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Sample records for amperometry

  1. Exocytosis: using amperometry to study presynaptic mechanisms of neurotoxicity

    NARCIS (Netherlands)

    Westerink, R.H.S.

    2004-01-01

    The development of carbon fiber microelectrode amperometry enabled detailed investigation of the presynaptic response at the single cell level with single vesicle resolution. Consequently, amperometry allowed for detailed studies into the presynaptic mechanisms underlying neurotoxicity. This review

  2. Mediated amperometry reveals different modes of yeast responses to sugars.

    Science.gov (United States)

    Garjonyte, Rasa; Melvydas, Vytautas; Malinauskas, Albertas

    2016-02-01

    Menadione-mediated amperometry at carbon paste electrodes modified with various yeasts (Saccharomyces cerevisiae, Candida pulcherrima, Pichia guilliermondii and Debaryomyces hansenii) was employed to monitor redox activity inside the yeast cells induced by glucose, fructose, sucrose, maltose or galactose. Continuous measurements revealed distinct modes (transient or gradually increasing) of the current development during the first 2 to 3 min after subjection to glucose, fructose and sucrose at electrodes containing S. cerevisiae and non-Saccharomyces strains. Different modes (increasing or decreasing) of the current development after yeast subjection to galactose at electrodes with S. cerevisiae or D. hansenii and at electrodes with C. pulcherrima and P. guilliermondii suggested different mechanisms of galactose assimilation.

  3. Application of triple potential step amperometry method for quantitative electroanalysis

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A novel quantitative electroanalysis method, triple potential step amperometry (TPSA), was developed and explained with an example of nitrobenzene analyzing in water. The selectivity of TPSA was improved by controlling the potential step within a narrow interval and using enzyme-modified electrode, the narrow potential step makes the method avoid most interferents, and enzyme-modified electrode can enhance the response of target substance selectively. The peak area was investigated for quantitative calibration, such as nitrobenzene concentration showing a linear relation with the peak area, with the correlation coefficients being 0.9995. The t-test and F-test were applied to evaluating the reliability of TPSA, the results showed that there was no evidence of systematic error for TPSA, and the method was of no significant difference from CV. The merit of fast detecting and few potential changing times make the TPSA suitably applicable to low-cost automatic monitoring equipments.

  4. Substrate-dependent kinetics in tyrosinase-based biosensing: amperometry vs. spectrophotometry

    NARCIS (Netherlands)

    Rassaei, L.; Cui, J.; Goluch, E.D.; Lemay, S.G.

    2012-01-01

    Despite the broad use of enzymes in electroanalytical biosensors, the influence of enzyme kinetics on the function of prototype sensors is often overlooked or neglected. In the present study, we employ amperometry as an alternative or complementary method to study the kinetics of tyrosinase, whose

  5. Simultaneous determination of flavonoids and anthraquinones in chrysanthemum by capillary electrophoresis with amperometry detection

    Institute of Scientific and Technical Information of China (English)

    Yin Yan Zhang; Zi Cheng Li; Jin Kun Zhu; Zhi Yong Yang; Qing Jiang Wang; Pin Gang He; Yu Zhi Fang

    2010-01-01

    A high-performance capillary electrophoresis with amperometry detection method(CE-AD)has been developed for the analysis of flavonoids and anthraquinones(emodin,kaempferol,apigenin,luteolin and rhein)in chrysanthemum.Under optimum conditions,these five analytes were base-line separated within 17 min using a borate-phosphate running buffer(1.5 × 10-2mol/L borate-3 × 10-2 mol/L phosphate running buffer,pH 9.0)at a working potential of+0.90 V(vs.SCE)and a separation voltage of 19 kV.The linear relationship between concentration and current response was obtained with detection limits(S/N = 3)ranging from 1.0 × 10-7 to 2.1 × 10-7 g/mL for all analytes.This proposed method was successfully used in the analysis of four kinds of chrysanthemum with relatively simple extraction procedures,the assay results were satisfactory.

  6. Novel microfluidic system for online monitoring of biofilm dynamics by electrical impedance spectroscopy and amperometry

    Science.gov (United States)

    Bruchmann, Julia; Sachsenheimer, Kai; Schwartz, Thomas; Rapp, Bastian E.

    2016-03-01

    Biofilm formation is ubiquitous in nature where microorganisms attach to surfaces and form highly adapted and protected communities. In technical and industrial systems like drinking water supply, food production or shipping industry biofilms are a major cause of product contamination, biofouling, and biocorrosion. Therefore, understanding of biofilm formation and means of preventing biofilm formation is important to develop novel biofilm treatment strategies. A system allowing directly online detection and monitoring biofilm formation is necessary. However, until today, there are little to none technical systems featuring a non-destructive real-time characterization of biofilm formation in a highthroughput manner. This paper presents such a microfluidic system based on electrical impedance spectroscopy (EIS) and amperomertic current measurement. The sensor consists of four modules, each housing 24 independent electrodes within 12 microfluidic channels. Attached biomass on the electrodes is monitored as increased inhibition in charge transfer by EIS and a change in metabolic activity is measured as change in produced electric current by amperometry. This modular sensor system is highly adaptable and suitable for a broad range of microbiological applications. Among others, biofilm formation processes can be characterized online, biofilm manipulation like inactivation or destabilization can be monitored in real-time and gene expression can be analyzed in parallel. The use of different electrode designs allows effective biofilm studies during all biofilm phases. The whole system was recently extended by an integrated pneumatic microfluidic pump which enables easy handling procedures. Further developments of this pumping module will allow a fully- automated computer-controlled valving and pumping.

  7. Simple SPE-HPLC determination of some common drugs and herbicides of environmental concern by pulsed amperometry.

    Science.gov (United States)

    Rivoira, L; De Carlo, R M; Cavalli, S; Bruzzoniti, M C

    2015-01-01

    In this work the electrochemical behavior of substances of environmental concern [bentazone, atrazine, carbamazepine, phenytoin and its metabolite 5-(4-hydroxyphenyl)-5-phenylhydantoin, HPPH] on a glassy carbon working electrode (Ag/AgCl reference electrode) was studied with the aim to develop a HPLC method coupled with amperometric detection. Constant potential (DC), pulsed amperometric detection modes were studied. For the pulsed mode, several waveforms were set and investigated. Detection conditions were optimized as a function of eluent pH. In order to reduce the limits of detection and to analyze natural water samples, a SPE protocol was optimized to be coupled to the developed procedure. For this aim, five sorbents of different physico-chemical characteristics were tested optimizing a recovery procedure for each of the cartridge evaluated. At the optimized SPE conditions, recoveries were included in the range (R=90.2-100.5% for all the analytes, with excellent reproducibility (<%, n=3). The method detection limits obtained by pulsed amperometry after the SPE protocol (preconcentration factor 100) were 113 ng L(-1) (0.47 nmol L(-1)), 67 ng L(-1) (0.25 nmol L(-1)), 234 ng L(-1) (1.1 nmol L(-1)), for bentazone, HPPH and carbamazepine, respectively. Robustness of the method was assessed for each analyte at a concentration level corresponding to about three times the limit of detection, through the evaluation of intra-day (n=13) and inter-day tests (4 days, n=52). Finally the method was successfully applied for the analysis of a river sample (Po River, Turin, Italy).

  8. Pulsed Amperometry for Anti-fouling of Boron-doped Diamond in Electroanalysis of β-Agonists: Application to Flow Injection for Pharmaceutical Analysis

    Directory of Open Access Journals (Sweden)

    Duangjai Nacapricha

    2006-01-01

    Full Text Available This work presents the construction and application of boron-doped diamond(BDD thin film electrode as sensor for the determination of three β-agonists, viz.salbutamol, terbutaline and clenbuterol. Although well-known as a chemically inertmaterial, BDD film however shows fouling in detection of these compounds using fixedpotentialmode amperometry. A suitable waveform for pulsed amperometric detection(PAD was developed and used to determine the agonist compounds. It was seen that thedeveloped PAD significantly refreshed the BDD surface for long-term detection in flowinjection analysis. Linear working ranges were 0.5-100 μM, 1.0-100 μM and 0.5-50 μM forsalbutamol, terbutaline and clenbuterol, respectively. The developed PAD-BDD system wasapplied to successfully determine salbutamol and terbutaline in commercial pharmaceuticalproducts. The methods were validated with a capillary electrophoresis method.

  9. Research on the Determination of COD in Water by Amperometry%安培法直接测定水体中COD的方法研究

    Institute of Scientific and Technical Information of China (English)

    杜宝中; 路蕾蕾; 唐建红; 孙莎; 屈敏佳

    2011-01-01

    以Ti/PbO2-Pt-Hg/Hg2Cl2为电极组成三电极体系,采用安培法直接测定水体中葡萄糖COD值.优化测试条件为:工作电极电位1.4 V,电解液浓度0.02mol/L,电解时间1.5 min.工作电极的电流响应值与COD值在标准溶液20~200mg/L范围内呈线性关系,检出限为10 mg/L.通过增大电位气泡更新法来再生工作电极具有简便、快速,重现性好的优点,当其与标准法对照用于实际水样COD的测定时相对误差<3%.%A threeelectrode system with Ti/PbO2 electrode as working anode is directly used to detect COD in water by amperometry.The optimized experimental conditions are: working electrode potential is 1.4 V; electrolyte concentration is 0.02 mol/L; determination time is 1.5 min.The current value on the anode in a standard solution with different concentrations of glucose appears to have the linear relation with COD in the range of 20 ~200 mg/L, whose detection limit is 10 mg/L.The surface of Ti/PbO2 electrode is refreshed by bubbling to get good reproducibility.The method is applied to the determination of the COD in real samples with such good characteristions as simplicity, fastness and repeatability.It is found that the relative error between the determined values obtained by this method and the standard method is less than 3%.

  10. Improved bacteria detection by coupling magneto-immunocapture and amperometry at flow-channel microband electrodes

    DEFF Research Database (Denmark)

    Laczka, Olivier; Maesa, José-María; Godino, Neus;

    2011-01-01

    with Escherichia coli evidenced a linear response for concentrations ranging 102–108cellml−1, with a limit of detection of 55cellsml−1 in PBS, without pre-enrichment steps. Furthermore, 100cellsml−1 could be detected in milk, and with negligible interference by non-target bacteria such as Pseudomonas....

  11. Striatal dopamine release in a schizophrenia mouse model measured by electrochemical amperometry in vivo.

    Science.gov (United States)

    Xu, Huadong; Zuo, Panli; Wang, Shirong; Zhou, Li; Sun, Xiaoxuan; Hu, Meiqin; Liu, Bin; Wu, Qihui; Dou, Haiqiang; Liu, Bing; Zhu, Feipeng; Teng, Sasa; Zhang, Xiaoyu; Wang, Li; Li, Qing; Jin, Mu; Kang, Xinjiang; Xiong, Wei; Wang, Changhe; Zhou, Zhuan

    2015-06-01

    Schizophrenia is a severely devastating mental disorder, the pathological process of which is proposed to be associated with the dysfunction of dopaminergic transmission. Our previous results have demonstrated slower kinetics of transmitter release (glutamate release in hippocampus and norepinephrine release in adrenal slice) in a schizophrenia model, dysbindin null-sandy mice. However, whether dopaminergic transmission in the nigrostriatal pathway contributes to the pathology of dysbindin-/- mice remains unknown. Here, we have provided a step-by-step protocol to be applied in the in vivo amperometric recording of dopamine (DA) release from the mouse striatum evoked by an action potential (AP) pattern. With this protocol, AP pattern-dependent DA release was recorded from dysbindin-/- mice striatum in vivo. On combining amperometric recording in slices and electrophysiology, we found that in dysbindin-/- mice, (1) presynaptically, AP-pattern dependent dopamine overflow and uptake were intact in vivo; (2) the recycling of the dopamine vesicle pool remained unchanged. (3) Postsynaptically, the excitability of medium spiny neuron (MSN) was also normal, as revealed by patch-clamp recordings in striatal slices. Taken together, in contrast to reduced norepinephrine release in adrenal chromaffin cells, the dopaminergic transmission remains unchanged in the nigrostriatal pathway in dysbindin-/- mice, providing a new insight into the functions of the schizophrenia susceptibility gene dysbindin.

  12. Real-time monitoring of auxin vesicular exocytotic efflux from single plant protoplasts by amperometry at microelectrodes decorated with nanowires.

    Science.gov (United States)

    Liu, Jun-Tao; Hu, Liang-Sheng; Liu, Yan-Ling; Chen, Rong-Sheng; Cheng, Zhi; Chen, Shi-Jing; Amatore, Christian; Huang, Wei-Hua; Huo, Kai-Fu

    2014-03-01

    Recent biochemical results suggest that auxin (IAA) efflux is mediated by a vesicular cycling mechanism, but no direct detection of vesicular IAA release from single plant cells in real-time has been possible up to now. A TiC@C/Pt-QANFA micro-electrochemical sensor has been developed with high sensitivity in detection of IAA, and it allows real-time monitoring and quantification of the quantal release of auxin from single plant protoplast by exocytosis.

  13. Finding out egyptian gods' secret using analytical chemistry: biomedical properties of egyptian black makeup revealed by amperometry at single cells.

    Science.gov (United States)

    Tapsoba, Issa; Arbault, Stéphane; Walter, Philippe; Amatore, Christian

    2010-01-15

    Lead-based compounds were used during antiquity as both pigments and medicines in the formulation of makeup materials. Chemical analysis of cosmetics samples found in Egyptians tombs and the reconstitution of ancient recipes as reported by Greco-Roman authors have shown that two non-natural lead chlorides (laurionite Pb(OH)Cl and phosgenite Pb(2)Cl(2)CO(3)) were purposely synthesized and were used as fine powders in makeup and eye lotions. According to ancient Egyptian manuscripts, these were essential remedies for treating eye illness and skin ailments. This conclusion seems amazing because today we focus only on the well-recognized toxicity of lead salts. Here, using ultramicroelectrodes, we obtain new insights into the biochemical interactions between lead(II) ions and cells, which support the ancient medical use of sparingly soluble lead compounds. Submicromolar concentrations of Pb(2+) ions are shown to be sufficient for eliciting specific oxidative stress responses of keratinocytes. These consist essentially of an overproduction of nitrogen monoxide (NO degrees ). Owing to the biological role of NO degrees in stimulating nonspecific immunological defenses, one may argue that these lead compounds were deliberately manufactured and used in ancient Egyptian formulations to prevent and treat eye illnesses by promoting the action of immune cells.

  14. Probing the redox metabolism in the strictly anaerobic, extremely thermophilic, hydrogen-producing Caldicellulosiruptor saccharolyticus using amperometry

    DEFF Research Database (Denmark)

    Kostesha, Natalie; Willquist, Karin; Emnéus, Jenny;

    2011-01-01

    flow between cells harvested in the exponential and stationary growth phases. The electron flow of C. saccharolyticus was dependent on the NADH- and reduced ferredoxin generation flux and the competitive behavior of cytosolic and membrane-associated oxidoreductases. Sodium oxamate was used to inhibit...... electron flow were observed when cells were supplied with different carbon sources. A higher electrochemical response was detected when cells were supplied with xylose than with sucrose or glucose. Moreover, using the mediated electrochemical method, it was possible to detect differences in the electron...... in the intracellular electron flow and to probe redox enzyme properties of a strictly anaerobic thermophile in vivo....

  15. Determination of Phenol and Chlorophenols at Single-Wall Carbon Nanotubes/Poly(3,4-ethylenedioxythiophene) Modified Glassy Carbon Electrode Using Flow Injection Amperometry

    OpenAIRE

    Negussie Negash; Hailemichael Alemu; Merid Tessema

    2014-01-01

    Phenol and chlorophenols were investigated using single-wall carbon nanotubes (SWCNT) and poly(3,4-ethylenedioxythiophene) (PEDOT) composite modified glassy carbon electrode (SWCNT/PEDOT/GCE) as a detector in flow injection system. Optimization of experimental variables such as the detection potential, flow rate, and pH of the carrier solution (0.1 M sodium acetate) for the determination of phenol (P), 4-chlorophenol (CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachloro...

  16. Electrochemical measurements of serotonin (5-HT) release from the guinea pig mucosa using continuous amperometry with a boron-doped diamond microelectrode

    OpenAIRE

    Zhao, Hong; Bian, Xiaochun; Galligan, James J.; Swain, Greg M.

    2010-01-01

    Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) disorder characterized by chronic abdominal discomfort, including pain, bloating and changes in bowel habits. The exact cause of IBS is not entirely understood. Recent studies have shown that IBS may be associated with altered serotonin (5-hydroxytryptamine, 5-HT) levels within the GI tract. About 90% of 5-HT in the human body is produced and stored in enterochromaffin (EC) cells that reside in the mucosal layer of the intestine...

  17. 3D-Printed Fluidic Devices for Nanoparticle Preparation and Flow-Injection Amperometry Using Integrated Prussian Blue Nanoparticle-Modified Electrodes.

    Science.gov (United States)

    Bishop, Gregory W; Satterwhite, Jennifer E; Bhakta, Snehasis; Kadimisetty, Karteek; Gillette, Kelsey M; Chen, Eric; Rusling, James F

    2015-01-01

    A consumer-grade fused filament fabrication (FFF) 3D printer was used to construct fluidic devices for nanoparticle preparation and electrochemical sensing. Devices were printed using poly(ethylene terephthalate) and featured threaded ports to connect polyetheretherketone (PEEK) tubing via printed fittings prepared from acrylonitrile butadiene styrene (ABS). These devices included channels designed to have 800 μm × 800 μm square cross sections and were semitransparent to allow visualization of the solution-filled channels. A 3D-printed device with a Y-shaped mixing channel was used to prepare Prussian blue nanoparticles (PBNPs) under flow rates of 100 to 2000 μL min(-1). PBNPs were then attached to gold electrodes for hydrogen peroxide sensing. 3D-printed devices used for electrochemical measurements featured threaded access ports into which a fitting equipped with reference, counter, and PBNP-modified working electrodes could be inserted. PBNP-modified electrodes enabled amperometric detection of H2O2 in the 3D-printed channel by flow-injection analysis, exhibiting a detection limit of 100 nM and linear response up to 20 μM. These experiments show that a consumer-grade FFF printer can be used to fabricate low-cost fluidic devices for applications similar to those that have been reported with more expensive 3D-printing methods. PMID:25901660

  18. Amperometric determination of rutin on carbon paste electrodes

    Directory of Open Access Journals (Sweden)

    Pavla Macikova

    2010-12-01

    Full Text Available Three different carbon paste electrodes (i.e. unmodified, ironphthalocyanine and ionic liquid modified were tested to determinerutin by amperometry. The widest linear concentration range andlowest detection limit were obtained with unmodified carbon pasteelectrode.

  19. Study of electrochemical phosphate conversion coating of metallic surfaces

    International Nuclear Information System (INIS)

    After an overview on phosphate conversion coating processes, on models of iron electrochemical dissolution, on the passivation phenomenon, and on the phosphate conversion coating treatment, this research thesis reports a detailed study of this last process. The author presents the experimental method, reports the study of this process and of passivation under constant polarization. He reports the use of various techniques and conditions: chrono-amperometry, chrono-potentiometry, cyclic volt-amperometry

  20. Electro-active bio-films: formation, characterization and mechanisms

    International Nuclear Information System (INIS)

    Some bacteria, which are able to exchange electrons with a conductive material without mediator form on conductive surfaces electro-active bio-films. This bacterial property has been recently discovered (2001). Objectives of this work are to develop electro-active bio-films in various natural environments from indigenous flora, then through complementary electrochemical techniques (chrono-amperometry and cyclic voltammetry), to evaluate electro-activity of isolates coming from so-formed bio-films and to characterize mechanisms of electron transfer between bacteria and materials. First, electro-active bio-films have been developed under chrono-amperometry in garden compost and in water coming from Guyana mangrove. These bio-films were respectively able to use an electrode as electron acceptor (oxidation) or as electron donor (reduction). In compost, results obtained in chrono-amperometry and cyclic voltammetry suggest a two-step electron transfer: slow substrate consumption, then rapid electron transfer between bacteria and the electrode. Thereafter, the ability to reduce oxygen was demonstrated with cyclic voltammetry for facultative aerobic isolates from compost bio-films (Enterobacter spp. and Pseudomonas spp.) and for aerobic isolates obtained from marine electro-active bio-films (Roseobacter spp. in majority). Finally, bio-films inducing current increase in chrono-amperometry were developed in bioreactor with synthetic medium from a pure culture of isolates. Hence, for the first time, electro-activity of several anaerobic strains of Geobacter bremensis isolated from compost bio-films was highlighted. (author)

  1. Electrodeposited nanostructured MnO2 for non-enzymatic hydrogen peroxide sensing

    International Nuclear Information System (INIS)

    Electrodeposited MnO2 nanostructure was synthesized on indium tin oxide coated glass electrode by cyclic voltammetry. The as obtained samples were subsequently characterized by atomic force microscopy and their electro-catalytic response towards hydrogen peroxide in alkaline medium of 0.1M NaOH was studied using cyclic voltammetry and amperometry

  2. A novel non-enzymatic H{sub 2}O{sub 2} sensor based on polypyrrole nanofibers–silver nanoparticles decorated reduced graphene oxide nano composites

    Energy Technology Data Exchange (ETDEWEB)

    Moozarm Nia, Pooria, E-mail: pooriamn@yahoo.com; Lorestani, Farnaz, E-mail: farnaz.lorestani@siswa.um.edu.my; Meng, Woi Pei, E-mail: pmwoi@um.edu.my; Alias, Y., E-mail: yatimah70@um.edu.my

    2015-03-30

    Graphical abstract: - Highlights: • Decorating silver nanoparticles on the surface of graphene oxide nanocomposites. • Using and comparing two different electrochemical methods for reducing graphene oxide. • Investigating the effect of cyclic voltammetry and amperometry on electropolymerization of polypyrrole nanofibers. • The senor shows superior performances (LOD, LOQ, selectivity, repeatability, reproducibility and stability) towards H{sub 2}O{sub 2}. - Abstract: Graphene oxide (GO) decorated with silver nanoparticles (AgNPs), was electrochemically reduced on glassy carbon electrode (GCE) by an amperometry method (AMP-AgNPs-rGO/GCE). Then, Pyrrole was electropolymerized on the surface of the modified electrode through amperometry process in order to obtain nanofibers of polypyrrole (AMP-PpyNFs-AgNPs-rGO). Fourier-transform infrared transmission spectroscopy and X-ray diffraction approved that during the amperometry process, the GO and Ppy nanofibers were reduced and polymerized respectively and the silver nanoparticles were formed. Field emission scanning electron microscope images indicated that the silver nanoparticles were homogeneously distributed on the rGO surface with a narrow nano size distribution and polypyrrole synthesized in the form of nanofibers with diameter around 100 nm. The first linear section was in the range of 0.1–5 mM with a limit of detection of 1.099 and the second linear section raised to 90 mM with a correlation factor of 0.085 (S/N of 3)

  3. Fabrication of Functionalized Carbon Nanotube Buckypaper Electrodes for Application in Glucose Biosensors

    OpenAIRE

    Henry Papa; Melissa Gaillard; Leon Gonzalez; Jhunu Chatterjee

    2014-01-01

    A highly sensitive glucose detection method was developed using functionalized carbon nanotube buckypaper as a free standing electrode in an electrochemical biosensor. Glucose oxidase was immobilized onto various buckypaper samples in order to oxidize glucose resulting in a measureable current/voltage signal output of the biosensor. Cyclic voltammetry (CV) and amperometry were utilized to determine the sensitivity of these buckypaper electrodes. Sensors of three different types of buckypaper ...

  4. Electropolymerized phenol derivatives as permselective polymers for biosensor applications

    OpenAIRE

    Giammario, Calia; MONTI, Patrizia; Marceddu, Salvatore; Dettori, Maria A.; Fabbri, Davidé; Jaoua, Samir; O'Neill, Robert D.; Serra, Pier A.; Delogu, Giovanna; Migheli, Quirico

    2015-01-01

    Amperometric biosensors are often coated with a polymeric permselective film to avoid electroactive interference by reducing agents present in the target medium. Phenylenediamine and phenol monomers are commonly used to form these permselective films in the design of microsensors and biosensors. This paper aims to evaluate the permselectivity, stability and lifetime of polymers electrosynthesized using either constant potential amperometry (CPA) or cyclic voltammetry (CV) from naturally...

  5. Carbon Nanotubes Based Glucose Needle-type Biosensor

    OpenAIRE

    Hong Li; Yongquan Li; Minghao Sim; Wenjun Guan; Jinyan Jia

    2008-01-01

    A novel needle-type biosensor based on carbon nanotubes is reported. The biosensor was prepared by packing a mixture of multi-wall carbon nanotubes (MWCNTs), graphite powder and glucose oxidase (Gox) freeze-dried powder into a glass capillary of 0.5 mm inner diameter. The resulting amperometric biosensor was characterized electrochemically using amperometry in the presence of hydrogen peroxide and in the presence of glucose. The glucose biosensor sensitivity was influenced by the glucose oxid...

  6. Coupling conducting polymers and mediated electrochemical responses for the detection of Listeria

    International Nuclear Information System (INIS)

    Different signal generation techniques were investigated for the development of a biosensor for Listeria monocytogenes. Conventional amperometry at an antibody-containing polypyrrole film electrode was found to be unsuccessful in detecting levels below 106 cells ml-1. More successful was the coupling of a covalently modified film with the use of electron mediators in a single device. This sensor was capable of reproducibly detecting Listeria at levels of 105 cells ml-1 in 30 min

  7. Wireless Instantaneous Neurotransmitter Concentration Sensing System (WINCS) for Intraoperative Neurochemical Monitoring

    OpenAIRE

    Kimble, Christopher J.; Johnson, David M.; Winter, Bruce A.; Whitlock, Sidney V.; Kressin, Kenneth R.; Horne, April E.; Robinson, Justin C.; Jonathan M. Bledsoe; Susannah J Tye; Chang, Su-Youne; Agnesi, Filippo; Griessenauer, Christoph J.; Covey, Daniel; Shon, Young-Min; Bennet, Kevin E.

    2009-01-01

    The Wireless Instantaneous Neurotransmitter Concentration Sensing System (WINCS) measures extracellular neurotransmitter concentration in vivo and displays the data graphically in nearly real time. WINCS implements two electroanalytical methods, fast-scan cyclic voltammetry (FSCV) and fixed-potential amperometry (FPA), to measure neurotransmitter concentrations at an electrochemical sensor, typically a carbon-fiber microelectrode. WINCS comprises a battery-powered patient module and a custom ...

  8. Voltammetric determination of melatonin using a graphene-based sensor in pharmaceutical products

    OpenAIRE

    Apetrei IM; Apetrei C

    2016-01-01

    Irina Mirela Apetrei,1 Constantin Apetrei2 1Department of Pharmaceutical Sciences, Faculty of Medicine and Pharmacy, 2Department of Chemistry, Physics and Environment, Faculty of Sciences and Environment, “Dunarea de Jos” University of Galati, Galati, Romania Abstract: Melatonin can be sensitively detected in pharmaceuticals by cyclic voltammetry and fixed-potential amperometry using a graphene-based sensor. The sensor characterization of cyclic voltammetry cons...

  9. Spontaneous Water Oxidation at Hematite (α-Fe_2O_3) Crystal Faces

    OpenAIRE

    Chatman, S.; Zarzycki, P.; Rosso, K. M.

    2015-01-01

    Hematite (α-Fe_2O_3) persists as a promising candidate for photoelectrochemical water splitting, but a slow oxygen evolution reaction (OER) at its surfaces remains a limitation. Here we extend a series of studies that examine pH-dependent surface potentials and electron-transfer properties of effectively perfect low-index crystal faces of hematite in contact with simple electrolyte. Zero-resistance amperometry (ZRA) was performed in a two electrode configuration to quantify spontaneous dark c...

  10. Critical role of peripheral drug actions in experience-dependent changes in nucleus accumbens glutamate release induced by intravenous cocaine

    OpenAIRE

    Wakabayashi, Ken T.; Kiyatkin, Eugene A

    2013-01-01

    Recent studies reveal that cocaine experience results in persistent neuroadaptive changes within glutamate (Glu) synapses in brain areas associated with drug reward. However, it remains unclear whether cocaine affects Glu release in drug-naive animals and how it is altered by drug experience. By using high-speed amperometry with enzyme-based and enzyme-free biosensors in freely moving rats, we show that an initial intravenous cocaine injection at a low self-administering dose (1 mg/kg) induce...

  11. Central and peripheral contributions to dynamic changes in nucleus accumbens glucose induced by intravenous cocaine

    OpenAIRE

    Wakabayashi, Ken T.; Kiyatkin, Eugene A

    2015-01-01

    The pattern of neural, physiological and behavioral effects induced by cocaine is consistent with metabolic neural activation, yet direct attempts to evaluate central metabolic effects of this drug have produced controversial results. Here, we used enzyme-based glucose sensors coupled with high-speed amperometry in freely moving rats to examine how intravenous cocaine at a behaviorally active dose affects extracellular glucose levels in the nucleus accumbens (NAc), a critical structure within...

  12. Simultaneous capacitance and amperometric measurements of exocytosis: a comparison.

    OpenAIRE

    Oberhauser, A F; Robinson, I M; Fernandez, J. M.

    1996-01-01

    We measured the exocytotic response induced by flash photolysis of caged compounds in isolated mast cells and chromaffin cells. Vesicle fusion was measured by monitoring the cell membrane capacitance. The release of vesicular contents was followed by amperometry. In response to a GTP gamma S stimulus we found that the time integral of the amperometric current could be superimposed on the capacitance trace. This shows that the integrated amperometric signal provides an alternative method of me...

  13. Electrochemical Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Gang; Lin, Yuehe

    2008-07-20

    Sensitive and selective detection techniques are of crucial importance for capillary electrophoresis (CE), microfluidic chips, and other microfluidic systems. Electrochemical detectors have attracted considerable interest for microfluidic systems with features that include high sensitivity, inherent miniaturization of both the detection and control instrumentation, low cost and power demands, and high compatibility with microfabrication technology. The commonly used electrochemical detectors can be classified into three general modes: conductimetry, potentiometry, and amperometry.

  14. Conducting gramicidin channel activity in phospholipid monolayers.

    OpenAIRE

    A. Nelson

    2001-01-01

    Potential step amperometry (chronoamperometry) of the Tl(I)/Tl(Hg) electrochemical reduction process has been used to investigate the underlying mechanisms of gramicidin activity in phospholipid monolayers. The experiments were carried out at gramicidin-modified dioleoyl phosphatidylcholine (DOPC)-coated electrodes. Application of a potential step to the coated electrode system results in a current transient that can be divided into two regions. An initial exponential decay of current corresp...

  15. Membrane Bending Energy and Fusion Pore Kinetics in Ca2+-Triggered Exocytosis

    OpenAIRE

    Zhang, Zhen; Jackson, Meyer B.

    2010-01-01

    A fusion pore composed of lipid is an obligatory kinetic intermediate of membrane fusion, and its formation requires energy to bend membranes into highly curved shapes. The energetics of such deformations in viral fusion is well established, but the role of membrane bending in Ca2+-triggered exocytosis remains largely untested. Amperometry recording showed that during exocytosis in chromaffin and PC12 cells, fusion pores formed by smaller vesicles dilated more rapidly than fusion pores formed...

  16. Polymer electrolytes based on aromatic lithium sulfonyl-imide compounds; Electrolytes polymeres a base de sulfonylimidures de lithium aromatiques

    Energy Technology Data Exchange (ETDEWEB)

    Reibel, L.; Bayoudh, S. [Centre National de la Recherche Scientifique (CNRS), 67 - Strasbourg (France). Institut Charles Sadron; Baudry, P. [Electricite de France, 77 - Moret sur Loing (France). Direction des Etudes et Recherches; Majastre, H. [Bollore Technologies, 29 - Quimper (France); Herlem, G. [UFR de Sciences et Techniques, L.E.S., 25 - Besancon (France)

    1996-12-31

    This paper presents ionic conductivity results obtained with polymer electrolytes and also with propylene carbonate solutions. The domain of electrochemical activity of this salt has been determined using cycle volt-amperometry in propylene carbonate. Preliminary experiments on the stability of the polymer electrolyte with respect to the lithium electrode have been carried out for a possible subsequent use in lithium batteries. (J.S.) 4 refs.

  17. Recent developments in detection methods for microfabricated analytical devices.

    Science.gov (United States)

    Schwarz, M A; Hauser, P C

    2001-09-01

    Sensitive detection in microfluidic analytical devices is a challenge because of the extremely small detection volumes available. Considerable efforts have been made lately to further address this aspect and to investigate techniques other than fluorescence. Among the newly introduced techniques are the optical methods of chemiluminescence, refraction and thermooptics, as well as the electrochemical methods of amperometry, conductimetry and potentiometry. Developments are also in progress to create miniaturized plasma-emission spectrometers and sensitive detectors for gas-chromatographic separations.

  18. A novel bi-enzyme electrochemical biosensor for selective and sensitive determination of methyl salicylate.

    Science.gov (United States)

    Fang, Yi; Umasankar, Yogeswaran; Ramasamy, Ramaraja P

    2016-07-15

    An amperometric sensor based on a bi-enzyme modified electrode was fabricated to detect methyl salicylate, a volatile organic compound released by pathogen-infected plants via systemic response. The detection is based on cascadic conversion reactions that result in an amperometric electrochemical signal. The bi-enzyme electrode is made of alcohol oxidase and horseradish peroxidase enzymes immobilized on to a carbon nanotube matrix through a molecular tethering method. Methyl salicylate undergoes hydrolysis to form methanol, which is consumed by alcohol oxidase to form formaldehyde while simultaneously reducing oxygen to hydrogen peroxide. The hydrogen peroxide will be further reduced to water by horseradish peroxidase, which results in an amperometric signal via direct electron transfer. The bi-enzyme biosensor was evaluated by cyclic voltammetry and constant potential amperometry using hydrolyzed methyl salicylate as the analyte. The sensitivity of the bi-enzyme biosensor as determined by cyclic voltammetry and constant potential amperometry were 112.37 and 282.82μAcm(-2)mM(-1) respectively, and the corresponding limits of detection were 22.95 and 0.98μM respectively. Constant potential amperometry was also used to evaluate durability, repeatability and interference from other compounds. Wintergreen oil was used for real sample study to establish the application of the bi-enzyme sensor for selective determination of plant pathogen infections. PMID:26918616

  19. Separation of Dopamine and Epinephrine by a Novel Electrophoresis Technique with Nafion Membrane as Separation Column

    Institute of Scientific and Technical Information of China (English)

    Fang Cheng; Wu Bingliang; Zhang Wu-ming; Zhou Xing-gao

    2004-01-01

    A novel electrophoresis technique, in which a strip of perflurosulfonic-acid (Nafion 117) membrane was used to replace the conventional separation column and liquid buffer solution within, was developed and employed to separate the mixture of dopamine and epinephrine under a low separation voltage of 100 V with quadruple pulses amperometry detection. It was showed that the so-called Nafion membrane electrophoresis could be one of very simple and easy method and has the potentiality to be used to separate and analyze some small organic biologic molecules.

  20. Characterization of poly(3,4-ethylenedioxythiophene):tosylate conductive polymer microelectrodes for transmitter detection

    DEFF Research Database (Denmark)

    Larsen, Simon T.; Vreeland, Richard F.; Heien, Michael L.;

    2012-01-01

    In this paper we investigate the physical and electrochemical properties of micropatterned poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:tosylate) microelectrodes for neurochemical detection. PEDOT:tosylate is a promising conductive polymer electrode material for chip-based bioanalytical...... applications such as capillary electrophoresis, high-performance liquid chromatography, and constant potential amperometry at living cells. Band electrodes with widths down to 3 μm were fabricated on polymer substrates using UV lithographic methods. The electrodes are electrochemically stable in a range...

  1. Fabrication of functionalized carbon nanotube buckypaper electrodes for application in glucose biosensors.

    Science.gov (United States)

    Papa, Henry; Gaillard, Melissa; Gonzalez, Leon; Chatterjee, Jhunu

    2014-12-01

    A highly sensitive glucose detection method was developed using functionalized carbon nanotube buckypaper as a free standing electrode in an electrochemical biosensor. Glucose oxidase was immobilized onto various buckypaper samples in order to oxidize glucose resulting in a measureable current/voltage signal output of the biosensor. Cyclic voltammetry (CV) and amperometry were utilized to determine the sensitivity of these buckypaper electrodes. Sensors of three different types of buckypaper were prepared and compared. These modified buckypaper electrode-based sensors showed much higher sensitivity to glucose compared to other electrochemical glucose sensors. PMID:25587433

  2. Biosensors for hepatitis B virus detection.

    Science.gov (United States)

    Yao, Chun-Yan; Fu, Wei-Ling

    2014-09-21

    A biosensor is an analytical device used for the detection of analytes, which combines a biological component with a physicochemical detector. Recently, an increasing number of biosensors have been used in clinical research, for example, the blood glucose biosensor. This review focuses on the current state of biosensor research with respect to efficient, specific and rapid detection of hepatitis B virus (HBV). The biosensors developed based on different techniques, including optical methods (e.g., surface plasmon resonance), acoustic wave technologies (e.g., quartz crystal microbalance), electrochemistry (amperometry, voltammetry and impedance) and novel nanotechnology, are also discussed. PMID:25253948

  3. A new approach of the understanding of sulfur dioxide reduction in non-aqueous solvent; Une nouvelle approche de la comprehension de la reduction du dioxyde de soufre en solvant non aqueux

    Energy Technology Data Exchange (ETDEWEB)

    Potteau, E.; Levillain, E.; Lelieur, J.P. [Laboratoire de Spectrochimie Infrarouge et Raman (LASIR, UPR 2631 CNRS) Haute Etudes Industrielles (HEI), 59 - Lille (France)

    1996-12-31

    The study of SO{sub 2} reduction in non-aqueous solvent can help to understand the functioning of Li/SO{sub 2} batteries and to find a simpler way for the synthesis of Li{sub 2}S{sub 2}O{sub 4} dithionite. This paper presents the results of electrochemical studies (cycle volt-amperometry in semi-infinite and thin film diffusion conditions, visible spectro-electrochemistry) and spectroscopic studies (UV, visible and RPE) performed on SO{sub 2} solutions. A mechanism of SO{sub 2} reduction is proposed and discussed. (J.S.) 18 refs.

  4. Electrochemical sensing of biomarker for diagnostics of bacteria-specific infections

    DEFF Research Database (Denmark)

    Al Atraktchi, Fatima Al-Zahraa; Johansen, Helle Krogh; Molin, Søren;

    2016-01-01

    a direct, selective and rapid detection technique of pyocyanin. Materials & methods: Pyocyanin was detected by amperometry at a relatively high potential where the pyocyanin signal was unaffected by background contributions. Results & conclusion: Pyocyanin was detected at concentrations down to 125 n......M in a 50 μM mixture of interfering compounds with a reproducibility of r2 = 0.999 (n = 5) within 200 s. The results document a step toward a point-of-care technique for diagnosis of P. aeruginosa infections....

  5. [Application of iodine metabolism analysis methods in thyroid diseases].

    Science.gov (United States)

    Han, Jian-hua; Qiu, Ling

    2013-08-01

    The main physiological role of iodine in the body is to synthesize thyroid hormone. Both iodine deficiency and iodine excess can lead to severe thyroid diseases. While its role in thyroid diseases has increasingly been recognized, few relevant platforms and techniques for iodine detection have been available in China. This paper summarizes the advantages and disadvantages of currently iodine detection methods including direct titration, arsenic cerium catalytic spectrophotometry, chromatography with pulsed amperometry, colorimetry based on automatic biochemistry, inductively coupled plasma mass spectrometry, so as to optimize the iodine nutrition for patients with thyroid diseases. PMID:23987480

  6. Acetylcholinesterase Immobilized on Magnetic Beads for Pesticides Detection: Application to Olive Oil Analysis

    Directory of Open Access Journals (Sweden)

    Ihya Ait-Ichou

    2012-06-01

    Full Text Available This work presents the development of bioassays and biosensors for the detection of insecticides widely used in the treatment of olive trees. The systems are based on the covalent immobilisation of acetylcholinesterase on magnetic microbeads using either colorimetry or amperometry as detection technique. The magnetic beads were immobilised on screen-printed electrodes or microtitration plates and tested using standard solutions and real samples. The developed devices showed good analytical performances with limits of detection much lower than the maximum residue limit tolerated by international regulations, as well as a good reproducibility and stability.

  7. Interference-Free Electrochemical Detection of Nanomolar Dopamine Using Doped Polypyrrole and Silver Nanoparticles

    OpenAIRE

    Saha, Suparna; Sarkar, Priyabrata; Turner, Anthony

    2014-01-01

    This paper presents a new approach to detect dopamine in nanomolar range using an electrochemical sensor utilizing a composite made of chitosan-stabilized silver nanoparticles and p-toluene sulfonic acid-doped ultrathin polypyrrole film. Studies included cyclic voltammogram, amperometry, differential pulse voltammetry and also investigation by electrochemical impedance spectroscopy. A detection limit of 0.58 nM was achieved in the linear range 1 x 10(-9) M to 1.2 x 10(-7) M. High sensitivity ...

  8. Fabrication of Functionalized Carbon Nanotube Buckypaper Electrodes for Application in Glucose Biosensors

    Directory of Open Access Journals (Sweden)

    Henry Papa

    2014-11-01

    Full Text Available A highly sensitive glucose detection method was developed using functionalized carbon nanotube buckypaper as a free standing electrode in an electrochemical biosensor. Glucose oxidase was immobilized onto various buckypaper samples in order to oxidize glucose resulting in a measureable current/voltage signal output of the biosensor. Cyclic voltammetry (CV and amperometry were utilized to determine the sensitivity of these buckypaper electrodes. Sensors of three different types of buckypaper were prepared and compared. These modified buckypaper electrode-based sensors showed much higher sensitivity to glucose compared to other electrochemical glucose sensors.

  9. Impedimetric and amperometric bifunctional glucose biosensor based on hybrid organic-inorganic thin films.

    Science.gov (United States)

    Wang, Huihui; Ohnuki, Hitoshi; Endo, Hideaki; Izumi, Mitsuru

    2015-02-01

    A novel glucose biosensor with an immobilized mediator was studied using electrochemical impedance spectroscopy (EIS) and amperometry measurements. The biosensor has a characteristic ultrathin form and is composed of a self-assembled monolayer anchoring glucose oxidase (GOx) covered with Langmuir-Blodgett (LB) films of Prussian blue (PB). The immobilized PB in the LB films acts as a mediator and enables the biosensor to work under a low potential (0.0V vs. Ag/AgCl). In the EIS measurements, a dramatic decrease in charge transfer resistance (Rct) was observed with sequential addition of glucose, which can be attributed to enzymatic activity. The linearity of the biosensor response was observed by the variation of the sensor response (1/Rct) as a function of glucose concentration in the range 0 to 25mM. The sensor also showed linear amperometric response below 130mM glucose. The organic-inorganic system of GOx and PB nanoclusters demonstrated bifunctional sensing action, both amperometry and EIS modes, as well as long sensing stability for 4 days. PMID:25014167

  10. EDTA assisted synthesis of hydroxyapatite nanoparticles for electrochemical sensing of uric acid

    International Nuclear Information System (INIS)

    Hydroxyapatite nanoparticles have been synthesized using EDTA as organic modifier by a simple microwave irradiation method and its application for the selective determination of uric acid (UA) has been demonstrated. Electrochemical behavior of uric acid at HA nanoparticle modified glassy carbon electrode (E-HA/GCE) has been investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), linear sweep voltammetry (LSV) and amperometry. The E-HA modified electrode exhibits efficient electrochemical activity towards uric acid sensing without requiring enzyme or electron mediator. Amperometry studies revealed that the fabricated electrode has excellent sensitivity for uric acid with the lowest detection limit of 142 nM over a wide concentration range from 1 × 10−7 to 3 × 10−5 M. Moreover, the studied E-HA modified GC electrode exhibits a good reproducibility and long-term stability and an admirable selectivity towards the determination of UA even in the presence of potential interferents. The analytical performance of this sensor was evaluated for the detection of uric acid in human urine and blood serum samples. - Highlights: • EDTA- hydroxyapatite (HA) nanoparticles have been synthesized by microwave irradiation method. • A novel amperometric Uric Acid biosensor has been fabricated using E-HA/GCE. • The fabricated sensor exhibits a wide linear range, good stability and high reproducibility. • The sensor was applied for the detection of UA in human blood serum and urine

  11. Recent developments in cyanide detection: A review

    Energy Technology Data Exchange (ETDEWEB)

    Ma Jian [Department of Chemistry and Biochemistry, University of Texas, 700 Planetarium Place, Arlington, TX 76019-0065 (United States); Dasgupta, Purnendu K., E-mail: Dasgupta@uta.edu [Department of Chemistry and Biochemistry, University of Texas, 700 Planetarium Place, Arlington, TX 76019-0065 (United States)

    2010-07-19

    The extreme toxicity of cyanide and environmental concerns from its continued industrial use continue to generate interest in facile and sensitive methods for cyanide detection. In recent years, there is also additional recognition of HCN toxicity from smoke inhalation and potential use of cyanide as a weapon of terrorism. This review summarizes the literature since 2005 on cyanide measurement in different matrices ranging from drinking water and wastewater, to cigarette smoke and exhaled breath to biological fluids like blood, urine and saliva. The dramatic increase in the number of publications on cyanide measurement is indicative of the great interest in this field not only from analytical chemists, but also researchers from diverse environmental, medical, forensic and clinical arena. The recent methods cover both established and emerging analytical disciplines and include naked eye visual detection, spectrophotometry/colorimetry, capillary electrophoresis with optical absorbance detection, fluorometry, chemiluminescence, near-infrared cavity ring down spectroscopy, atomic absorption spectrometry, electrochemical methods (potentiometry/amperometry/ion chromatography-pulsed amperometry), mass spectrometry (selected ion flow tube mass spectrometry, electrospray ionization mass spectrometry, gas chromatography-mass spectrometry), gas chromatography (nitrogen phosphorus detector, electron capture detector) and quartz crystal mass monitors.

  12. Highly sensitive sensor for picomolar detection of insulin at physiological pH, using GC electrode modified with guanine and electrodeposited nickel oxide nanoparticles.

    Science.gov (United States)

    Salimi, Abdollah; Noorbakhash, Abdollah; Sharifi, Ensieh; Semnani, Abolfazl

    2008-12-01

    The electrochemical behavior of insulin at glassy carbon (GC) electrode modified with nickel oxide nanoparticles and guanine was investigated. Cyclic voltammetry technique has been used for electrodeposition of nickel oxide nanoparticles (NiOx) and immobilization of guanine on the surface GC electrode. In comparison to glassy carbon electrode modified with nickel oxide nanoparticles and bare GC electrode modified with adsorbed guanine, the guanine/nickel oxide nanoparticles/modified GC electrode exhibited excellent catalytic activity for the oxidation of insulin in physiological pH solutions at reduced overpotential. The modified electrode was applied for insulin detection using cyclic voltammetry or hydrodynamic amperometry techniques. It was found that the calibration curve was linear up to 4muM with a detection limit of 22pM and sensitivity of 100.9pA/pM under the optimized condition for hydrodynamic amperometry using a rotating disk modified electrode. In comparison to other electrochemical insulin sensors, this sensor shows many advantages such as simple preparation method without using any special electron transfer mediator or specific reagent, high sensitivity, excellent catalytic activity at physiological pH values, short response time, long-term stability and remarkable antifouling property toward insulin and its oxidation product. Additionally, it is promising for the monitoring of insulin in chromatographic effluents.

  13. Fabrication of an Amperometric Flow-Injection Microfluidic Biosensor Based on Laccase for In Situ Determination of Phenolic Compounds

    Directory of Open Access Journals (Sweden)

    Juan C. Gonzalez-Rivera

    2015-01-01

    Full Text Available We aim to develop an in situ microfluidic biosensor based on laccase from Trametes pubescens with flow-injection and amperometry as the transducer method. The enzyme was directly immobilized by potential step chronoamperometry, and the immobilization was studied using cyclic voltammetry and electrochemical impedance spectroscopy. The electrode response by amperometry was probed using ABTS and syringaldazine. A shift of interfacial electron transfer resistance and the electron transfer rate constant from 18.1 kΩ to 3.9 MΩ and 4.6 × 10−2 cm s−1 to 2.1 × 10−4 cm s−1, respectively, evidenced that laccase was immobilized on the electrode by the proposed method. We established the optimum operating conditions of temperature (55°C, pH (4.5, injection flow rate (200 µL min−1, and applied potential (0.4 V. Finally, the microfluidic biosensor showed better lower limit of detection (0.149 µM and sensitivity (0.2341 nA µM−1 for ABTS than previous laccase-based biosensors and the in situ operation capacity.

  14. Simultaneous/Selective Detection of Dopamine and Ascorbic Acid at Synthetic Zeolite-Modified/Graphite-Epoxy Composite Macro/Quasi-Microelectrodes

    Directory of Open Access Journals (Sweden)

    Rodica Pode

    2013-06-01

    Full Text Available The present paper aims to miniaturize a graphite-epoxy and synthetic zeolite-modified graphite-epoxy composite macroelectrode as a quasi-microelectrode aiming in vitro and also, envisaging in vivo simultaneous electrochemical detection of dopamine (DA and ascorbic acid (AA neurotransmitters, or DA detection in the presence of AA. The electrochemical behavior and the response of the designed materials to the presence of dopamine and ascorbic acid without any protective membranes were studied by cyclic voltammetry and constant-potential amperometry techniques. The catalytic effect towards dopamine detection was proved for the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode, allowing increasing the sensitivity and selectivity for this analyte detection, besides a possible electrostatic attraction between dopamine cation and the negative surface of the synthetic zeolite and electrostatic repulsion with ascorbic acid anion. Also, the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode gave the best electroanalytical parameters for dopamine detection using constant-potential amperometry, the most useful technique for practical applications.

  15. EDTA assisted synthesis of hydroxyapatite nanoparticles for electrochemical sensing of uric acid

    Energy Technology Data Exchange (ETDEWEB)

    Kanchana, P.; Sekar, C., E-mail: Sekar2025@gmail.com

    2014-09-01

    Hydroxyapatite nanoparticles have been synthesized using EDTA as organic modifier by a simple microwave irradiation method and its application for the selective determination of uric acid (UA) has been demonstrated. Electrochemical behavior of uric acid at HA nanoparticle modified glassy carbon electrode (E-HA/GCE) has been investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), linear sweep voltammetry (LSV) and amperometry. The E-HA modified electrode exhibits efficient electrochemical activity towards uric acid sensing without requiring enzyme or electron mediator. Amperometry studies revealed that the fabricated electrode has excellent sensitivity for uric acid with the lowest detection limit of 142 nM over a wide concentration range from 1 × 10{sup −7} to 3 × 10{sup −5} M. Moreover, the studied E-HA modified GC electrode exhibits a good reproducibility and long-term stability and an admirable selectivity towards the determination of UA even in the presence of potential interferents. The analytical performance of this sensor was evaluated for the detection of uric acid in human urine and blood serum samples. - Highlights: • EDTA- hydroxyapatite (HA) nanoparticles have been synthesized by microwave irradiation method. • A novel amperometric Uric Acid biosensor has been fabricated using E-HA/GCE. • The fabricated sensor exhibits a wide linear range, good stability and high reproducibility. • The sensor was applied for the detection of UA in human blood serum and urine.

  16. Amperometric detection of Sudan I in red chili powder samples using Ag nanoparticles decorated graphene oxide modified glassy carbon electrode.

    Science.gov (United States)

    Prabakaran, E; Pandian, K

    2015-01-01

    A simple and sensitive electrochemical method was developed to determine the concentration of Sudan I in chili powder based on silver nanoparticles decorated graphene oxide modified glassy carbon electrode (AgNPs@GO/GCE). The voltammetry behaviour of Sudan I on modified GCE was investigated in phosphate buffer medium (PBS) with various pH ranges and the electron transfer properties were studied. It is found that the AgNPs@GO/GCE can catalyse the reduction of azo group, -N=N- followed by electrochemical oxidation of (-)OH group present in Sudan I dye molecule. Quantitative detection of Sudan I present in food products was carried out by amperometry method in which reduction potential was fixed at -0.77 V vs. Ag/AgCl. The amperometry method showed an excellent performance with a sensitivity of 6.83 μA mM(-1) and a detection limit of 11.4 × 10(-7)ML(-1). A linear calibration graph was constructed in the ranging 3.90 × 10(-6) to 3.19 × 10(-5)ML(-1). The method was successfully applied for the determination of Sudan I in red chili powder samples.

  17. Amperometric Detection of Bacillus anthracis Spores: A Portable, Low-Cost Approach to the ELISA

    Directory of Open Access Journals (Sweden)

    Gabriel D. Peckham

    2013-01-01

    Full Text Available Antibody-based detection assays are generally robust, a desirable characteristic for in-the-field use. However, to quantify the colorimetric or fluorescent signal, these assays require expensive and fragile instruments which are ill-suited to in-the-field use. Lateral flow devices (LFDs circumvent these barriers to portability but suffer from poor sensitivity and subjective interpretation. Here, an antibody-based method for detecting Bacillus anthracis spores via amperometric signal generation is compared to ELISA and LFDs. This amperometric immunoassay uses antibody conjugated to magnetic beads and glucose oxidase (GOX along with the electron mediator 2, 6-dichlorophenolindophenol (DCPIP for production of a measurable current from a 0.4 V bias voltage. With similar sensitivity to ELISA, the assay can be completed in about 75 minutes while being completely powered and operated from a laptop computer. Immunoassay amperometry holds promise for bringing low-cost, quantitative detection of hazardous agents to the field.

  18. Carbon Nanotubes Based Glucose Needle-type Biosensor

    Directory of Open Access Journals (Sweden)

    Hong Li

    2008-03-01

    Full Text Available A novel needle-type biosensor based on carbon nanotubes is reported. Thebiosensor was prepared by packing a mixture of multi-wall carbon nanotubes (MWCNTs,graphite powder and glucose oxidase (Gox freeze-dried powder into a glass capillary of 0.5mm inner diameter. The resulting amperometric biosensor was characterizedelectrochemically using amperometry in the presence of hydrogen peroxide and in thepresence of glucose. The glucose biosensor sensitivity was influenced by the glucoseoxidase concentration within the MWCNTs mixture. The optimized glucose needle-typebiosensor displayed better sensitivity and stability, and a detected range of up to 20 mM.Based on its favorable stability, the needle biosensor was first time used in real-timemonitoring system as a kind of online glucose detector. The decay of current response isless than 10% after 24-hour continuous observation.

  19. A glucose oxidase sensor based on screen-printed carbon electrodes modified by polypyrrole.

    Science.gov (United States)

    Xu, Hui; Li, Guang; Wu, Jieying; Wang, You; Liu, Jun

    2005-01-01

    A disposable amperometric biosensor for detecting blood glucose has been developed. The sensor is based on a screen-printed electrode prepared by electrochemical polymerization of pyrrole with glucose oxidase (GOD) and LiClO4 dopants. In citric acid buffer (pH5.0), GOD with negative charges is immobilized within electropositive polypyrrole matrices onto a carbon electrode surface. Afterward, the electron transfer mediator, potassium ferricyanide is immobilized by adsorption. Experimentally the compositions of pyrrole, LiClO4 and potassium ferricyanide are optimized. Amperometry is used for the determination of glucose concentration. Four microliters of glucose solution is needed for one test, and the response time of the sensor is 70s. The amperometric response of the enzyme electrode is linear in the range of 1-30 mM. PMID:17282595

  20. Amperometric Noise at Thin Film Band Electrodes

    DEFF Research Database (Denmark)

    Larsen, Simon T.; Heien, Michael L.; Taboryski, Rafael

    2012-01-01

    polymers and measured the current noise in physiological buffer solution for a wide range of different electrode areas. The noise measurements could be modeled by an analytical expression, representing the electrochemical cell as a resistor and capacitor in series. The studies revealed three domains......; for electrodes with low capacitance, the amplifier noise dominated, for electrodes with large capacitances, the noise from the resistance of the electrochemical cell was dominant, while in the intermediate region, the current noise scaled with electrode capacitance. The experimental results and the model......Background current noise is often a significant limitation when using constant-potential amperometry for biosensor application such as amperometric recordings of transmitter release from single cells through exocytosis. In this paper, we fabricated thin-film electrodes of gold and conductive...

  1. Highly sensitive and selective electrochemical dopamine sensing properties of multilayer graphene nanobelts

    Science.gov (United States)

    Karthick Kannan, Padmanathan; Moshkalev, Stanislav A.; Sekhar Rout, Chandra

    2016-02-01

    In the present study, we report the electrochemical sensing property of multi-layer graphene nanobelts (GNBs) towards dopamine (DA). GNBs are synthesized from natural graphite and characterized by using techniques like field-emission scanning electron microscopy, atomic force microscopy and Raman spectroscopy. An electrochemical sensor based on GNBs is developed for the detection of DA. From the cyclic voltammetry and amperometry studies, it is found that GNBs possess excellent electrocatalytic activity towards DA molecules. The developed DA sensor showed a sensitivity value of 0.95 μA μM-1 cm-2 with a linear range of 2 μM to 0.2 mM. The interference data exhibited that GNB is highly selective to DA even in the presence of common interfering species like ascorbic acid, uric acid, glucose and lactic acid.

  2. Toxicity assessment using different bioassays and microbial biosensors.

    Science.gov (United States)

    Hassan, Sedky H A; Van Ginkel, Steven W; Hussein, Mohamed A M; Abskharon, Romany; Oh, Sang-Eun

    2016-01-01

    Toxicity assessment of water streams, wastewater, and contaminated sediments, is a very important part of environmental pollution monitoring. Evaluation of biological effects using a rapid, sensitive and cost effective method can indicate specific information on ecotoxicity assessment. Recently, different biological assays for toxicity assessment based on higher and lower organisms such as fish, invertebrates, plants and algal cells, and microbial bioassays have been used. This review focuses on microbial biosensors as an analytical device for environmental, food, and biomedical applications. Different techniques which are commonly used in microbial biosensing include amperometry, potentiometry, conductometry, voltammetry, microbial fuel cells, fluorescence, bioluminescence, and colorimetry. Examples of the use of different microbial biosensors in assessing a variety of environments are summarized. PMID:27071051

  3. Electrochemical Probing of in Vivo 5-Hydroxymethyl Furfural Reduction in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Kostesha, Natalie; Almeida, J.R.M.; Heiskanen, Arto;

    2009-01-01

    In this work, mediated amperometry was used to evaluate whether differences in intracellular nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) level could be observed between a genetically modified Saccharomyces cerevisiae strain, engineered for NADPH dependent 5-hydroxymethyl-2-furaldehyde...... amperometric signal during real-time monitoring of the concentration dependent HMF reduction in living cells could be translated into the cellular enzyme kinetic parameters: K-M,cell(app), V-MAX, k(cat,cell), and k(cat,cell)/K-M,cell(app). The results indicated that the overexpression of the ADH6 gene gave...... a 68% decrease in K-M,cell(app), and 42% increase in V-MAX, resulting in a 4-fold increase in k(cat,cell)/K-M,cell(app). These results demonstrate that the mediated amperometric method is useful for monitoring the short-term dynamics of NAD(P)H variations and determining cellular enzyme kinetic...

  4. Potentiostatic controlled nucleation and growth modes of electrodeposited cobalt thin films on n-Si(1 1 1)

    Science.gov (United States)

    Mechehoud, Fayçal; Khelil, Abdelbacet; Eddine Hakiki, Nour; Bubendorff, Jean-Luc

    2016-08-01

    The nucleation and growth of Co electrodeposits on n-Si(1 1 1) substrate have been investigated as a function of the applied potential in a large potential range using electrochemical techniques (voltammetry and chrono-amperometry) and surface imaging by atomic force microscopy (AFM). The surface preparation of the sample is crucial and we achieve a controlled n-Si(1 1 1) surface with mono-atomic steps and flat terraces. Using Scharifker-Hills models for fitting the current-time transients, we show that a transition from an instantaneous nucleation process to a progressive one occurs when the overpotential increases. A good agreement between the nucleation and growth parameters extracted from the models and the AFM data's is observed. The growth is of the Volmer-Weber type with a roughness and a spatial extension in the substrate plane of the deposited islands that increase with thickness.

  5. Silence of Synaptotagmin VII inhibits release of dense core vesicles in PC12 cells

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Synaptotagmin VII (Syt VII), which has a higher Ca2+ affinity and slower disassembly kinetics with lipid than Syt I and Syt IX, was regarded as being uninvolved in synaptic vesicle (SV) exocytosis but instead possibly as a calcium sensor for the slower kinetic phase of dense core vesicles (DCVs) release. By using high temporal resolution capacitance and amperometry measurements, it was demonstrated that the knockdown of endogenous Syt VII attenuated the fusion of DCV with the plasma membrane, reduced the amplitude of the exocytotic burst of the Ca2+-triggered DCV release without affecting the slope of the sustained component, and blocked the fusion pore expansion. This suggests that Syt VII is the Ca2+ sensor of DCV fusion machinery and is an essential factor for the establishment and maintenance of the pool size of releasable DCVs in PC12 cells.

  6. Nanoporous Ag template from partially sintered Ag–Zn compact by dezincification

    Indian Academy of Sciences (India)

    M Mandal; A P Moon; S Sangal; K Mondal

    2014-10-01

    A novel approach is followed to successfully fabricate nanoporous thin Ag template using partial sintering of elemental Ag and Zn (both have 99.9% purity) and subsequent dezincification. The starting materials for dezincification are partially sintered Ag–Zn aggregates (2.5, 5 and 10 wt% Zn). Partial sintering is done in order to achieve only interfacial bonding with the aim to maintain maximum potential difference between Ag and Zn particles during dezincification process in 1 N HCl and 3.5 wt% NaCl solutions. Two different dissolution methods, namely, simple immersion for 45 days and electrochemical way (holding the sample at critical potential), are employed. Electrochemical polarization tests are carried out to determine the critical potential for subsequent chrono-amperometry. X-ray diffraction, optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy are carried out to examine microstructural evolution, size, distribution and nature of pores in sintered aggregate as well as in template.

  7. Pulse electrodeposited nickel-indium tin oxide nanocomposite as an electrocatalyst for non-enzymatic glucose sensing.

    Science.gov (United States)

    Sivasakthi, P; Ramesh Bapu, G N K; Chandrasekaran, Maruthai

    2016-01-01

    Nickel and nickel-ITO nanocomposite on mild steel substrate were prepared by pulse electrodeposition method from nickel sulphamate electrolyte and were examined as electrocatalysts for non-enzymatic glucose sensing. The surface morphology, chemical composition, preferred orientation and oxidation states of the nickel metal ion in the deposits were characterized by SEM, EDAX, XRD and XPS. Electrochemical sensing of glucose was studied by cyclic voltammetry and amperometry. The modified Ni-ITO nanocomposite electrode showed higher electrocatalytic activity for the oxidation of glucose in alkaline medium and exhibited a linear range from 0.02 to 3.00 mM with a limit of detection 3.74 μM at a signal-to-noise ratio of 3. The higher selectivity, longer stability and better reproducibility of this electrode compared to nickel in the sensing of glucose are pointers for exploitation in practical clinical applications.

  8. Electrochemical detection of hydrogen peroxide at a waxed graphite electrode modified with platinum-decorated carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    SHI Qiao-cui; ZENG Wen-fang; ZHU Yunu

    2009-01-01

    Platinum-decorated carbon nanotubes (CNT-Pt) were produced by the chemical reduction method. A novel modified electrode was fabricated by intercalated CNT-Pt in the surface of waxed graphite, which provided excellent electro-catalytic activity and selectivity for both oxidation and reduction of hydrogen peroxide. The current response of the modified electrode for hydrogen peroxide was very rapid and the detection limits in amperometry are 2.5×10-6 mol/L at reduction potential and 4.8×10-6 mol/L at oxidation potential. It was desmonstrated that the electrode with high electro-activity was a suitable basic electrode for preparing enzyme electrode.

  9. Electrochemical Analysis of Neurotransmitters

    Science.gov (United States)

    Bucher, Elizabeth S.; Wightman, R. Mark

    2015-07-01

    Chemical signaling through the release of neurotransmitters into the extracellular space is the primary means of communication between neurons. More than four decades ago, Ralph Adams and his colleagues realized the utility of electrochemical methods for the study of easily oxidizable neurotransmitters, such as dopamine, norepinephrine, and serotonin and their metabolites. Today, electrochemical techniques are frequently coupled to microelectrodes to enable spatially resolved recordings of rapid neurotransmitter dynamics in a variety of biological preparations spanning from single cells to the intact brain of behaving animals. In this review, we provide a basic overview of the principles underlying constant-potential amperometry and fast-scan cyclic voltammetry, the most commonly employed electrochemical techniques, and the general application of these methods to the study of neurotransmission. We thereafter discuss several recent developments in sensor design and experimental methodology that are challenging the current limitations defining the application of electrochemical methods to neurotransmitter measurements.

  10. Determination of inorganic phosphate by electroanalytical methods: a review.

    Science.gov (United States)

    Berchmans, Sheela; Issa, Touma B; Singh, Pritam

    2012-06-01

    Determination of inorganic phosphate is of very high importance in environmental and health care applications. Hence knowledge of suitable analytical techniques available for phosphate sensing for different applications becomes essential. Electrochemical methods for determining inorganic phosphate have several advantages over other common techniques, including detection selectivity, stability and relative environmental insensitivity of electroactive labels. The different electrochemical sensing strategies adopted for the determination of phosphate using selective ionophores are discussed in this review. The various sensing strategies are classified based on the electrochemical detection techniques used viz., potentiometry, voltammetry, amperometry, unconventional electrochemical methods etc., The enzymatic sensing of phosphate coupled with electrochemical detection is also included. Various electroanalytical methods available in the literature are assessed for their merits in terms of selectivity, simplicity, miniaturisation, adaptability and suitability for field measurements.

  11. Aplicações eletroanalíticas com eletrodos de prata confeccionados a partir de CDs graváveis Electroanalytical applications of silver electrodes built from recordable CDs

    Directory of Open Access Journals (Sweden)

    Eduardo M. Richter

    2003-12-01

    Full Text Available This paper presents a new way for the construction of silver electrodes utilizing recordable CDs. The new electrodes were explored for the quantification of chloride (by potentiometry/FIA, cyanide (by amperometry/FIA and for lead analysis (by square wave voltammetry. For the flowing measurements, a digital multimeter, connected to a microcomputer (via RS 232 interface was used to collect directly the potential signal (for Cl- measurements or to take the output signal from a potentiostat (for CN- measurements. The square wave voltammetry analysis was performed in a commercial instrument. The results shown good performance of the new electrodes and the detection limit (s/n = 3 attained for these three analytes were: 0.2, 50, and 200 µg L-1 for Pb2+, Cl-, and CN- respectively.

  12. Voltammetric determination of melatonin using a graphene-based sensor in pharmaceutical products

    Science.gov (United States)

    Apetrei, Irina Mirela; Apetrei, Constantin

    2016-01-01

    Melatonin can be sensitively detected in pharmaceuticals by cyclic voltammetry and fixed-potential amperometry using a graphene-based sensor. The sensor characterization of cyclic voltammetry constantly provides high values of electrode active area and heterogeneous rate constant. In optimal conditions, the sensor was applied for the determination of melatonin in different pharmaceutical samples. The sensitivity to melatonin was 0.0371 A M−1, and the limit of detection was 0.87×10−6 M. The data obtained by using the graphene-based sensor for the detection of melatonin in pharmaceutical products were in good agreement with the data provided by the producer. Since no interferences from the excipients were found, using a separation technique was not necessary. Additionally, the low price, ease of handling, small amount of sample, short time per analysis, and possibility of automation are the important advantages that recommend this methodology for quality control of pharmaceuticals. PMID:27194909

  13. Electroanalysis of tetracycline using nickel-implanted boron-doped diamond thin film electrode applied to flow injection system.

    Science.gov (United States)

    Treetepvijit, Surudee; Chuanuwatanakul, Suchada; Einaga, Yasuaki; Sato, Rika; Chailapakult, Orawon

    2005-05-01

    The electrochemical analysis of tetracycline was investigated using nickel-implanted boron-doped diamond thin film electrode by cyclic voltammetry and amperometry with a flow injection system. Cyclic voltammetry was used to study the electrochemical oxidation of tetracycline. Comparison experiments were carried out using as-deposited boron-doped diamond thin film electrode (BDD). Nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) provided well-resolved oxidation irreversible cyclic voltammograms. The current signals were higher than those obtained using the as-deposited BDD electrode. Results using nickel-implanted boron-doped diamond thin film electrode in flow injection system coupled with amperometric detection are presented. The optimum potential for tetracycline was 1.55 V versus Ag/AgCl. The linear range of 1.0 to 100 microM and the detection limit of 10 nM were obtained. In addition, the application for drug formulation was also investigated.

  14. Silver nanoparticles prepared in presence of ascorbic acid and gelatin, and their electrocatalytic application

    Indian Academy of Sciences (India)

    Fereshteh Chekin; Somayeh Ghasemi

    2014-10-01

    In this paper, we reported a simple and low-cost procedure to synthesize silver nanoparticles (AgNPs) by using ascorbic acid as reducing agent and gelatin as stabilizer. The synthesized AgNPs were characterized by various means such as transmission electron microscope (TEM), powder X-ray diffraction (XRD) and energy-dispersive X-ray (EDX). TEM observations and XRD analysis demonstrated that the size of AgNPs is about 20 nm. Silver nanoparticles modified with carbon-paste electrode (AgNPs–CPE) displayed excellent electrochemical catalytic activities towards hydrogen peroxide (H2O2). The reduction overpotential of H2O2 was decreased significantly compared with those obtained at the bare CPE. The sensor responded linearly to hydrogen peroxide (H2O2) in the concentration of 10–350 M, with detection limit of 5.6 M at 3 using amperometry. The studied sensor exhibited good reproducibility and long-term stability.

  15. Microfluidic perfusion systems for secretion fingerprint analysis of pancreatic islets: applications, challenges and opportunities.

    Science.gov (United States)

    Castiello, F Rafael; Heileman, Khalil; Tabrizian, Maryam

    2016-02-01

    A secretome signature is a heterogeneous profile of secretions present in a single cell type. From the secretome signature a smaller panel of proteins, namely a secretion fingerprint, can be chosen to feasibly monitor specific cellular activity. Based on a thorough appraisal of the literature, this review explores the possibility of defining and using a secretion fingerprint to gauge the functionality of pancreatic islets of Langerhans. It covers the state of the art regarding microfluidic perfusion systems used in pancreatic islet research. Candidate analytical tools to be integrated within microfluidic perfusion systems for dynamic secretory fingerprint monitoring were identified. These analytical tools include patch clamp, amperometry/voltametry, impedance spectroscopy, field effect transistors and surface plasmon resonance. Coupled with these tools, microfluidic devices can ultimately find applications in determining islet quality for transplantation, islet regeneration and drug screening of therapeutic agents for the treatment of diabetes. PMID:26732665

  16. Improvements of tritium enrichment for low level measurement

    International Nuclear Information System (INIS)

    Electrolysis enrichment of tritium water was improved for practical measurement. Hydrogen peroxide in sample water was completely decomposed and the water value was measured exactly by weight. Electric current was determined exactly by calibrated power supply. The value of water vapor was measured exactly using calcium chloride. These made the current balanced with the decomposed water, and gravimetry of enriched water could be replaced by amperometry. Iron cathode, the recovery factor is highest, was used. The recovery factor of tritium enrichment was determined as R = 0.88. The total error for the most simple measurement was 10-16% for the sample which concentration was 0.3-1.0 Bq/kg. (author)

  17. Amperometric homogeneous competitive immunoassay in a perfluorocarbon emulsion oxygen therapeutic (PEOT).

    Science.gov (United States)

    Barlag, Rebecca E; Halsall, H Brian; Heineman, William R

    2013-04-01

    The effect of a perfluorocarbon emulsion oxygen therapeutic (PEOT) on the detection of the drugs theophylline and phenytoin was explored using a commercial enzyme multiplied immunoassay technique (EMIT®). The EMIT technique is based on the enzymatic production of NADH, which is typically detected in serum samples spectrophotometrically. Here, amperometry using the rotating disk electrode on a single drop of solution is demonstrated to detect theophylline and phenytoin in the presence of PEOT. In the study, 2,6-dichloroindophenol (DCIP) added to the immunoassay mixture is reduced by the NADH to DCIPH2. Oxidation of DCIPH2 is monitored electrochemically at +200 mV using a glassy carbon rotating disk electrode. Slopes of amperograms are proportional to the concentration of drug in the immunoassay sample. This technique yields excellent quantitative data in the therapeutic range for both drugs in 2-20% PEOT.

  18. Brain Tissue Oxygen: In Vivo Monitoring with Carbon Paste Electrodes

    Directory of Open Access Journals (Sweden)

    John P. Lowry

    2005-11-01

    Full Text Available In this communication we review selected experiments involving the use ofcarbon paste electrodes (CPEs to monitor and measure brain tissue O2 levels in awakefreely-moving animals. Simultaneous measurements of rCBF were performed using the H2clearance technique. Voltammetric techniques used include both differential pulse (O2 andconstant potential amperometry (rCBF. Mild hypoxia and hyperoxia produced rapidchanges (decrease and increase respectively in the in vivo O2 signal. Neuronal activation(tail pinch and stimulated grooming produced similar increases in both O2 and rCBFindicating that CPE O2 currents provide an index of increases in rCBF when such increasesexceed O2 utilization. Saline injection produced a transient increase in the O2 signal whilechloral hydrate produced slower more long-lasting changes that accompanied the behavioralchanges associated with anaesthesia. Acetazolamide increased O2 levels through an increasein rCBF.

  19. Recent developments in electrochemical detection for microchip capillary electrophoresis.

    Science.gov (United States)

    Vandaveer, Walter R; Pasas-Farmer, Stephanie A; Fischer, David J; Frankenfeld, Celeste N; Lunte, Susan M

    2004-11-01

    Significant progress in the development of miniaturized microfluidic systems has occurred since their inception over a decade ago. This is primarily due to the numerous advantages of microchip analysis, including the ability to analyze minute samples, speed of analysis, reduced cost and waste, and portability. This review focuses on recent developments in integrating electrochemical (EC) detection with microchip capillary electrophoresis (CE). These detection modes include amperometry, conductimetry, and potentiometry. EC detection is ideal for use with microchip CE systems because it can be easily miniaturized with no diminution in analytical performance. Advances in microchip format, electrode material and design, decoupling of the detector from the separation field, and integration of sample preparation, separation, and detection on-chip are discussed. Microchip CEEC applications for enzyme/immunoassays, clinical and environmental assays, as well as the detection of neurotransmitters are also described.

  20. Non-enzymatic electrochemical glucose sensor based on NiMoO4 nanorods

    International Nuclear Information System (INIS)

    A non-enzymatic glucose sensor based on the NiMoO4 nanorods has been fabricated for the first time. The electrocatalytic performance of the NiMoO4 nanorods’ modified electrode toward glucose oxidation was evaluated by cyclic voltammetry and amperometry. The NiMoO4 nanorods’ modified electrode showed a greatly enhanced electrocatalytic property toward glucose oxidation, as well as an excellent anti-interference and a good stability. Impressively, good accuracy and high precision for detecting glucose concentration in human serum samples were obtained. These excellent sensing properties, combined with good reproducibility and low cost, indicate that NiMoO4 nanorods are a promising candidate for non-enzymatic glucose sensors. (paper)

  1. Ketamine Suppresses the Ventral Striatal Response to Reward Anticipation: A Cross-Species Translational Neuroimaging Study.

    Science.gov (United States)

    Francois, Jennifer; Grimm, Oliver; Schwarz, Adam J; Schweiger, Janina; Haller, Leila; Risterucci, Celine; Böhringer, Andreas; Zang, Zhenxiang; Tost, Heike; Gilmour, Gary; Meyer-Lindenberg, Andreas

    2016-04-01

    Convergent evidence implicates regional neural responses to reward anticipation in the pathogenesis of several psychiatric disorders, such as schizophrenia, where blunted ventral striatal responses to positive reward are observed in patients and at-risk populations. In vivo oxygen amperometry measurements in the ventral striatum in awake, behaving rats reveal reward-related tissue oxygen changes that closely parallel blood oxygen level dependent (BOLD) signal changes observed in human functional magnetic resonance imaging (fMRI), suggesting that a cross-species approach targeting this mechanism might be feasible in psychopharmacology. The present study explored modulatory effects of acute, subanaesthetic doses of ketamine-a pharmacological model widely used in psychopharmacological research, both preclinically and clinically-on ventral striatum activity during performance of a reward anticipation task in both species, using fMRI in humans and in vivo oxygen amperometry in rats. In a region-of-interest analysis conducted following a cross-over placebo and ketamine study in human subjects, an attenuated ventral striatal response during reward anticipation was observed following ketamine relative to placebo during performance of a monetary incentive delay task. In rats, a comparable attenuation of ventral striatal signal was found after ketamine challenge, relative to vehicle, in response to a conditioned stimulus that predicted delivery of reward. This study provides the first data in both species demonstrating an attenuating effect of acute ketamine on reward-related ventral striatal (O2) and fMRI signals. These findings may help elucidate a deeper mechanistic understanding of the potential role of ketamine as a model for psychosis, show that cross-species pharmacological experiments targeting reward signaling are feasible, and suggest this phenotype as a promising translational biomarker for the development of novel compounds, assessment of disease status, and

  2. Layer-by-layer self-assembling copper tetrasulfonated phthalocyanine on carbon nanotube modified glassy carbon electrode for electro-oxidation of 2-mercaptoethanol

    Energy Technology Data Exchange (ETDEWEB)

    Shaik, Mahabul, E-mail: mshaik86@gmail.com; Rao, V.K.; Gupta, Manish; Pandey, P.

    2012-12-30

    This paper describes the electrocatalytic activity of layer-by-layer self-assembled copper tetrasulfonated phthalocyanine (CuPcTS) on carbon nanotube (CNT)-modified glassy carbon (GC) electrode. CuPcTS is immobilized on the negatively charged CNT surface by alternatively assembling a cationic poly(diallyldimethylammonium chloride) (PDDA) layer and a CuPcTS layer. UV-vis absorption spectra and electrochemical measurements suggested the successive linear depositions of the bilayers of CuPcTs and PDDA on CNT. The surface morphology was observed using scanning electron microscopy. The viability of this CuPcTS/PDDA/CNT modified GC electrode as a redox mediator for the anodic oxidation and sensitive amperometric determination of 2-mercaptoethanol (2-ME) in alkaline conditions is described. The effect of number of bilayers of CuPcTS/PDDA and pH on electrochemical oxidation of 2-ME was studied. The proposed electrochemical sensor displayed excellent characteristics towards the determination of 2-ME in 0.1 M NaOH; such as low overpotentials (- 0.15 V vs Ag/AgCl), linear concentration range of 3 Multiplication-Sign 10{sup -5} M to 6 Multiplication-Sign 10{sup -3} M, and with a detection limit of 2.5 Multiplication-Sign 10{sup -5} M using simple amperometry. - Highlights: Black-Right-Pointing-Pointer Carbon nanotubes (CNT) were drop-dried on glassy carbon electrode (GCE). Black-Right-Pointing-Pointer Copper tetrasulfonated phthalocyanine (CuPcTS) was deposited on CNT/GCE. Black-Right-Pointing-Pointer Layer-by-layer self-assembling method is used for depositing CuPcTS. Black-Right-Pointing-Pointer Electrocatalytic oxidation of 2-mercaptoethanol (ME) was studied at this electrode Black-Right-Pointing-Pointer The detection limit of ME at modified electrode was 25 {mu}M by amperometry.

  3. Facile hydrothermal growth graphene/ZnO nanocomposite for development of enhanced biosensor.

    Science.gov (United States)

    Low, Sze Shin; Tan, Michelle T T; Loh, Hwei-San; Khiew, Poi Sim; Chiu, Wee Siong

    2016-01-15

    Graphene/zinc oxide nanocomposite was synthesised via a facile, green and efficient approach consisted of novel liquid phase exfoliation and solvothermal growth for sensing application. Highly pristine graphene was synthesised through mild sonication treatment of graphite in a mixture of ethanol and water at an optimum ratio. The X-ray diffractometry (XRD) affirmed the hydrothermal growth of pure zinc oxide nanoparticles from zinc nitrate hexahydrate precursor. The as-prepared graphene/zinc oxide (G/ZnO) nanocomposite was characterised comprehensively to evaluate its morphology, crystallinity, composition and purity. All results clearly indicate that zinc oxide particles were homogenously distributed on graphene sheets, without any severe aggregation. The electrochemical performance of graphene/zinc oxide nanocomposite-modified screen-printed carbon electrode (SPCE) was evaluated using cyclic voltammetry (CV) and amperometry analysis. The resulting electrode exhibited excellent electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2) in a linear range of 1-15 mM with a correlation coefficient of 0.9977. The sensitivity of the graphene/zinc oxide nanocomposite-modified hydrogen peroxide sensor was 3.2580 μAmM(-1) with a limit of detection of 7.4357 μM. An electrochemical DNA sensor platform was then fabricated for the detection of Avian Influenza H5 gene based on graphene/zinc oxide nanocomposite. The results obtained from amperometry study indicate that the graphene/zinc oxide nanocomposite-enhanced electrochemical DNA biosensor is significantly more sensitive (P < 0.05) and efficient than the conventional agarose gel electrophoresis. PMID:26709306

  4. Facile hydrothermal growth graphene/ZnO nanocomposite for development of enhanced biosensor.

    Science.gov (United States)

    Low, Sze Shin; Tan, Michelle T T; Loh, Hwei-San; Khiew, Poi Sim; Chiu, Wee Siong

    2016-01-15

    Graphene/zinc oxide nanocomposite was synthesised via a facile, green and efficient approach consisted of novel liquid phase exfoliation and solvothermal growth for sensing application. Highly pristine graphene was synthesised through mild sonication treatment of graphite in a mixture of ethanol and water at an optimum ratio. The X-ray diffractometry (XRD) affirmed the hydrothermal growth of pure zinc oxide nanoparticles from zinc nitrate hexahydrate precursor. The as-prepared graphene/zinc oxide (G/ZnO) nanocomposite was characterised comprehensively to evaluate its morphology, crystallinity, composition and purity. All results clearly indicate that zinc oxide particles were homogenously distributed on graphene sheets, without any severe aggregation. The electrochemical performance of graphene/zinc oxide nanocomposite-modified screen-printed carbon electrode (SPCE) was evaluated using cyclic voltammetry (CV) and amperometry analysis. The resulting electrode exhibited excellent electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2) in a linear range of 1-15 mM with a correlation coefficient of 0.9977. The sensitivity of the graphene/zinc oxide nanocomposite-modified hydrogen peroxide sensor was 3.2580 μAmM(-1) with a limit of detection of 7.4357 μM. An electrochemical DNA sensor platform was then fabricated for the detection of Avian Influenza H5 gene based on graphene/zinc oxide nanocomposite. The results obtained from amperometry study indicate that the graphene/zinc oxide nanocomposite-enhanced electrochemical DNA biosensor is significantly more sensitive (P < 0.05) and efficient than the conventional agarose gel electrophoresis.

  5. In situ optical measurement of the rapid Li intercalation and deintercalation dynamics in colloidal 2D layered TiS2 nanodiscs

    Science.gov (United States)

    Ren, Jiageng; Camacho-Forero, Luis E.; Rossi, Daniel; Park, Yerok; Balbuena, Perla B.; Son, Dong Hee

    2016-05-01

    We report the in situ optical measurements of the rapid Li intercalation and deintercalation dynamics in 2-dimensional (2D) layered transition metal dichalcogenide (TMD) with a nanoscale lateral dimension using thin films fabricated with size-controlled colloidal TiS2 nanodiscs. The films exhibiting high optical homogeneity, where the interband absorption changes near-linearly to the amount of intercalated Li, enabled facile optical probing of the intercalation dynamics overcoming the shortcomings of amperometry susceptible to complications from non-Faradaic processes. The time scale of Li intercalation and deintercalation was on the order of seconds in the nanodiscs of ~100 nm lateral dimension, indicating sufficiently rapid dynamic control of the intercalation-induced material properties with a reduced lateral dimension. The change in the rate and reversibility of the dynamics during the multiple intercalation/deintercalation cycles was also measured, providing a unique window to observe the effect of potential structural changes on the intercalation and deintercalation dynamics in 2D layered TMD structures with a nanoscale lateral dimension.We report the in situ optical measurements of the rapid Li intercalation and deintercalation dynamics in 2-dimensional (2D) layered transition metal dichalcogenide (TMD) with a nanoscale lateral dimension using thin films fabricated with size-controlled colloidal TiS2 nanodiscs. The films exhibiting high optical homogeneity, where the interband absorption changes near-linearly to the amount of intercalated Li, enabled facile optical probing of the intercalation dynamics overcoming the shortcomings of amperometry susceptible to complications from non-Faradaic processes. The time scale of Li intercalation and deintercalation was on the order of seconds in the nanodiscs of ~100 nm lateral dimension, indicating sufficiently rapid dynamic control of the intercalation-induced material properties with a reduced lateral dimension

  6. Development of Microelectrode Arrays Using Electroless Plating for CMOS-Based Direct Counting of Bacterial and HeLa Cells.

    Science.gov (United States)

    Niitsu, Kiichi; Ota, Shoko; Gamo, Kohei; Kondo, Hiroki; Hori, Masaru; Nakazato, Kazuo

    2015-10-01

    The development of two new types of high-density, electroless plated microelectrode arrays for CMOS-based high-sensitivity direct bacteria and HeLa cell counting are presented. For emerging high-sensitivity direct pathogen counting, two technical challenges must be addressed. One is the formation of a bacteria-sized microelectrode, and the other is the development of a high-sensitivity and high-speed amperometry circuit. The requirement for microelectrode formation is that the gold microelectrodes are required to be as small as the target cell. By improving a self-aligned electroless plating technique, the dimensions of the microelectrodes on a CMOS sensor chip in this work were successfully reduced to 1.2 μm × 2.05 μm. This is 1/20th of the smallest size reported in the literature. Since a bacteria-sized microelectrode has a severe limitation on the current flow, the amperometry circuit has to have a high sensitivity and high speed with low noise. In this work, a current buffer was inserted to mitigate the potential fluctuation. Three test chips were fabricated using a 0.6- μm CMOS process: two with 1.2 μm × 2.05 μm (1024 × 1024 and 4 × 4) sensor arrays and one with 6- μm square (16 × 16) sensor arrays; and the microelectrodes were formed on them using electroless plating. The uniformity among the 1024 × 1024 electrodes arranged with a pitch of 3.6 μm × 4.45 μm was optically verified. For improving sensitivity, the trenches on each microelectrode were developed and verified optically and electrochemically for the first time. Higher sensitivity can be achieved by introducing a trench structure than by using a conventional microelectrode formed by contact photolithography. Cyclic voltammetry (CV) measurements obtained using the 1.2 μm × 2.05 μm 4 × 4 and 6- μm square 16 × 16 sensor array with electroless-plated microelectrodes successfully demonstrated direct counting of the bacteria-sized microbeads and HeLa cells. PMID:26561481

  7. Alpha-latrotoxin Triggers Extracellular Ca2+-dependent Exocytosis and Sensitizes Fusion Machinery in Endocrine Cells

    Institute of Scientific and Technical Information of China (English)

    Zhi-Tao HU; Ping ZHAO; Jie LIU; Zheng-Xing WU; Tao XU

    2006-01-01

    α-Latrotoxin from the venom of black widow spider induces and augments neurotransmitter and hormone release by way of extracellular Ca2+ influx and cellular signal transduction pathways. By using whole cell current and capacitance recording, the photolysis of caged Ca2+, and Ca2+ microfluorometry and amperometry, we investigated the stimulating effect and mechanism of o-latrotoxin on exocytosis in rat pancreatic β cells, LβT2 cells and latrophilin plasmid-transfected INS-1 cells. Our data indicated that: (1) α-latrotoxin increased cytosolic Ca2+ concentration through the formation of cation-permitting pores and subsequent Ca2+ influx with the presence of extracellular Ca2+; (2) α-latrotoxin stimulated exocytosis in normal bath solution and its stimulating effect on secretion was eradicated in Ca2+-free bath solution; and (3) α-latrotoxin sensitized the molecular machinery of fusion through activation of protein kinase C and increased the response of cells to Ca2+ photolysed by a flash of ultraviolet light. In summary, α-latrotoxin induced exocytosis by way of Ca2+ influx and accelerated vesicle fusion by the sensitization of fusion machinery.

  8. Electropolymerized phenol derivatives as permselective polymers for biosensor applications.

    Science.gov (United States)

    Calia, Giammario; Monti, Patrizia; Marceddu, Salvatore; Dettori, Maria A; Fabbri, Davide; Jaoua, Samir; O'Neill, Robert D; Serra, Pier A; Delogu, Giovanna; Migheli, Quirico

    2015-05-21

    Amperometric biosensors are often coated with a polymeric permselective film to avoid electroactive interference by reducing agents present in the target medium. Phenylenediamine and phenol monomers are commonly used to form these permselective films in the design of microsensors and biosensors. This paper aims to evaluate the permselectivity, stability and lifetime of polymers electrosynthesized using either constant potential amperometry (CPA) or cyclic voltammetry (CV) from naturally occurring phenylpropanoids in monomeric and dimeric forms (eugenol, isoeugenol, dehydrodieugenol and magnolol). Sensors were characterized by scanning electron microscopy and permselectivity analysis. Magnolol formed an electro-deposited polymer with a more defined three-dimensional texture in comparison with the other films. The phenol-derived films showed different permselectivity towards H2O2 over ascorbic acid and dopamine, likely to be related to the thickness and compactness of the polymer. The CV-derived films had a better permselectivity compared to the CPA-corresponding polymers. Based on these results, the permselectivity, stability and lifetime of a biosensor for glucose were studied when a magnolol coating was electro-deposited. The structural principles governing the permselectivity of the magnolol-derived film are suggested to be mainly related to the conformational flexibility of this monomer. Newly designed biosensors, coated with electropolymerized natural phenol derivatives, may represent promising analytical devices for different application fields. PMID:25857616

  9. A novel, disposable, screen-printed amperometric biosensor for glucose in serum fabricated using a water-based carbon ink.

    Science.gov (United States)

    Crouch, Eric; Cowell, David C; Hoskins, Stephen; Pittson, Robin W; Hart, John P

    2005-11-15

    Screen-printed amperometric glucose biosensors have been fabricated using a water-based carbon ink. The enzyme glucose oxidase (GOD) and the electro-catalyst cobalt phthalocyanine were mixed with the carbon ink prior to the screen-printing process; therefore, biosensors are prepared in a one-step fabrication procedure. Optimisation of the biosensor performance was achieved by studying the effects of pH, buffer strength, and applied potential on the analytical response. Calibration studies were performed under optimum conditions, using amperometry in stirred solution, with an operating potential of +500 mV versus SCE. The sensitivity was found to be 1170 nA mM(-1), with a linear range of 0.025-2 mM; the former represents the detection limit. The disposable amperometric biosensor was evaluated by carrying out replicate determinations on a sample of bovine serum. This was achieved by the method of multiple standard additions and included a correction for background currents arising from oxidizable serum components. The mean serum concentration was calculated to be 8.63 mM and compared well with the supplier's value of 8.3 mM; the coefficient of variation was calculated to be 3.3% (n=6). PMID:16242609

  10. Amperometric determination of hydrogen peroxide by functionalized carbon nanotubes through EDC/NHS coupling chemistry.

    Science.gov (United States)

    Jeykumari, D R Shobha; Narayanan, S Sriman

    2007-06-01

    The electrochemistry of the redox mediator Toluidine blue (TB) which was covalently linked to the carboxyl group of the multiwalled carbon nanotubes (MWNTs) by coupling reactions, in which N-hydroxysuccinimide was used to assist 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride catalyzed amidation reaction is described. The results from cyclic voltammetry (CV) and amperometry suggested that the redox mediator is linked to the surface of the MWNTs and the nanotubes showed an obvious promotion for the direct electron-transfer between the redox mediator and the electrode. A couple of well-defined redox peak of TB was observed in a phosphate buffer solution (pH 7.0). The redox mediator immobilized to MWNTs exhibits remarkable electrocatalytic activity for the reduction of hydrogen peroxide (H2O2). The analytical applicability of the modified electrode for the determination of hydrogen peroxide was examined. A linear response in the concentration range of 6.8 x 10(-7)-3.4 x 10(-2) M (r = 0.9958) was obtained with detection limit of 3.4 x 10(-7) M for the determination of hydrogen peroxide. The modified electrode has advantages of being highly stable, sensitive, ease of construction and use. PMID:17654948

  11. Synthesis of single-crystal α-MnO2 nanotubes-loaded Ag@C core-shell matrix and their application for electrochemical sensing of nonenzymatic hydrogen peroxide.

    Science.gov (United States)

    Zhang, Sai; Zheng, Jianbin

    2016-10-01

    A nonenzymatic hydrogen peroxide sensor was fabricated by combing the crystal α-MnO2 nanotubes and Ag@C core-shell matrix with their own superior characteristics. The morphology, size and electrochemical of the sensing interface materials and the relationship between the electrical catalytic properties and sensor response performance were also studied, established a new method for the detection of hydrogen peroxide (H2O2). The structure and morphology of hollow tubular-like MnO2 and MnO2-Ag@C film were characterized by scanning electron micrograph (SEM), transmission electron microscopy (TEM) and X-ray diffraction. The electrochemical properties of the sensor were explored by cyclic voltammetry and amperometry. The investigation showed that the MnO2-Ag@C at the sensor exhibited a high electrocatalytic activity towards electroreduction of hydrogen peroxide; and under the optimal conditions, the linear ranges of hydrogen peroxide were 0.5μM to 5.7mM with a low detection limit of 0.17μM (S/N=3) and high sensitivity of 127.2μAmM(-1)cm(-2). Compared with other nonenzymatic hydrogen peroxide sensor, the fabricated sensor own lower detection limit, demonstrating that MnO2-Ag@C nanocomposite film will be a new promising platform for the construction of hydrogen peroxide sensors. PMID:27474303

  12. Multifunctional DNA-based biomemory device consisting of ssDNA/Cu heterolayers.

    Science.gov (United States)

    Lee, Taek; El-Said, Waleed Ahmed; Min, Junhong; Choi, Jeong-Woo

    2011-01-15

    In the present study, we developed a novel DNA-based biomemory device that was comprised of ssDNA/Cu heterolayers on Au electrodes. As a conducting material, a thiol-modified single strand DNA (26 bp) was designed and immobilized on the Au electrode without the need for any linker material. Cu(2+) ions, which acted as the active site, were then chemically absorbed on the external structure of ssDNA through electrostatic interactions. The presence of the fabricated ssDNA/Cu heterolayer was confirmed by surface plasmon resonance (SPR) spectroscopy and Raman spectroscopy. Cyclic voltammetry experiments were carried out to investigate the redox properties of ssDNA/Cu hybrids to obtain the oxidation and reduction potential. Based on measured oxidation and reduction potential, a ROM-type, 3-state type, and WORM type DNA memory functions were demonstrated by chronoamperometry (CA) and open circuit potential amperometry (OCPA). This proposed device acts and operates the memory function very well. In the near future, DNA based biomemory device in this study could provide the alternative to the inorganic electronic device when molecular scaled immobilization control and signal measurement are achieved. PMID:21051218

  13. CE microchips: an opened gate to food analysis.

    Science.gov (United States)

    Escarpa, Alberto; González, María Cristina; Crevillén, Agustín González; Blasco, Antonio Javier

    2007-03-01

    CE microchips are the first generation of micrototal analysis systems (-TAS) emerging in the miniaturization scene of food analysis. CE microchips for food analysis are fabricated in both glass and polymer materials, such as PDMS and poly(methyl methacrylate) (PMMA), and use simple layouts of simple and double T crosses. Nowadays, the detection route preferred is electrochemical in both, amperometry and conductivity modes, using end-channel and contactless configurations, respectively. Food applications using CE microchips are now emerging since food samples present complex matrices, the selectivity being a very important challenge because the total integration of analytical steps into microchip format is very difficult. As a consequence, the first contributions that have recently appeared in the relevant literature are based primarily on fast separations of analytes of high food significance. These protocols are combined with different strategies to achieve selectivity using a suitable nonextensive sample preparation and/or strategically choosing detection routes. Polyphenolic compounds, amino acids, preservatives, and organic and inorganic ions have been studied using CE microchips. Thus, new and exciting future expectations arise in the domain of food analysis. However, several drawbacks could easily be found and assumed within the miniaturization map.

  14. Chiral analysis of amino acids using electrochemical composite bienzyme biosensors.

    Science.gov (United States)

    Domínguez, R; Serra, B; Reviejo, A J; Pingarrón, J M

    2001-11-15

    The construction and performance of bienzyme amperometric composite biosensors for the selective determination of l- or d-amino acids is reported. D- or L-Amino acid oxidase, horseradish peroxidase, and the mediator ferrocene were coimmobilized by simple physical inclusion into the bulk of a graphite-70% Teflon electrode matrix. Working conditions including amino acid oxidase loading and pH were optimized. Studies on the repeatability of the amperometric response obtained at +0.00 V, with and without regeneration of the electrode surface by polishing, on the useful lifetime of one single biosensor and on the reproducibility in the fabrication of different biosensors illustrate the robustness of the bioelectrodes design. Calibration plots by both amperometry in stirred solutions and flow injection with amperometric detection were obtained for L-arginine, L-phenylalanine, L-leucine, L-methionine, L-tryptophan, D-leucine, D-methionine, D-serine, and D-valine. Differences in sensitivity were discussed in terms of the hydrophobicity of the substrate and of the electrode surface. The bienzyme composite electrode was applied to the determination of L- and D-amino acids in racemic samples, as well as to the estimation of the L-amino acids content in muscatel grapes. PMID:11700983

  15. Mediator-free electrochemical biosensor based on buckypaper with enhanced stability and sensitivity for glucose detection.

    Science.gov (United States)

    Ahmadalinezhad, Asieh; Wu, Guosheng; Chen, Aicheng

    2011-12-15

    Here we report on a novel platform based on buckypaper for the design of high-performance electrochemical biosensors. Using glucose oxidase as a model enzyme, we constructed a biocompatible mediator-free biosensor and studied the potential effect of the buckypaper on the stability of the biosensor with both amperometry and FTIR spectroscopy. The results showed that the biosensor responses sensitively and selectively to glucose with a considerable functional lifetime of over 80 days. The fabricated enzymatic sensor detects glucose with a dynamic linear range of over 9 mM and a detection limit of 0.01 mM. To examine the efficiency of enzyme immobilization, the Michaelis-Menten constant (K(M)(app)) was calculated to be 4.67 mM. In addition, the fabricated electrochemical biosensor shows high selectivity; no amperometric response to the common interference species such as ascorbic acid, uric acid and acetamidophenol was observed. The facile and robust buckypaper-based platform proposed in this study opens the door for the design of high-performance electrochemical biosensors for medical diagnostics and environmental monitoring. PMID:22014621

  16. Carbon Fiber Ultramicrodic Electrode Electrodeposited with Over-Oxidized Polypyrrole for Amperometric Detection of Vesicular Exocytosis from Pheochromocytoma Cell

    Directory of Open Access Journals (Sweden)

    Li Wang

    2015-01-01

    Full Text Available Vesicular exocytosis is ubiquitous, but it is difficult to detect within the cells’ communication mechanism. For this purpose, a 2 µm ultramicrodic carbon fiber electrode was fabricated in this work based on electrodeposition with over-oxidized polypyrrole nanoparticle (PPyox-CFE, which was applied successfully for real-time monitoring of quantal exocytosis from individual pheochromocytoma (PC12 cells. PPyox-CFE was evaluated by dopamine (DA solutions through cyclic voltammetry and amperometry electrochemical methods, and results revealed that PPyox-CFE improved the detection limit of DA. In particular, the sensitivity of DA was improved to 24.55 µA·µM−1·µm−2 using the PPyox-CFE. The ultramicrodic electrode combined with the patch-clamp system was used to detect vesicular exocytosis of DA from individual PC12 cells with 60 mM K+ stimulation. A total of 287 spikes released from 7 PC12 cells were statistically analyzed. The current amplitude (Imax and the released charge (Q of the amperometric spikes from the DA release by a stimulated PC12 cell is 45.1 ± 12.5 pA and 0.18 ± 0.04 pC, respectively. Furthermore, on average ~562,000 molecules were released in each vesicular exocytosis. PPyox-CFE, with its capability of detecting vesicular exocytosis, has potential application in neuron communication research.

  17. Feeding induced by cannabinoids is mediated independently of the melanocortin system.

    Directory of Open Access Journals (Sweden)

    Puspha Sinnayah

    Full Text Available BACKGROUND: Cannabinoids, the active components of marijuana, stimulate appetite, and cannabinoid receptor-1 (CB1-R antagonists suppress appetite and promote weight loss. Little is known about how CB1-R antagonists affect the central neurocircuitry, specifically the melanocortin system that regulates energy balance. METHODOLOGY/PRINCIPAL FINDINGS: Here, we show that peripherally administered CB1-R antagonist (AM251 or agonist equally suppressed or stimulated feeding respectively in A(y , which lack a functional melanocortin system, and wildtype mice, demonstrating that cannabinoid effects on feeding do not require melanocortin circuitry. CB1-R antagonist or agonist administered into the ventral tegmental area (VTA equally suppressed or stimulated feeding respectively, in both genotypes. In addition, peripheral and central cannabinoid administration similarly induced c-Fos activation in brain sites suggesting mediation via motivational dopaminergic circuitry. Amperometry-detected increases in evoked dopamine (DA release by the CB1-R antagonist in nucleus accumbens slices indicates that AM251 modulates DA release from VTA terminals. CONCLUSIONS/SIGNIFICANCE: Our results demonstrate that the effects of cannabinoids on energy balance are independent of hypothalamic melanocortin circuitry and is primarily driven by the reward system.

  18. Toward the Digital Electrochemical Recognition of Cobalt, Iridium, Nickel, and Iron Ion Collisions by Catalytic Amplification.

    Science.gov (United States)

    Dick, Jeffrey E; Bard, Allen J

    2016-07-13

    We report the electrochemical detection of femtomolar amounts of cobalt, iridium, nickel, and iron ions in solution by electrocatalyst formation and amplification. The metal oxides of these ions can be formed electrochemically and can catalyze the oxidation of water. Alternatively, the reduction of metal ions to metals, such as the reduction of IrCl6(3-) to iridium, is capable of electrocatalytically reducing protons to molecular hydrogen, as shown previously with Pt. These events, which manifest themselves in amperometry, correspond to the formation of electrocatalytic nuclei on the electrode surface, capable of electrocatalytically oxidizing water or reducing protons. An analysis of the frequency of anodic blips compared to theory implies that the requirement for water oxidation is 10 ± 1 ions of cobalt, 13 ± 4 ions of iridium, and 11 ± 3 ions of nickel. A similar analysis for iridium reduction and the corresponding catalytic reduction of protons implies that 6 ± 2 ions of iridium are required for proton reduction. These numbers are confirmed in an analysis of the time of first nucleation event, i.e. the time at which the first blip on the amperometric i-t experiment occurs. We further show that the anodic blips in detecting nickel increase in intensity upon increasing amounts of iron ions in solution to a ratio of Ni/Fe of ∼5, surprisingly close to that for bulk electrocatalysts of Ni-Fe. PMID:27295309

  19. Development and Characterization of a Diamond-Insulated Graphitic Multi Electrode Array Realized with Ion Beam Lithography

    Directory of Open Access Journals (Sweden)

    Federico Picollo

    2014-12-01

    Full Text Available The detection of quantal exocytic events from neurons and neuroendocrine cells is a challenging task in neuroscience. One of the most promising platforms for the development of a new generation of biosensors is diamond, due to its biocompatibility, transparency and chemical inertness. Moreover, the electrical properties of diamond can be turned from a perfect insulator into a conductive material (resistivity ~mΩ·cm by exploiting the metastable nature of this allotropic form of carbon. A 16‑channels MEA (Multi Electrode Array suitable for cell culture growing has been fabricated by means of ion implantation. A focused 1.2 MeV He+ beam was scanned on a IIa single-crystal diamond sample (4.5 × 4.5 × 0.5 mm3 to cause highly damaged sub-superficial structures that were defined with micrometric spatial resolution. After implantation, the sample was annealed. This process provides the conversion of the sub-superficial highly damaged regions to a graphitic phase embedded in a highly insulating diamond matrix. Thanks to a three-dimensional masking technique, the endpoints of the sub-superficial channels emerge in contact with the sample surface, therefore being available as sensing electrodes. Cyclic voltammetry and amperometry measurements of solutions with increasing concentrations of adrenaline were performed to characterize the biosensor sensitivity. The reported results demonstrate that this new type of biosensor is suitable for in vitro detection of catecholamine release.

  20. Biosensor based on tyrosinase immobilized on a single-walled carbon nanotube-modified glassy carbon electrode for detection of epinephrine

    Directory of Open Access Journals (Sweden)

    Apetrei IM

    2013-11-01

    Full Text Available Irina Mirela Apetrei,1 Constantin Apetrei21Department of Pharmaceutical Sciences, Faculty of Medicine and Pharmacy, 2Department of Chemistry, Physics and Environment, Faculty of Sciences and Environment, Dunarea de Jos University of Galati, RomaniaAbstract: A biosensor comprising tyrosinase immobilized on a single-walled carbon nanotube-modified glassy carbon electrode has been developed. The sensitive element, ie, tyrosinase, was immobilized using a drop-and-dry method followed by cross-linking. Tyrosinase maintained high bioactivity on this nanomaterial, catalyzing the oxidation of epinephrine to epinephrine-quinone, which was electrochemically reduced (-0.07 V versus Ag/AgCl on the biosensor surface. Under optimum conditions, the biosensor showed a linear response in the range of 10–110 µM. The limit of detection was calculated to be 2.54 µM with a correlation coefficient of 0.977. The repeatability, expressed as the relative standard deviation for five consecutive determinations of 10-5 M epinephrine solution was 3.4%. A good correlation was obtained between results obtained by the biosensor and those obtained by ultraviolet spectrophotometric methods.Keywords: amperometry, single-walled carbon nanotubes, spectrophotometry, catecholamine, pharmaceutical formula

  1. Novel amperometric sensor using metolcarb-imprinted film as the recognition element on a gold electrode and its application

    International Nuclear Information System (INIS)

    A molecularly imprinted film is electrochemically synthesized on a gold electrode using cyclic voltammetry to electropolymerize o-aminothiophenol in the presence of metolcarb (MTMC). The mechanism of the imprinting process and a number of factors affecting the activity of the imprinted film are discussed and optimized. Scanning electron microscope observations and binding measurements have proved that an MTMC-imprinted film (with a thickness of nearly 100 nm) was formed on the surface of the gold electrode. The film exhibited high binding affinity and selectivity towards the template MTMC, as well as good penetrability, reproducibility and stability. A novel amperometry sensor using the imprinted film as recognition element was developed for MTMC determination in food samples. Under the experimental conditions, the MTMC standard is linear within the concentration range studied (r2 = 0.9906). The limit of detection (S/N = 3) of the modified electrode was achieved to 1.34 x 10-8 mol L-1. Recoveries of MTMC from spiked apple juice, cabbage and cucumber samples for the developed electrochemical assay ranged from 94.80% to 102.43%, which was with great correlation coefficient (0.9929) with results from high-performance liquid chromatography. In practical application, the prepared amperometric sensor also showed good reproducibility and long lifetime for storage. The research in this study has offered a rapid, accurate and sensitive electrochemical method for quantitative determination of MTMC in food products.

  2. A nano-structured Ni(II)–chelidamic acid modified gold nanoparticle self-assembled electrode for electrocatalytic oxidation and determination of methanol

    International Nuclear Information System (INIS)

    A nano-structured Ni(II)–chelidamic acid (2,6-dicarboxy-4-hydroxypyridine) film was electrodeposited on a gold nanoparticle–cysteine–gold electrode. The morphology of Ni(II)–chelidamic acid gold nanoparticle self‐assembled electrode was investigated by scanning electron microscopy (SEM). Electrocatalytic oxidation of methanol on the surface of modified electrode was studied by cyclic voltammetry and chronoamperometry methods. The hydrodynamic amperometry at a rotating modified electrode at constant potential versus reference electrode was used for detection of methanol. Under optimized conditions the calibration plots are linear in the concentration range 0–50 mM with a detection limit of 15 μM. The formed matrix in our work possessed a 3D porous network structure with a large effective surface area, high catalytic activity and behaved like microelectrode ensembles. The modified electrode indicated reproducible behavior and a high level stability during the experiments, making it particularly suitable for analytical purposes. - Highlights: ► The Au electrode modified with thin Ni(II)/CHE-AuNP film shows stable and reproducible behavior. ► Long stability and excellent electrochemical reversibility were observed. ► This modified electrode shows excellent catalytic activity for methanol oxidation. ► Combination of unique properties of AuNP and Ni(II)/CHE resulted in improvement of current responses.

  3. A Micro-Platinum Wire Biosensor for Fast and Selective Detection of Alanine Aminotransferase

    Directory of Open Access Journals (Sweden)

    Tran Nguyen Thanh Thuy

    2016-05-01

    Full Text Available In this study, a miniaturized biosensor based on permselective polymer layers (overoxidized polypyrrole (Ppy and Nafion® modified and enzyme (glutamate oxidase (GlutOx immobilized micro-platinum wire electrode for the detection of alanine aminotransferase (ALT was fabricated. The proposed ALT biosensor was measured electrochemically by constant potential amperometry at +0.7 V vs. Ag/AgCl. The ALT biosensor provides fast response time (~5 s and superior selectivity towards ALT against both negatively and positively charged species (e.g., ascorbic acid (AA and dopamine (DA, respectively. The detection range of the ALT biosensor is found to be 10–900 U/L which covers the range of normal ALT levels presented in the serum and the detection limit and sensitivity are found to be 8.48 U/L and 0.059 nA/(U/L·mm2 (N = 10, respectively. We also found that one-day storage of the ALT biosensor at −20 °C right after the sensor being fabricated can enhance the sensor sensitivity (1.74 times higher than that of the sensor stored at 4 °C. The ALT biosensor is stable after eight weeks of storage at −20 °C. The sensor was tested in spiked ALT samples (ALT activities: 20, 200, 400, and 900 U/L and reasonable recoveries (70%~107% were obtained.

  4. Staircase and pulse potential electrochemical techniques for the facile and rapid synthesis of Pt and PtAg materials

    International Nuclear Information System (INIS)

    Electrochemical synthesis is an attractive option for the synthesis of materials because electrocrystallization is faster (microseconds), easier (fewer variables influence structure) and more cost-effective (only requiring an ion source and electrolyte) than traditional chemical methods. Pt and PtAg materials were synthesised using electrochemical techniques, including staircase cyclic voltammetry (CV). Differential pulse amperometry (DPA), square wave voltammetry (SWV) and second harmonic AC voltammetry (2nd H AC V) were employed as pulse potential techniques. Characterisation was conducted using X-ray diffraction, field emission scanning electron microscopy, X-ray fluorescence, cyclic voltammetry in acidic and basic media and by assessing the behaviour of the synthesised materials in oxygen reduction reaction (ORR). For the cyclic voltammetry and DPA techniques, a decrease in the interfacial electrode/solution concentration resulted in the formation of semi-spherical nanoparticles with dendritic nanosheet growth. Semi-spherical Pt nanoparticles with small crystal sizes were obtained using SWV and 2nd H AC V due to the enhancement of the Pt seed growth by the low-time pulse potential period. Silver incorporation allowed the formation of well-defined cubic-shaped and flower-like PtAg nanoparticles without the need for surfactants and/or reductants. Silver acted both as a silver ion source and an additive, due to its passivation of the particle surfaces

  5. Midbrain Gene Screening Identifies a New Mesoaccumbal Glutamatergic Pathway and a Marker for Dopamine Cells Neuroprotected in Parkinson’s Disease

    Science.gov (United States)

    Viereckel, Thomas; Dumas, Sylvie; Smith-Anttila, Casey J. A.; Vlcek, Bianca; Bimpisidis, Zisis; Lagerström, Malin C.; Konradsson-Geuken, Åsa; Wallén-Mackenzie, Åsa

    2016-01-01

    The ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) of the midbrain are associated with Parkinson’s disease (PD), schizophrenia, mood disorders and addiction. Based on the recently unraveled heterogeneity within the VTA and SNc, where glutamate, GABA and co-releasing neurons have been found to co-exist with the classical dopamine neurons, there is a compelling need for identification of gene expression patterns that represent this heterogeneity and that are of value for development of human therapies. Here, several unique gene expression patterns were identified in the mouse midbrain of which NeuroD6 and Grp were expressed within different dopaminergic subpopulations of the VTA, and TrpV1 within a small heterogeneous population. Optogenetics-coupled in vivo amperometry revealed a previously unknown glutamatergic mesoaccumbal pathway characterized by TrpV1-Cre-expression. Human GRP was strongly detected in non-melanized dopaminergic neurons within the SNc of both control and PD brains, suggesting GRP as a marker for neuroprotected neurons in PD. This study thus unravels markers for distinct subpopulations of neurons within the mouse and human midbrain, defines unique anatomical subregions within the VTA and exposes an entirely new glutamatergic pathway. Finally, both TRPV1 and GRP are implied in midbrain physiology of importance to neurological and neuropsychiatric disorders. PMID:27762319

  6. Ni(II)-quercetin complex modified multiwall carbon nanotube ionic liquid paste electrode and its electrocatalytic activity toward the oxidation of glucose

    Energy Technology Data Exchange (ETDEWEB)

    Zheng Li [Institute of Analytical Science, Northwest University, Xi' an, 710069 (China); College of Chemistry and Chemical Engineering, Xi' an Shiyou University, Xi' an, 710065 (China); Zhang Jiaoqiang [Department of Applied Chemistry, School of Science, Northwestern Polytechnical University, Xi' an, 710072 (China); Song Junfeng [Institute of Analytical Science, Northwest University, Xi' an, 710069 (China)], E-mail: songjunf@nwu.edu.cn

    2009-07-30

    A modified electrode Ni(II)-Qu-MWCNT-IL-PE has been fabricated by electrodepositing Ni(II)-quercetin [Ni(II)-Qu] complex on the surface of multi-wall carbon nanotube ionic liquid paste electrode (MWCNT-IL-PE) in alkaline solution. The Ni(II)-Qu-MWCNT-IL-PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple compared with Ni(II)-Qu-MWCNT-PE. It also shows good electrocatalytic activity toward the oxidation of glucose. Kinetic parameters such as the electron transfer coefficient {alpha}, rate constant k{sub s} of the electrode reaction and the catalytic rate constant k{sub cat} of the catalytic reaction are determined. Moreover, the catalytic current presents linear dependence on the concentration of glucose from 5.0 {mu}M to 2.8 mM, with a detection limit of 1.0 {mu}M by amperometry. The modified electrode for glucose determination is of the property of simple preparation, good stability, fast response and high sensitivity.

  7. Dynamin-dependent and dynamin-independent processes contribute to the regulation of single vesicle release kinetics and quantal size

    Science.gov (United States)

    Graham, Margaret E.; O'Callaghan, Dermott W.; McMahon, Harvey T.; Burgoyne, Robert D.

    2002-01-01

    Accumulating evidence suggests that the kinetics of release from single secretory vesicles can be regulated and that quantal size can be modified during fast kiss-and-run fusion. Multiple pathways for vesicle retrieval have been identified involving clathrin and dynamin. It has been unclear whether dynamin could participate in a fast kiss-and-run process to reclose a transient fusion pore and thereby limit vesicle release. We have disrupted dynamin function in adrenal chromaffin cells by expression of the amphiphysin Src-homology domain 3 (SH3) or by application of guanosine 5′-[γ-thio]triphosphate (GTPγS), and have monitored single vesicle release events, evoked by digitonin and Ca2+, by using carbon-fiber amperometry. Under both conditions, there was an increase in mean quantal size accompanying an increase in the half-width of amperometric spikes and a slowing of the fall time. These data suggest the existence of a dynamin-dependent process that can terminate vesicle release under basal conditions. Protein kinase C activation changed release kinetics and decreased quantal size by shortening the release period. The effects of phorbol ester treatment were not prevented by expression of the amphiphysin SH3 domain or by GTPγS suggesting the existence of alternative dynamin-independent process underlying fast kiss-and-run exocytosis. PMID:11997474

  8. Ferrocene Derivative Mediator Bonded Sol-gel Membrane Glucose Biosensor

    Institute of Scientific and Technical Information of China (English)

    XUAN, Guang-Shan; KIM, Moon-Chang; HER, Dae-Sung; LEE, Heung-Lark

    2006-01-01

    The sol-gel derived glucose biosensor was developed, and the sol-gel membrane was organically modified by N-(3-triethoxysilylpropyl)-ferrocenylmethylamine (FcSi) as sol-gel precursor to make electrochemical biosensor.The structure of biosensor was sol-gel/FcSi+Gox/GC type (glucose oxidase, Gox). The ferrocene mediator was chemically immobilized to the silane network, and Gox was entrapped to the sol-gel glass network. Therefore,these structures prevented mediator leakage and retained the enzyme activity. Additionally, pH of electrolyte, temperature effects, and interference of positive substances with biosensor were investigated. And the electrochemical performance of biosensor was studied by amperometry. The results indicated that the linear range, detection limit,and response slope of biosensor was 2.00× 10-4-1.57× 10-3 mol·L-1, 2.0× 10-4 mol·L-1 and 5.06× 105 nA·mol-1 · L, respectively.

  9. Electrochemical Quantification of the Antioxidant Capacity of Medicinal Plants Using Biosensors

    Directory of Open Access Journals (Sweden)

    Erika Rodríguez-Sevilla

    2014-08-01

    Full Text Available The working area of a screen-printed electrode, SPE, was modified with the enzyme tyrosinase (Tyr using different immobilization methods, namely entrapment with water-soluble polyvinyl alcohol (PVA, cross-linking using glutaraldehyde (GA, and cross-linking using GA and human serum albumin (HSA; the resulting electrodes were termed SPE/Tyr/PVA, SPE/Tyr/GA and SPE/Tyr/HSA/GA, respectively. These biosensors were characterized by means of amperometry and EIS techniques. From amperometric evaluations, the apparent Michaelis-Menten constant, Km′, of each biosensor was evaluated while the respective charge transfer resistance, Rct, was assessed from impedance measurements. It was found that the SPE/Tyr/GA had the smallest Km′ (57 ± 7 µM and Rct values. This electrode also displayed both the lowest detection and quantification limits for catechol quantification. Using the SPE/Tyr/GA, the Trolox Equivalent Antioxidant Capacity (TEAC was determined from infusions prepared with “mirto” (Salvia microphylla, “hHierba dulce” (Lippia dulcis and “salve real” (Lippia alba, medicinal plants commonly used in Mexico.

  10. Electrochemical sensor using neomycin-imprinted film as recognition element based on chitosan-silver nanoparticles/graphene-multiwalled carbon nanotubes composites modified electrode.

    Science.gov (United States)

    Lian, Wenjing; Liu, Su; Yu, Jinghua; Li, Jie; Cui, Min; Xu, Wei; Huang, Jiadong

    2013-06-15

    A novel imprinted electrochemical sensor for neomycin recognition was developed based on chitosan-silver nanoparticles (CS-SNP)/graphene-multiwalled carbon nanotubes (GR-MWCNTs) composites decorated gold electrode. Molecularly imprinted polymers (MIPs) were synthesized by electropolymerization using neomycin as the template, and pyrrole as the monomer. The mechanism of the fabrication process and a number of factors affecting the activity of the imprinted sensor have been discussed and optimized. The characterization of imprinted sensor has been carried out by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The performance of the proposed imprinted sensor has been investigated using cyclic voltammetry (CV) and amperometry. Under the optimized conditions, the linear range of the sensor was from 9×10(-9)mol/L to 7×10(-6)mol/L, with the limit of detection (LOD) of 7.63×10(-9)mol/L (S/N=3). The film exhibited high binding affinity and selectivity towards the template neomycin, as well as good reproducibility and stability. Furthermore, the proposed sensor was applied to determine the neomycin in milk and honey samples based on its good reproducibility and stability, and the acceptable recovery implied its feasibility for practical application. PMID:23395725

  11. Enhanced sensitivity for biosensors: Functionalized P1,5-diaminonaphthalene-multiwall carbon nanotube composite film-modified electrode

    International Nuclear Information System (INIS)

    A homogeneous electroactive poly(1,5-diaminonaphthalene) (P1,5DAN) and multiwalled carbon nanotube (MWNT) composite film-modified electrode was fabricated by cyclic voltammetry and a casting method. The dispersion and morphology of the MWNTs/P1,5DAN composite film were investigated by scanning electron microscopy. The cyclic voltammograms of the electrode modified by the MWNTs/P15DAN composite film strongly depended on the film thickness and pH of the electrolyte solution. Two absolutely isolated oxidation potentials were found as the MWCNTs were immobilized onto the surface of P1,5DAN film in a pH 6.8 buffer solution containing ascorbic acid (AA) and uric acid (UA). Both peak currents linearly increased with increased concentrations. The electrochemical behavior of UA was not interrupted even in the presence of high-concentration AA given that AA had no observable electrochemical changes at the immobilized concentration. The electrocatalytic behavior of H2O2 was also investigated by steady-state amperometry for the immobilization of horseradish peroxidase on the P1,5DAN film. The plot of the response current vs. H2O2 concentration was linear over the wide concentration range of 0.015–5.37 mM.

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

    Directory of Open Access Journals (Sweden)

    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.

  13. Development of sensitive amperometric hydrogen peroxide sensor using a CuNPs/MB/MWCNT-C60-Cs-IL nanocomposite modified glassy carbon electrode.

    Science.gov (United States)

    Roushani, Mahmoud; Bakyas, Kobra; Zare Dizajdizi, Behruz

    2016-07-01

    A sensitive hydrogen peroxide (H2O2) sensor was constructed based on copper nanoparticles/methylene blue/multiwall carbon nanotubes-fullerene-chitosan-ionic liquid (CuNPs/MB/MWCNTs-C60-Cs-IL) nanocomposites. The MB/MWCNTs-C60-Cs-IL and CuNPs were modified glassy carbon electrode (GCE) by the physical adsorption and electrodeposition of copper nitrate solution, respectively. The physical morphology and chemical composition of the surface of modified electrode was investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. The electrochemical properties of CuNPs/MB/MWCNTs-C60-Cs-IL/GCE were investigated by cyclic voltammetry (CV) and amperometry techniques and the sensor exhibited remarkably strong electrocatalytic activities toward the reduction of hydrogen peroxide. The peak currents possess a linear relationship with the concentration of H2O2 in the range of 0.2μM to 2.0mM, and the detection limit is 55.0nM (S/N=3). In addition, the modified electrode was used to determine H2O2 concentration in human blood serum sample with satisfactory results. PMID:27127028

  14. Electrochemical sensor using neomycin-imprinted film as recognition element based on chitosan-silver nanoparticles/graphene-multiwalled carbon nanotubes composites modified electrode.

    Science.gov (United States)

    Lian, Wenjing; Liu, Su; Yu, Jinghua; Li, Jie; Cui, Min; Xu, Wei; Huang, Jiadong

    2013-06-15

    A novel imprinted electrochemical sensor for neomycin recognition was developed based on chitosan-silver nanoparticles (CS-SNP)/graphene-multiwalled carbon nanotubes (GR-MWCNTs) composites decorated gold electrode. Molecularly imprinted polymers (MIPs) were synthesized by electropolymerization using neomycin as the template, and pyrrole as the monomer. The mechanism of the fabrication process and a number of factors affecting the activity of the imprinted sensor have been discussed and optimized. The characterization of imprinted sensor has been carried out by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The performance of the proposed imprinted sensor has been investigated using cyclic voltammetry (CV) and amperometry. Under the optimized conditions, the linear range of the sensor was from 9×10(-9)mol/L to 7×10(-6)mol/L, with the limit of detection (LOD) of 7.63×10(-9)mol/L (S/N=3). The film exhibited high binding affinity and selectivity towards the template neomycin, as well as good reproducibility and stability. Furthermore, the proposed sensor was applied to determine the neomycin in milk and honey samples based on its good reproducibility and stability, and the acceptable recovery implied its feasibility for practical application.

  15. Fabrication of a novel electrochemical sensor for determination of hydrogen peroxide in different fruit juice samples

    Directory of Open Access Journals (Sweden)

    Navid Nasirizadeh

    2016-01-01

    Full Text Available A new hydrogen peroxide (H2O2 sensor is fabricated based on a multiwalled carbon nanotube-modified glassy carbon electrode (MWCNT-GCE and reactive blue 19 (RB. The charge transfer coefficient, α, and the charge transfer rate constant, ks, of RB adsorbed on MWCNT-GCE were calculated and found to be 0.44 ± 0.01 Hz and 1.9 ± 0.05 Hz, respectively. The catalysis of the electroreduction of H2O2 by RB-MWCNT-GCE is described. The RB-MWCNT-GCE shows a dramatic increase in the peak current and a decrease in the overvoltage of H2O2 electroreduction in comparison with that seen at an RB modified GCE, MWCNT modified GCE, and activated GCE. The kinetic parameters such as α and the heterogeneous rate constant, k', for the reduction of H2O2 at RB-MWCNT-GCE surface were determined using cyclic voltammetry. The detection limit of 0.27μM and three linear calibration ranges were obtained for H2O2 determination at the RB-MWCNT-GCE surface using an amperometry method. In addition, using the newly developed sensor, H2O2 was determined in real samples with satisfactory results.

  16. Heme protein-gluten films: voltammetric studies and their electrocatalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Liu Hongyun; Hu Naifei

    2003-03-28

    Direct electrochemistry and electrocatalysis of heme proteins, such as hemoglobin (Hb), myoglobin (Mb), and horseradish peroxidase (HRP), incorporated in gluten biopolymer films cast on pyrolytic graphite (PG) electrodes, were studied by voltammetry and amperometry. All the three protein-gluten films exhibited a pair of well-defined, quasi-reversible cyclic voltammetric peaks at about -0.28 V versus saturated calomel electrode (SCE) in pH 5.5 buffers, respectively, characteristic of the heme Fe(III)/Fe(II) redox couples, indicating enhanced electron transfer between the proteins and PG electrodes in a gluten film environment. The protein-gluten hydrogel films showed excellent stability. Positions of Soret absorption band of protein-gluten films suggested that the heme proteins kept their secondary structure similar to their native state in the films in the medium pH range. The heme proteins in gluten films were act as a biologic catalyst to catalyze reduction of oxygen or hydrogen peroxide. The voltammetric or amperometric responses of H{sub 2}O{sub 2} at the protein-gluten film electrodes could be used to determine the concentration of H{sub 2}O{sub 2} in solution.

  17. Modified gold surfaces by 6-(ferrocenyl)hexanethiol/dendrimer/gold nanoparticles as a platform for the mediated biosensing applications

    Energy Technology Data Exchange (ETDEWEB)

    Karadag, Murat; Geyik, Caner; Demirkol, Dilek Odaci [Ege University, Faculty of Science, Biochemistry Department, 35100 Bornova-Izmir (Turkey); Ertas, F. Nil [Ege University, Faculty of Science, Chemistry Department, 35100, Bornova-Izmir (Turkey); Timur, Suna, E-mail: suna.timur@ege.edu.tr [Ege University, Faculty of Science, Biochemistry Department, 35100 Bornova-Izmir (Turkey)

    2013-03-01

    An electrochemical biosensor mediated by using 6-(Ferrocenyl) hexanethiol (FcSH) was fabricated by construction of gold nanoparticles (AuNPs) on the surface of polyamidoamine dendrimer (PAMAM) modified gold electrode. Glucose oxidase (GOx) was used as a model enzyme and was immobilized onto the gold surface forming a self assembled monolayer via FcSH and cysteamine. Cyclic voltammetry and amperometry were used for the characterization of electrochemical response towards glucose substrate. Following the optimization of medium pH, enzyme loading, AuNP and FcSH amount, the linear range for the glucose was studied and found as 1.0 to 5.0 mM with the detection limit (LOD) of 0.6 mM according to S/N = 3. Finally, the proposed Au/AuNP/(FcSH + Cyst)/PAMAM/GOx biosensor was successfully applied for the glucose analysis in beverages, and the results were compared with those obtained by HPLC. Highlights: Black-Right-Pointing-Pointer Immobilized mediator in SAM layer and dendrimeric structure to expand surface area. Black-Right-Pointing-Pointer Au nanoparticles for enhanced electron transfer. Black-Right-Pointing-Pointer Satisfactory Limit of Detection with 0.6 mM.

  18. Electrocatalytic oxidation and determination of insulin at nickel oxide nanoparticles-multiwalled carbon nanotube modified screen printed electrode.

    Science.gov (United States)

    Rafiee, Banafsheh; Fakhari, Ali Reza

    2013-08-15

    Nickel oxide nanoparticles modified nafion-multiwalled carbon nanotubes screen printed electrode (NiONPs/Nafion-MWCNTs/SPE) were prepared using pulsed electrodeposition of NiONPs on the MWCNTs/SPE surface. The size, distribution and structure of the NiONPs/Nafion-MWCNTs were characterized by transmission electron microscopy (TEM) and x-ray diffraction (XRD) and also the results show that NiO nanoparticles were homogeneously electrodeposited on the surfaces of MWCNTs. Also, the electrochemical behavior of NiONPs/Nafion-MWCNTs composites in aqueous alkaline solutions of insulin was studied by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS). It was found that the prepared nanoparticles have excellent electrocatalytic activity towards insulin oxidation due to special properties of NiO nanoparticles. Cyclic voltammetric studies showed that the NiONPs/Nafion-MWCNTs film modified SPE, lowers the overpotentials and improves electrochemical behavior of insulin oxidation, as compared to the bare SPE. Amperometry was also used to evaluate the analytical performance of modified electrode in the quantitation of insulin. Excellent analytical features, including high sensitivity (1.83 μA/μM), low detection limit (6.1 nM) and satisfactory dynamic range (20.0-260.0 nM), were achieved under optimized conditions. Moreover, these sensors show good repeatability and a high stability after a while or successive potential cycling.

  19. Simple determination of the CO2/O2 specificity of Ribulose-1,5-bisphosphate carboxylase/oxygenase by the specific radioactivity of [14C] glycerate 3-phosphate

    International Nuclear Information System (INIS)

    A new method is presented for measurement of the CO2/O2 specificity factor of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). The [14C]3-phosphoglycerate (PGA) from the Rubisco carboxylase reaction and its dilution by the Rubisco oxygenase reaction was monitored by directly measuring the specific radioactivity of PGA. 14CO2 fixation with Rubisco occurred under two reaction conditions: carboxylase with oxygenase with 40 micromolar CO2 in O2-saturated water and carboxylase only with 160 micromolar CO2 under N2. Detection of the specific radioactivity used the amount of PGA as obtained from the peak area, which was determined by pulsed amperometry following separation by high-performance anion exchange chromatography and the radioactive counts of the [14C]PGA in the same peak. The specificity factor of Rubisco from spinach (Spinacia oleracea L.) (93 ± 4), from the green alga Chlamydomonas reinhardtii (66 ± 1), and from the photosynthetic bacterium Rhodospirillum rubrum (13) were comparable with the published values measured by different methods

  20. A Facile Electrochemical Preparation of Reduced Graphene Oxide@Polydopamine Composite: A Novel Electrochemical Sensing Platform for Amperometric Detection of Chlorpromazine

    Science.gov (United States)

    Palanisamy, Selvakumar; Thirumalraj, Balamurugan; Chen, Shen-Ming; Wang, Yi-Ting; Velusamy, Vijayalakshmi; Ramaraj, Sayee Kannan

    2016-01-01

    We report a novel and sensitive amperometric sensor for chlorpromazine (CPZ) based on reduced graphene oxide (RGO) and polydopamine (PDA) composite modified glassy carbon electrode. The RGO@PDA composite was prepared by electrochemical reduction of graphene oxide (GO) with PDA. The RGO@PDA composite modified electrode shows an excellent electro-oxidation behavior to CPZ when compared with other modified electrodes such as GO, RGO and GO@PDA. Amperometric i-t method was used for the determination of CPZ. Amperometry result shows that the RGO@PDA composite detects CPZ in a linear range from 0.03 to 967.6 μM. The sensor exhibits a low detection limit of 0.0018 μM with the analytical sensitivity of 3.63 ± 0.3 μAμM–1 cm–2. The RGO@PDA composite shows its high selectivity towards CPZ in the presence of potentially interfering drugs such as metronidazole, phenobarbital, chlorpheniramine maleate, pyridoxine and riboflavin. In addition, the fabricated RGO@PDA modified electrode showed an appropriate recovery towards CPZ in the pharmaceutical tablets. PMID:27650697

  1. RCAN1 regulates vesicle recycling and quantal release kinetics via effects on calcineurin activity.

    Science.gov (United States)

    Zanin, Mark P; Mackenzie, Kimberly D; Peiris, Heshan; Pritchard, Melanie A; Keating, Damien J

    2013-02-01

    We have previously shown that Regulator of Calcineurin 1 (RCAN1) regulates multiple stages of vesicle exocytosis. However, the mechanisms by which RCAN1 affects secretory vesicle exocytosis and quantal release kinetics remain unknown. Here, we use carbon fibre amperometry to detect exocytosis from chromaffin cells and identify these underlying mechanisms. We observe reduced exocytosis with repeated stimulations in chromaffin cells over-expressing RCAN1 (RCAN1(ox)), but not in wild-type (WT) cells, indicating a negative effect of RCAN1 on vesicle recycling and endocytosis. Acute exposure to calcineurin inhibitors, cyclosporine A and FK-506, replicates this effect in WT cells but has no additional effect in RCAN1(ox) cells. When we chronically expose WT cells to cyclosporine A and FK-506 we find that catecholamine release per vesicle and pre-spike foot (PSF) signal parameters are decreased, similar to that in RCAN1(ox) cells. Inhibiting calcineurin activity in RCAN1(ox) cells has no additional effect on the amount of catecholamine release per vesicle but further reduces PSF signal parameters. Although electron microscopy studies indicate these changes are not because of altered vesicle number or distribution in RCAN1(ox) cells, the smaller vesicle and dense core size we observe in RCAN1(ox) cells may underlie the reduced quantal release in these cells. Thus, our results indicate that RCAN1 most likely affects vesicle recycling and quantal release kinetics via the inhibition of calcineurin activity.

  2. A lactate electrochemical biosensor with a titanate nanotube as direct electron transfer promoter

    Energy Technology Data Exchange (ETDEWEB)

    Yang Mingli; Wang Jin; Li Huaqing; Wu Nianqiang Nick [Department of Mechanical and Aerospace Engineering, WV Nano, West Virginia University, Morgantown, WV 26506-6106 (United States); Zheng Jianguo [Zeiss Center of Excellence and Materials Characterization Center (MC2), California Institute for Communication and Information Technology, University of California, Irvine, CA 92697 (United States)], E-mail: nick.wu@mail.wvu.edu

    2008-02-20

    Hydrogen titanate (H{sub 2}Ti{sub 3}O{sub 7}) nanotubes (TNTs) have been synthesized by a one-step hydrothermal processing. Lactate oxidase (LOx) enzyme has been immobilized on the three-dimensional porous TNT network to make an electrochemical biosensor for lactate detection. Cyclic voltammetry and amperometry tests reveal that the LOx enzyme, which is supported on TNTs, maintains their substrate-specific catalytic activity. The nanotubes offer the pathway for direct electron transfer between the electrode surface and the active redox centers of LOx, which enables the biosensor to operate at a low working potential and to avoid the influence of the presence of O{sub 2} on the amperometric current response. The biosensor exhibits a sensitivity of 0.24 {mu}A cm{sup -2} mM{sup -1}, a 90% response time of 5 s, and a linear response in the range from 0.5 to 14 mM and the redox center of enzyme obviates the need of redox mediators for electrochemical enzymatic sensors, which is attractive for the development of reagentless biosensors.

  3. Electrochemical determination of cysteine based on conducting polymers/gold nanoparticles hybrid nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Hsiao, Ya-Ping; Su, Wan-Yu; Cheng, Jin-Ru [Department of Applied Chemistry, National Chi Nan University, Puli, Nantou Hsien 545, Taiwan (China); Cheng, Shu-Hua, E-mail: shcheng@ncnu.edu.t [Department of Applied Chemistry, National Chi Nan University, Puli, Nantou Hsien 545, Taiwan (China)

    2011-08-01

    In this study, a hybrid nanocomposite consisting of a conducting polymer and gold nanoparticles (AuNPs) is fabricated onto a screen-printed carbon electrode (SPCE). A thin layer of poly(3,4-ethylenedioxythiophene) (PEDOT) is coated electrochemically on a bare SPCE; then, the nano-sized AuNPs are embedded by electrochemical deposition. The resultant SPCE/PEDOT/AuNPs-modified electrode is characterized by electrochemical methods, field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The SPCE/PEDOT/AuNPs-modified electrode possesses great catalytic activity for the oxidation of cysteine in various pH buffer solutions (pH 2.0-8.0). The selectivity of the method is demonstrated by the separation of the oxidation peaks at up to 240 mV for cysteine and glutathione in pH 6.0 buffer solutions. The effects of the oxidizable interferences are also investigated. Flow-injection amperometry is performed for 0.5-200 {mu}M of cysteine in pH 4.0 buffer solutions, and a linear calibration plot with a slope of 0.115 {mu}A/{mu}M is obtained. The detection limit (S/N = 3) is 0.05 {mu}M. Additionally, the proposed methods obtain satisfactory results in the detection of cysteine-containing medicine samples.

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

    Science.gov (United States)

    Vaidyanathan, Settu; Cherng, Jong-Yuh; Sun, An-Cheng; Chen, Chien-Yen

    2016-01-01

    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. PMID:27409615

  5. Highly sensitive voltammetric sensor based on immobilization of bisphosphoramidate-derivative and quantum dots onto multi-walled carbon nanotubes modified gold electrode for the electrocatalytic determination of olanzapine.

    Science.gov (United States)

    Mohammadi-Behzad, Leila; Gholivand, Mohammad Bagher; Shamsipur, Mojtaba; Gholivand, Khodayar; Barati, Ali; Gholami, Akram

    2016-03-01

    In the present paper, a new bisphosphoramidate derivative compound, 1, 4-bis(N-methyl)-benzene-bis(N-phenyl, N-benzoylphosphoramidate) (BMBPBP), was synthesized and used as a mediator for the electrocatalytic oxidation of olanzapine. The electro-oxidation of olanzapine at the surface of the BMBPBP/CdS-quantum dots/multi-walled carbon nanotubes (BMBPBP/CdS-QDs/MWCNTs) modified gold electrode was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. This sensor showed an excellent electrocatalytic oxidation activity toward olanzapine at less positive potential, pronounced current response, and good sensitivity. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) were determined for olanzapine oxidation, using the electrochemical approaches. Surface morphology and electrochemical properties of the prepared modified electrode were investigated by scanning electron microscopy (SEM), cyclic voltammetry and electrochemical impedance spectroscopy techniques. The hydrodynamic amperometry at rotating modified electrode at constant potential versus reference electrode was used for detection of olanzapine. Under optimized conditions, the calibration plot was linear in the concentration range of 20 nM to 100 μM and detection limit was found to be 6 nM. The proposed method was successfully applied to the determination of olanzapine in pharmaceuticals and human serum samples. PMID:26706508

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

    Science.gov (United States)

    Vaidyanathan, Settu; Cherng, Jong-Yuh; Sun, An-Cheng; Chen, Chien-Yen

    2016-01-01

    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 Ni(2+)/Ni(3+) 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. PMID:27409615

  7. Miniaturized neural sensing and optogenetic stimulation system for behavioral studies in the rat

    Science.gov (United States)

    Kim, Min Hyuck; Nam, Ilho; Ryu, Youngki; Wellman, Laurie W.; Sanford, Larry D.; Yoon, Hargsoon

    2015-04-01

    Real time sensing of localized electrophysiological and neurochemical signals associated with spontaneous and evoked neural activity is critically important for understanding neural networks in the brain. Our goal is to enhance the functionality and flexibility of a neural sensing and stimulation system for the observation of brain activity that will enable better understanding from the level of individual cells to that of global structures. We have thus developed a miniaturized electronic system for in-vivo neurotransmitter sensing and optogenetic stimulation amenable to behavioral studies in the rat. The system contains a potentiostat, a data acquisition unit, a control unit, and a wireless data transfer unit. For the potentiostat, we applied embedded op-amps to build single potential amperometry for electrochemical sensing of dopamine. A light emitting diode is controlled by a microcontroller and pulse width modulation utilized to control optogenetic stimulation within a sub-millisecond level. In addition, this proto-typed electronic system contains a Bluetooth module for wireless data communication. In the future, an application-specific integrated circuit (ASIC) will be designed for further miniaturization of the system.

  8. Physical techniques for the study of exocytosis in isolated cells.

    Science.gov (United States)

    Henry, J P; Darchen, F; Cribier, S

    1998-01-01

    Membrane traffic is an important aspect of cell biology which implies shuttle vesicles and multiple binding/fusion events. In spite of rapid progress at the biochemical level, the mechanism of fusion is still not understood. A detailed physical description of the phenomenon is possible at the level of the plasma membrane where secretory vesicles fuse with the cell membrane, a process known as exocytosis. This process is specially active in neurons (release of neurotransmitter) and in endocrine cells (release of hormones), where exocytosis is tightly regulated. Among the biophysical techniques developed, cell membrane capacitance measurements by the technique of patch-clamp and amperometry of the oxidizable secretory products have resulted in interesting information. These techniques have described the initial fusion pore, its fluctuations, the efflux of material through the pore and its irreversible expansion. Optical techniques, using bioluminescent and fluorescent probes are also in progress. For instance, the dye FM 1-43 binds to but is not translocated through biological membranes and it has been used to measure membrane surface, as done by capacitance measurement. Evanescent wave fluorescence microscopy has been recently introduced to analyse the behaviour of secretory granules in the vicinity of the plasma membrane. PMID:9782378

  9. Extracellular ATP stimulates exocytosis via localized Ca(2+) release from acidic stores in rat pancreatic beta cells.

    Science.gov (United States)

    Xie, Li; Zhang, Ming; Zhou, Wei; Wu, Zhengxing; Ding, Jiuping; Chen, Liangyi; Xu, Tao

    2006-04-01

    Three different methods, membrane capacitance (C(m)) measurement, amperometry and FM dye labeling were used to investigate the role of extracellular ATP in insulin secretion from rat pancreatic beta cells. We found that extracellular application of ATP mobilized intracellular Ca(2+) stores and synchronously triggered vigorous exocytosis. No influence of ATP on the readily releasable pool of vesicles was observed, which argues against a direct modulation of the secretory machinery at a level downstream of Ca(2+) elevation. The stimulatory effects of ATP were greatly reduced by intracellular perfusion of BAPTA but not EGTA, suggesting a close spatial association of fusion sites with intracellular Ca(2+) releasing sites. ATP-induced Ca(2+) transients and exocytosis were not blocked by thapsigargin (TG), by a ryanodine receptor antagonist or by dissipation of pH in acidic stores by monensin alone, but they were greatly attenuated by IP(3) receptor inhibition as well as ionomycin plus monensin, suggesting involvement of IP(3)-sensitive acidic Ca(2+) stores. Taken together, our data suggest that extracellular ATP triggers exocytosis by mobilizing spatially limited acidic Ca(2+) stores through IP(3) receptors. This mechanism may explain how insulin secretion from the pancreas is coordinated through diffusible ATP that is co-released with insulin. PMID:16536741

  10. Facile fabrication of 3D layer-by-layer graphene-gold nanorod hybrid architecture for hydrogen peroxide based electrochemical biosensor

    Directory of Open Access Journals (Sweden)

    Chenming Xue

    2015-03-01

    Full Text Available Three-dimensional (3D layer-by-layer graphene-gold nanorod (GNR architecture has been constructed. The resulting hybrid nanomaterials’ architecture has been tested for detecting hydrogen peroxide (H2O2 through the electrocatalytic reaction on a three electrode disposable biosensor platform. Cyclic voltammetry and amperometry were used to characterize and assess the performance of the biosensor. The 3D layer-by-layer modified electrode exhibited the highest sensitivity compared to the active carbon, graphene-oxide, cysteine-graphene oxide and GNR coated electrodes. This research explored the feasibility of using the 3D hybrid graphene-GNR as a template for biosensor. The 3D hybrid structure exhibited higher sensitivity than GNRs alone. SEM showed the explanation that GNRs had self-aggregates reducing the contact surface area when coated on the active carbon electrode, while there were no such aggregates in the 3D structure, and TEM illustrated that GNRs dispersed well in the 3D structure. This research demonstrated a better way to prepare well-separated metal nanoparticles by using the 3D layer-by-layer structure. Consequently, other single and bi-metallic metal nanoparticles could be incorporated into such structure. As a practical example, 3D layer-by-layer nanomaterials modified active carbon electrode was used for detecting glucose showing very good sensitivity and minimum interference by ascorbic acid and uric acid in test solution, which indicated a good selectivity of the biosensor as well.

  11. a High-Performance Glucose Biosensor Based on Zno Nanorod Arrays Modified with AU Nanoparticles

    Science.gov (United States)

    Zhang, Gong; Lei, Yang; Yan, Xiaoqin

    2012-08-01

    An amperometric glucose biosensor based on vertically aligned ZnO nanorod (NR) arrays modified with Au nanoparticles (NPs) was constructed in a channel-limited way. Au NPs with diameters in the range of 8-10 nm have been successfully synthesized by photoreduction method and were uniformly loaded onto the surface of ZnO NRs that was hydrothermally deposited on the Fluorine doped SnO2 conductive glass (FTO) via electrostatic self-assembly technique. The morphology and structure of Au/ZnO NR arrays were characterized by field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectrum analyzer (XPS). The electrocatalytic properties of glucose oxidase (GOD)- immobilized Au/ZnO NR arrays were evaluated by amperometry. Compared with the biosensor based on ZnO NR arrays, the resulting Au/ZnO NR arrays modified biosensor exhibited an expanded linear range from 3 μM to 3 mM with the detection limit of 30 nM and a smaller Michaelis-Menten constant of 0.7836 mM. All these results suggest that the Au NPs can greatly improve the biosensing properties of ZnO NR arrays and therefore Au/ZnO NR arrays provide a promising material for the biosensor designs and other biological applications.

  12. Glucose biosensor based on multisegment nanowires exhibiting reversible magnetic control.

    Science.gov (United States)

    Gerola, Gislaine P; Takahashi, Giovanna S; Perez, Geraldo G; Recco, Lucas C; Pedrosa, Valber A

    2014-11-01

    We describe the amperometric detection of glucose using oriented nanowires with magnetic switching of the bioelectrochemical process. The fabrication process of the nanowires was prepared through controlled nucleation and growth during a stepwise electrochemical deposition, and it was characterized using scanning electron microscopy. Cyclic voltammetry and amperometry were used to study the magnetoswitchable property; this control was accomplished by changing the surface orientation of nanowires. Under the optimal condition, the amperometric response was also linear up to a glucose concentration of 0.1-16.0 mmol L(-1) with a sensitivity of 81 μA mM(-1). The detection limit was estimated for 4.8×10(-8) mol L(-1), defined from a signal/noise ratio of 3. It also exhibits good reproducibility and high selectivity with insignificant interference from ascorbic acid, acetoaminophen, and uric acid. The resulting biosensor was applied to detect the blood sugar in human serum samples without any pretreatment, and the results were comparatively in agreement with the clinical assay. PMID:25127595

  13. Co-immobilization of gold nanoparticles with glucose oxidase to improve bioelectrocatalytic glucose oxidation

    Science.gov (United States)

    Aquino Neto, Sidney; Milton, Ross D.; Crepaldi, Laís B.; Hickey, David P.; de Andrade, Adalgisa R.; Minteer, Shelley D.

    2015-07-01

    Recently, there has been much effort in developing metal nanoparticle catalysts for fuel oxidation, as well as the development of enzymatic bioelectrocatalysts for fuel oxidation. However, there has been little study of the synergy of hybrid electrocatalytic systems. We report the preparation of hybrid bioanodes based on Au nanoparticles supported on multi-walled carbon nanotubes (MWCNTs) co-immobilized with glucose oxidase (GOx). Mediated electron transfer was achieved by two strategies: ferrocene entrapped within polypyrrole and a ferrocene-modified linear poly(ethylenimine) (Fc-LPEI) redox polymer. Electrochemical characterization of the Au nanoparticles supported on MWCNTs indicate that this catalyst exhibits an electrocatalytic response for glucose even in acidic conditions. Using the redox polymer Fc-LPEI as the mediator, voltammetric and amperometric data demonstrated that these bioanodes can efficiently achieve mediated electron transfer and also indicated higher catalytic currents with the hybrid bioelectrode. From the amperometry, the maximum current density (Jmax) achieved with the hybrid bioelectrode was 615 ± 39 μA cm-2, whereas the bioanode employing GOx only achieved a Jmax of 409 ± 26 μA cm-2. Biofuel cell tests are consistent with the electrochemical characterization, thus confirming that the addition of the metallic species into the bioanode structure can improve fuel oxidation and consequently, improve the power generated by the system.

  14. An interference-free glucose biosensor based on an anionic redox polymer-mediated enzymatic oxidation of glucose.

    Science.gov (United States)

    Deng, Huimin; Shen, Wei; Gao, Zhiqiang

    2013-07-22

    Herein a novel strategy for the construction of an amperometric biosensor for highly sensitive and selective determination of glucose is described. The biosensor is made of a biocomposite membrane of glucose oxidase (GOx) and an Os(bpy)2 (bpy=2,2'-bipyridine)-based anionic redox polymer (Os-RP) mediator. The biosensor is fabricated through the co-immobilization of GOx and the Os-RP on the surface of a glassy carbon electrode by a simple one-step chemical crosslinking process. The crosslinked Os-RP/GOx composite membrane shows excellent catalytic activity toward the oxidation of glucose. Under optimal experimental conditions, a linear correlation between the oxidation current of glucose in amperometry at 0.25 V (vs. Ag/AgCl) and glucose concentration up to 10 mM with a sensitivity of 16.5 μA mM(-1) cm(-2) and a response time glucose in the presence of ascorbic acid and uric acid. The low hydrophobicity of the composite membrane also effectively retards the transport of molecular oxygen within the membrane. PMID:23325705

  15. Entrapment of both glucose oxidase and peroxidase in regenerated silk fibroin membraneCharacterization of the membrane structure and its application to an amperometric glucose sensor employing methylene green as an electron transfer mediato.

    Science.gov (United States)

    Liu, Y; Liu, H; Qian, J; Deng, J; Yu, T

    1996-04-01

    Two enzmyes, glucose oxidase and peroxidase, were for the first time simultaneously immobilized in regenerated silk fibroin membrane. The structure and morphology of the regenerated silk fibroin membrane containing both glucose oxidase and peroxidase were investigated with IR spectra and SEM. The bienzymes do not change the structures of the regenerated silk fibroin in the membrane, which has an islands-sea structure. For the first time, an amperometric methylene green mediating sensor for glucose based on co-immobilization of both glucose oxidase and peroxidase in regenerated silk fibroin was constructed. Cyclic voltammetry and amperometry were used to test the suitability of methylene green shuttling electrons between peroxidase and the glassy carbon electrode. The bienzyme-based system offers fast response and high sensitivity of the sensor to glucose. The effects of pH, temperature, and the concentration of the mediator on the response current were evaluated, and the dependence of the Michaelis-Menten constant K(m)(app) on the concentration of the mediator was investigated. PMID:15045461

  16. A Fast, Sensitive and Label Free Electrochemical DNA Sensor

    International Nuclear Information System (INIS)

    A label free and sensitive DNA/RNA silicon based electrochemical microsensor array was developed by using thin film of the conducting polymer polypyrrole doped with an oligonucleotide probe. The electrochemical potential pulse amperometry technique was used for a biowarfare pathogen target DNA detection. The electrical potential assistanted DNA hybridisation method was applied. The sensor signal was increased by increasing the electrical potential assistanted DNA hybridisation time. It was possible to detect 0.34pmol and 0.072fmol of complementary oligonucleotide target in 0.1ml in seconds by using unpolished and polished gold electrode respectively. The probe preparation was also in seconds time, comparing indirect electrochemical DNA sensor, it has a fast sensor preparation as well as sensor response and label free advantages. The silicon microfabrication technique was used for this sensor array fabrication, which holds the potential to integrate with sensor electrical circuits. The conducting polymer polypyrrole was electrochemically deposited on each electrode respectively which has a possibility to dope the different DNA probe into the individual electrode to form a sensor array

  17. Rapid Prototyping of a High Sensitivity Graphene Based Glucose Sensor Strip

    Science.gov (United States)

    Tehrani, Farshad; Reiner, Lisa; Bavarian, Behzad

    2015-01-01

    A rapid prototyping of an inexpensive, disposable graphene and copper nanocomposite sensor strip using polymeric flexible substrate for highly sensitive and selective nonenzymatic glucose detection has been developed and tested for direct oxidization of glucose. The CuNPs were electrochemically deposited on to the graphene sheets to improve electron transfer rates and to enhance electrocatalytic activity toward glucose. The graphene based electrode with CuNPs demonstrated a high degree of sensitivity (1101.3±56 μA/mM.cm2), excellent selectivity (without an interference with Ascorbic Acid, Uric Acid, Dopamine, and Acetaminophen), good stability with a linear response to glucose ranging from 0.1 mM to 0.6 mM concentration, and detection limits of 0.025 mM to 0.9 mM. Characterization of the electrodes was performed by scanning electron microscopy (FESEM and SEM). The electrochemical properties of the modified graphene electrodes were inspected by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry. PMID:26678700

  18. Comparative study of label-free electrochemical immunoassay on various gold nanostructures

    Science.gov (United States)

    Rafique, S.; Gao, C.; Li, C. M.; Bhatti, A. S.

    2013-10-01

    Electrochemical methods such as amperometry and impedance spectroscopy provide the feasibility of label-free immunoassay. However, the performance of electrochemical interfaces varies with the shape of gold nanostructures. In the present work three types of gold nanostructures including pyramid, spherical, and rod-like nanostructures were electrochemically synthesized on the gold electrode and were further transformed into immunosensor by covalent binding of antibodies. As a model protein, a cancer biomarker, Carcinoembryonic Antigen (CEA) was detected using amperometric and impedimetric techniques on three nanostructured electrodes, which enabled to evaluate and compare the immunoassay's performance. It was found that all three immunosensors showed improved linear electrochemical response to the concentration of CEA compared to bare Au electrode. Among all the spherical gold nanostructure based immunosensors displayed superior performance. Under optimal condition, the immunosensors exhibited a limit of detection of 4.1 pg ml-1 over a concentration range of five orders of magnitude. This paper emphasizes that fine control over the geometry of nanostructures is essentially important for high-performance electrochemical immunoassay.

  19. Metabolic measurements in cell culture and tissue constructs

    Science.gov (United States)

    Rolfe, P.

    2008-10-01

    This paper concerns the study and use of biological cells in which there is a need for sensors and assemblies for the measurement of a diverse range of physical and chemical variables. In this field cell culture is used for basic research and for applications such as protein and drug synthesis, and in cell, tissue and organ engineering. Metabolic processes are fundamental to cell behaviour and must therefore be monitored reliably. Basic metabolic studies measure the transport of oxygen, glucose, carbon dioxide, lactic acid to, from, or within cells, whilst more advanced research requires examination of energy storage and utilisation. Assemblies are designed to incorporate bioreactor functions for cell culture together with appropriate sensing devices. Oxygen consumption by populations of cells is achieved in a flowthrough assembly that incorporates O2 micro-sensors based on either amperometry or fluorescence. Measurements in single cell are possible with intra-cellular fluorophores acting as biosensors together with optical stimulation and detection. Near infra-red spectroscopy (NIRS) is used for analysis within culture fluid, for example for estimation of glucose levels, as well as within cell populations, for example to study the respiratory enzymes.Â#

  20. High-Performance Bioinstrumentation for Real-Time Neuroelectrochemical Traumatic Brain Injury Monitoring

    Science.gov (United States)

    Papadimitriou, Konstantinos I.; Wang, Chu; Rogers, Michelle L.; Gowers, Sally A. N.; Leong, Chi L.; Boutelle, Martyn G.; Drakakis, Emmanuel M.

    2016-01-01

    Traumatic brain injury (TBI) has been identified as an important cause of death and severe disability in all age groups and particularly in children and young adults. Central to TBIs devastation is a delayed secondary injury that occurs in 30–40% of TBI patients each year, while they are in the hospital Intensive Care Unit (ICU). Secondary injuries reduce survival rate after TBI and usually occur within 7 days post-injury. State-of-art monitoring of secondary brain injuries benefits from the acquisition of high-quality and time-aligned electrical data i.e., ElectroCorticoGraphy (ECoG) recorded by means of strip electrodes placed on the brains surface, and neurochemical data obtained via rapid sampling microdialysis and microfluidics-based biosensors measuring brain tissue levels of glucose, lactate and potassium. This article progresses the field of multi-modal monitoring of the injured human brain by presenting the design and realization of a new, compact, medical-grade amperometry, potentiometry and ECoG recording bioinstrumentation. Our combined TBI instrument enables the high-precision, real-time neuroelectrochemical monitoring of TBI patients, who have undergone craniotomy neurosurgery and are treated sedated in the ICU. Electrical and neurochemical test measurements are presented, confirming the high-performance of the reported TBI bioinstrumentation. PMID:27242477

  1. Simultaneous Voltammetric/Amperometric Determination of Sulfide and Nitrite in Water at BDD Electrode

    Directory of Open Access Journals (Sweden)

    Anamaria Baciu

    2015-06-01

    Full Text Available This work reported new voltammetric/amperometric-based protocols using a commercial boron-doped diamond (BDD electrode for simple and fast simultaneous detection of sulfide and nitrite from water. Square-wave voltammetry operated under the optimized working conditions of 0.01 V step potential, 0.5 V modulation amplitude and 10 Hz frequency allowed achieving the best electroanalytical parameters for the simultaneous detection of nitrite and sulfide. For practical in-field detection applications, the multiple-pulsed amperometry technique was operated under optimized conditions, i.e., −0.5 V/SCE for a duration of 0.3 s as conditioning step, +0.85 V/SCE for a duration of 3 s that assure the sulfide oxidation and +1.25 V/SCE for a duration of 0.3 s, where the nitrite oxidation occurred, which allowed the simultaneously detection of sulfide and nitrite without interference between them. Good accuracy was found for this protocol in comparison with standardized methods for each anion. Also, no interference effect was found for the cation and anion species, which are common in the water matrix.

  2. Preparation,Electrochemical Behavior and Electrocatalytic Activity of a Copper Hexacyanoferrate Modified Ceramic Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    YU,Hao; ZHENG,Jian-Bin

    2007-01-01

    A copper hexacyanoferrate modified ceramic carbon electrode(CuHCF/CCE)had been prepared by two-step sol-gel technique and characterized using electrochemical methods.The resulting modified electrode showed a pair of well-defined surface waves in the potential range of 0.40 to 1.0 V with the formal potential of 0.682 V (vs.SCE)in 0.050 mol·dm-3 HOAc-NaOAc buffer containing 0.30 mol·dm-3 KCI.The charge transfer coefficient (α) and charge transfer rate constant(Ks)for the modified electrode were calculated.The electrocatalytic activity of this modified electrode to hydrazine was also investigated,and chronoamperometry was exploited to conveniently determine the diffusion coefficient(D)of hydrazine in solution and the catalytic rate constant(Kcat).Finally,hydrazine was determined with amperometry using the resulting modified electrode.The calibration plot for hydrazine determination was linear in 3.0×10-6-7.5×10-4 mol·dm-3 with the detection limit of 8.0×10-7 mol·dm-3.This modified electrode had some advantages over the modified film electrodes constructed by the conventional methods,such as renewable surface,good long-term stability,excellent catalytic activity and short response time to hydrazine.

  3. Electrochemical Determination of Chlorpyrifos on a Nano-TiO₂Cellulose Acetate Composite Modified Glassy Carbon Electrode.

    Science.gov (United States)

    Kumaravel, Ammasai; Chandrasekaran, Maruthai

    2015-07-15

    A rapid and simple method of determination of chlorpyrifos is important in environmental monitoring and quality control. Electrochemical methods for the determination of pesticides are fast, sensitive, reproducible, and cost-effective. The key factor in electrochemical methods is the choice of suitable electrode materials. The electrode materials should have good stability, reproducibility, more sensitivity, and easy method of preparation. Mercury-based electrodes have been widely used for the determination of chlorpyrifos. From an environmental point of view mercury cannot be used. In this study a biocompatible nano-TiO2/cellulose acetate modified glassy carbon electrode was prepared by a simple method and used for the electrochemical sensing of chlorpyrifos in aqueous methanolic solution. Electroanalytical techniques such as cyclic voltammetry, differential pulse voltammetry, and amperometry were used in this work. This electrode showed very good stability, reproducibility, and sensitivity. A well-defined peak was obtained for the reduction of chlorpyrifos in cyclic voltammetry and differential pulse voltammetry. A smooth noise-free current response was obtained in amperometric analysis. The peak current obtained was proportional to the concentration of chlorpyrifos and was used to determine the unknown concentration of chlorpyrifos in the samples. Analytical parameters such as LOD, LOQ, and linear range were estimated. Analysis of real samples was also carried out. The results were validated through HPLC. This composite electrode can be used as an alternative to mercury electrodes reported in the literature.

  4. Simultaneous Voltammetric/Amperometric Determination of Sulfide and Nitrite in Water at BDD Electrode

    Science.gov (United States)

    Baciu, Anamaria; Ardelean, Magdalena; Pop, Aniela; Pode, Rodica; Manea, Florica

    2015-01-01

    This work reported new voltammetric/amperometric-based protocols using a commercial boron-doped diamond (BDD) electrode for simple and fast simultaneous detection of sulfide and nitrite from water. Square-wave voltammetry operated under the optimized working conditions of 0.01 V step potential, 0.5 V modulation amplitude and 10 Hz frequency allowed achieving the best electroanalytical parameters for the simultaneous detection of nitrite and sulfide. For practical in-field detection applications, the multiple-pulsed amperometry technique was operated under optimized conditions, i.e., −0.5 V/SCE for a duration of 0.3 s as conditioning step, +0.85 V/SCE for a duration of 3 s that assure the sulfide oxidation and +1.25 V/SCE for a duration of 0.3 s, where the nitrite oxidation occurred, which allowed the simultaneously detection of sulfide and nitrite without interference between them. Good accuracy was found for this protocol in comparison with standardized methods for each anion. Also, no interference effect was found for the cation and anion species, which are common in the water matrix. PMID:26102487

  5. Structure-function study of mammalian Munc18-1 and C. elegans UNC-18 implicates domain 3b in the regulation of exocytosis.

    Directory of Open Access Journals (Sweden)

    Margaret E Graham

    Full Text Available Munc18-1 is an essential synaptic protein functioning during multiple stages of the exocytotic process including vesicle recruitment, docking and fusion. These functions require a number of distinct syntaxin-dependent interactions; however, Munc18-1 also regulates vesicle fusion via syntaxin-independent interactions with other exocytotic proteins. Although the structural regions of the Munc18-1 protein involved in closed-conformation syntaxin binding have been thoroughly examined, regions of the protein involved in other interactions are poorly characterised. To investigate this we performed a random transposon mutagenesis, identifying domain 3b of Munc18-1 as a functionally important region of the protein. Transposon insertion in an exposed loop within this domain specifically disrupted Mint1 binding despite leaving affinity for closed conformation syntaxin and binding to the SNARE complex unaffected. The insertion mutation significantly reduced total amounts of exocytosis as measured by carbon fiber amperometry in chromaffin cells. Introduction of the equivalent mutation in UNC-18 in Caenorhabditis elegans also reduced neurotransmitter release as assessed by aldicarb sensitivity. Correlation between the two experimental methods for recording changes in the number of exocytotic events was verified using a previously identified gain of function Munc18-1 mutation E466K (increased exocytosis in chromaffin cells and aldicarb hypersensitivity of C. elegans. These data implicate a novel role for an exposed loop in domain 3b of Munc18-1 in transducing regulation of vesicle fusion independent of closed-conformation syntaxin binding.

  6. Graphene: The Missing Piece for Cancer Diagnosis?

    Science.gov (United States)

    Cruz, Sandra M A; Girão, André F; Gonçalves, Gil; Marques, Paula A A P

    2016-01-01

    This paper reviews recent advances in graphene-based biosensors development in order to obtain smaller and more portable devices with better performance for earlier cancer detection. In fact, the potential of Graphene for sensitive detection and chemical/biological free-label applications results from its exceptional physicochemical properties such as high electrical and thermal conductivity, aspect-ratio, optical transparency and remarkable mechanical and chemical stability. Herein we start by providing a general overview of the types of graphene and its derivatives, briefly describing the synthesis procedure and main properties. It follows the reference to different routes to engineer the graphene surface for sensing applications with organic biomolecules and nanoparticles for the development of advanced biosensing platforms able to detect/quantify the characteristic cancer biomolecules in biological fluids or overexpressed on cancerous cells surface with elevated sensitivity, selectivity and stability. We then describe the application of graphene in optical imaging methods such as photoluminescence and Raman imaging, electrochemical sensors for enzymatic biosensing, DNA sensing, and immunosensing. The bioquantification of cancer biomarkers and cells is finally discussed, particularly electrochemical methods such as voltammetry and amperometry which are generally adopted transducing techniques for the development of graphene based sensors for biosensing due to their simplicity, high sensitivity and low-cost. To close, we discuss the major challenges that graphene based biosensors must overcome in order to reach the necessary standards for the early detection of cancer biomarkers by providing reliable information about the patient disease stage. PMID:26805845

  7. Graphene: The Missing Piece for Cancer Diagnosis?

    Directory of Open Access Journals (Sweden)

    Sandra M. A. Cruz

    2016-01-01

    Full Text Available This paper reviews recent advances in graphene-based biosensors development in order to obtain smaller and more portable devices with better performance for earlier cancer detection. In fact, the potential of Graphene for sensitive detection and chemical/biological free-label applications results from its exceptional physicochemical properties such as high electrical and thermal conductivity, aspect-ratio, optical transparency and remarkable mechanical and chemical stability. Herein we start by providing a general overview of the types of graphene and its derivatives, briefly describing the synthesis procedure and main properties. It follows the reference to different routes to engineer the graphene surface for sensing applications with organic biomolecules and nanoparticles for the development of advanced biosensing platforms able to detect/quantify the characteristic cancer biomolecules in biological fluids or overexpressed on cancerous cells surface with elevated sensitivity, selectivity and stability. We then describe the application of graphene in optical imaging methods such as photoluminescence and Raman imaging, electrochemical sensors for enzymatic biosensing, DNA sensing, and immunosensing. The bioquantification of cancer biomarkers and cells is finally discussed, particularly electrochemical methods such as voltammetry and amperometry which are generally adopted transducing techniques for the development of graphene based sensors for biosensing due to their simplicity, high sensitivity and low-cost. To close, we discuss the major challenges that graphene based biosensors must overcome in order to reach the necessary standards for the early detection of cancer biomarkers by providing reliable information about the patient disease stage.

  8. Voltammetric determination of melatonin using a graphene-based sensor in pharmaceutical products

    Directory of Open Access Journals (Sweden)

    Apetrei IM

    2016-05-01

    Full Text Available Irina Mirela Apetrei,1 Constantin Apetrei2 1Department of Pharmaceutical Sciences, Faculty of Medicine and Pharmacy, 2Department of Chemistry, Physics and Environment, Faculty of Sciences and Environment, “Dunarea de Jos” University of Galati, Galati, Romania Abstract: Melatonin can be sensitively detected in pharmaceuticals by cyclic voltammetry and fixed-potential amperometry using a graphene-based sensor. The sensor characterization of cyclic voltammetry constantly provides high values of electrode active area and heterogeneous rate constant. In optimal conditions, the sensor was applied for the determination of melatonin in different pharmaceutical samples. The sensitivity to melatonin was 0.0371 A M-1, and the limit of detection was 0.87×10-6 M. The data obtained by using the graphene-based sensor for the detection of melatonin in pharmaceutical products were in good agreement with the data provided by the producer. Since no interferences from the excipients were found, using a separation technique was not necessary. Additionally, the low price, ease of handling, small amount of sample, short time per analysis, and possibility of automation are the important advantages that recommend this methodology for quality control of pharmaceuticals. Keywords: electroanalysis, kinetics, chitosan, limit of detection, recovery

  9. Electrochemical Behavior and Determination of Rutin on Modified Carbon Paste Electrodes

    Directory of Open Access Journals (Sweden)

    Pavla Macikova

    2012-01-01

    Full Text Available The performances of ionic liquid (1-hexyl-3-methylimidazolium-bis(trifluoromethylsulfonylimide, IL/CPE and iron phthalocyanine (IP/CPE modified carbon paste electrodes in electroanalytical determinations of rutin were evaluated and compared to the performance of unmodified carbon paste electrode (CPE. Cyclic voltammetry (CV, differential pulse voltammetry (DPV, differential pulse adsorptive stripping voltammetry (DPAdSV, and amperometry were used for rutin analysis. The best current responses of rutin were obtained at pH 4.0 for all tested techniques. IL/CPE electrode was found to perform best with DPAdSV technique, where a detection limit (LOD as low as 5 nmol L-1 of rutin was found. On the other hand, IP/CPE showed itself to be an optimum choice for DPV technique, where LOD of 80 nmol L-1 was obtained. Analytical applicability of newly prepared electrodes was demonstrated on determination of rutin in the model samples and the extracts of buckwheat seeds. To find an optimum method for buckwheat seeds extraction, a boiling water extraction (BWE, Soxhlet extraction (SE, pressurized solvent extraction (PSE, and supercritical fluid extraction (SFE were tested.

  10. Conducting Polymer Nanostructures and Nanocomposites with Carbon Nanotubes: Hierarchical Assembly by Molecular Electrochemistry, Growth Aspects and Property Characterization.

    Science.gov (United States)

    Gupta, Sanju; Price, Carson; Heintzman, Eli

    2016-01-01

    Conducting (or π-conjugated) polymers are promising materials for preparing supramolecular nano-structures and nanocomposites. We report controlled nanostructure syntheses of polypyrrole (PPy) and poylaniline (PANi) via electropolymerization (i.e., in-situ electrochemical anodic oxidation). The density, shape, caliber and thickness of self-assembled PPy micro-containers are regulated by electrochemical potential window for H2 bubbles and number of cyclic voltammetric (potentiodynamic) scans. Likewise, we employed amperometry, chronopotentiometry and potentiodynamic modes using hydrochloric acid as oxidizing agent to prepare PANi nanoparticles and nanotubules. We present our findings from the viewpoint of molecular electrochemistry with growth kinetic aspects yielding mechanistic details (initially forming dimers and oligomers as nucleating agents followed by polymer growth). Also targeted is forming nanocomposites with functionalized single- and multi-walled carbon nanotubes (FSWCNTs and FMWCNTs) as reinforced agent to optimize structural and functional properties. All of these novel nanomaterials are characterized using a range of complementary techniques to establish microscopic structure-property-function relationship. PMID:27398466

  11. Implementation of a new integrated d-lactic acid biosensor in a semiautomatic FIA system for the simultaneous determination of lactic acid enantiomers. Application to the analysis of beer samples.

    Science.gov (United States)

    Vargas, E; Ruiz, M A; Campuzano, S; González de Rivera, G; López-Colino, F; Reviejo, A J; Pingarrón, J M

    2016-05-15

    An integrated amperometric d-lactic acid biosensor involving a gold film deposited by sputtering on a stainless steel disk electrode where the enzymes D-lactic acid dehydrogenase (DLDH) and diaphorase (DP) as well as the redox mediator tetrathiafulvalene (TTF) are coimmobilized by using a dialysis membrane, is reported in this work. Amperometry in stirred solutions at a detection potential of +0.15 V (vs Ag/AgCl reference electrode) provided a linear calibration plot for D-lactic acid over the 1.0×10(-4) to 3.8×10(-3) g L(-1) concentration range, with a limit of detection of 3.1×10(-5) g L(-1). The usefulness of the biosensor was demonstrated by determining D-lactic acid in beer samples with good results. Additionally, the biosensor was implemented together with a commercial L-lactic amperometric biosensor in a semiautomatic flow-injection analysis (FIA) system able to perform a rapid and simple stereo-specific determination of D- and D-lactic without a previous separation step. The operational characteristics of the biosensors under flow conditions were evaluated and its applicability was demonstrated through the simultaneous determination of both enantiomers in beer samples. PMID:26992505

  12. L-glutamate detection using a poly-L-lysine coated ENFET

    Science.gov (United States)

    Braeken, D.; Zhou, C.; Huys, R.; Bartic, C.; De Keersmaecker, K.; Winters, K.; Callewaert, G.; Borghs, G.

    2005-06-01

    Synaptic transmission in neuronal networks occur on a very short time scale and is highly specific. Fast, sensitive and in situ detection of single neuron L-glutamate release is essential for the investigation of these events under physiological or pathophysiological conditions. Up till now, amperometry with enzyme-modified electrodes has extensively been used to monitor extracellular glutamate release. However, due to in situ signal amplification, ENzyme-modified Field-Effect Transistors (ENFETs) have the advantage of preserving sensitivity and a fast response time when scaled down to micrometer dimensions. We have realized a L-GLutamate OxiDase (GLOD) functionalized FET to be used for glutamate detection in neuronal cultures. Effective and reproducible immobilization of GLOD on the FET active area is achieved by using Poly-L-Lysine (PLL) as a loading matrix. PLL plays a dual role in the assay: on the one hand this molecule serves as a platform for obtaining high enzyme loading and on the other hand it benefits the survival of the neuronal network on the active area of the FET. Both PLL and enzyme immobilization were characterised by quartz crystal microbalance measurements. A much higher enzyme loading has been achieved by this approach compared to immobilization methods without PLL. The enzyme coating has proven to be extremely durable as it keeps its activity for at least 3 weeks as monitored by a colorimetric assay. FET characterisation curves and glutamate response curves of the ENFET are presented.

  13. A sensitive, selective and rapid determination of lead(II) ions in real-life samples using an electrochemically reduced graphene oxide-graphite reinforced carbon electrode.

    Science.gov (United States)

    Hamsawahini, Kunashegaran; Sathishkumar, Palanivel; Ahamad, Rahmalan; Yusoff, Abdull Rahim Mohd

    2015-11-01

    In this study, a sensitive and cost-effective electrochemically reduced graphene oxide (ErGO) on graphite reinforced carbon (GRC) was developed for the detection of lead (Pb(II)) ions present in the real-life samples. A film of graphene oxide (GO) was drop-casted on GRC and their electrochemical properties were investigated using cyclic voltammetry (CV), amperometry and square wave voltammetry (SWV). Factors influencing the detection of Pb(II) ions, such as grades of GRC, constant applied cathodic potential (CACP), concentration of hydrochloric acid and drop-casting drying time were optimised. GO is irreversibly reduced in the range of -0.7 V to -1.6 V vs Ag/AgCl (3 M) in acidic condition. The results showed that the reduction behaviour of GO contributed to the high sensitivity of Pb(II) ions detection even at nanomolar level. The ErGO-GRC showed the detection limit of 0.5 nM and linear range of 3-15 nM in HCl (1 M). The developed electrode has potential to be a good candidate for the determination of Pb(II) ions in different aqueous system. The proposed method gives a good recovery rate of Pb(II) ions in real-life water samples such as tap water and river water.

  14. Graphene: The Missing Piece for Cancer Diagnosis?

    Science.gov (United States)

    Cruz, Sandra M A; Girão, André F; Gonçalves, Gil; Marques, Paula A A P

    2016-01-21

    This paper reviews recent advances in graphene-based biosensors development in order to obtain smaller and more portable devices with better performance for earlier cancer detection. In fact, the potential of Graphene for sensitive detection and chemical/biological free-label applications results from its exceptional physicochemical properties such as high electrical and thermal conductivity, aspect-ratio, optical transparency and remarkable mechanical and chemical stability. Herein we start by providing a general overview of the types of graphene and its derivatives, briefly describing the synthesis procedure and main properties. It follows the reference to different routes to engineer the graphene surface for sensing applications with organic biomolecules and nanoparticles for the development of advanced biosensing platforms able to detect/quantify the characteristic cancer biomolecules in biological fluids or overexpressed on cancerous cells surface with elevated sensitivity, selectivity and stability. We then describe the application of graphene in optical imaging methods such as photoluminescence and Raman imaging, electrochemical sensors for enzymatic biosensing, DNA sensing, and immunosensing. The bioquantification of cancer biomarkers and cells is finally discussed, particularly electrochemical methods such as voltammetry and amperometry which are generally adopted transducing techniques for the development of graphene based sensors for biosensing due to their simplicity, high sensitivity and low-cost. To close, we discuss the major challenges that graphene based biosensors must overcome in order to reach the necessary standards for the early detection of cancer biomarkers by providing reliable information about the patient disease stage.

  15. Emerging nanotechnology-based strategies for the identification of microbial pathogenesis.

    Science.gov (United States)

    Kaittanis, Charalambos; Santra, Santimukul; Perez, J Manuel

    2010-03-18

    Infectious diseases are still a major healthcare problem. From food intoxication and contaminated water, to hospital-acquired diseases and pandemics, infectious agents cause disease throughout the world. Despite advancements in pathogens' identification, some of the gold-standard diagnostic methods have limitations, including laborious sample preparation, bulky instrumentation and slow data readout. In addition, new field-deployable diagnostic modalities are urgently needed in first responder and point-of-care applications. Apart from compact, these sensors must be sensitive, specific, robust and fast, in order to facilitate detection of the pathogen even in remote rural areas. Considering these characteristics, researchers have utilized innovative approaches by employing the unique properties of nanomaterials in order to achieve detection of infectious agents, even in complex media like blood. From gold nanoparticles and their plasmonic shifts to iron oxide nanoparticles and changes in magnetic properties, detection of pathogens, toxins, antigens and nucleic acids has been achieved with impressive detection thresholds. Additionally, as bacteria become resistant to antibiotics, nanotechnology has achieved the rapid determination of bacterial drug susceptibility and resistance using novel methods, such as amperometry and magnetic relaxation. Overall, these promising results hint to the adoption of nanotechnology-based diagnostics for the diagnosis of infectious diseases in diverse settings throughout the globe, preventing epidemics and safeguarding human and economic wellness. PMID:19914316

  16. Graphene oxide electrocatalyst on MnO2 air cathode as an efficient electron pump for enhanced oxygen reduction in alkaline solution

    Science.gov (United States)

    Basirun, Wan Jeffrey; Sookhakian, Mehran; Baradaran, Saeid; Endut, Zulkarnain; Mahmoudian, Mohammad Reza; Ebadi, Mehdi; Yousefi, Ramin; Ghadimi, Hanieh; Ahmed, Sohail

    2015-03-01

    Graphene oxide (GO) was deposited on the surface of a MnO2 air cathode by thermal evaporation at 50°C from a GO colloidal suspension. Fourier transformed infrared spectroscopy and field emission scanning electron microscopy confirmed the presence of GO on the MnO2 air cathode (GO-MnO2). Voltammetry and chrono-amperometry showed increased currents for the oxygen reduction reaction (ORR) in 6 M KOH solution for GO-MnO2 compared to the MnO2 cathode. The GO-MnO2 was used as an air cathode in an alkaline tin-air cell and produced a maximum power density of 13 mW cm-2, in contrast to MnO2, which produced a maximum power density of 9.2 mW cm-2. The electrochemical impedance spectroscopy results suggest that the chemical step for the ORR is the rate determining step, as proposed earlier by different researchers. It is suggested that the presence of GO and electrochemically reduced graphene oxide (ERGO) on the MnO2 surface are responsible for the increased rate of this step, whereby GO and ERGO accelerate the process of electron donation to the MnO2 and to adsorbed oxygen atoms.

  17. Lipase immobilized on nanostructured cerium oxide thin film coated on transparent conducting oxide electrode for butyrin sensing

    International Nuclear Information System (INIS)

    Nanostructured cerium oxide (CeO2) thin films were deposited on transparent conducting oxide (TCO) substrate using spray pyrolysis technique with cerium nitrate salt, Ce(NO3)3·6H2O as precursor. Fluorine doped cadmium oxide (CdO:F) thin film prepared using spray pyrolysis technique acts as the TCO film and hence the bare electrode. The structural, morphological and elemental characterizations of the films were carried out using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX) respectively. The diffraction peak positions in XRD confirmed the formation of highly crystalline ceria with cubic structure and FE-SEM images showed uniform adherent films with granular morphology. The band gaps of CeO2 and TCO were found to be 3.2 eV and 2.6 eV respectively. Lipase enzyme was physisorbed on the surface of CeO2/TCO film to form the lipase/nano-CeO2/TCO bioelectrode. Sensing studies were carried out using cyclic voltammetry and amperometry, with lipase/nano-CeO2/TCO as working electrode and tributyrin as substrate. The mediator-free biosensor with nanointerface exhibited excellent linearity (0.33–1.98 mM) with a lowest detection limit of 2 μM with sharp response time of 5 s and a shelf life of about 6 weeks. -- Graphical abstract: Nanostructured cerium oxide thin films were deposited on transparent conducting oxide (TCO) substrate using spray pyrolysis technique. Fluorine doped cadmium oxide (CdO:F) thin film acts as the TCO film and hence the working electrode. Lipase enzyme was physisorbed on the surface of CeO2/TCO film and hence the lipase/nano-CeO2/TCO bioelectrode has been fabricated. Sensing studies were carried out using cyclic voltammetry and amperometry with tributyrin as substrate. The mediator-free biosensor with nanointerface exhibited excellent linearity (0.33–1.98 mM) with a lowest detection limit of 2 μM with sharp response time of 5 s and a shelf life of about 6 weeks. Highlights:

  18. Lipase immobilized on nanostructured cerium oxide thin film coated on transparent conducting oxide electrode for butyrin sensing

    Energy Technology Data Exchange (ETDEWEB)

    Panky, Sreedevi; Thandavan, Kavitha [Centre for Nanotechnology and Advanced Biomaterials (CeNTAB), SASTRA University, Thanjavur 613 401, Tamil Nadu (India); School of Chemical and Biotechnology, SASTRA University, Thanjavur 613 401, Tamil Nadu (India); Sivalingam, Durgajanani [Centre for Nanotechnology and Advanced Biomaterials (CeNTAB), SASTRA University, Thanjavur 613 401, Tamil Nadu (India); School of Electrical and Electronics Engineering, SASTRA University, Thanjavur 613 401, Tamil Nadu (India); Sethuraman, Swaminathan; Krishnan, Uma Maheswari [Centre for Nanotechnology and Advanced Biomaterials (CeNTAB), SASTRA University, Thanjavur 613 401, Tamil Nadu (India); School of Chemical and Biotechnology, SASTRA University, Thanjavur 613 401, Tamil Nadu (India); Jeyaprakash, Beri Gopalakrishnan [Centre for Nanotechnology and Advanced Biomaterials (CeNTAB), SASTRA University, Thanjavur 613 401, Tamil Nadu (India); School of Electrical and Electronics Engineering, SASTRA University, Thanjavur 613 401, Tamil Nadu (India); Rayappan, John Bosco Balaguru, E-mail: rjbosco@ece.sastra.edu [Centre for Nanotechnology and Advanced Biomaterials (CeNTAB), SASTRA University, Thanjavur 613 401, Tamil Nadu (India); School of Electrical and Electronics Engineering, SASTRA University, Thanjavur 613 401, Tamil Nadu (India)

    2013-01-15

    Nanostructured cerium oxide (CeO{sub 2}) thin films were deposited on transparent conducting oxide (TCO) substrate using spray pyrolysis technique with cerium nitrate salt, Ce(NO{sub 3}){sub 3}{center_dot}6H{sub 2}O as precursor. Fluorine doped cadmium oxide (CdO:F) thin film prepared using spray pyrolysis technique acts as the TCO film and hence the bare electrode. The structural, morphological and elemental characterizations of the films were carried out using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX) respectively. The diffraction peak positions in XRD confirmed the formation of highly crystalline ceria with cubic structure and FE-SEM images showed uniform adherent films with granular morphology. The band gaps of CeO{sub 2} and TCO were found to be 3.2 eV and 2.6 eV respectively. Lipase enzyme was physisorbed on the surface of CeO{sub 2}/TCO film to form the lipase/nano-CeO{sub 2}/TCO bioelectrode. Sensing studies were carried out using cyclic voltammetry and amperometry, with lipase/nano-CeO{sub 2}/TCO as working electrode and tributyrin as substrate. The mediator-free biosensor with nanointerface exhibited excellent linearity (0.33-1.98 mM) with a lowest detection limit of 2 {mu}M with sharp response time of 5 s and a shelf life of about 6 weeks. -- Graphical abstract: Nanostructured cerium oxide thin films were deposited on transparent conducting oxide (TCO) substrate using spray pyrolysis technique. Fluorine doped cadmium oxide (CdO:F) thin film acts as the TCO film and hence the working electrode. Lipase enzyme was physisorbed on the surface of CeO{sub 2}/TCO film and hence the lipase/nano-CeO{sub 2}/TCO bioelectrode has been fabricated. Sensing studies were carried out using cyclic voltammetry and amperometry with tributyrin as substrate. The mediator-free biosensor with nanointerface exhibited excellent linearity (0.33-1.98 mM) with a lowest detection limit of 2 {mu}M with sharp

  19. Selective determination of ascorbic acid with a novel hybrid material based 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid and the Dawson type ion [P{sub 2}Mo{sub 18}O{sub 62}]{sup 6-} immobilized on glassy carbon

    Energy Technology Data Exchange (ETDEWEB)

    Ammam, Malika, E-mail: Malika.Ammam@uoit.c [Faculty of Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, ON, L1H 7K4 (Canada); Easton, E. Bradley [Faculty of Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, ON, L1H 7K4 (Canada)

    2011-02-28

    In this study, we synthesized a new hybrid material using well-Dawson K{sub 6}[P{sub 2}Mo{sub 18}O{sub 62}].nH{sub 2}O and a room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF{sub 4}]). CHN elemental analysis showed that one mole of [P{sub 2}Mo{sub 18}O{sub 62}]{sup 6-} reacts with 6 moles of [BMIM]{sup +} to form [BMIM]{sub 6}P{sub 2}Mo{sub 18}O{sub 62}. FT-IR spectra showed the presence of both 1-butyl-3-methylimidazolium cation and the Dawson anion. TG analysis displayed a relative thermal stability of the hybrid material compared to the parent Dawson POM. The new hybrid material [BMIM]{sub 6}P{sub 2}Mo{sub 18}O{sub 62} was immobilized on glassy carbon (GC) electrode and the modified electrode was investigated by cyclic voltammetry and amperometry. Compared to the electrochemical behavior of dissolved [P{sub 2}Mo{sub 18}O{sub 62}]{sup 6-}, a slight shift in the redox peaks towards negative potentials is observed for the immobilized [BMIM]{sub 6}P{sub 2}Mo{sub 18}O{sub 62}. The relationship between the peak currents of the deposited [BMIM]{sub 6}P{sub 2}Mo{sub 18}O{sub 62} film and scan rate is shown to be linear, which demonstrates a surface-confined electron transfer processes. [BMIM]{sub 6}P{sub 2}Mo{sub 18}O{sub 62} modified electrode showed high sensitivities towards pH and shown to be active even at neutral pH. [BMIM]{sub 6}P{sub 2}Mo{sub 18}O{sub 62} modified GC electrode was subjected to cyclic voltammetry and amperometry in the presence of ascorbic acid (AA) and found to exhibit a remarkable catalytic activity towards the oxidation of AA. The catalytic oxidation peak of AA at [BMIM]{sub 6}P{sub 2}Mo{sub 18}O{sub 62} modified GC electrode occurs at low potential of {approx}0 V vs Ag/AgCl at neutral pH and shifts to more positive potentials when pH decreases. Comparison between [BMIM]{sub 6}P{sub 2}Mo{sub 18}O{sub 62} and [P{sub 2}Mo{sub 18}O{sub 62}]{sup 6-} modified GC films towards the oxidation of AA suggests that

  20. Impedance biosensor for the rapid detection of Listeria spp. based on aptamer functionalized Pt-interdigitated microelectrodes array

    Science.gov (United States)

    Sidhu, R.; Rong, Y.; Vanegas, D. C.; Claussen, J.; McLamore, E. S.; Gomes, C.

    2016-05-01

    Listeria monocytogenes is one of the most common causes of food illness deaths worldwide, with multiple outbreaks in the United States alone. Current methods to detect foodborne pathogens are laborious and can take several hours to days to produce results. Thus, faster techniques are needed to detect bacteria within the same reliability level as traditional techniques. This study reports on a rapid, accurate, and sensitive aptamer biosensor device for Listeria spp. detection based on platinum interdigitated array microelectrodes (Pt-IDEs). Pt-IDEs with different geometric electrode gaps were fabricated by lithographic techniques and characterized by cyclic voltammetric (CV), electrochemical impedance spectroscopy (EIS), and potential amperometry (DCPA) measurements of reversible redox species. Based on these results, 50 μm Pt-IDE was chosen to further functionalize with a Listeria monocytogenes DNA aptamer selective to the cell surface protein internalin A, via metal-thiol self-assembly at the 5' end of the 47-mer's. EIS analysis was used to detect Listeria spp. without the need for label amplification and pre-concentration steps. The optimized aptamer concentration of 800 nM was selected to capture the bacteria through internalin A binding and the aptamer hairpin structure near the 3' end. The aptasensor was capable of detecting a wide range of bacteria concentration from 10 to 106 CFU/mL at lower detection limit of 5.39 +/- 0.21 CFU/mL with sensitivity of 268.1 +/- 25.40 (Ohms/log [CFU/mL]) in 17 min. The aptamer based biosensor offers a portable, rapid and sensitive alternative for food safety applications with one of the lowest detection limits reported to date.

  1. Structure-function relationships affecting the sensing mechanism of monolayer-protected cluster doped xerogel amperometric glucose biosensors.

    Science.gov (United States)

    DiPasquale, Luke T; Poulos, Nicholas G; Hall, Jackson R; Minocha, Aastha; Bui, Tram Anh; Leopold, Michael C

    2015-07-15

    A systematic study of the structure-function relationships critical to understanding the sensing mechanism of 1st generation amperometric glucose biosensors with an embedded nanoparticle (NP) network is presented. Xerogel-based films featuring embedded glucose oxidase enzyme and doped with alkanethiolate-protected gold NPs, known as monolayer protected clusters (MPCs), exhibit significantly enhanced performance compared to analogous systems without NPs including higher sensitivity, faster response time, and extended linear/dynamic ranges. The proposed mechanism involves diffusion of the glucose to glucose oxidase within the xerogel, enzymatic reaction production of H2O2 with subsequent diffusion to the embedded network of MPCs where it is oxidized, an event immediately reported via fast electron transfer (ET) through the MPC system to the working electrode. Various aspects of the film construct and strategy are systematically probed using amperometry, voltammetry, and solid-state electronic conductivity measurements, including the effects of MPC peripheral chain length, MPC functionalization via place-exchange reaction, MPC core size, and the MPC density or concentration within the xerogel composite films. The collective results of these experiments support the proposed mechanism and identify interparticle spacing and the electronic communication through the MPC network is the most significant factor in the sensing scheme with the diffusional aspects of the mechanism that may be affected by film/MPC hydrophobicity and functionality (i.e., glucose and H2O2 diffusion) shown to be less substantial contributors to the overall enhanced performance. Understanding the structure-function relationships of effective sensing schemes allows for the employment of the strategy for future biosensor design toward clinically relevant targets. PMID:25819004

  2. An electrochemical approach: Switching Structures of rare earth metal Praseodymium hexacyanoferrate and its application to sulfite sensor in Red Wine

    International Nuclear Information System (INIS)

    Graphical abstract: Nucleation and growth of PrHCF and its application to sulfite oxidation in wine samples. - Highlights: • Electrochemical synthesis of PrHCF. • Switching structures of PrHCF. • Sulfite electrochemical sensor. • Wide linear range and low limit of detection. • Real sample application. - Abstract: Herein, we report a shape-controlled preparation of Praseodymium hexacyanoferrate (PrHCF) using a simple electrochemical technique. The electrochemically fabricated PrHCF modified glassy carbon electrodes (GCE) shows an excellent electrocatalytic activity towards sulfite oxidation. The morphology of PrHCF particles were controlled by carefully changing various synthesis conditions including electrochemical technique (cyclic voltammetry, amperometry and chemical), cations in the supporting electrolyte (K+, Na+, Li+ and H+), deposition cycles, molar ratio of precursors, and applied potential (-.2,0 and 0.2 V). The morphologies of the PrHCF was elucidated using scanning electron microscopy (SEM). The as-synthesized PrHCF was characterized using X-ray diffraction pattern (XRD), Infra-red (IR) and energy dispersive X-ray spectroscopy (EDX). The electrochemical oxidation of sulfite on PrHCF modified GCE was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The sensitivity of the as-developed sulfite sensor was determined to be 0.036 μA μM−1 cm−2. The low limit of detection was determined to be 2.15 μM. The real time application of PrHCF modified GCE was confirmed through the determination of sulfite from red wine and tap water samples

  3. Highly stable and sensitive glucose biosensor based on covalently assembled high density Au nanostructures.

    Science.gov (United States)

    Si, Peng; Kannan, Palanisamy; Guo, Longhua; Son, Hungsun; Kim, Dong-Hwan

    2011-05-15

    We describe the development of a highly stable and sensitive glucose biosensor based on the nanohybrid materials derived from gold nanoparticles (AuNPs) and multi-walled carbon nanotubes (MWCNT). The biosensing platform was developed by using layer-by-layer (LBL) self-assembly of the nanohybrid materials and the enzyme glucose oxidase (GOx). A high density of AuNPs and MWCNT nanocomposite materials were constructed by alternate self assembly of thiol functionalized MWCNTs and AuNPs, followed by chemisoption of GOx. The surface morphology of multilayered AuNPs/MWCNT structure was characterized by field emission-scanning electron microscope (FE-SEM), and the surface coverage of AuNPs was investigated by cyclic voltammetry (CV), showing that 5 layers of assembly achieves the maximum particle density on electrode. The immobilization of GOx was monitored by electrochemical impedance spectroscopy (EIS). CV and amperometry methods were used to study the electrochemical oxidation of glucose at physiological pH 7.4. The Au electrode modified with five layers of AuNPs/MWCNT composites and GOx exhibited an excellent electrocatalytic activity towards oxidation of glucose, which presents a wide liner range from 20 μM to 10 mM, with a sensitivity of 19.27 μA mM(-1) cm(-2). The detection limit of present modified electrode was found to be 2.3 μM (S/N=3). In addition, the resulting biosensor showed a faster amperometric current response (within 3 s) and low apparent Michaelis-Menten constant (K(m)(app)). Our present study shows that the high density of AuNPs decorated MWCNT is a promising nanohybrid material for the construction of enzyme based electrochemical biosensors. PMID:21454070

  4. Nonenzymatic electrochemical detection of glucose using well-distributed nickel nanoparticles on straight multi-walled carbon nanotubes.

    Science.gov (United States)

    Nie, Huagui; Yao, Zhen; Zhou, Xuemei; Yang, Zhi; Huang, Shaoming

    2011-12-15

    A nonenzymatic electrochemical sensor device was fabricated for glucose detection based on nickel nanoparticles (NiNPs)/straight multi-walled carbon nanotubes (SMWNTs) nanohybrids, which were synthesized through in situ precipitation procedure. SMWNTs can be easily dispersed in solution after mild sonication pretreatment, which facilitates the precursor of NiNPs binding to their surface and results in the homogeneous distribution of NiNPs on the surface of SMWNTs. The morphology and component of the nanohybrids were characterized by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD), respectively. Cyclic voltammetry (CV) and amperometry were used to evaluate the catalytic activity of the NiNPs/SMWNTs nanohybrids modified electrode towards glucose. It was found that the nanohybrids modified electrode showed remarkably enhanced electrocatalytic activity towards the oxidation of glucose in alkaline solution compared to that of the bare glass carbon electrode (GCE), the NiNPs and the SMWNTs modified electrode, attributing to the synergistic effect of SMWNTs and Ni(2+)/Ni(3+) redox couple. Under the optimal detection conditions, the as-prepared sensors exhibited linear behavior in the concentration range from 1 μM to 1 mM for the quantification of glucose with a limit of detection of 500 nM (3σ). Moreover, the NiNPs/SMWNTs modified electrode was also relatively insensitive to commonly interfering species such as ascorbic acid (AA), uric acid (UA), dopamine (DA), galactose (GA), and xylose (XY). The robust selectivities, sensitivities, and stabilities determined experimentally indicated the great potential of NiNPs/SMWNTs nanohybrids for construction of a variety of electrochemical sensors. PMID:21955756

  5. Electronic micropipettor: A versatile fluid propulsion and injection device for micro-flow analysis

    International Nuclear Information System (INIS)

    The shortage of ready to use small sized liquid propulsion and switching devices for microfluidic cells (μ-cell) is a bottleneck in the dissemination of micro-flow analysis (μ-FA), now that microfluidic electrochemical cells can be designed and assembled in any laboratory by thermal transfer of laser printed masks and CD-Rs. Microprocessor-controlled electronic pipettors, commercially available with minimum capacity of 10 μL, represent a compromise solution between oversized peristaltic pumps and tiny 'on a chip' micropumps and valves. The versatility of the electronic pipette coupled with the μ-cell (13-μm deep longitudinal channel) was demonstrated in three operation modes: SIA like, FIA like and direct injection analysis (DIA). Injections of 100 nL K4Fe(China)6 (0.1 mol L-1 KCl) define a linear analytical curve (r = 0.999) in the range of 5 x 10-7 to 1.0 x 10-3 mol L-1 for flow amperometry at a gold electrode potentiostated at 0.4 V versus Ag/AgCl. Methods for the amperometric μ-flow determination of promethazine (FIA like), dipyrone (SIA like) and chlorpromazine (DIA) in pharmaceutical formulations were developed and applied to real samples. Excellent linearity of analytical curves and high repeatability (R.S.D. < 3.0%) at the low picomole range was obtained and all results for real samples were in agreement with reference methods. The results reflect the stability and the reliability of the setups envisioned for the electronic pipette coupled with amperometric μ-cell and the validity of the μ-FA methods

  6. One dimensional CdS nanowire@TiO2 nanoparticles core-shell as high performance photocatalyst for fast degradation of dye pollutants under visible and sunlight irradiation.

    Science.gov (United States)

    Arabzadeh, Abbas; Salimi, Abdollah

    2016-10-01

    In this study, one-dimensional CdS nanowires@TiO2 nanoparticles core-shell structures (1D CdS NWs@TiO2 NPs) were synthesized by a facile wet chemical-solvothermal method. The different aspects of the properties of CdS NWs@TiO2 NPs were surveyed by using a comprehensive range of characterization techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-vis spectroscopy, scanning electron microscopy (SEM), fluorescence spectroscopy, energy dispersive X-ray spectroscopy (EDX), Cyclic Voltammetry (CV) and amperometry. The as-prepared nanostructure was applied as an effective photocatalyst for degradation of methyl orange (MO), methylene blue (MB) and rhodamine B (Rh B) under visible and sunlight irradiation. The results indicated significantly enhanced photocatalytic activity of CdS NWs@TiO2 NPs for degradation of MO, MB and Rh B compared to CdS NWs. The enhanced photocatalytic activity could be attributed to the enhanced sunlight absorbance and the efficient charge separation of the formed heterostructure between CdS NWs and TiO2. The results showed that MO, Rh B and MB were almost completely degraded after 2, 2 and 3min of exposure to sunlight, respectively; while under visible light irradiation (3W blue LED lamp) the dyes were decomposed with less half degradation rate. The catalytic activity was retained even after three degradation cycles of organic dyes, demonstrating that the proposed nanocomposite can be effectively used as efficient photocatalyst for removal of environmental pollutions caused by organic dyes under sunlight irradiation and it could be an important addition to the field of wastewater treatment. We hope the present study may open a new window of such 1-D semiconductor nanocomposites to be used as visible light photocatalysts in the promising field of organic dyes degradation. PMID:27348482

  7. The Involvement of Ser1898 of the Human L-Type Calcium Channel in Evoked Secretion

    Directory of Open Access Journals (Sweden)

    Niv Bachnoff

    2011-01-01

    Full Text Available A PKA consensus phosphorylation site S1928 at the α11.2 subunit of the rabbit cardiac L-type channel, CaV1.2, is involved in the regulation of CaV1.2 kinetics and affects catecholamine secretion. This mutation does not alter basal CaV1.2 current properties or regulation of CaV1.2 current by PKA and the beta-adrenergic receptor, but abolishes CaV1.2 phosphorylation by PKA. Here, we test the contribution of the corresponding PKA phosphorylation site of the human α11.2 subunit S1898, to the regulation of catecholamine secretion in bovine chromaffin cells. Chromaffin cells were infected with a Semliki-Forest viral vector containing either the human wt or a mutated S1898A α11.2 subunit. Both subunits harbor a T1036Y mutation conferring nifedipine insensitivity. Secretion evoked by depolarization in the presence of nifedipine was monitored by amperometry. Depolarization-triggered secretion in cells infected with either the wt α11.2 or α11.2/S1898A mutated subunit was elevated to a similar extent by forskolin. Forskolin, known to directly activate adenylyl-cyclase, increased the rate of secretion in a manner that is largely independent of the presence of S1898. Our results are consistent with the involvement of additional PKA regulatory site(s at the C-tail of α11.2, the pore forming subunit of CaV1.2.

  8. Alpha-Glucosidase Enzyme Biosensor for the Electrochemical Measurement of Antidiabetic Potential of Medicinal Plants.

    Science.gov (United States)

    Mohiuddin, M; Arbain, D; Islam, A K M Shafiqul; Ahmad, M S; Ahmad, M N

    2016-12-01

    A biosensor for measuring the antidiabetic potential of medicinal plants was developed by covalent immobilization of α-glucosidase (AG) enzyme onto amine-functionalized multi-walled carbon nanotubes (MWCNTs-NH2). The immobilized enzyme was entrapped in freeze-thawed polyvinyl alcohol (PVA) together with p-nitrophenyl-α-D-glucopyranoside (PNPG) on the screen-printed carbon electrode at low pH to prevent the premature reaction between PNPG and AG enzyme. The enzymatic reaction within the biosensor is inhibited by bioactive compounds in the medicinal plant extracts. The capability of medicinal plants to inhibit the AG enzyme on the electrode correlates to the potential of the medicinal plants to inhibit the production of glucose from the carbohydrate in the human body. Thus, the inhibition indicates the antidiabetic potential of the medicinal plants. The performance of the biosensor was evaluated to measure the antidiabetic potential of three medicinal plants such as Tebengau (Ehretis laevis), Cemumar (Micromelum pubescens), and Kedondong (Spondias dulcis) and acarbose (commercial antidiabetic drug) via cyclic voltammetry, amperometry, and spectrophotometry. The cyclic voltammetry (CV) response for the inhibition of the AG enzyme activity by Tebengau plant extracts showed a linear relation in the range from 0.423-8.29 μA, and the inhibition detection limit was 0.253 μA. The biosensor exhibited good sensitivity (0.422 μA/mg Tebengau plant extracts) and rapid response (22 s). The biosensor retains approximately 82.16 % of its initial activity even after 30 days of storage at 4 °C. PMID:26887579

  9. In situ activated nanostructured platform for oxidized glutathione biosensing

    International Nuclear Information System (INIS)

    Highlights: ► New nanostructured platform for GSSG determination based on multi walled carbon nanotubes and chitosan. ► The redox mediator activated in situ showed a high electrocatalytic constant for NADH electrooxidation. ► An amperometric method for GSSG determination based on NADH consumption has been presented for the first time. -- Abstract: This work describes the construction of a biosensor for glutathione disulfide (GSSG) based on a nanostructured platform composed by MWCNTs, chitosan (CHIT) and the redox mediator 3,5-dinitrobenzoic acid. The dispersion of MWCNTs and CHIT showed a good stability and was used to modify the glassy carbon electrode (GCE). The nanostructured platform was characterized by scanning electron microscopy (SEM) and electrochemical techniques. The R-NO/R-NHOH redox couple was electrogenerated in situ by cycling the potential between 0.2 and −0.4 V vs. SCE. After activating the nanostructured platform, glutathione reductase was easily immobilized on the electrode surface by using glutaraldehyde as functional linker. The biosensor performance was optimized in terms of amount of enzyme, effect of CHIT concentration and NADH amount. Under optimized conditions, the biosensor response for GSSG sensing was linear from 2.0 up to 35 μmol L−1 with detection and quantification limits achieving values of 0.6 and 2.0 μmol L−1, respectively and sensitivity of 6.24 mA L mol−1. The apparent Michaelis–Menten constant (KMapp) obtained by amperometry for the immobilized glutathione reductase on the nanostructured platform was 60 μmol L−1

  10. Syntaxin 1A interaction with the dopamine transporter promotes amphetamine-induced dopamine efflux.

    Science.gov (United States)

    Binda, Francesca; Dipace, Concetta; Bowton, Erica; Robertson, Sabrina D; Lute, Brandon J; Fog, Jacob U; Zhang, Minjia; Sen, Namita; Colbran, Roger J; Gnegy, Margaret E; Gether, Ulrik; Javitch, Jonathan A; Erreger, Kevin; Galli, Aurelio

    2008-10-01

    The soluble N-ethylmaleimide-sensitive factor attachment protein receptor protein syntaxin 1A (SYN1A) interacts with and regulates the function of transmembrane proteins, including ion channels and neurotransmitter transporters. Here, we define the first 33 amino acids of the N terminus of the dopamine (DA) transporter (DAT) as the site of direct interaction with SYN1A. Amphetamine (AMPH) increases the association of SYN1A with human DAT (hDAT) in a heterologous expression system (hDAT cells) and with native DAT in murine striatal synaptosomes. Immunoprecipitation of DAT from the biotinylated fraction shows that the AMPH-induced increase in DAT/SYN1A association occurs at the plasma membrane. In a superfusion assay of DA efflux, cells overexpressing SYN1A exhibited significantly greater AMPH-induced DA release with respect to control cells. By combining the patch-clamp technique with amperometry, we measured DA release under voltage clamp. At -60 mV, a physiological resting potential, AMPH did not induce DA efflux in hDAT cells and DA neurons. In contrast, perfusion of exogenous SYN1A (3 microM) into the cell with the whole-cell pipette enabled AMPH-induced DA efflux at -60 mV in both hDAT cells and DA neurons. It has been shown recently that Ca2+/calmodulin-dependent protein kinase II (CaMKII) is activated by AMPH and regulates AMPH-induced DA efflux. Here, we show that AMPH-induced association between DAT and SYN1A requires CaMKII activity and that inhibition of CaMKII blocks the ability of exogenous SYN1A to promote DA efflux. These data suggest that AMPH activation of CaMKII supports DAT/SYN1A association, resulting in a mode of DAT capable of DA efflux.

  11. Electrochemical fabrication of a novel conducting metallopolymer nanoparticles and its electrocatalytic application

    International Nuclear Information System (INIS)

    Graphical abstract: Nanoparticles of nickel-curcumin conducting polymer (Ni-Curc-NPs) were fabricated by a two steps electrochemical method. In the first step, nickel source was immobilized at the electrode surface in the form of nickel nanoparticles (NiNPs). Then, electropolymerization of Ni-curcumin was performed at the NiNPs modified electrode. These nanostructures were successfully employed for electrooxidative determination of glucose and significant increase in the electrochemical sensitivity and lower limit of detection were observed. -- Highlights: • A novel two steps method for fabrication of nickel-curcumin conducting polymer was described. • Nickel-curcumine nanoparticles were easily prepared instead of thin film. • Ni-Curc-NPs modified electrode was successfully employed for electrooxidation of glucose. • Significant improvement in the sensitivity and limit of detection was observed. -- Abstract: Present article is the first example of a novel two step electrochemical route for fabrication of nanoparticles of conducting metallopolymer of Ni-curcumin (Ni-Curc-NPs). Firstly, nickel nanoparticles (Ni-NPs) were electrochemically deposited on the electrode surface. Then, electropolymerization of Ni-Curc-NPs were performed at the electrode modified with Ni-NPs. These nanostructures were characterized using electrochemical methods including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and hydrodynamic amperometry, also surface analysis methods and electron microscopy including energy dispersive analysis of X-ray (EDAX), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Additionally, application of the Ni-Curc-NPs modified electrode toward glucose electrooxidation was examined. A lower limit of detection and enhanced dynamic linear range for determination of glucose were observed at Ni-Curc-NPs modified electrode compared to Ni-NPs modified electrode

  12. Fabrication of potato-like silver molybdate microstructures for photocatalytic degradation of chronic toxicity ciprofloxacin and highly selective electrochemical detection of H2O2

    Science.gov (United States)

    Kumar, J. Vinoth; Karthik, R.; Chen, Shen-Ming; Muthuraj, V.; Karuppiah, Chelladurai

    2016-01-01

    In the present work, potato-like silver molybdate (Ag2MoO4) microstructures were synthesized through a simple hydrothermal method. The microstructures of Ag2MoO4 were characterized by various analytical and spectroscopic techniques such as XRD, FTIR, Raman, SEM, EDX and XPS. Interestingly, the as-prepared Ag2MoO4 showed excellent photocatalytic and electrocatalytic activity for the degradation of ciprofloxacin (CIP) and electrochemical detection of hydrogen peroxide (H2O2), respectively. The ultraviolet-visible (UV-Vis) spectroscopy results revealed that the potato-like Ag2MoO4 microstructures could offer a high photocatalytic activity towards the degradation of CIP under UV-light illumination, leads to rapid degradation within 40 min with a degradation rate of above 98%. In addition, the cyclic voltammetry (CV) and amperometry studies were realized that the electrochemical performance of Ag2MoO4 modified electrode toward H2O2 detection. Our H2O2 sensor shows a wide linear range and lower detection limit of 0.04–240 μM and 0.03 μM, respectively. The Ag2MoO4 modified electrode exhibits a high selectivity towards the detection of H2O2 in the presence of different biological interferences. These results suggested that the development of potato-like Ag2MoO4 microstructure could be an efficient photocatalyst as well as electrocatalyst in the potential application of environmental, biomedical and pharmaceutical samples. PMID:27671795

  13. Highly accessible Pt nanodots homogeneously decorated on Au nanorods surface for sensing

    International Nuclear Information System (INIS)

    Highlights: • Seed-growth of highly-dispersed catalytic Pt nanodot on Au nanorod (PtND@AuNR). • Good accessibility of catalytic sites was evidenced by its peroxidase-like activity. • Excellent assay performances of H2O2 at PtND@AuNR-based sensor. - Abstract: Some nanostructures are reported to possess enzyme-mimetic activities similar to those of natural enzymes. Herein, highly-dispersed Pt nanodots on Au nanorods (HD- PtNDs@AuNRs) with mimetic peroxidase activity were designed as an active electrode modifier for fabrication of a hydrogen peroxide (H2O2) electrochemical sensor. The HD-PtNDs@AuNRs were synthesized by a seed-mediated growth approach and confirmed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and UV–vis spectroscopy. The electrochemical and catalytical performances of HD-PtNDs@AuNRs towards H2O2 reduction were investigated in detail by cyclic voltammetry and amperometry. The HD-PtNDs@AuNRs modified electrode displayed a high catalytic activity to H2O2 at −0.10 V (versus SCE), a rapid response within 5 s, a wide linear range of 2.0–3800.0 μM, a detection limit of 1.2 μM (S/N = 3), and a high sensitivity of 181 μA mM−1 cm−2. These results suggested a promising potential of fabricating H2O2 electrochemical sensor using HD- PtNDs@AuNRs

  14. Highly sensitive interference-free electrochemical determination of pyridoxine at graphene modified electrode: Importance in Parkinson and Asthma treatments.

    Science.gov (United States)

    Raj, M Amal; Gowthaman, N S K; John, S Abraham

    2016-07-15

    To reduce the side effects in the medication of Parkinson and Asthma, pyridoxine (PY) is administered along with l-3,4-dihydroxyphenyl alanine (l-dopa) and theophylline (TP), respectively. However, excessive dosage of PY leads to nervous disorder. Thus, a sensitive and selective electrochemical method was developed for the determination of PY in the presence of major interferences including TP, l-dopa, ascorbic acid (AA) and riboflavin (RB) using electrochemically reduced graphene oxide (ERGO) film modified glassy carbon electrode (GCE) in this paper. The ERGO fabrication process involves the nucleophilic substitution of graphene oxide at basic pH on amine terminal of 1,6-hexadiamine which was pre-assembled on GCE followed by electrochemical reduction. The electrocatalytic activity of the ERGO modified electrode was examined towards the oxidation of PY. It greatly enhanced the oxidation current of PY in contrast to bare and GO modified GCEs due to facile electron transfer besides π-π interaction between ERGO film and PY. Since TP and l-dopa drugs antagonize the drug action of PY, ERGO modified GCE was also used for the simultaneous determination of PY and l-dopa and PY and TP. Further, the selective determination of PY in the presence of other water soluble vitamins such as ascorbic acid and riboflavin was also demonstrated. Using amperometry, detection of 100nM PY was achieved and the detection limit was found to be 5.6×10(-8)M (S/N=3). The practical application of the present method was demonstrated by determining the concentration of PY in human blood serum and commercial drugs. PMID:27124811

  15. Amperometric L-glutamate biosensor based on bacterial cell-surface displayed glutamate dehydrogenase

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Bo [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049 (China); Zhang, Shu [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Key Laboratory of Marine Chemistry Theory and Technology of Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao 266100 (China); Lang, Qiaolin [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Song, Jianxia; Han, Lihui [Key Laboratory of Marine Chemistry Theory and Technology of Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao 266100 (China); Liu, Aihua, E-mail: liuah@qibebt.ac.cn [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049 (China)

    2015-07-16

    Highlights: • E. coli surface-dispalyed Gldh exhibiting excellent enzyme activity and stability. • Sensitive amperometric biosensor for glutamate using Gldh-bacteria and MWNTs. • The glutamate biosensor exhibited high specificity and stability. - Abstract: A novel L-glutamate biosensor was fabricated using bacteria surface-displayed glutamate dehydrogenase (Gldh-bacteria). Here the cofactor NADP{sup +}-specific dependent Gldh was expressed on the surface of Escherichia coli using N-terminal region of ice nucleation protein (INP) as the anchoring motif. The cell fractionation assay and SDS-PAGE analysis indicated that the majority of INP-Gldh fusion proteins were located on the surface of cells. The biosensor was fabricated by successively casting polyethyleneimine (PEI)-dispersed multi-walled carbon nanotubes (MWNTs), Gldh-bacteria and Nafion onto the glassy carbon electrode (Nafion/Gldh-bacteria/PEI-MWNTs/GCE). The MWNTs could not only significantly lower the oxidation overpotential towards NAPDH, which was the product of NADP{sup +} involving in the oxidation of glutamate by Gldh, but also enhanced the current response. Under the optimized experimental conditions, the current–time curve of the Nafion/Gldh-bacteria/PEI-MWNTs/GCE was performed at +0.52 V (vs. SCE) by amperometry varying glutamate concentration. The current response was linear with glutamate concentration in two ranges (10 μM–1 mM and 2–10 mM). The low limit of detection was estimated to be 2 μM glutamate (S/N = 3). Moreover, the proposed biosensor is stable, specific, reproducible and simple, which can be applied to real samples detection.

  16. New Copper wide range nanosensor electrode prepared by physical vapor deposition at oblique angles for the non-enzimatic determination of glucose

    International Nuclear Information System (INIS)

    In this work a novel Cu nanostructured electrode is presented. Cu tilted nanocolumnar and porous thin films have been prepared by physical vapor deposition (PVD) in an oblique angle configuration and characterized by different techniques. Cyclic voltammetry and amperometry were used to study the sensing ability of the copper films deposited on ITO to quantitatively determine glucose and to optimize the experimental conditions of detection. Scanning electron microscopy data revealed that the film microstructure consists of tilted nanocolumns of around 70 nm of diameter and an inclination of 65° with respect to the surface normal that extend through the total thickness of the layer of ca. 300 nm. X ray photoelectron spectroscopy and Raman, used to determine the oxidation state of Cu, revealed that an oxy/hydroxide external layer formed around the nanocolumns is the active phase responsible for the electrocatalytic detection of glucose. Under optimized conditions, the CuO/Cu nanoporous/ITO electrode presented a sensitivity of 1.41 A mol dm−3 cm−2 (R2:0.999) with a limit of detection of 0.36 μmol dm−3 and a reproducibility of 3.42%.The selectivity of the proposed sensor was checked against various interferences, including physiological compounds, different sugars and ethanol, thereby showing excellent anti-interference properties. The CuO/Cu nanoporous/ITO electrode was also used successfully to determine glucose in blood samples showing a performance comparable to that of a commercial glucometer. An extended working range covering from 1 to 5 × 10−3 mol dm−3 was determined for these sensor films which, in this way, could be applied for different analytical purposes including agro industrial liquids

  17. Synthesis and characterization of cobalt-nichel oxides for the oxygen formation reaction; Sintesis y caracterizacion de oxidos de cobalto-niquel para la reaccion de formacion de oxigeno

    Energy Technology Data Exchange (ETDEWEB)

    Morales G, P

    2001-07-01

    In this work the compounds of cobalt and nickel oxides and the mixtures of cobalt-nickel were prepared which were characterized and evaluated as electrocatalysts in the oxygen release reaction in alkaline media. The compounds were synthesised by the sol-gel method: heated at 400 and 500 Centigrade. The compounds characterization was realized by thermogravimetry, X-ray diffraction and Scanning electron microscopy. As the Co{sub 3}O{sub 4} and the Ni O as the mixtures Ni O/Co{sub 3}O{sub 4} were obtained as a porous material with a small particle size, characteristics which are presented by cause of the low temperature of synthesis. The electrocatalytic evaluation for the synthesised compounds for the oxygen release reaction was realized by cyclic volt amperometry in a 0.5M KOH solution. The oxides mixtures presented a well electrocatalytic activity to be used in the electrochemical release of oxygen. The current density and the electrochemically active area, in all the cases of mixtures is very higher to the Co{sub 3}O{sub 4} and Ni O ones. Observing with greater clearness the synergic effects, in the obtained mixture at 400 C. The oxides mixtures heated at 400 C were stables for the oxygen formation reaction. Therefore it is be able to say that the Ni O/Co{sub 3}O{sub 4} mixture counts on a great reactive area: electrocatalytic characteristic desirable to be a material used as anode in the electrolysis of water, which increases the oxygen release in the anode and so the hydrogen release in the cathode. (Author)

  18. Highly accessible Pt nanodots homogeneously decorated on Au nanorods surface for sensing

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xun [College of Chemistry, Jilin University, Changchun 130012 (China); Li, Xin [College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Shi, Hongyan; Huang, Hao [College of Chemistry, Jilin University, Changchun 130012 (China); Wu, Xiaochun [CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing 100190 (China); Song, Wenbo, E-mail: wbsong@jlu.edu.cn [College of Chemistry, Jilin University, Changchun 130012 (China)

    2014-12-10

    Highlights: • Seed-growth of highly-dispersed catalytic Pt nanodot on Au nanorod (PtND@AuNR). • Good accessibility of catalytic sites was evidenced by its peroxidase-like activity. • Excellent assay performances of H{sub 2}O{sub 2} at PtND@AuNR-based sensor. - Abstract: Some nanostructures are reported to possess enzyme-mimetic activities similar to those of natural enzymes. Herein, highly-dispersed Pt nanodots on Au nanorods (HD- PtNDs@AuNRs) with mimetic peroxidase activity were designed as an active electrode modifier for fabrication of a hydrogen peroxide (H{sub 2}O{sub 2}) electrochemical sensor. The HD-PtNDs@AuNRs were synthesized by a seed-mediated growth approach and confirmed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and UV–vis spectroscopy. The electrochemical and catalytical performances of HD-PtNDs@AuNRs towards H{sub 2}O{sub 2} reduction were investigated in detail by cyclic voltammetry and amperometry. The HD-PtNDs@AuNRs modified electrode displayed a high catalytic activity to H{sub 2}O{sub 2} at −0.10 V (versus SCE), a rapid response within 5 s, a wide linear range of 2.0–3800.0 μM, a detection limit of 1.2 μM (S/N = 3), and a high sensitivity of 181 μA mM{sup −1} cm{sup −2}. These results suggested a promising potential of fabricating H{sub 2}O{sub 2} electrochemical sensor using HD- PtNDs@AuNRs.

  19. Flow-based method for epinephrine determination using a solid reactor based on molecularly imprinted poly(FePP-MAA-EGDMA)

    International Nuclear Information System (INIS)

    A solid phase reactor based on molecularly imprinted poly(iron (III) protoporphyrin-methacrylic acid-ethylene glycol dimethacrylate) (MIP-MAA) has been synthesized by bulk method and applied as an selective material for the epinephrine determination in the presence of hydrogen peroxide. In order to prove the selective behaviour of MIP, two blank polymers named non-imprinted polymer (NIP1), non-imprinted polymer in the absence of hemin (NIP2) as well as a poly(iron (III) protoporphyrin-4-vynilpyridine-ethylene glycol dimethacrylate) (MIP-4VPy) were synthesized. The epinephrine-selective MIP-MAA reactor was used in a flow injection system, in which an epinephrine solution (120 μL) at pH 8.0 percolates in the presence of hydrogen peroxide (300 μmol L-1) through MIP-MAA. The oxidation of epinephrine by hydrogen peroxide is increased by using MIP-MAA, being the product formed monitored by amperometry at 0.0 V vs. Ag/AgCl. The MIP-MAA showed better selective behaviour than NIP1, NIP2 and MIP-4VPy, demonstrating the effectiveness of molecular imprinting effect. Highly improved response was observed for epinephrine in detriment of similar substances (phenol, ascorbic acid, methyl-L-DOPA, p-aminophenol, catechol, L-DOPA and guaiacol). The method provided a calibration curve ranging from 10 to 500 μmol L-1 and a limit of detection of 5.2 μmol L-1. Kinetic data indicated a value of maximum rate Vmax (0.993 μA) and apparent Michaelis-Menten constant of Kmapp(725.6 μmol L-1). The feasibility of biomimetic solid reactor was attested by its successful application for epinephrine determination in pharmaceutical formulation.

  20. Simultaneous determination of paracetamol and ascorbic acid using tetraoctylammonium bromide capped gold nanoparticles immobilized on 1,6-hexanedithiol modified Au electrode

    Energy Technology Data Exchange (ETDEWEB)

    Nair, Santhosh S. [Department of Chemistry, Gandhigram Rural University, Gandhigram 624302, Dindigul (India); John, S. Abraham [Department of Chemistry, Gandhigram Rural University, Gandhigram 624302, Dindigul (India)], E-mail: abrajohn@yahoo.co.in; Sagara, Takamasa [Department of Chemistry, Gandhigram Rural University, Gandhigram 624302, Dindigul (India)], E-mail: sagara@nagasaki-u.ac.jp

    2009-11-30

    Tetraoctylammonium bromide stabilized gold nanoparticles (TOAB-AuNPs) attached to 1,6-hexanedithiol (HDT) modified Au electrode was used for the simultaneous determination of paracetamol (PA) and ascorbic acid (AA) at physiological pH. The attachment of TOAB-AuNPs on HDT modified Au surface was confirmed by attenuated total reflectance (ATR)-FT-IR spectroscopy and atomic force microscope (AFM). The ATR-FT-IR spectrum of TOAB-AuNPs attached to the HDT monolayer showed a characteristic stretching modes corresponding to -CH{sub 2} and -CH{sub 3} of TOAB, confirming the immobilization of AuNPs with surface-protecting TOAB ions on the surface of the AuNPs after being attached to HDT modified Au electrode. AFM image showed that the immobilized AuNPs were spherical in shape and densely packed to a film of ca. 7 nm thickness. Interestingly, TOAB-AuNPs modified electrode shifted the oxidation potential of PA towards less positive potential by 70 mV and enhanced its oxidation current twice when compared to bare Au electrode. In addition, the AuNPs modified electrode separated the oxidation potentials of AA and PA by 210 mV, whereas bare Au electrode failed to resolve them. The amperometry current of PA was increased linearly from 1.50 x 10{sup -7} to 1.34 x 10{sup -5} M with a correlation coefficient of 0.9981 and the lowest detection limit was found to be 2.6 nM (S/N = 3). The present method was successfully used to determine the concentration of PA in human blood plasma and commercial drugs.

  1. Determination of ascorbic acid in pharmaceutical preparation and fruit juice using modified carbon paste electrode

    Directory of Open Access Journals (Sweden)

    Simona Žabčíková

    2016-06-01

    Full Text Available Acrobic acid is key substance in the human metabolism and the rapid and accurate determination in food is of a great interest. Ascorbic acid is an electroactive compound, however poorly responded on the bare carbon paste electrodes. In this paper, brilliant cresyl blue and multi-walled carbon nanotubes were used for the modification of carbon paste electrode. Brilliant cresyl blue acts as a mediator improving the transition of electrons, whereas multiwalled carbon nanotubes increased the surface of the electrode. Both brilliant cresyl blue and multiwalled carbon nanotubes were added directly to the composite material. The electrochemical behavior of modified electode was determined in electrolyte at various pH, and the effect of the scan rate was also performed. It was shown that the electrochemical process on the surface of the modified carbon paste electrode was diffusion-controlled. The resulted modified carbon paste electrode showed a good electrocatalytic activity towards the oxidation of ascorbic acid at a reduced overpotential of +100 mV descreasing the risk of interferences. A linear response of the ascorbic acid oxidation current measured by the amperometry in the range of 0.1 - 350 µmol.L-1 was obtained applying the sensor for the standard solution. The limit of detection and limit of quantification was found to be 0.05 and 0.15 µmol.L-1, respectively. The novel method was applied for the determination of ascorbic acid in pharmaceutical vitamin preparation and fruit juice, and the results were in good agreement with the standard HPLC method. The presented modification of carbon paste electrode is suitable for the fast, sensitive and very accurate determination of ascorbic acid in fruit juices and pharmaceutical preparation.

  2. Flow-based method for epinephrine determination using a solid reactor based on molecularly imprinted poly(FePP-MAA-EGDMA)

    Energy Technology Data Exchange (ETDEWEB)

    Sartori, Lucas Rossi [Programa de Pos-Graduacao em Ciencias Farmaceuticas, Universidade Federal de Alfenas (Unifal-MG), Rua Gabriel Monteiro da Silva, 714, 37130-000, Alfenas/MG (Brazil); Santos, Wilney de Jesus Rodrigues [Departamento de Quimica Analitica, Instituto de Quimica, Universidade Estadual de Campinas (Unicamp), Cidade Universitaria Zeferino Vaz s/n,13083-970, Campinas/SP (Brazil); Kubota, Lauro Tatsuo [Departamento de Quimica Analitica, Instituto de Quimica, Universidade Estadual de Campinas (Unicamp), Cidade Universitaria Zeferino Vaz s/n,13083-970, Campinas/SP (Brazil); Instituto Nacional de Ciencia e Tecnologia (INCT) de Bioanalitica, Universidade Estadual de Campinas (Unicamp), Instituto de Quimica, Departamento de Quimica Analitica, Cidade Universitaria Zeferino Vaz s/n, 13083-970, Campinas/SP (Brazil); Segatelli, Mariana Gava [Departamento de Quimica, Universidade Estadual de Londrina (UEL), Rod. Celso Garcia PR 445 Km 380, 86051-990, Londrina/PR (Brazil); Tarley, Cesar Ricardo Teixeira, E-mail: tarley@uel.br [Programa de Pos-Graduacao em Ciencias Farmaceuticas, Universidade Federal de Alfenas (Unifal-MG), Rua Gabriel Monteiro da Silva, 714, 37130-000, Alfenas/MG (Brazil); Instituto Nacional de Ciencia e Tecnologia (INCT) de Bioanalitica, Universidade Estadual de Campinas (Unicamp), Instituto de Quimica, Departamento de Quimica Analitica, Cidade Universitaria Zeferino Vaz s/n, 13083-970, Campinas/SP (Brazil)

    2011-03-12

    A solid phase reactor based on molecularly imprinted poly(iron (III) protoporphyrin-methacrylic acid-ethylene glycol dimethacrylate) (MIP-MAA) has been synthesized by bulk method and applied as an selective material for the epinephrine determination in the presence of hydrogen peroxide. In order to prove the selective behaviour of MIP, two blank polymers named non-imprinted polymer (NIP1), non-imprinted polymer in the absence of hemin (NIP2) as well as a poly(iron (III) protoporphyrin-4-vynilpyridine-ethylene glycol dimethacrylate) (MIP-4VPy) were synthesized. The epinephrine-selective MIP-MAA reactor was used in a flow injection system, in which an epinephrine solution (120 {mu}L) at pH 8.0 percolates in the presence of hydrogen peroxide (300 {mu}mol L{sup -1}) through MIP-MAA. The oxidation of epinephrine by hydrogen peroxide is increased by using MIP-MAA, being the product formed monitored by amperometry at 0.0 V vs. Ag/AgCl. The MIP-MAA showed better selective behaviour than NIP1, NIP2 and MIP-4VPy, demonstrating the effectiveness of molecular imprinting effect. Highly improved response was observed for epinephrine in detriment of similar substances (phenol, ascorbic acid, methyl-L-DOPA, p-aminophenol, catechol, L-DOPA and guaiacol). The method provided a calibration curve ranging from 10 to 500 {mu}mol L{sup -1} and a limit of detection of 5.2 {mu}mol L{sup -1}. Kinetic data indicated a value of maximum rate V{sub max} (0.993 {mu}A) and apparent Michaelis-Menten constant of K{sub m}{sup app}(725.6 {mu}mol L{sup -1}). The feasibility of biomimetic solid reactor was attested by its successful application for epinephrine determination in pharmaceutical formulation.

  3. Preparation and electrocatalytic application of composites containing gold nanoparticles protected with rhodium-substituted polyoxometalates

    International Nuclear Information System (INIS)

    Substitution of a metal center of phosphomolybdate, PMo12O403- (PMo12), or its tungsten analogue with dirhodium(II) and subsequent stabilization of gold nanoparticles, AuNPs, with Rh2PMo11 are demonstrated. The AuNP-Rh2PMo11 mediates oxidations but adsorbs too weakly for direct modification of electrode materials. Stability in quiescent solution was achieved by modifying glassy carbon (GC) with 3-aminopropyltriethoxysilane (APTES) and then electrostatically assembling AuNP-Rh2PMo11. At GC|APTES|AuNP-Rh2PMo11, cyclic voltammetry showed the expected set of three reversible peak-pairs for PMo11 in the range -0.2 to 0.6 vs. (Ag/AgCl)/V and the reversible RhII,III couple at 1.0 vs. (Ag/AgCl)/V. The presence of AuNPs increased the current for the reduction of bromate by a factor of 2.5 relative to that at GC|Rh2PMo11, and the electrocatalytic oxidation of methionine displayed characteristics of synergism between the AuNP and RhII. To stabilize AuNP-Rh2PMo11 on a surface in a flow system, GC was modified by electrochemically assisted deposition of a sol-gel with templated 10-nm pores prior to immobilizing the catalyst in the pores. The resulting electrode permitted determination of bromate by flow-injection amperometry with a detection limit of 4.0 x 10-8 mol dm-3.

  4. Hemodynamic responses in amygdala and hippocampus distinguish between aversive and neutral cues during Pavlovian fear conditioning in behaving rats.

    Science.gov (United States)

    McHugh, Stephen B; Marques-Smith, Andre; Li, Jennifer; Rawlins, J N P; Lowry, John; Conway, Michael; Gilmour, Gary; Tricklebank, Mark; Bannerman, David M

    2013-02-01

    Lesion and electrophysiological studies in rodents have identified the amygdala and hippocampus (HPC) as key structures for Pavlovian fear conditioning, but human functional neuroimaging studies have not consistently found activation of these structures. This could be because hemodynamic responses cannot detect the sparse neuronal activity proposed to underlie conditioned fear. Alternatively, differences in experimental design or fear levels could account for the discrepant findings between rodents and humans. To help distinguish between these alternatives, we used tissue oxygen amperometry to record hemodynamic responses from the basolateral amygdala (BLA), dorsal HPC (dHPC) and ventral HPC (vHPC) in freely-moving rats during the acquisition and extinction of conditioned fear. To enable specific comparison with human studies we used a discriminative paradigm, with one auditory cue [conditioned stimulus (CS)+] that was always followed by footshock, and another auditory cue (CS-) that was never followed by footshock. BLA tissue oxygen signals were significantly higher during CS+ than CS- trials during training and early extinction. In contrast, they were lower during CS+ than CS- trials by the end of extinction. dHPC and vHPC tissue oxygen signals were significantly lower during CS+ than CS- trials throughout extinction. Thus, hemodynamic signals in the amygdala and HPC can detect the different patterns of neuronal activity evoked by threatening vs. neutral stimuli during fear conditioning. Discrepant neuroimaging findings may be due to differences in experimental design and/or fear levels evoked in participants. Our methodology offers a way to improve translation between rodent models and human neuroimaging.

  5. The Effect of Multilayer Gold Nanoparticles on the Electrochemical Response of Ammonium Ion Biosensor Based on Alanine Dehydrogenase Enzyme

    Directory of Open Access Journals (Sweden)

    Tan Ling Ling

    2011-01-01

    Full Text Available The use of multilayer of gold nanoparticles (AuNPs attached on gold electrode surface via thiol chemistry to fabricate an ammonium (NH4+ ion biosensor based on alanine dehydrogenase (AlaDH was investigated. The approach of the study was based on construction of biosensor by direct deposition of AuNPs and 1,8-octanedithiol (C8-DT onto the gold electrode surface. For the immobilisation of enzyme, 2-mercaptoethanol (2BME was first covalently attached to AlaDH via esther bonding and then followed by chemically attached the 2BME-modified AlaDH (2BME-AlaDH moiety onto the AuNPs electrode via the exposed thiol group of 2BME. The resulting biosensor response was examined by means of amperometry for the quantification of NH4+ ion. In the absence of enzyme attachment, the use of three layers of AuNPs was found to improve the electrochemistry of the gold electrode when compared with no AuNPs was coated. However, when more than three layers of AuNPs were coated, the electrode response deteriorated due to excessive deposition of C8-DT. When AlaDH was incoporated into the AuNPs modified electrode, a linear response to NH4+ ion over the concentration range of 0.1–0.5 mM with a detection limit of 0.01 mM was obtained. In the absence of AuNPs, the NH4+ ion biosensor did not exhibit any good linear response range although the current response was observed to be higher. This work demonstrated that the incorporation of AuNPs could lead to the detection of higher NH4+ ion concentration without the need of dilution for high NH4+ ion concentration samples with a rapid response time of <1 min.

  6. Dispersion of multi-wall carbon nanotubes in polyhistidine: Characterization and analytical applications

    Energy Technology Data Exchange (ETDEWEB)

    Dalmasso, Pablo R. [INFIQC, Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Pedano, Maria L., E-mail: mlpedano@fcq.unc.edu.ar [INFIQC, Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Rivas, Gustavo A., E-mail: grivas@mail.fcq.unc.edu.ar [INFIQC, Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina)

    2012-01-13

    Highlights: Black-Right-Pointing-Pointer Polyhistidine (Polyhis) is an efficient dispersing agent of MWCNT. Black-Right-Pointing-Pointer MWCNT/Polyhis ratio and sonication time are critical variables when dispersing MWCNT. Black-Right-Pointing-Pointer MWCNT-Polyhis deposited at GCE largely catalyzes the oxidation of ascorbic acid. Black-Right-Pointing-Pointer GCE/MWCNT-Polyhis allows the selective and sensitive quantification of UA and Do. - Abstract: We report for the first time the use of polyhistidine (Polyhis) to efficiently disperse multiwall carbon nanotubes (MWCNTs). The optimum dispersion MWCNT-Polyhis was obtained by sonicating for 30 min 1.0 mg mL{sup -1} MWCNTs in 0.25 mg mL{sup -1} Polyhis solution prepared in 75:25 (v/v) ethanol/0.200 M acetate buffer solution pH 5.00. The dispersion was characterized by scanning electron microscopy, and by cyclic voltammetry and amperometry using ascorbic acid as redox marker. The modification of glassy carbon electrodes with MWCNT-Polyhis produces a drastic decrease in the overvoltage for the oxidation of ascorbic acid (580 mV) at variance with the response observed at glassy carbon electrodes modified just with Polyhis, where the charge transfer is more difficult due to the blocking effect of the polymer. The reproducibility for the sensitivities obtained after 10 successive calibration plots using the same surface was 6.3%. The MWCNT-modified glassy carbon electrode demonstrated to be highly stable since after 45 days storage at room temperature the response was 94.0% of the original. The glassy carbon electrode modified with MWCNT-Polyhis dispersion was successfully used to quantify dopamine or uric acid at nanomolar levels, even in the presence of large excess of ascorbic acid. Determinations of uric acid in human blood serum samples demonstrated a very good correlation with the value reported by Wienner laboratory.

  7. CO{sub 2} electroreduction: conversion into formic acid and mechanistic aspect in aqueous medium; Electroreduction du CO{sub 2}: conversion en acide formique et aspect mecanistique en milieu aqueux

    Energy Technology Data Exchange (ETDEWEB)

    Innocent, B.; Pasquier, D.; Ropital, F. [Institut Francais du Petrole (IFP), 92 - Rueil-Malmaison (France); Hahn, F.; Leger, J.M.; Kokoh, B. [Poitiers Univ., LaCCO, Equipe Electrocatalyse, UMR 6503 CNRS, 86 (France)

    2007-07-01

    The CO{sub 2} release reduction is nowadays considered as a necessity to limit the climatic change phenomena due to the greenhouse effect. For that, a part of CO{sub 2} could be transformed by its electrochemical reduction on a hydrogen overvoltage electrode as lead. According to the nature of the electrode material and of the electrolyte, CO{sub 2} can be electro catalytically hydrogenated or dimerized. In the conditions presented here (basic aqueous medium, lead electrode), the reagent is in majority reduced into formate, the parasite faradic reaction being the solvent transformation into dihydrogen. The studies carried out by cyclic voltametry have shown that the reducible form of CO{sub 2} is the hydrogeno-carbonate ion; its reduction begins at -1.2 V and reaches a maximum for an electrode potential of -1.6 V vs. ECS. Long intentiostatic electrolyses have then been carried out in an electrolytic circulation cell of 'filter-press' type. The cathode is a lead sheet of 20 cm{sup 2} and a current intensity of -100 mA has been imposed. The chromatographic analyses of the electrolytic solution have allowed to show that the formate selectivity is of 90%. The electroreduction process induces an acido-basic disequilibrium which induces a decrease of the reaction yield. A pH correction is then necessary to obtain great conversions of CO{sub 2} in alkaline medium (pH{>=}7) as follows: HCO{sub 3}{sup -} + H{sub 2}O + 2e{sup -} {yields} HCOO{sup -} + 2 HO{sup -}. In situ reflexion infrared spectroscopy studies, carried out in deuterated aqueous medium and by chrono-amperometry, have shown characteristic bands due to the hydrogeno-carbonate ion (weakly adsorbed) and to the formate produced, required for the understanding of the reactional mechanism. (O.M.)

  8. Direct Electrochemistry and Electrocatalysis of Horseradish Peroxidase Immobilized in a DNA/Chitosan-Fe3O4 Magnetic Nanoparticle Bio-Complex Film

    Directory of Open Access Journals (Sweden)

    Tingting Gu

    2014-02-01

    Full Text Available A DNA/chitosan-Fe3O4 magnetic nanoparticle bio-complex film was constructed for the immobilization of horseradish peroxidase (HRP on a glassy carbon electrode. HRP was simply mixed with DNA, chitosan and Fe3O4 nanoparticles, and then applied to the electrode surface to form an enzyme-incorporated polyion complex film. Scanning electron microscopy (SEM was used to study the surface features of DNA/chitosan/Fe3O4/HRP layer. The results of electrochemical impedance spectroscopy (EIS show that Fe3O4 and enzyme were successfully immobilized on the electrode surface by the DNA/chitosan bio-polyion complex membrane. Direct electron transfer (DET and bioelectrocatalysis of HRP in the DNA/chitosan/Fe3O4 film were investigated by cyclic voltammetry (CV and constant potential amperometry. The HRP-immobilized electrode was found to undergo DET and exhibited a fast electron transfer rate constant of 3.7 s−1. The CV results showed that the modified electrode gave rise to well-defined peaks in phosphate buffer, corresponding to the electrochemical redox reaction between HRP(Fe(III and HRP(Fe(II. The obtained electrode also displayed an electrocatalytic reduction behavior towards H2O2. The resulting DNA/chitosan/Fe3O4/HRP/glassy carbon electrode (GCE shows a high sensitivity (20.8 A·cm−2·M−1 toward H2O2. A linear response to H2O2 measurement was obtained over the range from 2 µM to 100 µM (R2 = 0.99 and an amperometric detection limit of 1 µM (S/N = 3. The apparent Michaelis-Menten constant of HRP immobilized on the electrode was 0.28 mM. Furthermore, the electrode exhibits both good operational stability and storage stability.

  9. Characterizing Enzymatic Deposition for Microelectrode Neurotransmitter Detection

    Energy Technology Data Exchange (ETDEWEB)

    Hosein, W. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Yorita, A. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tolosa, V. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-08-12

    The enzyme immobilization process, one step in creating an enzymatic biosensor, was characterized and analyzed as a function of its physical properties. The neural glutamic biosensor is a flexible device, effectively minimizing trauma to the area of implantation. The Multielectrode Array (MEA) is composed primarily of a proprietary polymer which has been successfully implanted into human subjects in recent years. This polymer allows the device the pliability that other devices normally lack, though this poses some challenges to implantation. The electrodes are made of Platinum (Pt), and can range in number from eight to thirty two electrodes per device. These electrodes are electroplated with a semipermeable polymer layer to improve selectivity of the electrode to the neurotransmitter of interest, in this case glutamate. A signal is created from the interaction of glutamate in the brain with the glutamate oxidase (GluOx) which is immobilized on the surface of the electrode by using crosslinking chemistry in conjunction with glutaraldehyde and Bovine Serum Albumin (BSA). The glutamate is oxidized by glutamate oxidase, producing α-ketoglutarate and hydrogen peroxide (H2O2) as a by-product. The production of H2O2 is crucial for detection of the presence of the glutamate within the enzymatic coating, as it diffuses through the enzyme layer and oxidizes at the surface of the electrode. This oxidation is detectable by measurable change in the current using amperometry. Hence, the MEA allows for in vivo monitoring of neurotransmitter activity in real time. The sensitivity of the sensor to these neurotransmitters is dependent on the thickness of the layer, which is investigated in these experiments in order to optimize the efficacy of the device to detecting the substrate, once implanted.

  10. Preparation and Electrocatalytic Application of Composites Containing Gold Nanoparticles Protected with Rhodium-Substituted Polyoxometalates

    Science.gov (United States)

    Wiaderek, Kamila M.; Cox, James A.

    2010-01-01

    Substitution of a metal center of phosphomolybdate, PMo12O403- (PMo12), or its tungsten analogue with dirhodium(II) and subsequent stabilization of gold nanoparticles, AuNPs, with Rh2PMo11 is demonstrated. The AuNP-Rh2PMo11 mediates oxidations but adsorbs too weakly for direct modification of electrode materials. Stability in quiescent solution was achieved by modifying glassy carbon (GC) with 3-aminopropyltriethoxysilane (APTES) and then electrostatically assembling AuNP-Rh2PMo11. At GC|APTES|AuNP-Rh2PMo11, cyclic voltammetry showed the expected set of three reversible peak-pairs for PMo11 in the range -0.2 to 0.6 vs (Ag/AgCl)/V and the reversible RhII,III couple at 1.0 vs (Ag/AgCl)/V. The presence of AuNPs increased the current for the reduction of bromate by a factor of 2.5 relative to that at GC|Rh2PMo11, and the electrocatalytic oxidation of methionine displayed characteristics of synergism between the AuNP and RhII. To stabilize AuNP-Rh2PMo11 on a surface in a flow system, GC was modified by electrochemically assisted deposition of a sol-gel with templated 10-nm pores prior to immobilizing the catalyst in the pores. The resulting electrode permitted determination of bromate by flow-injection amperometry with a detection limit of 4.0 × 10-8 mol dm-3. PMID:21499522

  11. Preparation and Electrocatalytic Application of Composites Containing Gold Nanoparticles Protected with Rhodium-Substituted Polyoxometalates.

    Science.gov (United States)

    Wiaderek, Kamila M; Cox, James A

    2011-04-01

    Substitution of a metal center of phosphomolybdate, PMo(12)O(40) (3-) (PMo(12)), or its tungsten analogue with dirhodium(II) and subsequent stabilization of gold nanoparticles, AuNPs, with Rh(2)PMo(11) is demonstrated. The AuNP-Rh(2)PMo(11) mediates oxidations but adsorbs too weakly for direct modification of electrode materials. Stability in quiescent solution was achieved by modifying glassy carbon (GC) with 3-aminopropyltriethoxysilane (APTES) and then electrostatically assembling AuNP-Rh(2)PMo(11). At GC|APTES|AuNP-Rh(2)PMo(11), cyclic voltammetry showed the expected set of three reversible peak-pairs for PMo(11) in the range -0.2 to 0.6 vs (Ag/AgCl)/V and the reversible Rh(II,III) couple at 1.0 vs (Ag/AgCl)/V. The presence of AuNPs increased the current for the reduction of bromate by a factor of 2.5 relative to that at GC|Rh(2)PMo(11), and the electrocatalytic oxidation of methionine displayed characteristics of synergism between the AuNP and Rh(II). To stabilize AuNP-Rh(2)PMo(11) on a surface in a flow system, GC was modified by electrochemically assisted deposition of a sol-gel with templated 10-nm pores prior to immobilizing the catalyst in the pores. The resulting electrode permitted determination of bromate by flow-injection amperometry with a detection limit of 4.0 × 10(-8) mol dm(-3).

  12. One dimensional CdS nanowire@TiO2 nanoparticles core-shell as high performance photocatalyst for fast degradation of dye pollutants under visible and sunlight irradiation.

    Science.gov (United States)

    Arabzadeh, Abbas; Salimi, Abdollah

    2016-10-01

    In this study, one-dimensional CdS nanowires@TiO2 nanoparticles core-shell structures (1D CdS NWs@TiO2 NPs) were synthesized by a facile wet chemical-solvothermal method. The different aspects of the properties of CdS NWs@TiO2 NPs were surveyed by using a comprehensive range of characterization techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-vis spectroscopy, scanning electron microscopy (SEM), fluorescence spectroscopy, energy dispersive X-ray spectroscopy (EDX), Cyclic Voltammetry (CV) and amperometry. The as-prepared nanostructure was applied as an effective photocatalyst for degradation of methyl orange (MO), methylene blue (MB) and rhodamine B (Rh B) under visible and sunlight irradiation. The results indicated significantly enhanced photocatalytic activity of CdS NWs@TiO2 NPs for degradation of MO, MB and Rh B compared to CdS NWs. The enhanced photocatalytic activity could be attributed to the enhanced sunlight absorbance and the efficient charge separation of the formed heterostructure between CdS NWs and TiO2. The results showed that MO, Rh B and MB were almost completely degraded after 2, 2 and 3min of exposure to sunlight, respectively; while under visible light irradiation (3W blue LED lamp) the dyes were decomposed with less half degradation rate. The catalytic activity was retained even after three degradation cycles of organic dyes, demonstrating that the proposed nanocomposite can be effectively used as efficient photocatalyst for removal of environmental pollutions caused by organic dyes under sunlight irradiation and it could be an important addition to the field of wastewater treatment. We hope the present study may open a new window of such 1-D semiconductor nanocomposites to be used as visible light photocatalysts in the promising field of organic dyes degradation.

  13. Central and peripheral contributions to dynamic changes in nucleus accumbens glucose induced by intravenous cocaine

    Directory of Open Access Journals (Sweden)

    Ken Taro Wakabayashi

    2015-02-01

    Full Text Available The pattern of neural, physiological and behavioral effects induced by cocaine is consistent with metabolic neural activation, yet direct attempts to evaluate central metabolic effects of this drug have produced controversial results. Here, we used enzyme-based glucose sensors coupled with high-speed amperometry in freely moving rats to examine how intravenous cocaine at a behaviorally active dose affects extracellular glucose levels in the nucleus accumbens (NAc, a critical structure within the motivation-reinforcement circuit. In drug-naive rats, cocaine induced a bimodal increase in glucose, with the first, ultra-fast phasic rise appearing during the injection (latency 6-8 s; ~50 µM or ~5% of baseline followed by a larger, more prolonged tonic elevation (~100 µM or 10% of baseline, peak ~15 min. While the rapid, phasic component of the glucose response remained stable following subsequent cocaine injections, the tonic component progressively decreased. Cocaine-methiodide, cocaine’s peripherally acting analog, induced an equally rapid and strong initial glucose rise, indicating cocaine’s action on peripheral neural substrates as its cause. However, this analog did not induce increases in either locomotion or tonic glucose, suggesting direct central mediation of these cocaine effects. Under systemic pharmacological blockade of dopamine transmission, both phasic and tonic components of the cocaine-induced glucose response were only slightly reduced, suggesting a significant role of non-dopamine mechanisms in cocaine-induced accumbal glucose influx. Hence, intravenous cocaine induces rapid, strong inflow of glucose into NAc extracellular space by involving both peripheral and central, non-dopamine drug actions, thus preventing a possible deficit resulting from enhanced glucose use by brain cells.

  14. Spontaneous Water Oxidation at Hematite (α-Fe2O3) Crystal Faces

    Energy Technology Data Exchange (ETDEWEB)

    Chatman, Shawn ME; Zarzycki, Piotr P.; Rosso, Kevin M.

    2015-01-28

    Hematite (α-Fe2O3) persists as a promising candidate for photoelectrochemical water splitting but a slow oxygen evolution reaction (OER) at its surfaces remains a limitation. Here we extend a series of studies that examine pH-dependent surface potentials and electron transfer properties of effectively perfect low-index crystal faces of hematite in contact with simple electrolyte. Zero resistance amperometry was performed in a two electrode configuration to quantify spontaneous dark current between hematite crystal face pairs (001)/(012), (001)/(113), and (012)/(113) at pH 3. Exponentially decaying currents initially of up to 200 nA were reported between faces over four minute experiments. Fourth order ZRA kinetics indicated rate limitation by the OER for current that flows between (001)/(012) and (001)/(113) face pairs, with the (012) and (113) faces serving as the anodes when paired with (001). The cathodic partner reaction is reductive dissolution of the (001) face, converting surface Fe3+ to solubilized aqueous Fe2+, at a rate maintained by the OER at the anode. In contrast, OER rate limitation does not manifest for the (012)/(113) pair. The uniqueness of the (001) face is established in terms of a faster intrinsic ability to accept the protons required for the reductive dissolution reaction. OER rate limitation inversely may thus arise from sluggish kinetics of hematite surfaces to dispense with the protons that accompany the four-electron OER. The results are explained in terms of semi-quantitative energy band diagrams. The finding may be useful as a consideration for tailoring the design of polycrystalline hematite photoanodes that present multiple terminations to the interface with electrolyte.

  15. 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. PMID:27485503

  16. Rapid fluctuations in extracellular brain glucose levels induced by natural arousing stimuli and intravenous cocaine: fueling the brain during neural activation

    Science.gov (United States)

    Lenoir, Magalie

    2012-01-01

    Glucose, a primary energetic substrate for neural activity, is continuously influenced by two opposing forces that tend to either decrease its extracellular levels due to enhanced utilization in neural cells or increase its levels due to entry from peripheral circulation via enhanced cerebral blood flow. How this balance is maintained under physiological conditions and changed during neural activation remains unclear. To clarify this issue, enzyme-based glucose sensors coupled with high-speed amperometry were used in freely moving rats to evaluate fluctuations in extracellular glucose levels induced by brief audio stimulus, tail pinch (TP), social interaction with another rat (SI), and intravenous cocaine (1 mg/kg). Measurements were performed in nucleus accumbens (NAcc) and substantia nigra pars reticulata (SNr), which drastically differ in neuronal activity. In NAcc, where most cells are powerfully excited after salient stimulation, glucose levels rapidly (latency 2–6 s) increased (30–70 μM or 6–14% over baseline) by all stimuli; the increase differed in magnitude and duration for each stimulus. In SNr, where most cells are transiently inhibited by salient stimuli, TP, SI, and cocaine induced a biphasic glucose response, with the initial decrease (−20–40 μM or 5–10% below baseline) followed by a reboundlike increase. The critical role of neuronal activity in mediating the initial glucose response was confirmed by monitoring glucose currents after local microinjections of glutamate (GLU) or procaine (PRO). While intra-NAcc injection of GLU transiently increased glucose levels in this structure, intra-SNr PRO injection resulted in rapid, transient decreases in SNr glucose. Therefore, extracellular glucose levels in the brain change very rapidly after physiological and pharmacological stimulation, the response is structure specific, and the pattern of neuronal activity appears to be a critical factor determining direction and magnitude of physiological

  17. Fully Enzymatic Membraneless Glucose|Oxygen Fuel Cell That Provides 0.275 mA cm(-2) in 5 mM Glucose, Operates in Human Physiological Solutions, and Powers Transmission of Sensing Data.

    Science.gov (United States)

    Ó Conghaile, Peter; Falk, Magnus; MacAodha, Domhnall; Yakovleva, Maria E; Gonaus, Christoph; Peterbauer, Clemens K; Gorton, Lo; Shleev, Sergey; Leech, Dónal

    2016-02-16

    Coimmobilization of pyranose dehydrogenase as an enzyme catalyst, osmium redox polymers [Os(4,4'-dimethoxy-2,2'-bipyridine)2(poly(vinylimidazole))10Cl](+) or [Os(4,4'-dimethyl-2,2'-bipyridine)2(poly(vinylimidazole))10Cl](+) as mediators, and carbon nanotube conductive scaffolds in films on graphite electrodes provides enzyme electrodes for glucose oxidation. The recombinant enzyme and a deglycosylated form, both expressed in Pichia pastoris, are investigated and compared as biocatalysts for glucose oxidation using flow injection amperometry and voltammetry. In the presence of 5 mM glucose in phosphate-buffered saline (PBS) (50 mM phosphate buffer solution, pH 7.4, with 150 mM NaCl), higher glucose oxidation current densities, 0.41 mA cm(-2), are obtained from enzyme electrodes containing the deglycosylated form of the enzyme. The optimized glucose-oxidizing anode, prepared using deglycosylated enzyme coimmobilized with [Os(4,4'-dimethyl-2,2'-bipyridine)2(poly(vinylimidazole))10Cl](+) and carbon nanotubes, was coupled with an oxygen-reducing bilirubin oxidase on gold nanoparticle dispersed on gold electrode as a biocathode to provide a membraneless fully enzymatic fuel cell. A maximum power density of 275 μW cm(-2) is obtained in 5 mM glucose in PBS, the highest to date under these conditions, providing sufficient power to enable wireless transmission of a signal to a data logger. When tested in whole human blood and unstimulated human saliva maximum power densities of 73 and 6 μW cm(-2) are obtained for the same fuel cell configuration, respectively. PMID:26750758

  18. Electrochemical reduction of lindane (γ-HCH) at NiCo2O4 modified electrode

    International Nuclear Information System (INIS)

    Highlights: • NiCo2O4, NiFe2O4, NiO, Co3O4, and Fe3O4 were synthesized by the hydrothermal route. • Modified electrodes based on these metal oxides were investigated in lindane reduction. • NiCo2O4 modified electrode exhibited the highest activity. • Reproducibility, stability, and interference studies were performed. -- Abstract: NiCo2O4 and NiFe2O4 were synthesized by the hydrothermal route using the molar composition, 2.2 CoCl2·6H2O:1.0 NiCl2·6H2O:9 urea:832 H2O and 2.2 FeCl2·4H2O:1.0 NiCl2·6H2O:9 urea:832 H2O, respectively. For the comparative study, NiO, Co3O4, and Fe3O4 were also prepared. Materials were characterized by a complementary combination of X-ray diffraction, nitrogen sorption, and Scanning electron microscopy. Non-enzymatic electrochemical sensors (using above-mentioned metal oxides) were constructed for the detection of lindane in the aqueous-methanol medium. Electrochemical techniques such as cyclic voltammetry, differential pulse voltammetry, and amperometry were used for the detection of lindane. Reproducibility, stability, and interference studies were performed to obtain the suitable non-enzymatic sensor. The analytical performance of the sensor was demonstrated for the detection of lindane in tap water samples

  19. Fusion Pore Size Limits 5-HT Release From Single Enterochromaffin Cell Vesicles.

    Science.gov (United States)

    Raghupathi, Ravinarayan; Jessup, Claire F; Lumsden, Amanda L; Keating, Damien J

    2016-07-01

    Enterochromaffin cells are the major site of serotonin (5-HT) synthesis and secretion providing ∼95% of the body's total 5-HT. 5-HT can act as a neurotransmitter or hormone and has several important endocrine and paracrine roles. We have previously demonstrated that EC cells release small amounts of 5-HT per exocytosis event compared to other endocrine cells. We utilized a recently developed method to purify EC cells to demonstrate the mechanisms underlying 5-HT packaging and release. Using the fluorescent probe FFN511, we demonstrate that EC cells express VMAT and that VMAT plays a functional role in 5-HT loading into vesicles. Carbon fiber amperometry studies illustrate that the amount of 5-HT released per exocytosis event from EC cells is dependent on both VMAT and the H(+)-ATPase pump, as demonstrated with reserpine or bafilomycin, respectively. We also demonstrate that increasing the amount of 5-HT loaded into EC cell vesicles does not result in an increase in quantal release. As this indicates that fusion pore size may be a limiting factor involved, we compared pore diameter in EC and chromaffin cells by assessing the vesicle capture of different-sized fluorescent probes to measure the extent of fusion pore dilation. This identified that EC cells have a reduced fusion pore expansion that does not exceed 9 nm in diameter. These results demonstrate that the small amounts of 5-HT released per fusion event in EC cells can be explained by a smaller fusion pore that limits 5-HT release capacity from individual vesicles. PMID:26574734

  20. Alpha-Glucosidase Enzyme Biosensor for the Electrochemical Measurement of Antidiabetic Potential of Medicinal Plants

    Science.gov (United States)

    Mohiuddin, M.; Arbain, D.; Islam, A. K. M. Shafiqul; Ahmad, M. S.; Ahmad, M. N.

    2016-02-01

    A biosensor for measuring the antidiabetic potential of medicinal plants was developed by covalent immobilization of α-glucosidase (AG) enzyme onto amine-functionalized multi-walled carbon nanotubes (MWCNTs-NH2). The immobilized enzyme was entrapped in freeze-thawed polyvinyl alcohol (PVA) together with p-nitrophenyl-α- d-glucopyranoside (PNPG) on the screen-printed carbon electrode at low pH to prevent the premature reaction between PNPG and AG enzyme. The enzymatic reaction within the biosensor is inhibited by bioactive compounds in the medicinal plant extracts. The capability of medicinal plants to inhibit the AG enzyme on the electrode correlates to the potential of the medicinal plants to inhibit the production of glucose from the carbohydrate in the human body. Thus, the inhibition indicates the antidiabetic potential of the medicinal plants. The performance of the biosensor was evaluated to measure the antidiabetic potential of three medicinal plants such as Tebengau ( Ehretis laevis), Cemumar ( Micromelum pubescens), and Kedondong ( Spondias dulcis) and acarbose (commercial antidiabetic drug) via cyclic voltammetry, amperometry, and spectrophotometry. The cyclic voltammetry (CV) response for the inhibition of the AG enzyme activity by Tebengau plant extracts showed a linear relation in the range from 0.423-8.29 μA, and the inhibition detection limit was 0.253 μA. The biosensor exhibited good sensitivity (0.422 μA/mg Tebengau plant extracts) and rapid response (22 s). The biosensor retains approximately 82.16 % of its initial activity even after 30 days of storage at 4 °C.

  1. Electrochemical Assay of Effects of Organophosphate Poisoning on Acetylcholinesterase from Pheretima via2,6-Dimethyl-p-benzoquinone

    Institute of Scientific and Technical Information of China (English)

    WU Wu-ai; LI Jun; GAO Bao-ping; GUO Man-dong

    2012-01-01

    Electroanalytical techniques could be a reliable and promising alternative to classical and sophisticatcd methods because of their simplicity(small and portable),easy use,the ability to deliver fast response with high sensitivity and selectivity.A square wave voltammetric method was developed for the assessment of organophosphorus(OPs) compound impact on acetylcholinesterase(AChE) of Pheretima with 2,6-dimethyl-p-benzoquinone(2,6-DMBQ) as a redox indicator.The substrate of acetylthiocholine is hydrolyzed by AChE and the produced thiocholine reacts with 2,6-DMBQ to give an obvious shift of electrochemical signal.The reduction peak of 2,6-DMBQ is located at around -0.18 V which is far away from the oxidation potential of possible interference components often present in biosample.The decreased rate of reduction current was related with the activity of AChE.The inhibition of parathion-methyl on AChE was assessed.The inhibiton rate of OPs on AChE activity increased quickly during the first 10min inhibition,and after that the value of inhibition rate approached to be constant.AChE lost almost 29.3% of activity after 10 min incubation with 1 μg/mL parathion-methyl and 67.5% of activity with 10 μg/mL parathion-methyl,while the activity that corresponds to 40 μg/mL parathion-methyl was nearly completely inhibited(94.9%).Compared to cyclic voltammetry and amperometry,Square wave voltammetry(SWV) method is a high sensitive electroanalysis with fast scan-rate(only several seconds for one signal value) which is useful to prevent the electrodes from possible fouling or passivation.This method can be employed to assess the inhibition of organophosphate on AChE and investigate OPs impact on environmental animals.

  2. Imidazoline derivative templated synthesis of broccoli-like Bi2S3 and its electrocatalysis towards the direct electrochemistry of hemoglobin.

    Science.gov (United States)

    Chen, Xiaoqian; Wang, Qingxiang; Wang, Liheng; Gao, Feng; Wang, Wei; Hu, Zhengshui

    2015-04-15

    A broccoli-like bismuth sulfide (bBi2S3) was synthesized via a solvothermal method using a self-made imidazoline derivative of 2-undecyl-1-dithioureido-ethyl-imidazoline as the soft template. The morphology and chemical constitution of the product were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Electrochemical characterization experiments show that the bBi2S3 has the higher specific surface area and standard heterogeneous electron transfer rate constant than the rod-like Bi2S3 (rBi2S3). Hemoglobin (Hb) was then chosen as a protein model to investigate the electrocatalytic property of the synthesized bBi2S3. The results show that Hb entrapped in the composite film of chitosan and bBi2S3 displays an excellent direct electrochemistry, and retains its biocatalytic activity toward the electro-reduction of hydrogen peroxide. The current response in the amperometry shows a linear response to H2O2 concentrations in the range from 0.4 to 4.8µM with high sensitivity (444µAmM(-1)) and low detection limit (0.096µM). The Michaelis-Menten constant (KM(app)) of the fabricated bioelectrode for H2O2 was determined as low as 1µM. These results demonstrate that the synthesized bBi2S3 offers a new path for the immobilization of redox-active protein and the construction of the third-generation biosensors. PMID:25437355

  3. Isolation of a novel uric-acid-degrading microbe Comamonas sp. BT UA and rapid biosensing of uric acid from extracted uricase enzyme

    Indian Academy of Sciences (India)

    Tanushree Ghosh; Priyabrata Sarkar

    2014-12-01

    Uric-acid-utilizing soil bacteria were isolated, and 16s rRNA sequence was studied for strain identification. The most prominent uricase-producing bacterium was identified as Comamonas sp BT UA. Crude enzyme was extracted, freeze-dried and its Km and Vmax were determined as 40 M and 0.047 M min−1ml−1 using Line-weaver Burke plot. An activity of 80 U/mg of total protein was observed when cultured at 37°C for 84 h at pH 7. The purified enzyme was used to measure uric acid by spectrophotometric method and electrochemical biosensor. In the biosensing system the enzyme was immobilized on the platinum electrode with a biodegradable glutaraldehyde-crosslinked gelatin film having a swelling percentage of 109±3.08, and response was observed by amperometry applying fixed potential. The electrochemical process as obtained by the anodic peak current and scan rate relationship was further configured by electrochemical impedance spectroscopy (EIS). The polymer matrix on the working electrode gave capacitive response for the electrode–electrolyte interaction. The sensitivity of the biosensor was measured as 6.93 AM−1 with a sensor affinity [m(app)] of 50 M and 95% reproducibility after 50 measurements. The spectrophotometric method could be used in the range of 6–1000 M, whereas the biosensor generated linear response in the 1.5–1000 M range with a response time of 24 s and limit of detection of 0.56 M. Uric acid was estimated in human blood samples by the biosensor and satisfactory results were obtained.

  4. Electrochemical dissolved oxygen removal from microfluidic streams for LOC sample pretreatment.

    Science.gov (United States)

    Marei, Mohamed M; Roussel, Thomas J; Keynton, Robert S; Baldwin, Richard P

    2014-09-01

    Current water quality monitoring for heavy metal contaminants largely results in analytical snapshots at a particular time and place. Therefore, we have been interested in miniaturized and inexpensive sensors suitable for long-term, real-time monitoring of the drinking water distribution grid, industrial wastewater effluents, and even rivers and lakes. Among the biggest challenges for such sensors are the issues of in-field device calibration and sample pretreatment. Previously, we have demonstrated use of coulometric stripping analysis for calibration-free determination of copper and mercury. For more negatively reduced metals, O2 reduction interferes with stripping analysis; hence, most electroanalysis techniques rely on pretreatments to remove dissolved oxygen (DO). Current strategies for portable DO removal offer limited practicality, because of their complexity, and often cause inadvertent sample alterations. Therefore, we have designed an indirect in-line electrochemical DO removal device (EDOR), utilizing a silver cathode to reduce DO in a chamber that is fluidically isolated from the sample stream by an O2-permeable membrane. The resulting concentration gradient supports passive DO diffusion from the sample stream into the deoxygenation chamber. The DO levels in the sample stream were determined by cyclic voltammetry (CV) and amperometry at a custom thin-layer cell (TLC) detector. Results show removal of 98% of the DO in a test sample at flow rates approaching 50 μL/min and power consumption as low as 165 mW h L(-1) at steady state. Besides our specific stripping application, this device is well-suited for LOC applications where miniaturized DO removal and/or regulation are desirable. PMID:25082792

  5. Hierarchical 3-dimensional nickel-iron nanosheet arrays on carbon fiber paper as a novel electrode for non-enzymatic glucose sensing.

    Science.gov (United States)

    Kannan, Palanisamy; Maiyalagan, Thandavarayan; Marsili, Enrico; Ghosh, Srabanti; Niedziolka-Jönsson, Joanna; Jönsson-Niedziolka, Martin

    2016-01-14

    Three-dimensional nickel-iron (3-D/Ni-Fe) nanostructures are exciting candidates for various applications because they produce more reaction-active sites than 1-D and 2-D nanostructured materials and exhibit attractive optical, electrical and catalytic properties. In this work, freestanding 3-D/Ni-Fe interconnected hierarchical nanosheets, hierarchical nanospheres, and porous nanospheres are directly grown on a flexible carbon fiber paper (CFP) substrate by a single-step hydrothermal process. Among the nanostructures, 3-D/Ni-Fe interconnected hierarchical nanosheets show excellent electrochemical properties because of its high conductivity, large specific active surface area, and mesopores on its walls (vide infra). The 3-D/Ni-Fe hierarchical nanosheet array modified CFP substrate is further explored as a novel electrode for electrochemical non-enzymatic glucose sensor application. The 3-D/Ni-Fe hierarchical nanosheet arrays exhibit significant catalytic activity towards the electrochemical oxidation of glucose, as compared to the 3-D/Ni-Fe hierarchical nanospheres, and porous nanospheres. The 3-D/Ni-Fe hierarchical nanosheet arrays can access a large amount of glucose molecules on their surface (mesopore walls) for an efficient electrocatalytic oxidation process. Moreover, 3-D/Ni-Fe hierarchical nanosheet arrays showed higher sensitivity (7.90 μA μM(-1) cm(-2)) with wide linear glucose concentration ranging from 0.05 μM to 0.2 mM, and the low detection limit (LOD) of 0.031 μM (S/N = 3) is achieved by the amperometry method. Further, the 3-D/Ni-Fe hierarchical nanosheet array modified CFP electrode can be demonstrated to have excellent selectivity towards the detection of glucose in the presence of 500-fold excess of major important interferents. All these results indicate that 3-D/Ni-Fe hierarchical nanosheet arrays are promising candidates for non-enzymatic glucose sensing. PMID:26578259

  6. Amperometric L-glutamate biosensor based on bacterial cell-surface displayed glutamate dehydrogenase

    International Nuclear Information System (INIS)

    Highlights: • E. coli surface-dispalyed Gldh exhibiting excellent enzyme activity and stability. • Sensitive amperometric biosensor for glutamate using Gldh-bacteria and MWNTs. • The glutamate biosensor exhibited high specificity and stability. - Abstract: A novel L-glutamate biosensor was fabricated using bacteria surface-displayed glutamate dehydrogenase (Gldh-bacteria). Here the cofactor NADP+-specific dependent Gldh was expressed on the surface of Escherichia coli using N-terminal region of ice nucleation protein (INP) as the anchoring motif. The cell fractionation assay and SDS-PAGE analysis indicated that the majority of INP-Gldh fusion proteins were located on the surface of cells. The biosensor was fabricated by successively casting polyethyleneimine (PEI)-dispersed multi-walled carbon nanotubes (MWNTs), Gldh-bacteria and Nafion onto the glassy carbon electrode (Nafion/Gldh-bacteria/PEI-MWNTs/GCE). The MWNTs could not only significantly lower the oxidation overpotential towards NAPDH, which was the product of NADP+ involving in the oxidation of glutamate by Gldh, but also enhanced the current response. Under the optimized experimental conditions, the current–time curve of the Nafion/Gldh-bacteria/PEI-MWNTs/GCE was performed at +0.52 V (vs. SCE) by amperometry varying glutamate concentration. The current response was linear with glutamate concentration in two ranges (10 μM–1 mM and 2–10 mM). The low limit of detection was estimated to be 2 μM glutamate (S/N = 3). Moreover, the proposed biosensor is stable, specific, reproducible and simple, which can be applied to real samples detection

  7. Stimulation-Evoked Dopamine Release in the Nucleus Accumbens Following Cocaine Administration in Rats Perinatally Exposed to Polychlorinated Biphenyls

    Science.gov (United States)

    Sable, Helen J. K.

    2013-01-01

    Exposure to polychlorinated biphenyls (PCBs) alters brain dopamine (DA) concentrations and DA receptor/transporter function, suggesting the reinforcing properties of drugs of abuse acting on the DA system may be affected by PCB exposure. Female Long-Evans rats were orally exposed to 0, 3, or 6mg/kg/day PCBs from 4 weeks prior to breeding until litters were weaned on postnatal day 21. In vivo fixed potential amperometry (FPA) was used in adult anesthetized offspring to determine whether perinatal PCB exposure altered (1) presynaptic DA autoreceptor (DAR) sensitivity, (2) electrically evoked nucleus accumbens (NAc) DA efflux following administration of cocaine, and (3) the rate of depletion of presynaptic DA stores. One adult male and female littermate were tested using FPA following a single injection of cocaine (20mg/kg ip), whereas a second adult male and female littermate were tested following the last of seven daily cocaine injections of the same dose. The carbon fiber recording microelectrode was positioned in the NAc core, and DA oxidation currents (i.e., DA release) evoked by brief stimulation of the medial forebrain bundle (MFB) were quantified before and after administration of cocaine. PCB-exposed rats exhibited enhanced stimulation-evoked DA release (relative to baseline) following a single injection of cocaine. Although nonexposed controls exhibited typical DA sensitization following repeated cocaine administration, this effect was attenuated in PCB-exposed rats. In addition, DAR sensitivity was higher (males only), and the rate of depletion of presynaptic DA stores was greater in PCB-exposed animals relative to nonexposed controls. These results indicate that perinatal PCB exposure can modify DA synaptic transmission in the NAc in a manner previously shown to alter the reinforcing properties of cocaine. PMID:23912914

  8. A PC-controlled voltage pulse generator for electroanalytical applications

    Science.gov (United States)

    Heredia-López, Francisco J.; Góngora-Alfaro, José L.; Alvarez-Cervera, Fernando J.; Bata-García, José Luis

    1997-04-01

    We present the design of a voltage pulse generator controlled by an IBM or compatible AT Personal Computer (PC) capable of synthesizing some of the voltage pulse wave forms commonly used in electrochemical studies. The included signals are: differential pulse voltametry, differential normal pulse voltametry, and differential pulse amperometry. Additionally, a triangular wave form and a constant-voltage signal, used in the pretreatment of carbon fiber microelectrodes for neurochemical analysis, are also available. Operating the generator imposes a minimum of restrictions on the specification of the duration, amplitude, and type of wave shapes. Low-cost PC-based design allows for compatibility, portability, and versatility. The operating ranges of the wave form parameters for the three voltametric signals are: initial voltage, -0.9-+0.9 V; step amplitude, 0.1-900 mV; period, 6 ms-60 s; measuring pulse amplitude, 0.1-900 mV; measuring pulse duration, 2 ms-20 s; prepulse duration, 2 ms-20 s. In the electrode pretreatment mode, the operating ranges are: amplitude, 0-±5 V; duration, unlimited; frequency, 15-240 Hz. The generator uses its own time base for the generation of all signals, thereby rendering it independent of processor clock speed or power-line frequency. The results of the experimental evaluation indicate that the system is accurate within ±10% of the expected values, taking into account the errors associated with the signal synthesis and the digitizing process. The maximum achievable scan rate is 500 V/s, and the highest frequency for the triangular wave form is 240 Hz. Therefore, the pulse generator could be used for fast cyclic voltametry (FCV). FCV and other wave forms could be added through software modules, without any hardware changes. We conclude that the PC-based electrochemistry pulse generator represents an economical and flexible alternative for electroanalytical applications.

  9. Synthesis and characterization of cobalt-nichel oxides for the oxygen formation reaction

    International Nuclear Information System (INIS)

    In this work the compounds of cobalt and nickel oxides and the mixtures of cobalt-nickel were prepared which were characterized and evaluated as electrocatalysts in the oxygen release reaction in alkaline media. The compounds were synthesised by the sol-gel method: heated at 400 and 500 Centigrade. The compounds characterization was realized by thermogravimetry, X-ray diffraction and Scanning electron microscopy. As the Co3O4 and the Ni O as the mixtures Ni O/Co3O4 were obtained as a porous material with a small particle size, characteristics which are presented by cause of the low temperature of synthesis. The electrocatalytic evaluation for the synthesised compounds for the oxygen release reaction was realized by cyclic volt amperometry in a 0.5M KOH solution. The oxides mixtures presented a well electrocatalytic activity to be used in the electrochemical release of oxygen. The current density and the electrochemically active area, in all the cases of mixtures is very higher to the Co3O4 and Ni O ones. Observing with greater clearness the synergic effects, in the obtained mixture at 400 C. The oxides mixtures heated at 400 C were stables for the oxygen formation reaction. Therefore it is be able to say that the Ni O/Co3O4 mixture counts on a great reactive area: electrocatalytic characteristic desirable to be a material used as anode in the electrolysis of water, which increases the oxygen release in the anode and so the hydrogen release in the cathode. (Author)

  10. Biosensor de Glucosa basado en un Biocompósito disperso de Grafito-Epoxi-Platino-Glucosa Oxidasa Glucose Biosensor based on a Graphite-Epoxy-Platimum- Glucose Oxidase dispersed Biocomposite

    Directory of Open Access Journals (Sweden)

    José L Montañez

    2011-01-01

    Full Text Available El objetivo del trabajo consistió en desarrollar un biosensor de glucosa basado en las propiedades electroquímicas de un compósito grafito-epoxi-platino-glucosa oxidasa. La industria de alimentos y bebidas demanda métodos analíticos rápidos, precisos y confiables para evaluar y asegurar la calidad de sus productos y optimizar sus procesos. El desarrollo de biosensores enzimáticos amperométricos representa una opción viable que satisface estos requerimientos. El potencial de trabajo y la caracterización de la respuesta del biosensor desarrollado se determinaron por voltamperometría de barrido lineal y amperometría, respectivamente. La respuesta del biosensor fue máxima a 600 mV, su tiempo de respuesta fue de 20 segundos en un intervalo de concentración de respuesta lineal de 0.1 a 5 mM de glucosa y sensibilidad de 1.4 μA/mM. La estabilidad y vida útil del biosensor desarrollado dependen de la frecuencia de uso y el biocompósito actúa como reservorio de enzimas y de mediador electroquímico.The aim of this work was to develop a glucose biosensor based on electrochemical properties of a graphite-epoxy-platinum- glucose oxidase composite. The food and beverage industry demand fast, precise and reliable analytical methods to evaluate and to assure the quality of its products and to optimize its processes. The development of amperometric enzyme biosensors represents a viable option that satisfies these requirements. The working potential and the characterization of the response of the biosensor were determined by cyclic voltammetry and amperometry, respectively. The biosensor response was máximum at 600 mV, with a response time of 20 seconds within the concentration range of linear response from 0.1 to 5 mM glucose and sensitivity of 1.4 μA/mM. The stability and lifetime of the proposed biosensor depend on the frequency of use, where the biocomposite acts as a reservoir of enzymes and electrochemical mediator.

  11. A biosensor based on the self-entrapment of glucose oxidase within biomimetic silica nanoparticles induced by a fusion enzyme.

    Science.gov (United States)

    Choi, Okkyoung; Kim, Byung-Chun; An, Ji-Hye; Min, Kyoungseon; Kim, Yong Hwan; Um, Youngsoon; Oh, Min-Kyu; Sang, Byoung-In

    2011-10-10

    We constructed a fusion protein (GOx-R5) consisting of R5 (a polypeptide component of silaffin) and glucose oxidase (GOx) that was expressed in Pichia pastoris. Silaffin proteins are responsible for the formation of a silica-based cell matrix of diatoms, and synthetic variants of the R5 protein can perform silicification in vitro[1]. GOx secreted by P. pastoris was self-immobilized (biosilicification) in a pH 5 citric buffer using 0.1M tetramethoxysilane as a silica source. This self-entrapment property of GOx-R5 was used to immobilize GOx on a graphite rod electrode. An electric cell designed as a biosensor was prepared to monitor the glucose concentrations. The electric cell consisted of an Ag/AgCl reference electrode, a platinum counter electrode, and a working electrode modified with poly(neutral red) (PNR)/GOx/Nafion. Glucose oxidase was immobilized by fused protein on poly(neutral red) and covered by Nafion to protect diffusion to the solution. The morphology of the resulting composite PNR/GOx/Nafion material was analyzed by scanning electron microscopy (SEM). This amperometric transducer was characterized electrochemically using cyclic voltammetry and amperometry in the presence of glucose. An image produced by scanning electron microscopy supported the formation of a PNR/GOx complex and the current was increased to 1.58 μA cm(-1) by adding 1mM glucose at an applied potential of -0.5 V. The current was detected by way of PNR-reduced hydrogen peroxide, a product of the glucose oxidation by GOx. The detection limit was 0.67mM (S/N=3). The biosensor containing the graphite rod/PNR/GOx/Nafion detected glucose at various concentrations in mixed samples, which contained interfering molecules. In this study, we report the first expression of R5 fused to glucose oxidase in eukaryotic cells and demonstrate an application of self-entrapped GOx to a glucose biosensor. PMID:22112615

  12. 聚酚藏花红功能碳纳米管生物阳极制备及其在乙醇传感器应用%Development of Dehydrogenase-Based Bioanode Using Poly(Phenosafranin)-Functionalized SWCNT Nanocomposites and its Application to Ethanol Biosensor

    Institute of Scientific and Technical Information of China (English)

    Farhana S.Saleh; Takeyoshi Okajima; 毛兰群; 大坂武男

    2011-01-01

    A New type of dehydrogenase-based amperometric ethanol biosensor was constructed using alcohol dehydrogenase(ADH) which was immobilized on the edge-plane pyrolytic graphite(EPPG) electrode modified with poly(phenosafranin)-functionalized single-walled carbon nanotube(PPS-SWCNT).The PPS-SWCNT modified EPPG electrode was prepared by electropolymerization of phenosafranin on the EPPG electrode which was previously coated with SWCNT.The performance of the ADH/PPS-SWCNT/EPPG electrode was evaluated using cyclic voltammetry and amperometry in the presence of ethanol.The fabricated ethanol biosensor provided a reasonable sensitivity of 2.0 μA·cm-2·mmol-1·L and a low detection limit(36 μmol·L-1) for the electrocatalytic oxidation of ethanol with a linear concentration dependence upto~1.0 mmol·L-1 at a detection potential of 0.2 V.%应用电化学法聚合酚藏花红(PPS)功能化的单壁碳纳米管,以其作为烟酰胺辅酶(NADH)氧化的电化学催化剂(电极),构建基于乙醇脱氢酶的安培型乙醇生物电化学传感器.该电极于0.0 V时,对NADH具有很好的催化性能.而单体酚藏花红则由于其电位过低(-0.48 V),不能显示催化性能.循环伏安和计时安培法测试表明:该传感器的碳纳米管的载量,固定化酶的量,NAD+的浓度以及溶液的pH都能直接影响它的性能.经优化制备的乙醇传感器在0.2 V电位下,对乙醇响应的灵敏度为2.0μA.cm-2.mM-1,检测限为36μmol.L-1.表现出很好的稳定性,连续测定45 min后,响应电流下降仅为起始值的7%.本文的研究为电化学生物传感器的创新开发提供了新的思路.

  13. Amperometric microsensor for direct probing of ascorbic acid in human gastric juice

    Energy Technology Data Exchange (ETDEWEB)

    Hutton, Emily A.; Pauliukaite, Rasa; Hocevar, Samo B. [Analytical Chemistry Laboratory, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana (Slovenia); Ogorevc, Bozidar, E-mail: bogorevc@ki.s [Analytical Chemistry Laboratory, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana (Slovenia); Smyth, Malcolm R. [National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin 9 (Ireland)

    2010-09-30

    This article reports on a novel microsensor for amperometric measurement of ascorbic acid (AA) under acidic conditions (pH 2) based on a carbon fiber microelectrode (CFME) modified with nickel oxide and ruthenium hexacyanoferrate (NiO-RuHCF). This sensing layer was deposited electrochemically in a two-step procedure involving an initial galvanostatic NiO deposition followed by a potentiodynamic RuHCF deposition from solutions containing the precursor salts. Several important parameters were examined to characterize and optimize the NiO-RuHCF sensing layer with respect to its current response to AA by using cyclic voltammetry, and scanning electron microscopy-energy dispersive X-ray spectroscopy methods. With the NiO-RuHCF coated CFME, the AA oxidation potential under acidic conditions was shifted to a less positive value for about 0.2 V (E{sub p} of ca. 0.23 V vs. Ag/AgCl) as compared to a bare CFME, which greatly improves the electrochemical selectivity. Using the hydrodynamic amperometry mode, the current vs. AA concentration in 0.01 M HCl, at a selected operating potential of 0.30 V, was found to be linear over a wide range of 10-1610 {mu}M (n = 22, r = 0.999) with a calculated limit of detection of 1.0 {mu}M. The measurement repeatability was satisfactory with a relative standard deviation (r.s.d.) ranging from 4% to 5% (n = 6), depending on the AA concentration, and with a sensor-to-sensor reproducibility (r.s.d.) of 6.9% at 100 {mu}M AA. The long-term reproducibility, using the same microsensor for 112 consecutive measurements of 20 {mu}M AA over 11 h of periodic probing sets over 4 days, was 16.1% r.s.d., thus showing very good stability at low AA levels and suitability for use over a prolonged period of time. Moreover, using the proposed microsensor, additionally coated with a protective cellulose acetate membrane, the calibration plot obtained in the extremely complex matrix of real undiluted gastric juice was linear from 10 to 520 {mu}M (n = 14, r = 0

  14. Synthesis and Catalytic Property of Flaked Spindle-Like CuO Nanocrystals%片层纺锤形纳米CuO的制备及性能研究

    Institute of Scientific and Technical Information of China (English)

    范建凤; 李丽青; 黄玉峰; 范楼珍

    2011-01-01

    A simple and efficient electrochemical route was developed for the synthesis of flaked spindle-like CuO nanocrystals using aqueous electrolyte and Cu sacrificial anode (graphite as the cathode) in an undivided cell at a constant potential mode under room temperature. The morphology, structure and component of CuO nanocrystals obtained were characterized by SEM and XRD. Flaked spindle-like CuO nanocrystals were successfully used to modify a GC electrode to detect H2O2 with cyclic voltammetry (CV) and amperometry (AC). The results showed that the products were pure monoclinic CuO nanocrystals. The linear range for the determination of hydrogen peroxide is from 1.0 μmol · L-1 to 1.0 mmol· L-1, the detection limit is 0.5 μmol · L-1, which suggests that the flaked spindle-like CuO nanocrystals may be of great potential for H2O2 electrochemical sensing.%室温下,以高纯铜片为阳极,石墨棒为阴极,聚乙二醇为分散剂,电解液pH=10的缓冲溶液,设定初始电压12 V.电解后,微波分解,制备了由片层组成的纺锤形纳米CuO(简称片层纺锤形纳米CuO).扫描电子显微镜(SEM)、X-射线衍射仪(XRD)等表征样品的形貌、微观结构及其成分,循环伏安和计时电流法研究了该纳米CuO对H2O2氧化的催化作用.结果表明:所得产物是纯的单斜片层纺锤形CuO纳米晶,对H2O2的电化学检测具有较高的灵敏度,线性范围1.0μmol·L-1~1.0 mmol·L-1,检出限0.5μmol·L-1.

  15. Electrosorption of Os(III)-complex at single-wall carbon nanotubes immobilized on a glassy carbon electrode: Application to nanomolar detection of bromate, periodate and iodate

    Energy Technology Data Exchange (ETDEWEB)

    Salimi, Abdollah [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Research Center for Nanotechnology, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of)], E-mail: absalimi@uok.ac.ir; Kavosi, Begard [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Department of Chemistry, Arak University, P.O. Box, 38156-879 Arak (Iran, Islamic Republic of); Babaei, Ali [Department of Chemistry, Arak University, P.O. Box, 38156-879 Arak (Iran, Islamic Republic of); Hallaj, Rahman [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of)

    2008-06-16

    A simple procedure was developed to prepare a glassy carbon electrode modified with single-wall carbon nanotubes (SWCNTs) and Os(III)-complex. The glassy carbon (GC) electrode modified with CNTs was immersed into Os(III)-complex solution (direct deposition) for a short period of time (60 s). 1,4,8,12-Tetraazacyclotetradecane osmium(III) chloride, (Os(III)LCl{sub 2}).ClO{sub 4}, irreversibly and strongly adsorbed on SWCNTs immobilized on the surface of GC electrode. Cyclic voltammograms of the Os(III)-complex-incorporated-SWCNTs indicate a pair of well defined and nearly reversible redox couple with surface confined characteristic at wide pH range (1-8). The surface coverage ({gamma}) and charge transfer rate constant (k{sub s}) of the immobilized Os-complex on SWCNTs were 3.07 x 10{sup -9} mol cm{sup -2}, 5.5 ({+-}0.2) s{sup -1}, 2.94 x 10{sup -9} mol cm{sup -2}, 7.3 ({+-}0.3) s{sup -1} at buffer solution with pH 2 and 7, respectively, indicate high loading ability of SWCNTs for Os(III) complex and great facilitation of the electron transfer between electroactive redox center and carbon nanotubes immobilized on the electrode surface. Modified electrodes showed higher electrocatalytic activity toward reduction of BrO{sub 3}{sup -}, IO{sub 3}{sup -} and IO{sub 4}{sup -} in acidic solutions. The catalytic rate constants for catalytic reduction bromate, periodate and iodate were 3.79 ({+-}0.2) x 10{sup 3}, 7.32 ({+-}0.2) x 10{sup 3} and 1.75 ({+-}0.2) x 10{sup 3} M{sup -1} s {sup -1}, respectively. The hydrodynamic amperometry of rotating modified electrode at constant potential (0.3 V) was used for nanomolar detection of selected analytes. Excellent electrochemical reversibility of the redox couple, good reproducibility, high stability, low detection limit, long life time, fast amperometric response time, wide linear concentration range, technical simplicity and possibility of rapid preparation are great advantage of this sensor.

  16. Highly sensitive amperometric sensor for micromolar detection of trichloroacetic acid based on multiwalled carbon nanotubes and Fe(II)–phtalocyanine modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Kurd, Masoumeh [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Salimi, Abdollah, E-mail: absalimi@uok.ac.ir [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Research Center for Nanotechnology, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Hallaj, Rahman [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of)

    2013-04-01

    A highly sensitive electrochemical sensor for the detection of trichloroacetic acid (TCA) is developed by subsequent immobilization of phthalocyanine (Pc) and Fe(II) onto multiwalled carbon nanotubes (MWCNTs) modified glassy carbon (GC) electrode. The GC/MWCNTs/Pc/Fe(II) electrode showed a pair of well-defined and nearly reversible redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) with surface-confined characteristics. The surface coverage (Γ) and heterogeneous electron transfer rate constant (k{sub s}) of immobilized Fe(II)–Pc were calculated as 1.26 × 10{sup −10} mol cm{sup −2} and 28.13 s{sup −1}, respectively. Excellent electrocatalytic activity of the proposed GC/MWCNTs/Pc/Fe(II) system toward TCA reduction has been indicated and the three consequent irreversible peaks for electroreduction of CCl{sub 3}COOH to CH{sub 3}COOH have been clearly seen. The observed chronoamperometric currents are linearly increased with the concentration of TCA at concentration range up to 20 mM. Detection limit and sensitivity of the modified electrode were 2.0 μM and 0.10 μA μM{sup −1} cm{sup −2}, respectively. The applicability of the sensor for TCA detection in real samples was tested. The obtained results suggest that the proposed system can serve as a promising electrochemical platform for TCA detection. Highlights: ► Phthalocyanine (PC) and Fe(II) immobilized onto MWCNTs modified GC electrode. ► A pair of well-defined redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) observed. ► Modified electrode shows excellent catalytic activity to electroreduction of CCl{sub 3}COOH. ► Amperometry and cyclic voltammetry techniques were used for detection of CCl{sub 3}COOH. ► Detection limit and sensitivity were 2.0 μM and 0.10 μA μM{sup −1} cm{sup −2}, respectively.

  17. Chrono-potentiometry in molten chlorides. Application to the study of the electrochemical properties of uranium and plutonium in the LiCl-KCl eutectic; Chronopotentiometrie dans les chlorures fondus. Application a l'etude des proprietes electrochimiques de l'uranium et du plutonium dans l'eutectique LiCl-KCl

    Energy Technology Data Exchange (ETDEWEB)

    Leseur, A. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1969-05-01

    Using solutions of cadmium chloride in the eutectic LiCl-KCl, a chrono-potentiometric method has been developed with a view to its application to the study of molten solutions. Particular attention has been paid to the choice of the indicator electrodes. The method makes it possible to analyze molten solutions quantitatively and to determine diffusion coefficients and their activation energies; it yields furthermore information about the nature and the behaviour of ionic species in solution. The method has been applied to the study of solutions of uranium and plutonium chloride in the eutectic LiCl-KCl. Linear chrono-amperometry has been used for studying these solutions quantitatively, but chrono-potentiometry, of which the theory is better developed, is better suited to a quantitative study. The results obtained have made it possible to determine the diffusion coefficients of the ions Cd{sup 2+}, U{sup 3+}, U{sup 4+} and U(IV) in the presence of F{sup -} and Pu{sup 3+} ions, as well as the activation energy of the diffusion coefficients. (author) [French] La mise au point de la chronopotentiometrie comme moyen d'etude des solutions fondues a ete effectuee avec des solutions de chlorure de cadmium dans l'eutectique LiCl-KCl. Le probleme du choix des electrodes indicatrices a ete particulierement etudie. La methode permet l'analyse quantitative des solutions fondues ainsi que la determination des coefficients de diffusion et de leurs energies d'activation: elle donne en outre des renseignements sur la nature et le comportement des especes ioniques en solution. Elle a ete appliquee a l'etude des solutions des chlorures d'uranium et de plutonium dans l'eutectique LiCl-KCl. La chronoamperometrie lineaire a ete utilisee pour l'etude qualitative de ces solutions, mais la chronopotentiometrie, dont la theorie est plus complete, convient mieux pour l'etude quantitative. Les resultats obtenus ont permis de determiner les

  18. Determination of glucose at a Cu-Ni hydroxid/PPyox film modified electrode in base solution%电沉积铜镍氢氧化物/过氧化聚吡咯修饰电极对葡萄糖的测定

    Institute of Scientific and Technical Information of China (English)

    金君; 于浩; 王飞; 宋诗稳; 刘珍叶; 齐广才

    2011-01-01

    A Cu-Ni hydroxid / overoxidized polypynole composite film modified electrode was fabricated by using cyclic voltammetry and characterized by electrochemistry and XRD techniques. The electrochemical behavior of glucose on the modified electrode was investigated by cyclic voltammetry and amperometry. The results showed that the resulting modified electrode exhibited high electrocatalytic activity for the oxidation of glucose. Based on this, an amperometric techniques for the determination of glucose was established. Under the optimal conditions, the oxidation peak current has linear relationship with concentration of glucose over the ranges of 5. 0 × 10-7 to 1.1 × 10~3 mol/L (r = 0.9992) and 1.1 × 10 -3 mol/L to 5. 8 × 10 3 mol/L(r = 0.9977), with sensitivities of 1069.3 μA/mmol/L ? cm-2and 505.7 μA/mmol/L ? cm-2, respectively. The detection limit (3sb) was 2.0× 10-7 mol/L. The RSD (n = 10) for the determination of 1.0 × 10-4 mol/L glucose was 3. 2 % and the recoveries were 96. 4 % ~ 100. 8%. The proposed method was applied to the determination of glucose in the serum.%采用循环伏安法制备了铜镍氢氧化物/过氧化聚吡咯复合膜修饰电极( Cu-Ni (OH) 2/PPyox/CCE),并对其进行了表征.研究了葡萄糖在该修饰电极上的电化学行为,结果表明,该修饰电极对葡萄糖的氧化有良好的电催化活性.安培法检测葡萄糖的线性范围为5.0×10-7~1.1×10-3 mol/L(r=0.9992)和1.1×10-3 mol/L~5.8×10-3 mol/L(r=0.9977),检出限(3sb)为2.0×10-7mol/L,加标回收率为96.4% ~ 100.8%.方法已用于血清中葡萄糖含量的测定.

  19. 内酯型荧光黄与β-环糊精的包合作用研究%Study of inclusion complex formation between the lactonic structure of fluorescein and β-cyclodextrin

    Institute of Scientific and Technical Information of China (English)

    刘奇; 魏静娟; 孟芹红; 王爱军

    2011-01-01

    A Cu-Ni hydroxid / overoxidized polypynole composite film modified electrode was fabricated by using cyclic voltammetry and characterized by electrochemistry and XRD techniques. The electrochemical behavior of glucose on the modified electrode was investigated by cyclic voltammetry and amperometry. The results showed that the resulting modified electrode exhibited high electrocatalytic activity for the oxidation of glucose. Based on this, an amperometric techniques for the determination of glucose was established. Under the optimal conditions, the oxidation peak current has linear relationship with concentration of glucose over the ranges of 5. 0 ×10-7 to 1.1 × 10~3 mol/L (r = 0.9992) and 1.1 × 10 3 mol/L to 5. 8 x× 10 3 mol/L(r = 0.9977), with sensitivities of 1069.3 μA/mmol/L · cm-2 and 505.7 μA/mmol/L · cm-2, respectively. The detection limit (3sb) was 2.0 × 10-7 mol/L. The RSD (n = 10) for the determination of 1.0 × 10-4 mol/L glucose was 3. 2 % and the recoveries were 96. 4 % ~ 100. 8%. The proposed method was applied to the determination of glucose in the serum.%在pH 4的缓冲溶液中,内酯型荧光黄与β-环糊精形成1∶1包合物,其紫外-可见吸光变和荧光强度均下降.考察了pH,离子强度及有机溶剂对包合物稳定性的影响;采用热力学法分析了温度和包合常数的关系,计算了包合过程的焓变,熵变及自由能变化;并通过分子模拟和红外光谱法对包合物的包合形式进行理论探讨和研究.

  20. Phosphomimetic mutation of cysteine string protein-α increases the rate of regulated exocytosis by modulating fusion pore dynamics in PC12 cells.

    Directory of Open Access Journals (Sweden)

    Ning Chiang

    Full Text Available BACKGROUND: Cysteine string protein-α (CSPα is a chaperone to ensure protein folding. Loss of CSPα function associates with many neurological diseases. However, its function in modulating regulated exocytosis remains elusive. Although cspα-knockouts exhibit impaired synaptic transmission, overexpression of CSPα in neuroendocrine cells inhibits secretion. These seemingly conflicting results lead to a hypothesis that CSPα may undergo a modification that switches its function in regulating neurotransmitter and hormone secretion. Previous studies implied that CSPα undergoes phosphorylation at Ser10 that may influence exocytosis by altering fusion pore dynamics. However, direct evidence is missing up to date. METHODOLOGY/PRINCIPAL FINDINGS: Using amperometry, we investigated how phosphorylation at Ser10 of CSPα (CSPα-Ser10 modulates regulated exocytosis and if this modulation involves regulating a specific kinetic step of fusion pore dynamics. The real-time exocytosis of single vesicles was detected in PC12 cells overexpressing control vector, wild-type CSPα (WT, the CSPα phosphodeficient mutant (S10A, or the CSPα phosphomimetic mutants (S10D and S10E. The shapes of amperometric signals were used to distinguish the full-fusion events (i.e., prespike feet followed by spikes and the kiss-and-run events (i.e., square-shaped flickers. We found that the secretion rate was significantly increased in cells overexpressing S10D or S10E compared to WT or S10A. Further analysis showed that overexpression of S10D or S10E prolonged fusion pore lifetime compared to WT or S10A. The fraction of kiss-and-run events was significantly lower but the frequency of full-fusion events was higher in cells overexpressing S10D or S10E compared to WT or S10A. Advanced kinetic analysis suggests that overexpression of S10D or S10E may stabilize open fusion pores mainly by inhibiting them from closing. CONCLUSIONS/SIGNIFICANCE: CSPα may modulate fusion pore dynamics

  1. Fisiologi dan Gangguan Keseimbangan Natrium, Kalium dan Klorida serta Pemeriksaan Laboratorium

    Directory of Open Access Journals (Sweden)

    Rismawati Yaswir

    2012-09-01

    +, potassium (K+, chloride(Cl-, and bicarbonate (HCO3-. Fourth Inspection of the major electrolyte in clinic known as "electrolyteprofile”.Sodium is cation many in extracell fluid, potassium is cation many in intrasel fluid, and chloride is anionmany in extracell fluid. Amount of natrium, chloride and potassium in body are balance which enter especially fromdigest and excretion especially through kidney.Balance disorders of natrium, chloride and potassium in the form ofhipo- and hyper-. Hipo- happened when the electrolyte concentration in body go down more than somemiliekuivalen under normal values and hyper- when the concentration of mounting above normal.Laboratoryfindings to determine concentration of natrium, chloride and potassium are with ion selective electrode (ISEmethod, flame emission spectrophotometry (FES, atomic absorption spectrophotometry, spektrofotometrypursuant to enzyme activation, determine concentration of chloride with titration method of merkurimeter, and withtitration method of colorimetry-amperometry.Keywords: Electrolyte, balance, balance disorders

  2. Analysis of Arterial Blood Gas Report in Chronic Kidney Diseases – Comparison between Bedside and Multistep Systematic Method

    Science.gov (United States)

    Dhat, Vaishali; Tilak, Mona A; Roy, Indranath

    2016-01-01

    Introduction Acid Base Disorders (ABDs) are commonly encountered in critically ill Chronic Kidney Disease (CKD) patients. Timely and correct analysis of Arterial Blood Gases (ABG) is critical for the diagnosis, treatment and prediction of outcome of the patients. Aim The aim was to explore type and prevalence of ABDs in 31 critically ill CKD patients from a tertiary care hospital in Maharashtra, to compare two methods of analysis- bedside and systematic approaches and to clinically correlate the nature of ABDs in these patients. Materials and Methods The initial ABG reports of 31 consecutive CKD patients were analysed by two methods. Medica Easy stat analyser was the equipment for analysis with Principle of potentiometry and ion selective electrode for pH and pCO2 and amperometry for pO2. Serum albumin was also measured by Bromocresol green dye binding method using liquixx albumin kit in Erba XL 300 autoanalyser. Statistical Analysis Chi-square test was used for statistical analysis using Epi Info version 3.5.4 and SPSS 14.0 softwares. Results The systematic method showed a significantly higher prevalence of mixed disorders (50%) compared to bedside method (12.9%). Most prevalent disorder by bedside method was metabolic acidosis in 15 cases (48.39%). By the systematic method, 3 reports were invalid. As a single category, most prevalent type was both simple respiratory alkalosis and mixed metabolic acidosis with respiratory alkalosis- 6 of 31 cases in each type (19.36% each). As a whole, metabolic acidosis (including both High Anion Gap Metabolic Acidosis or HAGMA and Non Anion Gap Metabolic Acidosis or NAGMA with 4 in each type) was most prevalent- 8 of 31(25.8%). Conclusion Systematic approach was more effective in diagnosing mixed acid base disorders. By systematic method the findings of analysis in most cases could be correlated with the clinical condition and provisional diagnosis. Thus interpretation of ABDs by using stepwise approach could be useful to the

  3. 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.

  4. 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

  5. 多孔阳极氧化铝的化学修饰及其应用于过氧化氢的测定%Chemical Modification of Porous Anodic Alumina and Application in Detection of Hydrogen Peroxide

    Institute of Scientific and Technical Information of China (English)

    徐国荣; 唐安平

    2011-01-01

    A new hydrogen peroxide electrochemical biosensor was fabricated through adsorbed cytochrome C in porous anodic alumina chemically modified. The barrier layer at the bottom of the porous anodic alumina was erased by chemical and electrochemical erosion. The Au nano particles were deposited in porous anodic alumina by two-step electroless deposition, and then the cytochrome C was immobilization on Nano Au bed in solution including L-cyste-ine through self-assembled technology. Then a new hydrogen peroxide biosensor was fabricated. The electrochemical and electro catalytic behavior of the cytochrome C electrode was characterized by cyclic voltammetry and chrono-amperometry. The cytochrome C electrode showed a pair of stable and well-defined peaks at about -50 mV and -190 mV at 80 mV/s in pH 7.0 PBS and displayed excellent electro catalytic responses to the reduction of hydrogen peroxide with linear relationship over a concentration range from 1.5xl0-5 mol/L to 4. 8xl0-4 mol/L,and a detection limit of 3.5 x10-6 mol/L( S/N = 3). The results of this study reveal porous anodic alumina chemically modified could be used for the design of biosensors with good operational lifetimes.%多孔阳极氧化铝经化学修饰后吸附细胞色素C,制备了过氧化氢生物传感器电极。多孔阳极氧化铝通过电化学和化学腐蚀阻挡层后,用两步无电沉积方法制备了纳米金修饰的多孔阳极氧化铝电极,再在含有L-半胱氨酸的细胞色素C的溶液中通过吸附制备细胞色素C电极。用循环伏安法和计时电流法测试细胞色素C电极的电化学性能及催化对过氧化氢的还原。结果表明,包覆的细胞色素C电极显示较好的稳定性,在扫描速度为80 mV/s时于-50 mV、-190mV附近出现一对稳定的氧化还原峰。该电极对过氧化氢具有良好的电催化还原性能,在1.5×10-5mol/L~4.8×10-4 mol/L浓度范围内,电流与浓度呈良好的线性关系。多孔阳极氧化铝

  6. Study on the direct electrochemistry of Myoglobin based on Ag2 S-MWNTs nanocomposites%基于Ag2 S-MWNTs的肌红蛋白直接电化学研究

    Institute of Scientific and Technical Information of China (English)

    史智锋; 贺慧; 马李思思

    2014-01-01

    Ag2 S-MWNTs nanoconposites was prepared and then a Mb-Ag2 S-MWNTs-CHIT/GCE was fabricated. Based on the fabri-cated Mb-Ag2 S-MWNTs-CHIT/GCE,the direct electrochemistry and electrocatalytic properties of the immobilized Mb were investi-gated. Scanning electron microscopic and Transmission electron microscopic were used to characterize the morphology of the Ag2 S-MWNTs. Cyclic voltammetry and amperometry were used for studying the electrochemical behaviors of Mb. Uniform and stable Ag2 S was growing at the MWNTs surface,and the fabricated electrode showed a well-defined and quasi-reversible redox peaks and good electrocatalytic ability for hydrogen peroxide( H2 O2 ) reduction. The resulting modified electrode could detect H2 O2 in a linear range of 1. 0 × 10-6 ~2. 5 × 10-4 mol·L-1 and the detection limit was 3 × 10-7 mol·L-1 at a signal-to-noise ratio of 3. Ag2 S-MWNTs in-creased the direct electron transfer rate dramatically and the modified electrode can provide a good platform for the investigation of the third generation biosensors.%制备了硫化银-多壁碳纳米管( Ag2 S-MWNTs)纳米复合材料,构置了Mb-Ag2 S-MWNTs-CHIT/GCE,并研究了肌红蛋白( Mb)在该修饰电极上的直接电化学和电催化行为。采用扫描电镜和透射电镜表征了Ag2 S-MWNTs的形貌,利用循环伏安法对Mb的电化学行为进行研究。 Ag2 S能够均一、稳定的在MWNTs表面生长,所构置的修饰电极在PBS中出现一对峰形良好的、准可逆的氧化还原峰,并对过氧化氢( H2 O2)表现出良好的电催化作用,测定H2O2的线性范围为1.0×10-6~2.5×10-4 mol·L-1,检出限为3×10-7 mol·L-1(S/N=3)。 Ag2 S-MWNTs纳米复合材料能显著提高氧化还原蛋白质(酶)的直接电子传递速率,所构置的修饰电极可为制备基于蛋白质(酶)的第三代电化学生物传感器提供一良好的研究平台。

  7. Source apportionment of elevated BaP concentrations in PM10 aerosols in an alpine valley in Austria

    Science.gov (United States)

    Bauer, Heidi; Puxbaum, Hans; Jankowski, Nicole; Sampaio Cordeiro Wagner, Lylian

    2010-05-01

    INTRODUCTION: In a village situated at 1215 m a.s.l. in a natural preserve in an Austrian alpine valley elevated BaP concentrations have been measured in the last years. A highly frequented highway leading from Italy to Germany passes near the village. Monthly means of particulate BaP concentrations show a clear seasonal trend with values below 1 ng/m³ during the warmer months and with concentrations up to 9 ng/m³ in the cold season. Annual averages in the years 2000 - 2005 ranged between 1.4 and 2.8 ng/m³ - much higher than the EU target value of 1 ng/m³. We used a macrotracer model developed at the Vienna University of Technology to determine the contributions of the sources for BaP emissions, which were mainly space heating with wood and traffic from the highway. EXPERIMENTAL: The macrotracer concept is a nine component model to derive source contribution and explains 80-100% of PM10 aerosols in Austria. The amount of traffic exhaust is derived by using EC as tracer, whereas EC produced by wood burning is subtracted, the amount of wood smoke is derived by the anhydro-sugar levoglucosan and the ratio between the anhydro-sugars levoglucosan and mannosan. For the source apportionment of BaP the applied factors reflect on the one hand the composition of the automotive fleet in Austria and on the other hand the composition of the fire wood in the region. Filter samples collected with a high volume sampler in winter were analyzed for PM10 aerosol mass, total, organic, elemental and carbonate carbon, HULIS, anhydro-sugars, polyols and ions (major ions and organic acids) and PAHs. In the same way emission samples taken at a motor test stand and at a test stand for wood combustion were analyzed (Schmidl et al. 2008). The saccharides were determined using high pH anion exchange and pulsed amperometry (HPAE-PAD). Details of the analytical method are given in Iinuma et al., 2009. Elemental and organic carbon were determined with a thermal-optical instrument (Sunset lab

  8. Development of a nanowire based titanium needle probe sensor for glucose monitoring

    Science.gov (United States)

    Deshpande, Devesh C.

    glucose monitoring. The working electrode of the sensor comprised of vertically aligned, free standing Au nanowires to utilize the advantages of nanostructures. The sensor was fabricated on biocompatible titanium substrate using Micro/Nano fabrication processes such as Plasma Enhanced Chemical Vapor Deposition (PECVD), Electron Beam Evaporation, Lithography, aligned nanowire growth and wet and plasma etching. Arrays of free-standing nanowires were grown at room temperature and pressure using a novel template based growth process. After fabrication of the sensor, immobilization of an enzyme was carried out on the sensing electrode to ensure selectivity of the sensor to glucose. This was achieved by using self-assembled thiol monolayers and entrapment in a conducting polymer matrix. Glucose oxidase was used for this purpose, which catalyzed the conversion of glucose to gluconic acid, producing hydrogen peroxide in the process. Amperometry was used for glucose detection, in which a constant voltage was applied to the sensor. This potential oxidized the hydrogen peroxide and produced changes in the current which were correlated to the glucose concentration. This dissertation will address the importance of continuous glucose monitoring, current technology and problems faced, the design and fabrication of the sensor and electrochemical sensing to detect glucose levels in solution. Finally, the problems encountered during the process will be discussed and the future work will be detailed.

  9. Corrosion kinetics of alloy Ni-22Cr-13Mo-3W as structural material in high level nuclear waste containers

    International Nuclear Information System (INIS)

    Alloy Ni-22Cr-13Mo-3W (also known as C-22) is one of the candidates to fabricate high level nuclear waste containers. These containers are designed to maintain isolation of the waste for a minimum of 10,000 years. In this period, the material must be resistant to corrosion. If the containers were in contact with water, it is assumed that alloy C-22 may undergo three different corrosion mechanisms: general corrosion, localized corrosion and stress corrosion cracking. This thesis discusses only the first two types of degradation. Electrochemical techniques such as amperometry, potentiometry, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) and non-electrochemical techniques such as microscopic observation, X-ray fluorescence (XRF) and X-ray photoelectron spectroscopy (XPS) were applied to study the corrosion behavior of alloy C-22 in 1 M NaCl, 25 C degrees saturated NaF (approximately 1 M) and 0,5 M NaCl + 0,5 M NaF solutions. Effects of temperature, pH and alloy thermal aging were analyzed. The corrosion rates obtained at 90 C degrees were low ranging from 0.04 μm/year to 0.48 μm /year. They increased with temperature and decreased with solution pH. Most of the impedance measurements showed a simply capacitive behavior. A second high-frequency time constant was detected in some cases. It was attributed to the formation of a nickel oxide and/or hydroxide at potentials near the reversible potential for this reaction. The active/passive transition detected in some potentiodynamic polarization curves was attributed to the same process. The corrosion potential showed an important increase after 24 hours of immersion. This increase in the corrosion potential was associated with an improvement of the passive film. The corrosion potential was always lower than the re-passivation potential for the corresponding media. The trans passive behavior of alloy C-22 was mainly influenced by temperature and solution chemistry. A clear trans passive peak

  10. Electrodeposition of Ni/LaNiO3 Composite Electrode and Its Properties Toward Oxygen Evolution Reaction in Alkaline Media%电沉积Ni/LaNiO3复合电极及其在碱性介质中的析氧性能

    Institute of Scientific and Technical Information of China (English)

    王森林; 鲍晋珍

    2012-01-01

    A perovskite composite oxide LaNiO3 was obtained by sol-gel method. Then,a Ni/LaNiO3 composite coating was prepared by composite electro-deposition technique in watt solution plating Ni by mixing with LaNiO3 powders. The effect of the plating bath pH and the cathode current density on the composition of the composite coating was investigated,respectively. The surface morphology,the LaNiO3 content and the structure of a Ni/LaNiO3 composite coating were characterized by scanning electron microscopy (SEM),energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). As a result,the LaNiO3 content of the Ni/LaNiO3 composite coating had the highest value ( about 60% ) at the best plating conditions ,which were the bath pH of 5. 8 and the cathodic current density of 90 mA·cm-2. In a 5 mol·L-1 KOH solution,the electrocatalytic properties toward the oxygen evolution reaction ( OER) of the Ni/LaNiO3 composite electrode was studied using cyclic voltammetry,electrochemical steady-state polarization,chrono-amperometry and electrochemical impendence spec-troscopy ( EIS ) . Compared with a nickel electrode,the electrocatalytic properties toward OER of the Ni/ LaNiO3 composite electrode improved greatly,and the apparent activation energy was reduced by 2/3,its specific surface was 55 times larger than that of a nickel electrode.%采用溶胶-凝胶法制备了钙钛矿型复合氧化物LaNiO3,然后将其加入瓦特镀镍液中进行复合电沉积,研究了镀液pH值和阴极电流密度对Ni/LaNiO3复合镀层组成的影响.运用扫描电镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)等对复合镀层进行表征,结果表明:最佳电沉积工艺条件是镀液pH=5.8和阴极电流密度jk=90 mA·cm-2,所得的Ni/LaNiO3复合镀层中LaNiO3的质量含量约为60%.用循环伏安、稳态极化、恒电位阶跃、电化学阻抗谱等电化学技术评价了Ni/LaNiO3复合电极的析氧性能.结果表明:在5mol·L-1的KOH溶液中,Ni/LaNiO3复合电极的

  11. Immunogenicity and ecotoxicity of engineered nanoparticles

    Science.gov (United States)

    Maurer-Jones, Melissa Ann

    The growing use of nanoscale materials in commercially available products and therapeutics has created an urgent need to determine the toxicity of these materials so that they may be designed and employed safely. As nanoparticles have unique physical and chemical properties, the challenges in determining their physiological and environmental impact have been numerous. It is, therefore, the goal of my thesis work to employ sensitive analytical tools to fundamentally understand the how nanoparticles interact with immunologically and ecologically relevant models. My project approaches nanotoxicity studies starting with a relevant model system exposed to well-characterized nanoparticles to (1) determine if cells/organisms survive exposure using traditional toxicological assays and, if the majority survives exposure, (2) use sensitive analytical tools to determine if there are changes to critical cell/organism function. If perturbation of function is detected, (3) the mechanism or cause of changes in cell function should be determined, including assessment of nanoparticle uptake and localization. Once a mechanism of interaction is determined, this process could begin again with a modified particle that may address the toxic response. Chapter Two describes the impact of metal oxide (TiO2 and SiO2) nanoparticles on mast cells, critical immune system cells, and utilizes the sensitive technique of carbon-fiber microelectrode amperometry (CFMA) to monitor changes in the important mast cell function of exocytosis. Chapter Three expands upon Chapter Two and examines in more detail the mechanism by which TiO2 nanoparticles impact exocytotic cell function, completing the process nanotoxicity described above. From these studies, it was determined that, while nanoparticles do not decrease the viability of mast cells, there are significant changes to exocytosis upon nanoparticle exposure, and in the case of TiO2, these changes in exocytosis are correlated to nanoparticle