amino acid substitution approach resulted in the construction of the Ser114Ala/Phe355Leu mutant, which has an 11-fold decrease in oxidase activity and 2.8-fold increase in dehydrogenase activity compared with wild-type GOx. As a result, the dehydrogenase/oxidase activity ratio of the engineered enzyme was 32-fold greater than that of the wild-type enzyme. The enzyme sensor constructed with Ser114Ala/Phe355Leu was considerably less affected by oxygen than the wild-type GOx-based sensor at lower glucose concentrations

Preparation of Glucose Sensor Using Polydimethylsiloxane / Polypyrrole Complex

Science.gov (United States)

Yasuzawa, Mikito; Inoue, Shigeru; Imai, Shinji

New glucose oxidase (GOD) immobilized glucose sensors were prepared by the electropolymerization of 1-(6-D-gluconamidohexyl) pyrrole (GHP) on the platinum wire electrode precoated with the mixture solution of pyrrole derivative GHP, polydimethylsiloxane (PDS) and Nafion. The addition of Nafion into the precoating mixture solution was essential to obtain suitable sensor sensitivity. However, the sensitivity was about the half of that of the electrode without PDS precoating. Although, the introduction of Nafion was effective to improve the long-term stability of the enzyme-immobilized electrode, the electrode prepared using Nafion, PDS and GHP performed excellent long-term stability even at the measurement and storage temperatures of 40°C. Relatively constant response current was obtained over 30 days under the condition of 40°C and over 9 months measured at 25°C. Moreover, the GOD-immobilized GHP polymer film prepared on the electrode precoated with GHP, PDS and Nafion solution, was found to have excellent hemocompatibility from the result of platelet rich plasma contacting test.

Assessing sensor accuracy for non-adjunct use of continuous glucose monitoring.

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Kovatchev, Boris P; Patek, Stephen D; Ortiz, Edward Andrew; Breton, Marc D

2015-03-01

The level of continuous glucose monitoring (CGM) accuracy needed for insulin dosing using sensor values (i.e., the level of accuracy permitting non-adjunct CGM use) is a topic of ongoing debate. Assessment of this level in clinical experiments is virtually impossible because the magnitude of CGM errors cannot be manipulated and related prospectively to clinical outcomes. A combination of archival data (parallel CGM, insulin pump, self-monitoring of blood glucose [SMBG] records, and meals for 56 pump users with type 1 diabetes) and in silico experiments was used to "replay" real-life treatment scenarios and relate sensor error to glycemic outcomes. Nominal blood glucose (BG) traces were extracted using a mathematical model, yielding 2,082 BG segments each initiated by insulin bolus and confirmed by SMBG. These segments were replayed at seven sensor accuracy levels (mean absolute relative differences [MARDs] of 3-22%) testing six scenarios: insulin dosing using sensor values, threshold, and predictive alarms, each without or with considering CGM trend arrows. In all six scenarios, the occurrence of hypoglycemia (frequency of BG levels ≤50 mg/dL and BG levels ≤39 mg/dL) increased with sensor error, displaying an abrupt slope change at MARD =10%. Similarly, hyperglycemia (frequency of BG levels ≥250 mg/dL and BG levels ≥400 mg/dL) increased and displayed an abrupt slope change at MARD=10%. When added to insulin dosing decisions, information from CGM trend arrows, threshold, and predictive alarms resulted in improvement in average glycemia by 1.86, 8.17, and 8.88 mg/dL, respectively. Using CGM for insulin dosing decisions is feasible below a certain level of sensor error, estimated in silico at MARD=10%. In our experiments, further accuracy improvement did not contribute substantively to better glycemic outcomes.

An NFC-Enabled CMOS IC for a Wireless Fully Implantable Glucose Sensor.

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DeHennis, Andrew; Getzlaff, Stefan; Grice, David; Mailand, Marko

2016-01-01

This paper presents an integrated circuit (IC) that merges integrated optical and temperature transducers, optical interface circuitry, and a near-field communication (NFC)-enabled digital, wireless readout for a fully passive implantable sensor platform to measure glucose in people with diabetes. A flip-chip mounted LED and monolithically integrated photodiodes serve as the transduction front-end to enable fluorescence readout. A wide-range programmable transimpedance amplifier adapts the sensor signals to the input of an 11-bit analog-to-digital converter digitizing the measurements. Measurement readout is enabled by means of wireless backscatter modulation to a remote NFC reader. The system is able to resolve current levels of less than 10 pA with a single fluorescent measurement energy consumption of less than 1 μJ. The wireless IC is fabricated in a 0.6-μm-CMOS process and utilizes a 13.56-MHz-based ISO15693 for passive wireless readout through a NFC interface. The IC is utilized as the core interface to a fluorescent, glucose transducer to enable a fully implantable sensor-based continuous glucose monitoring system.

Functional imaging and assessment of the glucose diffusion rate in epithelial tissues in optical coherence tomography

International Nuclear Information System (INIS)

Larin, K V; Tuchin, V V

2008-01-01

Functional imaging, monitoring and quantitative description of glucose diffusion in epithelial and underlying stromal tissues in vivo and controlling of the optical properties of tissues are extremely important for many biomedical applications including the development of noninvasive or minimally invasive glucose sensors as well as for therapy and diagnostics of various diseases, such as cancer, diabetic retinopathy, and glaucoma. Recent progress in the development of a noninvasive molecular diffusion biosensor based on optical coherence tomography (OCT) is described. The diffusion of glucose was studied in several epithelial tissues both in vitro and in vivo. Because OCT provides depth-resolved imaging of tissues with high in-depth resolution, the glucose diffusion is described not only as a function of time but also as a function of depth. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)

Ratiometric glucose sensing based on fluorescent oxygen films and glucose oxidase

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Fengyu Su

2017-06-01

Full Text Available A new two-layer sensor film was constructed for sensing glucose based on glucose oxidase and oxygen sensing material. The first layer of film containing the oxygen sensor and intra-reference material was polymerized, then the second layer of glucose oxidase and glutaraldehyde was formed on the oxygen sensor layer. The two-layer sensor film has a resolution up to 0.05 mM and a detection range from 0 to 5 mM to glucose. The effects of pH and temperature on the sensing performance were systematically investigated. The selective detection of glucose among other monosaccharides, such as fructose, mannose and galactose indicated that the sensing film has excellent selectivity. The prepared sensor was successfully applied for glucose sample detection of glucose concentration in artificial tears. Keywords: Glucose sensor, Glucose oxidase, Fluorescence, Oxygen film, Diabetes

Glucose Sensing Using Functionalized Amorphous In-Ga-Zn-O Field-Effect Transistors.

Science.gov (United States)

Du, Xiaosong; Li, Yajuan; Motley, Joshua R; Stickle, William F; Herman, Gregory S

2016-03-01

Recent advances in glucose sensing have focused on the integration of sensors into contact lenses to allow noninvasive continuous glucose monitoring. Current technologies focus primarily on enzyme-based electrochemical sensing which requires multiple nontransparent electrodes to be integrated. Herein, we leverage amorphous indium gallium zinc oxide (IGZO) field-effect transistors (FETs), which have found use in a wide range of display applications and can be made fully transparent. Bottom-gated IGZO-FETs can have significant changes in electrical characteristics when the back-channel is exposed to different environments. We have functionalized the back-channel of IGZO-FETs with aminosilane groups that are cross-linked to glucose oxidase and have demonstrated that these devices have high sensitivity to changes in glucose concentrations. Glucose sensing occurs through the decrease in pH during glucose oxidation, which modulates the positive charge of the aminosilane groups attached to the IGZO surface. The change in charge affects the number of acceptor-like surface states which can deplete electron density in the n-type IGZO semiconductor. Increasing glucose concentrations leads to an increase in acceptor states and a decrease in drain-source conductance due to a positive shift in the turn-on voltage. The functionalized IGZO-FET devices are effective in minimizing detection of interfering compounds including acetaminophen and ascorbic acid. These studies suggest that IGZO FETs can be effective for monitoring glucose concentrations in a variety of environments, including those where fully transparent sensing elements may be of interest.

Bacteria-Templated NiO Nanoparticles/Microstructure for an Enzymeless Glucose Sensor

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Settu Vaidyanathan

2016-07-01

Full Text Available The bacterial-induced hollow cylinder NiO (HCNiO nanomaterial was utilized for the enzymeless (without GOx detection of glucose in basic conditions. The determination of glucose in 0.05 M NaOH solution with high sensitivity was performed using cyclic voltammetry (CV and amperometry (i–t. The fundamental electrochemical parameters were analyzed and the obtained values of diffusion coefficient (D, heterogeneous rate constant (ks, electroactive surface coverage (Г, and transfer coefficient (alpha-α are 1.75 × 10−6 cm2/s, 57.65 M−1·s−1, 1.45 × 10−10 mol/cm2, and 0.52 respectively. The peak current of the i–t method shows two dynamic linear ranges of calibration curves 0.2 to 3.5 µM and 0.5 to 250 µM for the glucose electro-oxidation. The Ni2+/Ni3+ couple with the HCNiO electrode and the electrocatalytic properties were found to be sensitive to the glucose oxidation. The green chemistry of NiO preparation from bacteria and the high catalytic ability of the oxyhydroxide (NiOOH is the good choice for the development of a glucose sensor. The best obtained sensitivity and limit of detection (LOD for this sensor were 3978.9 µA mM−1·cm−2 and 0.9 µM, respectively.

Construction of a non-enzymatic sensor based on the poly(o-phenylenediamine)/Ag-NPs composites for detecting glucose in blood

Energy Technology Data Exchange (ETDEWEB)

Wang, Jinxiang; Wang, Meirong [College of Chemistry and Chemical Engineering, Jiangsu Key Laboratory of Environmental Engineering and Monitoring, Yangzhou University, 180 Si–Wang–Ting Road, Yangzhou 225002 (China); Guan, Jun [Clinical Medical College of Yangzhou University, Subei People' s Hospital of Jiangsu Province, Yangzhou 225002 (China); Wang, Chengyin, E-mail: wangcy@yzu.edu.cn [College of Chemistry and Chemical Engineering, Jiangsu Key Laboratory of Environmental Engineering and Monitoring, Yangzhou University, 180 Si–Wang–Ting Road, Yangzhou 225002 (China); Wang, Guoxiu [School of Mathematical and Physical Sciences, University of Technology Sydney, City Campus, Broadway, Sydney, NSW 2007 (Australia)

2017-02-01

A non-enzymatic glucose sensor, based on the silver nanoparticles (Ag-NPs)/poly (o-phenylenediamine) (PoPD) composites, is developed by the electrochemical polymerization of o-phenylenediamine and electrodeposition of silver nanoparticles on an indium tin oxide electrode. The Ag-NPs/PoPD composites are characterized by atomic force microscopy, scanning electronic microscopy and energy dispersive spectrometer. Under the optimized experimental conditions, the proposed glucose sensor demonstrates a wide linear range from 0.15 to 13 mmol L{sup −1} with a correlation coefficient of 0.998. The proposed glucose sensor can be used to detect glucose in blood sample with a satisfactory result. In addition, the proposed sensor presents the advantages, such as facile preparation, low cost, high sensitivity and fast response time. It also exhibits good anti-interference performance and stability. - Highlights: • A facile AgNPs/PoPD/ITO modified sensor was developed for the first time. • The non-enzymatic sensor can detect glucose in human blood directly with a wide detection range. • This sensor is of rapid response, low cost, high sensitivity, and long-time stability.

Direct electrochemistry of glucose oxidase immobilized on nanostructured gold thin films and its application to bioelectrochemical glucose sensor

International Nuclear Information System (INIS)

Qiu Cuicui; Wang Xia; Liu Xueying; Hou Shifeng; Ma Houyi

2012-01-01

Highlights: ► Au thin films are formed by electrodeposition and galvanic replacement technology. ► Glucose oxidase is stably immobilized via a simple physical adsorption method. ► The direct electrochemical behavior is obtained on the immobilized glucose oxidase. ► An amperometric sensor of glucose with an excellent sensing capability is achieved. - Abstract: Glucose oxidase (GOx) was stably immobilized via a simple physical adsorption method onto the nanostructured Au thin films fabricated by using electrodeposition and galvanic replacement technology, which provides a facile method to prepare morphology-controllable Au films and also facilitates the preparation and application of enzyme modified electrodes. An obvious advantage of the as-prepared enzyme electrode (denoted as GOx/Au/GCE) is that the nano-Au films provide a favorable microenvironment for GOx and facilitate the electron transfer between the active center of GOx and electrodes. Cyclic voltammetry (CV) results indicate that the immobilized GOx displayed a direct, reversible and surface-confined redox reaction in the phosphate buffer solution. Furthermore, the enzyme modified electrode was used as a glucose bioelectrochemical sensor, exhibiting a linear relationship in the concentration ranges of 2.5–32.5 μmol L −1 and 60–130 μmol L −1 with a detection limit of 0.32 μmol L −1 (S/N = 3) at an applied potential of −0.55 V. Due to the excellent stability, sensitivity and anti-interference ability, the Au thin films are hopeful in the construction of glucose biosensors.

"Smart tattoo" glucose biosensors and effect of coencapsulated anti-inflammatory agents.

Science.gov (United States)

Srivastava, Rohit; Jayant, Rahul Dev; Chaudhary, Ayesha; McShane, Michael J

2011-01-01

Minimally invasive glucose biosensors with increased functional longevity form one of the most promising techniques for continuous glucose monitoring. In the present study, we developed a novel nanoengineered microsphere formulation comprising alginate microsphere glucose sensors and anti-inflammatory-drug-loaded alginate microspheres. The formulation was prepared and characterized for size, shape, in vitro drug release, biocompatibility, and in vivo acceptability. Glucose oxidase (GOx)- and Apo-GOx-based glucose sensors were prepared and characterized. Sensing was performed both in distilled water and simulated interstitial body fluid. Layer-by-layer self-assembly techniques were used for preventing drug and sensing chemistry release. Finally, in vivo studies, involving histopathologic examination of subcutaneous tissue surrounding the implanted sensors using Sprague-Dawley rats, were performed to test the suppression of inflammation and fibrosis associated with glucose sensor implantation. The drug formulation showed 100% drug release with in 30 days with zero-order release kinetics. The GOx-based sensors showed good enzyme retention and enzyme activity over a period of 1 month. Apo-GOx-based visible and near-infrared sensors showed good sensitivity and analytical response range of 0-50 mM glucose, with linear range up to 12 mM glucose concentration. In vitro cell line studies proved biocompatibility of the material used. Finally, both anti-inflammatory drugs were successful in controlling the implant-tissue interface by suppressing inflammation at the implant site. The incorporation of anti-inflammatory drug with glucose biosensors shows promise in improving sensor biocompatibility, thereby suggesting potential application of alginate microspheres as "smart tattoo" glucose sensors with increased functional longevity. © 2010 Diabetes Technology Society.

Silver nanoparticles decorated carboxylate functionalized SiO2, New nanocomposites for non-enzymatic detection of glucose and hydrogen peroxide

International Nuclear Information System (INIS)

Ensafi, Ali A.; Zandi-Atashbar, N.; Rezaei, B.; Ghiaci, M.; Taghizadeh, M.

2016-01-01

Highlights: • Silver nanoparticles decorated carboxylates functionalized SiO 2 were prepared. • Ligands are bonding to silica support as SiO 2 –pro–NH 2 and SiO 2 –pro–NH–cyanuric–NH 2 . • These nanomaterials were used as electrochemical sensors for H 2 O 2 and glucose detection. • H 2 O 2 and glucose could be detected as low as 0.094 and 0.33 μmol L −1 , respectively. - Abstract: Here, two different nanocomposites are prepared based on the decoration of silver nanoparticles (AgNPs) on carboxylated SiO 2 . SiO 2 was functionalized with two different carboxylate ligands to stabilize silver nanoparticles on them, using two different organic bondings. Then, AgNPs were decorated successfully on the surface of the functionalized SiO 2 . The functionalized SiO 2 and AgNPs-functionalized SiO 2 were characterized using Fourier transform infrared spectroscopy, elemental analyses, and Transmission electron microscopy (TEM). For further characterization, the generated nanoparticles were employed as modifiers in the preparation of carbon paste electrodes (CPEs). Then, cyclic voltammetry and electrochemical impedance spectroscopy were used to study their electrochemical behavior. The electrochemical data exhibited that the modifications of CPE led to easier electron transfers rather than the bare and unmodified SiO 2 /CPE due to the presence of functionalized SiO 2 in accompany with electrocatalytic effects of the decorated silver nanoparticles. Furthermore, the modified–CPEs were examined as non–enzymatic H 2 O 2 and glucose sensors using electrochemical techniques including cyclic voltammetry and hydrodynamic chronoamperometric. Electrochemical results represented that the modified-CPE is efficient and sensitive for H 2 O 2 and glucose detection as low as 0.094 and 0.33 μmol L −1 , respectively. At last, the practical applications of these sensors were also evaluated by analyzing H 2 O 2 and glucose in the presence of common interfering species

A Cuprous Oxide Thin Film Non-Enzymatic Glucose Sensor Using Differential Pulse Voltammetry and Other Voltammetry Methods and a Comparison to Different Thin Film Electrodes on the Detection of Glucose in an Alkaline Solution

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Yifan Dai

2018-01-01

Full Text Available A cuprous oxide (Cu2O thin layer served as the base for a non-enzymatic glucose sensor in an alkaline medium, 0.1 NaOH solution, with a linear range of 50–200 mg/dL using differential pulse voltammetry (DPV measurement. An X-ray photoelectron spectroscopy (XPS study confirmed the formation of the cuprous oxide layer on the thin gold film sensor prototype. Quantitative detection of glucose in both phosphate-buffered saline (PBS and undiluted human serum was carried out. Neither ascorbic acid nor uric acid, even at a relatively high concentration level (100 mg/dL in serum, interfered with the glucose detection, demonstrating the excellent selectivity of this non-enzymatic cuprous oxide thin layer-based glucose sensor. Chronoamperometry and single potential amperometric voltammetry were used to verify the measurements obtained by DPV, and the positive results validated that the detection of glucose in a 0.1 M NaOH alkaline medium by DPV measurement was effective. Nickel, platinum, and copper are commonly used metals for non-enzymatic glucose detection. The performance of these metal-based sensors for glucose detection using DPV were also evaluated. The cuprous oxide (Cu2O thin layer-based sensor showed the best sensitivity for glucose detection among the sensors evaluated.

Liquid-Phase Packaging of a Glucose Oxidase Solution with Parylene Direct Encapsulation and an Ultraviolet Curing Adhesive Cover for Glucose Sensors

OpenAIRE

Seiichi Takamatsu; Hisanori Takano; Nguyen Binh-Khiem; Tomoyuki Takahata; Eiji Iwase; Kiyoshi Matsumoto; Isao Shimoyama

2010-01-01

We have developed a package for disposable glucose sensor chips using Parylene encapsulation of a glucose oxidase solution in the liquid phase and a cover structure made of an ultraviolet (UV) curable adhesive. Parylene was directly deposited onto a small volume (1 μL) of glucose oxidase solution through chemical vapor deposition. The cover and reaction chamber were constructed on Parylene film using a UV-curable adhesive and photolithography. The package was processed at room temperature to ...

Nanosensors and nanomaterials for monitoring glucose in diabetes.

Science.gov (United States)

Cash, Kevin J; Clark, Heather A

2010-12-01

Worldwide, diabetes is a rapidly growing problem that is managed at the individual level by monitoring and controlling blood glucose levels to minimize the negative effects of the disease. Because of limitations in diagnostic methods, significant research efforts are focused on developing improved methods to measure glucose. Nanotechnology has impacted these efforts by increasing the surface area of sensors, improving the catalytic properties of electrodes and providing nanoscale sensors. Here, we discuss developments in the past several years on both nanosensors that directly measure glucose and nanomaterials that improve glucose sensor function. Finally, we discuss challenges that must be overcome to apply these developments in the clinic. Copyright © 2010 Elsevier Ltd. All rights reserved.

Reusable urine glucose sensor based on functionalized graphene oxide conjugated Au electrode with protective layers

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Hye Youn Kim

2014-09-01

Full Text Available An electrochemical based system with multiple layers coated on a functionalized graphene oxide Au electrode was developed to measure glucose concentration in urine in a more stable way. Two types of gold printed circuit boards were fabricated and graphene oxide was immobilized on their surface by chemical adsorption. Multiple layers, composed of a couple of polymers, were uniformly coated on the surface electrode. This device exhibited higher electrochemical responses against glucose, a greater resistivity in the presence of interferential substances in urine, and durable stabilities for longer periods of time than conventional units. The efficiency in current level according to the order and ratio of solution was evaluated during the immobilization of the layer. The fabricated electrodes were then also evaluated using hyperglycemic clinical samples and compared with the patterns of blood glucose measured with commercially available glucose meters. Our findings show that not only was their pattern similar but this similarity is well correlated.

DNA-dispersed graphene/NiO hybrid materials for highly sensitive non-enzymatic glucose sensor

International Nuclear Information System (INIS)

Lv Wei; Jin Fengmin; Guo Quangui; Yang Quanhong; Kang Feiyu

2012-01-01

Highlights: ► We investigated the potential of GNS/NiO/DNA hybrid used as a nonenzymatic sensor. ► DNA is a highly efficient disperse agent for GNS/NiO hybrid than ionic surfactants. ► GNS/NiO/DNA hybrid shows fast electron transfer in the electrochemical reaction. ► GNS/NiO/DNA hybrid shows good detection performance towards glucose. - Abstract: We demonstrate graphene nanosheet/NiO hybrids (GNS/NiO) as the active material for high-performance non-enzymatic glucose sensors. Such sensors are fabricated by DNA-dispersed GNS/NiO suspension deposited on glassy carbon electrodes. ss-DNA shows strong dispersing ability for the GNS/NiO hybrid materials resulting in stable water-dispersible GNS/NiO/DNA hybrids with fully separated layers. The GNS/NiO/DNA hybrids show enhanced electron transfer in the electrocatalytic reaction process, and accordingly, such hybrids modified electrodes show good sensing performance towards glucose and are characterized by large detection ranges, short response periods, low detection limit and high sensitivity and stability.

Liquid-Phase Packaging of a Glucose Oxidase Solution with Parylene Direct Encapsulation and an Ultraviolet Curing Adhesive Cover for Glucose Sensors

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Seiichi Takamatsu

2010-06-01

Full Text Available We have developed a package for disposable glucose sensor chips using Parylene encapsulation of a glucose oxidase solution in the liquid phase and a cover structure made of an ultraviolet (UV curable adhesive. Parylene was directly deposited onto a small volume (1 μL of glucose oxidase solution through chemical vapor deposition. The cover and reaction chamber were constructed on Parylene film using a UV-curable adhesive and photolithography. The package was processed at room temperature to avoid denaturation of the glucose oxidase. The glucose oxidase solution was encapsulated and unsealed. Glucose sensing was demonstrated using standard amperometric detection at glucose concentrations between 0.1 and 100 mM, which covers the glucose concentration range of diabetic patients. Our proposed Parylene encapsulation and UV-adhesive cover form a liquid phase glucose-oxidase package that has the advantages of room temperature processing and direct liquid encapsulation of a small volume solution without use of conventional solidifying chemicals.

Ultrasensitive binder-free glucose sensors based on the pyrolysis of in situ grown Cu MOF

DEFF Research Database (Denmark)

Zhang, Xuan; Luo, Jiangshui; Tang, Pengyi

2017-01-01

A non-enzymatic glucose sensor based on carbon/Cu composite materials was developed by the in-situ growth and subsequent pyrolysis of metal-organic frameworks (MOFs) on Cu foam. After pyrolysis, SEM, HRTEM and STEM-EELS were employed to clarify the hierarchical Cu@porous carbon electrode. It is f......A non-enzymatic glucose sensor based on carbon/Cu composite materials was developed by the in-situ growth and subsequent pyrolysis of metal-organic frameworks (MOFs) on Cu foam. After pyrolysis, SEM, HRTEM and STEM-EELS were employed to clarify the hierarchical Cu@porous carbon electrode...... matrix electrode displays ultrahigh sensitivity (10.1 mA cm−2 mM−1), low detection limit (sensors....

Evaluating the clinical accuracy of two continuous glucose sensors using continuous glucose-error grid analysis.

Science.gov (United States)

Clarke, William L; Anderson, Stacey; Farhy, Leon; Breton, Marc; Gonder-Frederick, Linda; Cox, Daniel; Kovatchev, Boris

2005-10-01

To compare the clinical accuracy of two different continuous glucose sensors (CGS) during euglycemia and hypoglycemia using continuous glucose-error grid analysis (CG-EGA). FreeStyle Navigator (Abbott Laboratories, Alameda, CA) and MiniMed CGMS (Medtronic, Northridge, CA) CGSs were applied to the abdomens of 16 type 1 diabetic subjects (age 42 +/- 3 years) 12 h before the initiation of the study. Each system was calibrated according to the manufacturer's recommendations. Each subject underwent a hyperinsulinemic-euglycemic clamp (blood glucose goal 110 mg/dl) for 70-210 min followed by a 1-mg.dl(-1).min(-1) controlled reduction in blood glucose toward a nadir of 40 mg/dl. Arterialized blood glucose was determined every 5 min using a Beckman Glucose Analyzer (Fullerton, CA). CGS glucose recordings were matched to the reference blood glucose with 30-s precision, and rates of glucose change were calculated for 5-min intervals. CG-EGA was used to quantify the clinical accuracy of both systems by estimating combined point and rate accuracy of each system in the euglycemic (70-180 mg/dl) and hypoglycemic (<70 mg/dl) ranges. A total of 1,104 data pairs were recorded in the euglycemic range and 250 data pairs in the hypoglycemic range. Overall correlation between CGS and reference glucose was similar for both systems (Navigator, r = 0.84; CGMS, r = 0.79, NS). During euglycemia, both CGS systems had similar clinical accuracy (Navigator zones A + B, 88.8%; CGMS zones A + B, 89.3%, NS). However, during hypoglycemia, the Navigator was significantly more clinically accurate than the CGMS (zones A + B = 82.4 vs. 61.6%, Navigator and CGMS, respectively, P < 0.0005). CG-EGA is a helpful tool for evaluating and comparing the clinical accuracy of CGS systems in different blood glucose ranges. CG-EGA provides accuracy details beyond other methods of evaluation, including correlational analysis and the original EGA.

Ratiometric glucose sensing based on fluorescent oxygen films and glucose oxidase

OpenAIRE

Fengyu Su; Liqiang Zhang; Xiangxing Kong; Fred Lee; Yanqing Tian; Deirdre R. Meldrum

2017-01-01

A new two-layer sensor film was constructed for sensing glucose based on glucose oxidase and oxygen sensing material. The first layer of film containing the oxygen sensor and intra-reference material was polymerized, then the second layer of glucose oxidase and glutaraldehyde was formed on the oxygen sensor layer. The two-layer sensor film has a resolution up to 0.05 mM and a detection range from 0 to 5 mM to glucose. The effects of pH and temperature on the sensing performance were systemati...

Real-time continuous glucose monitoring shows high accuracy within 6 hours after sensor calibration: a prospective study.

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Xiao-Yan Yue

Full Text Available Accurate and timely glucose monitoring is essential in intensive care units. Real-time continuous glucose monitoring system (CGMS has been advocated for many years to improve glycemic management in critically ill patients. In order to determine the effect of calibration time on the accuracy of CGMS, real-time subcutaneous CGMS was used in 18 critically ill patients. CGMS sensor was calibrated with blood glucose measurements by blood gas/glucose analyzer every 12 hours. Venous blood was sampled every 2 to 4 hours, and glucose concentration was measured by standard central laboratory device (CLD and by blood gas/glucose analyzer. With CLD measurement as reference, relative absolute difference (mean±SD in CGMS and blood gas/glucose analyzer were 14.4%±12.2% and 6.5%±6.2%, respectively. The percentage of matched points in Clarke error grid zone A was 74.8% in CGMS, and 98.4% in blood gas/glucose analyzer. The relative absolute difference of CGMS obtained within 6 hours after sensor calibration (8.8%±7.2% was significantly less than that between 6 to 12 hours after calibration (20.1%±13.5%, p<0.0001. The percentage of matched points in Clarke error grid zone A was also significantly higher in data sets within 6 hours after calibration (92.4% versus 57.1%, p<0.0001. In conclusion, real-time subcutaneous CGMS is accurate in glucose monitoring in critically ill patients. CGMS sensor should be calibrated less than 6 hours, no matter what time interval recommended by manufacturer.

Aluminum gallium nitride (GaN)/GaN high electron mobility transistor-based sensors for glucose detection in exhaled breath condensate.

Science.gov (United States)

Chu, Byung Hwan; Kang, Byoung Sam; Hung, Sheng Chun; Chen, Ke Hung; Ren, Fan; Sciullo, Andrew; Gila, Brent P; Pearton, Stephen J

2010-01-01

Immobilized aluminum gallium nitride (AlGaN)/GaN high electron mobility transistors (HEMTs) have shown great potential in the areas of pH, chloride ion, and glucose detection in exhaled breath condensate (EBC). HEMT sensors can be integrated into a wireless data transmission system that allows for remote monitoring. This technology offers the possibility of using AlGaN/GaN HEMTs for extended investigations of airway pathology of detecting glucose in EBC without the need for clinical visits. HEMT structures, consisting of a 3-microm-thick undoped GaN buffer, 30-A-thick Al(0.3)Ga(0.7)N spacer, and 220-A-thick silicon-doped Al(0.3)Ga(0.7)N cap layer, were used for fabricating the HEMT sensors. The gate area of the pH, chloride ion, and glucose detection was immobilized with scandium oxide (Sc(2)O(3)), silver chloride (AgCl) thin film, and zinc oxide (ZnO) nanorods, respectively. The Sc(2)O(3)-gated sensor could detect the pH of solutions ranging from 3 to 10 with a resolution of approximately 0.1 pH. A chloride ion detection limit of 10(-8) M was achieved with a HEMT sensor immobilized with the AgCl thin film. The drain-source current of the ZnO nanorod-gated AlGaN/GaN HEMT sensor immobilized with glucose oxidase showed a rapid response of less than 5 seconds when the sensor was exposed to the target glucose in a buffer with a pH value of 7.4. The sensor could detect a wide range of concentrations from 0.5 nM to 125 microM. There is great promise for using HEMT-based sensors to enhance the detection sensitivity for glucose detection in EBC. Depending on the immobilized material, HEMT-based sensors can be used for sensing different materials. These electronic detection approaches with rapid response and good repeatability show potential for the investigation of airway pathology. The devices can also be integrated into a wireless data transmission system for remote monitoring applications. This sensor technology could use the exhaled breath condensate to measure the

Optical detection of glucose and glycated hemoglobin using etched fiber Bragg gratings coated with functionalized reduced graphene oxide.

Science.gov (United States)

Sridevi, S; Vasu, K S; Sampath, S; Asokan, S; Sood, A K

2016-07-01

An enhanced optical detection of D-glucose and glycated hemoglobin (HbA1c ) has been established in this study using etched fiber Bragg gratings (eFBG) coated with aminophenylboronic acid (APBA)-functionalized reduced graphene oxide (RGO). The read out, namely the shift in Bragg wavelength (ΔλB ) is highly sensitive to changes that occur due to the adsorption of glucose (or HbA1c ) molecules on the eFBG sensor coated with APBA-RGO complex through a five-membered cyclic ester bond formation between glucose and APBA molecules. A limit of detection of 1 nM is achieved with a linear range of detection from 1 nM to 10 mM in the case of D-glucose detection experiments. For HbA1c , a linear range of detection varying from 86 nM to 0.23 mM is achieved. The observation of only 4 pm (picometer) change in ΔλB even for the 10 mM lactose solution confirms the specificity of the APBA-RGO complex coated eFBG sensors to glucose molecules. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nonenzymatic flexible field-effect transistor based glucose sensor fabricated using NiO quantum dots modified ZnO nanorods.

Science.gov (United States)

Jung, Da-Un-Jin; Ahmad, Rafiq; Hahn, Yoon-Bong

2018-02-15

Herein, we fabricated nonenzymatic flexible field-effect transistor (f-FET) based glucose sensor using nickel oxide quantum dots (NiO QDs) modified zinc oxide nanorods (ZnO NRs). The ZnO NRs surfaces were coated with NiO QDs using radio frequency (RF) magnetron sputtering to enhance the electrocatalytic feature and the surface area of ZnO NRs. Under physiological conditions (pH 7.4), the nonenzymatic f-FET glucose sensor shows two linear ranges of 0.001-10mM and 10-50mM with the high sensitivity of 13.14μAcm -2 mM -1 and 7.31μAcm -2 mM -1 , respectively, along with good selectivity, stability and repeatability during glucose detection. The examination of human whole blood and serum samples reveal that the nonenzymatic f-FET based glucose sensor is capable of measuring glucose concentration efficiently in the presence of interfering species and thus can be offered as a promising device for further applications in clinical and non-clinical fields. Copyright © 2017 Elsevier Inc. All rights reserved.

Autoregressive Modeling of Drift and Random Error to Characterize a Continuous Intravascular Glucose Monitoring Sensor.

Science.gov (United States)

Zhou, Tony; Dickson, Jennifer L; Geoffrey Chase, J

2018-01-01

Continuous glucose monitoring (CGM) devices have been effective in managing diabetes and offer potential benefits for use in the intensive care unit (ICU). Use of CGM devices in the ICU has been limited, primarily due to the higher point accuracy errors over currently used traditional intermittent blood glucose (BG) measures. General models of CGM errors, including drift and random errors, are lacking, but would enable better design of protocols to utilize these devices. This article presents an autoregressive (AR) based modeling method that separately characterizes the drift and random noise of the GlySure CGM sensor (GlySure Limited, Oxfordshire, UK). Clinical sensor data (n = 33) and reference measurements were used to generate 2 AR models to describe sensor drift and noise. These models were used to generate 100 Monte Carlo simulations based on reference blood glucose measurements. These were then compared to the original CGM clinical data using mean absolute relative difference (MARD) and a Trend Compass. The point accuracy MARD was very similar between simulated and clinical data (9.6% vs 9.9%). A Trend Compass was used to assess trend accuracy, and found simulated and clinical sensor profiles were similar (simulated trend index 11.4° vs clinical trend index 10.9°). The model and method accurately represents cohort sensor behavior over patients, providing a general modeling approach to any such sensor by separately characterizing each type of error that can arise in the data. Overall, it enables better protocol design based on accurate expected CGM sensor behavior, as well as enabling the analysis of what level of each type of sensor error would be necessary to obtain desired glycemic control safety and performance with a given protocol.

A glucose-responsive pH-switchable bioelectrocatalytic sensor based on phenylboronic acid-diol specificity

International Nuclear Information System (INIS)

Gao, Peiyi; Wang, Zhihua; Yang, Lele; Ma, Tengfei; Yang, Ling; Guo, Qianqiong; Huang, Shasheng

2015-01-01

Graphical abstract: A pH-switchable bioelectrocatayltic sensor was developed, which exhibited an obvious anodic current in acidic conditions as “ON” state, yet a prohibited signal in alkaline conditions as “OFF” state. With the change of pH and/or the presence of glucose, our proposed biosensor produced the corresponding amplified signal, providing a better sensitivity. - Abstract: Aminophenylboronic acid moieties were covalently grafted onto mercaptobenzoic acid moieties, and glucose oxidase was then immobilized through boronic acid-diol specific recognition to form a pH-sensitive electrosensor switching between pH 5.8 and pH 8.0 base solution. Using potassium ferricyanide as electroactive probe, the response was intensified in acidic condition while hindered in alkaline condition. The sharp and stable contrast in current was performed alternately upon the change of pH like a “pH switch”. In the presence of glucose, the response to glucose was further amplified catalytically by glucose oxidase on “ON” state, while electron transfer was inhibited on “OFF” state. Furthermore, when our sensor was on “ON” state, it showed a good linearity ranging from 0 to 30 μmol L −1 of glucose, with a detection limit of 348 nmol L −1 (S/B = 3) and a dynamic range extending to 50 μmol L −1 . Glucose-responsive, pH-switchable and catalytically-amplified, our biosensor provided a new method for the detection of glucose in the form of pH switch in human serum sample, and was promising to more complicated environment

Nanomaterial-based Electrochemical Sensors for the Detection of Glucose and Cholesterol

Science.gov (United States)

Ahmadalinezhad, Asieh

Electrochemical detection methods are highly attractive for the monitoring of glucose, cholesterol, cancer, infectious diseases, and biological warfare agents due to their low cost, high sensitivity, functionality despite sample turbidity, easy miniaturization via microfabrication, low power requirements, and a relatively simple control infrastructure. The development of implantable biosensors is laden with great challenges, which include longevity and inherent biocompatibility, coupled with the continuous monitoring of analytes. Deficiencies in any of these areas will necessitate their surgical replacement. In addition, random signals arising from non-specific adsorption events can cause problems in diagnostic assays. Hence, a great deal of effort has been devoted to the specific control of surface structures. Nanotechnology involves the creation and design of structures with at least one dimension that is below 100 nm. The optical, magnetic, and electrical properties of nanostructures may be manipulated by altering their size, shape, and composition. These attributes may facilitate improvements in biocompatibility, sensitivity and the specific attachment of biomaterials. Thus, the central theme of this dissertation pertains to highlighting the critical roles that are played by the morphology and intrinsic properties of nanomaterials when they are applied in the development of electrochemical biosensors. For this PhD project, we initially designed and fabricated a novel amperometric glucose biosensor based on the immobilization of glucose oxidase (GOx) on a Prussian blue modified nanoporous gold surface, which exhibited a rapid response and a low detection limit of 2.5 microM glucose. The sensitivity of the biosensor was found to be very high (177 microA/mM) and the apparent Michaelis--Menten constant was calculated to be 2.1 mM. Our study has demonstrated that nanoporous gold provides an excellent matrix for enzyme immobilization. To adopt these advanced

Non-Enzymatic Glucose Sensor Composed of Carbon-Coated Nano-Zinc Oxide

Directory of Open Access Journals (Sweden)

Ren-Jei Chung

2017-02-01

Full Text Available Nowadays glucose detection is of great importance in the fields of biological, environmental, and clinical analyzes. In this research, we report a zinc oxide (ZnO nanorod powder surface-coated with carbon material for non-enzymatic glucose sensor applications through a hydrothermal process and chemical vapor deposition method. A series of tests, including crystallinity analysis, microstructure observation, and electrochemical property investigations were carried out. For the cyclic voltammetric (CV glucose detection, the low detection limit of 1 mM with a linear range from 0.1 mM to 10 mM was attained. The sensitivity was 2.97 μA/cm2mM, which is the most optimized ever reported. With such good analytical performance from a simple process, it is believed that the nanocomposites composed of ZnO nanorod powder surface-coated with carbon material are promising for the development of cost-effective non-enzymatic electrochemical glucose biosensors with high sensitivity.

Development of a glucose sensor employing quick and easy modification method with mediator for altering electron acceptor preference.

Science.gov (United States)

Hatada, Mika; Loew, Noya; Inose-Takahashi, Yuka; Okuda-Shimazaki, Junko; Tsugawa, Wakako; Mulchandani, Ashok; Sode, Koji

2018-06-01

Enzyme based electrochemical biosensors are divided into three generations according to their type of electron transfer from the cofactors of the enzymes to the electrodes. Although the 3rd generation sensors using direct electron transfer (DET) type enzymes are ideal, the number of enzyme types which possess DET ability is limited. In this study, we report of a glucose sensor using mediator-modified glucose dehydrogenase (GDH), that was fabricated by a new quick-and-easy method using the pre-functionalized amine reactive phenazine ethosulfate (arPES). Thus mediator-modified GDH obtained the ability to transfer electrons to bulky electron acceptors as well as electrodes. The concentration of glucose was successfully measured using electrodes with immobilized PES-modified GDH, without addition of external electron mediators. Therefore, continuous monitoring systems can be developed based on this "2.5th generation" electron transfer principle utilizing quasi-DET. Furthermore, we successfully modified two other diagnostically relevant enzymes, glucoside 3-dehydrogenase and lactate oxidase, with PES. Therefore, various kinds of diagnostic enzymes can achieve quasi-DET ability simply by modification with arPES, suggesting that continuous monitoring systems based on the 2.5th generation principle can be developed for various target molecules. Copyright © 2018 Elsevier B.V. All rights reserved.

Glucose determination using a re-usable enzyme-modified ion track membrane sensor

Czech Academy of Sciences Publication Activity Database

Fink, Dietmar; Klinkovich, I.; Bukelman, O.; Marks, R.S.; Kiv, A.; Fuks, D.; Fahrner, W. R.; Alfonta, L.

2009-01-01

Roč. 24, č. 8 (2009), s. 2702-2706 ISSN 0956-5663 Institutional research plan: CEZ:AV0Z10480505 Keywords : Glucose sensor * etched tracks * Ion track membranes Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 5.429, year: 2009

Biostable glucose permeable polymer

DEFF Research Database (Denmark)

2017-01-01

A new biostable glucose permeable polymer has been developed which is useful, for example, in implantable glucose sensors. This biostable glucose permeable polymer has a number of advantageous characteristics and, for example, does not undergo hydrolytic cleavage and degradation, thereby providing...... a composition that facilitates long term sensor stability in vivo. The versatile characteristics of this polymer allow it to be used in a variety of contexts, for example to form the body of an implantable glucose sensor. The invention includes the polymer composition, sensor systems formed from this polymer...

Development of an enzyme free glucose sensor based on copper oxide-graphene composite by using green reducing agent ascorbic acid

Science.gov (United States)

Palve, Yogesh Pandit; Jha, Neetu

2018-05-01

In this research work we have developed high sensitive and selective glucose sensor based on copper oxide-graphene composite which is prepared by green synthesis method and used for nonenzymatic glucose sensor. In present paper we report that present method highly selective, simple, efficient, accurate, ecofriendly, less toxic. The prepared composite were characterized by material characterization like SEM, XRD and also by electrochemical characterization like CV, chronoamperometry represents that copper oxide-graphene shows excellent electrocatalytic activity towards glucose, exhibiting a good sensitivity of 103.84 µA mM-1 cm-2, a fast response time 2s, a low detection limit 0.00033µM and linear range from 10 µM-3000 µM. The present sensor can successfully apply for determination of glucose concentration in human blood sample.

A CuNi/C Nanosheet Array Based on a Metal-Organic Framework Derivate as a Supersensitive Non-Enzymatic Glucose Sensor

Science.gov (United States)

Zhang, Li; Ye, Chen; Li, Xu; Ding, Yaru; Liang, Hongbo; Zhao, Guangyu; Wang, Yan

2018-06-01

Bimetal catalysts are good alternatives for non-enzymatic glucose sensors owing to their low cost, high activity, good conductivity, and ease of fabrication. In the present study, a self-supported CuNi/C electrode prepared by electrodepositing Cu nanoparticles on a Ni-based metal-organic framework (MOF) derivate was used as a non-enzymatic glucose sensor. The porous construction and carbon scaffold inherited from the Ni-MOF guarantee good kinetics of the electrode process in electrochemical glucose detection. Furthermore, Cu nanoparticles disturb the array structure of MOF derived films and evidently enhance their electrochemical performances in glucose detection. Electrochemical measurements indicate that the CuNi/C electrode possesses a high sensitivity of 17.12 mA mM-1 cm-2, a low detection limit of 66.67 nM, and a wider linearity range from 0.20 to 2.72 mM. Additionally, the electrode exhibits good reusability, reproducibility, and stability, thereby catering to the practical use of glucose sensors. Similar values of glucose concentrations in human blood serum samples are detected with our electrode and with the method involving glucose-6-phosphate dehydrogenase; the results further demonstrate the practical feasibility of our electrode.

Glucose Sensor MdHXK1 Phosphorylates and Stabilizes MdbHLH3 to Promote Anthocyanin Biosynthesis in Apple

Science.gov (United States)

Hu, Da-Gang; Zhang, Quan-Yan; An, Jian-Ping; You, Chun-Xiang; Hao, Yu-Jin

2016-01-01

Glucose induces anthocyanin accumulation in many plant species; however, the molecular mechanism involved in this process remains largely unknown. Here, we found that apple hexokinase MdHXK1, a glucose sensor, was involved in sensing exogenous glucose and regulating anthocyanin biosynthesis. In vitro and in vivo assays suggested that MdHXK1 interacted directly with and phosphorylated an anthocyanin-associated bHLH transcription factor (TF) MdbHLH3 at its Ser361 site in response to glucose. Furthermore, both the hexokinase_2 domain and signal peptide are crucial for the MdHXK1-mediated phosphorylation of MdbHLH3. Moreover, phosphorylation modification stabilized MdbHLH3 protein and enhanced its transcription of the anthocyanin biosynthesis genes, thereby increasing anthocyanin biosynthesis. Finally, a series of transgenic analyses in apple calli and fruits demonstrated that MdHXK1 controlled glucose-induced anthocyanin accumulation at least partially, if not completely, via regulating MdbHLH3. Overall, our findings provide new insights into the mechanism of the glucose sensor HXK1 modulation of anthocyanin accumulation, which occur by directly regulating the anthocyanin-related bHLH TFs in response to a glucose signal in plants. PMID:27560976

Glucose Sensor MdHXK1 Phosphorylates and Stabilizes MdbHLH3 to Promote Anthocyanin Biosynthesis in Apple.

Directory of Open Access Journals (Sweden)

Da-Gang Hu

2016-08-01

Full Text Available Glucose induces anthocyanin accumulation in many plant species; however, the molecular mechanism involved in this process remains largely unknown. Here, we found that apple hexokinase MdHXK1, a glucose sensor, was involved in sensing exogenous glucose and regulating anthocyanin biosynthesis. In vitro and in vivo assays suggested that MdHXK1 interacted directly with and phosphorylated an anthocyanin-associated bHLH transcription factor (TF MdbHLH3 at its Ser361 site in response to glucose. Furthermore, both the hexokinase_2 domain and signal peptide are crucial for the MdHXK1-mediated phosphorylation of MdbHLH3. Moreover, phosphorylation modification stabilized MdbHLH3 protein and enhanced its transcription of the anthocyanin biosynthesis genes, thereby increasing anthocyanin biosynthesis. Finally, a series of transgenic analyses in apple calli and fruits demonstrated that MdHXK1 controlled glucose-induced anthocyanin accumulation at least partially, if not completely, via regulating MdbHLH3. Overall, our findings provide new insights into the mechanism of the glucose sensor HXK1 modulation of anthocyanin accumulation, which occur by directly regulating the anthocyanin-related bHLH TFs in response to a glucose signal in plants.

Multi-function microfluidic platform for sensor integration

DEFF Research Database (Denmark)

Fernandes, Ana C.; Semenova, Daria; Panjan, Peter

2018-01-01

The limited availability of metabolite-specific sensors for continuous sampling and monitoring is one of the main bottlenecks contributing to failures in bioprocess development. Furthermore, only a limited number of approaches exist to connect currently available measurement systems with high...... throughput reactor units. This is especially relevant in the biocatalyst screening and characterization stage of process development. In this work, a strategy for sensor integration in microfluidic platforms is demonstrated, to address the need for rapid, cost-effective and high-throughput screening...... of the sample solution up to 10 times. In order to highlight the features of the proposed platform, inline monitoring of glucose levels is presented and discussed. Glucose was chosen due to its importance in biotechnology as a relevant substrate. The platform demonstrated continuous measurement of substrate...

A high performance non-enzymatic glucose sensor based on nickel hydroxide modified nitrogen-incorporated nanodiamonds.

Science.gov (United States)

Ko, Chih-Yu; Huang, Jin-Hua; Raina, Supil; Kang, Weng P

2013-06-07

A highly selective, sensitive, and stable non-enzymatic glucose sensor based on Ni hydroxide modified nitrogen-incorporated nanodiamonds (Ni(OH)2-NND) was developed. The sensor was fabricated by e-beam evaporation of a thin Ni film on NND followed by the growth of Ni(OH)2 using an electrochemical process. It was found that the Ni film thickness greatly affects the morphology and electro-catalytic activity of the as-synthesized electrode for non-enzymatic glucose oxidation. Owing to its nanostructure characteristics, the best sensor fabricated by 150 nm Ni deposition showed two wide response ranges, namely, 0.02-1 mM and 1-9 mM, with sensitivities of 3.20 and 1.41 mA mM(-1) cm(-2), respectively, and a detection limit of 1.2 μM (S/N = 3). The sensor also showed good long-term stability as well as high selectivity in the presence of interferences such as ascorbic acid, acetaminophen, and uric acid. This finding reveals the possibility of exploiting the NND as an electrochemical biosensor platform where high performance addressable sensor arrays could be built.

Glucose-induced effects and joker function of glucose: endocrine or genotoxic prevalence?

Science.gov (United States)

Berstein, L M; Vasilyev, D A; Poroshina, T E; Kovalenko, I G

2006-10-01

The steady increase in chronic "glycemic load" is characteristic for modern times. Among myriad of glucose functions, two principals can be emphasized: first, endocrine (in particular, ability to induce insulin secretion) and second, DNA-damaging related to formation of reactive oxygen species (ROS). It was suggested by us earlier that a shift in the ratio of mentioned functions reflects a possible "joker" role of glucose as an important modifier of human pathology. Therefore, we embarked on a study to investigate an individual effect of peroral glucose challenge on serum insulin level and ROS generation by mononuclears (luminol-dependent/latex-induced chemiluminescence) in 20 healthy people aged between 28-75. Concentrations of glucose, blood lipids, carbonylated proteins, malondialdehyde, leptin and TNF-alpha were determined as well. On the basis of received data two separate groups could be distinguished: one (n=8), in which glucose stimulation of ROS generation by mononuclears was increased and relatively prevailed over induction of insulin secretion (state of the so called glucose-induced genotoxicity, GIGT), and another (n=12), in which signs of GIGT were not revealed. People who belonged to the first group were characterized with a tendency to lower body mass index, blood leptin and cholesterol and to higher TNF-alpha concentration. Thus, if joker function of glucose is realized in "genotoxic mode", the phenotype (and probably genotype) of subjects may be rather distinctive to the one discovered in glucose-induced "endocrine prevalence". Whether such changes may serve as a pro-mutagenic or pro-endocrine basis for the rise of different chronic diseases or, rather, different features/aggressiveness of the same disease warrants further study.

The glucose enzyme electrode: is simple peroxide detection at a needle sensor acceptable?

Science.gov (United States)

Vadgama, P; Mullen, W; Churchouse, S; Battersby, C

1988-01-01

Needle type devices have been fabricated based on Pt anodes (to detect H2O2) mounted with stainless steel needles to act as the reference. Coating of these devices with glucose oxidase allowed glucose measurement, but with high dependence on stirring and background pO2 levels as well as a restricted glucose assay range. By wet dipcoating of microporous polyurethane or the application of preformed porous membranes, the linear range has been extended up to 70 mM glucose, to give minimal pO2 dependence and insensitivity to stirring. With incorporation of polyethersulphone membranes, blood measurement was possible with high selectivity (y = 0.954x + 0.202, r = 0.991, n = 48). This establishes that simple peroxide detection at a needle sensor is acceptable, and can now be focussed on increasing biocompatibility.

Fabrication of a Microneedle/CNT Hierarchical Micro/Nano Surface Electrochemical Sensor and Its In-Vitro Glucose Sensing Characterization

Directory of Open Access Journals (Sweden)

Youngsam Yoon

2013-12-01

Full Text Available We report fabrication of a microneedle-based three-electrode integrated electrochemical sensor and in-vitro characterization of this sensor for glucose sensing applications. A piece of silicon was sequentially dry and wet etched to form a 15 × 15 array of tall (approximately 380 µm sharp silicon microneedles. Iron catalyst was deposited through a SU-8 shadow mask to form the working electrode and counter electrode. A multi-walled carbon nanotube forest was grown directly on the silicon microneedle array and platinum nano-particles were electrodeposited. Silver was deposited on the Si microneedle array through another shadow mask and chlorinated to form a Ag/AgCl reference electrode. The 3-electrode electrochemical sensor was tested for various glucose concentrations in the range of 3~20 mM in 0.01 M phosphate buffered saline (PBS solution. The sensor’s amperometric response to the glucose concentration is linear and its sensitivity was found to be 17.73 ± 3 μA/mM-cm2. This microneedle-based sensor has a potential to be used for painless diabetes testing applications.

Glucose Sensing

CERN Document Server

Geddes, Chris D

2006-01-01

Topics in Fluorescence Spectroscopy, Glucose Sensing is the eleventh volume in the popular series Topics in Fluorescence Spectroscopy, edited by Drs. Chris D. Geddes and Joseph R. Lakowicz. This volume incorporates authoritative analytical fluorescence-based glucose sensing reviews specialized enough to be attractive to professional researchers, yet also appealing to the wider audience of scientists in related disciplines of fluorescence. Glucose Sensing is an essential reference for any lab working in the analytical fluorescence glucose sensing field. All academics, bench scientists, and industry professionals wishing to take advantage of the latest and greatest in the continuously emerging field of glucose sensing, and diabetes care & management, will find this volume an invaluable resource. Topics in Fluorescence Spectroscopy Volume 11, Glucose Sensing Chapters include: Implantable Sensors for Interstitial Fluid Smart Tattoo Glucose Sensors Optical Enzyme-based Glucose Biosensors Plasmonic Glucose Sens...

Time-domain fiber loop ringdown sensor and sensor network

Science.gov (United States)

Kaya, Malik

Optical fibers have been mostly used in fiber optic communications, imaging optics, sensing technology, etc. Fiber optic sensors have gained increasing attention for scientific and structural health monitoring (SHM) applications. In this study, fiber loop ringdown (FLRD) sensors were fabricated for scientific, SHM, and sensor networking applications. FLRD biosensors were fabricated for both bulk refractive index (RI)- and surface RI-based DNA sensing and one type of bacteria sensing. Furthermore, the effect of glucose oxidase (GOD) immobilization at the sensor head on sensor performance was evaluated for both glucose and synthetic urine solutions with glucose concentration between 0.1% and 10%. Detection sensitivities of the glucose sensors were achieved as low as 0.05%. For chemical sensing, heavy water, ranging from 97% to 10%, and several elemental solutions were monitored by using the FLRD chemical sensors. Bulk index-based FLRD sensing showed that trace elements can be detected in deionized water. For physical sensing, water and cracking sensors were fabricated and embedded into concrete. A partially-etched single-mode fiber (SMF) was embedded into a concrete bar for water monitoring while a bare SMF without any treatment was directly embedded into another concrete bar for monitoring cracks. Furthermore, detection sensitivities of water and crack sensors were investigated as 10 ml water and 0.5 mm surface crack width, respectively. Additionally fiber loop ringdown-fiber Bragg grating temperature sensors were developed in the laboratory; two sensor units for water, crack, and temperature sensing were deployed into a concrete cube in a US Department of Energy test bed (Miami, FL). Multi-sensor applications in a real concrete structure were accomplished by testing the six FLRD sensors. As a final stage, a sensor network was assembled by multiplexing two or three FLRD sensors in series and parallel. Additionally, two FLRD sensors were combined in series and

Layer-by-layer assembly of functionalized reduced graphene oxide for direct electrochemistry and glucose detection

Energy Technology Data Exchange (ETDEWEB)

Mascagni, Daniela Branco Tavares [São Paulo State University - UNESP, Sorocaba, São Paulo (Brazil); Miyazaki, Celina Massumi [Federal University of São Carlos, UFSCar, Campus Sorocaba, SP (Brazil); Cruz, Nilson Cristino da [São Paulo State University - UNESP, Sorocaba, São Paulo (Brazil); Leite de Moraes, Marli [Federal University of São Paulo, Unifesp, Campus São José dos Campos, SP (Brazil); Riul, Antonio [University of Campinas - Unicamp, Campinas, São Paulo (Brazil); Ferreira, Marystela, E-mail: marystela@ufscar.br [Federal University of São Carlos, UFSCar, Campus Sorocaba, SP (Brazil)

2016-11-01

We report an electrochemical glucose biosensor made with layer-by-layer (LbL) films of functionalized reduced graphene oxide (rGO) and glucose oxidase (GOx). The LbL assembly using positively and negatively charged rGO multilayers represents a simple approach to develop enzymatic biosensors. The electron transport properties of graphene were combined with the specificity provided by the enzyme. rGO was obtained and functionalized using chemical methods, being positively charged with poly(diallyldimethylammonium chloride) to form GPDDA, and negatively charged with poly(styrene sulfonate) to form GPSS. Stable aqueous dispersions of GPDDA and GPSS are easily obtained, enabling the growth of LbL films on various solid supports. The use of graphene in the immobilization of GOx promoted Direct Electron Transfer, which was evaluated by Cyclic Voltammetry. Amperometric measurements indicated a detection limit of 13.4 μmol·L{sup ‐1} and sensitivity of 2.47 μA·cm{sup −2}·mmol{sup −1}·L for glucose with the (GPDDA/GPSS){sub 1}/(GPDDA/GOx){sub 2} architecture, whose thickness was 19.80 ± 0.28 nm, as determined by Surface Plasmon Resonance (SPR). The sensor may be useful for clinical analysis since glucose could be detected even in the presence of typical interfering agents and in real samples of a lactose-free milk and an electrolyte solution to prevent dehydration. - Highlights: • Direct electrochemistry of glucose oxidase at functionalized reduced graphene oxide. • Thickness (layer-by-layer) LbL film determined by Surface Plasmon Resonance (SPR). • Selective determination of glucose in the presence of several interferents. • Real sample test: commercial oral electrolyte solution and lactose-free milk.

Layer-by-layer assembly of functionalized reduced graphene oxide for direct electrochemistry and glucose detection

International Nuclear Information System (INIS)

Mascagni, Daniela Branco Tavares; Miyazaki, Celina Massumi; Cruz, Nilson Cristino da; Leite de Moraes, Marli; Riul, Antonio; Ferreira, Marystela

2016-01-01

We report an electrochemical glucose biosensor made with layer-by-layer (LbL) films of functionalized reduced graphene oxide (rGO) and glucose oxidase (GOx). The LbL assembly using positively and negatively charged rGO multilayers represents a simple approach to develop enzymatic biosensors. The electron transport properties of graphene were combined with the specificity provided by the enzyme. rGO was obtained and functionalized using chemical methods, being positively charged with poly(diallyldimethylammonium chloride) to form GPDDA, and negatively charged with poly(styrene sulfonate) to form GPSS. Stable aqueous dispersions of GPDDA and GPSS are easily obtained, enabling the growth of LbL films on various solid supports. The use of graphene in the immobilization of GOx promoted Direct Electron Transfer, which was evaluated by Cyclic Voltammetry. Amperometric measurements indicated a detection limit of 13.4 μmol·L ‐1 and sensitivity of 2.47 μA·cm −2 ·mmol −1 ·L for glucose with the (GPDDA/GPSS) 1 /(GPDDA/GOx) 2 architecture, whose thickness was 19.80 ± 0.28 nm, as determined by Surface Plasmon Resonance (SPR). The sensor may be useful for clinical analysis since glucose could be detected even in the presence of typical interfering agents and in real samples of a lactose-free milk and an electrolyte solution to prevent dehydration. - Highlights: • Direct electrochemistry of glucose oxidase at functionalized reduced graphene oxide. • Thickness (layer-by-layer) LbL film determined by Surface Plasmon Resonance (SPR). • Selective determination of glucose in the presence of several interferents. • Real sample test: commercial oral electrolyte solution and lactose-free milk.

Glucose oxidase-functionalized fluorescent gold nanoclusters as probes for glucose

International Nuclear Information System (INIS)

Xia, Xiaodong; Long, Yunfei; Wang, Jianxiu

2013-01-01

Highlights: ► A glucose oxidase/gold nanocluster conjugates formed by etching chemistry. ► Integration of the bioactivities and fluorescence properties within a single unit. ► These conjugates serve as novel fluorescent probe for glucose. -- Abstract: Creation and application of noble metal nanoclusters have received continuous attention. By integrating enzyme activity and fluorescence for potential applications, enzyme-capped metal clusters are more desirable. This work demonstrated a glucose oxidase (an enzyme for glucose)-functionalized gold cluster as probe for glucose. Under physiological conditions, such bioconjugate was successfully prepared by an etching reaction, where tetrakis (hydroxylmethyl) phosphonium-protected gold nanoparticle and thioctic acid-modified glucose oxidase were used as precursor and etchant, respectively. These bioconjugates showed unique fluorescence spectra (λ em max = 650 nm, λ ex max = 507 nm) with an acceptable quantum yield (ca. 7%). Moreover, the conjugated glucose oxidase remained active and catalyzed reaction of glucose and dissolved O 2 to produce H 2 O 2 , which quenched quantitatively the fluorescence of gold clusters and laid a foundation of glucose detection. A linear range of 2.0 × 10 −6 –140 × 10 −6 M and a detection limit of 0.7 × 10 −6 M (S/N = 3) were obtained. Also, another horseradish peroxidase/gold cluster bioconjugate was produced by such general synthesis method. Such enzyme/metal cluster bioconjugates represented a promising class of biosensors for biologically important targets in organelles or cells

Neuronal calcium sensor synaptotagmin-9 is not involved in the regulation of glucose homeostasis or insulin secretion.

Directory of Open Access Journals (Sweden)

Natalia Gustavsson

Full Text Available BACKGROUND: Insulin secretion is a complex and highly regulated process. It is well established that cytoplasmic calcium is a key regulator of insulin secretion, but how elevated intracellular calcium triggers insulin granule exocytosis remains unclear, and we have only begun to define the identities of proteins that are responsible for sensing calcium changes and for transmitting the calcium signal to release machineries. Synaptotagmins are primarily expressed in brain and endocrine cells and exhibit diverse calcium binding properties. Synaptotagmin-1, -2 and -9 are calcium sensors for fast neurotransmitter release in respective brain regions, while synaptotagmin-7 is a positive regulator of calcium-dependent insulin release. Unlike the three neuronal calcium sensors, whose deletion abolished fast neurotransmitter release, synaptotagmin-7 deletion resulted in only partial loss of calcium-dependent insulin secretion, thus suggesting that other calcium-sensors must participate in the regulation of insulin secretion. Of the other synaptotagmin isoforms that are present in pancreatic islets, the neuronal calcium sensor synaptotagmin-9 is expressed at the highest level after synaptotagmin-7. METHODOLOGY/PRINCIPAL FINDINGS: In this study we tested whether synaptotagmin-9 participates in the regulation of glucose-stimulated insulin release by using pancreas-specific synaptotagmin-9 knockout (p-S9X mice. Deletion of synaptotagmin-9 in the pancreas resulted in no changes in glucose homeostasis or body weight. Glucose tolerance, and insulin secretion in vivo and from isolated islets were not affected in the p-S9X mice. Single-cell capacitance measurements showed no difference in insulin granule exocytosis between p-S9X and control mice. CONCLUSIONS: Thus, synaptotagmin-9, although a major calcium sensor in the brain, is not involved in the regulation of glucose-stimulated insulin release from pancreatic β-cells.

Neuronal calcium sensor synaptotagmin-9 is not involved in the regulation of glucose homeostasis or insulin secretion.

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Gustavsson, Natalia; Wang, Xiaorui; Wang, Yue; Seah, Tingting; Xu, Jun; Radda, George K; Südhof, Thomas C; Han, Weiping

2010-11-09

Insulin secretion is a complex and highly regulated process. It is well established that cytoplasmic calcium is a key regulator of insulin secretion, but how elevated intracellular calcium triggers insulin granule exocytosis remains unclear, and we have only begun to define the identities of proteins that are responsible for sensing calcium changes and for transmitting the calcium signal to release machineries. Synaptotagmins are primarily expressed in brain and endocrine cells and exhibit diverse calcium binding properties. Synaptotagmin-1, -2 and -9 are calcium sensors for fast neurotransmitter release in respective brain regions, while synaptotagmin-7 is a positive regulator of calcium-dependent insulin release. Unlike the three neuronal calcium sensors, whose deletion abolished fast neurotransmitter release, synaptotagmin-7 deletion resulted in only partial loss of calcium-dependent insulin secretion, thus suggesting that other calcium-sensors must participate in the regulation of insulin secretion. Of the other synaptotagmin isoforms that are present in pancreatic islets, the neuronal calcium sensor synaptotagmin-9 is expressed at the highest level after synaptotagmin-7. In this study we tested whether synaptotagmin-9 participates in the regulation of glucose-stimulated insulin release by using pancreas-specific synaptotagmin-9 knockout (p-S9X) mice. Deletion of synaptotagmin-9 in the pancreas resulted in no changes in glucose homeostasis or body weight. Glucose tolerance, and insulin secretion in vivo and from isolated islets were not affected in the p-S9X mice. Single-cell capacitance measurements showed no difference in insulin granule exocytosis between p-S9X and control mice. Thus, synaptotagmin-9, although a major calcium sensor in the brain, is not involved in the regulation of glucose-stimulated insulin release from pancreatic β-cells.

Phosphomolybdic acid functionalized graphene loading copper nanoparticles modified electrodes for non-enzymatic electrochemical sensing of glucose

Energy Technology Data Exchange (ETDEWEB)

Xu, Jiaoyan; Cao, Xiyue [College of Chemistry and Chemical Engineering, Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China); Xia, Jianfei, E-mail: xiajianfei@126.com [College of Chemistry and Chemical Engineering, Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China); Gong, Shida [College of Chemistry and Chemical Engineering, Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China); Wang, Zonghua, E-mail: wangzonghua@qdu.edu.cn [College of Chemistry and Chemical Engineering, Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China); Lu, Lin [College of Chemistry and Chemical Engineering, Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China); Zibo Normal College, Zibo, Shandong 255100 (China)

2016-08-31

A sensitive non-enzymatic glucose electrochemical biosensor (Cu/PMo{sub 12}-GR/GCE) was developed based on the combination of copper nanoparticles (CuNPs) and phosphomolybdic acid functionalized graphene (PMo{sub 12}-GR). PMo{sub 12}-GR films were modified on the surface of glassy carbon electrode (GCE) through electrostatic self-assembly with the aid of poly diallyl dimethyl ammonium chloride (PDDA). Then CuNPs were successfully decorated onto the PMo{sub 12}-GR modified GCE through electrodeposition. The morphology of Cu/PMo{sub 12}-GR/GCE was characterized by scanning electron microscope (SEM). Cyclic voltammetry (CV) and chronoamperometry were used to investigate the electrochemical performances of the biosensor. The results indicated that the modified electrode displayed a synergistic effect of PMo{sub 12}-GR sheets and CuNPs towards the electro-oxidation of glucose in the alkaline solution. At the optimal detection potential of 0.50 V, the response towards glucose presented a linear response ranging from 0.10 μM to 1.0 mM with a detection limit of 3.0 × 10{sup −2} μM (S/N = 3). In addition, Cu/PMo{sub 12}-GR/GCE possessed a high selectivity, good reproducibility, excellent stability and acceptable recovery, which indicating the potential application in clinical field. - Highlights: • Cu/PMo{sub 12}-GR/GCE as a non-enzymatic glucose electrochemical sensor. • PMo{sub 12} is efficient for the uniform growth of Cu-NPs and electron transport. • The sensor exhibits good sensitivity and specificity towards glucose.

Hybrid online sensor error detection and functional redundancy for systems with time-varying parameters.

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Feng, Jianyuan; Turksoy, Kamuran; Samadi, Sediqeh; Hajizadeh, Iman; Littlejohn, Elizabeth; Cinar, Ali

2017-12-01

Supervision and control systems rely on signals from sensors to receive information to monitor the operation of a system and adjust manipulated variables to achieve the control objective. However, sensor performance is often limited by their working conditions and sensors may also be subjected to interference by other devices. Many different types of sensor errors such as outliers, missing values, drifts and corruption with noise may occur during process operation. A hybrid online sensor error detection and functional redundancy system is developed to detect errors in online signals, and replace erroneous or missing values detected with model-based estimates. The proposed hybrid system relies on two techniques, an outlier-robust Kalman filter (ORKF) and a locally-weighted partial least squares (LW-PLS) regression model, which leverage the advantages of automatic measurement error elimination with ORKF and data-driven prediction with LW-PLS. The system includes a nominal angle analysis (NAA) method to distinguish between signal faults and large changes in sensor values caused by real dynamic changes in process operation. The performance of the system is illustrated with clinical data continuous glucose monitoring (CGM) sensors from people with type 1 diabetes. More than 50,000 CGM sensor errors were added to original CGM signals from 25 clinical experiments, then the performance of error detection and functional redundancy algorithms were analyzed. The results indicate that the proposed system can successfully detect most of the erroneous signals and substitute them with reasonable estimated values computed by functional redundancy system.

Design of nanostructured-based glucose biosensors

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Komirisetty, Archana; Williams, Frances; Pradhan, Aswini; Konda, Rajini B.; Dondapati, Hareesh; Samantaray, Diptirani

2012-04-01

This paper presents the design of glucose sensors that will be integrated with advanced nano-materials, bio-coatings and electronics to create novel devices that are highly sensitive, inexpensive, accurate, and reliable. In the work presented, a glucose biosensor and its fabrication process flow have been designed. The device is based on electrochemical sensing using a working electrode with bio-functionalized zinc oxide (ZnO) nano-rods. Among all metal oxide nanostructures, ZnO nano-materials play a significant role as a sensing element in biosensors due to their properties such as high isoelectric point (IEP), fast electron transfer, non-toxicity, biocompatibility, and chemical stability which are very crucial parameters to achieve high sensitivity. Amperometric enzyme electrodes based on glucose oxidase (GOx) are used due to their stability and high selectivity to glucose. The device also consists of silicon dioxide and titanium layers as well as platinum working and counter electrodes and a silver/silver chloride reference electrode. Currently, the biosensors are being fabricated using the process flow developed. Once completed, the sensors will be bio-functionalized and tested to characterize their performance, including their sensitivity and stability.

Multi-function microfluidic platform for sensor integration.

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Fernandes, Ana C; Semenova, Daria; Panjan, Peter; Sesay, Adama M; Gernaey, Krist V; Krühne, Ulrich

2018-03-06

The limited availability of metabolite-specific sensors for continuous sampling and monitoring is one of the main bottlenecks contributing to failures in bioprocess development. Furthermore, only a limited number of approaches exist to connect currently available measurement systems with high throughput reactor units. This is especially relevant in the biocatalyst screening and characterization stage of process development. In this work, a strategy for sensor integration in microfluidic platforms is demonstrated, to address the need for rapid, cost-effective and high-throughput screening in bioprocesses. This platform is compatible with different sensor formats by enabling their replacement and was built in order to be highly flexible and thus suitable for a wide range of applications. Moreover, this re-usable platform can easily be connected to analytical equipment, such as HPLC, laboratory scale reactors or other microfluidic chips through the use of standardized fittings. In addition, the developed platform includes a two-sensor system interspersed with a mixing channel, which allows the detection of samples that might be outside the first sensor's range of detection, through dilution of the sample solution up to 10 times. In order to highlight the features of the proposed platform, inline monitoring of glucose levels is presented and discussed. Glucose was chosen due to its importance in biotechnology as a relevant substrate. The platform demonstrated continuous measurement of substrate solutions for up to 12 h. Furthermore, the influence of the fluid velocity on substrate diffusion was observed, indicating the need for in-flow calibration to achieve a good quantitative output. Copyright © 2018 Elsevier B.V. All rights reserved.

Regression Methods for Ophthalmic Glucose Sensing Using Metamaterials

Directory of Open Access Journals (Sweden)

Philipp Rapp

2011-01-01

Full Text Available We present a novel concept for in vivo sensing of glucose using metamaterials in combination with automatic learning systems. In detail, we use the plasmonic analogue of electromagnetically induced transparency (EIT as sensor and evaluate the acquired data with support vector machines. The metamaterial can be integrated into a contact lens. This sensor changes its optical properties such as reflectivity upon the ambient glucose concentration, which allows for in situ measurements in the eye. We demonstrate that estimation errors below 2% at physiological concentrations are possible using simulations of the optical properties of the metamaterial in combination with an appropriate electrical circuitry and signal processing scheme. In the future, functionalization of our sensor with hydrogel will allow for a glucose-specific detection which is insensitive to other tear liquid substances providing both excellent selectivity and sensitivity.

Measurement of Non-Invasive Blood Glucose Level Based Sensor Color TCS3200 and Arduino

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Kurniadi Wardana, Humaidillah; Indahwati, Elly; Arifah Fitriyah, Lina

2018-04-01

Design and measurement of Arduino-based urinary (non-invasive) urine glucose using RGB tcs3200 sensor. This research was conducted by making use of the urine in diabetes patients detected by sensor colours then measured levels of colour based on the RGB colour of the urine of diabetics. The detection is done on 4 urine samples with each consisting of 3 diabetics and 1 non-diabetics. Equipment used in this research, among others, Arduino Uno, colour sensor tcs3200, LCD 16x4. The results showed that the detection of RGB values in diabetics 230 with blue and not diabetics 200 with red.

Glucose oxidase-functionalized fluorescent gold nanoclusters as probes for glucose

Energy Technology Data Exchange (ETDEWEB)

Xia, Xiaodong [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201 (China); Long, Yunfei, E-mail: l_yunfei927@163.com [School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201 (China); Wang, Jianxiu, E-mail: jxiuwang@csu.edu.cn [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China)

2013-04-15

Highlights: ► A glucose oxidase/gold nanocluster conjugates formed by etching chemistry. ► Integration of the bioactivities and fluorescence properties within a single unit. ► These conjugates serve as novel fluorescent probe for glucose. -- Abstract: Creation and application of noble metal nanoclusters have received continuous attention. By integrating enzyme activity and fluorescence for potential applications, enzyme-capped metal clusters are more desirable. This work demonstrated a glucose oxidase (an enzyme for glucose)-functionalized gold cluster as probe for glucose. Under physiological conditions, such bioconjugate was successfully prepared by an etching reaction, where tetrakis (hydroxylmethyl) phosphonium-protected gold nanoparticle and thioctic acid-modified glucose oxidase were used as precursor and etchant, respectively. These bioconjugates showed unique fluorescence spectra (λ{sub em} {sub max} = 650 nm, λ{sub ex} {sub max} = 507 nm) with an acceptable quantum yield (ca. 7%). Moreover, the conjugated glucose oxidase remained active and catalyzed reaction of glucose and dissolved O{sub 2} to produce H{sub 2}O{sub 2}, which quenched quantitatively the fluorescence of gold clusters and laid a foundation of glucose detection. A linear range of 2.0 × 10{sup −6}–140 × 10{sup −6} M and a detection limit of 0.7 × 10{sup −6} M (S/N = 3) were obtained. Also, another horseradish peroxidase/gold cluster bioconjugate was produced by such general synthesis method. Such enzyme/metal cluster bioconjugates represented a promising class of biosensors for biologically important targets in organelles or cells.

Optical biosensor optimized for continuous in-line glucose monitoring in animal cell culture.

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Tric, Mircea; Lederle, Mario; Neuner, Lisa; Dolgowjasow, Igor; Wiedemann, Philipp; Wölfl, Stefan; Werner, Tobias

2017-09-01

Biosensors for continuous glucose monitoring in bioreactors could provide a valuable tool for optimizing culture conditions in biotechnological applications. We have developed an optical biosensor for long-term continuous glucose monitoring and demonstrated a tight glucose level control during cell culture in disposable bioreactors. The in-line sensor is based on a commercially available oxygen sensor that is coated with cross-linked glucose oxidase (GOD). The dynamic range of the sensor was tuned by a hydrophilic perforated diffusion membrane with an optimized permeability for glucose and oxygen. The biosensor was thoroughly characterized by experimental data and numerical simulations, which enabled insights into the internal concentration profile of the deactivating by-product hydrogen peroxide. The simulations were carried out with a one-dimensional biosensor model and revealed that, in addition to the internal hydrogen peroxide concentration, the turnover rate of the enzyme GOD plays a crucial role for biosensor stability. In the light of this finding, the glucose sensor was optimized to reach a long functional stability (>52 days) under continuous glucose monitoring conditions with a dynamic range of 0-20 mM and a response time of t 90  ≤ 10 min. In addition, we demonstrated that the sensor was sterilizable with beta and UV irradiation and only subjected to minor cross sensitivity to oxygen, when an oxygen reference sensor was applied. Graphical abstract Measuring setup of a glucose biosensor in a shake flask for continuous glucose monitoring in mammalian cell culture.

Wearable Contact Lens Biosensors for Continuous Glucose Monitoring Using Smartphones.

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Elsherif, Mohamed; Hassan, Mohammed Umair; Yetisen, Ali K; Butt, Haider

2018-05-17

Low-cost, robust, and reusable continuous glucose monitoring systems that can provide quantitative measurements at point-of-care settings is an unmet medical need. Optical glucose sensors require complex and time-consuming fabrication processes, and their readouts are not practical for quantitative analyses. Here, a wearable contact lens optical sensor was created for the continuous quantification of glucose at physiological conditions, simplifying the fabrication process and facilitating smartphone readouts. A photonic microstructure having a periodicity of 1.6 μm was printed on a glucose-selective hydrogel film functionalized with phenylboronic acid. Upon binding with glucose, the microstructure volume swelled, which modulated the periodicity constant. The resulting change in the Bragg diffraction modulated the space between zero- and first-order spots. A correlation was established between the periodicity constant and glucose concentration within 0-50 mM. The sensitivity of the sensor was 12 nm mM -1 , and the saturation response time was less than 30 min. The sensor was integrated with commercial contact lenses and utilized for continuous glucose monitoring using smartphone camera readouts. The reflected power of the first-order diffraction was measured via a smartphone application and correlated to the glucose concentrations. A short response time of 3 s and a saturation time of 4 min was achieved in the continuous monitoring mode. Glucose-sensitive photonic microstructures may have applications in point-of-care continuous monitoring devices and diagnostics at home settings.

Enzymatic glucose sensor based on Au nanoparticle and plant-like ZnO film modified electrode

Energy Technology Data Exchange (ETDEWEB)

Tian, Kun [Nanostructured Materials Research Laboratory, Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112 (United States); Alex, Saji [Nanostructured Materials Research Laboratory, Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112 (United States); Department of Chemistry, Government College for Women, Thiruvananthapuram, Kerala 695014 (India); Siegel, Gene [Nanostructured Materials Research Laboratory, Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112 (United States); Tiwari, Ashutosh, E-mail: tiwari@eng.utah.edu [Nanostructured Materials Research Laboratory, Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112 (United States)

2015-01-01

A novel electrochemical glucose sensor was developed by employing a composite film of plant-like Zinc oxide (ZnO) and chitosan stabilized spherical gold nanoparticles (AuNPs) on which Glucose oxidaze (GOx) was immobilized. The ZnO was deposited on an indium tin oxide (ITO) coated glass and the AuNPs of average diameter of 23 nm were loaded on ZnO as the second layer. The prepared ITO/ZnO/AuNPs/GOx bioelectrode exhibited a low value of Michaelis–Menten constant of 1.70 mM indicating a good bio-matrix for GOx. The studies of electrochemical properties of the electrode using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) showed that, the presence of AuNPs provides significant enhancement of the electron transfer rate during redox reactions. The linear sweep voltammetry (LSV) shows that the ITO/ZnO/AuNPs/GOx based sensor has a high sensitivity of 3.12 μA·mM{sup −1}·cm{sup −2} in the range of 50 mg/dL to 400 mg/dL glucose concentration. The results show promising application of the gold nanoparticle modified plant-like ZnO composite bioelectrode for electrochemical sensing of glucose.

Determination of Glucose Concentration in Yeast Culture Medium

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Hara, Seiichi; Kishimoto, Tomokazu; Muraji, Masafumi; Tsujimoto, Hiroaki; Azuma, Masayuki; Ooshima, Hiroshi

The present paper describes a sensor for measuring the glucose concentration of yeast culture medium. The sensor determines glucose concentration by measuring the yield of hydrogen peroxide produced by glucose oxidase, which is monitored as luminescence using photomultiplier. The present sensor is able to measure low glucose concentration in media in which yeast cells keep respiration state. We herein describe the system and the characteristics of the glucose sensor.

Naked-Eye Detection of Glucose in Saliva with Bienzymatic Paper-Based Sensor

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Luis A. Santana-Jiménez

2018-04-01

Full Text Available The high incidence of Diabetes Mellitus in low-income regions has promoted the development of low-cost alternatives to replace blood-based procedures. In this work, we present a bienzymatic paper-based sensor suitable for the naked-eye detection of glucose in saliva samples. The sensor was obtained by a stamping procedure and modified with chitosan to improve the colorimetric readout. The bienzymatic reaction of GOx-HRP coupled with 2,4,6-tribromo-3-hydroxy benzoic acid was applied for the detection of glucose within a range from 0 to 180 mgdL−1 in buffer and artificial saliva solutions. The visual readout was perceived by the naked eye and registered with an office scanner to evaluate the analytical performance. The results showed a limit of detection of 0.37 mgdL−1 (S/N = 3 with an R.S.D. of 1.69% and a linear range from 1 to 22.5 mgdL−1 with an R2 of 0.99235. The analysis of human saliva samples was performed without pre-processing, achieving recoveries from 92 to 114%. The naked-eye detection was evaluated under two different light settings, showing average recoveries of 108.58 and 90.65% for standard and low illumination. The proposed device showed potential for easy-to-use, sensitive, low-cost, fast, and device-free detection of salivary glucose suitable for untrained personnel operation and limited facilities.

Analytical modeling of glucose biosensors based on carbon nanotubes.

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Pourasl, Ali H; Ahmadi, Mohammad Taghi; Rahmani, Meisam; Chin, Huei Chaeng; Lim, Cheng Siong; Ismail, Razali; Tan, Michael Loong Peng

2014-01-15

In recent years, carbon nanotubes have received widespread attention as promising carbon-based nanoelectronic devices. Due to their exceptional physical, chemical, and electrical properties, namely a high surface-to-volume ratio, their enhanced electron transfer properties, and their high thermal conductivity, carbon nanotubes can be used effectively as electrochemical sensors. The integration of carbon nanotubes with a functional group provides a good and solid support for the immobilization of enzymes. The determination of glucose levels using biosensors, particularly in the medical diagnostics and food industries, is gaining mass appeal. Glucose biosensors detect the glucose molecule by catalyzing glucose to gluconic acid and hydrogen peroxide in the presence of oxygen. This action provides high accuracy and a quick detection rate. In this paper, a single-wall carbon nanotube field-effect transistor biosensor for glucose detection is analytically modeled. In the proposed model, the glucose concentration is presented as a function of gate voltage. Subsequently, the proposed model is compared with existing experimental data. A good consensus between the model and the experimental data is reported. The simulated data demonstrate that the analytical model can be employed with an electrochemical glucose sensor to predict the behavior of the sensing mechanism in biosensors.

Layer-by-layer assembly of functionalized reduced graphene oxide for direct electrochemistry and glucose detection.

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Mascagni, Daniela Branco Tavares; Miyazaki, Celina Massumi; da Cruz, Nilson Cristino; de Moraes, Marli Leite; Riul, Antonio; Ferreira, Marystela

2016-11-01

We report an electrochemical glucose biosensor made with layer-by-layer (LbL) films of functionalized reduced graphene oxide (rGO) and glucose oxidase (GOx). The LbL assembly using positively and negatively charged rGO multilayers represents a simple approach to develop enzymatic biosensors. The electron transport properties of graphene were combined with the specificity provided by the enzyme. rGO was obtained and functionalized using chemical methods, being positively charged with poly(diallyldimethylammonium chloride) to form GPDDA, and negatively charged with poly(styrene sulfonate) to form GPSS. Stable aqueous dispersions of GPDDA and GPSS are easily obtained, enabling the growth of LbL films on various solid supports. The use of graphene in the immobilization of GOx promoted Direct Electron Transfer, which was evaluated by Cyclic Voltammetry. Amperometric measurements indicated a detection limit of 13.4μmol·L(-1) and sensitivity of 2.47μA·cm(-2)·mmol(-1)·L for glucose with the (GPDDA/GPSS)1/(GPDDA/GOx)2 architecture, whose thickness was 19.80±0.28nm, as determined by Surface Plasmon Resonance (SPR). The sensor may be useful for clinical analysis since glucose could be detected even in the presence of typical interfering agents and in real samples of a lactose-free milk and an electrolyte solution to prevent dehydration. Copyright © 2016 Elsevier B.V. All rights reserved.

A glucose concentration and temperature sensor based on long period fiber gratings induced by electric-arc discharge

Science.gov (United States)

Du, Chao; Wang, Qi

2017-10-01

As one of the key parameters in biological and chemical reactions, glucose concentration objectively reflects the characteristics of reactions, so the real-time monitoring of glucose concentration is important in the field of biochemical. Meanwhile, the influence from temperature should be considered. The fiber sensors have been studied extensively for decades due to the advantages of small size, immunity to electromagnetic interference and high sensitivity, which are suitable for the application of biochemical sensing. A long period fiber grating (LPFG) sensor induced by electric-arc discharge has been fabricated and demonstrated for simultaneous measurement of glucose concentration and temperature. The proposed sensor was fabricated by inscribing a sing mode fiber (SMF) with periodic electric-arc discharge technology. During the fabrication process, the electric-arc discharge technology was produced by a commercial fusion splicer, and the period of inscribed LPFG was determined by the movement of translation stages. A serials of periodic geometrical deformations would be formed in SMF after the fabrication, and the discharge intensity and discharge time can be adjusted though the fusion splicer settings screen. The core mode can be coupled into the cladding modes at certain wavelength when they satisfy the phase-matching conditions, and there will be several resonance dips in the transmission spectrum in LPFG. The resonance dips formed by the coupling between cladding modes and core mode have different sensitivity responses, so the simultaneous measurement for multi-parameter can be realized by monitoring the wavelength shifts of the resonance dips. Compared with the LPFG based on conventional SMF, the glucose concentration sensitivity has been obviously enhanced by etching the cladding with hydrofluoric acid solution. Based on the independent measured results, a dual-parameter measurement matrix has been built for signal demodulation. Because of the easy

Intraperitoneal Glucose Sensing is Sometimes Surprisingly Rapid

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Anders Lyngvi Fougner

2016-04-01

Full Text Available Rapid, accurate and robust glucose measurements are needed to make a safe artificial pancreas for the treatment of diabetes mellitus type 1 and 2. The present gold standard of continuous glucose sensing, subcutaneous (SC glucose sensing, has been claimed to have slow response and poor robustness towards local tissue changes such as mechanical pressure, temperature changes, etc. The present study aimed at quantifying glucose dynamics from central circulation to intraperitoneal (IP sensor sites, as an alternative to the SC location. Intraarterial (IA and IP sensors were tested in three anaesthetized non-diabetic pigs during experiments with intravenous infusion of glucose boluses, enforcing rapid glucose level excursions in the range 70--360 mg/dL (approximately 3.8--20 mmol/L. Optical interferometric sensors were used for IA and IP measurements. A first-order dynamic model with time delay was fitted to the data after compensating for sensor dynamics. Additionally, off-the-shelf Medtronic Enlite sensors were used for illustration of SC glucose sensing. The time delay in glucose excursions from central circulation (IA to IP sensor location was found to be in the range 0--26 s (median: 8.5 s, mean: 9.7 s, SD 9.5 s, and the time constant was found to be 0.5--10.2 min (median: 4.8 min, mean: 4.7 min, SD 2.9 min. IP glucose sensing sites have a substantially faster and more distinctive response than SC sites when sensor dynamics is ignored, and the peritoneal fluid reacts even faster to changes in intravascular glucose levels than reported in previous animal studies. This study may provide a benchmark for future, rapid IP glucose sensors.

The ethylene glycol template assisted hydrothermal synthesis of Co3O4 nanowires; structural characterization and their application as glucose non-enzymatic sensor

International Nuclear Information System (INIS)

Khun, K.; Ibupoto, Z.H.; Liu, X.; Beni, V.; Willander, M.

2015-01-01

Highlights: • Ethylene glycol assisted Co 3 O 4 nanowires were synthesized by hydrothermal method. • The grown Co 3 O 4 nanowires were used for sensitive non-enzymatic glucose sensor. • The proposed glucose sensor shows a wide linear range with fast response. • The Co 3 O 4 modified electrode is a highly specific enzyme-less glucose sensor. - Abstract: In the work reported herein the ethylene glycol template assisted hydrothermal synthesis, onto Au substrate, of thin and highly dense cobalt oxide (Co 3 O 4 ) nanowires and their characterization and their application for non-enzymatic glucose sensing are reported. The structure and composition of Co 3 O 4 nanowires have been fully characterized using scanning electron microscopy, X-ray diffraction, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The synthesized Co 3 O 4 nanowires resulted to have high purity and showed diameter of approximately 10 nm. The prepared Co 3 O 4 nanowires coated gold electrodes were applied to the non-enzymatic detection of glucose. The developed sensor showed high sensitivity (4.58 × 10 1 μA mM −1 cm −2 ), a wide linear range of concentration (1.00 × 10 −4 –1.2 × 10 1 mM) and a detection limit of 2.65 × 10 −5 mM. The developed glucose sensor has also shown to be very stable and selective over interferents such as uric acid and ascorbic acid. Furthermore, the proposed fabrication process was shown to be highly reproducible response (over nine electrodes)

Effects of oral glucose load on endothelial function and on insulin and glucose fluctuations in healthy individuals

DEFF Research Database (Denmark)

Major-Pedersen, A; Ihlemann, N; Hermann, T S

2008-01-01

to better understand and cope with the postprandial state in insulin resistant individuals. METHODS: We assessed post-oral glucose load endothelial function (flow mediated dilation), plasma insulin, and blood glucose in 9 healthy subjects. RESULTS: The largest increases in delta FMD values (fasting FMD......BACKGROUND/AIMS: Postprandial hyperglycemia, an independent risk factor for cardiovascular disease, is accompanied by endothelial dysfunction. We studied the effect of oral glucose load on insulin and glucose fluctuations, and on postprandial endothelial function in healthy individuals in order...... value subtracted from postprandial FMD value) occurred at 3 hours after both glucose or placebo load, respectively: 4.80 +/- 1.41 (P = .009) and 2.34 +/- 1.47 (P = .15). Glucose and insulin concentrations achieved maximum peaks at one hour post-glucose load. CONCLUSION: Oral glucose load does not induce...

Effects of Oral Glucose Load on Endothelial Function and on Insulin and Glucose Fluctuations in Healthy Individuals

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A. Major-Pedersen

2008-01-01

Full Text Available Background/aims. Postprandial hyperglycemia, an independent risk factor for cardiovascular disease, is accompanied by endothelial dysfunction. We studied the effect of oral glucose load on insulin and glucose fluctuations, and on postprandial endothelial function in healthy individuals in order to better understand and cope with the postprandial state in insulin resistant individuals. Methods. We assessed post-oral glucose load endothelial function (flow mediated dilation, plasma insulin, and blood glucose in 9 healthy subjects. Results. The largest increases in delta FMD values (fasting FMD value subtracted from postprandial FMD value occurred at 3 hours after both glucose or placebo load, respectively: 4.80±1.41 (P = .009 and 2.34±1.47 (P = .15. Glucose and insulin concentrations achieved maximum peaks at one hour post-glucose load. Conclusion. Oral glucose load does not induce endothelial dysfunction in healthy individuals with mean insulin and glucose values of 5.6 mmol/L and 27.2 mmol/L, respectively, 2 hours after glucose load.

Spherulitic copper–copper oxide nanostructure-based highly sensitive nonenzymatic glucose sensor

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Das G

2015-08-01

Full Text Available Gautam Das, Thao Quynh Ngan Tran, Hyon Hee Yoon Department of Chemical and Biological Engineering, Gachon University, Seongnam, Republic of South Korea Abstract: In this work, three different spherulitic nanostructures Cu–CuOA, Cu–CuOB, and Cu–CuOC were synthesized in water-in-oil microemulsions by varying the surfactant concentration (30 mM, 40 mM, and 50 mM, respectively. The structural and morphological characteristics of the Cu–CuO nanostructures were investigated by ultraviolet–visible (UV–vis spectroscopy, X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy techniques. The synthesized nanostructures were deposited on multiwalled carbon nanotube (MWCNT-modified indium tin oxide (ITO electrodes to fabricate a nonenzymatic highly sensitive amperometric glucose sensor. The performance of the ITO/MWCNT/Cu–CuO electrodes in the glucose assay was examined by cyclic voltammetry and chronoamperometric studies. The sensitivity of the sensor varied with the spherulite type; Cu–CuOA, Cu–CuOB, and Cu–CuOC exhibited a sensitivity of 1,229, 3,012, and 3,642 µA mM-1·cm-2, respectively. Moreover, the linear range is dependent on the structure types: 0.023–0.29 mM, 0.07–0.8 mM, and 0.023–0.34 mM for Cu–CuOA, Cu–CuOB, and Cu–CuOC, respectively. An excellent response time of 3 seconds and a low detection limit of 2 µM were observed for Cu–CuOB at an applied potential of +0.34 V. In addition, this electrode was found to be resistant to interference by common interfering agents such as urea, cystamine, l-ascorbic acid, and creatinine. The high performance of the Cu–CuO spherulites with nanowire-to-nanorod outgrowths was primarily due to the high surface area and stability, and good three-dimensional structure. Furthermore, the ITO/MWCNT/Cu–CuOB electrode applied to real urine and serum sample showed satisfactory performance. Keywords: copper oxide, multiwalled

Hydrogen peroxide and glucose concentration measurement using optical fiber grating sensors with corrodible plasmonic nanocoatings.

Science.gov (United States)

Zhang, Xuejun; Wu, Ze; Liu, Fu; Fu, Qiangqiang; Chen, Xiaoyong; Xu, Jian; Zhang, Zhaochuan; Huang, Yunyun; Tang, Yong; Guo, Tuan; Albert, Jacques

2018-04-01

We propose and demonstrate hydrogen peroxide (H 2 O 2 ) and glucose concentration measurements using a plasmonic optical fiber sensor. The sensor utilizes a tilted fiber Bragg grating (TFBG) written in standard single mode communication fiber. The fiber is over coated with an nm-scale film of silver that supports surface plasmon resonances (SPRs). Such a tilted grating SPR structure provides a high density of narrow spectral resonances (Q-factor about 10 5 ) that overlap with the broader absorption band of the surface plasmon waves in the silver film, thereby providing an accurate tool to measure small shifts of the plasmon resonance frequencies. The H 2 O 2 to be detected acts as an oxidant to etch the silver film, which has the effect of gradually decreasing the SPR attenuation. The etching rate of the silver film shows a clear relationship with the H 2 O 2 concentration so that monitoring the progressively increasing attenuation of a selected surface plasmon resonance over a few minutes enables us to measure the H 2 O 2 concentration with a limit of detection of 0.2 μM. Furthermore, the proposed method can be applied to the determination of glucose in human serum for a concentration range from 0 to 12 mM (within the physiological range of 3-8 mM) by monitoring the H 2 O 2 produced by an enzymatic oxidation process. The sensor does not require accurate temperature control because of the inherent temperature insensitivity of TFBG devices referenced to the core mode resonance. A gold mirror coated on the fiber allows the sensor to work in reflection, which will facilitate the integration of the sensor with a hypodermic needle for in vitro measurements. The present study shows that Ag-coated TFBG-SPR can be applied as a promising type of sensing probe for optical detection of H 2 O 2 and glucose detection in human serum.

Hydrogen peroxide and glucose concentration measurement using optical fiber grating sensors with corrodible plasmonic nanocoatings

Science.gov (United States)

Zhang, Xuejun; Wu, Ze; Liu, Fu; Fu, Qiangqiang; Chen, Xiaoyong; Xu, Jian; Zhang, Zhaochuan; Huang, Yunyun; Tang, Yong; Guo, Tuan; Albert, Jacques

2018-01-01

We propose and demonstrate hydrogen peroxide (H2O2) and glucose concentration measurements using a plasmonic optical fiber sensor. The sensor utilizes a tilted fiber Bragg grating (TFBG) written in standard single mode communication fiber. The fiber is over coated with an nm-scale film of silver that supports surface plasmon resonances (SPRs). Such a tilted grating SPR structure provides a high density of narrow spectral resonances (Q-factor about 105) that overlap with the broader absorption band of the surface plasmon waves in the silver film, thereby providing an accurate tool to measure small shifts of the plasmon resonance frequencies. The H2O2 to be detected acts as an oxidant to etch the silver film, which has the effect of gradually decreasing the SPR attenuation. The etching rate of the silver film shows a clear relationship with the H2O2 concentration so that monitoring the progressively increasing attenuation of a selected surface plasmon resonance over a few minutes enables us to measure the H2O2 concentration with a limit of detection of 0.2 μM. Furthermore, the proposed method can be applied to the determination of glucose in human serum for a concentration range from 0 to 12 mM (within the physiological range of 3-8 mM) by monitoring the H2O2 produced by an enzymatic oxidation process. The sensor does not require accurate temperature control because of the inherent temperature insensitivity of TFBG devices referenced to the core mode resonance. A gold mirror coated on the fiber allows the sensor to work in reflection, which will facilitate the integration of the sensor with a hypodermic needle for in vitro measurements. The present study shows that Ag-coated TFBG-SPR can be applied as a promising type of sensing probe for optical detection of H2O2 and glucose detection in human serum. PMID:29675315

Effects of glucose load on cognitive functions in elderly people

NARCIS (Netherlands)

Zwaluw, N.L. van der; Rest, O. van de; Kessels, R.P.C.; Groot, L.C.P.G.M. de

2015-01-01

Glucose is the main fuel for the brain, and manipulation of the glucose supply may consequently affect brain function. The present review was conducted to provide an overview of studies that investigated the acute effects of glucose load on memory and other cognitive functions in elderly people. The

ZIF-67 derived porous Co3O4 hollow nanopolyhedron functionalized solution-gated graphene transistors for simultaneous detection of glucose and uric acid in tears.

Science.gov (United States)

Xiong, Can; Zhang, Tengfei; Kong, Weiyu; Zhang, Zhixiang; Qu, Hao; Chen, Wei; Wang, Yanbo; Luo, Linbao; Zheng, Lei

2018-03-15

Biomarkers in tears have attracted much attention in daily healthcare sensing and monitoring. Here, highly sensitive sensors for simultaneous detection of glucose and uric acid are successfully constructed based on solution-gated graphene transistors (SGGTs) with two separate Au gate electrodes, modified with GOx-CHIT and BSA-CHIT respectively. The sensitivity of the SGGT is dramatically improved by co-modifying the Au gate with ZIF-67 derived porous Co 3 O 4 hollow nanopolyhedrons. The sensing mechanism for glucose sensor is attributed to the reaction of H 2 O 2 generated by the oxidation of glucose near the gate, while the sensing mechanism for uric acid is due to the direct electro-oxidation of uric acid molecules on the gate. The optimized glucose and uric acid sensors show the detection limits both down to 100nM, far beyond the sensitivity required for non-invasive detection of glucose and uric acid in tears. The glucose and uric acid in real tear samples was quantitatively detected at 323.2 ± 16.1μM and 98.5 ± 16.3μM by using the functionalized SGGT device. Due to the low-cost, high-biocompatibility and easy-fabrication features of the ZIF-67 derived porous Co 3 O 4 hollow nanopolyhedron, they provide excellent electrocatalytic nanomaterials for enhancing sensitivity of SGGTs for a broad range of disease-related biomarkers. Copyright © 2017 Elsevier B.V. All rights reserved.

N-doped graphene-carbon nanotube hybrid networks attaching with gold nanoparticles for glucose non-enzymatic sensor.

Science.gov (United States)

Jeong, Hun; Nguyen, Dang Mao; Lee, Min Sang; Kim, Hong Gun; Ko, Sang Cheol; Kwac, Lee Ku

2018-09-01

Herein, we successfully developed a novel three dimensional (3D) opened networks based on nitrogen doped graphene‑carbon nanotubes attaching with gold nanoparticles (N-GR-CNTs/AuNPs) to apply for non-enzymatic glucose determination. It was demonstrated that the N-GR-CNTs/AuNPs modified electrode exhibited good behavior for glucose detection with a long linear range of 2 μM to 19.6 mM, high sensitivity of 0.9824 μA·mM -1 ·cm -2 , low detection limit of 500 nM, and negligible interference effect. The high performance of the N-GR-CNTs/AuNPs based sensor was assumed due to the outstanding catalytic activity of AuNPs well dispersing on N-GR-CNTs networks, which exhibited as a perfect supporting scaffold due to the enhanced electrical conductivity and large surface area. The obtained results indicated that the N-GR-CNTs/AuNPs hybrid is highly promising for sensitive and selective detection of glucose in sensor application. Copyright © 2018 Elsevier B.V. All rights reserved.

Sodium Glucose Cotransporter 2 (SGLT2 Plays as a Physiological Glucose Sensor and Regulates Cellular Contractility in Rat Mesangial Cells.

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Masanori Wakisaka

Full Text Available Mesangial cells play an important role in regulating glomerular filtration by altering their cellular tone. We report the presence of a sodium glucose cotransporter (SGLT in rat mesangial cells. This study in rat mesangial cells aimed to evaluate the expression and role of SGLT2.The SGLT2 expression in rat mesangial cells was assessed by Western blotting and reverse transcription-polymerase chain reaction (RT-PCR. Changes in the mesangial cell surface area at different glucose concentrations and the effects of extracellular Na+ and Ca2+ and of SGLT and Na+/Ca2+ exchanger (NCX inhibitors on cellular size were determined. The cellular sizes and the contractile response were examined during a 6-day incubation with high glucose with or without phlorizin, an SGLT inhibitor.Western blotting revealed an SGLT2 band, and RT-PCR analysis of SGLT2 revealed the predicted 422-bp band in both rat mesangial and renal proximal tubular epithelial cells. The cell surface area changed according to the extracellular glucose concentration. The glucose-induced contraction was abolished by the absence of either extracellular Na+ or Ca2+ and by SGLT and NCX inhibitors. Under the high glucose condition, the cell size decreased for 2 days and increased afterwards; these cells did not contract in response to angiotensin II, and the SGLT inhibitor restored the abolished contraction.These data suggest that SGLT2 is expressed in rat mesangial cells, acts as a normal physiological glucose sensor and regulates cellular contractility in rat mesangial cells.

Glycogen metabolism protects against metabolic insult to preserve carotid body function during glucose deprivation.

Science.gov (United States)

Holmes, Andrew P; Turner, Philip J; Carter, Paul; Leadbeater, Wendy; Ray, Clare J; Hauton, David; Buckler, Keith J; Kumar, Prem

2014-10-15

The view that the carotid body (CB) type I cells are direct physiological sensors of hypoglycaemia is challenged by the finding that the basal sensory neuronal outflow from the whole organ is unchanged in response to low glucose. The reason for this difference in viewpoint and how the whole CB maintains its metabolic integrity when exposed to low glucose is unknown. Here we show that, in the intact superfused rat CB, basal sensory neuronal activity was sustained during glucose deprivation for 29.1 ± 1.2 min, before irreversible failure following a brief period of excitation. Graded increases in the basal discharge induced by reducing the superfusate PO2 led to proportional decreases in the time to the pre-failure excitation during glucose deprivation which was dependent on a complete run-down in glycolysis and a fall in cellular energy status. A similar ability to withstand prolonged glucose deprivation was observed in isolated type I cells. Electron micrographs and immunofluorescence staining of rat CB sections revealed the presence of glycogen granules and the glycogen conversion enzymes glycogen synthase I and glycogen phosphorylase BB, dispersed throughout the type I cell cytoplasm. Furthermore, pharmacological attenuation of glycogenolysis and functional depletion of glycogen both significantly reduced the time to glycolytic run-down by ∼33 and 65%, respectively. These findings suggest that type I cell glycogen metabolism allows for the continuation of glycolysis and the maintenance of CB sensory neuronal output in periods of restricted glucose delivery and this may act as a key protective mechanism for the organ during hypoglycaemia. The ability, or otherwise, to preserve energetic status may thus account for variation in the reported capacity of the CB to sense physiological glucose concentrations and may even underlie its function during pathological states associated with augmented CB discharge. © 2014 The Authors. The Journal of Physiology © 2014

Non-invasive Blood Glucose Quantification Using a Hybrid Sensor

Directory of Open Access Journals (Sweden)

Sundararajan JAYAPAL

2009-02-01

Full Text Available Diabetes Mellitus is a group of metabolic diseases characterized by high blood sugar (glucose levels which result from defects in insulin secretion. It is very important for the diabetics and normal people to have a correct blood glucose level. The HbA1c test is the most preferred test by renowned doctors for glucose quantification. But this test is an invasive one. At present, there are many available techniques for this purpose but these are mostly invasive or minimally non-invasive and most of these are under research. Among the different methods available, the photo acoustic (PA methods provide a reliable solution since the acoustical energy loss is much less compared to the optical or other techniques. Here a novel framework is presented for blood glucose level measurement using a combination of the HbA1c test and a PA method to get an absolutely consistent and precise, non-invasive technique. The setup uses a pulsed laser diode with pulse duration of 5-15 ns and at a repetition rate of 10 Hz as the source. The detector setup is based on the piezoelectric detection. It consists of a ring detector that includes two double ring sensors that are attached to the ring shaped module that can be worn around the finger. The major aim is to detect the photo acoustic signals from the glycated hemoglobin with the least possible error. The proposed monitoring system is designed with extreme consideration to precision and compatibility with the other computing devices. The results obtained in this research have been studied and analyzed by comparing these with those of in-vitro techniques like the HPLC. The comparison has been plotted and it shows a least error. The results also show a positive drive for using this concept as a basis for future extension in quantifying the other blood components.

Soft, smart contact lenses with integrations of wireless circuits, glucose sensors, and displays.

Science.gov (United States)

Park, Jihun; Kim, Joohee; Kim, So-Yun; Cheong, Woon Hyung; Jang, Jiuk; Park, Young-Geun; Na, Kyungmin; Kim, Yun-Tae; Heo, Jun Hyuk; Lee, Chang Young; Lee, Jung Heon; Bien, Franklin; Park, Jang-Ung

2018-01-01

Recent advances in wearable electronics combined with wireless communications are essential to the realization of medical applications through health monitoring technologies. For example, a smart contact lens, which is capable of monitoring the physiological information of the eye and tear fluid, could provide real-time, noninvasive medical diagnostics. However, previous reports concerning the smart contact lens have indicated that opaque and brittle components have been used to enable the operation of the electronic device, and this could block the user's vision and potentially damage the eye. In addition, the use of expensive and bulky equipment to measure signals from the contact lens sensors could interfere with the user's external activities. Thus, we report an unconventional approach for the fabrication of a soft, smart contact lens in which glucose sensors, wireless power transfer circuits, and display pixels to visualize sensing signals in real time are fully integrated using transparent and stretchable nanostructures. The integration of this display into the smart lens eliminates the need for additional, bulky measurement equipment. This soft, smart contact lens can be transparent, providing a clear view by matching the refractive indices of its locally patterned areas. The resulting soft, smart contact lens provides real-time, wireless operation, and there are in vivo tests to monitor the glucose concentration in tears (suitable for determining the fasting glucose level in the tears of diabetic patients) and, simultaneously, to provide sensing results through the contact lens display.

Effects of glucose load on cognitive functions in elderly people.

Science.gov (United States)

van der Zwaluw, Nikita L; van de Rest, Ondine; Kessels, Roy P C; de Groot, Lisette C P G M

2015-02-01

Glucose is the main fuel for the brain, and manipulation of the glucose supply may consequently affect brain function. The present review was conducted to provide an overview of studies that investigated the acute effects of glucose load on memory and other cognitive functions in elderly people. The effects of sucrose on cognition and suggested mechanisms were also explored. A total of twenty studies met the inclusion criteria. In the majority of studies, episodic memory was investigated and a beneficial role for glucose in that specific cognitive domain was suggested. Other cognitive domains, i.e., working memory, semantic memory, visual memory, information-processing speed, attention, executive function, and visual/spatial function, have been studied less frequently and evidence for a beneficial effect of glucose was equivocal. Mechanisms are suggested to be mainly related to the human body's need for glucose as a metabolic substrate for physiological mechanisms in both central and peripheral processes. © The Author(s) 2015. Published by Oxford University Press on behalf of the International Life Sciences Institute. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Fabrication of Nonenzymatic Glucose Sensors Based on Multiwalled Carbon Nanotubes with Bimetallic Pt-M (M = Ru and Sn Catalysts by Radiolytic Deposition

Directory of Open Access Journals (Sweden)

Sun-Young Kwon

2012-01-01

Full Text Available Nonenzymatic glucose sensors employing multiwalled carbon nanotubes (MWNTs with highly dispersed Pt-M (M = Ru and Sn nanoparticles (Pt-M@PVP-MWNTs were fabricated by radiolytic deposition. The Pt-M nanoparticles on the MWNTs were characterized by transmittance electron microscopy, elemental analysis, and X-ray diffraction. They were found to be well dispersed and to exhibit alloy properties on the MWNT support. Electrochemical testing showed that these nonenzymatic sensors had larger currents (mA than that of a bare glassy carbon (GC electrode and one modified with MWNTs. The sensitivity (A mM−1, linear range (mM, and detection limit (mM (S/N = 3 of the glucose sensor with the Pt-Ru catalyst in NaOH electrolyte were determined as 18.0, 1.0–2.5, 0.7, respectively. The corresponding data of the sensor with Pt-Sn catalyst were 889.0, 1.00–3.00, and 0.3, respectively. In addition, these non-enzymatic sensors can effectively avoid interference arising from the oxidation of the common interfering species ascorbic acid and uric acid in NaOH electrolyte. The experimental results show that such sensors can be applied in the detection of glucose in commercial red wine samples.

Determination of hydrogen peroxide and glucose using a novel sensor platform based on Co0.4Fe0.6LaO3 nanoparticles

International Nuclear Information System (INIS)

Zhang, Zhen; Gu, Shuqing; Ding, Yaping; Zhang, Fenfen; Jin, Jindi

2013-01-01

We report on a novel nonenzymatic sensor platform for the determination of hydrogen peroxide and glucose. It is based on a carbon paste electrode that was modified with Co 0.4 Fe 0.6 LaO 3 nanoparticles synthesized by the sol–gel method. The structure and morphology of Co 0.4 Fe 0.6 LaO 3 nanoparticles were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical performance of this sensor was evaluated by cyclic voltammetry and amperometry, and the results demonstrated that it exhibits strong electrocatalytical activity towards the oxidation of H 2 O 2 and glucose in an alkaline medium. The sensor has a limit of detection as low as 2.0 nM of H 2 O 2 and a linear range that extends from 0.01 to 800 μM. The response to glucose is characterized by two analytical ranges of different slope, viz. from 0.05 to 5 μM and from 5 to 500 μM, with a 10 nM limit of detection. The glucose sensor has a fast response and good long term stability. (author)

Development of Chemically Amplified Optical Sensors for Continuous Blood Glucose Monitoring Final Report CRADA No. TSB-1162-95

Energy Technology Data Exchange (ETDEWEB)

Lane, Stephen M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Livermore, CA (United States); Mastrototaro, John J. [Minimed Technologies, Inc., Sylmar, CA (United States)

2018-01-22

Diabetes is a chronic disease that affects 14 million people in the U.S. and more than 110 million people worldwide. Each year in this country 27,000 diabetic patients become blind, 15,000 have kidney failure, and over 54,000 have peripheral limb amputations. In 1992, total healthcare costs in the U.S. for diabetes were more than $105 billion, approximately 15% of our healthcare budget. Conventional therapy for the most severe form of diabetes, insulin-dependent diabetes mellitus (IDDM) or Type I diabetes, is to administer one or two injections per day of various forms of insulin while monitoring blood glucose levels twice or three times daily with commercial glucometers that require blood samples. Near normal blood sugar levels (glycemic control) is difficult to achieve with conventional therapy. In the fall of 1993, the results of the 10-year $165 million Diabetes Control and Complications Trial (DCCT) were published which showed that intensive insulin management would lead to dramatically fewer cases of retinopathy (which leads to blindness), nephropathy (which leads to kidney failure), and neuropathy (which can lead to limb amputations) [New England Journal of Medicine, Vo1239, No.14 977-986 (1993)]. If existing commercial insulin pumps could be combined with a continuous glucose sensor, a more physiological and fine-tuned therapy could be provided - in effect, an artificial biomechanical pancreas would be available. Existing research suggested that such a development would dramatically improve glucose control, thus greatly reducing morbidity and mortality from this disease. MiniMed Technologies in Sylmar, CA, identified a number of optically based sensor strategies as well as candidate chemical reactions that could be used to implement a minimally invasive opto-chemical glucose sensor. LLNL evaluated these sensor strategies and chemical reactions. These evaluations were the first steps leading to development of a sensor of considerable importance that could

The effects of carbon nanotube addition and oxyfluorination on the glucose-sensing capabilities of glucose oxidase-coated carbon fiber electrodes

Energy Technology Data Exchange (ETDEWEB)

Im, Ji Sun; Yun, Jumi; Kim, Jong Gu [Department of Fine Chemical Engineering and Applied Chemistry, BK21-E2 M, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Bae, Tae-Sung [Department of Fine Chemical Engineering and Applied Chemistry, BK21-E2 M, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Korea Basic Science Institute (KBSI), Jeonju 561-756 (Korea, Republic of); Lee, Young-Seak, E-mail: youngslee@cnu.ac.kr [Department of Fine Chemical Engineering and Applied Chemistry, BK21-E2 M, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

2012-01-15

Glucose-sensing electrodes were constructed from carbon fibers by electrospinning and heat treatment. By controlling the pore size, the specific surface area and pore volume of the electrospun carbon fibers were increased for efficient immobilization of the glucose oxidase. Carbon nanotubes were embedded as an electrically conductive additive to improve the electrical property of the porous carbon fibers. In addition, the surface of the porous carbon fibers was modified with hydrophilic functional groups by direct oxyfluorination to increase the affinity between the hydrophobic carbon surface and the hydrophilic glucose oxidase molecules. The porosity of the carbon fibers was improved significantly with approximately 28- and 35-fold increases in the specific surface area and pore volume, respectively. The number of chemical bonds between carbon and oxygen were increased with higher oxygen content during oxyfluorination based on the X-ray photoelectron spectroscopy results. Glucose sensing was carried out by current voltagram and amperometric methods. A high-performance glucose sensor was obtained with high sensitivity and rapid response time as a result of carbon nanotube addition, physical activation and surface modification. The mechanism of the highly sensitive prepared glucose sensor was modeled by an enzyme kinetics study using the Michaelis-Menten equation.

Direct electron transfer of glucose oxidase and dual hydrogen peroxide and glucose detection based on water-dispersible carbon nanotubes derivative

Energy Technology Data Exchange (ETDEWEB)

Chen, Hsiao-Chien [Department of Biochemistry and Molecular Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, 250, Wuxing St., Taipei 11031, Taiwan (China); Tu, Yi-Ming; Hou, Chung-Che [Department of Chemical and Materials Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Tao-Yuan 33302, Taiwan (China); Lin, Yu-Chen [Wah Hong industrial Co. Ltd., 6 Lixing St., Guantian Dist., Tainan City 72046,Taiwan (China); Chen, Ching-Hsiang [Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, 43 Keelung Rd., Sec. 4, Taipei 10607, Taiwan (China); Yang, Kuang-Hsuan, E-mail: khy@mail.vnu.edu.tw [Department of Food and Beverage Management, Vanung University, 1, Van Nung Rd., Shuei-Wei Li, Chung-Li City 32061, Taiwan (China)

2015-03-31

Highlights: • Dual hydrogen peroxide and glucose sensor. • Direct electrochemistry of glucose oxidase used MWCNT-Py/GC electrode. • Change sensing function by adjusting pH value. - Abstract: A water-dispersible multi-walled carbon nanotubes (MWCNTs) derivative, MWCNTs-1-one-dihydroxypyridine (MWCNTs-Py) was synthesis via Friedel–Crafts chemical acylation. Raman spectra demonstrated the conjugated level of MWCNTs-Py was retained after this chemical modification. MWCNTs-Py showed dual hydrogen peroxide (H{sub 2}O{sub 2}) and glucose detections without mutual interference by adjusting pH value. It was sensitive to H{sub 2}O{sub 2} in acidic solution and displayed the high performances of sensitivity, linear range, response time and stability; meanwhile it did not respond to H{sub 2}O{sub 2} in neutral solution. In addition, this positively charged MWCNTs-Py could adsorb glucose oxidase (GOD) by electrostatic attraction. MWCNTs-Py-GOD/GC electrode showed the direct electron transfer (DET) of GOD with a pair of well-defined redox peaks, attesting the bioactivity of GOD was retained due to the non-destroyed immobilization. The high surface coverage of active GOD (3.5 × 10{sup −9} mol cm{sup −2}) resulted in exhibiting a good electrocatalytic activity toward glucose. This glucose sensor showed high sensitivity (68.1 μA mM{sup −1} cm{sup −2}) in a linear range from 3 μM to 7 mM in neutral buffer solution. The proposed sensor could distinguish H{sub 2}O{sub 2} and glucose, thus owning high selectivity and reliability.

Direct electron transfer of glucose oxidase and dual hydrogen peroxide and glucose detection based on water-dispersible carbon nanotubes derivative

International Nuclear Information System (INIS)

Chen, Hsiao-Chien; Tu, Yi-Ming; Hou, Chung-Che; Lin, Yu-Chen; Chen, Ching-Hsiang; Yang, Kuang-Hsuan

2015-01-01

Highlights: • Dual hydrogen peroxide and glucose sensor. • Direct electrochemistry of glucose oxidase used MWCNT-Py/GC electrode. • Change sensing function by adjusting pH value. - Abstract: A water-dispersible multi-walled carbon nanotubes (MWCNTs) derivative, MWCNTs-1-one-dihydroxypyridine (MWCNTs-Py) was synthesis via Friedel–Crafts chemical acylation. Raman spectra demonstrated the conjugated level of MWCNTs-Py was retained after this chemical modification. MWCNTs-Py showed dual hydrogen peroxide (H 2 O 2 ) and glucose detections without mutual interference by adjusting pH value. It was sensitive to H 2 O 2 in acidic solution and displayed the high performances of sensitivity, linear range, response time and stability; meanwhile it did not respond to H 2 O 2 in neutral solution. In addition, this positively charged MWCNTs-Py could adsorb glucose oxidase (GOD) by electrostatic attraction. MWCNTs-Py-GOD/GC electrode showed the direct electron transfer (DET) of GOD with a pair of well-defined redox peaks, attesting the bioactivity of GOD was retained due to the non-destroyed immobilization. The high surface coverage of active GOD (3.5 × 10 −9 mol cm −2 ) resulted in exhibiting a good electrocatalytic activity toward glucose. This glucose sensor showed high sensitivity (68.1 μA mM −1 cm −2 ) in a linear range from 3 μM to 7 mM in neutral buffer solution. The proposed sensor could distinguish H 2 O 2 and glucose, thus owning high selectivity and reliability

An In-Line Photonic Biosensor for Monitoring of Glucose Concentrations

Directory of Open Access Journals (Sweden)

Ala'aldeen Al-Halhouli

2014-08-01

Full Text Available This paper presents two PDMS photonic biosensor designs that can be used for continuous monitoring of glucose concentrations. The first design, the internally immobilized sensor, consists of a reactor chamber, micro-lenses and self-alignment structures for fiber optics positioning. This sensor design allows optical detection of glucose concentrations under continuous glucose flow conditions of 33 µL/h based on internal co-immobilization of glucose oxidase (GOX and horseradish peroxidase (HRP on the internal PDMS surface of the reactor chamber. For this design, two co-immobilization methods, the simple adsorption and the covalent binding (PEG methods were tested. Experiments showed successful results when using the covalent binding (PEG method, where glucose concentrations up to 5 mM with a coefficient of determination (R2 of 0.99 and a limit of detection of 0.26 mM are detectable. The second design is a modified version of the internally immobilized sensor, where a microbead chamber and a beads filling channel are integrated into the sensor. This modification enabled external co-immobilization of enzymes covalently onto functionalized silica microbeads and allows binding a huge amount of HRP and GOX enzymes on the microbeads surfaces which increases the interaction area between immobilized enzymes and the analyte. This has a positive effect on the amount and rate of chemical reactions taking place inside the chamber. The sensor was tested under continuous glucose flow conditions and was found to be able to detect glucose concentrations up to 10 mM with R2 of 0.98 and a limit of detection of 0.7 mM. Such results are very promising for the application in photonic LOC systems used for online analysis.

MoS2 nanosheet functionalized with Cu nanoparticles and its application for glucose detection

International Nuclear Information System (INIS)

Huang, Jingwei; Dong, Zhengping; Li, Yanrong; Li, Jing; Tang, Weijie; Yang, Haidong; Wang, Jia; Bao, Yun; Jin, Jun; Li, Rong

2013-01-01

Graphical abstract: - Highlights: • First report on decorating MoS 2 nanosheet with Cu nanoparticles by chemical reduction. • Cu nanoparticles were uniformly decorated on MoS 2 nanosheet. • Glucose biosensor based on copper nanoparticles-MoS 2 nanosheet hybrid is fabricated. • The biosensor exhibits high sensitivity. - Abstract: For the first time, Cu nanoparticles were evenly decorated on MoS 2 nanosheet by chemical reduction. The as-prepared Cu-MoS 2 hybrid was characterized by atomic force microscope (AFM), Raman spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and then used to fabricate a non-enzymatic glucose sensor. The performance of our sensor was investigated by cyclic voltammetry and amperometric measurement in alkaline media. Electrochemical tests showed that Cu-MoS 2 hybrid exhibited synergistic electrocatalytic activity on the oxidation of glucose with a high sensitivity of 1055 μA mM −1 cm −2 and a linear range up to 4 mM

Graphene-Paper Based Electrochemical Sensors

DEFF Research Database (Denmark)

Zhang, Minwei; Halder, Arnab; Cao, Xianyi

2017-01-01

in electrochemical sensors and energy technologies amongothers. In this chapter, we present some examples to overview recent advances in theresearch and development of two-dimensional (2D) graphene papers as new materialsfor electrochemical sensors. The chapter covers the design, fabrication, functionalizationand...... functionalization ofgraphene papers with polymer and nanoscale functional building blocks for electrochemical-sensing purposes. In terms of electrochemical-sensing applications, the emphasis ison enzyme-graphene and nanoparticle-graphene paper-based systems for the detectionof glucose. We finally conclude...

Copper@carbon coaxial nanowires synthesized by hydrothermal carbonization process from electroplating wastewater and their use as an enzyme-free glucose sensor.

Science.gov (United States)

Zhao, Yuxin; He, Zhaoyang; Yan, Zifeng

2013-01-21

In the pursuit of electrocatalysts with great economic and ecological values for non-enzymatic glucose sensors, one-dimensional copper@carbon (Cu@C) core-shell coaxial nanowires (NWs) have been successfully prepared via a simple continuous flow wet-chemistry approach from electroplating wastewater. The as-obtained products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy and Raman spectroscopy. The electrocatalytic activity of the modified electrodes by Cu@C NWs towards glucose oxidation was investigated by cyclic voltammetry and chronoamperometry. It was found that the as-obtained Cu@C NWs showed good electrochemical properties and could be used as an electrochemical sensor for the detection of glucose molecules. Compared to the other electrodes including the bare Nafion/glassy carbon electrode (GCE) and several hot hybrid nanostructures modified GCE, a substantial decrease in the overvoltage of the glucose oxidation was observed at the Cu@C NWs electrodes with oxidation starting at ca. 0.20 V vs. Ag/AgCl (3 M KCl). At an applied potential of 0.65 V, Cu@C NWs electrodes had a high and reproducible sensitivity of 437.8 µA cm(-2) mM(-1) to glucose. Linear responses were obtained with a detection limit of 50 nM. More importantly, the proposed electrode also had good stability, high resistance against poisoning by chloride ion and commonly interfering species. These good analytical performances make Cu@C NWs promising for the future development of enzyme-free glucose sensors.

Osteocalcin protects pancreatic beta cell function and survival under high glucose conditions

Energy Technology Data Exchange (ETDEWEB)

Kover, Karen, E-mail: kkover@cmh.edu [Division of Endocrine/Diabetes, Children' s Mercy Hospital & Clinics, Kansas City, MO 64108 (United States); University of Missouri-Kansas City School of Medicine, Kansas City, MO 64108 (United States); Yan, Yun; Tong, Pei Ying; Watkins, Dara; Li, Xiaoyu [Division of Endocrine/Diabetes, Children' s Mercy Hospital & Clinics, Kansas City, MO 64108 (United States); University of Missouri-Kansas City School of Medicine, Kansas City, MO 64108 (United States); Tasch, James; Hager, Melissa [Kansas City University Medical Biosciences, Kansas City, MO (United States); Clements, Mark; Moore, Wayne V. [Division of Endocrine/Diabetes, Children' s Mercy Hospital & Clinics, Kansas City, MO 64108 (United States); University of Missouri-Kansas City School of Medicine, Kansas City, MO 64108 (United States)

2015-06-19

Diabetes is characterized by progressive beta cell dysfunction and loss due in part to oxidative stress that occurs from gluco/lipotoxicity. Treatments that directly protect beta cell function and survival in the diabetic milieu are of particular interest. A growing body of evidence suggests that osteocalcin, an abundant non-collagenous protein of bone, supports beta cell function and proliferation. Based on previous gene expression data by microarray, we hypothesized that osteocalcin protects beta cells from glucose-induced oxidative stress. To test our hypothesis we cultured isolated rat islets and INS-1E cells in the presence of normal, high, or high glucose ± osteocalcin for up to 72 h. Oxidative stress and viability/mitochondrial function were measured by H{sub 2}O{sub 2} assay and Alamar Blue assay, respectively. Caspase 3/7 activity was also measured as a marker of apoptosis. A functional test, glucose stimulated insulin release, was conducted and expression of genes/protein was measured by qRT-PCR/western blot/ELISA. Osteocalcin treatment significantly reduced high glucose-induced H{sub 2}O{sub 2} levels while maintaining viability/mitochondrial function. Osteocalcin also significantly improved glucose stimulated insulin secretion and insulin content in rat islets after 48 h of high glucose exposure compared to untreated islets. As expected sustained high glucose down-regulated gene/protein expression of INS1 and BCL2 while increasing TXNIP expression. Interestingly, osteocalcin treatment reversed the effects of high glucose on gene/protein expression. We conclude that osteocalcin can protect beta cells from the negative effects of glucose-induced oxidative stress, in part, by reducing TXNIP expression, thereby preserving beta cell function and survival. - Highlights: • Osteocalcin reduces glucose-induced oxidative stress in beta cells. • Osteocalcin preserves beta cell function and survival under stress conditions. • Osteocalcin reduces glucose

Osteocalcin protects pancreatic beta cell function and survival under high glucose conditions

International Nuclear Information System (INIS)

Kover, Karen; Yan, Yun; Tong, Pei Ying; Watkins, Dara; Li, Xiaoyu; Tasch, James; Hager, Melissa; Clements, Mark; Moore, Wayne V.

2015-01-01

Diabetes is characterized by progressive beta cell dysfunction and loss due in part to oxidative stress that occurs from gluco/lipotoxicity. Treatments that directly protect beta cell function and survival in the diabetic milieu are of particular interest. A growing body of evidence suggests that osteocalcin, an abundant non-collagenous protein of bone, supports beta cell function and proliferation. Based on previous gene expression data by microarray, we hypothesized that osteocalcin protects beta cells from glucose-induced oxidative stress. To test our hypothesis we cultured isolated rat islets and INS-1E cells in the presence of normal, high, or high glucose ± osteocalcin for up to 72 h. Oxidative stress and viability/mitochondrial function were measured by H 2 O 2 assay and Alamar Blue assay, respectively. Caspase 3/7 activity was also measured as a marker of apoptosis. A functional test, glucose stimulated insulin release, was conducted and expression of genes/protein was measured by qRT-PCR/western blot/ELISA. Osteocalcin treatment significantly reduced high glucose-induced H 2 O 2 levels while maintaining viability/mitochondrial function. Osteocalcin also significantly improved glucose stimulated insulin secretion and insulin content in rat islets after 48 h of high glucose exposure compared to untreated islets. As expected sustained high glucose down-regulated gene/protein expression of INS1 and BCL2 while increasing TXNIP expression. Interestingly, osteocalcin treatment reversed the effects of high glucose on gene/protein expression. We conclude that osteocalcin can protect beta cells from the negative effects of glucose-induced oxidative stress, in part, by reducing TXNIP expression, thereby preserving beta cell function and survival. - Highlights: • Osteocalcin reduces glucose-induced oxidative stress in beta cells. • Osteocalcin preserves beta cell function and survival under stress conditions. • Osteocalcin reduces glucose-induced TXNIP

Fabrication and Optimization of a Nanoporous Platinum Electrode and a Non-enzymatic Glucose Micro-sensor on Silicon

Directory of Open Access Journals (Sweden)

Younghun Kim

2008-10-01

Full Text Available In this paper, optimal conditions for fabrication of nanoporous platinum (Pt were investigated in order to use it as a sensitive sensing electrode for silicon CMOS integrable non-enzymatic glucose micro-sensor applications. Applied charges, voltages, and temperatures were varied during the electroplating of Pt into the formed nonionic surfactant C16EO8 nano-scaled molds in order to fabricate nanoporous Pt electrodes with large surface roughness factor (RF, uniformity, and reproducibility. The fabricated nanoporous Pt electrodes were characterized using atomic force microscopy (AFM and electrochemical cyclic voltammograms. Optimal electroplating conditions were determined to be an applied charge of 35 mC/mm2, a voltage of -0.12 V, and a temperature of 25 °C, respectively. The optimized nanoporous Pt electrode had an electrochemical RF of 375 and excellent reproducibility. The optimized nanoporous Pt electrode was applied to fabricate non-enzymatic glucose micro-sensor with three electrode systems. The fabricated sensor had a size of 3 mm x 3 mm, air gap of 10 µm, working electrode (WE area of 4.4 mm2, and sensitivity of 37.5 µA•L/mmol•cm2. In addition, it showed large detection range from 0.05 to 30 mmolL-1 and stable recovery responsive to the step changes in glucose concentration.

A Novel Microdialysis Glucose Sensor System Based on Co-immobilizing on AU Micro-Electrode by SOL-GEL Technique

National Research Council Canada - National Science Library

Yu, Ping

2001-01-01

.... The sensor is based on co_immobilizing glucose oxidase (COD) with the catalase by sol-gel technique on the surface of the silicon bases with two pattern of An microelectrodes. A graduated ("sandwich...

The ethylene glycol template assisted hydrothermal synthesis of Co{sub 3}O{sub 4} nanowires; structural characterization and their application as glucose non-enzymatic sensor

Energy Technology Data Exchange (ETDEWEB)

Khun, K., E-mail: kimleang.khun@liu.se [Department of Science and Technology, Linköping University, SE-60174 Norrköping (Sweden); Ibupoto, Z.H. [Dr M.A. Kazi Institute of Chemistry, University of Sindh Jamshoro, Sindh Jamshoro (Pakistan); Liu, X. [Department of Physics, Chemistry and Biology, Linköping University, 58183 Linköping (Sweden); Beni, V. [Biosensors and Biolelectronics Centre, Department of Physics, Chemistry and Biology, Linköping University, 58183 Linköping (Sweden); Willander, M. [Department of Science and Technology, Linköping University, SE-60174 Norrköping (Sweden)

2015-04-15

Highlights: • Ethylene glycol assisted Co{sub 3}O{sub 4} nanowires were synthesized by hydrothermal method. • The grown Co{sub 3}O{sub 4} nanowires were used for sensitive non-enzymatic glucose sensor. • The proposed glucose sensor shows a wide linear range with fast response. • The Co{sub 3}O{sub 4} modified electrode is a highly specific enzyme-less glucose sensor. - Abstract: In the work reported herein the ethylene glycol template assisted hydrothermal synthesis, onto Au substrate, of thin and highly dense cobalt oxide (Co{sub 3}O{sub 4}) nanowires and their characterization and their application for non-enzymatic glucose sensing are reported. The structure and composition of Co{sub 3}O{sub 4} nanowires have been fully characterized using scanning electron microscopy, X-ray diffraction, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The synthesized Co{sub 3}O{sub 4} nanowires resulted to have high purity and showed diameter of approximately 10 nm. The prepared Co{sub 3}O{sub 4} nanowires coated gold electrodes were applied to the non-enzymatic detection of glucose. The developed sensor showed high sensitivity (4.58 × 10{sup 1} μA mM{sup −1} cm{sup −2}), a wide linear range of concentration (1.00 × 10{sup −4}–1.2 × 10{sup 1} mM) and a detection limit of 2.65 × 10{sup −5} mM. The developed glucose sensor has also shown to be very stable and selective over interferents such as uric acid and ascorbic acid. Furthermore, the proposed fabrication process was shown to be highly reproducible response (over nine electrodes)

A label-free fiber-optic Turbidity Affinity Sensor (TAS) for continuous glucose monitoring.

Science.gov (United States)

Dutt-Ballerstadt, Ralph; Evans, Colton; Pillai, Arun P; Gowda, Ashok

2014-11-15

In this paper, we describe the concept of a novel implantable fiber-optic Turbidity Affinity Sensor (TAS) and report on the findings of its in-vitro performance for continuous glucose monitoring. The sensing mechanism of the TAS is based on glucose-specific changes in light scattering (turbidity) of a hydrogel suspension consisting of small particles made of crosslinked dextran (Sephadex G100), and a glucose- and mannose-specific binding protein - Concanavalin A (ConA). The binding of ConA to Sephadex particles results in a significant turbidity increase that is much greater than the turbidity contribution by the individual components. The turbidity of the TAS was measured by determining the intensity of light passing through the suspension enclosed within a small semi-permeable hollow fiber (OD: 220 μm, membrane thickness: 20 μm, molecular weight cut-off: 10 kDa) using fiber optics. The intensity of measured light of the TAS was proportional to the glucose concentration over the concentration range from 50mg/dL to 400mg/dL in PBS and whole blood at 37°C (R>0.96). The response time was approximately 4 min. The stability of the glucose response of the TAS decreased only slightly (by 20%) over an 8-day study period at 37°C. In conclusion, this study demonstrated proof-of-concept of the TAS for interstitial glucose monitoring. Due to the large signal amplitude of the turbidity change, and the lack of need for wavelength-specific emission and excitation filters, a very small, robust and compact TAS device with an extremely short optical pathlength could be feasibly designed and implemented for in-vivo glucose monitoring in people with diabetes. Copyright © 2014 Elsevier B.V. All rights reserved.

Accuracy and precision of flash glucose monitoring sensors inserted into the abdomen and upper thigh compared with the upper arm.

Science.gov (United States)

Charleer, Sara; Mathieu, Chantal; Nobels, Frank; Gillard, Pieter

2018-06-01

Nowadays, most Belgian patients with type 1 diabetes use flash glucose monitoring (FreeStyle Libre [FSL]; Abbott Diabetes Care, Alameda, California) to check their glucose values, but some patients find the sensor on the upper arm too visible. The aim of the present study was to compare the accuracy and precision of FSL sensors when placed on different sites. A total of 23 adults with type 1 diabetes used three FSL sensors simultaneously for 14 days on the upper arm, abdomen and upper thigh. FSL measurements were compared with capillary blood glucose (BG) measurements obtained with a built-in FSL BG meter. The aggregated mean absolute relative difference was 11.8 ± 12.0%, 18.5 ± 18.4% and 12.3 ± 13.8% for the arm, abdomen (P = .002 vs arm) and thigh (P = .5 vs arm), respectively. Results of Clarke error grid analysis for the arm and thigh were similar (zone A: 84.9% vs 84.5%; P = .6), while less accuracy was seen for the abdomen (zone A: 69.4%; P = .01). Apart from the first day, the accuracy of FSL sensors on the arm and thigh was more stable across the 14-day wear duration than accuracy of sensors on the abdomen, which deteriorated mainly during week 2 (P < .0005). The aggregated precision absolute relative difference was markedly lower for the arm/thigh (10.9 ± 11.9%) compared with the arm/abdomen (20.9 ± 22.8%; P = .002). Our results indicate that the accuracy and precision of FSL sensors placed on the upper thigh are similar to the upper arm, whereas the abdomen performed unacceptably poorly. © 2018 John Wiley & Sons Ltd.

Luminol, horseradish peroxidase, and glucose oxidase ternary functionalized graphene oxide for ultrasensitive glucose sensing.

Science.gov (United States)

Li, Fang; Ma, Wenjing; Liu, Jiachang; Wu, Xiang; Wang, Yan; He, Jianbo

2018-01-01

Luminol, horseradish peroxidase (HRP), and glucose oxidase (GOx) ternary functionalized graphene oxide (HRP/GOx-luminol-GO) with excellent chemiluminescence (CL) activity and specific enzymatic property was prepared via a simple and general strategy for the first time. In this approach, luminol functionalized GO (luminol-GO) was prepared by gently stirring GO with luminol. Then HRP and GOx were further co-immobilized onto the surface of luminol-GO by storing HRP and GOx with luminol-GO at 4 °C overnight, to form HRP/GOx-luminol-GO bionanocomposites. The synthesized HRP/GOx-luminol-GO could react with H 2 O 2 generated from GOx catalyzed glucose oxidization reaction, to produce strong CL emission in the presence of co-immobilized HRP. Thus, we developed an ultrasensitive, homogeneous, reagentless, selective, and simple CL sensing system for glucose detection. The resulting biosensors exhibited ultra-wide linear range from 5.0 nM to 5.0 mM, and an ultra-low detection limit of 1.2 nM, which was more than 3 orders of magnitude lower than previously reported methods. Furthermore, the sensing system was successfully applied for the detection of glucose in human blood samples.

Capacitive Sensing of Glucose in Electrolytes Using Graphene Quantum Capacitance Varactors.

Science.gov (United States)

Zhang, Yao; Ma, Rui; Zhen, Xue V; Kudva, Yogish C; Bühlmann, Philippe; Koester, Steven J

2017-11-08

A novel graphene-based variable capacitor (varactor) that senses glucose based on the quantum capacitance effect was successfully developed. The sensor utilizes a metal-oxide-graphene varactor device structure that is inherently compatible with passive wireless sensing, a key advantage for in vivo glucose sensing. The graphene varactors were functionalized with pyrene-1-boronic acid (PBA) by self-assembly driven by π-π interactions. Successful surface functionalization was confirmed by both Raman spectroscopy and capacitance-voltage characterization of the devices. Through glucose binding to the PBA, the glucose concentration in the buffer solutions modulates the level of electrostatic doping of the graphene surface to different degrees, which leads to capacitance changes and Dirac voltage shifts. These responses to the glucose concentration were shown to be reproducible and reversible over multiple measurement cycles, suggesting promise for eventual use in wireless glucose monitoring.

Polymer optical fiber compound parabolic concentrator tip for enhanced coupling efficiency for fluorescence based glucose sensors

DEFF Research Database (Denmark)

Hassan, Hafeez Ul; Nielsen, Kristian; Aasmul, Søren

2015-01-01

We demonstrate that the light excitation and capturing efficiency of fluorescence based fiber-optical sensors can be significantly increased by using a CPC (Compound Parabolic Concentrator) tip instead of the standard plane-cut tip. We use Zemax modelling to find the optimum CPC tip profile...... and fiber length of a polymer optical fiber diabetes sensor for continuous monitoring of glucose levels. We experimentally verify the improved performance of the CPC tipped sensor and the predicted production tolerances. Due to physical size requirements when the sensor has to be inserted into the body...... a non-optimal fiber length of 35 mm is chosen. For this length an average improvement in efficiency of a factor of 1.7 is experimentally demonstrated and critically compared to the predicted ideal factor of 3 in terms of parameters that should be improved through production optimization....

Polymer optical fiber compound parabolic concentrator tip for enhanced coupling efficiency for fluorescence based glucose sensors.

Science.gov (United States)

Hassan, Hafeez Ul; Nielsen, Kristian; Aasmul, Soren; Bang, Ole

2015-12-01

We demonstrate that the light excitation and capturing efficiency of fluorescence based fiber-optical sensors can be significantly increased by using a CPC (Compound Parabolic Concentrator) tip instead of the standard plane-cut tip. We use Zemax modelling to find the optimum CPC tip profile and fiber length of a polymer optical fiber diabetes sensor for continuous monitoring of glucose levels. We experimentally verify the improved performance of the CPC tipped sensor and the predicted production tolerances. Due to physical size requirements when the sensor has to be inserted into the body a non-optimal fiber length of 35 mm is chosen. For this length an average improvement in efficiency of a factor of 1.7 is experimentally demonstrated and critically compared to the predicted ideal factor of 3 in terms of parameters that should be improved through production optimization.

Sensor-integrated polymer actuators for closed-loop drug delivery system

Science.gov (United States)

Xu, Han; Wang, Chunlei; Kulinsky, Lawrence; Zoval, Jim; Madou, Marc

2006-03-01

This work presents manufacturing and testing of a closed-loop drug delivery system where drug release is achieved by an electrochemical actuation of an array of polymeric valves on a set of drug reservoirs. The valves are based on bi-layer structures made of polypyrrole/gold in the shape of a flap that is hinged on one side of a valve seat. Drugs stored in the underlying chambers are released by bending the bi-layer flaps back with a small applied bias. These polymeric valves simultaneously function as both drug release components and biological/chemical sensors responding to a specific biological or environmental stimulus. The sensors may send signals to the control module to realize closed-loop control of the drug release. In this study a glucose sensor has been integrated with the polymeric actuators through immobilization of glucose oxidase(GOx) within polypyrrole(PPy) valves. Sensitivities per unit area of the integrated glucose sensor have been measured and compared before and after the actuation of the sensor/actuator PPy/DBS/GOx film. Other sensing parameters such as linear range and response time were discussed as well. Using an array of these sensor/actuator cells, the amount of released drug, e.g. insulin, can be precisely controlled according to the surrounding glucose concentration detected by the glucose sensor. Activation of these reservoirs can be triggered either by the signal from the sensor, or by the signal from the operator. This approach also serves as the initial step to use the proposed system as an implantable drug delivery platform in the future.

Platinum decorated carbon nanotubes for highly sensitive amperometric glucose sensing

International Nuclear Information System (INIS)

Xie Jining; Wang Shouyan; Aryasomayajula, L; Varadan, V K

2007-01-01

Fine platinum nanoparticles (1-5 nm in diameter) were deposited on functionalized multi-walled carbon nanotubes (MWNTs) through a decoration technique. A novel type of enzymatic Pt/MWNTs paste-based mediated glucose sensor was fabricated. Electrochemical measurements revealed a significantly improved sensitivity (around 52.7 μA mM -1 cm -2 ) for glucose sensing without using any picoampere booster or Faraday cage. In addition, the calibration curve exhibited a good linearity in the range of 1-28 mM of glucose concentration. Transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS) were performed to investigate the nanoscale structure and the chemical bonding information of the Pt/MWNTs paste-based sensing material, respectively. The improved sensitivity of this novel glucose sensor could be ascribed to its higher electroactive surface area, enhanced electron transfer, efficient enzyme immobilization, unique interaction in nanoscale and a synergistic effect on the current signal from possible multi-redox reactions

A glucose oxidase-coupled DNAzyme sensor for glucose detection in tears and saliva.

Science.gov (United States)

Liu, Chengcheng; Sheng, Yongjie; Sun, Yanhong; Feng, Junkui; Wang, Shijin; Zhang, Jin; Xu, Jiacui; Jiang, Dazhi

2015-08-15

Biosensors have been widely investigated and utilized in a variety of fields ranging from environmental monitoring to clinical diagnostics. Glucose biosensors have triggered great interest and have been widely exploited since glucose determination is essential for diabetes diagnosis. In here, we designed a novel dual-enzyme biosensor composed of glucose oxidase (GOx) and pistol-like DNAzyme (PLDz) to detect glucose levels in tears and saliva. First, GOx, as a molecular recognition element, catalyzes the oxidation of glucose forming H2O2; then PLDz recognizes the produced H2O2 as a secondary signal and performs a self-cleavage reaction promoted by Mn(2+), Co(2+) and Cu(2+). Thus, detection of glucose could be realized by monitoring the cleavage rate of PLDz. The slope of the cleavage rate of PLDz versus glucose concentration curve was fitted with a Double Boltzmann equation, with a range of glucose from 100 nM to 10mM and a detection limit of 5 μM. We further applied the GOx-PLDz 1.0 biosensor for glucose detection in tears and saliva, glucose levels in which are 720±81 μM and 405±56 μM respectively. Therefore, the GOx-PLDz 1.0 biosensor is able to determine glucose levels in tears and saliva as a noninvasive glucose biosensor, which is important for diabetic patients with frequent/continuous glucose monitoring requirements. In addition, induction of DNAzyme provides a new approach in the development of glucose biosensors. Copyright © 2015 Elsevier B.V. All rights reserved.

Pseudo-bi-enzyme glucose sensor: ZnS hollow spheres and glucose oxidase concerted catalysis glucose.

Science.gov (United States)

Shuai, Ying; Liu, Changhua; Wang, Jia; Cui, Xiaoyan; Nie, Ling

2013-06-07

This work creatively uses peroxidase-like ZnS hollow spheres (ZnS HSs) to cooperate with glucose oxidase (GOx) for glucose determinations. This approach is that the ZnS HSs electrocatalytically oxidate the enzymatically generated H2O2 to O2, and then the O2 circularly participates in the previous glucose oxidation by glucose oxidase. Au nanoparticles (AuNPs) and carbon nanotubes (CNTs) are used as electron transfer and enzyme immobilization matrices, respectively. The biosensor of glucose oxidase-carbon nanotubes-Au nanoparticles-ZnS hollow spheres-gold electrode (GOx-CNT-AuNPs-ZnS HSs-GE) exhibits a rapid response, a low detection limit (10 μM), a wide linear range (20 μM to 7 mM) as well as good anti-interference, long-term longevity and reproducibility.

On-chip highly sensitive saliva glucose sensing using multilayer films composed of single-walled carbon nanotubes, gold nanoparticles, and glucose oxidase

Directory of Open Access Journals (Sweden)

Wenjun Zhang

2015-06-01

Full Text Available It is very important for human health to rapidly and accurately detect glucose levels in biological environments, especially for diabetes mellitus. We proposed a simple, highly sensitive, accurate, convenient, low-cost, and disposable glucose biosensor on a single chip. A working (sensor electrode, a counter electrode, and a reference electrode are integrated on a single chip through micro-fabrication. The working electrode is functionalized through a layer-by-layer (LBL assembly of single-walled carbon nanotubes (SWNTs and multilayer films composed of chitosan (CS, gold nanoparticles (GNp, and glucose oxidase (GOx to obtain high sensitivity and accuracy. The glucose sensor has following features: (1 direct electron transfer between GOx and the electrode surface; (2 on-a-chip; (3 glucose detection down to 0.1 mg/dL (5.6 μM; (4 good sensing linearity over 0.017–0.81 mM; (5 high sensitivity (61.4 μA/mM-cm2 with a small reactive area (8 mm2; (6 fast response; (7 high reproducibility and repeatability; (8 reliable and accurate saliva glucose detection. Thus, this disposable biosensor will be an alternative for real time tracking of glucose levels from body fluids, e.g. saliva, in a noninvasive, pain-free, accurate, and continuous way. In addition to being used as a disposable glucose biosensor, it also provides a suitable platform for on-chip electrochemical sensing for other chemical agents and biomolecules.

Glucose-Sensitive Hydrogel Optical Fibers Functionalized with Phenylboronic Acid.

Science.gov (United States)

Yetisen, Ali K; Jiang, Nan; Fallahi, Afsoon; Montelongo, Yunuen; Ruiz-Esparza, Guillermo U; Tamayol, Ali; Zhang, Yu Shrike; Mahmood, Iram; Yang, Su-A; Kim, Ki Su; Butt, Haider; Khademhosseini, Ali; Yun, Seok-Hyun

2017-04-01

Hydrogel optical fibers are utilized for continuous glucose sensing in real time. The hydrogel fibers consist of poly(acrylamide-co-poly(ethylene glycol) diacrylate) cores functionalized with phenylboronic acid. The complexation of the phenylboronic acid and cis-diol groups of glucose enables reversible changes of the hydrogel fiber diameter. The analyses of light propagation loss allow for quantitative glucose measurements within the physiological range. © 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nonenzymatic Glucose Sensor Based on In Situ Reduction of Ni/NiO-Graphene Nanocomposite

Directory of Open Access Journals (Sweden)

Xiaohui Zhang

2016-10-01

Full Text Available Ni/NiO nanoflower modified reduced graphene oxide (rGO nanocomposite (Ni/NiO-rGO was introduced to screen printed electrode (SPE for the construction of a nonenzymatic electrochemical glucose biosensor. The Ni/NiO-rGO nanocomposite was synthesized by an in situ reduction process. Graphene oxide (GO hybrid Nafion sheets first chemical adsorbed Ni ions and assembled on the SPE. Subsequently, GO and Ni ions were reduced by hydrazine hydrate. The electrochemical properties of such a Ni/NiO-rGO modified SPE were carefully investigated. It showed a high activity for electrocatalytic oxidation of glucose in alkaline medium. The proposed nonenzymatic sensor can be utilized for quantification of glucose with a wide linear range from 29.9 μM to 6.44 mM (R = 0.9937 with a low detection limit of 1.8 μM (S/N = 3 and a high sensitivity of 1997 μA/mM∙cm−2. It also exhibited good reproducibility as well as high selectivity.

A new luminol chemiluminescence sensor for glucose based on pH-dependent graphene oxide.

Science.gov (United States)

Hao, Minjia; Liu, Na; Ma, Zhanfang

2013-08-07

In this study, graphene oxide (GO) was found to catalyze the luminol-O2 reaction, which yielded a novel chemiluminescence (CL). Remarkably, the CL emission could be tuned by modulating the pH of the GO dispersion. Transmission electron microscopy, CL spectra, electron spin resonance spectra studies were carried out to investigate the CL mechanism. The results indicate that the CL emission was attributed to the intrinsic catalytic effect of GO acting as the radical generation proliferators and electron transfer accelerators. Based on the GO catalyzed luminol-O2 system, we successfully developed a new CL sensor to detect glucose. Under the optimized conditions, glucose could be assayed in the range of 0.05 mM to 5 mM with a detection limit of 0.044 mM. For the detection of clinical serum samples, it is well consistent with the data determined by commercially available method in hospital, indicating that the new CL method provides a possible application for the detection of glucose in clinical diagnostics.

Tattoo-based noninvasive glucose monitoring: a proof-of-concept study.

Science.gov (United States)

Bandodkar, Amay J; Jia, Wenzhao; Yardımcı, Ceren; Wang, Xuan; Ramirez, Julian; Wang, Joseph

2015-01-06

We present a proof-of-concept demonstration of an all-printed temporary tattoo-based glucose sensor for noninvasive glycemic monitoring. The sensor represents the first example of an easy-to-wear flexible tattoo-based epidermal diagnostic device combining reverse iontophoretic extraction of interstitial glucose and an enzyme-based amperometric biosensor. In-vitro studies reveal the tattoo sensor's linear response toward physiologically relevant glucose levels with negligible interferences from common coexisting electroactive species. The iontophoretic-biosensing tattoo platform is reduced to practice by applying the device on human subjects and monitoring variations in glycemic levels due to food consumption. Correlation of the sensor response with that of a commercial glucose meter underscores the promise of the tattoo sensor to detect glucose levels in a noninvasive fashion. Control on-body experiments demonstrate the importance of the reverse iontophoresis operation and validate the sensor specificity. This preliminary investigation indicates that the tattoo-based iontophoresis-sensor platform holds considerable promise for efficient diabetes management and can be extended toward noninvasive monitoring of other physiologically relevant analytes present in the interstitial fluid.

Functional expression of sodium-glucose transporters in cancer

Science.gov (United States)

Scafoglio, Claudio; Hirayama, Bruce A.; Kepe, Vladimir; Liu, Jie; Ghezzi, Chiara; Satyamurthy, Nagichettiar; Moatamed, Neda A.; Huang, Jiaoti; Koepsell, Hermann; Barrio, Jorge R.; Wright, Ernest M.

2015-01-01

Glucose is a major metabolic substrate required for cancer cell survival and growth. It is mainly imported into cells by facilitated glucose transporters (GLUTs). Here we demonstrate the importance of another glucose import system, the sodium-dependent glucose transporters (SGLTs), in pancreatic and prostate adenocarcinomas, and investigate their role in cancer cell survival. Three experimental approaches were used: (i) immunohistochemical mapping of SGLT1 and SGLT2 distribution in tumors; (ii) measurement of glucose uptake in fresh isolated tumors using an SGLT-specific radioactive glucose analog, α-methyl-4-deoxy-4-[18F]fluoro-d-glucopyranoside (Me4FDG), which is not transported by GLUTs; and (iii) measurement of in vivo SGLT activity in mouse models of pancreatic and prostate cancer using Me4FDG-PET imaging. We found that SGLT2 is functionally expressed in pancreatic and prostate adenocarcinomas, and provide evidence that SGLT2 inhibitors block glucose uptake and reduce tumor growth and survival in a xenograft model of pancreatic cancer. We suggest that Me4FDG-PET imaging may be used to diagnose and stage pancreatic and prostate cancers, and that SGLT2 inhibitors, currently in use for treating diabetes, may be useful for cancer therapy. PMID:26170283

Novel glucose biosensor based on a glassy carbon electrode modified with hollow gold nanoparticles and glucose oxidase

International Nuclear Information System (INIS)

Wang, W.; Ying, S.; Zhang, Z.; Huang, S.

2011-01-01

A novel glucose biosensor is presented as that based on a glassy carbon electrode modified with hollow gold nanoparticles (HGNs) and glucose oxidase. The sensor exhibits a better differential pulse voltammetric response towards glucose than the one based on conventional gold nanoparticles of the same size. This is attributed to the good biological conductivity and biocompatibility of HGNs. Under the optimal conditions, the sensor displays a linear range from 2.0 x 10 -6 to 4.6 x 10 -5 M of glucose, with a detection limit of 1.6 x 10 -6 M (S/N = 3). Good reproducibility, stability and no interference make this biosensor applicable to the determination of glucose in samples such as sports drinks. (author)

Glucose Monitoring System Based on Osmotic Pressure Measurements

Directory of Open Access Journals (Sweden)

Alexandra LEAL

2011-02-01

Full Text Available This paper presents the design and development of a prototype sensor unit for implementation in a long-term glucose monitoring system suitable for estimating glucose levels in people suffering from diabetes mellitus. The system utilizes osmotic pressure as the sensing mechanism and consists of a sensor prototype that is integrated together with a pre-amplifier and data acquisition unit for both data recording and processing. The sensor prototype is based on an embedded silicon absolute pressure transducer and a semipermeable nanoporous membrane that is enclosed in the sensor housing. The glucose monitoring system facilitates the integration of a low power microcontroller that is combined with a wireless inductive powered communication link. Experimental verification have proven that the system is capable of tracking osmotic pressure changes using albumin as a model compound, and thereby show a proof of concept for novel long term tracking of blood glucose from remote sensor nodes.

GOX-functionalized nanodiamond films for electrochemical biosensor

Energy Technology Data Exchange (ETDEWEB)

Villalba, Pedro [Department of Chemical and Biomedical Engineering, University of South Florida (United States); Departamento de Medicina, Universidad del Norte, Barranquilla (Colombia); Ram, Manoj K., E-mail: mkram@usf.edu [Department of Mechanical Engineering, University of South Florida, 4202 E Fowler Avenue, Tampa, FL, 33620-5350 (United States); Nanotechnology Research and Education Center, University of South Florida (United States); Gomez, Humberto [Department of Mechanical Engineering, University of South Florida, 4202 E Fowler Avenue, Tampa, FL, 33620-5350 (United States); Departamento de Medicina, Universidad del Norte, Barranquilla (Colombia); Kumar, Amrita [Department of Physiology, Emory University. Atlanta GA (United States); Bhethanabotla, Venkat [Department of Chemical and Biomedical Engineering, University of South Florida (United States); Kumar, Ashok [Department of Mechanical Engineering, University of South Florida, 4202 E Fowler Avenue, Tampa, FL, 33620-5350 (United States); Nanotechnology Research and Education Center, University of South Florida (United States)

2011-07-20

The importance of nanodiamond in biological and technological applications has been recognized recently, and applied in drug delivery, biochip, sensors and biosensors. Under this investigation, nanodiamond (ND) and nitrogen doped nanodiamond (NND) were deposited on n-type silicon films, and later functionalized with enzyme Glucose oxidase (GOX). The GOX functionalized doped and undoped ND films were characterized using combination of several techniques; i.e. FTIR spectroscopy, Raman spectroscopy, atomic force microscopy (AFM) and electrochemical techniques. ND/GOX and NND/GOX thin films on n-type silicon have been found to provide sensitive glucose sensor. GOX has been chosen as a model enzyme system to functionalize with ND at molecular level to understand the glucose biosensor. - Research highlights: {yields} Nanodiamond (ND) films were used as an enzyme electrode for glucose quantification. {yields} Electrochemical behavior of doped and intrinsic films was analyzed. {yields} Electrode demonstrates sensitivity to glucose concentration in dynamic condition. {yields} Linear behavior was observed upto 8mM before saturation condition.

GOX-functionalized nanodiamond films for electrochemical biosensor

International Nuclear Information System (INIS)

Villalba, Pedro; Ram, Manoj K.; Gomez, Humberto; Kumar, Amrita; Bhethanabotla, Venkat; Kumar, Ashok

2011-01-01

The importance of nanodiamond in biological and technological applications has been recognized recently, and applied in drug delivery, biochip, sensors and biosensors. Under this investigation, nanodiamond (ND) and nitrogen doped nanodiamond (NND) were deposited on n-type silicon films, and later functionalized with enzyme Glucose oxidase (GOX). The GOX functionalized doped and undoped ND films were characterized using combination of several techniques; i.e. FTIR spectroscopy, Raman spectroscopy, atomic force microscopy (AFM) and electrochemical techniques. ND/GOX and NND/GOX thin films on n-type silicon have been found to provide sensitive glucose sensor. GOX has been chosen as a model enzyme system to functionalize with ND at molecular level to understand the glucose biosensor. - Research highlights: → Nanodiamond (ND) films were used as an enzyme electrode for glucose quantification. → Electrochemical behavior of doped and intrinsic films was analyzed. → Electrode demonstrates sensitivity to glucose concentration in dynamic condition. → Linear behavior was observed upto 8mM before saturation condition.

A selective glucose sensor: the cooperative effect of monoboronic acid-modified poly(amidoamine) dendrimers.

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Tsai, Ching-Hua; Tang, Yi-Hsuan; Chen, Hui-Ting; Yao, Yi-Wen; Chien, Tun-Cheng; Kao, Chai-Lin

2018-05-01

Selective glucose binding was identified through five generations of monoboronic acid-functionalized PAMAM dendrimers. The best selectivity obtained when using G3 dendrimers (1b) generated 71.1, 94.9, and 1309 times stronger binding than when using galactose, fructose, and lactose, respectively. Further experiments using dendrimer analogues and glucose derivatives suggested that two nearby monoboronic acids cooperatively bound one glucose.

Nano-yarn carbon nanotube fiber based enzymatic glucose biosensor

International Nuclear Information System (INIS)

Zhu Zhigang; Burugapalli, Krishna; Moussy, Francis; Song, Wenhui; Li Yali; Zhong Xiaohua

2010-01-01

A novel brush-like electrode based on carbon nanotube (CNT) nano-yarn fiber has been designed for electrochemical biosensor applications and its efficacy as an enzymatic glucose biosensor demonstrated. The CNT nano-yarn fiber was spun directly from a chemical-vapor-deposition (CVD) gas flow reaction using a mixture of ethanol 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) concentrically compacted into multiple layers forming a nano-porous network structure. Cyclic voltammetry study revealed a superior electrocatalytic activity for CNT fiber compared to the traditional Pt-Ir coil electrode. The electrode end tip of the CNT fiber was freeze-fractured to obtain a unique brush-like nano-structure resembling a scale-down electrical 'flex', where glucose oxidase (GOx) enzyme was immobilized using glutaraldehyde crosslinking 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 against a standard reference electrode. The sensitivities, linear detection range and linearity for detecting glucose for the miniature CNT fiber electrode were better than that reported for a Pt-Ir coil electrode. Thermal annealing of the CNT fiber at 250 deg. C for 30 min prior to fabrication of the sensor resulted in a 7.5 fold increase in glucose sensitivity. The as-spun CNT fiber based glucose biosensor was shown to be stable for up to 70 days. In addition, gold coating of the electrode connecting end 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 demonstrated compared to a traditional Pt-Ir sensor.

Nano-yarn carbon nanotube fiber based enzymatic glucose biosensor

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Zhu, Zhigang; Song, Wenhui; Burugapalli, Krishna; Moussy, Francis; Li, Ya-Li; Zhong, Xiao-Hua

2010-04-01

A novel brush-like electrode based on carbon nanotube (CNT) nano-yarn fiber has been designed for electrochemical biosensor applications and its efficacy as an enzymatic glucose biosensor demonstrated. The CNT nano-yarn fiber was spun directly from a chemical-vapor-deposition (CVD) gas flow reaction using a mixture of ethanol 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) concentrically compacted into multiple layers forming a nano-porous network structure. Cyclic voltammetry study revealed a superior electrocatalytic activity for CNT fiber compared to the traditional Pt-Ir coil electrode. The electrode end tip of the CNT fiber was freeze-fractured to obtain a unique brush-like nano-structure resembling a scale-down electrical 'flex', where glucose oxidase (GOx) enzyme was immobilized using glutaraldehyde crosslinking 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 against a standard reference electrode. The sensitivities, linear detection range and linearity for detecting glucose for the miniature CNT fiber electrode were better than that reported for a Pt-Ir coil electrode. Thermal annealing of the CNT fiber at 250 °C for 30 min prior to fabrication of the sensor resulted in a 7.5 fold increase in glucose sensitivity. The as-spun CNT fiber based glucose biosensor was shown to be stable for up to 70 days. In addition, gold coating of the electrode connecting end 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 demonstrated compared to a traditional Pt-Ir sensor.

Construction and characterization of nonenzymatic glucose sensor from recycling of Co, Cu and Mn from spent batteries

International Nuclear Information System (INIS)

Selvatici, Livia Serra; Favalessa, Luiza Botan; Loureiro, Eduardo dos Santos; Dixini, Pedro Vitor Morbach; Freitas, Marcos Benedito Jose de; Celante, Vinicius Guilherme

2016-01-01

Full text: In this work, Co, Cu and MnO 2 films were synthesized from the electrochemical recycling of spent Li-ion and alkaline batteries and applied as non-enzymatic electrochemical sensors for glucose determination in aqueous solution. The batteries were dismantled, physically separated into different constituents and leached solution of acetic acid 3:1 v/v. The films were synthesized in potentiostatic condition with E =-0.90 V and fixed charge density of 10 C.cm -2 on glassy carbon substrate with area equal to 3.0 mm 2 . Measurements of X-ray diffraction showed the Co structures (111), Cu (101) and MnO 2 (110). By analysis of scanning electron microscopy, a homogeneous coating of the surface was observed without the presence of surface irregularities. For energy dispersive X-ray, Co, Cu, Mn and O were observed. These films were subsequently used in determining glucose in aqueous solution by measures of successive voltammetric cycles in solutions of concentration varying from 0.1 to 0.5 g/l. These solutions were related to anodic peak current (I peak ), relative oxidation of glucose in glucolactona, the concentration of the solution, obtaining a linear correlation coefficient of 0.989. The sensor stability was measured in 20 voltammetric cycles in each solution, obtaining a correlation coefficient equal to 0978, being stable in the measurements. (author)

Smart point-of-care systems for molecular diagnostics based on nanotechnology: whole blood glucose analysis

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Devadhasan, Jasmine P.; Kim, Sanghyo

2015-07-01

Complementary metal oxide semiconductor (CMOS) image sensors are received great attention for their high efficiency in biological applications. The present work describes a CMOS image sensor-based whole blood glucose monitoring system through a point-of-care (POC) approach. A simple poly-ethylene terephthalate (PET) film chip was developed to carry out the enzyme kinetic reaction at various concentrations of blood glucose. In this technique, assay reagent was adsorbed onto amine functionalized silica (AFSiO2) nanoparticles in order to achieve glucose oxidation on the PET film chip. The AFSiO2 nanoparticles can immobilize the assay reagent with an electrostatic attraction and eased to develop the opaque platform which was technically suitable chip to analyze by the camera module. The oxidized glucose then produces a green color according to the glucose concentration and is analyzed by the camera module as a photon detection technique. The photon number decreases with increasing glucose concentration. The simple sensing approach, utilizing enzyme immobilized AFSiO2 nanoparticle chip and assay detection method was developed for quantitative glucose measurement.

Glucose sensing based on Pt-MWCNT and MWCNT

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Aryasomayajula, Lavanya; Xie, Jining; Wang, Shouyan; Varadan, Vijay K.

2007-04-01

It is known that multi walled carbon nanotubes (MWCNTs) is an excellent materials for biosensing applications and with the introduction of Pt nanoparticles (Pt-MWCNTs) of about 3nm in diameter in MWCNTs greatly increases the current sensitivity and also the signal to noise ratio. We fabricated the CNT- based glucose sensor by immobilization the bio enzyme, glucose oxidase (GoX), on the Pt-MWCNT and electrode were prepared. The sensor has been tested effectively for both the abnormal blood glucose levels- greater than 6.9 mM and less than 3.5 mM which are the prediabetic and diabetic glucose levels, respectively. The current signal obtained from the Pt-MWCNT was much higher compared to the MWCNT based sensors.

Blood glucose level reconstruction as a function of transcapillary glucose transport.

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Koutny, Tomas

2014-10-01

A diabetic patient occasionally undergoes a detailed monitoring of their glucose levels. Over the course of a few days, a monitoring system provides a detailed track of their interstitial fluid glucose levels measured in their subcutaneous tissue. A discrepancy in the blood and interstitial fluid glucose levels is unimportant because the blood glucose levels are not measured continuously. Approximately five blood glucose level samples are taken per day, and the interstitial fluid glucose level is usually measured every 5min. An increased frequency of blood glucose level sampling would cause discomfort for the patient; thus, there is a need for methods to estimate blood glucose levels from the glucose levels measured in subcutaneous tissue. The Steil-Rebrin model is widely used to describe the relationship between blood and interstitial fluid glucose dynamics. However, we measured glucose level patterns for which the Steil-Rebrin model does not hold. Therefore, we based our research on a different model that relates present blood and interstitial fluid glucose levels to future interstitial fluid glucose levels. Using this model, we derived an improved model for calculating blood glucose levels. In the experiments conducted, this model outperformed the Steil-Rebrin model while introducing no additional requirements for glucose sample collection. In subcutaneous tissue, 26.71% of the calculated blood glucose levels had absolute values of relative differences from smoothed measured blood glucose levels less than or equal to 5% using the Steil-Rebrin model. However, the same difference interval was encountered in 63.01% of the calculated blood glucose levels using the proposed model. In addition, 79.45% of the levels calculated with the Steil-Rebrin model compared with 95.21% of the levels calculated with the proposed model had 20% difference intervals. Copyright © 2014 Elsevier Ltd. All rights reserved.

Photo-acoustic sensor based on an inexpensive piezoelectric film transducer and an amplitude-stabilized single-mode external cavity diode laser for in vitro measurements of glucose concentration

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Bayrakli, Ismail; Erdogan, Yasar Kemal

2018-06-01

The present paper focuses on development of a compact photo-acoustic sensor using inexpensive components for glucose analysis. An amplitude-stabilized wavelength-tunable single-mode external cavity diode laser operating around 1050 nm was realized and characterized for the use of laser beam as an excitation light source. In the established setup, a fine tuning range of 9 GHz was achieved. The glucose solution was obtained by diluting D-glucose in sterile water. The acoustic signal generated by the optical excitation was detected via a chip piezoelectric film transducer. A detection limit of 50 mM (900 mg/dl) was achieved. The device may be of great interest for its applications in medicine and health monitoring. The sensor is promising for non-invasive in vivo glucose measurements from interstitial fluid.

Glucose variability negatively impacts long-term functional outcome in patients with traumatic brain injury.

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Matsushima, Kazuhide; Peng, Monica; Velasco, Carlos; Schaefer, Eric; Diaz-Arrastia, Ramon; Frankel, Heidi

2012-04-01

Significant glycemic excursions (so-called glucose variability) affect the outcome of generic critically ill patients but has not been well studied in patients with traumatic brain injury (TBI). The purpose of this study was to evaluate the impact of glucose variability on long-term functional outcome of patients with TBI. A noncomputerized tight glucose control protocol was used in our intensivist model surgical intensive care unit. The relationship between the glucose variability and long-term (a median of 6 months after injury) functional outcome defined by extended Glasgow Outcome Scale (GOSE) was analyzed using ordinal logistic regression models. Glucose variability was defined by SD and percentage of excursion (POE) from the preset range glucose level. A total of 109 patients with TBI under tight glucose control had long-term GOSE evaluated. In univariable analysis, there was a significant association between lower GOSE score and higher mean glucose, higher SD, POE more than 60, POE 80 to 150, and single episode of glucose less than 60 mg/dL but not POE 80 to 110. After adjusting for possible confounding variables in multivariable ordinal logistic regression models, higher SD, POE more than 60, POE 80 to 150, and single episode of glucose less than 60 mg/dL were significantly associated with lower GOSE score. Glucose variability was significantly associated with poorer long-term functional outcome in patients with TBI as measured by the GOSE score. Well-designed protocols to minimize glucose variability may be key in improving long-term functional outcome. Copyright © 2012 Elsevier Inc. All rights reserved.

An Enzymatic Glucose Sensor Composed of Carbon-Coated Nano Tin Sulfide

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Ren-Jei Chung

2017-02-01

Full Text Available In this study, a biosensor, based on a glucose oxidase (GOx immobilized, carbon-coated tin sulfide (SnS assembled on a glass carbon electrode (GCE was developed, and its direct electrochemistry was investigated. The carbon coated SnS (C-SnS nanoparticle was prepared through a simple two-step process, using hydrothermal and chemical vapor deposition methods. The large reactive surface area and unique electrical potential of C-SnS could offer a favorable microenvironment for facilitating electron transfer between enzymes and the electrode surface. The structure and sensor ability of the proposed GOx/C-SnS electrode were characterized using scanning electron microscopy (SEM, X-ray diffraction (XRD, Raman spectroscopy, UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR, and cyclic voltammetry study (CV.

The flavonoid-rich fraction of Coreopsis tinctoria promotes glucose tolerance regain through pancreatic function recovery in streptozotocin-induced glucose-intolerant rats.

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Dias, Teresa; Bronze, Maria Rosário; Houghton, Peter J; Mota-Filipe, Hélder; Paulo, Alexandra

2010-11-11

Infusions of Coreopsis tinctoria Nutt. flowering tops have been used traditionally in Portugal to control hyperglycaemia and a previous study revealed that daily administration of the infusion during a 3-week period promoted the recovery of glucose tolerance by a mechanism different from inhibition of glucose absorption and direct promotion of insulin secretion. We know report the study of the ethyl acetate fraction of Coreopsis tinctoria flowers infusion aiming to confirm flavonoids as bioactive metabolites. To give one step forward into the antihyperglycaemic mechanism of action of this traditionally used plant we also studied the activity of Coreopsis tinctoria flavonoids on the pancreatic function of glucose-intolerant rats. A standard antioxidant, Trolox, was also studied for comparative purposes as the antioxidant mechanism has been frequently purposed as one of the mechanisms mediating antihyperglycaemic effects of flavonoid-rich extracts. Thirteen compounds, mainly of flavanone and chalcone flavonoidal type, have been identified in this fraction by HPLC-DAD-ESI-MS/MS, and the major one (marein) quantified by HPLC-UV. The fraction (125 mg containing 20 mg of marein/kg b.w.) and Trolox (50 mg/kg b.w.) were administered daily by oral gavage to normal and STZ (40 mg/kg b.w.)-induced glucose-intolerant Wistar rats for 3 weeks. Blood glucose levels were measured weekly by Oral Glucose Tolerance Test. Pancreatic function was evaluated by plasma lipase of treated and non-treated glucose-tolerant and- intolerant rats after the 3-week treatment period. After 2 weeks oral treatment with Coreopsis tinctoria AcOEt fraction the animals were no longer glucose-intolerant, an effect maintained over the remaining experimental period. Additionally, plasma lipase values of glucose-intolerant animals treated with the AcOEt fraction (13.5 ± 0.84 U/L) showed a clear reduction when compared with the glucose-intolerant group (34.60 ± 1.76 U/L; P<0.001) and normoglycaemic control

Accuracy of flash glucose monitoring and continuous glucose monitoring technologies: Implications for clinical practice.

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Ajjan, Ramzi A; Cummings, Michael H; Jennings, Peter; Leelarathna, Lalantha; Rayman, Gerry; Wilmot, Emma G

2018-02-01

Continuous glucose monitoring and flash glucose monitoring technologies measure glucose in the interstitial fluid and are increasingly used in diabetes care. Their accuracy, key to effective glycaemic management, is usually measured using the mean absolute relative difference of the interstitial fluid sensor compared to reference blood glucose readings. However, mean absolute relative difference is not standardised and has limitations. This review aims to provide a consensus opinion on assessing accuracy of interstitial fluid glucose sensing technologies. Mean absolute relative difference is influenced by glucose distribution and rate of change; hence, we express caution on the reliability of comparing mean absolute relative difference data from different study systems and conditions. We also review the pitfalls associated with mean absolute relative difference at different glucose levels and explore additional ways of assessing accuracy of interstitial fluid devices. Importantly, much data indicate that current practice of assessing accuracy of different systems based on individualised mean absolute relative difference results has limitations, which have potential clinical implications. Healthcare professionals must understand the factors that influence mean absolute relative difference as a metric for accuracy and look at additional assessments, such as consensus error grid analysis, when evaluating continuous glucose monitoring and flash glucose monitoring systems in diabetes care. This in turn will ensure that management decisions based on interstitial fluid sensor data are both effective and safe.

Glucose regulation and cognitive function after bariatric surgery.

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Galioto, Rachel; Alosco, Michael L; Spitznagel, Mary Beth; Strain, Gladys; Devlin, Michael; Cohen, Ronald; Crosby, Ross D; Mitchell, James E; Gunstad, John

2015-01-01

Obesity is associated with cognitive impairment, and bariatric surgery has been shown to improve cognitive functioning. Rapid improvements in glycemic control are common after bariatric surgery and likely contribute to these cognitive gains. We examined whether improvements in glucose regulation are associated with better cognitive function following bariatric surgery. A total of 85 adult bariatric surgery patients underwent computerized cognitive testing and fasting blood draw for glucose, insulin, and glycated hemoglobin (HbA1c) at baseline and 12 months postoperatively. Significant improvements in both cognitive function and glycemic control were observed among patients. After controlling for baseline factors, 12-month homeostatic model assessment of insulin resistance HOMA-IR predicted 12-month digits backward (β = -.253, p cognitive flexibility improved. Decreases in HbA1c were not associated with postoperative cognitive improvements. After controlling for baseline cognitive test performance, changes in body mass index (BMI) were also not associated with 12-month cognitive function. Small effects of improved glycemic control on improved aspects of attention and executive function were observed following bariatric surgery among severely obese individuals. Future research is needed to identify the underlying mechanisms for the neurocognitive benefits of these procedures.

Noninvasive biosensor and wireless interrogating system for glucose in blood

Science.gov (United States)

Varadan, Vijay K.; Whitchurch, Ashwin K.; Sarukesi, K.

2003-07-01

Hypoglycemia-abnormal decrease in blood sugar-is a major obstacle in the management of diabetes and prevention of long-term complications, and it may impose serious effects on the brain, including impairment of memory and other cognitive functions. This paper presents the development of a non-invasive sensor with miniaturized telemetry device in a wrist-watch for monitoring glucose concentration in blood. The sensor concept is based on optical chirality of glucose level in the interstitial fluid. The wrist watch consists of a laser power source of the wavelength compatible with the glucose. A nanofilm with specific chirality is placed at the bottom of the watch. The light then passes through the film and illuminates a small area on the skin. It has been documented that there is certain concentration of sugar level is taken by the intertitial fluid from the blood stream and deposit a portion of it at the dead skin. The wrist-watch when in contact with the outer skin of the human will thus monitor the glucose concentration. A wireless monitoring system in the watch then downloads the data from the watch to a Palm or a laptop computer.

Vertically Aligned Carbon Nanofiber based Biosensor Platform for Glucose Sensor

Energy Technology Data Exchange (ETDEWEB)

Al Mamun, Khandaker A.; Tulip, Fahmida S.; MacArthur, Kimberly; McFarlane, Nicole; Islam, Syed K.; Hensley, Dale

2014-03-01

Vertically aligned carbon nanofibers (VACNFs) have recently become an important tool for biosensor design. Carbon nanofibers (CNF) have excellent conductive and structural properties with many irregularities and defect sites in addition to exposed carboxyl groups throughout their surfaces. These properties allow a better immobilization matrix compared to carbon nanotubes and offer better resolution when compared with the FET-based biosensors. VACNFs can be deterministically grown on silicon substrates allowing optimization of the structures for various biosensor applications. Two VACNF electrode architectures have been employed in this study and a comparison of their performances has been made in terms of sensitivity, sensing limitations, dynamic range, and response time. The usage of VACNF platform as a glucose sensor has been verified in this study by selecting an optimum architecture based on the VACNF forest density. Read More: http://www.worldscientific.com/doi/abs/10.1142/S0129156414500062

The acute effect of coffee on endothelial function and glucose metabolism following a glucose load in healthy human volunteers.

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Boon, Evan A J; Croft, Kevin D; Shinde, Sujata; Hodgson, Jonathan M; Ward, Natalie C

2017-09-20

A diet rich in plant polyphenols has been suggested to reduce the incidence of cardiovascular disease and type 2 diabetes mellitus, in part, via improvements in endothelial function. Coffee is a rich source of phenolic compounds including the phenolic acid, chlorogenic acid (CGA). The aim of the study was to investigate the effect of coffee as a whole beverage on endothelial function, blood pressure and blood glucose concentration. Twelve healthy men and women were recruited to a randomised, placebo-controlled, cross-over study, with three treatments tested: (i) 18 g of ground caffeinated coffee containing 300 mg CGA in 200 mL of hot water, (ii) 18 g of decaffeinated coffee containing 287 mg CGA in 200 mL of hot water, and (iii) 200 mL of hot water (control). Treatment beverages were consumed twice, two hours apart, with the second beverage consumed simultaneously with a 75 g glucose load. Blood pressure was recorded and the finger prick glucose test was performed at time = 0 and then every 30 minutes up to 2 hours. Endothelial function, assessed using flow-mediated dilatation (FMD) of the brachial artery, was measured at 1 hour and a blood sample taken at 2 hours to measure plasma nitrate/nitrite and 5-CGA concentrations. The FMD response was significantly higher in the caffeinated coffee group compared to both decaffeinated coffee and water groups (P coffee and water. Blood glucose concentrations and blood pressure were not different between the three treatment groups. In conclusion, the consumption of caffeinated coffee resulted in a significant improvement in endothelial function, but there was no evidence for benefit regarding glucose metabolism or blood pressure. Although the mechanism has yet to be elucidated the results suggest that coffee as a whole beverage may improve endothelial function, or that caffeine is the component of coffee responsible for improving FMD.

Detection of saliva-range glucose concentrations using organic thin-film transistors

International Nuclear Information System (INIS)

Elkington, D.; Belcher, W. J.; Dastoor, P. C.; Zhou, X. J.

2014-01-01

We describe the development of a glucose sensor through direct incorporation of an enzyme (glucose oxidase) into the gate of an organic thin film transistor (OTFT). We show that glucose diffusion is the key determinant of the device response time and present a mechanism of glucose sensing in these devices that involves protonic doping of the transistor channel via enzymatic oxidation of glucose. The integrated OTFT sensor is sensitive across 4 decades of glucose concentration; a range that encompasses both the blood and salivary glucose concentration levels. As such, this work acts as a proof-of-concept for low-cost printed biosensors for salivary glucose.

Detection of saliva-range glucose concentrations using organic thin-film transistors

Energy Technology Data Exchange (ETDEWEB)

Elkington, D.; Belcher, W. J.; Dastoor, P. C.; Zhou, X. J. [Centre for Organic Electronics, University of Newcastle, Callaghan, New South Wales 2308 (Australia)

2014-07-28

We describe the development of a glucose sensor through direct incorporation of an enzyme (glucose oxidase) into the gate of an organic thin film transistor (OTFT). We show that glucose diffusion is the key determinant of the device response time and present a mechanism of glucose sensing in these devices that involves protonic doping of the transistor channel via enzymatic oxidation of glucose. The integrated OTFT sensor is sensitive across 4 decades of glucose concentration; a range that encompasses both the blood and salivary glucose concentration levels. As such, this work acts as a proof-of-concept for low-cost printed biosensors for salivary glucose.

Accuracy of subcutaneous continuous glucose monitoring in critically ill adults: improved sensor performance with enhanced calibrations.

Science.gov (United States)

Leelarathna, Lalantha; English, Shane W; Thabit, Hood; Caldwell, Karen; Allen, Janet M; Kumareswaran, Kavita; Wilinska, Malgorzata E; Nodale, Marianna; Haidar, Ahmad; Evans, Mark L; Burnstein, Rowan; Hovorka, Roman

2014-02-01

Accurate real-time continuous glucose measurements may improve glucose control in the critical care unit. We evaluated the accuracy of the FreeStyle(®) Navigator(®) (Abbott Diabetes Care, Alameda, CA) subcutaneous continuous glucose monitoring (CGM) device in critically ill adults using two methods of calibration. In a randomized trial, paired CGM and reference glucose (hourly arterial blood glucose [ABG]) were collected over a 48-h period from 24 adults with critical illness (mean±SD age, 60±14 years; mean±SD body mass index, 29.6±9.3 kg/m(2); mean±SD Acute Physiology and Chronic Health Evaluation score, 12±4 [range, 6-19]) and hyperglycemia. In 12 subjects, the CGM device was calibrated at variable intervals of 1-6 h using ABG. In the other 12 subjects, the sensor was calibrated according to the manufacturer's instructions (1, 2, 10, and 24 h) using arterial blood and the built-in point-of-care glucometer. In total, 1,060 CGM-ABG pairs were analyzed over the glucose range from 4.3 to 18.8 mmol/L. Using enhanced calibration median (interquartile range) every 169 (122-213) min, the absolute relative deviation was lower (7.0% [3.5, 13.0] vs. 12.8% [6.3, 21.8], P<0.001), and the percentage of points in the Clarke error grid Zone A was higher (87.8% vs. 70.2%). Accuracy of the Navigator CGM device during critical illness was comparable to that observed in non-critical care settings. Further significant improvements in accuracy may be obtained by frequent calibrations with ABG measurements.

Mesoporous Nickel Oxide (NiO) Nanopetals for Ultrasensitive Glucose Sensing

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Mishra, Suryakant; Yogi, Priyanka; Sagdeo, P. R.; Kumar, Rajesh

2018-01-01

Glucose sensing properties of mesoporous well-aligned, dense nickel oxide (NiO) nanostructures (NSs) in nanopetals (NPs) shape grown hydrothermally on the FTO-coated glass substrate has been demonstrated. The structural study based investigations of NiO-NPs has been carried out by X-ray diffraction (XRD), electron and atomic force microscopies, energy dispersive X-ray (EDX), and X-ray photospectroscopy (XPS). Brunauer-Emmett-Teller (BET) measurements, employed for surface analysis, suggest NiO's suitability for surface activity based glucose sensing applications. The glucose sensor, which immobilized glucose on NiO-NPs@FTO electrode, shows detection of wide range of glucose concentrations with good linearity and high sensitivity of 3.9 μA/μM/cm2 at 0.5 V operating potential. Detection limit of as low as 1 μΜ and a fast response time of less than 1 s was observed. The glucose sensor electrode possesses good anti-interference ability, stability, repeatability & reproducibility and shows inert behavior toward ascorbic acid (AA), uric acid (UA) and dopamine acid (DA) making it a perfect non-enzymatic glucose sensor.

Functional Characterization of MODY2 Mutations Highlights the Importance of the Fine-Tuning of Glucokinase and Its Role in Glucose Sensing

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García-Herrero, Carmen-María; Rubio-Cabezas, Oscar; Azriel, Sharona; Gutierrez-Nogués, Angel; Aragonés, Angel; Vincent, Olivier; Campos-Barros, Angel; Argente, Jesús; Navas, María-Angeles

2012-01-01

Glucokinase (GK) acts as a glucose sensor in the pancreatic beta-cell and regulates insulin secretion. Heterozygous mutations in the human GK-encoding GCK gene that reduce the activity index increase the glucose-stimulated insulin secretion threshold and cause familial, mild fasting hyperglycaemia, also known as Maturity Onset Diabetes of the Young type 2 (MODY2). Here we describe the biochemical characterization of five missense GK mutations: p.Ile130Thr, p.Asp205His, p.Gly223Ser, p.His416Arg and p.Ala449Thr. The enzymatic analysis of the corresponding bacterially expressed GST-GK mutant proteins show that all of them impair the kinetic characteristics of the enzyme. In keeping with their position within the protein, mutations p.Ile130Thr, p.Asp205His, p.Gly223Ser, and p.His416Arg strongly decrease the activity index of GK, affecting to one or more kinetic parameters. In contrast, the p.Ala449Thr mutation, which is located in the allosteric activator site, does not affect significantly the activity index of GK, but dramatically modifies the main kinetic parameters responsible for the function of this enzyme as a glucose sensor. The reduced Kcat of the mutant (3.21±0.28 s−1 vs 47.86±2.78 s−1) is balanced by an increased glucose affinity (S0.5 = 1.33±0.08 mM vs 7.86±0.09 mM) and loss of cooperativity for this substrate. We further studied the mechanism by which this mutation impaired GK kinetics by measuring the differential effects of several competitive inhibitors and one allosteric activator on the mutant protein. Our results suggest that this mutation alters the equilibrium between the conformational states of glucokinase and highlights the importance of the fine-tuning of GK and its role in glucose sensing. PMID:22291974

Physical activity energy expenditure vs cardiorespiratory fitness level in impaired glucose metabolism

DEFF Research Database (Denmark)

Lidegaard, Lærke P; Hansen, Anne-Louise Smidt; Johansen, Nanna B

2015-01-01

Aim/hypothesis: Little is known about the relative roles of physical activity energy expenditure (PAEE) and cardiorespiratory fitness (CRF) as determinants of glucose regulation. The aim of this study was to examine the associations of PAEE and CRF with markers of glucose metabolism, and to test...... the hypothesis that CRF modifies the association between PAEE and glucose metabolism. Methods: We analysed cross-sectional data from 755 adults from the Danish ADDITION-PRO study. On the basis of OGTT results, participants without known diabetes were classified as having normal glucose tolerance, isolated...... impaired fasting glycaemia (i-IFG), isolated impaired glucose tolerance (i-IGT), combined IFG + IGT or screen-detected diabetes mellitus. Markers of insulin sensitivity and beta cell function were determined. PAEE was measured using a combined heart rate and movement sensor. CRF (maximal oxygen uptake...

A novel glucose biosensor based on phosphonic acid-functionalized silica nanoparticles for sensitive detection of glucose in real samples

International Nuclear Information System (INIS)

Zhao, Wenbo; Fang, Yi; Zhu, Qinshu; Wang, Kuai; Liu, Min; Huang, Xiaohua; Shen, Jian

2013-01-01

An effective strategy for preparation amperometric biosensor by using the phosphonic acid-functionalized silica nanoparticles (PFSi NPs) as special modified materials is proposed. In such a strategy, glucose oxidase (GOD) was selected as model protein to fabricate glucose biosensor in the presence of phosphonic acid-functionalized silica nanoparticles (PFSi NPs). The PFSi NPs were first modified on the surface of glassy carbon (GC) electrode, then, GOD was adsorbed onto the PFSi NPs film by drop-coating. The PFSi NPs were characterized by transmission electron microscopy (TEM) and nuclear magnetic resonance (NMR) spectra. The interaction of PFSi NPs with GOD was investigated by the circular dicroism spectroscopy (CD). The results showed PFSi NPs could essentially maintain the native conformation of GOD. The direct electron transfer of GOD on (PFSi NPs)/GCE electrode exhibited excellent electrocatalytic activity for the oxidation of glucose. The proposed biosensor modified with PFSi NPs displayed a fast amperometric response (5 s) to glucose, a good linear current–time relation over a wide range of glucose concentrations from 5.00 × 10 −4 to 1.87 × 10 −1 M, and a low detection limit of 2.44 × 10 −5 M (S/N = 3). Moreover, the biosensor can be used for assessment of the concentration of glucose in many real samples (relative error < 3%). The GOD biosensor modified with PFSi NPs will have essential meaning and practical application in future that attributed to the simple method of fabrication and good performance

Impaired insulin secretion and glucose intolerance in synaptotagmin-7 null mutant mice

DEFF Research Database (Denmark)

Gustavsson, Natalia; Lao, Ye; Maximov, Anton

2008-01-01

and insulin release. Here, we show that synaptotagmin-7 is required for the maintenance of systemic glucose tolerance and glucose-stimulated insulin secretion. Mutant mice have normal insulin sensitivity, insulin production, islet architecture and ultrastructural organization, and metabolic and calcium...... secretion in pancreatic beta-cells. Of these other synaptotagmins, synaptotagmin-7 is one of the most abundant and is present in pancreatic beta-cells. To determine whether synaptotagmin-7 regulates Ca(2+)-dependent insulin secretion, we analyzed synaptotagmin-7 null mutant mice for glucose tolerance...... responses but exhibit impaired glucose-induced insulin secretion, indicating a calcium-sensing defect during insulin-containing secretory granule exocytosis. Taken together, our findings show that synaptotagmin-7 functions as a positive regulator of insulin secretion and may serve as a calcium sensor...

Mediatorless amperometric bienzyme glucose biosensor based on horseradish peroxidase and glucose oxidase cross-linked to multiwall carbon nanotubes

International Nuclear Information System (INIS)

Xu, Shuxia; Zhou, Shiyi; Zhang, Xinfeng; Qi, Honglan; Zhang, Chengxiao

2014-01-01

We report on a bienzyme-channeling sensor for sensing glucose without the aid of mediator. It was fabricated by cross-linking horseradish peroxidase (HRP) and glucose oxidase (GOx) on a glassy carbon electrode modified with multiwalled carbon nanotubes (MWNTs). The bienzyme was cross-linked with the MWNTs by glutaraldehyde and bovine serum albumin. The MWNTs were employed to accelerate the electron transfer between immobilized HRP and electrode. Glucose was sensed by amperometric reduction of enzymatically generated H 2 O 2 at an applied voltage of −50 mV (vs. Ag/AgCl). Factors influencing the preparation and performance of the bienzyme electrode were investigated in detail. The biosensor exhibited a fast and linear response to glucose in the concentration range from 0.4 to 15 mM, with a detection limit of 0.4 mM. The sensor exhibited good selectivity and durability, with a long-term relative standard deviation of <5 %. Analysis of glucose-spiked human serum samples yielded recoveries between 96 and 101 %. (author)

Novel synthesis and characterization of Ag@TiO2 core shell nanostructure for non-enzymatic glucose sensor

Science.gov (United States)

T, Dayakar; Venkateswara Rao, K.; Vinodkumar, M.; Bikshalu, K.; Chakradhar, B.; Ramachandra Rao, K.

2018-03-01

Ag@TiO2 core-shell nano composite (ATCSNC) were synthesized by using Ocimum tenuiflorum leaves extract through a simple one-step hydrothermal route for Non-enzymatic glucose sensing material. The prepared NCs were characterized and found high crystallinity, red shift absorbance, interface-bonding parameters, rough surface and network like microstructure through XRD, Uv-vis, FTIR, SEM, and TEM. The prepared ATCSNC have been used for fabrication of glassy carbon electrode (GCE) and the same was applied to test its electro catalytic activity of glucose in 0.1 M NaOH. The promising results were recorded for ATCSNC/GCE with a high sensitivity (1968.72 μAm M-1cm-2), wide linear range (1 μM-8.1 mM), good response time (3 s), and excellent low detection limit (0.19 μM, S/N = 3). Furthermore, the designed sensor exhibits admirable stability and reproducibility, as well as attractive achievability for real sample analysis. As such, the proposed ATCSNC could be highly beneficial in the development of sustainable and eco-friendly glucose sensing devices.

Dynamic Sensor Management Algorithm Based on Improved Efficacy Function

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TANG Shujuan

2016-01-01

Full Text Available A dynamic sensor management algorithm based on improved efficacy function is proposed to solve the multi-target and multi-sensory management problem. The tracking task precision requirements (TPR, target priority and sensor use cost were considered to establish the efficacy function by weighted sum the normalized value of the three factors. The dynamic sensor management algorithm was accomplished through control the diversities of the desired covariance matrix (DCM and the filtering covariance matrix (FCM. The DCM was preassigned in terms of TPR and the FCM was obtained by the centralized sequential Kalman filtering algorithm. The simulation results prove that the proposed method could meet the requirements of desired tracking precision and adjust sensor selection according to target priority and cost of sensor source usage. This makes sensor management scheme more reasonable and effective.

Functional CuO Microstructures for Glucose Sensing

Science.gov (United States)

Ali, Gulzar; Tahira, Aneela; Mallah, Arfana Begum; Mallah, Sarfraz Ahmed; Ibupoto, Akila; Khand, Aftab Ahmed; Baradi, Waryani; Willander, Magnus; Yu, Cong; Ibupoto, Zafar Hussain

2018-02-01

CuO microstructures are produced in the presence of water-soluble amino acids by hydrothermal method. The used amino acids include isoleucine, alpha alanine, and arginine as a soft template and are used for tuning the morphology of CuO nanostructures. The crystalline and morphological investigations were carried out by x-ray diffraction (XRD) and scanning electron microscopy techniques. The XRD study has shown that CuO material obtained in the presence of different amino acids is of high purity and all have the same crystal phase. The CuO microstructures prepared in the presence of arginine were used for the development of sensitive and selective glucose biosensor. The linear range for the glucose detection are from 0.001 mM to 30 mM and limit of detection was found to be 0.0005 mM. The sensitivity was estimated around 77 mV/decade. The developed biosensor is highly selective, sensitive, stable and reproducible. The glucose biosensor was used for the determination of real human blood samples and the obtained results are satisfactory. The CuO material is functional therefore can be capitalized in wide range of applications such as lithium ion batteries, all oxide solar cells and supercapacitors.

Elevated 1-hour postload plasma glucose levels identify subjects with normal glucose tolerance but impaired β-cell function, insulin resistance, and worse cardiovascular risk profile: the GENFIEV study.

Science.gov (United States)

Bianchi, Cristina; Miccoli, Roberto; Trombetta, Maddalena; Giorgino, Francesco; Frontoni, Simona; Faloia, Emanuela; Marchesini, Giulio; Dolci, Maria A; Cavalot, Franco; Cavallo, Gisella; Leonetti, Frida; Bonadonna, Riccardo C; Del Prato, Stefano

2013-05-01

In subjects with normal glucose tolerance (NGT) 1-hour postload plasma glucose (1-h oral glucose tolerance test [OGTT]) of >155 mg/dL predicts type 2 diabetes (T2DM) and is associated with subclinical atherosclerosis. The purpose of this study was to evaluate β-cell function, insulin resistance, and cardiovascular risk profile in subjects with NGT with a 1-h OGTT glucose of >155 mg/dL. The GENFIEV (Genetics, PHYsiopathology, and Evolution of Type 2 diabetes) study is a multicenter study recruiting individuals at high risk of T2DM. A total of 926 subjects underwent a 75-g OGTT for assessment of plasma glucose and C-peptide for mathematical modeling of β-cell function (derivative and proportional control). Fasting insulin, lipid profile, and clinical parameters were determined as well. A 1-hour OGTT glucose of >155 mg/dL was found in 39% of subjects with NGT, 76% with impaired fasting glucose (IFG), 90% with impaired glucose tolerance (IGT), and 99% and 98% with IFG + IGT or newly diagnosed T2DM, respectively. Among subjects with NGT (n = 474), those with 1-hour OGTT glucose of >155 mg/dL were more insulin-resistant and had worse β-cell function than those with 1-hour OGTT glucose of ≤155 mg/dL. Moreover, glycosylated hemoglobin, blood pressure, low-density lipoprotein cholesterol, and triglycerides were higher in subjects with NGT with 1-hour OGTT glucose of >155 mg/dL, whereas high-density lipoprotein cholesterol was lower compared with that in subjects with NGT with 1-hour OGTT glucose of ≤155 mg/dL. Compared with subjects with IGT, those with NGT with 1-hour OGTT glucose of >155 mg/dL had comparable cardiovascular risk profile and insulin resistance but slightly better β-cell function. Among subjects with NGT, those with 1-hour OGTT glucose of >155 mg/dL showed lower insulin sensitivity, impaired β-cell function, and worse cardiovascular risk profile and therefore are at greater risk of developing T2DM and cardiovascular disease.

Investigation of the Influence of the As-Grown ZnO Nanorods and Applied Potentials on an Electrochemical Sensor for In-Vitro Glucose Monitoring

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Mohammed Marie

2017-01-01

Full Text Available The influence of the as-grown zinc oxide nanorods (ZnO NRs on the fabricated electrochemical sensor for in vitro glucose monitoring were investigated. A direct growth of ZnO NRs was performed on the Si/SiO2/Au electrode, using hydrothermal and sol-gel techniques at low temperatures. The structure, consisting of a Si/SiO2/Au/GOx/Nafion membrane, was considered as a baseline, and it was tested under several applied potential 0.1–0.8 V. The immobilized working electrode, with GOx and a nafion membrane, was characterized amperometrically using a source meter Keithely 2410, and an electrochemical impedance Gamry potentiostat. The sensor exhibited the following: a high sensitivity of ~0.468 mA/cm2 mM, a low detection limit in the order of 166.6 µM, and a fast and sharp response time of around 2 s. The highest sensitivity and the lowest limit of detection were obtained at 0.4 volt, after the growth of ZnO NRs. The highest net sensitivity was obtained after subtracting the sensitivity of the baseline, and it was in the order of 0.315 mA/cm2·mM. The device was tested with a range of glucose concentrations from 1–10 mM, showing a linear line from 3–8 mM, and the device was saturated after exceeding high concentrations of glucose. Such devices can be used for in vitro glucose monitoring, since glucose changes can be accurately detected.

Functional MRI of human hypothalamic responses following glucose ingestion

NARCIS (Netherlands)

Smeets, P.A.M.; Graaf, C. de; Stafleu, A.; Osch, M.J.P. van; Grond, J. van der

2005-01-01

The hypothalamus is intimately involved in the regulation of food intake, integrating multiple neural and hormonal signals. Several hypothalamic nuclei contain glucose-sensitive neurons, which play a crucial role in energy homeostasis. Although a few functional magnetic resonance imaging (fMRI)

Non-Enzymatic Glucose Sensing Using Carbon Quantum Dots Decorated with Copper Oxide Nanoparticles

Directory of Open Access Journals (Sweden)

Houcem Maaoui

2016-10-01

Full Text Available Perturbations in glucose homeostasis is critical for human health, as hyperglycemia (defining diabetes leads to premature death caused by macrovascular and microvascular complications. However, the simple and accurate detection of glucose in the blood at low cost remains a challenging task, although it is of great importance for the diagnosis and therapy of diabetic patients. In this work, carbon quantum dots decorated with copper oxide nanostructures (CQDs/Cu2O are prepared by a simple hydrothermal approach, and their potential for electrochemical non-enzymatic glucose sensing is evaluated. The proposed sensor exhibits excellent electrocatalytic activity towards glucose oxidation in alkaline solutions. The glucose sensor is characterized by a wide concentration range from 6 µM to 6 mM, a sensitivity of 2.9 ± 0.2 µA·µM−1·cm−2, and a detection limit of 6 µM at a signal-to-noise ratio S/N = 3. The sensors are successfully applied for glucose determination in human serum samples, demonstrating that the CQDs/Cu2O-based glucose sensor satisfies the requirements of complex sample detection with adapted potential for therapeutic diagnostics.

The Performance and Usability of a Factory-Calibrated Flash Glucose Monitoring System.

Science.gov (United States)

Bailey, Timothy; Bode, Bruce W; Christiansen, Mark P; Klaff, Leslie J; Alva, Shridhara

2015-11-01

The purpose of the study was to evaluate the performance and usability of the FreeStyle(®) Libre™ Flash glucose monitoring system (Abbott Diabetes Care, Alameda, CA) for interstitial glucose results compared with capillary blood glucose results. Seventy-two study participants with type 1 or type 2 diabetes were enrolled by four U.S. clinical sites. A sensor was inserted on the back of each upper arm for up to 14 days. Three factory-only calibrated sensor lots were used in the study. Sensor glucose measurements were compared with capillary blood glucose (BG) results (approximately eight per day) obtained using the BG meter built into the reader (BG reference) and with the YSI analyzer (Yellow Springs Instrument, Yellow Springs, OH) reference tests at three clinic visits (32 samples per visit). Sensor readings were masked to the participants. The accuracy of the results was demonstrated against capillary BG reference values, with 86.7% of sensor results within Consensus Error Grid Zone A. The percentage of readings within Consensus Error Grid Zone A on Days 2, 7, and 14 was 88.4%, 89.2%, and 85.2%, respectively. The overall mean absolute relative difference was 11.4%. The mean lag time between sensor and YSI reference values was 4.5±4.8 min. Sensor accuracy was not affected by factors such as body mass index, age, type of diabetes, clinical site, insulin administration, or hemoglobin A1c. Interstitial glucose measurements with the FreeStyle Libre system were found to be accurate compared with capillary BG reference values, with accuracy remaining stable over 14 days of wear and unaffected by patient characteristics.

Immobilization of glucose oxidase on graphene and cobalt phthalocyanine composite and its application for the determination of glucose.

Science.gov (United States)

Mani, Veerappan; Devasenathipathy, Rajkumar; Chen, Shen-Ming; Huang, Sheng-Tung; Vasantha, V S

2014-11-01

We described a simple and facile chemical reduction strategy for the preparation of graphene (GR)-cobalt phthalocyanine (CoPc) composite and explored it for the enzymatic determination of glucose. CoPc is an active mediator and electrocatalysts for the immobilization of GOx and determination of glucose. However, it is not stable on the electrode surface and also suffers from lack of conductivity. Here, we have employed GR as the suitable support to stabilize CoPc through simple chemical reduction method and the resulting composite has been used for the glucose biosensor application. Scanning electron microscopy, X-ray diffraction and Energy-dispersive X-ray spectroscopy studies confirmed the successful formation of composite. Direct electron transfer of glucose oxidase (GOx) was observed with well defined redox peaks at the formal potential of -0.44 V. The amount of electroactive GOx (Г) and electron transfer rate constant (ks) were calculated to be 3.77×10(-10) mol cm(-2) and 3.57 s(-1), respectively. The fabricated amperometric biosensor detects glucose in wide linear concentration range from 10 μM to 14.8 mM with high sensitivity of 5.0 9μA mM(-1) cm(-2). The sensor offered very low detection limit (LOD) of 1.6 μM. In addition, practical feasibility of the sensor has been explored in screen printing carbon electrode with accurate determination of glucose present in human blood serum and urine samples. Furthermore, the sensor exhibited appreciable stability, repeatability and reproducibility results. Copyright © 2014 Elsevier Inc. All rights reserved.

Integrated fiber optical and thermal sensor for noninvasive monitoring of blood and human tissue

Science.gov (United States)

Saetchnikov, Vladimir A.; Tcherniavskaia, Elina A.; Schiffner, Gerhard

2007-05-01

A novel concept of noninvasive monitoring of human tissue and blood based on optical diffuse reflective spectroscopy combined with metabolic heat measurements has been under development. A compact integrated fiber optical and thermal sensor has been developed. The idea of the method was to evaluate by optical spectroscopy haemoglobin and derivative concentrations and supplement with data associated with the oxidative metabolism of glucose. Body heat generated by glucose oxidation is based on the balance of capillary glucose and oxygen supply to the cells. The variation in glucose concentration is followed also by a difference from a distance (or depth) of scattered through the body radiation. So, blood glucose can be estimated by measuring the body heat and the oxygen supply. The sensor pickup contains of halogen lamp and LEDs combined with fiber optical bundle to deliver optical radiation inside and through the patient body, optical and thermal detectors. Fiber optical probe allows diffuse scattering measurement down to a depth of 2.5 mm in the skin including vascular system, which contributes to the control of the body temperature. The sensor pickup measures thermal generation, heat balance, blood flow rate, haemoglobin and derivative concentrations, environmental conditions. Multivariate statistical analysis was applied to convert various signals from the sensor pickup into physicochemical variables. By comparing the values from the noninvasive measurement with the venous plasma result, analytical functions for patient were obtained. Cluster analysis of patient groups was used to simplify a calibration procedure. Clinical testing of developed sensor is being performed.

Chitosan coated on the layers' glucose oxidase immobilized on cysteamine/Au electrode for use as glucose biosensor.

Science.gov (United States)

Zhang, Yawen; Li, Yunqiu; Wu, Wenjian; Jiang, Yuren; Hu, Biru

2014-10-15

A glucose biosensor was developed via direct immobilization of glucose oxidase (GOD) by self-assembled cysteamine monolayer on Au electrode surface followed by coating chitosan on the surface of electrode. In this work, chitosan film was coated on the surface of GOD as a protection film to ensure the stability and biocompatibility of the constructed glucose biosensor. The different application ranges of sensors were fabricated by immobilizing varied layers of GOD. The modified surface film was characterized by a scanning electron microscope (SEM) and the fabrication process of the biosensor was confirmed through electrochemical impedance spectroscopy (EIS) of ferrocyanide. The performance of cyclic voltammetry (CV) in the absence and presence of 25 mM glucose and ferrocenemethanol showed a diffusion-controlled electrode process and reflected the different maximum currents between the different GOD layers. With the developed glucose biosensor, the detection limits of the two linear responses are 49.96 μM and 316.8 μM with the sensitivities of 8.91 μA mM(-1)cm(-2) and 2.93 μA mM(-1)cm(-2), respectively. In addition, good stability (up to 30 days) of the developed biosensor was observed. The advantages of this new method for sensors construction was convenient and different width ranges of detection can be obtained by modified varied layers of GOD. The sensor with two layers of enzyme displayed two current linear responses of glucose. The present work provided a simplicity and novelty method for producing biosensors, which may help design enzyme reactors and biosensors in the future. Copyright © 2014 Elsevier B.V. All rights reserved.

Insulin resistance and β-cell function influence postprandial blood glucose levels in Japanese patients with gestational diabetes mellitus.

Science.gov (United States)

Kusunoki, Yoshiki; Katsuno, Tomoyuki; Nakae, Rie; Watanabe, Kahori; Ochi, Fumihiro; Tokuda, Masaru; Akagami, Takafumi; Miuchi, Masayuki; Miyagawa, Jun-ichiro; Namba, Mitsuyoshi

2015-01-01

The aim of this study in patients with gestational diabetes mellitus (GDM) was to evaluate the relationship of insulin resistance and secretion to area-under-the-sensor glucose concentration-time curve from before to 120 min postmeal (CGM-AUC(0-120 min)) as determined with continuous glucose monitoring (CGM). Immunoreactive insulin and HbA1c were determined in 22 Japanese patients with GDM undergoing a 75 g oral glucose tolerance test. Patients underwent CGM within 3 weeks of receiving a diagnosis of GDM. HbA1c (NGSP) was 5.5 ± 0.4%, BMI was 24.8 ± 5.3 kg/m(2), mean sensor glucose by CGM was 94.2 ± 10.3 mg/dL, standard deviation was 17.5 ± 4.4 mg/dL, and CGM-AUC(0-120 min) was 204.2 ± 23.8 h mg/dL. The insulin resistance indices the homeostasis model assessment ratio (HOMA-R), quantitative insulin sensitivity check index (QUICKI), and the Matsuda Index were correlated with CGM-AUC(0-120 min). The disposition index (DI), which was used to evaluate insulin secretion, was negatively correlated with CGM-AUC(0-120 min). Not only insulin resistance but also beta cell dysfunction contributes to postprandial hyperglycemia in Japanese patients with GDM.

Brain-derived neurotrophic factor in the nucleus tractus solitarii modulates glucose homeostasis after carotid chemoreceptor stimulation in rats.

Science.gov (United States)

Montero, Sergio; Cuéllar, Ricardo; Lemus, Mónica; Avalos, Reyes; Ramírez, Gladys; de Álvarez-Buylla, Elena Roces

2012-01-01

Neuronal systems, which regulate energy intake, energy expenditure and endogenous glucose production, sense and respond to input from hormonal related signals that convey information from body energy availability. Carotid chemoreceptors (CChr) function as sensors for circulating glucose levels and contribute to glycemic counterregulatory responses. Brain-derived neurotrophic factor (BDNF) that plays an important role in the endocrine system to regulate glucose metabolism could play a role in hyperglycemic glucose reflex with brain glucose retention (BGR) evoked by anoxic CChr stimulation. Infusing BDNF into the nucleus tractus solitarii (NTS) before CChr stimulation, showed that this neurotrophin increased arterial glucose and BGR. In contrast, BDNF receptor (TrkB) antagonist (K252a) infusions in NTS resulted in a decrease in both glucose variables.

Glucose Binding Protein as a Novel Optical Glucose Nanobiosensor

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Majed DWEIK

2009-11-01

Full Text Available Development of an in vivo optical sensor requires the utilization of Near Infra Red (NIR fluorophores due to their ability to operate within the biological tissue window. Alexa Fluor 750 (AF750 and Alexa Fluor 680 (AF680 were examined as potential NIR fluorophores for an in vivo fluorescence resonance energy transfer (FRET glucose biosensor. AF680 and AF750 found to be a FRET pair and percent energy transfer was calculated. Next, the tested dye pair was utilized in a competitive binding assay in order to detect glucose. Concanavalin A (Con A and dextran have binding affinity, but in the presence of glucose, glucose displaces dextran due to its higher affinity to Con A than dextran. Finally, the percent signal transfer through porcine skin was examined. The results showed with approximately 4.0 mm porcine skin thickness, 1.98 % of the fluorescence was transmitted and captured by the detector.

3D-copper oxide and copper oxide/few-layer graphene with screen printed nanosheet assembly for ultrasensitive non-enzymatic glucose sensing

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhimei [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin, 300384 (China); Advanced Materials and Printed Electronics Center, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin, 300384 (China); Pan, Peng, E-mail: panpeny@163.com [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin, 300384 (China); Advanced Materials and Printed Electronics Center, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin, 300384 (China); Liu, Xuewen [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin, 300384 (China); Advanced Materials and Printed Electronics Center, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin, 300384 (China); Yang, Zhengchun; Wei, Jun [Advanced Materials and Printed Electronics Center, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin, 300384 (China); Wei, Zhen, E-mail: weizhenxinxi@163.com [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin, 300384 (China); Advanced Materials and Printed Electronics Center, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin, 300384 (China)

2017-02-01

Screen-printed copper oxide (CuO) and CuO/few-layer graphene on graphite electrodes were used to fabricate the ultrasensitive nonenzymatic glucose biosensors. Flower-like CuO and flower-like CuO/few-layer graphene composites were prepared by screen-printing method and characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HETEM). On the basis of their cyclic voltammetry (CV) and chronoamperometry results, it was concluded that the addition of graphene to CuO significantly improved the performance of the fabricated glucose sensors, exhibiting high and reproducible sensitivity of 3120 μAmM{sup −1} cm{sup −2} with three linear ranges from 4 μM to 13.5 mM and the detection limit of 4 μM (S/N = 3) in a fast response time of 2 s. In addition, the fabricated sensors could effectively avoid the disturbance by interferents, such as Ascorbic Acid (AA), Uric Acid (UA), and Dopamine (DA). Most importantly, the testing results of real blood serum samples demonstrated that the electrodes were applicable and acceptable for the determination of glucose concentrations in human serum. The efficiencies of two non-enzymatic glucose biosensors for glucose determination were comparable with that of a commercial enzymatic sensor. - Highlights: • The method 2D nanosheet turns to 3D microflower by using screen printing was proposed. • Few-layer graphene added improved the sensor’s performance on base of CuO functional material. • Two ultrasensitive non-enzymatic glucose sensors were successfully fabricated. • The proposed sensor shows a high sensitivity of 3120 μA mM{sup −1} cm{sup −2}.

Pyruvate incubation enhances glycogen stores and sustains neuronal function during subsequent glucose deprivation.

Science.gov (United States)

Shetty, Pavan K; Sadgrove, Matthew P; Galeffi, Francesca; Turner, Dennis A

2012-01-01

The use of energy substrates, such as lactate and pyruvate, has been shown to improve synaptic function when administered during glucose deprivation. In the present study, we investigated whether prolonged incubation with monocarboxylate (pyruvate or lactate) prior rather than during glucose deprivation can also sustain synaptic and metabolic function. Pyruvate pre-incubation(3-4h) significantly prolonged (>25 min) the tolerance of rat hippocampal slices to delayed glucose deprivation compared to control and lactate pre-incubated slices, as revealed by field excitatory post synaptic potentials (fEPSPs); pre-incubation with pyruvate also reduced the marked decrease in NAD(P)H fluorescence resulting from glucose deprivation. Moreover, pyruvate exposure led to the enhancement of glycogen stores with time, compared to glucose alone (12 μmol/g tissue at 4h vs. 3.5 μmol/g tissue). Prolonged resistance to glucose deprivation following exogenous pyruvate incubation was prevented by glycogenolysis inhibitors, suggesting that enhanced glycogen mediates the delay in synaptic activity failure. The application of an adenosine A1 receptor antagonist enhanced glycogen utilization and prolonged the time to synaptic failure, further confirming this hypothesis of the importance of glycogen. Moreover, tissue levels of ATP were also significantly maintained during glucose deprivation in pyruvate pretreated slices compared to control and lactate. In summary, these experiments indicate that pyruvate exposure prior to glucose deprivation significantly increased the energy buffering capacity of hippocampal slices, particularly by enhancing internal glycogen stores, delaying synaptic failure during glucose deprivation by maintaining ATP levels, and minimizing the decrease in the levels of NAD(P)H. Copyright © 2011 Elsevier Inc. All rights reserved.

Metal nanostructures for non-enzymatic glucose sensing

International Nuclear Information System (INIS)

Tee, Si Yin; Teng, Choon Peng; Ye, Enyi

2017-01-01

This review covers the recent development of metal nanostructures in electrochemical non-enzymatic glucose sensing. It highlights a variety of nanostructured materials including noble metals, other transition metals, bimetallic systems, and their hybrid with carbon-based nanomaterials. Particularly, attention is devoted to numerous approaches that have been implemented for improving the sensors performance by tailoring size, shape, composition, effective surface area, adsorption capability and electron-transfer properties. The correlation of the metal nanostructures to the glucose sensing performance is addressed with respect to the linear concentration range, sensitivity and detection limit. In overall, this review provides important clues from the recent scientific achievements of glucose sensor nanomaterials which will be essentially useful in designing better and more effective electrocatalysts for future electrochemical sensing industry. - Highlights: • Overview of recent development of metal nanostructures in electrochemical non-enzymatic glucose sensing. • Special attention is focussed on noble metals, other transition metals, bimetallic systems, and their hybrid with carbon-based nanomaterials. • Merits and limitations of various metal nanostructures in electrochemical non-enzymatic glucose sensing. • Strategies to improve the glucose sensing performance of metal nanostructures as electrocatalysts.

Sensitive Determination of 6-Thioguanine Using Caffeic Acid-functionalized Fe3O4 Nanoparticles as an Electrochemical Sensor

Science.gov (United States)

Amir, Md.; Tunesi, Mawada M.; Soomro, Razium A.; Baykal, Abdülhadi; Kalwar, Nazar H.

2018-04-01

The study demonstrates the potential application of caffeic acid-functionalized magnetite nanoparticles (CA-Fe3O4 NPs) as an effective electrode modifying material for the electrochemical oxidation of the 6-thioguanine (6-TG) drug. The functionalized Fe3O4 NPs were prepared using simple wet-chemical methodology where the used caffeic acid acted simultaneously as growth controlling and functionalizing agent. The study discusses the influence of an effective functionalization on the signal sensitivity observed for the electro-oxidation of 6-TG over CA-Fe3O4 NPs in comparison to a glassy carbon electrode modified with bare and nicotinic acid (NA)-functionalized Fe3O4 NPs. The experiment results provided sufficient evidence to support the importance of favorable functionality to achieve higher signal sensitivity for the electro-oxidation of 6-TG. The presence of favorable interactions between the active functional moieties of caffeic acid and 6-TG synergized with the greater surface area of magnetic NPs produces a stable electro-oxidation signal within the working range of 0.01-0.23 μM with sensitive up to 0.001 μM. Additionally, the sensor showed the strong anti-interference potential against the common co-existing drug molecules such as benzoic acid, acetaminophen, epinephrine, norepinephrine, glucose, ascorbic acid and l-cysteine. In addition, the successful quantification of 6-TG from the commercial tablets obtained from local pharmacy further signified the practical capability of the discussed sensor.

Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor

Directory of Open Access Journals (Sweden)

Baoyan Wu

2015-09-01

Full Text Available A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs and glucose oxidase (GOD onto single-walled carbon nanotubes (SWCNTs-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for optimizing the biosensor. Among the resulting glucose biosensors, the four layers of AuNRs-GOD-modified electrode showed the best performance. The sol-SWCNTs-(AuNRs- GOD4/Au biosensor exhibited a good linear range of 0.01–8 mM glucose, high sensitivity of 1.08 μA/mM, and fast amperometric response within 4 s. The good performance of the proposed glucose biosensor could be mainly attributed to the advantages of the three-dimensional sol-gel matrix and stereo self-assembly films, and the natural features of one-dimensional nanostructure SWCNTs and AuNRs. This study may provide a new facile way to fabricate the enzyme-based biosensor with high performance.

Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor.

Science.gov (United States)

Wu, Baoyan; Hou, Shihua; Miao, Zhiying; Zhang, Cong; Ji, Yanhong

2015-09-18

A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs) and glucose oxidase (GOD) onto single-walled carbon nanotubes (SWCNTs)-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for optimizing the biosensor. Among the resulting glucose biosensors, the four layers of AuNRs-GOD-modified electrode showed the best performance. The sol-SWCNTs-(AuNRs- GOD)₄/Au biosensor exhibited a good linear range of 0.01-8 mM glucose, high sensitivity of 1.08 μA/mM, and fast amperometric response within 4 s. The good performance of the proposed glucose biosensor could be mainly attributed to the advantages of the three-dimensional sol-gel matrix and stereo self-assembly films, and the natural features of one-dimensional nanostructure SWCNTs and AuNRs. This study may provide a new facile way to fabricate the enzyme-based biosensor with high performance.

Triboelectric Hydrogen Gas Sensor with Pd Functionalized Surface

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Sung-Ho Shin

2016-10-01

Full Text Available Palladium (Pd-based hydrogen (H2 gas sensors have been widely investigated thanks to its fast reaction and high sensitivity to hydrogen. Various sensing mechanisms have been adopted for H2 gas sensors; however, all the sensors must be powered through an external battery. We report here an H2 gas sensor that can detect H2 by measuring the output voltages generated during contact electrification between two friction surfaces. When the H2 sensor, composed of Pd-coated ITO (indium tin oxide and PET (polyethylene Terephthalate film, is exposed to H2, its output voltage is varied in proportion to H2 concentration because the work function (WF of Pd-coated surface changes, altering triboelectric charging behavior. Specifically, the output voltage of the sensor is gradually increased as exposing H2 concentration increases. Reproducible and sensitive sensor response was observed up 1% H2 exposure. The approach introduced here can easily be adopted to development of triboelectric gas sensors detecting other gas species.

Glucose Transporters at the Blood-Brain Barrier: Function, Regulation and Gateways for Drug Delivery.

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Patching, Simon G

2017-03-01

Glucose transporters (GLUTs) at the blood-brain barrier maintain the continuous high glucose and energy demands of the brain. They also act as therapeutic targets and provide routes of entry for drug delivery to the brain and central nervous system for treatment of neurological and neurovascular conditions and brain tumours. This article first describes the distribution, function and regulation of glucose transporters at the blood-brain barrier, the major ones being the sodium-independent facilitative transporters GLUT1 and GLUT3. Other GLUTs and sodium-dependent transporters (SGLTs) have also been identified at lower levels and under various physiological conditions. It then considers the effects on glucose transporter expression and distribution of hypoglycemia and hyperglycemia associated with diabetes and oxygen/glucose deprivation associated with cerebral ischemia. A reduction in glucose transporters at the blood-brain barrier that occurs before the onset of the main pathophysiological changes and symptoms of Alzheimer's disease is a potential causative effect in the vascular hypothesis of the disease. Mutations in glucose transporters, notably those identified in GLUT1 deficiency syndrome, and some recreational drug compounds also alter the expression and/or activity of glucose transporters at the blood-brain barrier. Approaches for drug delivery across the blood-brain barrier include the pro-drug strategy whereby drug molecules are conjugated to glucose transporter substrates or encapsulated in nano-enabled delivery systems (e.g. liposomes, micelles, nanoparticles) that are functionalised to target glucose transporters. Finally, the continuous development of blood-brain barrier in vitro models is important for studying glucose transporter function, effects of disease conditions and interactions with drugs and xenobiotics.

First Clinical Experience with Retrospective Flash Glucose Monitoring (FGM) Analysis in South Africa: Characterizing Glycemic Control with Ambulatory Glucose Profile.

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Distiller, Larry A; Cranston, Iain; Mazze, Roger

2016-11-01

In 2014, an innovative blinded continuous glucose monitoring system was introduced with automated ambulatory glucose profile (AGP) reporting. The clinical use and interpretation of this new technology has not previously been described. Therefore we wanted to understand its use in characterizing key factors related to glycemic control: glucose exposure, variability, and stability, and risk of hypoglycemia in clinical practice. Clinicians representing affiliated diabetes centers throughout South Africa were trained and subsequently were given flash glucose monitoring readers and 2-week glucose sensors to use at their discretion. After patient use, sensor data were collected and uploaded for AGP reporting. Complete data (sensor AGP with corresponding clinical information) were obtained for 50 patients with type 1 (70%) and type 2 diabetes (30%), irrespective of therapy. Aggregated analysis of AGP data comparing patients with type 1 versus type 2 diabetes, revealed that despite similar HbA1c values between both groups (8.4 ± 2 vs 8.6 ± 1.7%, respectively), those with type 2 diabetes had lower mean glucose levels (9.2 ± 3 vs 10.3 mmol/l [166 ± 54 vs 185 mg/dl]) and lower indices of glucose variability (3.0 ± 1.5 vs 5.0 ± 1.9 mmol/l [54 ± 27 vs 90 ± 34.2 mg/dl]). This highlights key areas for future focus. Using AGP, the characteristics of glucose exposure, variability, stability, and hypoglycemia risk and occurrence were obtained within a short time and with minimal provider and patient input. In a survey at the time of the follow-up visit, clinicians indicated that aggregated AGP data analysis provided important new clinical information and insights. © 2016 Diabetes Technology Society.

Amperometric Bioelectronic Tongue for glucose determination

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Yazan Al-Issa

2015-03-01

Full Text Available An amperometric Bioelectronic Tongue is reported for glucose determination that contains eight sensor electrodes constructed using different metal electrodes (Pt, Au, oxidoreductase enzymes (glucose oxidase, ascorbate oxidase, uricase, and membrane coatings (Nafion, chitosan. The response to varying concentrations of glucose, ascorbic acid, uric acid, and acetaminophen was tested for two models, concentration determination by current density measurements at individual electrodes and concentration determination by a linear regression model for the entire electrode array. The reduced chi-squared for the full array model was found to be about one order of magnitude lower than that for the individual-electrode model. Discrimination of glucose from chemical interference by the other three species is accomplished through a combination of enzyme catalysis, metal electrocatalysis, and membrane surface charge. The benefit of incorporating enzyme electrodes into the sensor array is illustrated by the lower correlation coefficients between different enzyme electrodes relative to non-enzyme coated electrodes. This approach can be more generally applied to detection of other substrates of oxidoreductase enzymes.

Pulse-voltammetric glucose detection at gold junction electrodes.

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Rassaei, Liza; Marken, Frank

2010-09-01

A novel glucose sensing concept based on the localized change or "modulation" in pH within a symmetric gold-gold junction electrode is proposed. A paired gold-gold junction electrode (average gap size ca. 500 nm) is prepared by simultaneous bipotentiostatic electrodeposition of gold onto two closely spaced platinum disk electrodes. For glucose detection in neutral aqueous solution, the potential of the "pH-modulator" electrode is set to -1.5 V vs saturated calomel reference electrode (SCE) to locally increase the pH, and simultaneously, either cyclic voltammetry or square wave voltammetry experiments are conducted at the sensor electrode. A considerable improvement in the sensor electrode response is observed when a normal pulse voltammetry sequence is applied to the modulator electrode (to generate "hydroxide pulses") and the glucose sensor electrode is operated with fixed bias at +0.5 V vs SCE (to eliminate capacitive charging currents). Preliminary data suggest good linearity for the glucose response in the medically relevant 1-10 mM concentration range (corresponding to 0.18-1.8 g L(-1)). Future electroanalytical applications of multidimensional pulse voltammetry in junction electrodes are discussed.

Design, synthesis and structure of new potential electrochemically active boronic acid-based glucose sensors

DEFF Research Database (Denmark)

Norrild, Jens Chr.; Søtofte, Inger

2002-01-01

In the course of our investigations on new boronic acid based carbohydrate sensors three new boronic acids 3, 7 and 11 containing a ferrocene moiety were synthesised. Their design includes an intramolecular B-N bonding motif in order to facilitate binding at physiological pH. We report the synthe......In the course of our investigations on new boronic acid based carbohydrate sensors three new boronic acids 3, 7 and 11 containing a ferrocene moiety were synthesised. Their design includes an intramolecular B-N bonding motif in order to facilitate binding at physiological pH. We report...... the synthesis of the compounds and our investigations on glucose complexation as studied by C-13 NMR spectroscopy. The crystal structure of 2,4,6-tris[2-(N-ferrocenylmethyl-N-methylaminomethyl) phenyl] boroxin (13) (boroxin of boronic acid 3) (boroxin = cyclotriboroxane) was obtained and compared...... with structures obtained of 2,4,6-tris[2-(N,N-dimethylaminomethyl)phenyl]boroxin (14) and 2,2-dimethyl-1,3-diyl[2-(N,N-dimethylaminomethyl)phenyl]boronate (15). The structure of 13 shows the existence of intramolecular B-N bonds in the solid phase....

The continuous glucose monitoring sensor in neonatal intensive care

OpenAIRE

Beardsall, K; Ogilvy-Stuart, A; Ahluwalia, J; Thompson, M; Dunger, D

2005-01-01

Objective: To determine the feasibility of continuous glucose monitoring in the very low birthweight baby requiring intensive care, as these infants are known to be at high risk of abnormalities of glucose control.

Multiple functional attributes of glucose-monitoring neurons in the medial orbitofrontal (ventrolateral prefrontal) cortex.

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Szabó, István; Hormay, Edina; Csetényi, Bettina; Nagy, Bernadett; Lénárd, László; Karádi, Zoltán

2018-02-01

Multiple functional attributes of glucose-monitoring neurons in the medial orbitofrontal (ventrolateral prefrontal) cortex. NEUROSCI BIOBEHAV REV 73(1) XXX-XXX, 2017.- Special chemosensory cells, the glucose-monitoring (GM) neurons, reportedly involved in the central feeding control, exist in the medial orbitofrontal (ventrolateral prefrontal) cortex (mVLPFC). Electrophysiological, metabolic and behavioral studies reveal complex functional attributes of these cells and raise their homeostatic significance. Single neuron recordings, by means of the multibarreled microelectrophoretic technique, elucidate differential sensitivities of limbic forebrain neurons in the rat and the rhesus monkey to glucose and other chemicals, whereas gustatory stimulations demonstrate their distinct taste responsiveness. Metabolic examinations provide evidence for alteration of blood glucose level in glucose tolerance test and elevation of plasma triglyceride concentration after destruction of the local GM cells by streptozotocin (STZ). In behavioral studies, STZ microinjection into the mVLPFC fails to interfere with the acquisition of saccharin conditioned taste avoidance, does cause, however, taste perception deficit in taste reactivity tests. Multiple functional attributes of GM neurons in the mVLPFC, within the frame of the hierarchically organized central GM neuronal network, appear to play important role in the maintenance of the homeostatic balance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sensitive Fluorescent Sensor for Recognition of HIV-1 dsDNA by Using Glucose Oxidase and Triplex DNA

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Yubin Li

2018-01-01

Full Text Available A sensitive fluorescent sensor for sequence-specific recognition of double-stranded DNA (dsDNA was developed on the surface of silver-coated glass slide (SCGS. Oligonucleotide-1 (Oligo-1 was designed to assemble on the surface of SCGS and act as capture DNA, and oligonucleotide-2 (Oligo-2 was designed as signal DNA. Upon addition of target HIV-1 dsDNA (Oligo-3•Oligo-4, signal DNA could bind on the surface of silver-coated glass because of the formation of C•GoC in parallel triplex DNA structure. Biotin-labeled glucose oxidase (biotin-GOx could bind to signal DNA through the specific interaction of biotin-streptavidin, thereby GOx was attached to the surface of SCGS, which was dependent on the concentration of target HIV-1 dsDNA. GOx could catalyze the oxidation of glucose and yield H2O2, and the HPPA can be oxidized into a fluorescent product in the presence of HRP. Therefore, the concentration of target HIV-1 dsDNA could be estimated with fluorescence intensity. Under the optimum conditions, the fluorescence intensity was proportional to the concentration of target HIV-1 dsDNA over the range of 10 pM to 1000 pM, the detection limit was 3 pM. Moreover, the sensor had good sequence selectivity and practicability and might be applied for the diagnosis of HIV disease in the future.

Noninvasive wearable sensor for indirect glucometry.

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Zilberstein, Gleb; Zilberstein, Roman; Maor, Uriel; Righetti, Pier Giorgio

2018-04-02

A noninvasive mini-sensor for blood glucose concentration assessment has been developed. The monitoring is performed by gently pressing a wrist or fingertip onto the chemochromic mixture coating a thin glass or polymer film positioned on the back panel of a smart watch with PPG/HRM (photoplethysmographic/heart rate monitoring sensor). The various chemochromic components measure the absolute values of the following metabolites present in the sweat: acetone, acetone beta-hydroxybutirate, aceto acetate, water, carbon dioxide, lactate anion, pyruvic acid, Na and K salts. Taken together, all these parameters give information about blood glucose concentration, calculated via multivariate analysis based on neural network algorithms built into the sensor. The Clarke Error Grid shows an excellent correlation between data measured by the standard invasive glucose analyser and the present noninvasive sensor, with all points aligned along a 45-degree diagonal and contained almost exclusively in sector A. Graphs measuring glucose levels five times a day (prior, during and after breakfast and prior, during and after lunch), for different individuals (males and females) show a good correlation between the two curves of conventional, invasive meters vs. the noninvasive sensor, with an error of ±15%. This novel, noninvasive sensor for indirect glucometry is fully miniaturized, easy to use and operate and could represent a valid alternative in clinical settings and for individual, personal users, to current, invasive tools. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Glucose transport in brain - effect of inflammation.

Science.gov (United States)

Jurcovicova, J

2014-01-01

Glucose is transported across the cell membrane by specific saturable transport system, which includes two types of glucose transporters: 1) sodium dependent glucose transporters (SGLTs) which transport glucose against its concentration gradient and 2) sodium independent glucose transporters (GLUTs), which transport glucose by facilitative diffusion in its concentration gradient. In the brain, both types of transporters are present with different function, affinity, capacity, and tissue distribution. GLUT1 occurs in brain in two isoforms. The more glycosylated GLUT1 is produced in brain microvasculature and ensures glucose transport across the blood brain barrier (BBB). The less glycosylated form is localized in astrocytic end-feet and cell bodies and is not present in axons, neuronal synapses or microglia. Glucose transported to astrocytes by GLUT1 is metabolized to lactate serving to neurons as energy source. Proinflammatory cytokine interleukin (IL)-1β upregulates GLUT1 in endothelial cells and astrocytes, whereas it induces neuronal death in neuronal cell culture. GLUT2 is present in hypothalamic neurons and serves as a glucose sensor in regulation of food intake. In neurons of the hippocampus, GLUT2 is supposed to regulate synaptic activity and neurotransmitter release. GLUT3 is the most abundant glucose transporter in the brain having five times higher transport capacity than GLUT1. It is present in neuropil, mostly in axons and dendrites. Its density and distribution correlate well with the local cerebral glucose demands. GLUT5 is predominantly fructose transporter. In brain, GLUT5 is the only hexose transporter in microglia, whose regulation is not yet clear. It is not present in neurons. GLUT4 and GLUT8 are insulin-regulated glucose transporters in neuronal cell bodies in the cortex and cerebellum, but mainly in the hippocampus and amygdala, where they maintain hippocampus-dependent cognitive functions. Insulin translocates GLUT4 from cytosol to plasma

Nanomaterials in glucose sensing

CERN Document Server

Burugapalli, Krishna

2013-01-01

The smartness of nano-materials is attributed to their nanoscale and subsequently unique physicochemical properties and their use in glucose sensing has been aimed at improving performance, reducing cost and miniaturizing the sensor and its associated instrumentation. So far, portable (handheld) glucose analysers were introduced for hospital wards, emergency rooms and physicians' offices; single-use strip systems achieved nanolitre sampling for painless and accurate home glucose monitoring; advanced continuous monitoring devices having 2 to 7 days operating life are in clinical and home use; and continued research efforts are being made to develop and introduce increasingly advanced glucose monitoring systems for health as well as food, biotechnology, cell and tissue culture industries. Nanomaterials have touched every aspect of biosensor design and this chapter reviews their role in the development of advanced technologies for glucose sensing, and especially for diabetes. Research shows that overall, nanomat...

Direct electrochemical sensing of glucose using glucose oxidase immobilized on functionalized carbon nanotubes via a novel metal chelate-based affinity method

International Nuclear Information System (INIS)

Tu, X.; Zhao, Y.; Luo, S.; Luo, X.; Feng, L.

2012-01-01

We report on a novel amperometric glassy carbon biosensing electrode for glucose. It is based on the immobilization of a highly sensitive glucose oxidase (GOx) by affinity interaction on carbon nanotubes (CNTs) functionalized with iminodiacetic acid and metal chelates. The new technique for immobilization is exploiting the affinity of Co(II) ions to the histidine and cysteine moieties on the surface of GOx. The direct electrochemistry of immobilized GOx revealed that the functionalized CNTs greatly improve the direct electron transfer between GOx and the surface of the electrode to give a pair of well-defined and almost reversible redox peaks and undergoes fast heterogeneous electron transfer with a rate constant (k s) of 0. 59 s -1 . The GOx immobilized in this way fully retained its activity for the oxidation of glucose. The resulting biosensor is capable of detecting glucose at levels as low as 0.01 mM, and has excellent operational stability (with no decrease in the activity of enzyme over a 10 days period). The method of immobilizing GOx is easy and also provides a model technique for potential use with other redox enzymes and proteins. (author)

Brain glucose sensing, glucokinase and neural control of metabolism and islet function.

Science.gov (United States)

Ogunnowo-Bada, E O; Heeley, N; Brochard, L; Evans, M L

2014-09-01

It is increasingly apparent that the brain plays a central role in metabolic homeostasis, including the maintenance of blood glucose. This is achieved by various efferent pathways from the brain to periphery, which help control hepatic glucose flux and perhaps insulin-stimulated insulin secretion. Also, critically important for the brain given its dependence on a constant supply of glucose as a fuel--emergency counter-regulatory responses are triggered by the brain if blood glucose starts to fall. To exert these control functions, the brain needs to detect rapidly and accurately changes in blood glucose. In this review, we summarize some of the mechanisms postulated to play a role in this and examine the potential role of the low-affinity hexokinase, glucokinase, in the brain as a key part of some of this sensing. We also discuss how these processes may become altered in diabetes and related metabolic diseases. © 2014 John Wiley & Sons Ltd.

Photochemical immobilization of protein on the inner wall of a microchannel and Its application in a glucose sensor

International Nuclear Information System (INIS)

Nakajima, Hizuru; Ishino, Satomi; Masuda, Hironori; Nakagama, Tatsuro; Shimosaka, Takuya; Uchiyama, Katsumi

2006-01-01

A new protein immobilization technique has been developed for patterning enzymes in a specific position inside a microchannel. First, bovine serum albumin (BSA) was adsorbed onto the internal surface of a polydimethylsiloxane microchannel. The microchannel was then filled with the conjugate solution of a photoreactive cross-linker, 4-azido-2,3,5,6-tetrafluorobenzoic acid succinimidyl ester (ATFB-SE), and an enzyme, horseradish peroxidase (HRP). An irradiation by a He-Cd laser activated the azido group of the conjugates and these conjugates became covalently attached to the adsorbed BSA on the microchannel. The enzyme turnover was observed from only the HRP zone. This technique was successfully applied to the enzymatic glucose sensor. Glucose oxidase (GOD) and HRP were sequentially patterned in a single microchannel, i.e., the HRP zone was located downstream from the GOD zone. The calibration curve of a glucose standard solution was linear over the range of 0-128 μM with a correlation coefficient of 0.993. Compared to the traditional method using a 96-well microtiter plate, the present technique on the microchip shortened the reaction time from 30 min to 4.8 s, i.e., to 1/375

Association Between Blood Glucose and Functional Outcome in Intracerebral Hemorrhage: A Systematic Review and Meta-Analysis.

Science.gov (United States)

Zheng, Jun; Yu, Zhiyuan; Ma, Lu; Guo, Rui; Lin, Sen; You, Chao; Li, Hao

2018-03-16

Intracerebral hemorrhage (ICH) is a devastating subtype of stroke. Patients with ICH have poor functional outcomes. The association between blood glucose level and functional outcome in ICH remains unclear. This systematic review and meta-analysis aimed to investigate the association between blood glucose level and functional outcomes in patients with ICH. Literature was searched systemically in PubMed, EMBASE, Web of Science, and Cochrane Library. Published cohort studies evaluating the association between blood glucose and functional outcome in patients with ICH were included. This meta-analysis was performed using odds ratios (ORs) and 95% confidence intervals (CIs). A total of 16 studies were included in our meta-analysis. Our data show that hyperglycemia defined by cutoff values was significantly associated with unfavorable functional outcome (OR, 1.80; 95% CI, 1.36-2.39; P analysis also suggested a significant association between increased blood glucose levels and functional outcomes (OR, 1.05; 95% CI, 1.03-1.07; P functional outcome in ICH. Further studies with larger sample sizes, more time points, and longer follow-up times are necessary to confirm this association. Copyright © 2018 Elsevier Inc. All rights reserved.

Thumb-size ultrasonic-assisted spectroscopic imager for in-situ glucose monitoring as optional sensor of conventional dialyzers

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Nogo, Kosuke; Mori, Keita; Qi, Wei; Hosono, Satsuki; Kawashima, Natsumi; Nishiyama, Akira; Wada, Kenji; Ishimaru, Ichiro

2016-03-01

We proposed the ultrasonic-assisted spectroscopic imaging for the realization of blood-glucose-level monitoring during dialytic therapy. Optical scattering and absorption caused by blood cells deteriorate the detection accuracy of glucose dissolved in plasma. Ultrasonic standing waves can agglomerate blood cells at nodes. In contrast, around anti-node regions, the amount of transmitted light increases because relatively clear plasma appears due to decline the number of blood cells. Proposed method can disperse the transmitted light of plasma without time-consuming pretreatment such as centrifugation. To realize the thumb-size glucose sensor which can be easily attached to dialysis tubes, an ultrasonic standing wave generator and a spectroscopic imager are required to be small. Ultrasonic oscillators are ∅30[mm]. A drive circuit of oscillators, which now size is 41×55×45[mm], is expected to become small. The trial apparatus of proposed one-shot Fourier spectroscopic imager, whose size is 30×30×48[mm], also can be little-finger size in principal. In the experiment, we separated the suspension mixed water and micro spheres (Θ10[mm) into particles and liquid regions with the ultrasonic standing wave (frequency: 2[MHz]). Furthermore, the spectrum of transmitted light through the suspension could be obtained in visible light regions with a white LED.

Non-invasive optical detection of glucose in cell culture nutrient medium

Science.gov (United States)

Cote, Gerald L.

1993-01-01

The objective of the proposed research was to begin the development of a non-invasive optical sensor for measuring glucose concentration in the output medium of cell cultures grown in a unique NASA bioreactor referred to as an integrated rotating-wall vessel (IRWV). The input, a bovine serum based nutrient media, has a known glucose concentration. The cells within the bioreactor digest a portion of the glucose. Thus, the non-invasive optical sensor is needed to monitor the decrease in glucose due to cellular consumption since the critical parameters for sustained cellular productivity are glucose and pH. Previous glucose sensing techniques have used chemical reactions to quantify the glucose concentration. Chemical reactions, however, cannot provide for continuous, real time, non-invasive measurement as is required in this application. Our effort while in the fellowship program was focused on the design, optical setup, and testing of one bench top prototype non-invasive optical sensor using a mid-infrared absorption spectroscopy technique. Glucose has a fundamental vibrational absorption peak in the mid-infrared wavelength range at 9.6 micron. Preliminary absorption data using a CO2 laser were collected at this wavelength for water based glucose solutions at different concentrations and one bovine serum based nutrient medium (GTSF) with added glucose. The results showed near linear absorption responses for the glucose-in-water data with resolutions as high at 108 mg/dl and as low as 10 mg/dl. The nutrient medium had a resolution of 291 mg/dl. The variability of the results was due mainly to thermal and polarization drifts of the laser while the decrease in sensitivity to glucose in the nutrient medium was expected due to the increase in the number of confounders present in the nutrient medium. A multispectral approach needs to be used to compensate for these confounders. The CO2 laser used for these studies was wavelength tunable (9.2 to 10.8 micrometers), however

Fiber Optic Chemical Sensors

Science.gov (United States)

1993-10-01

31, 1980. Koyama, Masao and Sato , Yuichi, "Improved Enzyme Sensor for Glucose with an Ultra-Filtration Membrane and Immobilized Glucose Oxidase...ion Process," American Laboratory, AVO, AIS, 54-59, 1989. Kaihara, Mikio ; Mametsuka, Hiroaki; Gunji, Naoki; Iwata, Hideo and Gohshi,, "New Dilution

INFLUENCE OF TIME BETWEEN RUMINAL GLUCOSE CHALLENGES ON RUMEN FUNCTION

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Martín F. Montaño-Gómez

2016-08-01

Full Text Available Ruminal lactic acidosis is one of the most important metabolic problems in feedlot cattle. Gradually transitioning cattle to finishing-feedlot diets may reduce the risk for ruminal acidosis by providing sufficient time for adaptation. This adaptation of feedlot cattle to high-concentrate diets may causes marked changes in the ruminal environment, and time is required to establish stable ruminal conditions.   However, few studies have evaluated the ruminal adaptation in steers. A metabolism trial was conducted to evaluate the effects of two consecutive glucose challenges on rumen function in steers fed a high-energy finishing diet. Four Holstein steers (320 kg LW with cannula in the rumen were used in a 4 x 4 Latin square design. Four treatments were used and consisted of the time elapsed between both challenges of glucose (2, 4, 6 or 8 d. Ruminal fluid samples were taken at 0700 h (just prior the first glucose challenge, and from the second challenge (d 2, 4, 6, or 8 at 1 h before and 2, 4, 6, 8, 28, 52, 124, 196 and 268 h. As the time between fluctuation of energy intake increased, ruminal fluid pH (P 0.10. During the first 6 h following the second glucose challenge ruminal fluid pH decreased. No effects of treatments on ruminal pH were observed (P >0.10 among treatments from 3 days after the second challenge. Ruminal fluid osmotic pressure increased (P <0.10 after dosed glucose with all treatments. Ruminal osmolality increased (P <0.10 as the time between challenges were 2 or 4 days. After dosed glucose, total volatile fatty acids increased, except by treatment 1 after second challenge. Total volatile fatty acid and pH were related positively (R2 =0.69. As the time increased, a tendency on increment of concentrations of protozoa was observed. Ruminal glucose concentration decreased linearly (P <0.10 2 h after the second fluctuation of energy intake. We conclude that ruminal alterations are magnified as the time between glucose challenge

Woven electrochemical fabric-based test sensors (WEFTS): a new class of multiplexed electrochemical sensors.

Science.gov (United States)

Choudhary, Tripurari; Rajamanickam, G P; Dendukuri, Dhananjaya

2015-05-07

We present textile weaving as a new technique for the manufacture of miniature electrochemical sensors with significant advantages over current fabrication techniques. Biocompatible silk yarn is used as the material for fabrication instead of plastics and ceramics used in commercial sensors. Silk yarns are coated with conducting inks and reagents before being handloom-woven as electrodes into patches of fabric to create arrays of sensors, which are then laminated, cut and packaged into individual sensors. Unlike the conventionally used screen-printing, which results in wastage of reagents, yarn coating uses only as much reagent and ink as required. Hydrophilic and hydrophobic yarns are used for patterning so that sample flow is restricted to a small area of the sensor. This simple fluidic control is achieved with readily available materials. We have fabricated and validated individual sensors for glucose and hemoglobin and a multiplexed sensor, which can detect both analytes. Chronoamperometry and differential pulse voltammetry (DPV) were used to detect glucose and hemoglobin, respectively. Industrial quantities of these sensors can be fabricated at distributed locations in the developing world using existing skills and manufacturing facilities. We believe such sensors could find applications in the emerging area of wearable sensors for chemical testing.

Functional Testing of Wireless Sensor Node Designs

DEFF Research Database (Denmark)

Virk, Kashif M.; Madsen, Jan

2007-01-01

Wireless sensor networks are networked embedded computer systems with stringent power, performance, cost and form-factor requirements along with numerous other constraints related to their pervasiveness and ubiquitousness. Therefore, only a systematic design methdology coupled with an efficient...... test approach can enable their conformance to design and deployment specifications. We discuss off-line, hierarchical, functional testing of complete wireless sensor nodes containing configurable logic through a combination of FPGA-based board test and Software-Based Self-Test (SBST) techniques...

Glucose Homeostasis, Pancreatic Endocrine Function, and Outcomes in Advanced Heart Failure.

Science.gov (United States)

Melenovsky, Vojtech; Benes, Jan; Franekova, Janka; Kovar, Jan; Borlaug, Barry A; Segetova, Marketa; Tura, Andrea; Pelikanova, Tereza

2017-08-07

The mechanisms and relevance of impaired glucose homeostasis in advanced heart failure (HF) are poorly understood. The study goals were to examine glucose regulation, pancreatic endocrine function, and metabolic factors related to prognosis in patients with nondiabetic advanced HF. In total, 140 advanced HF patients without known diabetes mellitus and 21 sex-, age-, and body mass index-matched controls underwent body composition assessment, oral glucose tolerance testing, and measurement of glucose-regulating hormones to model pancreatic β-cell secretory response. Compared with controls, HF patients had similar fasting glucose and insulin levels but higher levels after oral glucose tolerance testing. Insulin secretion was not impaired, but with increasing HF severity, there was a reduction in glucose, insulin, and insulin/glucagon ratio-a signature of starvation. The insulin/C-peptide ratio was decreased in HF, indicating enhanced insulin clearance, and this was correlated with lower cardiac output, hepatic insufficiency, right ventricular dysfunction, and body wasting. After a median of 449 days, 41% of patients experienced an adverse event (death, urgent transplant, or assist device). Increased glucagon and, paradoxically, low fasting plasma glucose displayed the strongest relations to outcome ( P =0.01). Patients in the lowest quartile of fasting plasma glucose (3.8-5.1 mmol·L -1 , 68-101 mg·dL -1 ) had 3-times higher event risk than in the top quartile (6.0-7.9 mmol·L -1 , 108-142 mg·dL -1 ; relative risk: 3.05 [95% confidence interval, 1.46-6.77]; P =0.002). Low fasting plasma glucose and increased glucagon are robust metabolic predictors of adverse events in advanced HF. Pancreatic insulin secretion is preserved in advanced HF, but levels decrease with increasing HF severity due to enhanced insulin clearance that is coupled with right heart failure and cardiac cachexia. © 2017 The Authors. Published on behalf of the American Heart Association, Inc

Electrochemical Glucose Sensors—Developments Using Electrostatic Assembly and Carbon Nanotubes for Biosensor Construction

Directory of Open Access Journals (Sweden)

Mark R. Anderson

2010-09-01

Full Text Available In 1962, Clark and Lyons proposed incorporating the enzyme glucose oxidase in the construction of an electrochemical sensor for glucose in blood plasma. In their application, Clark and Lyons describe an electrode in which a membrane permeable to glucose traps a small volume of solution containing the enzyme adjacent to a pH electrode, and the presence of glucose is detected by the change in the electrode potential that occurs when glucose reacts with the enzyme in this volume of solution. Although described nearly 50 years ago, this seminal development provides the general structure for constructing electrochemical glucose sensors that is still used today. Despite the maturity of the field, new developments that explore solutions to the fundamental limitations of electrochemical glucose sensors continue to emerge. Here we discuss two developments of the last 15 years; confining the enzyme and a redox mediator to a very thin molecular films at electrode surfaces by electrostatic assembly, and the use of electrodes modified by carbon nanotubes (CNTs to leverage the electrocatalytic effect of the CNTs to reduce the oxidation overpotential of the electrode reaction or for the direct electron transport to the enzyme.

Functionalized active-nucleus complex sensor

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Pines, Alexander; Wemmer, David E.; Spence, Megan; Rubin, Seth

2003-11-25

A functionalized active-nucleus complex sensor that selectively associates with one or more target species, and a method for assaying and screening for one or a plurality of target species utilizing one or a plurality of functionalized active-nucleus complexes with at least two of the functionalized active-nucleus complexes having an attraction affinity to different corresponding target species. The functionalized active-nucleus complex has an active-nucleus and a targeting carrier. The method involves functionalizing an active-nucleus, for each functionalized active-nucleus complex, by incorporating the active-nucleus into a macromolucular or molecular complex that is capable of binding one of the target species and then bringing the macromolecular or molecular complexes into contact with the target species and detecting the occurrence of or change in a nuclear magnetic resonance signal from each of the active-nuclei in each of the functionalized active-nucleus complexes.

Layer-by-Layer Assembly of Glucose Oxidase on Carbon Nanotube Modified Electrodes.

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Suroviec, Alice H

2017-01-01

The use of enzymatically modified electrodes for the detection of glucose or other non-electrochemically active analytes is becoming increasingly common. Direct heterogeneous electron transfer to glucose oxidase has been shown to be kinetically difficult, which is why electron transfer mediators or indirect detection is usually used for monitoring glucose with electrochemical sensors. It has been found, however, that electrodes modified with single or multi-walled carbon nanotubes (CNTs) demonstrate fast heterogeneous electron transfer kinetics as compared to that found for traditional electrodes. Incorporating CNTs into the assembly of electrochemical glucose sensors, therefore, affords the possibility of facile electron transfer to glucose oxidase, and a more direct determination of glucose. This chapter describes the methods used to use CNTs in a layer-by-layer structure along with glucose oxidase to produce an enzymatically modified electrode with high turnover rates, increased stability and shelf-life.

Electrochemical Glucose Biosensor Based on Glucose Oxidase Displayed on Yeast Surface.

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Wang, Hongwei; Lang, Qiaolin; Liang, Bo; Liu, Aihua

2015-01-01

The conventional enzyme-based biosensor requires chemical or physical immobilization of purified enzymes on electrode surface, which often results in loss of enzyme activity and/or fractions immobilized over time. It is also costly. A major advantage of yeast surface display is that it enables the direct utilization of whole cell catalysts with eukaryote-produced proteins being displayed on the cell surface, providing an economic alternative to traditional production of purified enzymes. Herein, we describe the details of the display of glucose oxidase (GOx) on yeast cell surface and its application in the development of electrochemical glucose sensor. In order to achieve a direct electrochemistry of GOx, the entire cell catalyst (yeast-GOx) was immobilized together with multiwalled carbon nanotubes on the electrode, which allowed sensitive and selective glucose detection.

Graphene Quantum Dots Electrochemistry and Sensitive Electrocatalytic Glucose Sensor Development

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Sanju Gupta

2017-09-01

Full Text Available Graphene quantum dots (GQDs, derived from functionalized graphene precursors are graphene sheets a few nanometers in the lateral dimension having a several-layer thickness. They are zero-dimensional materials with quantum confinement and edge site effects. Intense research interest in GQDs is attributed to their unique physicochemical phenomena arising from the sp2-bonded carbon nanocore surrounded with edged plane functional moieties. In this work, GQDs are synthesized by both solvothermal and hydrothermal techniques, with the optimal size of 5 nm determined using high-resolution transmission electron microscopy, with additional UV-Vis absorption and fluorescence spectroscopy, revealing electronic band signatures in the blue-violet region. Their potential in fundamental (direct electron transfer and applied (enzyme-based glucose biosensor electrochemistry has been practically realized. Glucose oxidase (GOx was immobilized on glassy carbon (GC electrodes modified with GQDs and functionalized graphene (graphene oxide and reduced form. The cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy are used for characterizing the direct electron transfer kinetics and electrocatalytical biosensing. The well-defined quasi-reversible redox peaks were observed under various electrochemical environment and conditions (pH, concentration, scan rate to determine the diffusion coefficient (D and first-order electron transfer rate (kET. The cyclic voltammetry curves showed homogeneous ion transport behavior for GQD and other graphene-based samples with D ranging between 8.45 × 10−9 m2 s−1 and 3 × 10−8 m2 s−1 following the order of GO < rGO < GQD < GQD (with FcMeOH as redox probe < GOx/rGO < GOx/GO < HRP/GQDs < GOx/GQDs. The developed GOx-GQDs biosensor responds efficiently and linearly to the presence of glucose over concentrations ranging between 10 μM and 3 mM with a limit of detection of 1.35 μM and

Glucose biosensor based on glucose oxidase immobilized at gold nanoparticles decorated graphene-carbon nanotubes.

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Devasenathipathy, Rajkumar; Mani, Veerappan; Chen, Shen-Ming; Huang, Sheng-Tung; Huang, Tsung-Tao; Lin, Chun-Mao; Hwa, Kuo-Yuan; Chen, Ting-Yo; Chen, Bo-Jun

2015-10-01

Biopolymer pectin stabilized gold nanoparticles were prepared at graphene and multiwalled carbon nanotubes (GR-MWNTs/AuNPs) and employed for the determination of glucose. The formation of GR-MWNTs/AuNPs was confirmed by scanning electron microscopy, X-ray diffraction, UV-vis and FTIR spectroscopy methods. Glucose oxidase (GOx) was successfully immobilized on GR-MWNTs/AuNPs film and direct electron transfer of GOx was investigated. GOx exhibits highly enhanced redox peaks with formal potential of -0.40 V (vs. Ag/AgCl). The amount of electroactive GOx and electron transfer rate constant were found to be 10.5 × 10(-10) mol cm(-2) and 3.36 s(-1), respectively, which were significantly larger than the previous reports. The fabricated amperometric glucose biosensor sensitively detects glucose and showed two linear ranges: (1) 10 μM - 2 mM with LOD of 4.1 μM, (2) 2 mM - 5.2 mM with LOD of 0.95 mM. The comparison of the biosensor performance with reported sensors reveals the significant improvement in overall sensor performance. Moreover, the biosensor exhibited appreciable stability, repeatability, reproducibility and practicality. The other advantages of the fabricated biosensor are simple and green fabrication approach, roughed and stable electrode surface, fast in sensing and highly reproducible. Copyright © 2015 Elsevier Inc. All rights reserved.

Glucose ameliorates the metabolic profile and mitochondrial function of platelet concentrates during storage in autologous plasma

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Amorini, Angela M.; Tuttobene, Michele; Tomasello, Flora M.; Biazzo, Filomena; Gullotta, Stefano; De Pinto, Vito; Lazzarino, Giuseppe; Tavazzi, Barbara

2013-01-01

Background It is essential that the quality of platelet metabolism and function remains high during storage in order to ensure the clinical effectiveness of a platelet transfusion. New storage conditions and additives are constantly evaluated in order to achieve this. Using glucose as a substrate is controversial because of its potential connection with increased lactate production and decreased pH, both parameters triggering the platelet lesion during storage. Materials and methods In this study, we analysed the morphological status and metabolic profile of platelets stored for various periods in autologous plasma enriched with increasing glucose concentrations (13.75, 27.5 and 55 mM). After 0, 2, 4, 6 and 8 days, high energy phosphates (ATP, GTP, ADP, AMP), oxypurines (hypoxanthine, xanthine, uric acid), lactate, pH, mitochondrial function, cell lysis and morphology, were evaluated. Results The data showed a significant dose-dependent improvement of the different parameters in platelets stored with increasing glucose, compared to what detected in controls. Interestingly, this phenomenon was more marked at the highest level of glucose tested and in the period of time generally used for platelet transfusion (0–6 days). Conclusion These results indicate that the addition of glucose during platelet storage ameliorates, in a dose-dependent manner, the biochemical parameters related to energy metabolism and mitochondrial function. Since there was no correspondence between glucose addition, lactate increase and pH decrease in our experiments, it is conceivable that platelet derangement during storage is not directly caused by glucose through an increase of anaerobic glycolysis, but rather to a loss of mitochondrial functions caused by reduced substrate availability. PMID:22682337

Enhanced non-enzymatic glucose sensing based on copper nanoparticles decorated nitrogen-doped graphene.

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Jiang, Ding; Liu, Qian; Wang, Kun; Qian, Jing; Dong, Xiaoya; Yang, Zhenting; Du, Xiaojiao; Qiu, Baijing

2014-04-15

Copper nanoparticles (NPs) decorated nitrogen-doped graphene (Cu-N-G) was prepared by a facile thermal treatment, and further employed as a novel sensing material for fabricating the sensitive non-enzymatic glucose sensor. Compared with pure Cu NPs, the Cu-N-G showed enhanced electrocatalytic activity to glucose oxidation due to the integration of N-G, which exhibited the oxidation peak current of glucose ca. 23-fold higher than that of pure Cu NPs. The presented sensor showed excellent performances for glucose detection including wide linear range of 0.004-4.5 mM, low detection limit (1.3 μM, S/N=3), high sensitivity (48.13 μA mM(-1)), fast response time (doped graphene as enhanced materials in fabricating sensors for chemical and biochemical analysis. © 2013 Published by Elsevier B.V.

Valsartan Improves β-Cell Function and Insulin Sensitivity in Subjects With Impaired Glucose Metabolism

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van der Zijl, Nynke J.; Moors, Chantalle C.M.; Goossens, Gijs H.; Hermans, Marc M.H.; Blaak, Ellen E.; Diamant, Michaela

2011-01-01

OBJECTIVE Recently, the Nateglinide and Valsartan in Impaired Glucose Tolerance Outcomes Research Trial demonstrated that treatment with the angiotensin receptor blocker (ARB) valsartan for 5 years resulted in a relative reduction of 14% in the incidence of type 2 diabetes in subjects with impaired glucose metabolism (IGM). We investigated whether improvements in β-cell function and/or insulin sensitivity underlie these preventive effects of the ARB valsartan in the onset of type 2 diabetes. RESEARCH DESIGN AND METHODS In this randomized controlled, double-blind, two-center study, the effects of 26 weeks of valsartan (320 mg daily; n = 40) or placebo (n = 39) on β-cell function and insulin sensitivity were assessed in subjects with impaired fasting glucose and/or impaired glucose tolerance, using a combined hyperinsulinemic-euglycemic and hyperglycemic clamp with subsequent arginine stimulation and a 2-h 75-g oral glucose tolerance test (OGTT). Treatment effects were analyzed using ANCOVA, adjusting for center, glucometabolic status, and sex. RESULTS Valsartan increased first-phase (P = 0.028) and second-phase (P = 0.002) glucose-stimulated insulin secretion compared with placebo, whereas the enhanced arginine-stimulated insulin secretion was comparable between groups (P = 0.25). In addition, valsartan increased the OGTT-derived insulinogenic index (representing first-phase insulin secretion after an oral glucose load; P = 0.027). Clamp-derived insulin sensitivity was significantly increased with valsartan compared with placebo (P = 0.049). Valsartan treatment significantly decreased systolic and diastolic blood pressure compared with placebo (P valsartan treatment increased glucose-stimulated insulin release and insulin sensitivity in normotensive subjects with IGM. These findings may partly explain the beneficial effects of valsartan in the reduced incidence of type 2 diabetes. PMID:21330640

The measurement of the nigrostriatal dopaminergic function and glucose metabolism in patients with movement disorders

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Otsuka, Makoto; Ichiya, Yuichi; Kuwabara, Yasuo; Sasaki, Masayuki; Fukumura, Toshimitsu; Masuda, Kouji; Shima, Fumio; Kato, Motohiro (Kyushu Univ., Fukuoka (Japan). Faculty of Medicine)

1992-12-01

The nigrostriatal dopaminergic function and glucose metabolism were evaluated in 34 patients with various movement disorders by using positron emission tomography with [sup 18]F-Dopa and [sup 18]F-FDG respectively. The [sup 18]F-Dopa uptake in the striatum (the caudate head and the putamen) decreased in patients with Parkinson's disease but was relatively unaffected in the caudate. The cerebral glucose metabolism was normal in patients with Parkinson's disease. The [sup 18]F-Dopa uptake in the striatum also decreased in cases of atypical parkinsonism and in cases of progressive supranuclear palsy, but there was no difference in the uptake between the caudate and the putamen. The glucose metabolism decreased in the cerebral hemisphere including the striatum; this finding was also different from those of Parkinson's disease. A normal [sup 18]F-Dopa uptake in the striatum with a markedly decreased striatal glucose metabolism and a mildly decreased cortical glucose metabolism was observed in cases of Huntington's disease and Wilson's disease. The [sup 18]F-Dopa uptake in the striatum increased and the glucose metabolism was normal in cases of idiopathic dystonia. Various patterns of [sup 18]F-Dopa uptake and glucose metabolism were thus observed in the various movement disorders. These results suggest that the measurements of the [sup 18]F-Dopa uptake and the cerebral glucose metabolism would be useful for the evaluation of the striatal function in various movement disorders. (author).

The measurement of the nigrostriatal dopaminergic function and glucose metabolism in patients with movement disorders

Energy Technology Data Exchange (ETDEWEB)

Otsuka, Makoto; Ichiya, Yuichi; Kuwabara, Yasuo; Sasaki, Masayuki; Fukumura, Toshimitsu; Masuda, Kouji; Shima, Fumio; Kato, Motohiro [Kyushu Univ., Fukuoka (Japan). Faculty of Medicine

1992-12-01

The nigrostriatal dopaminergic function and glucose metabolism were evaluated in 34 patients with various movement disorders by using positron emission tomography with [sup 18]F-Dopa and [sup 18]F-FDG respectively. The [sup 18]F-Dopa uptake in the striatum (the caudate head and the putamen) decreased in patients with Parkinson's disease but was relatively unaffected in the caudate. The cerebral glucose metabolism was normal in patients with Parkinson's disease. The [sup 18]F-Dopa uptake in the striatum also decreased in cases of atypical parkinsonism and in cases of progressive supranuclear palsy, but there was no difference in the uptake between the caudate and the putamen. The glucose metabolism decreased in the cerebral hemisphere including the striatum; this finding was also different from those of Parkinson's disease. A normal [sup 18]F-Dopa uptake in the striatum with a markedly decreased striatal glucose metabolism and a mildly decreased cortical glucose metabolism was observed in cases of Huntington's disease and Wilson's disease. The [sup 18]F-Dopa uptake in the striatum increased and the glucose metabolism was normal in cases of idiopathic dystonia. Various patterns of [sup 18]F-Dopa uptake and glucose metabolism were thus observed in the various movement disorders. These results suggest that the measurements of the [sup 18]F-Dopa uptake and the cerebral glucose metabolism would be useful for the evaluation of the striatal function in various movement disorders. (author).

Sugar for the brain: the role of glucose in physiological and pathological brain function.

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Mergenthaler, Philipp; Lindauer, Ute; Dienel, Gerald A; Meisel, Andreas

2013-10-01

The mammalian brain depends upon glucose as its main source of energy, and tight regulation of glucose metabolism is critical for brain physiology. Consistent with its critical role for physiological brain function, disruption of normal glucose metabolism as well as its interdependence with cell death pathways forms the pathophysiological basis for many brain disorders. Here, we review recent advances in understanding how glucose metabolism sustains basic brain physiology. We synthesize these findings to form a comprehensive picture of the cooperation required between different systems and cell types, and the specific breakdowns in this cooperation that lead to disease. Copyright © 2013 Elsevier Ltd. All rights reserved.

Facile synthesis of a silver nanoparticles/polypyrrole nanocomposite for non-enzymatic glucose determination.

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Poletti Papi, Maurício A; Caetano, Fabio R; Bergamini, Márcio F; Marcolino-Junior, Luiz H

2017-06-01

The present work describes the synthesis of a new conductive nanocomposite based on polypyrrole (PPy) and silver nanoparticles (PPy-AgNP) based on a facile reverse microemulsion method and its application as a non-enzymatic electrochemical sensor for glucose detection. Focusing on the best sensor performance, all experimental parameters used in the synthesis of nanocomposite were optimized based on its electrochemical response for glucose. Characterization of the optimized material by FT-IR, cyclic voltammetry, and DRX measurements and TEM images showed good monodispersion of semispherical Ag nanoparticles capped by PPy structure, with size average of 12±5nm. Under the best analytical conditions, the proposed sensor exhibited glucose response in linear dynamic range of 25 to 2500μmolL -1 , with limit of detection of 3.6μmolL -1 . Recovery studies with human saliva samples varying from 99 to 105% revealed the accuracy and feasibility of a non-enzymatic electrochemical sensor for glucose determination by easy construction and low-cost. Copyright © 2017 Elsevier B.V. All rights reserved.

Insulin resistance according to β-cell function in women with polycystic ovary syndrome and normal glucose tolerance.

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Song, Do Kyeong; Hong, Young Sun; Sung, Yeon-Ah; Lee, Hyejin

2017-01-01

Polycystic ovary syndrome (PCOS) is associated with insulin resistance (IR) and compensatory hyperinsulinemia. IR is recognized as a major risk factor for the development of type 2 diabetes mellitus. However, few studies have investigated IR in women with PCOS and normal glucose tolerance. The objective of this study was to evaluate IR and β-cell function in women with PCOS and normal glucose tolerance. Additionally, we sought to evaluate the usefulness of oral glucose tolerance test (OGTT)-derived IR indices in lean women with PCOS. We recruited 100 women with PCOS and normal glucose tolerance and 100 age- and BMI-matched women as controls. IR and insulin secretory indices, including the homeostasis-model assessment (HOMA)-IR, HOMA-M120, HOMA-F and the Stumvoll index, were calculated from an OGTT. Increased β-cell function was defined as>75th percentile for the HOMA-F in control women. Women with PCOS had higher values for post-load 2-hour glucose, fasting insulin, post-load 2-hour insulin, HOMA-IR, HOMA-M120, HOMA-F and lower values for the Stumvoll index than the controls (all PsWomen with PCOS and increased β-cell function showed lower Stumvoll index values than the matched controls (Plean women with PCOS (all PsWomen with PCOS and normal glucose tolerance showed higher IR than controls matched for age, BMI, and β-cell function. β-cell function was increased in women with PCOS when compared to the matched controls, but not when the lean subjects were compared to the matched controls separately. Therefore, early evaluation of IR in women with PCOS and normal glucose tolerance may be needed.

Design of multi-function sensor detection system in coal mine based on ARM

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Ge, Yan-Xiang; Zhang, Quan-Zhu; Deng, Yong-Hong

2017-06-01

The traditional coal mine sensor in the specific measurement points, the number and type of channel will be greater than or less than the number of monitoring points, resulting in a waste of resources or cannot meet the application requirements, in order to enable the sensor to adapt to the needs of different occasions and reduce the cost, a kind of multi-functional intelligent sensor multiple sensors and ARM11 the S3C6410 processor is used to design and realize the dust, gas, temperature and humidity sensor functions together, and has storage, display, voice, pictures, data query, alarm and other new functions.

STUDY ON ALGORITHM OF SENSOR MANAGEMENT BASED ON FUNCTIONS OF EFFICIENCY AND WASTE

Institute of Scientific and Technical Information of China (English)

无

2000-01-01

Sensor management plays an important role in data fusion system, and this paper presents an algorithm of sensor management that can be used in target detection, identification and tracking. First, the basic concept, rule, range and function of sensor management are introduced. Then, the quantifying problems of target priority and sensor (or combination)-target pairing in multisensor management are discussed and the efficiency and waste functions are established based on the functions of target priority and sensor-target pairing. On this basis, a distribution algorithm of multisensor resources is given, which is optimized by the principle of maximum synthesis efficiency in the multisensor system and constrained by sensor maximum tracking power and what target must be scanned. In addition, the waste measure of sensor resources is introduced to improve the algorithm. Finally, a tactical task that includes three sensors and ten targets is set, and the simulation results show that the algorithm is feasible and effective.

Plain to point network reduced graphene oxide - activated carbon composites decorated with platinum nanoparticles for urine glucose detection

Science.gov (United States)

Hossain, Mohammad Faruk; Park, Jae Y.

2016-02-01

In this study, a hydrothermal technique was applied to synthesize glucose-treated reduced graphene oxide-activated carbon (GRGO/AC) composites. Platinum nanoparticles (PtNP) were electrochemically deposited on the modified GRGO/AC surface, and chitosan-glucose oxidase (Chit-GOx) composites and nafion were integrated onto the modified surface of the working electrode to prepare a highly sensitive glucose sensor. The fabricated biosensor exhibited a good amperometric response to glucose in the detection range from 0.002 mM to 10 mM, with a sensitivity of 61.06 μA/mMcm2, a short response time (4 s) and a low detection limit of 2 μM (signal to noise ratio is 3). The glucose sensor exhibited a negligible response to interference and good stability. In addition, the glucose levels in human urine were tested in order to conduct a practical assessment of the proposed sensor, and the results indicate that the sensor had superior urine glucose recognition. These results thus demonstrate that the noble nano-structured electrode with a high surface area and electrocatalytic activity offers great promise for use in urine glucose sensing applications.

A Disposable Tear Glucose Biosensor—Part 4

Science.gov (United States)

Engelschall, Erica; Lan, Kenneth; Shah, Pankti; Saez, Neil; Maxwell, Stephanie; Adamson, Teagan; Abou-Eid, Michelle; McAferty, Kenyon; Patel, Dharmendra R.; Cook, Curtiss B.

2014-01-01

Objective: A prototype tear glucose (TG) sensor was tested in New Zealand white rabbits to assess eye irritation, blood glucose (BG) and TG lag time, and correlation with BG. Methods: A total of 4 animals were used. Eye irritation was monitored by Lissamine green dye and analyzed using image analysis software. Lag time was correlated with an oral glucose load while recording TG and BG readings. Correlation between TG and BG were plotted against one another to form a correlation diagram, using a Yellow Springs Instrument (YSI) and self-monitoring of blood glucose as the reference measurements. Finally, TG levels were calculated using analytically derived expressions. Results: From repeated testing carried over the course of 12 months, little to no eye irritation was detected. TG fluctuations over time visually appeared to trace the same pattern as BG with an average lag times of 13 minutes. TG levels calculated from the device current measurements ranged from 4 to 20 mg/dL and correlated linearly with BG levels of 75-160 mg/dL (TG = 0.1723 BG = 7.9448 mg/dL; R2 = .7544). Conclusion: The first steps were taken toward preliminary development of a sensor for self-monitoring of tear glucose (SMTG). No conjunctival irritation in any of the animals was noted. Lag time between TG and BG was found to be noticeable, but a quantitative modeling to correlate lag time in this study is unnecessary. Measured currents from the sensors and the calculated TG showed promising correlation to BG levels. Previous analytical bench marking showed BG and TG levels consistent with other literature. PMID:24876546

A novel CuO-N-doped graphene nanocomposite-based hybrid electrode for the electrochemical detection of glucose

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Felix, Sathiyanathan; Kollu, Pratap; Jeong, Soon Kwan; Grace, Andrews Nirmala

2017-10-01

We report a catalyst of N-doped graphene CuO nanocomposite, for the non-enzymatic electrocatalytic oxidation of glucose. The hybrid nanocomposite was synthesized by copper sulfate, cetyl ammonium bromide and graphite as starting materials. The synthesized composites were characterized with the techniques like X-ray diffraction, field emission scanning electron microscopy, transmission electron microscope to study the crystalline phase and morphological structure. Based on this composite, a non-enzymatic glucose sensor was constructed. Cyclic voltammetry and chronoamperometry methods were done to investigate the electrocatalytic properties of glucose in alkaline medium. For glucose detection, the fabricated sensor showed a linear response over a wide range of concentration from 3 to 1000 µM, with sensitivity of 2365.7 µA mM-1 cm-2 and a fast response time of 5 s. The designed sensor exhibited negligible current response to the normal concentration of common interferents in the presence of glucose. All these favorable advantages of the fabricated glucose sensor suggest that it may have good potential application in biological samples, food and other related areas.

Towards a continuous glucose monitoring system using tunable quantum cascade lasers

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Haase, Katharina; Müller, Niklas; Petrich, Wolfgang

2018-02-01

We present a reagent-free approach for long-term continuous glucose monitoring (cgm) of liquid samples using midinfrared absorption spectroscopy. This method could constitute an alternative to enzymatic glucose sensors in order to manage the widespread disease of Diabetes. In order to acquire spectra of the liquid specimen, we use a spectrally tunable external-cavity (EC-) quantum cascade laser (QCL) as radiation source in combination with a fiber-based in vitro sensor setup. Hereby we achieve a glucose sensitivity in pure glucose solutions of 3 mg/dL (RMSEP). Furthermore, the spectral tunability of the EC-QCL enables us to discriminate glucose from other molecules. We exemplify this by detecting glucose among other saccharides with an accuracy of 8 mg/dL (within other monosaccharides, RMSEVC) and 14 mg/dL (within other mono- and disaccharides, RMSECV). Moreover, we demonstrate a characterization of the significance of each wavenumber for an accurate prediction of glucose among other saccharides using an evolutionary algorithm. We show, that by picking 10 distinct wavenumbers we can achieve comparable accuracies to the use of a complete spectrum.

Mathematical model of glucose-insulin homeostasis in healthy rats.

Science.gov (United States)

Lombarte, Mercedes; Lupo, Maela; Campetelli, German; Basualdo, Marta; Rigalli, Alfredo

2013-10-01

According to the World Health Organization there are over 220 million people in the world with diabetes and 3.4 million people died in 2004 as a consequence of this pathology. Development of an artificial pancreas would allow to restore control of blood glucose by coupling an infusion pump to a continuous glucose sensor in the blood. The design of such a device requires the development and application of mathematical models which represent the gluco-regulatory system. Models developed by other research groups describe very well the gluco-regulatory system but have a large number of mathematical equations and require complex methodologies for the estimation of its parameters. In this work we propose a mathematical model to study the homeostasis of glucose and insulin in healthy rats. The proposed model consists of three differential equations and 8 parameters that describe the variation of: blood glucose concentration, blood insulin concentration and amount of glucose in the intestine. All parameters were obtained by setting functions to the values of glucose and insulin in blood obtained after oral glucose administration. In vivo and in silico validations were performed. Additionally, a qualitative analysis has been done to verify the aforementioned model. We have shown that this model has a single, biologically consistent equilibrium point. This model is a first step in the development of a mathematical model for the type I diabetic rat. Copyright © 2013 Elsevier Inc. All rights reserved.

Synthesis of tremella-like CoS and its application in sensing of hydrogen peroxide and glucose

Energy Technology Data Exchange (ETDEWEB)

Wu, Wenqin; Yu, Beibei [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education, College of Chemistry & Chemical Engineering, Hubei University, Wuhan 430062 (China); Wu, Huimin, E-mail: whm267@hubu.edu.cn [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education, College of Chemistry & Chemical Engineering, Hubei University, Wuhan 430062 (China); Wang, Shengfu; Xia, Qinghua [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education, College of Chemistry & Chemical Engineering, Hubei University, Wuhan 430062 (China); Ding, Yu [College of Chemistry and Materials Science, Hubei Engineering University, Xiaogan 432000 (China)

2017-01-01

Different phases of cobalt sulfides have been fabricated by one-pot hydrothermal method. Comparing all of the prepared materials, and the results revealed that CoS was the most conductive and could accelerate electron transfer. The CoS presented tremella-like and excellent catalytic activities towards hydrogen peroxide and glucose. The sensor based on CoS performed amperometric sensing of hydrogen peroxide in a linear range between 5.00 μM and 14.82 mM. Meanwhile, sensing of glucose with double-linear range, one is between 5.00 μM and 1.10 mM, the other is between 1.20 mM and 10.20 mM. These due to the fact that more and more intermediate species absorb onto electrode surface with increasing the concentration of glucose, which limit the following glucose oxidation. Furthermore, the hydrogen peroxide and glucose sensors based on tremella-like CoS also exhibited excellent selectivity, stability, and reproducibility. Thus, the sensor showed potential utilities in hydrogen peroxide and glucose detection. - Highlights: • Tremella-like CoS was prepared by an environmentally friendly hydrothermal method. • The CoS exhibited excellent catalytic activity towards hydrogen peroxide and glucose. • The sensors based on CoS can be applied to detect real samples.

Evolutionary ancestry and novel functions of the mammalian glucose transporter (GLUT) family.

Science.gov (United States)

Wilson-O'Brien, Amy L; Patron, Nicola; Rogers, Suzanne

2010-05-21

In general, sugar porters function by proton-coupled symport or facilitative transport modes. Symporters, coupled to electrochemical energy, transport nutrients against a substrate gradient. Facilitative carriers transport sugars along a concentration gradient, thus transport is dependent upon extracellular nutrient levels. Across bacteria, fungi, unicellular non-vertebrates and plants, proton-coupled hexose symport is a crucial process supplying energy under conditions of nutrient flux. In mammals it has been assumed that evolution of whole body regulatory mechanisms would eliminate this need. To determine whether any isoforms bearing this function might be conserved in mammals, we investigated the relationship between the transporters of animals and the proton-coupled hexose symporters found in other species. We took a comparative genomic approach and have performed the first comprehensive and statistically supported phylogenetic analysis of all mammalian glucose transporter (GLUT) isoforms. Our data reveals the mammalian GLUT proteins segregate into five distinct classes. This evolutionary ancestry gives insight to structure, function and transport mechanisms within the groups. Combined with biological assays, we present novel evidence that, in response to changing nutrient availability and environmental pH, proton-coupled, active glucose symport function is maintained in mammalian cells. The analyses show the ancestry, evolutionary conservation and biological importance of the GLUT classes. These findings significantly extend our understanding of the evolution of mammalian glucose transport systems. They also reveal that mammals may have conserved an adaptive response to nutrient demand that would have important physiological implications to cell survival and growth.

The use of two continuous glucose sensors during and after surgery

NARCIS (Netherlands)

Vriesendorp, T. M.; DeVries, J. H.; Holleman, F.; Dzoljic, M.; Hoekstra, J. B. L.

2005-01-01

BACKGROUND: Maintaining plasma glucose between 80 and 120 mg/dL is beneficial for patients admitted to a surgical intensive care unit, but requires frequent glucose monitoring to ensure adequacy of treatment and detection of hypoglycemia. We examined whether continuous glucose sensing is feasible

Cr2O3 nanoparticle-functionalized WO3 nanorods for ethanol gas sensors

Science.gov (United States)

Choi, Seungbok; Bonyani, Maryam; Sun, Gun-Joo; Lee, Jae Kyung; Hyun, Soong Keun; Lee, Chongmu

2018-02-01

Pristine WO3 nanorods and Cr2O3-functionalized WO3 nanorods were synthesized by the thermal evaporation of WO3 powder in an oxidizing atmosphere, followed by spin-coating of the nanowires with Cr2O3 nanoparticles and thermal annealing in an oxidizing atmosphere. Scanning electron microscopy was used to examine the morphological features and X-ray diffraction was used to study the crystallinity and phase formation of the synthesized nanorods. Gas sensing tests were performed at different temperatures in the presence of test gases (ethanol, acetone, CO, benzene and toluene). The Cr2O3-functionalized WO3 nanorods sensor showed a stronger response to these gases relative to the pristine WO3 nanorod sensor. In particular, the response of the Cr2O3-functionalized WO3 nanorods sensor to 200 ppm ethanol gas was 5.58, which is approximately 4.4 times higher that of the pristine WO3 nanorods sensor. Furthermore, the Cr2O3-functionalized WO3 nanorods sensor had a shorter response and recovery time. The pristine WO3 nanorods had no selectivity toward ethanol gas, whereas the Cr2O3-functionalized WO3 nanorods sensor showed good selectivity toward ethanol. The gas sensing mechanism of the Cr2O3-functionalized WO3 nanorods sensor toward ethanol is discussed in detail.

Combined functional CT/FDG-PET: demonstrates reduced hepatic phosphorylation of glucose in advanced colorectal cancer

International Nuclear Information System (INIS)

Miles, K.A.; Keith, C.J.; Griffiths, M.R.; Fuentes, M.; Bunce, I.

2002-01-01

Full text: This study describes a technique to quantify hepatic glucose phosphorylation using combined data from functional CT and FDG-PET and assesses the differences in phosphorylation between patients with either early or advanced colorectal cancer. Functional CT and FDG-PET were utilised to obtain measurements of perfusion and glucose uptake respectively within the livers of a series of 35 patients with colorectal cancer. Patients with PET evidence of extrahepatic tumour were considered to have advanced disease. The net influx constant (Ki) for FDG was determined from the liver SUV. CT measurements of hepatic perfusion were incorporated into FDG kinetic analysis to determine hepatic glucose phosphorylation fraction. SUV and Ki were significantly lower in the 12 patients with advanced disease (p=0.015 and p=0.013 respectively) whereas portal and total hepatic perfusion were increased (p=0.013 and p=0.008 respectively). Combining the PET and CT data yielded phosphorylation fractions of 1.14% and 0.74% for early and advanced disease respectively (p=0.002). Hepatic glucose phosphorylation can be determined by combining functional CT measurements of perfusion with PET measurements of FDG and is significantly reduced in patients with more advanced malignancy. Reduced hepatic glucose phosphorylation may be an important mechanism in the development of cancer cachexia. Copyright (2002) The Australian and New Zealand Society of Nuclear Medicine Inc

Combined functional CT/FDG-PET: demonstrates reduced hepatic phosphorylation of glucose in advanced colorectal cancer

Energy Technology Data Exchange (ETDEWEB)

Miles, K A [Southernex Imaging Group, QLD (Australia); Queensland University of Technology, QLD (Australia); Keith, C J [Southernex Imaging Group, QLD (Australia); Wesley Research Institute, QLD (Australia); Griffiths, M R [Queensland University of Technology, QLD (Australia); Fuentes, M [Southernex Imaging Group, QLD (Australia); Bunce, I [Wesley Research Institute, QLD (Australia)

2002-07-01

Full text: This study describes a technique to quantify hepatic glucose phosphorylation using combined data from functional CT and FDG-PET and assesses the differences in phosphorylation between patients with either early or advanced colorectal cancer. Functional CT and FDG-PET were utilised to obtain measurements of perfusion and glucose uptake respectively within the livers of a series of 35 patients with colorectal cancer. Patients with PET evidence of extrahepatic tumour were considered to have advanced disease. The net influx constant (Ki) for FDG was determined from the liver SUV. CT measurements of hepatic perfusion were incorporated into FDG kinetic analysis to determine hepatic glucose phosphorylation fraction. SUV and Ki were significantly lower in the 12 patients with advanced disease (p=0.015 and p=0.013 respectively) whereas portal and total hepatic perfusion were increased (p=0.013 and p=0.008 respectively). Combining the PET and CT data yielded phosphorylation fractions of 1.14% and 0.74% for early and advanced disease respectively (p=0.002). Hepatic glucose phosphorylation can be determined by combining functional CT measurements of perfusion with PET measurements of FDG and is significantly reduced in patients with more advanced malignancy. Reduced hepatic glucose phosphorylation may be an important mechanism in the development of cancer cachexia. Copyright (2002) The Australian and New Zealand Society of Nuclear Medicine Inc.

High fat diet-induced glucose intolerance impairs myocardial function, but not myocardial perfusion during hyperaemia: a pilot study

Directory of Open Access Journals (Sweden)

van den Brom Charissa E

2012-06-01

Full Text Available Abstract Background Glucose intolerance is a major health problem and is associated with increased risk of progression to type 2 diabetes mellitus and cardiovascular disease. However, whether glucose intolerance is related to impaired myocardial perfusion is not known. The purpose of the present study was to study the effect of diet-induced glucose intolerance on myocardial function and perfusion during baseline and pharmacological induced hyperaemia. Methods Male Wistar rats were randomly exposed to a high fat diet (HFD or control diet (CD (n = 8 per group. After 4 weeks, rats underwent an oral glucose tolerance test. Subsequently, rats underwent (contrast echocardiography to determine myocardial function and perfusion during baseline and dipyridamole-induced hyperaemia (20 mg/kg for 10 min. Results Four weeks of HFD feeding resulted in glucose intolerance compared to CD-feeding. Contractile function as represented by fractional shortening was not altered in HFD-fed rats compared to CD-fed rats under baseline conditions. However, dipyridamole increased fractional shortening in CD-fed rats, but not in HFD-fed rats. Basal myocardial perfusion, as measured by estimate of perfusion, was similar in CD- and HFD-fed rats, whereas dipyridamole increased estimate of perfusion in CD-fed rats, but not in HFD-fed rats. However, flow reserve was not different between CD- and HFD-fed rats. Conclusions Diet-induced glucose intolerance is associated with impaired myocardial function during conditions of hyperaemia, but myocardial perfusion is maintained. These findings may result in new insights into the effect of glucose intolerance on myocardial function and perfusion during hyperaemia.

Preparation and characterization of nickel oxide nanoparticles and their application in glucose and methanol sensing

Directory of Open Access Journals (Sweden)

Mahsa Hasanzadeh

2015-03-01

Full Text Available In this work, a low cost glucose and methanol nonenzymatic sensor was prepared using nickel oxide (NiO nanofilm electrodeposited on a bare Cu electrode. Electrochemical deposition was assisted with cetyl trimethylammonium bromide (CTAB as a template. Scanning electron microscopy (SEM was applied to observe the surface morphology of the modified electrode. Cyclic voltammetry (CV and amperometry techniques were used to study the electrocatalytic behavior of NiO porous film in glucose and methanol detection. For glucose sensing, the electrode showed a linear relationship in the concentration range of 0.01-2.14 mM with a low limit of detection (LOD 1.7 µM (signal/noise ratio (S/N=3. Moreover, high sensitivities of 4.02 mA mM−1 cm−2 and 0.38 mA mM−1 cm−2 respectively in glucose and methanol monitoring suggested the modified electrode as an excellent sensor. The NiO-Cu modified electrode was relatively insensitive to common biological interferers. This sensor possessed good poison resistance towards chloride ions, and long term stability and significant selectivity towards glucose and methanol. Finally the proposed sensor was successfully applied for determination of glucose in human blood serum samples.

Cognitive function in adult offspring of women with gestational diabetes-the role of glucose and other factors

DEFF Research Database (Denmark)

Clausen, Tine D; Mortensen, Erik Lykke; Schmidt, Lone

2013-01-01

We aimed to evaluate cognitive function in adult offspring of women with diet-treated gestational diabetes and to study potential associations with maternal glucose values.......We aimed to evaluate cognitive function in adult offspring of women with diet-treated gestational diabetes and to study potential associations with maternal glucose values....

Graphene Electronic Device Based Biosensors and Chemical Sensors

Science.gov (United States)

Jiang, Shan

Two-dimensional layered materials, such as graphene and MoS2, are emerging as an exciting material system for a new generation of atomically thin electronic devices. With their ultrahigh surface to volume ratio and excellent electrical properties, 2D-layered materials hold the promise for the construction of a generation of chemical and biological sensors with unprecedented sensitivity. In my PhD thesis, I mainly focus on graphene based electronic biosensors and chemical sensors. In the first part of my thesis, I demonstrated the fabrication of graphene nanomesh (GNM), which is a graphene thin film with a periodic array of holes punctuated in it. The periodic holes introduce long periphery active edges that provide a high density of functional groups (e.g. carboxylic groups) to allow for covalent grafting of specific receptor molecules for chemical and biosensor applications. After covalently functionalizing the GNM with glucose oxidase, I managed to make a novel electronic sensor which can detect glucose as well as pH change. In the following part of my thesis I demonstrate the fabrication of graphene-hemin conjugate for nitric oxide detection. The non-covalent functionalization through pi-pi stacking interaction allows reliable immobilization of hemin molecules on graphene without damaging the graphene lattice to ensure the highly sensitive and specific detection of nitric oxide. The graphene-hemin nitric oxide sensor is capable of real-time monitoring of nitric oxide concentrations, which is of central importance for probing the diverse roles of nitric oxide in neurotransmission, cardiovascular systems, and immune responses. Our studies demonstrate that the graphene-hemin sensors can respond rapidly to nitric oxide in physiological environments with sub-nanomolar sensitivity. Furthermore, in vitro studies show that the graphene-hemin sensors can be used for the detection of nitric oxide released from macrophage cells and endothelial cells, demonstrating their

Longitudinal Residential Ambient Monitoring: Correlating Sensor Data to Functional Health Status

NARCIS (Netherlands)

Robben, S.; Kröse, B.

2013-01-01

Wireless sensor networks are becoming popular in the field of ambient assisted living. In this paper we report our study on the relationship between a functional health metric and features derived from the sensor data. Sensor systems are installed in the houses of nine people who are also quarterly

Fault and meal detection by redundant continuous glucose monitors and the unscented Kalman filter

DEFF Research Database (Denmark)

Mahmoudi, Zeinab; Nørgaard, Kirsten; Poulsen, Niels Kjølstad

2017-01-01

The purpose of this study is to develop a method for detecting and compensating the anomalies of continuous glucose monitoring (CGM) sensors as well as detecting unannounced meals. Both features, sensor fault detection/correction and meal detection, are necessary to have a reliable artificial pan...... is corrupted by PISA. The fault isolator can detect 199 out of 200 unannounced meals. The average change in the glucose concentrations between the meals and the detection time points is 46.3 mg/dL.......The purpose of this study is to develop a method for detecting and compensating the anomalies of continuous glucose monitoring (CGM) sensors as well as detecting unannounced meals. Both features, sensor fault detection/correction and meal detection, are necessary to have a reliable artificial...... from the two fault detectors differentiates between a sensor fault and an unannounced meal appearing as an anomaly in the CGM data. If the fault isolator indicates a sensor fault, a method based on the covariance matching technique tunes the covariance of the measurement noise associated...

Dysregulation of glucose metabolism even in Chinese PCOS women with normal glucose tolerance.

Science.gov (United States)

Li, Weiping; Li, Qifu

2012-01-01

To clarify the necessity of improving glucose metabolism in polycystic ovary syndrome (PCOS) women as early as possible, 111 PCOS women with normal glucose tolerance and 92 healthy age-matched controls were recruited to investigate glucose levels distribution, insulin sensitivity and β cell function. 91 PCOS women and 33 controls underwent hyperinsulinemic-euglycemic clamp to assess their insulin sensitivity, which was expressed as M value. β cell function was estimated by homeostatic model assessment (HOMA)-β index after adjusting insulin sensitivity (HOMA-βad index). Compared with lean controls, lean PCOS women had similar fasting plasma glucose (FPG), higher postprandial plasma glucose (PPG) (6.03±1.05 vs. 5.44±0.97 mmol/L, PPCOS women had higher levels of both FPG (5.24±0.58 vs. 4.90±0.39, PPCOS women separately, and the cutoff of BMI indicating impaired β cell function of PCOS women was 25.545kg/m². In conclusion, insulin resistance and dysregulation of glucose metabolism were common in Chinese PCOS women with normal glucose tolerance. BMI ≥ 25.545kg/m² indicated impaired β cell function in PCOS women with normal glucose tolerance.

Cloning and functional expression of a human pancreatic islet glucose-transporter cDNA

International Nuclear Information System (INIS)

Permutt, M.A.; Koranyi, L.; Keller, K.; Lacy, P.E.; Scharp, D.W.; Mueckler, M.

1989-01-01

Previous studies have suggested that pancreatic islet glucose transport is mediated by a high-K m , low-affinity facilitated transporter similar to that expressed in liver. To determine the relationship between islet and liver glucose transporters, liver-type glucose-transporter cDNA clones were isolated from a human liver cDNA library. The liver-type glucose-transporter cDNA clone hybridized to mRNA transcripts of the same size in human liver and pancreatic islet RNA. A cDNA library was prepared from purified human pancreatic islet tissue and screened with human liver-type glucose-transporter cDNA. The authors isolated two overlapping cDNA clones encompassing 2600 base pairs, which encode a pancreatic islet protein identical in sequence to that of the putative liver-type glucose-transporter protein. Xenopus oocytes injected with synthetic mRNA transcribed from a full-length cDNA construct exhibited increased uptake of 2-deoxyglucose, confirming the functional identity of the clone. These cDNA clones can now be used to study regulation of expression of the gene and to assess the role of inherited defects in this gene as a candidate for inherited susceptibility to non-insulin-dependent diabetes mellitus

Direct determination of glucose, lactate and triglycerides in blood serum by a tunable quantum cascade laser-based mid-IR sensor

Science.gov (United States)

Brandstetter, M.; Volgger, L.; Genner, A.; Jungbauer, C.; Lendl, B.

2013-02-01

This work reports on a compact sensor for fast and reagent-free point-of-care determination of glucose, lactate and triglycerides in blood serum based on a tunable (1030-1230 cm-1) external-cavity quantum cascade laser (EC-QCL). For simple and robust operation a single beam set-up was designed and only thermoelectric cooling was used for the employed laser and detector. Full computer control of analysis including liquid handling and data analysis facilitated routine measurements. A high optical pathlength (>100 μm) is a prerequisite for robust measurements in clinical practice. Hence, the optimum optical pathlength for transmission measurements in aqueous solution was considered in theory and experiment. The experimentally determined maximum signal-to-noise ratio (SNR) was around 140 μm for the QCL blood sensor and around 50 μm for a standard FT-IR spectrometer employing a liquid nitrogen cooled mercury cadmium telluride (MCT) detector. A single absorption spectrum was used to calculate the analyte concentrations simultaneously by using a partial-least-squares (PLS) regression analysis. Glucose was determined in blood serum with a prediction error (RMSEP) of 6.9 mg/dl and triglycerides with an error of cross-validation (RMSECV) of 17.5 mg/dl in a set of 42 different patients. In spiked serum samples the lactate concentration could be determined with an RMSECV of 8.9 mg/dl.

Platinum nanoparticles functionalized nitrogen doped graphene platform for sensitive electrochemical glucose biosensing

International Nuclear Information System (INIS)

Yang, Zhanjun; Cao, Yue; Li, Juan; Jian, Zhiqin; Zhang, Yongcai; Hu, Xiaoya

2015-01-01

Highlights: • An efficient PtNPs@NG nanocomposite was prepared for the immobilization of enzyme. • A novel electrochemical glucose biosensor was constructed based on this PtNPs@NG. • The proposed glucose biosensor showed high sensitivity and low detection limit. • The PtNPs@NG composite provided a promising platform for biosensing applications. - Abstract: In this work, we reported an efficient platinum nanoparticles functionalized nitrogen doped graphene (PtNPs@NG) nanocomposite for devising novel electrochemical glucose biosensor for the first time. The fabricated PtNPs@NG and biosensor were characterized using transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, static water contact angle, UV–vis spectroscopy, electrochemical impedance spectra and cyclic voltammetry, respectively. PtNPs@NG showed large surface area and excellent biocompatibility, and enhanced the direct electron transfer between enzyme molecules and electrode surface. The glucose oxidase (GOx) immobilized on PtNPs@NG nanocomposite retained its bioactivity, and exhibited a surface controlled, quasi-reversible and fast electron transfer process. The constructed glucose biosensor showed wide linear range from 0.005 to 1.1 mM with high sensitivity of 20.31 mA M −1 cm −2 . The detection limit was calculated to be 0.002 mM at signal-to-noise of 3, which showed 20-fold decrease in comparison with single NG-based electrochemical biosensor for glucose. The proposed glucose biosensor also demonstrated excellent selectivity, good reproducibility, acceptable stability, and could be successfully applied in the detection of glucose in serum samples at the applied potential of −0.33 V. This research provided a promising biosensing platform for the development of excellent electrochemical biosensors

Platinum nanoparticles functionalized nitrogen doped graphene platform for sensitive electrochemical glucose biosensing

Energy Technology Data Exchange (ETDEWEB)

Yang, Zhanjun, E-mail: zjyang@yzu.edu.cn; Cao, Yue; Li, Juan; Jian, Zhiqin; Zhang, Yongcai; Hu, Xiaoya

2015-04-29

Highlights: • An efficient PtNPs@NG nanocomposite was prepared for the immobilization of enzyme. • A novel electrochemical glucose biosensor was constructed based on this PtNPs@NG. • The proposed glucose biosensor showed high sensitivity and low detection limit. • The PtNPs@NG composite provided a promising platform for biosensing applications. - Abstract: In this work, we reported an efficient platinum nanoparticles functionalized nitrogen doped graphene (PtNPs@NG) nanocomposite for devising novel electrochemical glucose biosensor for the first time. The fabricated PtNPs@NG and biosensor were characterized using transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, static water contact angle, UV–vis spectroscopy, electrochemical impedance spectra and cyclic voltammetry, respectively. PtNPs@NG showed large surface area and excellent biocompatibility, and enhanced the direct electron transfer between enzyme molecules and electrode surface. The glucose oxidase (GOx) immobilized on PtNPs@NG nanocomposite retained its bioactivity, and exhibited a surface controlled, quasi-reversible and fast electron transfer process. The constructed glucose biosensor showed wide linear range from 0.005 to 1.1 mM with high sensitivity of 20.31 mA M{sup −1} cm{sup −2}. The detection limit was calculated to be 0.002 mM at signal-to-noise of 3, which showed 20-fold decrease in comparison with single NG-based electrochemical biosensor for glucose. The proposed glucose biosensor also demonstrated excellent selectivity, good reproducibility, acceptable stability, and could be successfully applied in the detection of glucose in serum samples at the applied potential of −0.33 V. This research provided a promising biosensing platform for the development of excellent electrochemical biosensors.

Direct measurement of glucose profiles in immobilized yeast gels with a pH-insensitive micro-electrode under anaerobic conditions

NARCIS (Netherlands)

Cronenberg, C.C.H.; Heuvel, van den J.C.; Ottengraf, S.P.P.

1993-01-01

A 10 µm glucose sensor was developed based on a glucose oxidase coated Pt-electrode inserted in a capillary shaft. The internal buffer medium effected in a glucose response that was insensitive for the external pH. The sensor was successfully utilized at pH 4 under anaerobic conditions in gel

Nitrogen functionality of glucose-glycine condensate; Glucose to glycine tono shukugo hanno (shukugobutsuchu no chisso kagobutsu no keitai bunseki)

Energy Technology Data Exchange (ETDEWEB)

Tanaka, C.; Yoshioka, T.; Komano, T.; Mashimo, K.; Wainai, T. [Nihon University, Tokyo (Japan). College of Science and Technology; Sugimoto, Y.; : Miki, Y. [National Institute of Materials and Chemical Research, Tsukuba (Japan)

1996-10-28

In order to clarify a humification process in the early stage of coalification, the nitrogen functionality of prepared glucose-glycine condensate was studied experimentally. In experiment, the condensate was prepared by heating the mixture of glucose, glycine and water in a autoclave at 130{degree}C for 50 hours, and furthermore heating the produced solid material in water at 300{degree}C. After the condensate was hydrocracked, the fraction, condensate and hydrocracking residue were analyzed by elementary analyzer, {sup 13}C-NMR, XPS, FT-IR, capillary GC-FID/NPD and GC-MS. As a result, the glucose-glycine condensate could be arranged on the basis of three types of nitrogen such as pyridine, pyrrole and quaternary amine type. Pyridine type nitrogen increased, while quaternary amine type one decreased with an increase in heating treatment temperature. Rich pyrrole type nitrogen and poor pyridine type one were found in light nitrogen compounds in hydrocracked products. 2 refs., 4 figs., 2 tabs.

Sensing of Salivary Glucose Using Nano-Structured Biosensors.

Science.gov (United States)

Du, Yunqing; Zhang, Wenjun; Wang, Ming L

2016-03-17

The anxiety and pain associated with frequent finger pricking has always been troublesome for diabetics measuring blood glucose (BG) in their daily lives. For this reason, a reliable glucose monitoring system that allows noninvasive measurements is highly desirable. Our main objective is to develop a biosensor that can detect low-level glucose in saliva (physiological range 0.5-20 mg/dL). Salivary glucose (SG) sensors were built using a layer-by-layer self-assembly of single-walled carbon nanotubes, chitosan, gold nanoparticles, and glucose oxidase onto a screen-printed platinum electrode. An electrochemical method was utilized for the quantitative detection of glucose in both buffer solution and saliva samples. A standard spectrophotometric technique was used as a reference method to validate the glucose content of each sample. The disposable glucose sensors have a detection limit of 0.41 mg/dL, a sensitivity of 0.24 μA·s·dL·mg(-1), a linear range of 0.5-20 mg/dL in buffer solution, and a response time of 30 s. A study of 10 healthy subjects was conducted, and SG levels between 1.1 to 10.1 mg/dL were successfully detected. The results revealed that the noninvasive SG monitoring could be an alternative for diabetes self-management at home. This paper is not intended to replace regular BG tests, but to study SG itself as an indicator for the quality of diabetes care. It can potentially help patients control and monitor their health conditions, enabling them to comply with prescribed treatments for diabetes.

Glucose oxidase-modified carbon-felt-reactor coupled with peroxidase-modified carbon-felt-detector for amperometric flow determination of glucose

International Nuclear Information System (INIS)

Wang Yue; Hasebe, Yasushi

2012-01-01

Glucose oxidase (GOx) and horseradish peroxidase (HRP) were covalently immobilized on a porous carbon-felt (CF) by using cyanuric chloride (CC) as a linking reagent. The resulting GOx-modified-CF (GOx-ccCF) was used as column-type enzyme reactor and placed on upstream of the HRP-ccCF-based H 2 O 2 flow-detector to fabricate amperometric flow-biosensor for glucose. Sensor setting conditions and the operational conditions were optimized, and the analytical performance characteristics of the resulting flow-biosensor were evaluated. The chemical modification of the GOx via CC was found to be effective to obtain larger catalytic activity as compared with the physical adsorption. Under the optimized conditions (i.e., volume ratio of the GOx-ccCF-reactor to the HRP-ccCF-detector is 1.0; applied potential is − 0.12 V vs. Ag/AgCl; carrier pH is 6.5; and carrier flow rate is 4.3 ml/min), highly selective and quite reproducible peak current responses toward glucose were obtained: the RSD for 30 consecutive injections of 3 mM glucose was 1.04%, and no serious interferences were observed for fructose, ethanol, uric acid, urea and tartaric acid for the amperometric measurements of glucose. The magnitude of the cathodic peak currents for glucose was linear up to 5 mM (sensitivity, 6.38 ± 0.32 μA/μM) with the limit detection of 9.4 μM (S/N = 3, noise level, 20 nA). The present GOx-ccCF-reactor and HRP-ccCF-detector-coupled flow-glucose biosensor was utilized for the determination of glucose in beverages and liquors, and the analytical results by the sensor were in fairly good agreement with those by the conventional spectrophotometry. - Highlights: ► Glucose oxidase (GOx) and peroxidase (HRP) were modified on carbon-felt. ► GOx-CF reactor and HRP-CF detector-coupled flow glucose biosensor was developed. ► This flow biosensor enabled the determination of glucose in beverages and liquors.

Glucose oxidase-modified carbon-felt-reactor coupled with peroxidase-modified carbon-felt-detector for amperometric flow determination of glucose

Energy Technology Data Exchange (ETDEWEB)

Wang Yue [School of Chemical Engineering, University of Science and Technology LiaoNing, 185 Qianshan Middle Road, High-tech Zone, Anshan, LiaoNing, 114501 (China); Hasebe, Yasushi, E-mail: hasebe@sit.ac.jp [Department of Life Science and Green Chemistry, Faculty of Engineering, Saitama Institute of Technology, 1690, Fusaiji, Fukaya, Saitama 369-0293 (Japan)

2012-04-01

Glucose oxidase (GOx) and horseradish peroxidase (HRP) were covalently immobilized on a porous carbon-felt (CF) by using cyanuric chloride (CC) as a linking reagent. The resulting GOx-modified-CF (GOx-ccCF) was used as column-type enzyme reactor and placed on upstream of the HRP-ccCF-based H{sub 2}O{sub 2} flow-detector to fabricate amperometric flow-biosensor for glucose. Sensor setting conditions and the operational conditions were optimized, and the analytical performance characteristics of the resulting flow-biosensor were evaluated. The chemical modification of the GOx via CC was found to be effective to obtain larger catalytic activity as compared with the physical adsorption. Under the optimized conditions (i.e., volume ratio of the GOx-ccCF-reactor to the HRP-ccCF-detector is 1.0; applied potential is - 0.12 V vs. Ag/AgCl; carrier pH is 6.5; and carrier flow rate is 4.3 ml/min), highly selective and quite reproducible peak current responses toward glucose were obtained: the RSD for 30 consecutive injections of 3 mM glucose was 1.04%, and no serious interferences were observed for fructose, ethanol, uric acid, urea and tartaric acid for the amperometric measurements of glucose. The magnitude of the cathodic peak currents for glucose was linear up to 5 mM (sensitivity, 6.38 {+-} 0.32 {mu}A/{mu}M) with the limit detection of 9.4 {mu}M (S/N = 3, noise level, 20 nA). The present GOx-ccCF-reactor and HRP-ccCF-detector-coupled flow-glucose biosensor was utilized for the determination of glucose in beverages and liquors, and the analytical results by the sensor were in fairly good agreement with those by the conventional spectrophotometry. - Highlights: Black-Right-Pointing-Pointer Glucose oxidase (GOx) and peroxidase (HRP) were modified on carbon-felt. Black-Right-Pointing-Pointer GOx-CF reactor and HRP-CF detector-coupled flow glucose biosensor was developed. Black-Right-Pointing-Pointer This flow biosensor enabled the determination of glucose in beverages and

Evolutionary ancestry and novel functions of the mammalian glucose transporter (GLUT family

Directory of Open Access Journals (Sweden)

Patron Nicola

2010-05-01

Full Text Available Abstract Background In general, sugar porters function by proton-coupled symport or facilitative transport modes. Symporters, coupled to electrochemical energy, transport nutrients against a substrate gradient. Facilitative carriers transport sugars along a concentration gradient, thus transport is dependent upon extracellular nutrient levels. Across bacteria, fungi, unicellular non-vertebrates and plants, proton-coupled hexose symport is a crucial process supplying energy under conditions of nutrient flux. In mammals it has been assumed that evolution of whole body regulatory mechanisms would eliminate this need. To determine whether any isoforms bearing this function might be conserved in mammals, we investigated the relationship between the transporters of animals and the proton-coupled hexose symporters found in other species. Results We took a comparative genomic approach and have performed the first comprehensive and statistically supported phylogenetic analysis of all mammalian glucose transporter (GLUT isoforms. Our data reveals the mammalian GLUT proteins segregate into five distinct classes. This evolutionary ancestry gives insight to structure, function and transport mechanisms within the groups. Combined with biological assays, we present novel evidence that, in response to changing nutrient availability and environmental pH, proton-coupled, active glucose symport function is maintained in mammalian cells. Conclusions The analyses show the ancestry, evolutionary conservation and biological importance of the GLUT classes. These findings significantly extend our understanding of the evolution of mammalian glucose transport systems. They also reveal that mammals may have conserved an adaptive response to nutrient demand that would have important physiological implications to cell survival and growth.

Continuous non-invasive blood glucose monitoring by spectral image differencing method

Science.gov (United States)

Huang, Hao; Liao, Ningfang; Cheng, Haobo; Liang, Jing

2018-01-01

Currently, the use of implantable enzyme electrode sensor is the main method for continuous blood glucose monitoring. But the effect of electrochemical reactions and the significant drift caused by bioelectricity in body will reduce the accuracy of the glucose measurements. So the enzyme-based glucose sensors need to be calibrated several times each day by the finger-prick blood corrections. This increases the patient's pain. In this paper, we proposed a method for continuous Non-invasive blood glucose monitoring by spectral image differencing method in the near infrared band. The method uses a high-precision CCD detector to switch the filter in a very short period of time, obtains the spectral images. And then by using the morphological method to obtain the spectral image differences, the dynamic change of blood sugar is reflected in the image difference data. Through the experiment proved that this method can be used to monitor blood glucose dynamically to a certain extent.

U-Shaped and Surface Functionalized Polymer Optical Fiber Probe for Glucose Detection.

Science.gov (United States)

Azkune, Mikel; Ruiz-Rubio, Leire; Aldabaldetreku, Gotzon; Arrospide, Eneko; Pérez-Álvarez, Leyre; Bikandi, Iñaki; Zubia, Joseba; Vilas-Vilela, Jose Luis

2017-12-25

In this work we show an optical fiber evanescent wave absorption probe for glucose detection in different physiological media. High selectivity is achieved by functionalizing the surface of an only-core poly(methyl methacrylate) (PMMA) polymer optical fiber with phenilboronic groups, and enhanced sensitivity by using a U-shaped geometry. Employing a supercontinuum light source and a high-resolution spectrometer, absorption measurements are performed in the broadband visible light spectrum. Experimental results suggest the feasibility of such a fiber probe as a low-cost and selective glucose detector.

Expression, purification, and functional characterization of the insulin-responsive facilitative glucose transporter GLUT4.

Science.gov (United States)

Kraft, Thomas E; Hresko, Richard C; Hruz, Paul W

2015-12-01

The insulin-responsive facilitative glucose transporter GLUT4 is of fundamental importance for maintenance of glucose homeostasis. Despite intensive effort, the ability to express and purify sufficient quantities of structurally and functionally intact protein for biophysical analysis has previously been exceedingly difficult. We report here the development of novel methods to express, purify, and functionally reconstitute GLUT4 into detergent micelles and proteoliposomes. Rat GLUT4 containing FLAG and His tags at the amino and carboxy termini, respectively, was engineered and stably transfected into HEK-293 cells. Overexpression in suspension culture yielded over 1.5 mg of protein per liter of culture. Systematic screening of detergent solubilized GLUT4-GFP fusion protein via fluorescent-detection size exclusion chromatography identified lauryl maltose neopentyl glycol (LMNG) as highly effective for isolating monomeric GLUT4 micelles. Preservation of structural integrity and ligand binding was demonstrated via quenching of tryptophan fluorescence and competition of ATB-BMPA photolabeling by cytochalasin B. GLUT4 was reconstituted into lipid nanodiscs and proper folding was confirmed. Reconstitution of purified GLUT4 with amphipol A8-35 stabilized the transporter at elevated temperatures for extended periods of time. Functional activity of purified GLUT4 was confirmed by reconstitution of LMNG-purified GLUT4 into proteoliposomes and measurement of saturable uptake of D-glucose over L-glucose. Taken together, these data validate the development of an efficient means to generate milligram quantities of stable and functionally intact GLUT4 that is suitable for a wide array of biochemical and biophysical analyses. © 2015 The Protein Society.

Utilization of highly purified single wall carbon nanotubes dispersed in polymer thin films for an improved performance of an electrochemical glucose sensor

Energy Technology Data Exchange (ETDEWEB)

Goornavar, Virupaxi [Molecular Toxicology Laboratory, Center for Biotechnology and Biomedical Sciences, Norfolk State University, 700 Park Avenue, Norfolk, VA 23504 (United States); Center for Materials Research, Norfolk State University, 555 Park Avenue, Norfolk, VA 23504 (United States); Jeffers, Robert [Molecular Toxicology Laboratory, Center for Biotechnology and Biomedical Sciences, Norfolk State University, 700 Park Avenue, Norfolk, VA 23504 (United States); Luna Innovations, Inc., 706 Forest St., Suite A, Charlottesville, VA 22902 (United States); Biradar, Santoshkumar [RICE University, 6100 Main St, Houston, TX 77251 (United States); Ramesh, Govindarajan T., E-mail: gtramesh@nsu.edu [Molecular Toxicology Laboratory, Center for Biotechnology and Biomedical Sciences, Norfolk State University, 700 Park Avenue, Norfolk, VA 23504 (United States); Center for Materials Research, Norfolk State University, 555 Park Avenue, Norfolk, VA 23504 (United States)

2014-07-01

In this work we report the improved performance an electrochemical glucose sensor based on a glassy carbon electrode (GCE) that has been modified with highly purified single wall carbon nanotubes (SWCNTs) dispersed in polyethyleneimine (PEI), polyethylene glycol (PEG) and polypyrrole (PPy). The single wall carbon nanotubes were purified by both thermal and chemical oxidation to achieve maximum purity of ∼ 98% with no damage to the tubes. The SWCNTs were then dispersed by sonication in three different organic polymers (1.0 mg/ml SWCNT in 1.0 mg/ml of organic polymer). The stable suspension was coated onto the GCE and electrochemical characterization was performed by Cyclic Voltammetry (CV) and Amperometry. The electroactive enzyme glucose oxidase (GOx) was immobilized on the surface of the GCE/(organic polymer–SWCNT) electrode. The amperometric detection of glucose was carried out at 0.7 V versus Ag/AgCl. The GCE/(SWCNT–PEI, PEG, PPY) gave a detection limit of 0.2633 μM, 0.434 μM, and 0.9617 μM, and sensitivities of 0.2411 ± 0.0033 μA mM{sup −1}, r{sup 2} = 0.9984, 0.08164 ± 0.001129 μA mM{sup −1}, r{sup 2} = 0.9975, 0.04189 ± 0.00087 μA mM{sup −1}, and r{sup 2} = 0.9944 respectively and a response time of less than 5 s. The use of purified SWCNTs has several advantages, including fast electron transfer rate and stability in the immobilized enzyme. The significant enhancement of the SWCNT modified electrode as a glucose sensor can be attributed to the superior conductivity and large surface area of the well dispersed purified SWCNTs. - Highlights: • Purification method employed here use cheap and green oxidants. • The method does not disrupt the electronic structure of nanotubes. • This method removes nearly < 2% metallic impurities. • Increases the sensitivity and performance of glassy carbon electrode • This system can detect as low as 0.066 μM of H{sub 2}O{sub 2} and 0.2633 μM of glucose.

Development and testing of a fluorescence biosensor for glucose sensing

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Aloraefy, Mamdouh; Pfefer, Joshua; Ramella-Roman, Jessica; Sapsford, Kim

2012-06-01

Rapid, accurate, and minimally-invasive biosensors for glucose measurement have the potential to enhance management of diabetes mellitus and improve patient outcome in intensive care settings. Recent studies have indicated that implantable biosensors based on Förster Resonance Energy Transfer (FRET) can provide high sensitivity in quantifying glucose concentrations. However, standard approaches for determining the potential for interference from other biological constituents have not been established. The aim of this work was to design and optimize a FRET-based glucose sensor and assess its specificity to glucose. A sensor based on competitive binding between concanavalin A and dextran, labeled with long-wavelength acceptor and donor fluorophores, was developed. This process included optimization of dextran molecular weight and donor concentration, acceptor to donor ratio, and hydrogel concentration, as well as the number of polymer layers for encapsulation. The biosensor performance was characterized in terms of its response to clinically relevant glucose concentrations. The potential for interference and the development of test methods to evaluate this effect were studied using a potential clinical interferent, maltose. Results indicated that our biosensor had a prediction accuracy of better than 11% and that the robustness to maltose was highly dependent on glucose level.

Dynamic Functional Imaging of Brain Glucose Utilization using fPET-FDG

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Villien, Marjorie; Wey, Hsiao-Ying; Mandeville, Joseph B.; Catana, Ciprian; Polimeni, Jonathan R.; Sander, Christin Y.; Zürcher, Nicole R.; Chonde, Daniel B.; Fowler, Joanna S.; Rosen, Bruce R.; Hooker, Jacob M.

2014-01-01

Glucose is the principal source of energy for the brain and yet the dynamic response of glucose utilization to changes in brain activity is still not fully understood. Positron emission tomography (PET) allows quantitative measurement of glucose metabolism using 2-[18F]-fluorodeoxyglucose (FDG). However, FDG PET in its current form provides an integral (or average) of glucose consumption over tens of minutes and lacks the temporal information to capture physiological alterations associated with changes in brain activity induced by tasks or drug challenges. Traditionally, changes in glucose utilization are inferred by comparing two separate scans, which significantly limits the utility of the method. We report a novel method to track changes in FDG metabolism dynamically, with higher temporal resolution than exists to date and within a single session. Using a constant infusion of FDG, we demonstrate that our technique (termed fPET-FDG) can be used in an analysis pipeline similar to fMRI to define within-session differential metabolic responses. We use visual stimulation to demonstrate the feasibility of this method. This new method has a great potential to be used in research protocols and clinical settings since fPET-FDG imaging can be performed with most PET scanners and data acquisition and analysis is straightforward. fPET-FDG is a highly complementary technique to MRI and provides a rich new way to observe functional changes in brain metabolism. PMID:24936683

Brain glucose metabolism during hypoglycemia in type 1 diabetes: insights from functional and metabolic neuroimaging studies.

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Rooijackers, Hanne M M; Wiegers, Evita C; Tack, Cees J; van der Graaf, Marinette; de Galan, Bastiaan E

2016-02-01

Hypoglycemia is the most frequent complication of insulin therapy in patients with type 1 diabetes. Since the brain is reliant on circulating glucose as its main source of energy, hypoglycemia poses a threat for normal brain function. Paradoxically, although hypoglycemia commonly induces immediate decline in cognitive function, long-lasting changes in brain structure and cognitive function are uncommon in patients with type 1 diabetes. In fact, recurrent hypoglycemia initiates a process of habituation that suppresses hormonal responses to and impairs awareness of subsequent hypoglycemia, which has been attributed to adaptations in the brain. These observations sparked great scientific interest into the brain's handling of glucose during (recurrent) hypoglycemia. Various neuroimaging techniques have been employed to study brain (glucose) metabolism, including PET, fMRI, MRS and ASL. This review discusses what is currently known about cerebral metabolism during hypoglycemia, and how findings obtained by functional and metabolic neuroimaging techniques contributed to this knowledge.

Software sensors as a tool for optimization of animal-cell cultures

NARCIS (Netherlands)

Dorresteijn, R.C.

1997-01-01

In this thesis software sensors are introduced that predict the biomass activity and the concentrations of glucose, glutamine, lactic acid, and ammonium on line, The software sensors for biomass activity, glucose and lactic acid can be applied for any type of animal cell that is grown in a

Insulin resistance according to β-cell function in women with polycystic ovary syndrome and normal glucose tolerance.

Directory of Open Access Journals (Sweden)

Do Kyeong Song

Full Text Available Polycystic ovary syndrome (PCOS is associated with insulin resistance (IR and compensatory hyperinsulinemia. IR is recognized as a major risk factor for the development of type 2 diabetes mellitus. However, few studies have investigated IR in women with PCOS and normal glucose tolerance. The objective of this study was to evaluate IR and β-cell function in women with PCOS and normal glucose tolerance. Additionally, we sought to evaluate the usefulness of oral glucose tolerance test (OGTT-derived IR indices in lean women with PCOS.We recruited 100 women with PCOS and normal glucose tolerance and 100 age- and BMI-matched women as controls. IR and insulin secretory indices, including the homeostasis-model assessment (HOMA-IR, HOMA-M120, HOMA-F and the Stumvoll index, were calculated from an OGTT. Increased β-cell function was defined as>75th percentile for the HOMA-F in control women.Women with PCOS had higher values for post-load 2-hour glucose, fasting insulin, post-load 2-hour insulin, HOMA-IR, HOMA-M120, HOMA-F and lower values for the Stumvoll index than the controls (all Ps<0.05. Women with PCOS and increased β-cell function showed lower Stumvoll index values than the matched controls (P<0.05. The HOMA-F was significantly associated with the HOMA-M120 and Stumvoll index when adjusted for age and BMI in a multiple regression analysis (all Ps<0.05. The HOMA-M120 was positively correlated with triglycerides and free testosterone, and the Stumvoll index was negatively correlated with triglycerides and free testosterone in lean women with PCOS (all Ps<0.05.Women with PCOS and normal glucose tolerance showed higher IR than controls matched for age, BMI, and β-cell function. β-cell function was increased in women with PCOS when compared to the matched controls, but not when the lean subjects were compared to the matched controls separately. Therefore, early evaluation of IR in women with PCOS and normal glucose tolerance may be needed.

Basal Forebrain Cholinergic Deficits Reduce Glucose Metabolism and Function of Cholinergic and GABAergic Systems in the Cingulate Cortex

OpenAIRE

Jeong, Da Un; Oh, Jin Hwan; Lee, Ji Eun; Lee, Jihyeon; Cho, Zang Hee; Chang, Jin Woo; Chang, Won Seok

2015-01-01

Purpose Reduced brain glucose metabolism and basal forebrain cholinergic neuron degeneration are common features of Alzheimer's disease and have been correlated with memory function. Although regions representing glucose hypometabolism in patients with Alzheimer's disease are targets of cholinergic basal forebrain neurons, the interaction between cholinergic denervation and glucose hypometabolism is still unclear. The aim of the present study was to evaluate glucose metabolism changes caused ...

Reversible changes in brain glucose metabolism following thyroid function normalization in hyperthyroidism.

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Miao, Q; Zhang, S; Guan, Y H; Ye, H Y; Zhang, Z Y; Zhang, Q Y; Xue, R D; Zeng, M F; Zuo, C T; Li, Y M

2011-01-01

Patients with hyperthyroidism frequently present with regional cerebral metabolic changes, but the consequences of endocrine-induced brain changes after thyroid function normalization are unclear. We hypothesized that the changes of regional cerebral glucose metabolism are related to thyroid hormone levels in patients with hyperthyroid, and some of these changes can be reversed with antithyroid therapy. Relative regional cerebral glucose metabolism was compared between 10 new-onset untreated patients with hyperthyroidism and 20 healthy control participants by using brain FDG-PET scans. Levels of emotional distress were evaluated by using the SAS and SDS. Patients were treated with methimazole. A follow-up PET scan was performed to assess metabolic changes of the brain when thyroid functions normalized. Compared with controls, patients exhibited lower activity in the limbic system, frontal lobes, and temporal lobes before antithyroid treatment. There were positive correlations between scores of depression and regional metabolism in the cingulate and paracentral lobule. The severity of depression and anxiety covaried negatively with pretreatment activity in the inferior temporal and inferior parietal gyri respectively. Compared with the hyperthyroid status, patients with normalized thyroid functions showed an increased metabolism in the left parahippocampal, fusiform, and right superior frontal gyri. The decrease in both FT3 and FT4 was associated with increased activity in the left parahippocampal and right superior frontal gyri. The changes of regional cerebral glucose metabolism are related to thyroid hormone levels in patients with hyperthyroidism, and some cerebral hypometabolism can be improved after antithyroid therapy.

Rational redesign of glucose oxidase for improved catalytic function and stability.

Directory of Open Access Journals (Sweden)

J Todd Holland

Full Text Available Glucose oxidase (GOx is an enzymatic workhorse used in the food and wine industries to combat microbial contamination, to produce wines with lowered alcohol content, as the recognition element in amperometric glucose sensors, and as an anodic catalyst in biofuel cells. It is naturally produced by several species of fungi, and genetic variants are known to differ considerably in both stability and activity. Two of the more widely studied glucose oxidases come from the species Aspergillus niger (A. niger and Penicillium amagasakiense (P. amag., which have both had their respective genes isolated and sequenced. GOx from A. niger is known to be more stable than GOx from P. amag., while GOx from P. amag. has a six-fold superior substrate affinity (K(M and nearly four-fold greater catalytic rate (k(cat. Here we sought to combine genetic elements from these two varieties to produce an enzyme displaying both superior catalytic capacity and stability. A comparison of the genes from the two organisms revealed 17 residues that differ between their active sites and cofactor binding regions. Fifteen of these residues in a parental A. niger GOx were altered to either mirror the corresponding residues in P. amag. GOx, or mutated into all possible amino acids via saturation mutagenesis. Ultimately, four mutants were identified with significantly improved catalytic activity. A single point mutation from threonine to serine at amino acid 132 (mutant T132S, numbering includes leader peptide led to a three-fold improvement in k(cat at the expense of a 3% loss of substrate affinity (increase in apparent K(M for glucose resulting in a specify constant (k(cat/K(M of 23.8 (mM(-1 · s(-1 compared to 8.39 for the parental (A. niger GOx and 170 for the P. amag. GOx. Three other mutant enzymes were also identified that had improvements in overall catalysis: V42Y, and the double mutants T132S/T56V and T132S/V42Y, with specificity constants of 31.5, 32.2, and 31.8 mM(-1 · s

Caudal fourth ventricular administration of the AMPK activator 5-aminoimidazole-4-carboxamide-riboside regulates glucose and counterregulatory hormone profiles, dorsal vagal complex metabolosensory neuron function, and hypothalamic Fos expression.

Science.gov (United States)

Ibrahim, Baher A; Tamrakar, Pratistha; Gujar, Amit D; Cherian, Ajeesh Koshy; Briski, Karen P

2013-09-01

This study investigated the hypothesis that estrogen controls hindbrain AMP-activated protein kinase (AMPK) activity and regulation of blood glucose, counterregulatory hormone secretion, and hypothalamic nerve cell transcriptional status. Dorsal vagal complex A2 noradrenergic neurons were laser microdissected from estradiol benzoate (E)- or oil (O)-implanted ovariectomized female rats after caudal fourth ventricular (CV4) delivery of the AMPK activator 5-aminoimidazole-4-carboxamide-riboside (AICAR), for Western blot analysis. E advanced AICAR-induced increases in A2 phospho-AMPK (pAMPK) expression and in blood glucose levels and was required for augmentation of Fos, estrogen receptor-α (ERα), monocarboxylate transporter-2, and glucose transporter-3 protein in A2 neurons and enhancement of corticosterone secretion by this treatment paradigm. CV4 AICAR also resulted in site-specific modifications in Fos immunolabeling of hypothalamic metabolic structures, including the paraventricular, ventromedial, and arcuate nuclei. The current studies demonstrate that estrogen regulates AMPK activation in caudal hindbrain A2 noradrenergic neurons during pharmacological replication of energy shortage in this area of the brain, and that this sensor is involved in neural regulation of glucostasis, in part, through control of corticosterone secretion. The data provide unique evidence that A2 neurons express both ERα and -β proteins and that AMPK upregulates cellular sensitivity to ERα-mediated signaling during simulated energy insufficiency. The results also imply that estrogen promotes glucose and lactate uptake by these cells under those conditions. Evidence for correlation between hindbrain AMPK and hypothalamic nerve cell genomic activation provides novel proof for functional connectivity between this hindbrain sensor and higher order metabolic brain loci while demonstrating a modulatory role for estrogen in this interaction. Copyright © 2013 Wiley Periodicals, Inc.

Graphene wrapped porous Co_3O_4/NiCo_2O_4 double-shelled nanocages with enhanced electrocatalytic performance for glucose sensor

International Nuclear Information System (INIS)

Xue, Bei; Li, Kezhi; Feng, Lei; Lu, Jinhua; Zhang, Leilei

2017-01-01

Highlights: • Graphene wrapped Co_3O_4/NiCo_2O_4 DSNCs has been prepared for detection of glucose. • Sensing performance was improved by synergy between electrocatalytic activity and efficient electron transport. • The sensor has excellent sensing performance with high sensitivity and low detection limit. • The developed method was successfully applied to detect glucose in human serum. - Abstract: Graphene (G) wrapped porous Co_3O_4/NiCo_2O_4 double-shelled nanocages (Co_3O_4/NiCo_2O_4 DSNCs@G) were prepared by the formation of Co_3O_4/NiCo_2O_4 DSNCs using zeolite imidazole frameworks-67 as template with the subsequent calcination and package of G by hydrothermal method. The abundant accessible active sites provided by the porous structure of Co_3O_4/NiCo_2O_4 DSNCs and efficient electron transport pathways for electrocatalytic reaction offered by the high conductive G worked very well together in a ferocious synergy, which endowed Co_3O_4/NiCo_2O_4 DSNCs@G with excellent electrocatalytic behaviors for determining glucose. A comparison between Co_3O_4/NiCo_2O_4 DSNCs without G packing and Co_3O_4/NiCo_2O_4 DSNCs@G showed that former had linear response window concentrations of 0.01-3.52 mM (correlation coefficient = 0.999), detection limit of 0.744 μM (S/N = 3) and sensitivity of 0.196 mA mM"−"1 cm"−"2, whereas the latter exhibited linear response window concentrations of 0.01-3.52 mM (correlation coefficient = 0.999), detection limit of 0.384 μM (S/N = 3) and sensitivity of 0.304 mA mM"−"1 cm"−"2. The combination of Co_3O_4/NiCo_2O_4 DSNCs and G was a meaningful strategy to fabricate high-performance non-enzyme glucose sensors with low detection limit, good selectivity and high sensitivity.

The effect of gold nanoparticles modified electrode on the glucose sensing performance

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Zulkifli, Zulfa Aiza; Ridhuan, Nur Syafinaz; Nor, Noorhashimah Mohamad; Zakaria, Nor Dyana; Razak, Khairunisak Abdul

2017-07-01

In this work, 20 nm, 30 nm, 40 nm, 50 nm and 60 nm colloidal gold nanoparticles (AuNPs) were synthesized using the seeding growth method. AuNPs produced had spherical shape with uniform size. The AuNPs also are well dispersed in colloidal form that was proven by low polydispersity index. The produced AuNPs were used to modify electrode for glucose sensor. The produced AuNPs were deposited on indium tin oxide substrate (ITO), followed by immobilization of glucose oxidase (GOx) on it. After that, Nafion was deposited on the GOx/AuNPs/ITO. Electrooxidation of glucose with AuNPs-modified electrode was examined by cyclic voltammeter (CV) in 15 mM glucose mixed with 0.01 M PBS. The optimum size of AuNPs was 30 nm with optical density 3.0. AuNPs were successfully immobilized with glucose oxidase (GOx) and proved to work well as a glucose sensor. Based on the high electrocatalytic activity of Nafion/GOx/AuNPs/ITO, the sensitivity of the glucose sensors was further examined by varying the concentration of glucose solution from 2 mM to 20 mM in 0.01 M phosphate buffer solution (PBS) solution. Good linear relationship was observed between the catalytic current and glucose concentration in the range of 2 mM to 20 mM. The sensitivity of the Nafion/GOx/AuNPs/ITO electrode calculated from the slope of linear square calibration was 0.909 µA mM-1 cm-2 that is comparable with other published work. The linear fitting to the experimental data gives R-square of 0.991 at 0.9 V and a detection limit of 2.03 mM. This detection range is sufficient to be medically useful in monitoring human blood glucose level in which the normal blood glucose level is in the range of 4.4 to 6.6 mM and diabetic blood glucose level is above 7 mM.

Reduced Expression of the Liver/Beta-Cell Glucose Transporter Isoform in Glucose-Insensitive Pancreatic Beta Cells of Diabetic Rats

Science.gov (United States)

Thorens, Bernard; Weir, Gordon C.; Leahy, John L.; Lodish, Harvey F.; Bonner-Weir, Susan

1990-09-01

Rats injected with a single dose of streptozocin at 2 days of age develop non-insulin-dependent diabetes 6 weeks later. The pancreatic beta islet cells of these diabetic rats display a loss of glucose-induced insulin secretion while maintaining sensitivity to other secretagogues such as arginine. We analyzed the level of expression of the liver/beta-cell glucose transporter isoform in diabetic islets by immunofluorescence staining of pancreas sections and by Western blotting of islet lysates. Islets from diabetic animals have a reduced expression of this beta-cell-specific glucose transporter isoform and the extent of reduction is correlated with the severity of hyperglycemia. In contrast, expression of this transporter isoform in liver is minimally modified by the diabetes. Thus a decreased expression of the liver/beta-cell glucose transporter isoform in beta cells is associated with the impaired glucose sensing characteristic of diabetic islets; our data suggest that this glucose transporter may be part of the beta-cell glucose sensor.

Genetic disruption of SOD1 gene causes glucose intolerance and impairs β-cell function.

Science.gov (United States)

Muscogiuri, Giovanna; Salmon, Adam B; Aguayo-Mazzucato, Cristina; Li, Mengyao; Balas, Bogdan; Guardado-Mendoza, Rodolfo; Giaccari, Andrea; Reddick, Robert L; Reyna, Sara M; Weir, Gordon; Defronzo, Ralph A; Van Remmen, Holly; Musi, Nicolas

2013-12-01

Oxidative stress has been associated with insulin resistance and type 2 diabetes. However, it is not clear whether oxidative damage is a cause or a consequence of the metabolic abnormalities present in diabetic subjects. The goal of this study was to determine whether inducing oxidative damage through genetic ablation of superoxide dismutase 1 (SOD1) leads to abnormalities in glucose homeostasis. We studied SOD1-null mice and wild-type (WT) littermates. Glucose tolerance was evaluated with intraperitoneal glucose tolerance tests. Peripheral and hepatic insulin sensitivity was quantitated with the euglycemic-hyperinsulinemic clamp. β-Cell function was determined with the hyperglycemic clamp and morphometric analysis of pancreatic islets. Genetic ablation of SOD1 caused glucose intolerance, which was associated with reduced in vivo β-cell insulin secretion and decreased β-cell volume. Peripheral and hepatic insulin sensitivity were not significantly altered in SOD1-null mice. High-fat diet caused glucose intolerance in WT mice but did not further worsen the glucose intolerance observed in standard chow-fed SOD1-null mice. Our findings suggest that oxidative stress per se does not play a major role in the pathogenesis of insulin resistance and demonstrate that oxidative stress caused by SOD1 ablation leads to glucose intolerance secondary to β-cell dysfunction.

Effect of platinum-nanodendrite modification on the glucose-sensing properties of a zinc-oxide-nanorod electrode

Energy Technology Data Exchange (ETDEWEB)

Abdul Razak, Khairunisak, E-mail: khairunisak@usm.my [School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); NanoBiotechnology Research & Innovation (NanoBRI), INFORMM, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Neoh, Soo Huan; Ridhuan, N.S.; Mohamad Nor, Noorhashimah [School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia)

2016-09-01

Highlights: • Effect of PtNDs on ZnONRs/ITO glucose sensor was studied. • Well-defined PtNDs synthesis using 20 mM K{sub 2}PtCl{sub 4} produced good dispersion between nanodendrites with uniform particle size. • Nafion coating significantly improved the catalytic oxidation of glucose sensor. • Nafion/GO{sub x}/PtNDs/ZnONRs/ITO demonstrated better properties compared with Nafion/GO{sub x}/PtNDs/ITO and Nafion/GO{sub x}/ZnONRs/ITO electrodes. - Abstract: The properties of ZnO nanorods (ZnONRs) decorated with platinum nanodendrites (PtNDs) were studied. Various sizes of PtNDs were synthesized and spin coated onto ZnONRs, which were grown on indium–titanium–oxide (ITO) substrates through a low-temperature hydrothermal method. Scanning electron microscopy and X-ray diffraction analyses were conducted to analyze the morphology and structural properties of the electrodes. The effects of PtND size, glucose concentration, and Nafion amount on glucose-sensing properties were investigated. The glucose-sensing properties of electrodes with immobilized glucose oxidase (GO{sub x}) were measured using cyclic voltammetry. The bio-electrochemical properties of Nafion/GO{sub x}/42 nm PtNDs/ZnONRs/ITO glucose sensor was observed with linear range within 1–18 mM, with a sensitivity value of 5.85 μA/mM and a limit of detection of 1.56 mM. The results of this study indicate that PtNDs/ZnONRs/ITO has potential in glucose sensor applications.

Direct electron transfer of glucose oxidase and dual hydrogen peroxide and glucose detection based on water-dispersible carbon nanotubes derivative.

Science.gov (United States)

Chen, Hsiao-Chien; Tu, Yi-Ming; Hou, Chung-Che; Lin, Yu-Chen; Chen, Ching-Hsiang; Yang, Kuang-Hsuan

2015-03-31

A water-dispersible multi-walled carbon nanotubes (MWCNTs) derivative, MWCNTs-1-one-dihydroxypyridine (MWCNTs-Py) was synthesis via Friedel-Crafts chemical acylation. Raman spectra demonstrated the conjugated level of MWCNTs-Py was retained after this chemical modification. MWCNTs-Py showed dual hydrogen peroxide (H2O2) and glucose detections without mutual interference by adjusting pH value. It was sensitive to H2O2 in acidic solution and displayed the high performances of sensitivity, linear range, response time and stability; meanwhile it did not respond to H2O2 in neutral solution. In addition, this positively charged MWCNTs-Py could adsorb glucose oxidase (GOD) by electrostatic attraction. MWCNTs-Py-GOD/GC electrode showed the direct electron transfer (DET) of GOD with a pair of well-defined redox peaks, attesting the bioactivity of GOD was retained due to the non-destroyed immobilization. The high surface coverage of active GOD (3.5×10(-9) mol cm(-2)) resulted in exhibiting a good electrocatalytic activity toward glucose. This glucose sensor showed high sensitivity (68.1 μA mM(-1) cm(-2)) in a linear range from 3 μM to 7 mM in neutral buffer solution. The proposed sensor could distinguish H2O2 and glucose, thus owning high selectivity and reliability. Copyright © 2015. Published by Elsevier B.V.

Growth of coral-like PtAu-MnO2 binary nanocomposites on free-standing graphene paper for flexible nonenzymatic glucose sensors.

Science.gov (United States)

Xiao, Fei; Li, Yuanqing; Gao, Hongcai; Ge, Shuibing; Duan, Hongwei

2013-03-15

The growing demand for compact point-of-care medical devices and portable instruments for on-site environmental sampling has stimulated intense research on flexible sensors that can be miniaturized and function under considerable physical deformation. We report a new type of flexible electrochemical biosensors based on free-standing graphene paper carrying binary nanocomposites of PtAu alloy and MnO(2). The coral-like PtAu-MnO(2) nanocomposites are grown on the substrate through one-step template-free electrodeposition, leading to an intimate contact between the PtAu alloy and MnO(2) matrix. The flexible electrode exhibits a unique set of structural and electrochemical properties such as better uniformity, larger active surface areas, and faster electron transfer in comparison with the control electrode prepared by tandem growth of MnO(2) network and PtAu alloy in two steps. In nonenzymatic amperometric glucose detection, the PtAu-MnO(2) binary nanostructure-decorated graphene paper has shown greatly enhanced sensing performance such as wide liner range (0.1 mM to 30.0 mM), high sensitivity (58.54 μA cm(-2) mM(-1)), low detection limit (0.02 mM, S/N=3), satisfactory selectivity, excellent reproducibility and stability, and tolerability to mechanical stress. The strategy of co-growth of metal and metal oxides on freestanding carbon substrates opens new possibility to develop high-performance flexible electrochemical sensors. Copyright © 2012 Elsevier B.V. All rights reserved.

A Disposable Tear Glucose Biosensor—Part 2: System Integration and Model Validation

Science.gov (United States)

La Belle, Jeffrey T.; Bishop, Daniel K.; Vossler, Stephen R.; Patel, Dharmendra R.; Cook, Curtiss B.

2010-01-01

Background We presented a concept for a tear glucose sensor system in an article by Bishop and colleagues in this issue of Journal of Diabetes Science and Technology. A unique solution to collect tear fluid and measure glucose was developed. Individual components were selected, tested, and optimized, and system error modeling was performed. Further data on prototype testing are now provided. Methods An integrated fluidics portion of the prototype was designed, cast, and tested. A sensor was created using screen-printed sensors integrated with a silicone rubber fluidics system and absorbent polyurethane foam. A simulated eye surface was prepared using fluid-saturated poly(2-hydroxyethyl methacrylate) sheets, and the disposable prototype was tested for both reproducibility at 0, 200, and 400 μM glucose (n = 7) and dynamic range of glucose detection from 0 to 1000 μM glucose. Results From the replicated runs, an established relative standard deviation of 15.8% was calculated at 200 μM and a lower limit of detection was calculated at 43.4 μM. A linear dynamic range was demonstrated from 0 to 1000 μM with an R2 of 99.56%. The previously developed model predicted a 14.9% variation. This compares to the observed variance of 15.8% measured at 200 μM glucose. Conclusion With the newly designed fluidics component, an integrated tear glucose prototype was assembled and tested. Testing of this integrated prototype demonstrated a satisfactory lower limit of detection for measuring glucose concentration in tears and was reproducible across a physiological sampling range. The next step in the device design process will be initial animal studies to evaluate the current prototype for factors such as eye irritation, ease of use, and correlation with blood glucose. PMID:20307390

A disposable tear glucose biosensor-part 2: system integration and model validation.

Science.gov (United States)

La Belle, Jeffrey T; Bishop, Daniel K; Vossler, Stephen R; Patel, Dharmendra R; Cook, Curtiss B

2010-03-01

We presented a concept for a tear glucose sensor system in an article by Bishop and colleagues in this issue of Journal of Diabetes Science and Technology. A unique solution to collect tear fluid and measure glucose was developed. Individual components were selected, tested, and optimized, and system error modeling was performed. Further data on prototype testing are now provided. An integrated fluidics portion of the prototype was designed, cast, and tested. A sensor was created using screen-printed sensors integrated with a silicone rubber fluidics system and absorbent polyurethane foam. A simulated eye surface was prepared using fluid-saturated poly(2-hydroxyethyl methacrylate) sheets, and the disposable prototype was tested for both reproducibility at 0, 200, and 400 microM glucose (n = 7) and dynamic range of glucose detection from 0 to 1000 microM glucose. From the replicated runs, an established relative standard deviation of 15.8% was calculated at 200 microM and a lower limit of detection was calculated at 43.4 microM. A linear dynamic range was demonstrated from 0 to 1000 microM with an R(2) of 99.56%. The previously developed model predicted a 14.9% variation. This compares to the observed variance of 15.8% measured at 200 microM glucose. With the newly designed fluidics component, an integrated tear glucose prototype was assembled and tested. Testing of this integrated prototype demonstrated a satisfactory lower limit of detection for measuring glucose concentration in tears and was reproducible across a physiological sampling range. The next step in the device design process will be initial animal studies to evaluate the current prototype for factors such as eye irritation, ease of use, and correlation with blood glucose. (c) 2010 Diabetes Technology Society.

A novel electrochemical immunosensor using β-cyclodextrins functionalized silver supported adamantine-modified glucose oxidase as labels for ultrasensitive detection of alpha-fetoprotein.

Science.gov (United States)

Gao, Jian; Ma, Hongmin; Lv, Xiaohui; Yan, Tao; Li, Na; Cao, Wei; Wei, Qin

2015-09-17

In this work, a novel sandwich-type electrochemical immunosensor based on host-guest interaction was fabricated for the detection of alpha-fetoprotein (AFP). Due to the large specific surface area of multiwalled carbon nanotubes and the unique supramolecular recognition ability of β-cyclodextrins, ferrocenecarboxylic acid (Fc) was incorporated into this sensor platform by host-guest interaction to generate an electrochemical signal. And β-cyclodextrins functionalized silver supported adamantine-modified glucose oxidase (GOD-CD-Ag), was used as a label to improve the analytical performance of the immunosensor by the dual amplification strategy. The obtained GOD-CD-Ag conjugates could convert glucose into gluconic acid with the formation of hydrogen peroxide (H2O2). And then silver nanoparticles could in situ catalyze the reduction of the generated H2O2, dramatically improving the oxidation reaction of Fc. The developed immunosensor shows a wide linear calibration range from 0.001 to 5.0 ng/mL with a low detection limit (0.2 pg/mL) for the detection of AFP. The method, with ideal reproducibility and selectivity, has a wide application prospect in clinical research. Copyright © 2015 Elsevier B.V. All rights reserved.

Nonenzymatic amperometric determination of glucose by CuO nanocubes-graphene nanocomposite modified electrode.

Science.gov (United States)

Luo, Liqiang; Zhu, Limei; Wang, Zhenxin

2012-12-01

Here, we report a nonenzymatic amperometric glucose sensor based on copper oxide (CuO) nanocubes-graphene nanocomposite modified glassy carbon electrode (CuO-G-GCE). In this case, the graphene sheets were cast on the GCE directly. CuO nanocubes were obtained by oxidizing electrochemically deposited Cu on the graphene. The morphology of CuO-G nanocomposite was characterized by scanning electron microscopy. The CuO-G-GCE-based sensor exhibited excellent electrocatalytic activity and high stability for glucose oxidation. Under optimized conditions, the linearity between the current response and the glucose concentration was obtained in the range of 2μM to 4mM with a detection limit of 0.7μM (S/N=3), and a high sensitivity of 1360μAmM(-1)cm(-2). The proposed electrode showed a fast response time (less than 5s) and a good reproducibility. The as-made sensor was applied to determine the glucose levels in clinic human serum samples with satisfactory results. In addition, the effects of common interfering species, including ascorbic acid, uric acid, dopamine and other carbohydrates, on the amperometric response of the sensor were investigated and discussed in detail. Copyright © 2012 Elsevier B.V. All rights reserved.

High-performance glucose biosensor based on chitosan-glucose oxidase immobilized polypyrrole/Nafion/functionalized multi-walled carbon nanotubes bio-nanohybrid film.

Science.gov (United States)

Shrestha, Bishnu Kumar; Ahmad, Rafiq; Mousa, Hamouda M; Kim, In-Gi; Kim, Jeong In; Neupane, Madhav Prasad; Park, Chan Hee; Kim, Cheol Sang

2016-11-15

A highly electroactive bio-nanohybrid film of polypyrrole (PPy)-Nafion (Nf)-functionalized multi-walled carbon nanotubes (fMWCNTs) nanocomposite was prepared on the glassy carbon electrode (GCE) by a facile one-step electrochemical polymerization technique followed by chitosan-glucose oxidase (CH-GOx) immobilization on its surface to achieve a high-performance glucose biosensor. The as-fabricated nanohybrid composite provides high surface area for GOx immobilization and thus enhances the enzyme-loading efficiency. The structural characterization revealed that the PPy-Nf-fMWCNTs nanocomposite films were uniformly formed on GCE and after GOx immobilization, the surface porosities of the film were decreased due to enzyme encapsulation inside the bio-nanohybrid composite materials. The electrochemical behavior of the fabricated biosensor was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry measurements. The results indicated an excellent catalytic property of bio-nanohybrid film for glucose detection with improved sensitivity of 2860.3μAmM(-1)cm(-2), the linear range up to 4.7mM (R(2)=0.9992), and a low detection limit of 5μM under a signal/noise (S/N) ratio of 3. Furthermore, the resulting biosensor presented reliable selectivity, better long-term stability, good repeatability, reproducibility, and acceptable measurement of glucose concentration in real serum samples. Thus, this fabricated biosensor provides an efficient and highly sensitive platform for glucose sensing and can open up new avenues for clinical applications. Copyright © 2016 Elsevier Inc. All rights reserved.

Fluorescent sensors based on quinoline-containing styrylcyanine: determination of ferric ions, hydrogen peroxide, and glucose, pH-sensitive properties and bioimaging.

Science.gov (United States)

Yang, Xiaodong; Zhao, Peiliang; Qu, Jinqing; Liu, Ruiyuan

2015-08-01

A novel styrylcyanine-based fluorescent probe 1 was designed and synthesized via facile methods. Ferric ions quenched the fluorescence of probe 1, whereas the addition of ferrous ions led to only small changes in the fluorescence signal. When hydrogen peroxide was introduced into the solution containing probe 1 and Fe(2+) , Fe(2+) was oxidized to Fe(3+), resulting in the quenching of the fluorescence. The probe 1/Fe(2+) solution fluorescence could also be quenched by H2 O2 released from glucose oxidation by glucose oxidase (GOD), which means that probe 1/Fe(2+) platform could be used to detect glucose. Probe 1 is fluorescent in basic and neutral media but almost non-fluorescent in strong acidic environments. Such behaviour enables it to work as a fluorescent pH sensor in both the solution and solid states and as a chemosensor for detecting volatile organic compounds with high acidity and basicity. Subsequently, the fluorescence microscopic images of probe 1 in live cells and in zebrafish were achieved successfully, suggesting that the probe has good cell membrane permeability and a potential application for imaging in living cells and living organisms. Copyright © 2014 John Wiley & Sons, Ltd.

Holographic sensors for diagnostics of solution components

International Nuclear Information System (INIS)

Kraiskii, A V; Suitanov, T T; Postnikov, V A; Khamidulin, A V

2010-01-01

The properties of holographic sensors of two types are studied. The sensors are based on a three-dimensional polymer-network matrix of copolymers of acrylamide, acrylic acid (which are sensitive to the medium acidity and bivalent metal ions) and aminophenylboronic acid (sensitive to glucose). It is found that a change in the ionic composition of a solution results in changes in the distance between layers and in the diffraction efficiency of holograms. Variations in the shape of spectral lines, which are attributed to the inhomogeneity of a sensitive layer, and nonmonotonic changes in the emulsion thickness and diffraction efficiency were observed during transient processes. The composition of the components of a hydrogel medium is selected for systems which can be used as a base for glucose sensors with the mean holographic response in the region of physiological glucose concentration in model solutions achieving 40 nm/(mmol L -1 ). It is shown that the developed holographic sensors can be used for the visual and instrumental determination of the medium acidity, alcohol content, ionic strength, bivalent metal salts and the quality of water, in particular, for drinking. (laser applications and other topics in quantum electronics)

Surface analysis of gold nanoparticles functionalized with thiol-modified glucose SAMs for biosensor applications.

Directory of Open Access Journals (Sweden)

Valentina eSpampinato

2016-02-01

Full Text Available In this work, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS, Principal Component Analysis (PCA and X-ray Photoelectron Spectroscopy (XPS have been used to characterize the surface chemistry of gold substrates before and after functionalization with thiol-modified glucose self-assembled monolayers and subsequent biochemical specific recognition of maltose binding protein (MBP.The results indicate that the surface functionalization is achieved both on flat and nanoparticles gold substrates thus showing the potential of the developed system as biodetection platform. Moreover, the method presented here has been found to be a sound and valid approach to characterize the surface chemistry of nanoparticles functionalized with large molecules.Both techniques were proved to be very useful tools for monitoring all the functionalization steps, including the investigation of the biological behaviour of the glucose-modified particles in presence of the maltose binding protein.

Changes in enzyme activity and functional diversity in soil induced by Cd and glucose addition

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Gilmullina, A. R.; Galitskaya, P. Yu; Selivanovskaya, S. Yu

2018-01-01

Toxic heavy metal (HM) contamination is a major global issue as it may have an indirect effect on the health of soil, plants, animals and, consequently, on human health. Agricultural soils’ fertilization is one of the reported sources of HM pollution in the world. In this case simultaneous input of stimulating and inhibiting agents into soil takes place, and effects of the combined influence of these agents is hardly predictable. In this study, a simultaneous inhibiting and stimulating effect of Cd and glucose on soil microbes was studied in a model experiment. Enzyme activities (phosphatase, β-glucosidase and cellobiohydrolase) and functional diversity (BIOLOG®EcoPlates ™) were assessed as a test functions. Cd (300 μg Cd g-1 ) amendment had a negative effect only on phosphatase activity. Glucose (3 mg C g-1) addition inhibited β-glucosidase activity and stimulated functional diversity. In joint addition of Cd and Glucose the leading effect belonged to that agent which had the greatest effect in case when it was added separately.

Cost-Effectiveness of Sensor-Augmented Pump Therapy with Low Glucose Suspend Versus Standard Insulin Pump Therapy in Two Different Patient Populations with Type 1 Diabetes in France.

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Roze, Stéphane; Smith-Palmer, Jayne; Valentine, William; Payet, Vincent; de Portu, Simona; Papo, Natalie; Cucherat, Michel; Hanaire, Helene

2016-02-01

Sensor-augmented pump therapy (SAP) provides a useful adjunct relative to continuous subcutaneous insulin infusion (CSII) alone. It can provide early warning of the onset of hyperglycemia and hypoglycemia and has the functionality to suspend insulin delivery if sensor glucose levels fall below a predefined threshold. The aim was to assess the cost-effectiveness of SAP with low glucose suspend (LGS) versus CSII alone in type 1 diabetes. Cost-effectiveness analysis was performed using the CORE Diabetes Model, using published clinical input data. The analysis was performed in two cohorts: one with uncontrolled glycated hemoglobin at baseline and one at elevated risk for hypoglycemic events. The analysis was conducted from a healthcare payer perspective over a lifetime time horizon; future costs and clinical outcomes were discounted at 4% per annum. In patients with uncontrolled glycated hemoglobin at baseline, SAP + LGS resulted in improved discounted quality-adjusted life expectancy (QALE) versus CSII (10.55 quality-adjusted life-years [QALYs] vs. 9.36 QALYs) but higher mean lifetime direct costs (€84,972 vs. €49,171) resulting in an incremental cost-effectiveness ratio (ICER) of €30,163 per QALY gained. In patients at elevated risk for hypoglycemia, the ICER was €22,005 per QALY gained for SAP + LGS versus CSII as lifetime costs were higher (€88,680 vs. €57,097), but QALE was also higher (18.46 QALYs vs. 18.30 QALYs). In France, projected improvements in outcomes with SAP + LGS versus CSII translated into an ICER generally considered as good value for money, particularly in patients who experience frequent and/or problematic hypoglycemic events.

Glucose sensing by carotid body glomus cells: potential implications in disease

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Lin eGao

2014-10-01

Full Text Available The carotid body (CB is a key chemoreceptor organ in which glomus cells sense changes in blood O2, CO2, and pH levels. CB glomus cells have also been found to detect hypoglycemia in both non-primate mammals and humans. O2 and low-glucose responses share a common final pathway involving membrane depolarization, extracellular calcium influx, increase in cytosolic calcium concentration, and neurotransmitter secretion, which stimulates afferent sensory fibers to evoke sympathoadrenal activation. On the other hand, hypoxia and low glucose induce separate signal transduction pathways. Unlike O2 sensing, the response of the CB to low glucose is not altered by rotenone, with the low glucose-activated background cationic current unaffected by hypoxia. Responses of the CB to hypoglycemia and hypoxia can be potentiated by each other. The counter-regulatory response to hypoglycemia by the CB is essential for the brain, an organ that is particularly sensitive to low glucose. CB glucose sensing could be altered in diabetic patients, particularly those under insulin treatment, as well as in other medical conditions such as sleep apnea or obstructive pulmonary diseases, where chronic hypoxemia presents with plastic modifications in CB structure and function. The current review will focus on the following main aspects: 1 the CB as a low glucose sensor in both in vitro and in vivo models; 2 molecular and ionic mechanisms of low glucose sensing by glomus cells, 3 the interplay between low glucose and O2 sensing in CB, and 4 the role of CB low glucose sensing in the pathophysiology of cardiorespiratory and metabolic diseases, and how this may serve as a potential therapeutic target.

Expanding the functionality and applications of nanopore sensors

Science.gov (United States)

Venta, Kimberly E.

Nanopore sensors have developed into powerful tools for single-molecule studies since their inception two decades ago. Nanopore sensors function as nanoscale Coulter counters, by monitoring ionic current modulations as particles pass through a nanopore. While nanopore sensors can be used to study any nanoscale particle, their most notable application is as a low cost, fast alternative to current DNA sequencing technologies. In recent years, signifcant progress has been made toward the goal of nanopore-based DNA sequencing, which requires an ambitious combination of a low-noise and high-bandwidth nanopore measurement system and spatial resolution. In this dissertation, nanopore sensors in thin membranes are developed to improve dimensional resolution, and these membranes are used in parallel with a high-bandwidth amplfier. Using this nanopore sensor system, the signals of three DNA homopolymers are differentiated for the first time in solid-state nanopores. The nanopore noise is also reduced through the addition of a layer of SU8, a spin-on polymer, to the supporting chip structure. By increasing the temporal and spatial resolution of nanopore sensors, studies of shorter molecules are now possible. Nanopore sensors are beginning to be used for the study and characterization of nanoparticles. Nanoparticles have found many uses from biomedical imaging to next-generation solar cells. However, further insights into the formation and characterization of nanoparticles would aid in developing improved synthesis methods leading to more effective and customizable nanoparticles. This dissertation presents two methods of employing nanopore sensors to benet nanoparticle characterization and fabrication. Nanopores were used to study the formation of individual nanoparticles and serve as nanoparticle growth templates that could be exploited to create custom nanoparticle arrays. Additionally, nanopore sensors were used to characterize the surface charge density of anisotropic

Combining functional CT and FDG PET allows the calculation of FDG extraction fraction and hepatic glucose phosphorylation

Energy Technology Data Exchange (ETDEWEB)

Griffiths, M R [Centre for Medical and Health Physics, Queensland University of Technology (Australia); Wesley Research Institute, QLD (Australia); Miles, K A [Centre for Medical and Health Physics, Queensland University of Technology (Australia); Wesley Research Institute, QLD (Australia); Southern X-ray Clinics, Brisbane [Australia; Keith, C J [Wesley Research Institute, QLD (Australia)

2002-09-01

Perfusion data from Functional CT and FDG-PET data may be combined to provide additional information about the uptake of FDG. We have developed methods to calculate FDG extraction fraction in tissues and to quantify hepatic glucose phosphorylation in the liver. Extraction fraction: Functional CT and FDG-PET studies were used to obtain measurements of perfusion and glucose uptake respectively within ten pulmonary nodules. The net influx constant (Ki) was determined from SUV measurements for each lung mass Extraction fraction (E) for each mass lesion was determined from: E=Ki/(Px[1-Hct]). A pixel by pixel calculation allowed generation of extraction fraction maps. The extraction fraction measurements ranged (median) from 0.6% to 4.81% (2.7%). The values for a benign nodule and an organising pneumonia were 0.6% and 0.71% respectively. Extraction fraction measurements for the malignant nodules ranged from 2.01% to 4.81%. A clearer separation of benign and malignant lesions is seen with E values rather than with SUV. Hepatic Glucose Phosphorylation: Functional CT and FDG-PET were utilised to obtain measurements of perfusion and glucose uptake respectively within the livers of a series of 35 patients with colorectal cancer. Hepatic perfusion and the net influx constant were incorporated into FDG kinetic analysis to determine hepatic glucose phosphorylation fraction. SUV and Ki were significantly lower in the 12 patients with advanced disease (p=0.015 and p=0.013 respectively) whereas portal and total hepatic perfusion were increased (p=0.013 and p=0.008 respectively). Combining the PET and CT data yielded phosphorylation fractions of 1.14% and 0.74% for early and advanced disease respectively (p=0.002). By combining functional CT measurements of blood flow with PET measurements of FDG uptake, it is possible to calculate the extraction fraction of FDG and Hepatic glucose phosphorylation. The use of the extraction fraction has improved the distinction between malignant and

Combining functional CT and FDG PET allows the calculation of FDG extraction fraction and hepatic glucose phosphorylation

International Nuclear Information System (INIS)

Griffiths, M.R.; Miles, K.A.; Keith, C.J.

2002-01-01

Perfusion data from Functional CT and FDG-PET data may be combined to provide additional information about the uptake of FDG. We have developed methods to calculate FDG extraction fraction in tissues and to quantify hepatic glucose phosphorylation in the liver. Extraction fraction: Functional CT and FDG-PET studies were used to obtain measurements of perfusion and glucose uptake respectively within ten pulmonary nodules. The net influx constant (Ki) was determined from SUV measurements for each lung mass Extraction fraction (E) for each mass lesion was determined from: E=Ki/(Px[1-Hct]). A pixel by pixel calculation allowed generation of extraction fraction maps. The extraction fraction measurements ranged (median) from 0.6% to 4.81% (2.7%). The values for a benign nodule and an organising pneumonia were 0.6% and 0.71% respectively. Extraction fraction measurements for the malignant nodules ranged from 2.01% to 4.81%. A clearer separation of benign and malignant lesions is seen with E values rather than with SUV. Hepatic Glucose Phosphorylation: Functional CT and FDG-PET were utilised to obtain measurements of perfusion and glucose uptake respectively within the livers of a series of 35 patients with colorectal cancer. Hepatic perfusion and the net influx constant were incorporated into FDG kinetic analysis to determine hepatic glucose phosphorylation fraction. SUV and Ki were significantly lower in the 12 patients with advanced disease (p=0.015 and p=0.013 respectively) whereas portal and total hepatic perfusion were increased (p=0.013 and p=0.008 respectively). Combining the PET and CT data yielded phosphorylation fractions of 1.14% and 0.74% for early and advanced disease respectively (p=0.002). By combining functional CT measurements of blood flow with PET measurements of FDG uptake, it is possible to calculate the extraction fraction of FDG and Hepatic glucose phosphorylation. The use of the extraction fraction has improved the distinction between malignant and

Zinc oxide nano-rods based glucose biosensor devices fabrication

Science.gov (United States)

Wahab, H. A.; Salama, A. A.; El Saeid, A. A.; Willander, M.; Nur, O.; Battisha, I. K.

2018-06-01

ZnO is distinguished multifunctional material that has wide applications in biochemical sensor devices. For extracellular measurements, Zinc oxide nano-rods will be deposited on conducting plastic substrate with annealing temperature 150 °C (ZNRP150) and silver wire with annealing temperature 250 °C (ZNRW250), for the extracellular glucose concentration determination with functionalized ZNR-coated biosensors. It was performed in phosphate buffer saline (PBS) over the range from 1 μM to 10 mM and on human blood plasma. The prepared samples crystal structure and surface morphologies were characterized by XRD and field emission scanning electron microscope FESEM respectively.

A reagentless enzymatic fluorescent biosensor for glucose based on upconverting glasses, as excitation source, and chemically modified glucose oxidase.

Science.gov (United States)

Del Barrio, Melisa; Cases, Rafael; Cebolla, Vicente; Hirsch, Thomas; de Marcos, Susana; Wilhelm, Stefan; Galbán, Javier

2016-11-01

Upon near-infrared excitation Tm(3+)+Yb(3+) doped fluorohafnate glasses present upconversion properties and emit visible light. This property permits to use these glasses (UCG) as excitation sources for fluorescent optical biosensors. Taking this into account, in this work a fluorescent biosensor for glucose determination is designed and evaluated. The biosensor combines the UCG and the fluorescence of the enzyme glucose oxidase chemically modified with a fluorescein derivative (GOx-FS), whose intensity is modified during the enzymatic reaction with glucose. Optical parameters have been optimized and a mathematical model describing the behavior of the analytical signal is suggested. Working in FIA mode, the biosensor responds to glucose concentrations up to, at least, 15mM with a limit of detection of 1.9mM. The biosensor has a minimum lifetime of 9 days and has been applied to glucose determination in drinks. The applicability of the sensor was tested by glucose determination in two fruit juices. Copyright © 2016 Elsevier B.V. All rights reserved.

Functionalized graphene/silicon chemi-diode H₂ sensor with tunable sensitivity.

Science.gov (United States)

Uddin, Md Ahsan; Singh, Amol Kumar; Sudarshan, Tangali S; Koley, Goutam

2014-03-28

A reverse bias tunable Pd- and Pt-functionalized graphene/Si heterostructure Schottky diode H2 sensor has been demonstrated. Compared to the graphene chemiresistor sensor, the chemi-diode sensor offers more than one order of magnitude higher sensitivity as the molecular adsorption induced Schottky barrier height change causes the heterojunction current to vary exponentially in reverse bias. The reverse bias operation also enables low power consumption, as well as modulation of the atomically thin graphene's Fermi level, leading to tunable sensitivity and detection of H₂ down to the sub-ppm range.

High Glucose Aggravates the Detrimental Effects of Pancreatic Stellate Cells on Beta-Cell Function

Directory of Open Access Journals (Sweden)

Min Zha

2014-01-01

Full Text Available Background and Aims. We here assess the effects of PSCs on β-cell function and apoptosis in vivo and in vitro. Materials and Methods. PSCs were transplanted into Wistar and Goto-Kakizaki (GK rats. Sixteen weeks after transplantation, β-cell function, apoptosis, and islet fibrosis were assessed. In vitro the effects of PSCs conditioned medium (PSCs-CM and/or high concentration of glucose on INS-1 cell function was assessed by measuring insulin secretion, INS-1 cell survival, apoptosis, and endoplasmic reticulum stress (ER stress associated CHOP expression. Results. PSCs transplantation exacerbated the impaired β-cell function in GK rats, but had no significant effects in Wistar rats. In vitro, PSCs-CM caused impaired INS-1 cell viability and insulin secretion and increased apoptosis, which were more pronounced in the presence of high glucose. Conclusion. Our study demonstrates that PSCs induce β-cell failure in vitro and in vivo.

The resilient hybrid fiber sensor network with self-healing function

Energy Technology Data Exchange (ETDEWEB)

Xu, Shibo, E-mail: Shibo-Xu@tju.edu.cn; Liu, Tiegen; Ge, Chunfeng; Chen, Qinnan; Zhang, Hongxia [College of Precision Instrument and Opto-electronics Engineering, Tianjin University, Tianjin 300072 (China); Key Laboratory of Opto-electronics Information Technology (Tianjin University), Ministry of Education, Tianjin 300072 (China)

2015-03-15

This paper presents a novel resilient fiber sensor network (FSN) with multi-ring architecture, which could interconnect various kinds of fiber sensors responsible for more than one measurands. We explain how the intelligent control system provides sensors with self-healing function meanwhile sensors are working properly, besides each fiber in FSN is under real-time monitoring. We explain the software process and emergency mechanism to respond failures or other circumstances. To improve the efficiency in the use of limited spectrum resources in some situations, we have two different structures to distribute the light sources rationally. Then, we propose a hybrid sensor working in FSN which is a combination of a distributed sensor and a FBG (Fiber Bragg Grating) array fused in a common fiber sensing temperature and vibrations simultaneously with neglectable crosstalk to each other. By making a failure to a working fiber in experiment, the feasibility and effectiveness of the network with a hybrid sensor has been demonstrated, hybrid sensors could not only work as designed but also survive from destructive failures with the help of resilient network and smart and quick self-healing actions. The network has improved the viability of the fiber sensors and diversity of measurands.

The resilient hybrid fiber sensor network with self-healing function

Science.gov (United States)

Xu, Shibo; Liu, Tiegen; Ge, Chunfeng; Chen, Qinnan; Zhang, Hongxia

2015-03-01

This paper presents a novel resilient fiber sensor network (FSN) with multi-ring architecture, which could interconnect various kinds of fiber sensors responsible for more than one measurands. We explain how the intelligent control system provides sensors with self-healing function meanwhile sensors are working properly, besides each fiber in FSN is under real-time monitoring. We explain the software process and emergency mechanism to respond failures or other circumstances. To improve the efficiency in the use of limited spectrum resources in some situations, we have two different structures to distribute the light sources rationally. Then, we propose a hybrid sensor working in FSN which is a combination of a distributed sensor and a FBG (Fiber Bragg Grating) array fused in a common fiber sensing temperature and vibrations simultaneously with neglectable crosstalk to each other. By making a failure to a working fiber in experiment, the feasibility and effectiveness of the network with a hybrid sensor has been demonstrated, hybrid sensors could not only work as designed but also survive from destructive failures with the help of resilient network and smart and quick self-healing actions. The network has improved the viability of the fiber sensors and diversity of measurands.

The resilient hybrid fiber sensor network with self-healing function

International Nuclear Information System (INIS)

Xu, Shibo; Liu, Tiegen; Ge, Chunfeng; Chen, Qinnan; Zhang, Hongxia

2015-01-01

This paper presents a novel resilient fiber sensor network (FSN) with multi-ring architecture, which could interconnect various kinds of fiber sensors responsible for more than one measurands. We explain how the intelligent control system provides sensors with self-healing function meanwhile sensors are working properly, besides each fiber in FSN is under real-time monitoring. We explain the software process and emergency mechanism to respond failures or other circumstances. To improve the efficiency in the use of limited spectrum resources in some situations, we have two different structures to distribute the light sources rationally. Then, we propose a hybrid sensor working in FSN which is a combination of a distributed sensor and a FBG (Fiber Bragg Grating) array fused in a common fiber sensing temperature and vibrations simultaneously with neglectable crosstalk to each other. By making a failure to a working fiber in experiment, the feasibility and effectiveness of the network with a hybrid sensor has been demonstrated, hybrid sensors could not only work as designed but also survive from destructive failures with the help of resilient network and smart and quick self-healing actions. The network has improved the viability of the fiber sensors and diversity of measurands

Activation of Wnt Signaling in Cortical Neurons Enhances Glucose Utilization through Glycolysis.

Science.gov (United States)

Cisternas, Pedro; Salazar, Paulina; Silva-Álvarez, Carmen; Barros, L Felipe; Inestrosa, Nibaldo C

2016-12-09

The Wnt signaling pathway is critical for a number of functions in the central nervous system, including regulation of the synaptic cleft structure and neuroprotection against injury. Deregulation of Wnt signaling has been associated with several brain pathologies, including Alzheimer's disease. In recent years, it has been suggested that the Wnt pathway might act as a central integrator of metabolic signals from peripheral organs to the brain, which would represent a new role for Wnt signaling in cell metabolism. Energy metabolism is critical for normal neuronal function, which mainly depends on glucose utilization. Brain energy metabolism is important in almost all neurological disorders, to which a decrease in the capacity of the brain to utilize glucose has been linked. However, little is known about the relationship between Wnt signaling and neuronal glucose metabolism in the cellular context. In the present study, we found that acute treatment with the Wnt3a ligand induced a large increase in glucose uptake, without changes in the expression or localization of glucose transporter type 3. In addition, we observed that Wnt3a treatment increased the activation of the metabolic sensor Akt. Moreover, we observed an increase in the activity of hexokinase and in the glycolytic rate, and both processes were dependent on activation of the Akt pathway. Furthermore, we did not observe changes in the activity of glucose-6-phosphate dehydrogenase or in the pentose phosphate pathway. The effect of Wnt3a was independent of both the transcription of Wnt target genes and synaptic effects of Wnt3a. Together, our results suggest that Wnt signaling stimulates glucose utilization in cortical neurons through glycolysis to satisfy the high energy demand of these cells. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Fluorescent blood glucose monitor by hemin-functionalized graphene quantum dots based sensing system

Energy Technology Data Exchange (ETDEWEB)

He, Yuezhen; Wang, Xiaoxun; Sun, Jian; Jiao, Shoufeng; Chen, Hongqi; Gao, Feng; Wang, Lun, E-mail: wanglun@mail.ahnu.edu.cn

2014-01-31

Graphical abstract: -- Highlights: •Hemin is assembled onto the surfaces of graphene quantum dots (GQDs). •With the aid of hemin, H{sub 2}O{sub 2} could quench the FL signal of GQDs obviously. •Based on this effect, a fluorescent platform is proposed for the sensing of glucose. •The proposed method provides a new pathway to explore practical application of GQDs. -- Abstract: In the present work, a highly sensitive and specific fluorescent biosensor for blood glucose monitoring is developed based on hemin-functionalized graphene quantum dots (GQDs) and glucose oxidase (GOx) system. The GQDs which are simply prepared by pyrolyzing citric acid exhibit strong fluorescence and good water-solubility. Due to the noncovalent assembly between hemin and GQDs, the addition of hemin can make hydrogen peroxide (H{sub 2}O{sub 2}) to destroy the passivated surface of GQDs, leading to significant fluorescence quenching of GQDs. Based on this effect, a novel fluorescent platform is proposed for the sensing of glucose. Under the optimized conditions, the linear range of glucose is from 9 to 300 μM, and the limit of detection is 0.1 μM. As unique properties of GQDs, the proposed biosensor is green, simple, cost-efficient, and it is successfully applied to the determination of glucose in human serum. In addition, the proposed method provides a new pathway to further design the biosensors based on the assembly of GQDs with hemin for detection of biomolecules.

Facile synthesis of glucose-functionalized reduced graphene oxide (GFRGO)/poly(vinyl alcohol) nanocomposites for improving thermal and mechanical properties

Energy Technology Data Exchange (ETDEWEB)

Abdolmaleki, Amir, E-mail: abdolmaleki@cc.iut.ac.ir [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Center of Excellence in Sensors and Green Chemistry, Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Mallakpour, Shadpour, E-mail: mallak@cc.iut.ac.ir [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Center of Excellence in Sensors and Green Chemistry, Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Karshenas, Azam [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

2017-03-15

Highlights: • GFRGO composites were synthesized and used for fabrication of PVA/GFRGO NCs. • Attached glucose on RGO enhances RGO interaction with PVA hydroxyl groups. • PVA/GFRGO NCs exhibited enhanced thermal and mechanical properties. • FE-SEM and TEM micrographs prove good dispersion of GFRGO into PVA matrix. - Abstract: In this work, we provided a facile pathway to the modification of reduced graphene oxide (RGO) nanosheets by glucose as a biologically active molecule through covalent functionalization. Then, flexible and smooth poly(vinyl alcohol) (PVA)/glucose-functionalized reduced graphene oxide (PVA/GFRGO) nanocomposite (NC) films were fabricated using 0, 1, 3 and 5 wt% concentrations of RGO-glucose in water. As a reducing sugar, glucose can reduce graphene oxide. Thus, graphene oxide was converted to reduced graphene oxide (RGO) by hydrazine hydrate. Then, RGO was functionalized with glucose to achieve good dispersion in the polymer matrix. Due to the increased interfacial interaction between GFRGO and PVA matrix, the prepared PVA/GFRGO NCs showed a 52% increase in tensile strength and a 47% improvement in Young’s modulus by adding of only 5 wt% of GFRGO. Thermal analysis results showed that the thermal stability of the PVA/GFRGO NCs increased compared to the neat PVA film.

Facile synthesis of glucose-functionalized reduced graphene oxide (GFRGO)/poly(vinyl alcohol) nanocomposites for improving thermal and mechanical properties

International Nuclear Information System (INIS)

Abdolmaleki, Amir; Mallakpour, Shadpour; Karshenas, Azam

2017-01-01

Highlights: • GFRGO composites were synthesized and used for fabrication of PVA/GFRGO NCs. • Attached glucose on RGO enhances RGO interaction with PVA hydroxyl groups. • PVA/GFRGO NCs exhibited enhanced thermal and mechanical properties. • FE-SEM and TEM micrographs prove good dispersion of GFRGO into PVA matrix. - Abstract: In this work, we provided a facile pathway to the modification of reduced graphene oxide (RGO) nanosheets by glucose as a biologically active molecule through covalent functionalization. Then, flexible and smooth poly(vinyl alcohol) (PVA)/glucose-functionalized reduced graphene oxide (PVA/GFRGO) nanocomposite (NC) films were fabricated using 0, 1, 3 and 5 wt% concentrations of RGO-glucose in water. As a reducing sugar, glucose can reduce graphene oxide. Thus, graphene oxide was converted to reduced graphene oxide (RGO) by hydrazine hydrate. Then, RGO was functionalized with glucose to achieve good dispersion in the polymer matrix. Due to the increased interfacial interaction between GFRGO and PVA matrix, the prepared PVA/GFRGO NCs showed a 52% increase in tensile strength and a 47% improvement in Young’s modulus by adding of only 5 wt% of GFRGO. Thermal analysis results showed that the thermal stability of the PVA/GFRGO NCs increased compared to the neat PVA film.

The effect of metformin on monocyte secretory function in simvastatin-treated patients with impaired fasting glucose.

Science.gov (United States)

Krysiak, Robert; Okopien, Bogusław

2013-01-01

This study was designed to investigate whether metformin affects monocyte secretory function in patients with impaired fasting glucose receiving chronic statin therapy. The study included 48 patients with impaired fasting glucose treated for at least three months with simvastatin (40 mg daily). These patients were randomized to either metformin (3 g daily) or placebo, which was administered together with simvastatin for 90 days. Plasma lipids, glucose homeostasis markers, monocyte cytokine release and plasma C-reactive protein levels were determined before randomization and at the end of the treatment. Compared to placebo, metformin reduced monocyte release of tumor necrosis factor-α, interleukin-1β, interleukin-6, monocyte chemoattractant protein-1 and interleukin-8, as well as decreased plasma C-reactive protein levels, which were accompanied by an improvement in insulin sensitivity. The obtained results suggest that metformin may inhibit monocyte secretory function and reduce systemic inflammation in statin-treated patients with prediabetes. Impaired fasting glucose patients with high cardiovascular risk may receive the greatest benefits from concomitant treatment with a statin and metformin. Copyright © 2013 Elsevier Inc. All rights reserved.

Glucose sensing by GABAergic neurons in the mouse nucleus tractus solitarii

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Boychuk, Carie R.; Gyarmati, Peter; Xu, Hong

2015-01-01

Changes in blood glucose concentration alter autonomic function in a manner consistent with altered neural activity in brain regions controlling digestive processes, including neurons in the brain stem nucleus tractus solitarii (NTS), which process viscerosensory information. With whole cell or on-cell patch-clamp recordings, responses to elevating glucose concentration from 2.5 to 15 mM were assessed in identified GABAergic NTS neurons in slices from transgenic mice that express EGFP in a subset of GABA neurons. Single-cell real-time RT-PCR was also performed to detect glutamic acid decarboxylase (GAD67) in recorded neurons. In most identified GABA neurons (73%), elevating glucose concentration from 2.5 to 15 mM resulted in either increased (40%) or decreased (33%) neuronal excitability, reflected by altered membrane potential and/or action potential firing. Effects on membrane potential were maintained when action potentials or fast synaptic inputs were blocked, suggesting direct glucose sensing by GABA neurons. Glucose-inhibited GABA neurons were found predominantly in the lateral NTS, whereas glucose-excited cells were mainly in the medial NTS, suggesting regional segregation of responses. Responses were prevented in the presence of glucosamine, a glucokinase (GCK) inhibitor. Depolarizing responses were prevented when KATP channel activity was blocked with tolbutamide. Whereas effects on synaptic input to identified GABAergic neurons were variable in GABA neurons, elevating glucose increased glutamate release subsequent to stimulation of tractus solitarius in unlabeled, unidentified neurons. These results indicate that GABAergic NTS neurons act as GCK-dependent glucose sensors in the vagal complex, providing a means of modulating central autonomic signals when glucose is elevated. PMID:26084907

Selective chloroform sensor using thiol functionalized reduced graphene oxide at room temperature

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Midya, Anupam; Mukherjee, Subhrajit; Roy, Shreyasee; Santra, Sumita; Manna, Nilotpal; Ray, Samit K.

2018-02-01

This paper presents a highly selective chloroform sensor using functionalised reduced graphene oxide (RGO) as a sensing layer. Thiol group is covalently attached on the basal plan of RGO film by a simple one-step aryl diazonium chemistry to improve its selectivity. Several spectroscopic techniques like X-ray photoelectron, Raman and Fourier transform infrared spectroscopy confirm successful thiol functionalization of RGO. Finally, the fabricated chemiresistor type sensor is exposed to chloroform in the concentration range 200-800 ppm (parts per million). The sensor shows a 4.3% of response towards 800 ppm chloroform. The selectivity of the sensor is analyzed using various volatile organic compounds as well. The devices show enhanced response and faster recovery attributed to the physiosorption of chloroform onto thiol functionalized graphene making them attractive for 2D materials based sensing applications.

A ``plasmonic cuvette'': dye chemistry coupled to plasmonic interferometry for glucose sensing

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Siu, Vince S.; Feng, Jing; Flanigan, Patrick W.; Palmore, G. Tayhas R.; Pacifici, Domenico

2014-06-01

A non-invasive method for the detection of glucose is sought by millions of diabetic patients to improve personal management of blood glucose over a lifetime. In this work, the synergistic advantage of combining plasmonic interferometry with an enzyme-driven dye assay yields an optical sensor capable of detecting glucose in saliva with high sensitivity and selectivity. The sensor, coined a "plasmonic cuvette," is built around a nano-scale groove-slit-groove (GSG) plasmonic interferometer coupled to an Amplex-red/Glucose-oxidase/Glucose (AR/GOx/Glucose) assay. The proposed device is highly sensitive, with a measured intensity change of 1.7×105%/m (i.e., one order of magnitude more sensitive than without assay) and highly specific for glucose sensing in picoliter volumes, across the physiological range of glucose concentrations found in human saliva (20-240 μm). Real-time glucose monitoring in saliva is achieved by performing a detailed study of the underlying enzyme-driven reactions to determine and tune the effective rate constants in order to reduce the overall assay reaction time to ˜2 min. The results reported suggest that by opportunely choosing the appropriate dye chemistry, a plasmonic cuvette can be turned into a general, real-time sensing scheme for detection of any molecular target, with high sensitivity and selectivity, within extremely low volumes of biological fluid (down to femtoliters). Hereby, we present the results on glucose detection in artificial saliva as a notable and clinically relevant case study.

Design of a sensor network system with a self-maintenance function for homeland security applications

International Nuclear Information System (INIS)

Fujiwara, Takeshi; Takahashi, Hiroyuki; Iyomoto, Naoko

2008-01-01

In this study, we develop a new concept of a robust wireless sensor network for homeland security applications. The sensor system consists of intelligent radiation sensors that can communicate each other through the wireless network. This structure can cover a wide area with a flexible geometry which is suitable for detecting a moving object with a detectable radiation source. Also, it has a tolerance against both the partial node's failure and packet errors; realized by a Self-Maintenance function. The Self-maintenance function is a function that enables an artifact to find, diagnosis and fix the trouble automatically and maintain itself. So far some approaches have been tried to realize robust monitoring system by applying the idea of multiplex system, based on ''2 out of 3'', but this requires a large amount of the hardware and is not suitable for sensor network systems. We designed a sensor network system with Self-Maintenance function based on qualitative reasoning technique for robust wireless sensor network system, and an instrument network based on ZigBee has been set up for investigations. CsI(Tl) gamma-ray detectors are used as sensors. The network system picks up correlation signals from sensors even some of sensors send false signals, which can be used as a reliable detection system for practical use. (author)

Resonator graphene microfluidic antenna (RGMA) for blood glucose detection

Science.gov (United States)

Jizat, Noorlindawaty Md.; Mohamad, Su Natasha; Ishak, Muhammad Ikman

2017-09-01

Graphene is capable of highly sensitive analyte detection due to its nanoscale nature. Here we show a resonator graphene microfluidic antenna (RGMA) is used to detect the dielectric properties of aqueous glucose solution which represent the glucose level in blood. Simulation verified the high sensitivity of proposed RGMA made with aqueous glucose solutions at different concentrations. The RGMA yielded a sensor sensitivity of 0.1882GHz/mgml-1 as plotted from the slope of the linear fit from the result averages in S11 and S21 parameter, respectively. This results indicate that the proposed resonator antenna achieves high sensitivity and linear to the changes of glucose concentration.

Basal Forebrain Cholinergic Deficits Reduce Glucose Metabolism and Function of Cholinergic and GABAergic Systems in the Cingulate Cortex.

Science.gov (United States)

Jeong, Da Un; Oh, Jin Hwan; Lee, Ji Eun; Lee, Jihyeon; Cho, Zang Hee; Chang, Jin Woo; Chang, Won Seok

2016-01-01

Reduced brain glucose metabolism and basal forebrain cholinergic neuron degeneration are common features of Alzheimer's disease and have been correlated with memory function. Although regions representing glucose hypometabolism in patients with Alzheimer's disease are targets of cholinergic basal forebrain neurons, the interaction between cholinergic denervation and glucose hypometabolism is still unclear. The aim of the present study was to evaluate glucose metabolism changes caused by cholinergic deficits. We lesioned basal forebrain cholinergic neurons in rats using 192 immunoglobulin G-saporin. After 3 weeks, lesioned animals underwent water maze testing or were analyzed by ¹⁸F-2-fluoro-2-deoxyglucose positron emission tomography. During water maze probe testing, performance of the lesioned group decreased with respect to time spent in the target quadrant and platform zone. Cingulate cortex glucose metabolism in the lesioned group decreased, compared with the normal group. Additionally, acetylcholinesterase activity and glutamate decarboxylase 65/67 expression declined in the cingulate cortex. Our results reveal that spatial memory impairment in animals with selective basal forebrain cholinergic neuron damage is associated with a functional decline in the GABAergic and cholinergic system associated with cingulate cortex glucose hypometabolism.

Surface Modified Long Period Fiber Grating Sensor for Rapid Detection of Aspergillus Niger Fungal Spores

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Gambhir, Monika; Gupta, Shilpi; John, Priya; Mahakud, Ramakanta; Kumar, Jitendra; Prakash, Om

2018-03-01

We present development of a compact and label-free sensor based on the surface modification of copper vapor laser fabricated long period fiber gratings for detection of airborne Aspergillus niger (A. niger) fungal spores. Surface of sensors were functionalized with monoclonal glucose oxidases IgG1 for target-specific covalent binding. In process of functionalization and binding of 103 cfu/ml of pathogenic A. niger fungal spores, notable shorter wave transition in resonance wavelength from 1562.93 nm to 1555.97 nm, and significant reduction in peak loss from 61.72 dB to 57.48 dB were recorded. The implementation was cost effective and yielded instantaneous results.

Hypothalamic glucose sensing: making ends meet

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Vanessa eRouth

2014-12-01

Full Text Available The neuroendocrine system governs essential survival and homeostatic functions. For example, growth is needed for development. Thermoregulation maintains optimal core temperature in a changing environment. Reproduction ensures species survival. Stress and immune responses enable an organism to overcome external and internal threats. The circadian system regulates arousal and sleep such that vegetative and active functions do not overlap. All of these functions require a significant portion of the body’s energy. As the integrator of the neuroendocrine system, the hypothalamus carefully assesses the energy status of the body in order to appropriately partition resources to provide for each system without compromising the others. While doing so the hypothalamus must ensure that adequate glucose levels are preserved for brain function since glucose is the primary fuel of the brain. To this end, the hypothalamus contains specialized glucose sensing neurons which are scattered throughout the nuclei controlling distinct neuroendocrine functions. We hypothesize that these neurons play a key role in enabling the hypothalamus to partition energy to meet these peripheral survival needs without endangering the brain’s glucose supply. The goal of this review is to describe the varied mechanisms underlying glucose sensing in neurons within discrete hypothalamic nuclei. We will then evaluate the way in which peripheral energy status regulates glucose sensitivity. For example, during energy deficit such as fasting specific hypothalamic glucose sensing neurons become sensitized to decreased glucose. This increases the gain of the information relay when glucose availability is a greater concern for the brain. Finally, changes in glucose sensitivity under pathological conditions (e.g., recurrent insulin-hypoglycemia, diabetes will be addressed. The overall goal of this review is to place glucose sensing neurons within the context of hypothalamic control of

Glucose biosensor based on glucose oxidase immobilized on a nanofilm composed of mesoporous hydroxyapatite, titanium dioxide, and modified with multi-walled carbon nanotubes

International Nuclear Information System (INIS)

Li, J.; Kuang, D.; Feng, Y.; Zhang, F.; Liu, M.

2012-01-01

We report on a highly sensitive glucose biosensor that was fabricated from a composite made from mesoporous hydroxyapatite and mesoporous titanium dioxide which then were ultrasonically mixed with multi-walled carbon nanotubes to form a rough nanocomposite film. This film served as a platform to immobilize glucose oxidase onto a glassy carbon electrode. The morphological and electrochemical properties of the film were examined by scanning electron microscopy and electrochemical impedance spectroscopy. Cyclic voltammetry and chronoamperometry were used to characterize the electrochemical performances of the biosensor which exhibited excellent electrocatalytic activity to the oxidation of glucose. At an operating potential of 0. 3 V and pH 6. 8, the sensor displays a sensitivity of 57. 0 μA mM -1 cm -2 , a response time of <5 s, a linear dynamic range from 0. 01 to 15. 2 mM, a correlation coefficient of 0. 9985, and a detection limit of 2 μM at an SNR of 3. No interferences are found for uric acid, ascorbic acid, dopamine and most carbohydrates. The sensor is stable and was successfully applied to the determination of glucose in real samples. (author)

Continuous glucose monitoring microsensor with a nanoscale conducting matrix and redox mediator

Science.gov (United States)

Pesantez, Daniel

The major limiting factor in kidney clinical transplantation is the shortage of transplantable organs. The current inability to distinguish viability from non-viability on a prospective basis represents a major obstacle in any attempt to expand organ donor criteria. Consequently, a way to measure and monitor a relevant analyte to assess kidney viability is needed. For the first time, the initial development and characterization of a metabolic microsensor to assess kidney viability is presented. The rate of glucose consumption appears to serve as an indicator of kidney metabolism that may distinguish reversible from irreversible kidney damage. The proposed MetaSense (Metabolic Sensor) microdevice would replace periodic laboratory diagnosis tests with a continuous monitor that provides real-time data on organ viability. Amperometry, a technique that correlates an electrical signal with analyte concentration, is used as a method to detect glucose concentrations. A novel two-electrode electrochemical sensing cell design is presented. It uses a modified metallic working electrode (WE) and a bare metallic reference electrode (RE) that acts as a pseudo-reference/counter electrode as well. The proposed microsensor has the potential to be used as a minimally invasive sensor for its reduced number of probes and very small dimensions achieved by micromachining and lithography. In order to improve selectivity of the microdevice, two electron transfer mechanisms or generations were explored. A first generation microsensor uses molecular oxygen as the electron acceptor in the enzymatic reaction and oxidizes hydrogen peroxide (H2O2) to get the electrical signal. The microsensor's modified WE with conductive polymer polypyrrole (PPy) and corresponding enzyme glucose oxidase (GOx) immobilized into its matrix, constitutes the electrochemical detection mechanism. Photoluminescence spectroscopic analysis confirmed and quantified enzyme immobilized concentrations within the matrix. In

Synthesis of CdS quantum dots decorated graphene nanosheets and non-enzymatic photoelectrochemical detection of glucose

International Nuclear Information System (INIS)

Zhang, Xuyan; Xu, Fang; Zhao, Bingqing; Ji, Xin; Yao, Yanwen; Wu, Dapeng; Gao, Zhiyong; Jiang, Kai

2014-01-01

Graphical abstract: - Highlights: • Graphene-CdS hybrid materials were prepared via one-step hydrothermal method. • Graphene-CdS was used as non-enzymatic photoelectrochemical sensor to detect glucose. • Glucose in real sample was detected and showed good specificity and sensitivity. - ABSTRACT: Graphene-CdS quantum dots (QDs) hybrid materials were successfully prepared via one-step hydrothermal method. CdS QDs with average size of ∼6 nm were dispersed on graphene sheets with high coverage through non-covalent bonding. Photocurrent and electrochemical impedance spectroscopy (EIS) results suggested that the best dosage of graphene oxide for graphene-CdS hybrid materials is 0.5% (G0.5-CdS). When G0.5-CdS QDs was used as photoanode materials in non-enzymatic sensor, and the sensor was used to detect glucose and displayed satisfactory analytical performance with good linear range from 0.1∼4 mmol dm −3 with a detection limit of 7 μmol dm −3 at a signal-to-noise ratio of 3. The sensor also possessed high selectivity and durability in trace detection of glucose

Synthesis of novel CuO nanosheets and their non-enzymatic glucose sensing applications.

Science.gov (United States)

Ibupoto, Zafar Hussain; Khun, Kimleang; Beni, Valerio; Liu, Xianjie; Willander, Magnus

2013-06-20

In this study, we have developed a sensitive and selective glucose sensor using novel CuO nanosheets which were grown on a gold coated glass substrate by a low temperature growth method. X-ray differaction (XRD) and scanning electron microscopy (SEM) techniques were used for the structural characterization of CuO nanostructures. CuO nanosheets are highly dense, uniform, and exhibited good crystalline array structure. X-ray photoelectron spectroscopy (XPS) technique was applied for the study of chemical composition of CuO nanosheets and the obtained information demonstrated pure phase CuO nanosheets. The novel CuO nanosheets were employed for the development of a sensitive and selective non-enzymatic glucose sensor. The measured sensitivity and a correlation coefficient are in order 5.20 × 10² µA/mMcm² and 0.998, respectively. The proposed sensor is associated with several advantages such as low cost, simplicity, high stability, reproducibility and selectivity for the quick detection of glucose.

Synthesis of Novel CuO Nanosheets and Their Non-Enzymatic Glucose Sensing Applications

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Magnus Willander

2013-06-01

Full Text Available In this study, we have developed a sensitive and selective glucose sensor using novel CuO nanosheets which were grown on a gold coated glass substrate by a low temperature growth method. X-ray differaction (XRD and scanning electron microscopy (SEM techniques were used for the structural characterization of CuO nanostructures. CuO nanosheets are highly dense, uniform, and exhibited good crystalline array structure. X-ray photoelectron spectroscopy (XPS technique was applied for the study of chemical composition of CuO nanosheets and the obtained information demonstrated pure phase CuO nanosheets. The novel CuO nanosheets were employed for the development of a sensitive and selective non-enzymatic glucose sensor. The measured sensitivity and a correlation coefficient are in order 5.20 × 102 µA/mMcm2 and 0.998, respectively. The proposed sensor is associated with several advantages such as low cost, simplicity, high stability, reproducibility and selectivity for the quick detection of glucose.

Measuring brain glucose phosphorylation with labeled glucose

International Nuclear Information System (INIS)

Brondsted, H.E.; Gjedde, A.

1988-01-01

This study tested whether glucose labeled at the C-6 position generates metabolites that leave brain so rapidly that C-6-labeled glucose cannot be used to measure brain glucose phosphorylation (CMRGlc). In pentobarbital-anesthetized rats, the parietal cortex uptake of [ 14 C]glucose labeled in the C-6 position was followed for times ranging from 10 s to 60 min. We subtracted the observed radioactivity from the radioactivity expected with no loss of labeled metabolites from brain by extrapolation of glucose uptake in an initial period when loss was negligible. The observed radioactivity was a monoexponentially declining function of the total radioactivity expected in the absence of metabolite loss. The constant of decline was 0.0077.min-1 for parietal cortex. Metabolites were lost from the beginning of the experiment. However, with correction for the loss of labeled metabolites, it was possible to determine an average CMRGlc between 4 and 60 min of circulation of 64 +/- 4 (SE; n = 49) mumol.hg-1.min-1

Higher Fasting Plasma Glucose Levels, within the Normal Range, are Associated with Decreased Processing Speed in High Functioning Young Elderly.

Science.gov (United States)

Raizes, Meytal; Elkana, Odelia; Franko, Motty; Ravona Springer, Ramit; Segev, Shlomo; Beeri, Michal Schnaider

2016-01-01

We explored the association of plasma glucose levels within the normal range with processing speed in high functioning young elderly, free of type 2 diabetes mellitus (T2DM). A sample of 41 participants (mean age = 64.7, SD = 10; glucose 94.5 mg/dL, SD = 9.3), were examined with a computerized cognitive battery. Hierarchical linear regression analysis showed that higher plasma glucose levels, albeit within the normal range (levels may have an impact on cognitive function.

Implementation of an integrating sphere for the enhancement of noninvasive glucose detection using quantum cascade laser spectroscopy

Science.gov (United States)

Werth, Alexandra; Liakat, Sabbir; Dong, Anqi; Woods, Callie M.; Gmachl, Claire F.

2018-05-01

An integrating sphere is used to enhance the collection of backscattered light in a noninvasive glucose sensor based on quantum cascade laser spectroscopy. The sphere enhances signal stability by roughly an order of magnitude, allowing us to use a thermoelectrically (TE) cooled detector while maintaining comparable glucose prediction accuracy levels. Using a smaller TE-cooled detector reduces form factor, creating a mobile sensor. Principal component analysis has predicted principal components of spectra taken from human subjects that closely match the absorption peaks of glucose. These principal components are used as regressors in a linear regression algorithm to make glucose concentration predictions, over 75% of which are clinically accurate.

A Glucose Sensor Based on Glucose Oxidase Immobilized by Electrospinning Nanofibrous Polymer Membranes Modified with Carbon Nanotubes

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You Wang

2013-05-01

Full Text Available A glucose biosensor based on glucose oxidase immobilized by electrospinning nanofibrous membranes has been developed. Nanofibrous membranes were electrospun from the solution of poly(acrylonitrile-co-acrylic acid containing carbon nanotubes suspension and directly deposited on Pt electrodes for immobilizing glucose oxidase. The morphologies and structure of the nanofibrous membranes with or without carbon nanotubes were characterized by scanning electron microscopy. The fabrication parameters of nanofibers were optimized such as thickness of the nanofibrous membranes and mass ration of carbon nanotubes. The biosensor showed the relationship with a concentration range of 0.1–10 mM and response time was 60 s. The sensitivity of carbon nanotubes modified biosensors was two times larger than which of no carbon nanotubes modified ones. The pH effect, interference and lifetime of biosensors were discussed.

First Clinical Experience with Retrospective Flash Glucose Monitoring (FGM) Analysis in South Africa

Science.gov (United States)

Distiller, Larry A.; Cranston, Iain; Mazze, Roger

2016-01-01

Background: In 2014, an innovative blinded continuous glucose monitoring system was introduced with automated ambulatory glucose profile (AGP) reporting. The clinical use and interpretation of this new technology has not previously been described. Therefore we wanted to understand its use in characterizing key factors related to glycemic control: glucose exposure, variability, and stability, and risk of hypoglycemia in clinical practice. Methods: Clinicians representing affiliated diabetes centers throughout South Africa were trained and subsequently were given flash glucose monitoring readers and 2-week glucose sensors to use at their discretion. After patient use, sensor data were collected and uploaded for AGP reporting. Results: Complete data (sensor AGP with corresponding clinical information) were obtained for 50 patients with type 1 (70%) and type 2 diabetes (30%), irrespective of therapy. Aggregated analysis of AGP data comparing patients with type 1 versus type 2 diabetes, revealed that despite similar HbA1c values between both groups (8.4 ± 2 vs 8.6 ± 1.7%, respectively), those with type 2 diabetes had lower mean glucose levels (9.2 ± 3 vs 10.3 mmol/l [166 ± 54 vs 185 mg/dl]) and lower indices of glucose variability (3.0 ± 1.5 vs 5.0 ± 1.9 mmol/l [54 ± 27 vs 90 ± 34.2 mg/dl]). This highlights key areas for future focus. Conclusions: Using AGP, the characteristics of glucose exposure, variability, stability, and hypoglycemia risk and occurrence were obtained within a short time and with minimal provider and patient input. In a survey at the time of the follow-up visit, clinicians indicated that aggregated AGP data analysis provided important new clinical information and insights. PMID:27154973

Carbon Nanotube Yarn-Based Glucose Sensing Artificial Muscle.

Science.gov (United States)

Lee, Junghan; Ko, Sachan; Kwon, Cheong Hoon; Lima, Márcio D; Baughman, Ray H; Kim, Seon Jeong

2016-04-01

Boronic acid (BA), known to be a reversible glucose-sensing material, is conjugated to a nanogel (NG) derived from hyaluronic acid biopolymer and used as a guest material for a carbon multiwalled nanotube (MWNT) yarn. By exploiting the swelling/deswelling of the NG that originates from the internal anionic charge changes resulting from BA binding to glucose, a NG MWNT yarn artificial muscle is obtained that provides reversible torsional actuation that can be used for glucose sensing. This actuator shows a short response time and high sensitivity (in the 5-100 × 10(-3) m range) for monitoring changes in glucose concentration in physiological buffer, without using any additional auxiliary substances or an electrical power source. It may be possible to apply the glucose-sensing MWNT yarn muscles as implantable glucose sensors that automatically release drugs when needed or as an artificial pancreas. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Glucose allostasis

DEFF Research Database (Denmark)

Stumvoll, Michael; Tataranni, P Antonio; Stefan, Norbert

2003-01-01

individuals with normal glucose tolerance, normoglycemia can always be maintained by compensatorily increasing AIR in response to decreasing M (and vice versa). This has been mathematically described by the hyperbolic relationship between AIR and M and referred to as glucose homeostasis, with glucose......In many organisms, normoglycemia is achieved by a tight coupling of nutrient-stimulated insulin secretion in the pancreatic beta-cell (acute insulin response [AIR]) and the metabolic action of insulin to stimulate glucose disposal (insulin action [M]). It is widely accepted that in healthy...... concentration assumed to remain constant along the hyperbola. Conceivably, glucose is one of the signals stimulating AIR in response to decreasing M. Hypothetically, as with any normally functioning feed-forward system, AIR should not fully compensate for worsening M, since this would remove the stimulus...

Design of Amperometric Biosensors for the Detection of Glucose Prepared by Immobilization of Glucose Oxidase on Conducting (PolyThiophene Films

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Maria Pilo

2018-01-01

Full Text Available Enzyme-based sensors have emerged as important analytical tools with application in diverse fields, and biosensors for the detection of glucose using the enzyme glucose oxidase have been widely investigated. In this work, the preparation of biosensors by electrochemical polymerization of (polythiophenes, namely 2,2′-bithiophene (2,2′-BT and 4,4′-bis(2-methyl-3-butyn-2-ol-2,2′-bithiophene (4,4′-bBT, followed by immobilization of glucose oxidase on the films, is described. N-cyclohexyl-N′-(2-morpholinoethylcarbodiimide metho-p-toluenesulfonate (CMC was used as a condensing agent, and p-benzoquinone (BQ was used as a redox mediator in solution. The glucose oxidase electrodes with films of 2,2′-BT and 4,4′-bBT were then tested for their ability in detecting glucose from synthetic and real samples (pear, apricot, and peach fruit juices.

Analysis of the transfer function for layered piezoelectric ultrasonic sensors

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E. Gutiérrrez-Reyes

2017-06-01

Full Text Available We model theoretically the voltage response to an acoustic pulse of a multilayer system forming a low noise capacitive sensor including a Polyvinylidene Fluoride piezoelectric film. First we model a generic piezoelectric detector consisting of a piezoelectric film between two metallic electrodes that are the responsible to convert the acoustic signal into a voltage signal. Then we calculate the pressure-to-voltage transfer function for a N-layer piezo-electric capacitor detector, allowing to study the effects of the electrode and protective layers thickness in typical layered piezoelectric sensors. The derived transfer function, when multiplied by the Fourier transform of the incident acoustic pulse, gives the voltage electric response in the frequency domain. An important concern regarding the transfer function is that it may have zeros at specific frequencies, and thus inverting the voltage Fourier transform of the pulse to recover the pressure signal in the time domain is not always, in principle, possible. Our formulas can be used to predict the existence and locations of such zeroes. We illustrate the use of the transfer function by predicting the electric signal generated at a multilayer piezoelectric sensor to an ultrasonic pulse generated photoacoustically by a laser pulse at a three media system with impedance mismatch. This theoretical calculations are compared with our own experimental measurements.

Enzyme-functionalized thin-cladding long-period fiber grating in transition mode at dispersion turning point for sugar-level and glucose detection

Science.gov (United States)

Badmos, Abdulyezir A.; Sun, Qizhen; Sun, Zhongyuan; Zhang, Junxi; Yan, Zhijun; Lutsyk, Petro; Rozhin, Alex; Zhang, Lin

2017-02-01

Enzyme-functionalized dual-peak long-period fiber grating (LPFG) inscribed in 80-μm-cladding B/Ge codoped single-mode fiber is presented for sugar-level and specific glucose detection. Before enzyme functionalization, the dual-peak LPFG was employed for refractive index sensing and sugar-level detection and high sensitivities of ˜4298.20 nm/RIU and 4.6696 nm/% were obtained, respectively. Glucose detection probe was attained by surface functionalization of the dual-peak LPFG via covalent binding with aminopropyl triethoxysilane used as a binding site. Optical micrographs confirmed the presence of enzyme. The surface-functionalized dual-peak LPFG was tested with D-(+)-glucose solution of different concentrations. While the peak 2 at the longer wavelength was suitable only to measure lower glucose concentration (0.1 to 1.6 mg/ml) recording a high sensitivity of 12.21±0.19 nm/(mg/ml), the peak 1 at the shorter wavelength was able to measure a wider range of glucose concentrations (0.1 to 3.2 mg/ml) exhibiting a maximum resonance wavelength shift of 7.12±0.12 nm/mg/ml. The enzyme-functionalized dual-peak LPFG has the advantage of direct inscription of highly sensitive grating structures in thin-cladding fibre without etching, and most significantly, its sensitivity improvement of approximately one order of magnitude higher than previously reported LPFG and excessively tilted fibre grating (Ex-TFG) for glucose detection.

Effect of intravenous glucose infusion on renal function in normal man and in insulin-dependent diabetics

DEFF Research Database (Denmark)

Frandsen, M; Parving, H H; Christiansen, JS

1981-01-01

The effect of intravenous glucose infusion on glomerular filtration rate and renal plasma flow (constant infusion technique using 125I-iothalamate and 131I-hippuran) and on urinary excretion of albumin and beta-2-microglobulin were studied in ten normal subjects and seven metabolically well......-controlled insulin-dependent diabetics. Following glucose infusion in normal subjects (n = 10) blood glucose increased from 4.7 +/- 0.1 to 10.9 +/- 0.4 mmol/l (SEM) (p less than or equal to 0.01). Glomerular filtration rate increased from 116 +/- 2 to 123 +/- 3 ml/mi x 1.73 m2 (p less than or equal to 0.01), while...... no change in renal plasma flow was seen - 552 +/- 11 versus 553 +/- 18 ml/min x 1.73 m2. Volume expansion with intravenous saline infusion in six of the normal subjects induced no changes in blood glucose or kidney function. In seven strictly controlled insulin-dependent diabetics, blood glucose values were...

ZnO nano-array-based EGFET biosensor for glucose detection

Science.gov (United States)

Qi, Junjie; Zhang, Huihui; Ji, Zhaoxia; Xu, Minxuan; Zhang, Yue

2015-06-01

Electrochemical biosensors are normally based on enzymatic catalysis of a reaction that produces or consumes electrons and the sensing membranes dominate the performance. In this work, ZnO nano-array-based EGFETs were fabricated for pH and glucose detection. The ZnO nano-arrays prepared via low-temperature hydrothermal method were well-aligned, with an average length of 2 μm and diameter of 100-150 nm, and have a typical hexagonal wurtzite structure. The sensor performed with a sensitivity of 45 mV/pH and response time of about 6-7 s from pH = 4-12. UV irradiation can improve the Vref response as a result of the formation of a depletion region at the surface of ZnO nanomaterials. Due to its high specific surface area, the ZnO nano-array EGFET sensor showed a sensitivity of -0.395 mV/μM to the glucose detection in a concentration range between 20 and 100 μM. These EGFET glucose biosensors demonstrate a low detectable concentration (20 μM) with good linearity, therefore may be used to detect glucose in saliva and tears at much lower concentrations than that in blood.

Functionalized graphene/silicon chemi-diode H2 sensor with tunable sensitivity

International Nuclear Information System (INIS)

Uddin, Md Ahsan; Singh, Amol Kumar; Sudarshan, Tangali S; Koley, Goutam

2014-01-01

A reverse bias tunable Pd- and Pt-functionalized graphene/Si heterostructure Schottky diode H 2 sensor has been demonstrated. Compared to the graphene chemiresistor sensor, the chemi-diode sensor offers more than one order of magnitude higher sensitivity as the molecular adsorption induced Schottky barrier height change causes the heterojunction current to vary exponentially in reverse bias. The reverse bias operation also enables low power consumption, as well as modulation of the atomically thin graphene’s Fermi level, leading to tunable sensitivity and detection of H 2 down to the sub-ppm range. (paper)

Acute Effects of Glucose and Fructose Administration on the Neural Correlates of Cognitive Functioning in Healthy Subjects: A Pilot Study

Directory of Open Access Journals (Sweden)

Davide Zanchi

2018-03-01

Full Text Available The present randomized double-blinded cross-over study aims to extensively study the neural correlates underpinning cognitive functions in healthy subjects after acute glucose and fructose administration, using an integrative multimodal neuroimaging approach. Five minutes after glucose, fructose, or placebo administration through a nasogastric tube, 12 participants underwent 3 complementary neuroimaging techniques: 2 task-based functional magnetic resonance imaging (fMRI sequences to assess working memory (N-back and response inhibition (Go/No-Go and one resting state fMRI sequence to address the cognition-related fronto-parietal network (FPN and salience network (SN. During working memory processing, glucose intake decreased activation in the anterior cingulate cortex (ACC relative to placebo, while fructose decreased activation in the ACC and sensory cortex relative to placebo and glucose. During response inhibition, glucose and fructose decreased activation in the ACC, insula and visual cortex relative to placebo. Resting state fMRI indicated increased global connectivity strength of the FPN and the SN during glucose and fructose intake. The results demonstrate that glucose and fructose lead to partially different partially overlapping changes in regional brain activities that underpin cognitive performance in different tasks.