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Sample records for enhanced electrochemical detection

  1. Enhanced electrochemical detection of quercetin by Natural Deep Eutectic Solvents.

    PubMed

    Gomez, Federico José Vicente; Espino, Magdalena; de Los Angeles Fernandez, María; Raba, Julio; Silva, María Fernanda

    2016-09-14

    New trends in analytical chemistry encourage the development of smart techniques and methods aligned with Green Chemistry. In this sense, Natural Deep Eutectic Solvents represents an excellent opportunity as a new generation of green solvents. In this work a new application for them has been proposed and demonstrated. These solvents were synthesized by combinations of inexpensive and natural components like, Glucose, Fructose, Citric acid and Lactic acid. The different natural solvents were easily prepared and added to buffer solution in different concentrations, allowing the enhancement of electrochemical detection of an important representative antioxidant like quercetin (QR) with improved signal up to 380%. QR is a ubiquitous flavonoid widespread in plants and food of plant origin. The proposed method using phosphate buffer with a eutectic mixture of Citric acid, Glucose and water in combination with carbon screen printed electrodes exhibited a good analytical performance. Detection and quantification limits were of 7.97 and 26.3 nM respectively; and repeatability with %RSDs of 1.41 and 7.49 for peak potential and intensity respectively. In addition, it has proved to be faster, greener and cheaper than other sensors and chromatographic methods available with the additional advantage of being completely portable. Furthermore, the obtained results demonstrated that the proposed method is able for the determination of QR in complex food samples.

  2. Enhanced electrochemical detection of quercetin by Natural Deep Eutectic Solvents.

    PubMed

    Gomez, Federico José Vicente; Espino, Magdalena; de Los Angeles Fernandez, María; Raba, Julio; Silva, María Fernanda

    2016-09-14

    New trends in analytical chemistry encourage the development of smart techniques and methods aligned with Green Chemistry. In this sense, Natural Deep Eutectic Solvents represents an excellent opportunity as a new generation of green solvents. In this work a new application for them has been proposed and demonstrated. These solvents were synthesized by combinations of inexpensive and natural components like, Glucose, Fructose, Citric acid and Lactic acid. The different natural solvents were easily prepared and added to buffer solution in different concentrations, allowing the enhancement of electrochemical detection of an important representative antioxidant like quercetin (QR) with improved signal up to 380%. QR is a ubiquitous flavonoid widespread in plants and food of plant origin. The proposed method using phosphate buffer with a eutectic mixture of Citric acid, Glucose and water in combination with carbon screen printed electrodes exhibited a good analytical performance. Detection and quantification limits were of 7.97 and 26.3 nM respectively; and repeatability with %RSDs of 1.41 and 7.49 for peak potential and intensity respectively. In addition, it has proved to be faster, greener and cheaper than other sensors and chromatographic methods available with the additional advantage of being completely portable. Furthermore, the obtained results demonstrated that the proposed method is able for the determination of QR in complex food samples. PMID:27566343

  3. DNA Diagnostics: Nanotechnology-enhanced Electrochemical Detection of Nucleic Acids

    PubMed Central

    Wei, Fang; Lillehoj, Peter B.; Ho, Chih-Ming

    2010-01-01

    The detection of mismatched base pairs in DNA plays a crucial role in the diagnosis of genetic-related diseases and conditions, especially for early stage treatment. Among the various biosensors that have been employed for DNA detection, electrochemical sensors show great promise since they are capable of precise DNA recognition and efficient signal transduction. Advancements in micro- and nanotechnologies, specifically fabrication techniques and new nanomaterials, have enabled for the development of highly sensitive, highly specific sensors making them attractive for the detection of small sequence variations. Furthermore, the integration of sensors with sample preparation and fluidic processes enables for rapid, multiplexed DNA detection for point-of-care (POC) clinical diagnostics. PMID:20075759

  4. Electrochemical detection of amaranth in food based on the enhancement effect of carbon nanotube film.

    PubMed

    Wang, Peng; Hu, Xiaozhong; Cheng, Qin; Zhao, Xiaoya; Fu, Xiaofang; Wu, Kangbing

    2010-12-01

    Amaranth is widely added to food and can cause many adverse health effects when it is excessively consumed. Therefore, the monitoring of amaranth is quite important. Herein, an electrochemical sensor for the sensitive and rapid detection of amaranth was reported using multiwall carbon nanotube (MWNT) as the sensing film. Due to the large surface area and high accumulation efficiency, the MWNT sensor showed a strong enhancement effect on the oxidation of amaranth, and greatly increased the current signal. The detection conditions such as pH value, amount of MWNT, accumulation potential and time were optimized. The linear range is from 40 nM to 0.8 μM, and the limit of detection is 35 nM. Finally, the new sensor was successfully employed to detect amaranth in soft drinks, and the results were tested by high-performance liquid chromatography.

  5. Ultrasensitive electrochemical detection of nucleic acids by template enhanced hybridization followed with rolling circle amplification.

    PubMed

    Ji, Hanxu; Yan, Feng; Lei, Jianping; Ju, Huangxian

    2012-08-21

    An ultrasensitive protocol for electrochemical detection of DNA is designed with quantum dots (QDs) as a signal tag by combining the template enhanced hybridization process (TEHP) and rolling circle amplification (RCA). Upon the recognition of the molecular beacon (MB) to target DNA, the MB hybridizes with assistants and target DNA to form a ternary ''Y-junction''. The target DNA can be dissociated from the structure under the reaction of nicking endonuclease to initiate the next hybridization process. The template enhanced MB fragments further act as the primers of the RCA reaction to produce thousands of repeated oligonucleotide sequences, which can bind with oligonucleotide functionalized QDs. The attached signal tags can be easily read out by square-wave voltammetry after dissolving with acid. Because of the cascade signal amplification and the specific TEHP and RCA reaction, this newly designed protocol provides an ultrasensitive electrochemical detection of DNA down to the attomolar level (11 aM) with a linear range of 6 orders of magnitude (from 1 × 10(-17) to 1 × 10(-11) M) and can discriminate mismatched DNA from perfect matched target DNA with high selectivity. The high sensitivity and specificity make this method a great potential for early diagnosis in gene-related diseases.

  6. Nanoprobe-Enhanced, Split Aptamer-Based Electrochemical Sandwich Assay for Ultrasensitive Detection of Small Molecules.

    PubMed

    Zhao, Tao; Liu, Ran; Ding, Xiaofan; Zhao, Juncai; Yu, Haixiang; Wang, Lei; Xu, Qing; Wang, Xuan; Lou, Xinhui; He, Miao; Xiao, Yi

    2015-08-01

    It is quite challenging to improve the binding affinity of antismall molecule aptamers. We report that the binding affinity of anticocaine split aptamer pairs improved by up to 66-fold by gold nanoparticles (AuNP)-attached aptamers due to the substantially increased local concentration of aptamers and multiple and simultaneous ligand interactions. The significantly improved binding affinity enables the detection of small molecule targets with unprecedented sensitivity, as demonstrated in nanoprobe-enhanced split aptamer-based electrochemical sandwich assays (NE-SAESA). NE-SAESA replaces the traditional molecular reporter probe with AuNPs conjugated to multiple reporter probes. The increased binding affinity allowed us to use 1,000-fold lower reporter probe concentrations relative to those employed in SAESA. We show that the near-elimination of background in NE-SAESA effectively improves assay sensitivity by ∼1,000-100,000-fold for ATP and cocaine detection, relative to equivalent SAESA. With the ongoing development of new strategies for the selection of aptamers, we anticipate that our sensor platform should offer a generalizable approach for the high-sensitivity detection of diverse targets. More importantly, we believe that NE-SAESA represents a novel strategy to improve the binding affinity between a small molecule and its aptamer and potentially can be extended to other detection platforms.

  7. Sheath-Flow Microfluidic Approach for Combined Surface Enhanced Raman Scattering and Electrochemical Detection

    PubMed Central

    2015-01-01

    The combination of hydrodynamic focusing with embedded capillaries in a microfluidic device is shown to enable both surface enhanced Raman scattering (SERS) and electrochemical characterization of analytes at nanomolar concentrations in flow. The approach utilizes a versatile polystyrene device that contains an encapsulated microelectrode and fluidic tubing, which is shown to enable straightforward hydrodynamic focusing onto the electrode surface to improve detection. A polydimethyslsiloxane (PDMS) microchannel positioned over both the embedded tubing and SERS active electrode (aligned ∼200 μm from each other) generates a sheath flow that confines the analyte molecules eluting from the embedded tubing over the SERS electrode, increasing the interaction between the Riboflavin (vitamin B2) and the SERS active electrode. The microfluidic device was characterized using finite element simulations, amperometry, and Raman experiments. This device shows a SERS and amperometric detection limit near 1 and 100 nM, respectively. This combination of SERS and amperometry in a single device provides an improved method to identify and quantify electroactive analytes over either technique independently. PMID:25815795

  8. Micro and nanoscale electrochemical systems for reagent generation, coupled electrokinetic transport and enhanced detection

    NASA Astrophysics Data System (ADS)

    Contento, Nicholas M.

    Chemical analysis is being performed in devices operated at ever decreasing length scales in order to harness the fundamental benefits of micro and nanoscale phenomena while minimizing operating footprint and sample size. The advantages of moving traditional sample or chemical processing steps (e.g. separation, detection, and reaction) into micro- and nanofluidic devices have been demonstrated, and they arise from the relatively rapid rates of heat and mass transport at small length scales. The use of electrochemical methods in micro/nanoscale systems to control and improve these processes holds great promise. Unfortunately, much is still not understood about the coupling of multiple electrode driven processes in a confined environment nor about the fundamental changes in device performance that occur as geometries approach the nanoscale regime. At the nanoscale a significant fraction of the sample volume is in close contact with the device surface, i.e. most of the sample is contained within electronic or diffusion layers associated with surface charge or surface reactions, respectively. The work presented in this thesis aims to understand some fundamental different behaviors observed in micro/nanofluidic structures, particularly those containing one or more embedded, metallic electrode structures. First, a quantitative method is devised to describe the impact of electric fields on electrochemistry in multi-electrode micro/nanofluidic systems. Next the chemical manipulation of small volumes (≤ 10-13 L) in micro/nanofluidic structures is explored by creating regions of high pH and high dissolved gas (H 2) concentration through the electrolysis of H2O. Massively parallel arrays of nanochannel electrodes, or embedded annular nanoband electrodes (EANEs), are then studied with a focus on achieving enhanced signals due to coupled electrokinetic and electrochemical effects. In EANE devices, electroosmotic flow results from the electric field generated between the

  9. Target-specific capture enhances sensitivity of electrochemical detection of bacterial pathogens.

    PubMed

    Patel, Mayank; Gonzalez, Rodrigo; Halford, Colin; Lewinski, Michael A; Landaw, Elliot M; Churchill, Bernard M; Haake, David A

    2011-12-01

    We report the concentration and purification of bacterial 16S rRNA by the use of a biotinylated DNA target-specific capture (TSC) probe. For both cultivated bacterial and urine specimens from urinary tract infection patients, TSC resulted in a 5- to 8-fold improvement in the sensitivity of bacterial detection in a 16S rRNA electrochemical sensor assay.

  10. A Proof of Concept: Detection of Avian Influenza H5 Gene by a Graphene-Enhanced Electrochemical Genosensor.

    PubMed

    Low, Sze Shin; Chia, Joanna Su Yuin; Tan, Michelle T T; Loh, Hwei-San; Khiew, Poi Sim; Singh, Ajit; Chiu, Wee Siong

    2016-03-01

    The highly pathogenic avian influenza (HPAI) virus subtype H5N1 has been found to be the most virulent and deadliest virus strain, with capability of interspecies transmission to human infection. Most human HPAI H5N1 cases were diagnosed late in their illnesses for medical care, resulting in severe complications that led to death. In this study, a novel graphene-enhanced electrochemical DNA biosensor had been fabricated for the detection of polymerase chain reaction (PCR) amplicon derived from the haemagglutinin (H5) gene of the HPAI. The graphene-enhanced DNA biosensor showed excellent linear correlation between PCR amplicon concentration and amperometric signal with a correlation coefficient, r2 of 0.9987. The amperometric response of the proposed biosensor was compared with conventional gel electrophoresis while the feasibility of the proposed sandwich sensing platform was verified via dot blot assay. The results obtained indicate that the electrochemical DNA biosensing assay is significantly more sensitive (P < 0.05) and time efficient. This work serves as a proof of concept in hopes for further development of the graphene enhanced electrochemical DNA biosensor into a portable, on-site screening platform for point-of-care detection of various pathogens. PMID:27455653

  11. Rapid and highly sensitive detection of Enterovirus 71 by using nanogold-enhanced electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Hsing-Yuan; Tseng, Shing-Hua; Cheng, Tsai-Mu; Chu, Hsueh-Liang; Lu, Yu-Ning; Wang, Fang-Yu; Tsai, Li-Yun; Shieh, Juo-Yu; Yang, Jyh-Yuan; Juan, Chien-Chang; Tu, Lung-Chen; Chang, Chia-Ching

    2013-07-01

    Enterovirus 71 (EV71) infection is an emerging infectious disease causing neurological complications and/or death within two to three days after the development of fever and rash. A low viral titre in clinical specimens makes the detection of EV71 difficult. Conventional approaches for detecting EV71 are time consuming, poorly sensitive, or complicated, and cannot be used effectively for clinical diagnosis. Furthermore, EV71 and Coxsackie virus A16 (CA16) may cross react in conventional assays. Therefore, a rapid, highly sensitive, specific, and user-friendly test is needed. We developed an EV71-specific nanogold-modified working electrode for electrochemical impedance spectroscopy in the detection of EV71. Our results show that EV71 can be distinguished from CA16, Herpes simplex virus, and lysozyme, with the modified nanogold electrode being able to detect EV71 in concentrations as low as 1 copy number/50 μl reaction volume, and the duration between sample preparation and detection being 11 min. This detection platform may have the potential for use in point-of-care diagnostics.

  12. Single domain antibody coated gold nanoparticles as enhancer for Clostridium difficile toxin detection by electrochemical impedance immunosensors

    PubMed Central

    Zhu, Zanzan; Shi, Lianfa; Feng, Hanping; Zhou, H. Susan

    2016-01-01

    This work presents a sandwich-type electrochemical impedance immunosensor for detecting Clostridium difficile toxin A (TcdA) and toxin B (TcdB). Single domain antibody conjugated gold nanoparticles were applied to amplify the detection signal. Gold nanoparticles (Au NPs) were characterized by transmission electron microscopy and UV–vis spectra. The electron transfer resistance (Ret) of the working electrode surface was used as a parameter in the measurement of the biosensor. With the increase of the concentration of toxins from 1 pg/mL to 100 pg/mL, a linear relationship was observed between the relative electron transfer resistance and toxin concentration. In addition, the detection signal was enhanced due to the amplification effect. The limit of detection for TcdA and TcdB was found to be 0.61 pg/mL and 0.60 pg/mL respectively at a signal-to-noise ratio of 3 (S/N = 3). This method is simple, fast and ultrasensitive, thus possesses a great potential for clinical applications in the future. PMID:25460611

  13. Ultrasensitive electrochemical detection of DNA hybridization using Au/Fe3O4 magnetic composites combined with silver enhancement.

    PubMed

    Bai, Yu-Hui; Li, Jin-Yi; Xu, Jing-Juan; Chen, Hong-Yuan

    2010-07-01

    A novel method is described for the highly effective amplifying electrochemical response of DNA based on oligonucleotides functionalized with Au/Fe(3)O(4) nanocomposites by the aid of silver (Ag) enhancement. Via electrostatic layer-by-layer (LBL) assembly, the prepared Fe(3)O(4) nanoparticles form nano-clusters coated with a bilayer composed of polystyrene sulfonate sodium salt (PSS) and poly(diallyldimethylammonium chloride) (PDDA), which are in favor of adsorbing lots of gold nanoparticles (AuNPs) on the surface. The application of magnetic Fe(3)O(4) made the procedures much more simple, convenient and feasible. The resulting composites were then used as labels via the Au-S bond for the DNA hybridization, followed by catalytic deposition of silver on the gold tags. Such an assay is then combined with a sensitive anodic stripping voltammetry (ASV) measurement of multiple silver nanoparticle tracers. A 27-mer sequence DNA target is detected at a glassy carbon (GC) electrode with a detection limit down to ca. 100 aM, which is 800 times lower than that obtained using gold nanoparticles only as labels in the control experiments. This Fe(3)O(4)/PSS/PDDA/Au composite offers a great promising future for the ultrasensitive detection of other biorecognition events.

  14. Enhancing the analytical performance of electrochemical RNA aptamer-based sensors for sensitive detection of aminoglycoside antibiotics.

    PubMed

    Schoukroun-Barnes, Lauren R; Wagan, Samiullah; Wagan, Samuillah; White, Ryan J

    2014-01-21

    Folding-based electrochemical sensors utilizing structure-switching aptamers are specific, selective, sensitive, and widely applicable to the detection of a variety of target analytes. The specificity is achieved by the binding properties of an electrode-bound RNA or DNA aptamer biorecognition element. Signaling in this class of sensors arises from changes in electron transfer efficiency upon target-induced changes in the conformation/flexibility of the aptamer probe. These changes can be readily monitored electrochemically. Because of this signaling mechanism, there are several approaches to maximizing the analytical attributes (i.e., sensitivity, limit of detection, and observed binding affinity) of the aptamer sensor. Here, we present a systematic study of several approaches, including electrochemical interrogation parameters and biomolecular engineering of the aptamer sequence, to develop a sensor for the detection of aminoglycoside antibiotics. Specifically, through a combination of optimizing the electrochemical signal and engineering the parent 26-nucleotide RNA aptamer sequence to undergo larger conformation changes, we develop several improved sensors. These sensors exhibit binding affinities ranging from 220 nM to 42 μM, as much as a 100-fold improved limit of detection in comparison to previously reported sensors, and a variety of linear ranges including the therapeutic window for tobramycin. These data demonstrate that rational engineering of the aptamer structure to create large conformation changes upon target binding leads to improved sensor performance. We believe that the sensor design guidelines outlined here represent a general strategy for developing new aptamer folding-based electrochemical sensors.

  15. Enhanced Sensitivity for Electrochemical Detection Using Screen-Printed Diamond Electrodes via the Random Microelectrode Array Effect.

    PubMed

    Kondo, Takeshi; Udagawa, Ikuto; Aikawa, Tatsuo; Sakamoto, Hironori; Shitanda, Isao; Hoshi, Yoshinao; Itagaki, Masayuki; Yuasa, Makoto

    2016-02-01

    The electrochemical properties of screen-printed diamond electrodes with various insulating polyester (PES) resin binder/boron-doped diamond powder (BDDP) ratios were investigated for high sensitivity electrochemical detection. For PES/BDDP weight ratios in the range of 0.3-0.5, the BDDP-printed electrodes exhibited cyclic voltammetry (CV) characteristics for Fe(CN)6(3-/4-) that are typical of a planar electrode, whereas microelectrode-like characteristics with sigmoidal CV curves were observed for PES/BDDP ratios of 1.0-2.0. Cu elemental mapping images of copper-electrodeposited BDDP-printed electrodes indicated the formation of island structures with conductive BDDP domains surrounded by an insulating PES matrix for large PES/BDDP ratios. The electrochemical detection of ascorbic acid (AA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) was also investigated using polycrystalline BDD thin-film and BDDP-printed electrodes (PES/BDDP ratio = 0.3 and 1.0). As a result, the signal-to-background (S/B) ratios for the voltammetric detection of AA and 8-OHdG were in the order BDDP-printed electrode (PES/BDDP = 1.0) > BDDP-printed electrode (PES/BDDP = 0.3) > polycrystalline BDD thin film electrode, based on the large faradaic current with respect to the background current. Therefore, the BDDP-printed electrode with a large insulating binder/BDDP ratio has the potential for use as a disposable electrode for electrochemical detection. The electrode is cheaper, lighter and more sensitive than conventional BDD electrodes. PMID:26750090

  16. Titania nanotube-modified screen printed carbon electrodes enhance the sensitivity in the electrochemical detection of proteins.

    PubMed

    Mandal, Soumit S; Navratna, Vikas; Sharma, Pratyush; Gopal, B; Bhattacharyya, Aninda J

    2014-08-01

    The use of titania nanotubes (TiO2-NT) as the working electrode provides a substantial improvement in the electrochemical detection of proteins. A biosensor designed using this strategy provided a robust method to detect protein samples at very low concentrations (Cprotein ca 1ng/μl). Reproducible measurements on protein samples at this concentration (Ip,a of 80+1.2μA) could be achieved using a sample volume of ca 30μl. We demonstrate the feasibility of this strategy for the accurate detection of penicillin binding protein, PBP2a, a marker for methicillin resistant Staphylococcus aureus (MRSA). The selectivity and efficiency of this sensor were also validated using other diverse protein preparations such as a recombinant protein tyrosine phosphatase (PTP10D) and bovine serum albumin (BSA). This electrochemical method also presents a substantial improvement in the time taken (few minutes) when compared to conventional enzyme-linked immunosorbent assay (ELISA) protocols. It is envisaged that this sensor could substantially aid in the rapid diagnosis of bacterial infections in resource strapped environments.

  17. Electrochemical Detection in Stacked Paper Networks.

    PubMed

    Liu, Xiyuan; Lillehoj, Peter B

    2015-08-01

    Paper-based electrochemical biosensors are a promising technology that enables rapid, quantitative measurements on an inexpensive platform. However, the control of liquids in paper networks is generally limited to a single sample delivery step. Here, we propose a simple method to automate the loading and delivery of liquid samples to sensing electrodes on paper networks by stacking multiple layers of paper. Using these stacked paper devices (SPDs), we demonstrate a unique strategy to fully immerse planar electrodes by aqueous liquids via capillary flow. Amperometric measurements of xanthine oxidase revealed that electrochemical sensors on four-layer SPDs generated detection signals up to 75% higher compared with those on single-layer paper devices. Furthermore, measurements could be performed with minimal user involvement and completed within 30 min. Due to its simplicity, enhanced automation, and capability for quantitative measurements, stacked paper electrochemical biosensors can be useful tools for point-of-care testing in resource-limited settings.

  18. Rapid and highly sensitive detection of Enterovirus 71 by using nanogold-enhanced electrochemical impedance spectroscopy.

    PubMed

    Li, Hsing-Yuan; Tseng, Shing-Hua; Cheng, Tsai-Mu; Chu, Hsueh-Liang; Lu, Yu-Ning; Wang, Fang-Yu; Tsai, Li-Yun; Shieh, Juo-Yu; Yang, Jyh-Yuan; Juan, Chien-Chang; Tu, Lung-Chen; Chang, Chia-Ching

    2013-07-19

    Enterovirus 71 (EV71) infection is an emerging infectious disease causing neurological complications and/or death within two to three days after the development of fever and rash. A low viral titre in clinical specimens makes the detection of EV71 difficult. Conventional approaches for detecting EV71 are time consuming, poorly sensitive, or complicated, and cannot be used effectively for clinical diagnosis. Furthermore, EV71 and Coxsackie virus A16 (CA16) may cross react in conventional assays. Therefore, a rapid, highly sensitive, specific, and user-friendly test is needed. We developed an EV71-specific nanogold-modified working electrode for electrochemical impedance spectroscopy in the detection of EV71. Our results show that EV71 can be distinguished from CA16, Herpes simplex virus, and lysozyme, with the modified nanogold electrode being able to detect EV71 in concentrations as low as 1 copy number/50 μl reaction volume, and the duration between sample preparation and detection being 11 min. This detection platform may have the potential for use in point-of-care diagnostics.

  19. Ratiometric electrochemical detection of alkaline phosphatase.

    PubMed

    Goggins, Sean; Naz, Christophe; Marsh, Barrie J; Frost, Christopher G

    2015-01-11

    A novel ferrocene-derived substrate for the ratiometric electrochemical detection of alkaline phosphatase (ALP) was designed and synthesised. It was demonstrated to be an excellent electrochemical substrate for the ALP-labelled enzyme-linked immunosorbent assay (ELISA).

  20. Nickel/cobalt oxide-decorated 3D graphene nanocomposite electrode for enhanced electrochemical detection of urea.

    PubMed

    Nguyen, Nhi Sa; Das, Gautam; Yoon, Hyon Hee

    2016-03-15

    A NiCo2O4 bimetallic electro-catalyst was synthesized on three-dimensional graphene (3D graphene) for the non-enzymatic detection of urea. The structural and morphological properties of the NiCo2O4/3D graphene nanocomposite were characterized by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The NiCo2O4/3D graphene was deposited on an indium tin oxide (ITO) glass to fabricate a highly sensitive urea sensor. The electrochemical properties of the prepared electrode were studied by cyclic voltammetry. A high sensitivity of 166 μAmM(-)(1)cm(-)(2) was obtained for the NiCo2O4/3D graphene/ITO sensor. The sensor exhibited a linear range of 0.06-0.30 mM (R(2)=0.998) and a fast response time of approximately 1.0 s with a detection limit of 5.0 µM. Additionally, the sensor exhibited high stability with a sensitivity decrease of only 5.5% after four months of storage in ambient conditions. The urea sensor demonstrates feasibility for urea analysis in urine samples.

  1. Nickel/cobalt oxide-decorated 3D graphene nanocomposite electrode for enhanced electrochemical detection of urea.

    PubMed

    Nguyen, Nhi Sa; Das, Gautam; Yoon, Hyon Hee

    2016-03-15

    A NiCo2O4 bimetallic electro-catalyst was synthesized on three-dimensional graphene (3D graphene) for the non-enzymatic detection of urea. The structural and morphological properties of the NiCo2O4/3D graphene nanocomposite were characterized by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The NiCo2O4/3D graphene was deposited on an indium tin oxide (ITO) glass to fabricate a highly sensitive urea sensor. The electrochemical properties of the prepared electrode were studied by cyclic voltammetry. A high sensitivity of 166 μAmM(-)(1)cm(-)(2) was obtained for the NiCo2O4/3D graphene/ITO sensor. The sensor exhibited a linear range of 0.06-0.30 mM (R(2)=0.998) and a fast response time of approximately 1.0 s with a detection limit of 5.0 µM. Additionally, the sensor exhibited high stability with a sensitivity decrease of only 5.5% after four months of storage in ambient conditions. The urea sensor demonstrates feasibility for urea analysis in urine samples. PMID:26433071

  2. Multichannel electrochemical microbial detection unit

    NASA Technical Reports Server (NTRS)

    Wilkins, J. R.; Young, R. N.; Boykin, E. H.

    1978-01-01

    The paper describes the design and capabilities of a compact multichannel electrochemical unit devised to detect and automatically indicate detection time length of bacteria. By connecting this unit to a strip-chart recorder, a permanent record is obtained of the end points and growth curves for each of eight channels. The experimental setup utilizing the multichannel unit consists of a test tube (25 by 150 mm) containing a combination redox electrode plus 18 ml of lauryl tryptose broth and positioned in a 35-C water bath. Leads from the electrodes are connected to the multichannel unit, which in turn is connected to a strip-chart recorder. After addition of 2.0 ml of inoculum to the test tubes, depression of the push-button starter activates the electronics, timer, and indicator light for each channel. The multichannel unit is employed to test tenfold dilutions of various members of the Enterobacteriaceae group, and a typical dose-response curve is presented.

  3. Electrochemical immunoassay for thyroxine detection using cascade catalysis as signal amplified enhancer and multi-functionalized magnetic graphene sphere as signal tag.

    PubMed

    Han, Jing; Zhuo, Ying; Chai, Yaqin; Yu, Yanqing; Liao, Ni; Yuan, Ruo

    2013-08-01

    This paper constructed a reusable electrochemical immunosensor for the detection of thyroxine at an ultralow concentration using cascade catalysis of cytochrome c (Cyt c) and glucose oxidase (GOx) as signal amplified enhancer. It is worth pointing out that numerous Cyt c and GOx were firstly carried onto the double-stranded DNA polymers based on hybridization chain reaction (HCR), and then the amplified responses could be achieved by cascade catalysis of Cyt c and GOx recycling with the help of glucose. Moreover, multi-functionalized magnetic graphene sphere was synthesized and used as signal tag, which not only exhibited good mechanical properties, large surface area and an excellent electron transfer rate of graphene, but also possessed excellent redox activity and desirable magnetic property. With a sandwich-type immunoreaction, the proposed cascade catalysis amplification strategy could greatly enhance the sensitivity for the detection of thyroxine. Under the optimal conditions, the immunosensor showed a wide linear ranged from 0.05pg mL(-1) to 5ng mL(-1) and a low detection limit down to 15fg mL(-1). Importantly, the proposed method offers promise for reproducible and cost-effective analysis of biological samples.

  4. Signal enhancement of electrochemical biosensors via direct electrochemical oxidation of silver nanoparticle labels coated with zwitterionic polymers.

    PubMed

    Geagea, R; Aubert, P-H; Banet, P; Sanson, N

    2015-01-01

    A new electrochemical label has been developed, which is made up of silver nanoparticles (AgNPs) coated with a mixture of zwitterionic and biotinylated zwitterionic polymers. These polymers improve colloidal stability in physiological medium and ensure biorecognition while direct electrochemical oxidation of silver nanoparticles strongly enhances the detection signal. The resulting hybrid nanomaterials are used as labels in the electrochemical sensing of avidin using sandwich assays elaborated using the biotin-avidin biorecognition system.

  5. Platinum electrodes for electrochemical detection of bacteria

    NASA Technical Reports Server (NTRS)

    Wilkins, J. R.

    1979-01-01

    Bacteria is detected electro-chemically by measuring evolution of hydrogen in test system with platinum and reference electrode. Using system, electrodes of platinum are used to detect and enumerate varieties of gram-positive and gram-negative organisms compared in different media.

  6. Electrochemical immunosensors for Salmonella detection in food.

    PubMed

    Melo, Airis Maria Araújo; Alexandre, Dalila L; Furtado, Roselayne F; Borges, Maria F; Figueiredo, Evânia Altina T; Biswas, Atanu; Cheng, Huai N; Alves, Carlúcio R

    2016-06-01

    Pathogen detection is a critical point for the identification and the prevention of problems related to food safety. Failures at detecting contaminations in food may cause outbreaks with drastic consequences to public health. In spite of the real need for obtaining analytical results in the shortest time possible, conventional methods may take several days to produce a diagnosis. Salmonella spp. is the major cause of foodborne diseases worldwide and its absence is a requirement of the health authorities. Biosensors are bioelectronic devices, comprising bioreceptor molecules and transducer elements, able to detect analytes (chemical and/or biological species) rapidly and quantitatively. Electrochemical immunosensors use antibody molecules as bioreceptors and an electrochemical transducer. These devices have been widely used for pathogen detection at low cost. There are four main techniques for electrochemical immunosensors: amperometric, impedimetric, conductometric, and potentiometric. Almost all types of immunosensors are applicable to Salmonella detection. This article reviews the developments and the applications of electrochemical immunosensors for Salmonella detection, particularly the advantages of each specific technique. Immunosensors serve as exciting alternatives to conventional methods, allowing "real-time" and multiple analyses that are essential characteristics for pathogen detection and much desired in health and safety control in the food industry. PMID:27138197

  7. Electrochemical immunosensors for Salmonella detection in food.

    PubMed

    Melo, Airis Maria Araújo; Alexandre, Dalila L; Furtado, Roselayne F; Borges, Maria F; Figueiredo, Evânia Altina T; Biswas, Atanu; Cheng, Huai N; Alves, Carlúcio R

    2016-06-01

    Pathogen detection is a critical point for the identification and the prevention of problems related to food safety. Failures at detecting contaminations in food may cause outbreaks with drastic consequences to public health. In spite of the real need for obtaining analytical results in the shortest time possible, conventional methods may take several days to produce a diagnosis. Salmonella spp. is the major cause of foodborne diseases worldwide and its absence is a requirement of the health authorities. Biosensors are bioelectronic devices, comprising bioreceptor molecules and transducer elements, able to detect analytes (chemical and/or biological species) rapidly and quantitatively. Electrochemical immunosensors use antibody molecules as bioreceptors and an electrochemical transducer. These devices have been widely used for pathogen detection at low cost. There are four main techniques for electrochemical immunosensors: amperometric, impedimetric, conductometric, and potentiometric. Almost all types of immunosensors are applicable to Salmonella detection. This article reviews the developments and the applications of electrochemical immunosensors for Salmonella detection, particularly the advantages of each specific technique. Immunosensors serve as exciting alternatives to conventional methods, allowing "real-time" and multiple analyses that are essential characteristics for pathogen detection and much desired in health and safety control in the food industry.

  8. Embroidered electrochemical sensors for biomolecular detection.

    PubMed

    Liu, Xiyuan; Lillehoj, Peter B

    2016-05-24

    Electrochemical sensors are powerful analytical tools which possess the capacity for rapid detection of biomarkers in clinical specimens. While most electrochemical sensors are fabricated on rigid substrates, there is a growing need for sensors that can be manufactured on inexpensive and flexible materials. Here, we present a unique embroidered electrochemical sensor that is capable of quantitative analytical measurements using raw biofluid samples. Conductive threads immobilized with enzyme probes were generated using a simple and robust fabrication process and used to fabricate flexible, mechanically robust electrodes on textiles. For proof of concept, measurements were performed to detect glucose and lactate in buffer and whole blood samples, which exhibited excellent specificity and accuracy. We also demonstrate that our embroidered biosensor can be readily fabricated in two-dimensional (2D) arrays for multiplexed measurements. Lastly, we show that this biosensor exhibits good resiliency against mechanical stress and superior repeatability, which are important requirements for flexible sensor platforms. PMID:27156700

  9. Invertase inhibition based electrochemical sensor for the detection of heavy metal ions in aqueous system: Application of ultra-microelectrode to enhance sucrose biosensor's sensitivity.

    PubMed

    Bagal-Kestwal, Dipali; Karve, Meena S; Kakade, Bhalchandra; Pillai, Vijayamohanan K

    2008-12-01

    We are reporting fabrication and characterization of electrochemical sucrose biosensor using ultra-microelectrode (UME) for the detection of heavy metal ions (Hg(II), Ag(I), Pb(II) and Cd(II)). The working UME, with 25 microm diameter, was modified with invertase (INV, EC: 3.2.1.26) and glucose oxidase (GOD, EC: 1.1.3.4) entrapped in agarose-guar gum. The hydrophilic character of the agarose-guar gum composite matrix was checked by water contact angle measurement. The atomic force microscopy (AFM) images of the membranes showed proper confinement of both the enzymes during co-immobilization. The dynamic range for sucrose biosensor was achieved in the range of 1 x 10(-10) to 1 x 10(-7)M with lower detection limit 1 x 10(-10)M at pH 5.5 with 9 cycles of reuse. The spectrophotometric and electrochemical studies showed linear relationship between concentration of heavy metal ions and degree of inhibition of invertase. The toxicity sequence for invertase using both methods was observed as Hg(2+)>Pb(2+)>Ag(+)>Cd(2+). The dynamic linear range for mercury using electrochemical biosensor was observed in the range of 5 x 10(-10) to 12.5 x 10(-10)M for sucrose. The lower detection limit for the fabricated biosensor was found to be 5 x 10(-10)M. The reliability of the electrochemical biosensor was conformed by testing the spike samples and the results were comparable with the conventional photometric DNSA method. PMID:18667298

  10. Invertase inhibition based electrochemical sensor for the detection of heavy metal ions in aqueous system: Application of ultra-microelectrode to enhance sucrose biosensor's sensitivity.

    PubMed

    Bagal-Kestwal, Dipali; Karve, Meena S; Kakade, Bhalchandra; Pillai, Vijayamohanan K

    2008-12-01

    We are reporting fabrication and characterization of electrochemical sucrose biosensor using ultra-microelectrode (UME) for the detection of heavy metal ions (Hg(II), Ag(I), Pb(II) and Cd(II)). The working UME, with 25 microm diameter, was modified with invertase (INV, EC: 3.2.1.26) and glucose oxidase (GOD, EC: 1.1.3.4) entrapped in agarose-guar gum. The hydrophilic character of the agarose-guar gum composite matrix was checked by water contact angle measurement. The atomic force microscopy (AFM) images of the membranes showed proper confinement of both the enzymes during co-immobilization. The dynamic range for sucrose biosensor was achieved in the range of 1 x 10(-10) to 1 x 10(-7)M with lower detection limit 1 x 10(-10)M at pH 5.5 with 9 cycles of reuse. The spectrophotometric and electrochemical studies showed linear relationship between concentration of heavy metal ions and degree of inhibition of invertase. The toxicity sequence for invertase using both methods was observed as Hg(2+)>Pb(2+)>Ag(+)>Cd(2+). The dynamic linear range for mercury using electrochemical biosensor was observed in the range of 5 x 10(-10) to 12.5 x 10(-10)M for sucrose. The lower detection limit for the fabricated biosensor was found to be 5 x 10(-10)M. The reliability of the electrochemical biosensor was conformed by testing the spike samples and the results were comparable with the conventional photometric DNSA method.

  11. Electrochemical aptasensor for detecting tetracycline in milk

    NASA Astrophysics Data System (ADS)

    Hanh Le, Thi; Phuc Pham, Van; Huyen La, Thi; Binh Phan, Thi; Huan Le, Quang

    2016-03-01

    A rapid, simple and sensitive biosensor system for tetracycline detection is very important in food safety. In this paper we developed a label-free aptasensor for electrochemical detection of tetracycline. According to the electrochemical impendence spectroscopy (EIS) analysis, there was a linear relationship between the concentration of tetracycline and the electron transfer resistance from 10 to 3000 ng ml-1 of the tetracycline concentration. The detection limit was 10 ng ml-1 in 15 min detection duration. The prepared aptasensor showed a good reproducibility with an acceptable stability in tetracycline detection. The recoveries of tetracycline in spiked milk samples were in the range of 88.1%-94.2%. The aptasensor has sensitivity 98% and specificity of 100%.

  12. Detection Limits and Selectivity in Electrochemical Detectors.

    ERIC Educational Resources Information Center

    Weber, Stephen G.; Long, John T.

    1988-01-01

    Discusses three aspects of electrochemical detectors: (1) signal and noise generation and signal-to-noise ratio, (2) improvement of qualitative information content, and (3) control of selectivity of the detector. Explains electronic principles of detectors and detection limits. Lists current applications and research. (ML)

  13. Electrochemical X-ray fluorescence spectroscopy for trace heavy metal analysis: enhancing X-ray fluorescence detection capabilities by four orders of magnitude.

    PubMed

    Hutton, Laura A; O'Neil, Glen D; Read, Tania L; Ayres, Zoë J; Newton, Mark E; Macpherson, Julie V

    2014-05-01

    The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales). Large area free-standing boron doped diamond grown using microwave plasma chemical vapor deposition techniques is found to be ideal as the electrode material for both electrodeposition and XRF due to its wide solvent window, transparency to the XRF beam, and ability to be produced in mechanically robust freestanding thin film form. During electrodeposition it is possible to vary both the deposition potential (Edep) and deposition time (tdep). For the metals Cu(2+) and Pb(2+) the highest detection sensitivities were found for Edep = -1.75 V and tdep (=) 4000 s with LODs of 0.05 and 0.04 ppb achieved, respectively. In mixed Cu(2+)/Pb(2+) solutions, EC-XRF shows that Cu(2+) deposition is unimpeded by Pb(2+), across a broad concentration range, but this is only true for Pb(2+) when both metals are present at low concentrations (10 nM), boding well for trace level measurements. In a dual mixed metal solution, EC-XRF can also be employed to either selectively deposit the metal which has the most positive formal reduction potential, E(0), or exhaustively deplete it from solution, enabling uninhibited detection of the metal with the more negative E(0).

  14. Zeptomole Electrochemical Detection of Metallothioneins

    PubMed Central

    Adam, Vojtech; Petrlova, Jitka; Wang, Joseph; Eckschlager, Tomas; Trnkova, Libuse; Kizek, Rene

    2010-01-01

    Background Thiol-rich peptides and proteins possess a large number of biological activities and may serve as markers for numerous health problems including cancer. Metallothionein (MT), a small molecular mass protein rich in cysteine, may be considered as one of the promising tumour markers. The aim of this paper was to employ chronopotentiometric stripping analysis (CPSA) for highly sensitive detection of MT. Methodology/Principal Findings In this study, we used adsorptive transfer stripping technique coupled with CPSA for detection of cysteine, glutathione oxidized and reduced, phytochelatin, bovine serum albumin, and metallothionein. Under the optimal conditions, we were able to estimate detection limits down to tens of fg per ml. Further, this method was applied to detect metallothioneins in blood serum obtained from patients with breast cancer and in neuroblastoma cells resistant and sensitive to cisplatin in order to show the possible role of metallothioneins in carcinogenesis. It was found that MT level in blood serum was almost twice higher as compared to the level determined in healthy individuals. Conclusions/Significance This paper brings unique results on the application of ultra-sensitive electroanalytical method for metallothionein detection. The detection limit and other analytical parameters are the best among the parameters of other techniques. In spite of the fact that the paper is mainly focused on metallothionein, it is worth mentioning that successful detection of other biologically important molecules is possible by this method. Coupling of this method with simple isolation methods such as antibody-modified paramagnetic particles may be implemented to lab–on-chip instrument. PMID:20625429

  15. Electrochemical characterization of riboflavin-enhanced reduction of trinitrotoluene.

    PubMed

    Sumner, James J; Chu, Kevin

    2011-01-01

    There is great interest in understanding trinitrotoluene (TNT) and dinitrotoluene (DNT) contamination, detection and remediation in the environment due to TNT's negative health effects and security implications. Numerous publications have focused on detecting TNT in groundwater using multiple techniques, including electrochemistry. The main degradation pathway of nitrotoluenes in the environment is reduction, frequently with biological and/or photolytic assistance. Riboflavin has also been noted to aid in TNT remediation in soils and groundwater when exposed to light. This report indicates that adding riboflavin to a TNT or DNT solution enhances redox currents in electrochemical experiments. Here AC voltammetry was performed and peak currents compared with and without riboflavin present. Results indicated that TNT, DNT and riboflavin could be detected using AC voltammetry on modified gold electrodes and the addition of riboflavin affected redox peaks of TNT and DNT. Poised potential experiments indicated that it is possible to enhance reduction of TNT in the presence of riboflavin and light. These results were dramatic enough to explain long term enhancement of bioremediation in environments containing high levels of riboflavin and enhance the limit of detection in electrochemically-based nitrotoluene sensing.

  16. Nitroaromatic explosives detection using electrochemically exfoliated graphene.

    PubMed

    Yew, Ying Teng; Ambrosi, Adriano; Pumera, Martin

    2016-01-01

    Detection of nitroaromatic explosives is of paramount importance from security point of view. Graphene sheets obtained from the electrochemical anodic exfoliation of graphite foil in different electrolytes (LiClO4 and Na2SO4) were compared and tested as electrode material for the electrochemical detection of 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) in seawater. Voltammetry analysis demonstrated the superior electrochemical performance of graphene produced in LiClO4, resulting in higher sensitivity and linearity for the explosives detection and lower limit of detection (LOD) compared to the graphene obtained in Na2SO4. We attribute this to the presence of oxygen functionalities onto the graphene material obtained in LiClO4 which enable charge electrostatic interactions with the -NO2 groups of the analyte, in addition to π-π stacking interactions with the aromatic moiety. Research findings obtained from this study would assist in the development of portable devices for the on-site detection of nitroaromatic explosives. PMID:27633489

  17. Nitroaromatic explosives detection using electrochemically exfoliated graphene

    NASA Astrophysics Data System (ADS)

    Yew, Ying Teng; Ambrosi, Adriano; Pumera, Martin

    2016-09-01

    Detection of nitroaromatic explosives is of paramount importance from security point of view. Graphene sheets obtained from the electrochemical anodic exfoliation of graphite foil in different electrolytes (LiClO4 and Na2SO4) were compared and tested as electrode material for the electrochemical detection of 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) in seawater. Voltammetry analysis demonstrated the superior electrochemical performance of graphene produced in LiClO4, resulting in higher sensitivity and linearity for the explosives detection and lower limit of detection (LOD) compared to the graphene obtained in Na2SO4. We attribute this to the presence of oxygen functionalities onto the graphene material obtained in LiClO4 which enable charge electrostatic interactions with the –NO2 groups of the analyte, in addition to π-π stacking interactions with the aromatic moiety. Research findings obtained from this study would assist in the development of portable devices for the on-site detection of nitroaromatic explosives.

  18. Nitroaromatic explosives detection using electrochemically exfoliated graphene

    PubMed Central

    Yew, Ying Teng; Ambrosi, Adriano; Pumera, Martin

    2016-01-01

    Detection of nitroaromatic explosives is of paramount importance from security point of view. Graphene sheets obtained from the electrochemical anodic exfoliation of graphite foil in different electrolytes (LiClO4 and Na2SO4) were compared and tested as electrode material for the electrochemical detection of 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) in seawater. Voltammetry analysis demonstrated the superior electrochemical performance of graphene produced in LiClO4, resulting in higher sensitivity and linearity for the explosives detection and lower limit of detection (LOD) compared to the graphene obtained in Na2SO4. We attribute this to the presence of oxygen functionalities onto the graphene material obtained in LiClO4 which enable charge electrostatic interactions with the –NO2 groups of the analyte, in addition to π-π stacking interactions with the aromatic moiety. Research findings obtained from this study would assist in the development of portable devices for the on-site detection of nitroaromatic explosives. PMID:27633489

  19. Nanoparticles for Enhanced Sensitivity in Electrochemical Immunoassays

    SciTech Connect

    Lin, Yuehe; Wang, Jun; Wang, Hua; Wu, Hong; Tang, Zhiwen

    2008-10-12

    In this manuscript, we report on electrochemical biosensors based on various nanoparticles (NPs) as labels for sensitive detection of protein biomarkers. We used silica nanoparticle as a carrier to loading a large amount of electroactive species such as poly(guanine) for sensitive immunoassay of tumor necrosis factor-alpha (TNF-a). We took the advantages of the unique hollow structure and reconstruction properties of apoferritin to prepare Cd3(PO4)2 nanoparticles as labels for sensitive assay of TNF-a. A novel immunochromatographic/electro-chemical biosensor based on quantum dots as labels has also been developed for rapid and sensitive detection of prostate-specific antigen (PSA) in human serum. These biosensors are quite sensitive with the detection limit at pM level and these approaches based on nanoparticle labels offer a new avenue for sensitive detection of protein biomarkers.

  20. Disposable Electrochemical Immunosensors for Pcb Detection

    NASA Astrophysics Data System (ADS)

    Laschi, S.; Mascini, M.; Fránek, M.

    2000-12-01

    We realised an electrochemical enzyme immunoassay for polychlorinated biphenyls (PCB) using carbon-based screen-printed disposable electrodes as solid-phase for reagent immobilisation and as signal transducer. Horseradish peroxidase (HRP) conjugate with Ag or Ab as enzyme label was used; hydrogen peroxide and ferrocenemonocarboxylic acid (FCA) as mediator were employed in order to evaluate the HRP activity in the range 10-8-10-10 M. Indirect and direct competitive assays for PCB were performed and a detection limit of 0.01 μg/mL was obtained in direct competitive format. The advantage of this approach is the relatively fast analysis (30 min) in comparison with a test based on microtiter assay plates (14h); moreover, the use of disposable screen-printed electrodes eliminates the problems of fouling and surface regeneration of electrochemical device.

  1. Single-Nanowire Electrochemical Probe Detection for Internally Optimized Mechanism of Porous Graphene in Electrochemical Devices.

    PubMed

    Hu, Ping; Yan, Mengyu; Wang, Xuanpeng; Han, Chunhua; He, Liang; Wei, Xiujuan; Niu, Chaojiang; Zhao, Kangning; Tian, Xiaocong; Wei, Qiulong; Li, Zijia; Mai, Liqiang

    2016-03-01

    Graphene has been widely used to enhance the performance of energy storage devices due to its high conductivity, large surface area, and excellent mechanical flexibility. However, it is still unclear how graphene influences the electrochemical performance and reaction mechanisms of electrode materials. The single-nanowire electrochemical probe is an effective tool to explore the intrinsic mechanisms of the electrochemical reactions in situ. Here, pure MnO2 nanowires, reduced graphene oxide/MnO2 wire-in-scroll nanowires, and porous graphene oxide/MnO2 wire-in-scroll nanowires are employed to investigate the capacitance, ion diffusion coefficient, and charge storage mechanisms in single-nanowire electrochemical devices. The porous graphene oxide/MnO2 wire-in-scroll nanowire delivers an areal capacitance of 104 nF/μm(2), which is 4.0 and 2.8 times as high as those of reduced graphene oxide/MnO2 wire-in-scroll nanowire and MnO2 nanowire, respectively, at a scan rate of 20 mV/s. It is demonstrated that the reduced graphene oxide wrapping around the MnO2 nanowire greatly increases the electronic conductivity of the active materials, but decreases the ion diffusion coefficient because of the shielding effect of graphene. By creating pores in the graphene, the ion diffusion coefficient is recovered without degradation of the electron transport rate, which significantly improves the capacitance. Such single-nanowire electrochemical probes, which can detect electrochemical processes and behavior in situ, can also be fabricated with other active materials for energy storage and other applications in related fields.

  2. Single-Nanowire Electrochemical Probe Detection for Internally Optimized Mechanism of Porous Graphene in Electrochemical Devices.

    PubMed

    Hu, Ping; Yan, Mengyu; Wang, Xuanpeng; Han, Chunhua; He, Liang; Wei, Xiujuan; Niu, Chaojiang; Zhao, Kangning; Tian, Xiaocong; Wei, Qiulong; Li, Zijia; Mai, Liqiang

    2016-03-01

    Graphene has been widely used to enhance the performance of energy storage devices due to its high conductivity, large surface area, and excellent mechanical flexibility. However, it is still unclear how graphene influences the electrochemical performance and reaction mechanisms of electrode materials. The single-nanowire electrochemical probe is an effective tool to explore the intrinsic mechanisms of the electrochemical reactions in situ. Here, pure MnO2 nanowires, reduced graphene oxide/MnO2 wire-in-scroll nanowires, and porous graphene oxide/MnO2 wire-in-scroll nanowires are employed to investigate the capacitance, ion diffusion coefficient, and charge storage mechanisms in single-nanowire electrochemical devices. The porous graphene oxide/MnO2 wire-in-scroll nanowire delivers an areal capacitance of 104 nF/μm(2), which is 4.0 and 2.8 times as high as those of reduced graphene oxide/MnO2 wire-in-scroll nanowire and MnO2 nanowire, respectively, at a scan rate of 20 mV/s. It is demonstrated that the reduced graphene oxide wrapping around the MnO2 nanowire greatly increases the electronic conductivity of the active materials, but decreases the ion diffusion coefficient because of the shielding effect of graphene. By creating pores in the graphene, the ion diffusion coefficient is recovered without degradation of the electron transport rate, which significantly improves the capacitance. Such single-nanowire electrochemical probes, which can detect electrochemical processes and behavior in situ, can also be fabricated with other active materials for energy storage and other applications in related fields. PMID:26882441

  3. Harnessing aptamers for electrochemical detection of endotoxin.

    PubMed

    Kim, Sung-Eun; Su, Wenqiong; Cho, MiSuk; Lee, Youngkwan; Choe, Woo-Seok

    2012-05-01

    Lipopolysaccharide (LPS), also known as endotoxin, triggers a fatal septic shock; therefore, fast and accurate detection of LPS from a complex milieu is of primary importance. Several LPS affinity binders have been reported so far but few of them have proved their efficacy in developing electrochemical sensors capable of selectively detecting LPS from crude biological liquors. In this study, we identified 10 different single-stranded DNA aptamers showing specific affinity to LPS with dissociation constants (K(d)) in the nanomolar range using a NECEEM-based non-SELEX method. Based on the sequence and secondary structure analysis of the LPS binding aptamers, an aptamer exhibiting the highest affinity to LPS (i.e., B2) was selected to construct an impedance biosensor on a gold surface. The developed electrochemical aptasensor showed excellent sensitivity and specificity in the linear detection range from 0.01 to 1 ng/mL of LPS with significantly reduced detection time compared with the traditional Limulus amoebocyte lysate (LAL) assay. PMID:22370280

  4. Pulsed electrochemical detection in bioanalysis: chemical fingerprinting

    NASA Astrophysics Data System (ADS)

    LaCourse, William R.

    2004-03-01

    Pulsed Electrochemical Detection (PED) is a revolutionary approach to the simple, sensitive, and direct detection of numerous polar aliphatic compounds, especially carbohydrates. This technique exploits the electrocatalytic activity of noble metal electrode surfaces to oxidize various polar functional groups. In PED, multi-step potential-time waveforms at Au and Pt electrodes realize amperometric/coulometric detection while maintaining uniform and reproducible electrode activity. The response mechanisms in PED are dominated by the surface properties of the electrode, and, as a consequence, members of each chemical class of compounds produce virtually identical voltammetric responses. Thus, the full potential is realized when combined with high performance liquid chromatography (HPLC). This paper reviews the fundamental aspects of PED and details a novel approach to the chemical "fingerprinting" of natural products. Applications include the characterization of tobacco, peptones, and bacteria.

  5. Detection of theophylline utilising portable electrochemical sensors.

    PubMed

    Wang, Tiancheng; Randviir, Edward P; Banks, Craig E

    2014-04-21

    The electrochemical oxidation of theophylline (TP) is investigated utilising screen-printed electrodes. Through thorough investigation of pH, we propose a reaction mechanism, finding that the oxidation of TP is stable over a wide pH range, in particular under acidic conditions. Conversely under alkaline conditions, theophylline fouls the electrode surface. The screen-printed carbon sensors are applied towards the electroanalytical sensing of TP with a remarkable amount of success in aqueous solution at physiological pH. The screen-printed sensors have been shown to be applicable to the detection of TP at unharmful, medicinally relevant (55-110 μM), and toxic concentrations in aqueous media at physiological pH. Thus this work presents a proof-of-concept approach towards TP detection utilising sensors commonly implemented in point-of-care applications.

  6. Electrochemical synthesis and one step modification of PMProDot nanotubes and their enhanced electrochemical properties.

    PubMed

    Nguyen, Thao M; Cho, Seungil; Varongchayakul, Nitinun; Yoon, Daehyun; Seog, Joonil; Zong, Kyukwan; Lee, Sang Bok

    2012-03-11

    Poly (3,4-(2-methylene)propylenedioxythiophene) (PMProDot) nanotubes were synthesized within the pores of polycarbonate and were further modified with styrene and vinylcarbazole by a one step electrochemical method through the methylene functional group. The enhanced electrochemical and electrochromic properties of composite nanotubes were investigated using FTIR, UV/Vis absorbance spectroscopy, and AFM.

  7. Parallel Optical and Electrochemical DNA Detection

    NASA Astrophysics Data System (ADS)

    Knoll, Wolfgang; Liu, Jianyun; Niu, Lifang; Nielsen, Peter Eigil; Tiefenauer, Louis

    This contribution introduces strategies for the sensitive detection of oligonucleotides as bio-analytes binding from solution to a variety of probe architectures assembled at the (Au-) sensor surface. Detection principles based on surface plasmon optics and electrochemical techniques are compared. In particular, cyclic- and square wave voltammetry (SWV) are applied for the read-out of ferrocene redox labels conjugated to streptavidin that binds to the (biotinylated) DNA targets after hybridizing to the interfacial probe matrix of either DNA or peptide nucleic acid (PNA) strands. By employing streptavidin modified with fluorophores the identical sensor architecture can be used for the recording of hybridization reactions by surface plasmon fluorescence spectroscopy (SPFS). The Langmuir isotherms determined by both techniques, i.e., by SWV and SPFS, give virtually identical affinity constants KA, confirming that the mode of detection has no influence on the hybridization reaction. By using semiconducting nanoparticles as luminescence labels that can be tuned in their bandgap energies over a wide range of emission wavelengths surface plasmon fluorescence microscopy allows for the parallel read-out of multiple analyte binding events simultaneously.

  8. Portable pH-inspired electrochemical detection of DNA amplification.

    PubMed

    Zhang, Fang; Wu, Jian; Wang, Rui; Wang, Liu; Ying, Yibin

    2014-08-01

    A portable and label-free pH-mediated electrochemical method for the detection of DNA amplification is described. With protons released as readouts, DNA amplifications were detected in real-time or at the end-point.

  9. Enhanced simultaneous detection of ractopamine and salbutamol--Via electrochemical-facial deposition of MnO2 nanoflowers onto 3D RGO/Ni foam templates.

    PubMed

    Wang, Ming Yan; Zhu, Wei; Ma, Lin; Ma, Juan Juan; Zhang, Dong En; Tong, Zhi Wei; Chen, Jun

    2016-04-15

    In this paper, we report a facile method to successfully fabricate MnO2 nanoflowers loaded onto 3D RGO@nickel foam, showing enhanced biosensing activity due to the improved structural integration of different electrode materials components. When the as-prepared 3D hybrid electrodes were investigated as a binder-free biosensor, two well-defined and separate differential pulse voltammetric peaks for ractopamine (RAC) and salbutamol (SAL) were observed, indicating the simultaneous selective detection of both β-agonists possible. The MnO2/RGO@NF sensor also demonstrated a linear relationship over a wide concentration range of 17 nM to 962 nM (R=0.9997) for RAC and 42 nM to 1463 nM (R=0.9996) for SAL, with the detection limits of 11.6 nM for RAC and 23.0 nM for SAL. In addition, the developed MnO2/RGO@NF sensor was further investigated to detect RAC and SAL in pork samples, showing satisfied comparable results in comparison with analytic results from HPLC.

  10. Electrochemical Detection of Multiple Bioprocess Analytes

    NASA Technical Reports Server (NTRS)

    Rauh, R. David

    2010-01-01

    An apparatus that includes highly miniaturized thin-film electrochemical sensor array has been demonstrated as a prototype of instruments for simultaneous detection of multiple substances of interest (analytes) and measurement of acidity or alkalinity in bioprocess streams. Measurements of pH and of concentrations of nutrients and wastes in cell-culture media, made by use of these instruments, are to be used as feedback for optimizing the growth of cells or the production of desired substances by the cultured cells. The apparatus is designed to utilize samples of minimal volume so as to minimize any perturbation of monitored processes. The apparatus can function in a potentiometric mode (for measuring pH), an amperometric mode (detecting analytes via oxidation/reduction reactions), or both. The sensor array is planar and includes multiple thin-film microelectrodes covered with hydrous iridium oxide. The oxide layer on each electrode serves as both a protective and electrochemical transducing layer. In its transducing role, the oxide provides electrical conductivity for amperometric measurement or pH response for potentiometric measurement. The oxide on an electrode can also serve as a matrix for one or more enzymes that render the electrode sensitive to a specific analyte. In addition to transducing electrodes, the array includes electrodes for potential control. The array can be fabricated by techniques familiar to the microelectronics industry. The sensor array is housed in a thin-film liquid-flow cell that has a total volume of about 100 mL. The flow cell is connected to a computer-controlled subsystem that periodically draws samples from the bioprocess stream to be monitored. Before entering the cell, each 100-mL sample is subjected to tangential-flow filtration to remove particles. In the present version of the apparatus, the electrodes are operated under control by a potentiostat and are used to simultaneously measure the pH and the concentration of glucose

  11. A new electrochemically active-inactive switching aptamer molecular beacon to detect thrombin directly in solution.

    PubMed

    Cheng, Guifang; Shen, Bijun; Zhang, Fan; Wu, Jikui; Xu, Ying; He, Pingang; Fang, Yuzhi

    2010-06-15

    A new electrochemical aptamer molecular beacon (MB) was designed by the carminic acid (CA) covalently linking at the each end of a special single-stranded stem-loop shaped oligonucleotide and named as CAs-MB. CA is an electrochemically active molecule and two CA molecules at the ends of molecular beacon stem were closed enough to associate each other to be as CA dimer. The dimer was electrochemically inactive. It separated into two CA monomers and produced the electrochemical signal while CAs-MB combined with target. In this protocol, the detection strategy of CAs-MB for thrombin is based on electrochemical active-inactive switching between monomer and dimer forms of CA. In order to enhance the electrochemical signal, magnetic nanobeads (MNB) was applied by connecting CAs-MB with MNB through a duplex of DNA. With the magnetic enrichment, the detection limit for thrombin reached to 42.4 pM. The experiment results showed that this type of electrochemical active-inactive switching aptamer molecular beacon allowed the direct detection of target proteins in the solution with no requirement of removing uncombined CAs-MB. Besides, CAs-MB/MNB can be easily regenerated by using 2M NaCl solution to cleave the thrombin from the aptasensor. PMID:20378327

  12. A new electrochemically active-inactive switching aptamer molecular beacon to detect thrombin directly in solution.

    PubMed

    Cheng, Guifang; Shen, Bijun; Zhang, Fan; Wu, Jikui; Xu, Ying; He, Pingang; Fang, Yuzhi

    2010-06-15

    A new electrochemical aptamer molecular beacon (MB) was designed by the carminic acid (CA) covalently linking at the each end of a special single-stranded stem-loop shaped oligonucleotide and named as CAs-MB. CA is an electrochemically active molecule and two CA molecules at the ends of molecular beacon stem were closed enough to associate each other to be as CA dimer. The dimer was electrochemically inactive. It separated into two CA monomers and produced the electrochemical signal while CAs-MB combined with target. In this protocol, the detection strategy of CAs-MB for thrombin is based on electrochemical active-inactive switching between monomer and dimer forms of CA. In order to enhance the electrochemical signal, magnetic nanobeads (MNB) was applied by connecting CAs-MB with MNB through a duplex of DNA. With the magnetic enrichment, the detection limit for thrombin reached to 42.4 pM. The experiment results showed that this type of electrochemical active-inactive switching aptamer molecular beacon allowed the direct detection of target proteins in the solution with no requirement of removing uncombined CAs-MB. Besides, CAs-MB/MNB can be easily regenerated by using 2M NaCl solution to cleave the thrombin from the aptasensor.

  13. HME powder detection using space sampling and electrochemical sensors

    NASA Astrophysics Data System (ADS)

    Cagan, Avi; Wang, Joseph; Cizek, Karel; Lu, Donglai; La Belle, Jeffrey

    2009-05-01

    A new concept for effective sampling and detecting HME powder traces is described. The collection is based on the particles mobility under rotation into an accumulation collector unit, followed by sequential transfer to the electrochemical detection system where surface washing yields a higher concentration at room temperature. The electrochemical detection of the peroxide explosives is based on photochemical degradation or acid treatment resulting in hydrogen peroxide which is sensed by a Prussian-blue (PB) modified strip electrode at a low potential. Nitrates such as Urea Nitrate are detected using unique reactions which generate one product which has a specific electrochemical signature. Nitroaromatics, nitramines and nitroesters are detected. The new "Add and Detect" procedure is operator independent and is the safest as the operator.

  14. Triggering interface potential barrier: A controllable tuning mechanism for electrochemical detection.

    PubMed

    Ding, Longjiang; Zhao, Minggang; Ma, Ye; Fan, Sisi; Wen, Zhen; Huang, Jingyun; Liang, Jingjing; Chen, Shougang

    2016-11-15

    A novel theory of employing interface potential barriers as a controllabe tuning factor for electrochemical detection is proposed. The 3D NiO/PANI/ZnO hierarchical heterostructure is fabricated by thermal oxidation, electropolymerization and electrodeposition. The 3D NiO/PANI/ZnO heterostructure is then chose as a model for electrochemical detection of dopamine, uric acid and ascorbic acid. The p-n and p-p junction interface potential barriers are employed as tuning factors to achieve high selectivity and sensitivity. Our results demonstrate the electrochemical response to different targets can be controllable enhanced or weakened by rational design of interface potential barriers. The potential barrier height Φp-n is an enhanced tuning factor, and Φp-p is a selective tuning factor. We afford a controllable adjustive approach to achieve desired selectivity and sensitivity. PMID:27295574

  15. Enhanced electrochemical lithium storage by graphene nanoribbons.

    PubMed

    Bhardwaj, Tarun; Antic, Aleks; Pavan, Barbara; Barone, Veronica; Fahlman, Bradley D

    2010-09-15

    Herein, we report the electrochemical Li intake capacity of carbonaceous one-dimensional graphene nanoribbons (GNRs) obtained by unzipping pristine multiwalled carbon nanotubes (MWCNTs). We have found that nanotubes with diameters of approximately 50 nm present a smaller reversible capacity than conventional mesocarbon microbead (MCMB) powder. Reduced GNRs improve the capacity only marginally over the MCMB reference but present a lower Coulombic efficiency as well as a higher capacity loss per cycle. Oxidized GNRs (ox-GNRs) outperform all of the other materials studied here in terms of energy density. They present a first charge capacity of approximately 1400 mA h g(-1) with a low Coulombic efficiency for the first cycle (approximately 53%). The reversible capacity of ox-GNRs is in the range of 800 mA h g(-1), with a capacity loss per cycle of approximately 3% for early cycles and a decreasing loss rate for subsequent cycles.

  16. Maltodextrin enhances biofilm elimination by electrochemical scaffold

    PubMed Central

    Sultana, Sujala T.; Call, Douglas R.; Beyenal, Haluk

    2016-01-01

    Electrochemical scaffolds (e-scaffolds) continuously generate low concentrations of H2O2 suitable for damaging wound biofilms without damaging host tissue. Nevertheless, retarded diffusion combined with H2O2 degradation can limit the efficacy of this potentially important clinical tool. H2O2 diffusion into biofilms and bacterial cells can be increased by damaging the biofilm structure or by activating membrane transportation channels by exposure to hyperosmotic agents. We hypothesized that e-scaffolds would be more effective against Acinetobacter baumannii and Staphylococcus aureus biofilms in the presence of a hyperosmotic agent. E-scaffolds polarized at −600 mVAg/AgCl were overlaid onto preformed biofilms in media containing various maltodextrin concentrations. E-scaffold alone decreased A. baumannii and S. aureus biofilm cell densities by (3.92 ± 0.15) log and (2.31 ± 0.12) log, respectively. Compared to untreated biofilms, the efficacy of the e-scaffold increased to a maximum (8.27 ± 0.05) log reduction in A. baumannii and (4.71 ± 0.12) log reduction in S. aureus biofilm cell densities upon 10 mM and 30 mM maltodextrin addition, respectively. Overall ~55% decrease in relative biofilm surface coverage was achieved for both species. We conclude that combined treatment with electrochemically generated H2O2 from an e-scaffold and maltodextrin is more effective in decreasing viable biofilm cell density. PMID:27782161

  17. Addition of nitrite enhances the electrochemical defluorination of 2-fluoroaniline.

    PubMed

    Feng, Huajun; Liang, Yuxiang; Guo, Kun; Long, Yuyang; Cong, Yanqing; Shen, Dongsheng

    2015-12-30

    This study introduces a novel approach that uses the interaction of pollutants with added nitrite to produce diazonium salts, which cause in situ self-assembly of the pollutants on carbon electrodes, to improve their 2-fluoroaniline (2-FA) defluorination and removal performance. The 2-FA degradation performance, electrode properties, electrochemical properties and degradation pathway were investigated. The reactor containing NO2(-) achieved a 2-FA removal efficiency of 90.1% and a defluorination efficiency of 38% within 48 h, 1.4 and 2.3 times higher than the corresponding results achieved without NO2(-), respectively. The residual NO2(-) was less than 0.5mg/L in the reactor containing added NO2(-), which would not cause serious secondary pollution. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) results proved that the carbon anode surface was successfully modified with benzene polymer, and electrochemical tests confirmed that the electrochemical activity of the modified anode was enhanced significantly. The C-F bond was weakened by the effect of the positive charge of the benzenediazonium groups, and the high electrochemical activity of the carbon anode enhanced the electrochemical performance of the system to accelerate defluorination. Thus, the present electrical method involving nitrite nitrogen is very promising for the treatment of wastewater containing fluoroaniline compounds.

  18. An electrochemical aptasensor electrocatalyst for detection of thrombin.

    PubMed

    Tian, Rong; Chen, Xiaojun; Li, Qingwen; Yao, Cheng

    2016-05-01

    This work reports a novel signal amplification strategy based on three-dimensional ordered macroporous C60-poly(3,4-ethylenedioxythiophene)-1-butyl-3-methylimidazolium hexafluorophosphate (3DOM C60-PEDOT-[BMIm][BF6]) for ultrasensitive detection of thrombin by cascade catalysis of Au-PEDOT@SiO2 microspheres and alcohol dehydrogenase (ADH). Au-PEDOT@SiO2 microspheres were constructed not only as nanocarriers to anchor the large amounts of secondary thrombin aptamers but also as nanocatalysts to catalyze the oxidation of ethanol efficiently. Significantly, the electrochemical signal was greatly enhanced based on cascade catalysis: First, ADH catalyzed the oxidation of ethanol to acetaldehyde with the concomitant generation of NADH in the presence of β-nicotinamide adenine dinucleotide hydrate (NAD(+)). Then, gold nanoparticles (AuNPs) as nanocatalysts could effectively catalyze NADH to produce NAD(+) with the help of PEDOT as redox probe. Under the optimal conditions, the proposed aptasensor exhibits a linear range of 2 × 10(-13) to 2 × 10(-8) M with a low detection limit of 2 × 10(-14) M for thrombin detection and shows high sensitivity and good specificity. PMID:26869084

  19. Enhanced electrochemical etching of ion irradiated silicon by localized amorphization

    SciTech Connect

    Dang, Z. Y.; Breese, M. B. H.; Lin, Y.; Tok, E. S.; Vittone, E.

    2014-05-12

    A tailored distribution of ion induced defects in p-type silicon allows subsequent electrochemical anodization to be modified in various ways. Here we describe how a low level of lattice amorphization induced by ion irradiation influences anodization. First, it superposes a chemical etching effect, which is observable at high fluences as a reduced height of a micromachined component. Second, at lower fluences, it greatly enhances electrochemical anodization by allowing a hole diffusion current to flow to the exposed surface. We present an anodization model, which explains all observed effects produced by light ions such as helium and heavy ions such as cesium over a wide range of fluences and irradiation geometries.

  20. Enhanced electrochemical etching of ion irradiated silicon by localized amorphization

    NASA Astrophysics Data System (ADS)

    Dang, Z. Y.; Breese, M. B. H.; Lin, Y.; Tok, E. S.; Vittone, E.

    2014-05-01

    A tailored distribution of ion induced defects in p-type silicon allows subsequent electrochemical anodization to be modified in various ways. Here we describe how a low level of lattice amorphization induced by ion irradiation influences anodization. First, it superposes a chemical etching effect, which is observable at high fluences as a reduced height of a micromachined component. Second, at lower fluences, it greatly enhances electrochemical anodization by allowing a hole diffusion current to flow to the exposed surface. We present an anodization model, which explains all observed effects produced by light ions such as helium and heavy ions such as cesium over a wide range of fluences and irradiation geometries.

  1. Electrochemical nanoprobes for the chemical detection of neurotransmitters

    PubMed Central

    Colombo, Michelle L.

    2015-01-01

    Neurotransmitters, acting as chemical messengers, play an important role in neurotransmission, which governs many functional aspects of nervous system activity. Electrochemical probes have proven a very useful technique to study neurotransmission, especially to quantify and qualify neurotransmitters. With the emerging interests in probing neurotransmission at the level of single cells, single vesicles, as well as single synapses, probes that enable detection of neurotransmitters at the nanometer scale become vitally important. Electrochemical nanoprobes have been successfully employed in nanometer spatial resolution imaging of single nanopores of Si membrane and single Au nanoparticles, providing both topographical and chemical information, thus holding great promise for nanometer spatial study of neurotransmission. Here we present the current state of electrochemical nanoprobes for chemical detection of neurotransmitters, focusing on two types of nanoelectrodes, i.e. carbon nanoelectrode and nano-ITIES pipet electrode. PMID:26327927

  2. Nanogold/mesoporous carbon foam-mediated silver enhancement for graphene-enhanced electrochemical immunosensing of carcinoembryonic antigen.

    PubMed

    Lin, Dajie; Wu, Jie; Ju, Huangxian; Yan, Feng

    2014-02-15

    Nanogold functionalized mesoporous carbon foam (Au/MCF) coupling with a signal amplification by C-Au synergistic silver enhancement was designed for sensitive electrochemical immunosensing of biomarker. The Au/MCF was prepared by in situ growth of nanogold on carboxylated MCF and used as a tracing tag to label signal antibody via the inherent interaction between protein and nanogold. The immunosensor was prepared by covalently immobilizing capture antibody on an electrochemically reduced graphene oxide/chitosan film modified glassy carbon electrode. Through a sandwich-type immunoreaction, Au/MCF tags were captured on the immunoconjugates to induce a silver deposition process. The electrochemical stripping signal of the deposited silver was used to monitor the immunoreaction. The Au/MCF-mediated silver enhancement along with the graphene-promoted electron transfer led to high detection sensitivity of carcinoembryonic antigen. Under optimal conditions, the proposed immunoassay method showed wide linear range from 0.05 pg mL(-1) to 1 ng mL(-1) and a detection limit down to 0.024 pg mL(-1). The newly designed amplification strategy holds great potential for ultrasensitive electrochemical biosensing of other analytes.

  3. A mediator embedded micro-immunosensing unit for electrochemical detection on viruses within physiological saline media

    NASA Astrophysics Data System (ADS)

    Pires, Nuno M. M.; Dong, Tao; Yang, Zhaochu; Høivik, Nils; Zhao, Xinyan

    2011-11-01

    To provide a time- and cost-saving alternative to the conventional methods for virus detection in biological media, this work presents an electrochemical micro-immunosensor based on the nickel hexacyanoferrate (NiHCF) redox mediator film coating the interdigitated microelectrodes (IDMEs). By chelation binding with no additional cross-linker, the 6xHis-tagged antibodies were immobilized on a NiHCF film. Secondly, an immunoassay response was enhanced by employing microbeads coated with 6xHis antibody. The electrochemical properties and the stability of the NiHCF film modified IDMEs were evaluated by cyclic voltammetry. The bead-induced impedance variations at the electrode film/electrolyte interface were characterized by electrochemical impedance spectroscopy and verified using FEM simulation. Experiments of virus detection were conducted through targeting the antigens of the vital infectious salmon viruses, such as infectious salmon anaemia virus, infectious pancreatic necrosis virus and salmonid alphavirus subtype 3. The micro-immunosensor exhibited detection limits as low as 10 pg ml-1 and detection sensitivities as high as 57.5 kΩ µM-1 within a physiological saline solution. Tests for multiple antigen-antibody interactions showed good detection specificity, as confirmed by ELISA. By incorporating the microfluidic network, electrochemical impedance micro-immunosensing units can be realized in a fully integrated platform for multiplex virus detection in tissue samples.

  4. Electrochemical Processes Enhanced by Acoustic Liquid Manipulation

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C.

    2004-01-01

    Acoustic liquid manipulation is a family of techniques that employ the nonlinear acoustic effects of acoustic radiation pressure and acoustic streaming to manipulate the behavior of liquids. Researchers at the NASA Glenn Research Center are exploring new methods of manipulating liquids for a variety of space applications, and we have found that acoustic techniques may also be used in the normal Earth gravity environment to enhance the performance of existing fluid processes. Working in concert with the NASA Commercial Technology Office, the Great Lakes Industrial Technology Center, and Alchemitron Corporation (Elgin, IL), researchers at Glenn have applied nonlinear acoustic principles to industrial applications. Collaborating with Alchemitron Corporation, we have adapted the devices to create acoustic streaming in a conventional electroplating process.

  5. Ionic liquid-graphene hybrid nanosheets as an enhanced material for electrochemical determination of trinitrotoluene.

    PubMed

    Guo, Shaojun; Wen, Dan; Zhai, Yueming; Dong, Shaojun; Wang, Erkang

    2011-04-15

    Trinitrotoluene, usually known as TNT, is a kind of chemical explosive with hazardous and toxic effects on the environment and human health. Ever-increasing needs for a secure society and green environment essentially require the detection of TNT with rapidity, high sensitivity and low cost. In this article, ionic liquid-graphene hybrid nanosheets (IL-GNs) have been used as an enhanced material for rapidly electrochemical detection of trinitrotoluene (TNT). IL-GNs were characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray photo-electron spectroscopy, electrochemical impedance spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy, which confirmed that IL has been effectively functionalized on the surface of GNs. Significantly, IL-GNs modified glassy carbon electrode (GCE) showed 6.2 and 51.4-folds higher current signals for TNT reduction than IL-CNTs/GCE and bare GCE, respectively. Adsorptive stripping voltammetry (ASV) for the detection of TNT on IL-GNs exhibited a good linear range from 0.03 to 1.5 ppm with a detection limit of 4 ppb on the basis of the signal-to-noise characteristics (S/N=3). Moreover, IL-GNs/GCE exhibited good stability and reproducibility for the detection of TNT. And, IL-GNs based electrochemical detection platform was also successfully demonstrated for the detection of TNT in ground water, tap water, and lake water with satisfactory results.

  6. Ionic liquid-graphene hybrid nanosheets as an enhanced material for electrochemical determination of trinitrotoluene.

    PubMed

    Guo, Shaojun; Wen, Dan; Zhai, Yueming; Dong, Shaojun; Wang, Erkang

    2011-04-15

    Trinitrotoluene, usually known as TNT, is a kind of chemical explosive with hazardous and toxic effects on the environment and human health. Ever-increasing needs for a secure society and green environment essentially require the detection of TNT with rapidity, high sensitivity and low cost. In this article, ionic liquid-graphene hybrid nanosheets (IL-GNs) have been used as an enhanced material for rapidly electrochemical detection of trinitrotoluene (TNT). IL-GNs were characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray photo-electron spectroscopy, electrochemical impedance spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy, which confirmed that IL has been effectively functionalized on the surface of GNs. Significantly, IL-GNs modified glassy carbon electrode (GCE) showed 6.2 and 51.4-folds higher current signals for TNT reduction than IL-CNTs/GCE and bare GCE, respectively. Adsorptive stripping voltammetry (ASV) for the detection of TNT on IL-GNs exhibited a good linear range from 0.03 to 1.5 ppm with a detection limit of 4 ppb on the basis of the signal-to-noise characteristics (S/N=3). Moreover, IL-GNs/GCE exhibited good stability and reproducibility for the detection of TNT. And, IL-GNs based electrochemical detection platform was also successfully demonstrated for the detection of TNT in ground water, tap water, and lake water with satisfactory results. PMID:21333522

  7. Electrochemical immunosensors for Salmonella detection in food

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pathogen detection is a critical point for the identification and the prevention of problems related to food safety. Failures at detecting contaminations in food may cause outbreaks with drastic consequences to public health. In spite of the real need for obtaining analytical results in the shortest...

  8. Microfluidic devices with thick-film electrochemical detection

    DOEpatents

    Wang, Joseph; Tian, Baomin; Sahlin, Eskil

    2005-04-12

    An apparatus for conducting a microfluidic process and analysis, including at least one elongated microfluidic channel, fluidic transport means for transport of fluids through the microfluidic channel, and at least one thick-film electrode in fluidic connection with the outlet end of the microfluidic channel. The present invention includes an integrated on-chip combination reaction, separation and thick-film electrochemical detection microsystem, for use in detection of a wide range of analytes, and methods for the use thereof.

  9. Microchip Capillary Electrophoresis with Electrochemical Detection for Monitoring Environmental Pollutants

    SciTech Connect

    Chen, Gang; Lin, Yuehe; Wang, Joseph

    2006-01-15

    This invited paper reviews recent advances and the key strategies in microchip capillary electrophoresis (CE) with electrochemical detection (ECD) for separating and detecting a variety of environmental pollutants. The subjects covered include the fabrication of microfluidic chips, sample pretreatments, ECD, typical applications of microchip CE with ECD in environmental analysis, and future prospects. It is expected that microchip CE-ECD will become a powerful tool in the environmental field and will lead to the creation of truly portable devices.

  10. Nanomaterials and biomaterials in electrochemical arrays for protein detection

    PubMed Central

    Rusling, James F.; Bishop, Gregory W.; Doan, Nhi; Papadimitrakopoulos, Fotios

    2013-01-01

    Nanomaterials and biomaterials are important components of new electrochemical arrays designed for sensitive detection of proteins in biological fluids. Such multiplexed protein arrays are predicted to have an important future in personalized medical diagnostics, especially for cancer and heart disease. Sandwich immunoassays for proteins benefit greatly in sensitivity from the use of nanostructured sensor surfaces and multilabeled detection strategies involving nano- or microparticles. In these assays, capture agents such as antibodies or aptamers are attached to sensor surfaces in the array. Target proteins with large binding constants for the affinity agents are captured from liquid samples with high efficiency, either on the sensors or on magnetic bioconjugate particles decorated with many copies of labels and antibodies. After target proteins are captured on the sensor surfaces, the labels are detected by electrochemical techniques. This feature article begins with an overview of the recent history of nanoparticles in electrochemical protein sensors, then moves on to specific examples from our own laboratories. We discuss fabrication of nanostructured sensors and arrays with the aim of multiplexed detection as well as reusability. Following this, we describe systems that integrate particle-based protein sensing with microfluidics for multiplexed protein detection. We end with predictions on the diagnostic future of protein detection. PMID:24392222

  11. A novel electrochemical detection method for aptamer biosensors.

    PubMed

    Bang, Gyeong Sook; Cho, Suhyeong; Kim, Byung-Gee

    2005-12-15

    A beacon aptamer-based biosensor for the detection of thrombin was developed using electrochemical transduction method. Gold surface was modified with a beacon aptamer covalently linked at 5'-terminus with a linker containing a primary aliphatic amine. Methylene blue (MB) was intercalated into the beacon sequence, and used as an electrochemical marker. When the beacon aptamer immobilized on gold surface encounters thrombin, the hairpin forming beacon aptamer is conformationally changed to release the intercalated MB, resulting a decrease in electrical current intensity in voltamogram. The peak signal of the MB is clearly decreased by the binding of thrombin onto the beacon aptamer. The linear range of the signal was observed between 0 and 50.8 nM of thrombin with 0.999 correlation factor. This method was able to linearly and selectively detect thrombin with a detection limit of 11 nM.

  12. Detection of Escherichia coli in meat with an electrochemical biochip.

    PubMed

    Heidenreich, Bernd; Pöhlmann, Christopher; Sprinzl, Mathias; Gareis, Manfred

    2010-11-01

    Detection of foodborne pathogenic and spoilage bacteria by RNA-DNA hybridization is an alternative to traditional microbiological procedures. To achieve high sensitivity with RNA-DNA-based methods, efficient bacterial lysis and release of nucleic acids from bacteria are needed. Here we report the specific detection of the hygiene indicator microorganism Escherichia coli in meat by use of electrochemical biochips. We improved RNA isolation from bacteria in meat juice from pork and beef. Samples, either naturally or artificially contaminated by E. coli, were enriched by incubation in full or minimal medium. A combined treatment of the samples with lysozyme, proteinase K, and sonication resulted in efficient cell disruption and high total RNA yields. Together with optimization of enrichment time, this ensures high sensitivity of electrochemical measurements on biochips. A short enrichment period and the triple-lysis regimen in combination with electrochemical biochip measurement were tested with 25 meat samples. The lower limit of detection of the biochip was approximately 2,000 CFU of E. coli per ml. The entire analysis procedure (5 h of enrichment, triple lysis, and biochip detection) has a lower limit of detection of 1 CFU of E. coli per ml within a total time needed for analysis of 7 h.

  13. Detection of Salmonella typhimurium using an electrochemical immunosensor.

    PubMed

    Salam, Faridah; Tothill, Ibtisam E

    2009-04-15

    An electrochemical immunosensor based on screen-printed gold working electrode with onboard carbon counter and silver-silver chloride pseudo-reference electrode for Salmonella typhimurium detection is described in this paper. Monoclonal anti-S. typhimurium antibody was immobilized using physical and covalent immobilization via amine coupling of carboxymethyldextran on the surface of the gold working electrode. A direct sandwich enzyme-linked immunosorbent assays (ELISA) format was then developed and optimized using a polyclonal anti-Salmonella antibodies conjugated to horseradish peroxidase (HRP) as the enzyme label. 3,3',5,5'-Tetramethylbenzidine dihydrochloride (TMB)/H(2)O(2) was used as the enzyme mediator/substrate system. Electrochemical detection was conducted using chronoamperometry at -200 mV vs. onboard screen-printed Ag-AgCl pseudo-reference electrode. The applied potential was selected through the study of the electrochemical behaviour of bare gold electrode with TMB-H(2)O(2)-IgG-HRP system. S. typhimurium detection of 5x10(3) cells ml(-1) and approximately 20 cells ml(-1) was achieved respectively for physical and covalent antibody immobilization. The developed sensor was then compared to a commercial ELISA kit and a chromogenic agar plating method for meat samples analysis. The sensor format shows a promising technology for simple and sensitive detection system for Salmonella contamination. Rapid detection of Salmonella is a key to the prevention and identification of problems related to health and safety.

  14. Electrochemical aptasensor for lung cancer-related protein detection in crude blood plasma samples

    PubMed Central

    Zamay, Galina S.; Zamay, Tatiana N.; Kolovskii, Vasilii A.; Shabanov, Alexandr V.; Glazyrin, Yury E.; Veprintsev, Dmitry V.; Krat, Alexey V.; Zamay, Sergey S.; Kolovskaya, Olga S.; Gargaun, Ana; Sokolov, Alexey E.; Modestov, Andrey A.; Artyukhov, Ivan P.; Chesnokov, Nikolay V.; Petrova, Marina M.; Berezovski, Maxim V.; Zamay, Anna S.

    2016-01-01

    The development of an aptamer-based electrochemical sensor for lung cancer detection is presented in this work. A highly specific DNA-aptamer, LC-18, selected to postoperative lung cancer tissues was immobilized onto a gold microelectrode and electrochemical measurements were performed in a solution containing the redox marker ferrocyanide/ferricyanide. The aptamer protein targets were harvested from blood plasma of lung cancer patients by using streptavidin paramagnetic beads and square wave voltammetry of the samples was performed at various concentrations. In order to enhance the sensitivity of the aptasensor, silica-coated iron oxide magnetic beads grafted with hydrophobic C8 and C4 alkyl groups were used in a sandwich detection approach. Addition of hydrophobic beads increased the detection limit by 100 times. The detection limit of the LC-18 aptasensor was enhanced by the beads to 0.023 ng/mL. The formation of the aptamer – protein – bead sandwich on the electrode surface was visualized by electron microcopy. As a result, the electrochemical aptasensor was able to detect cancer-related targets in crude blood plasma of lung cancer patients. PMID:27694916

  15. Signal-on electrochemical Y or junction probe detection of nucleic acid.

    PubMed

    Shen, Zuliang; Nakayama, Shizuka; Semancik, Steve; Sintim, Herman O

    2012-08-01

    A methylene-blue (MB)-labeled molecular beacon junction probe allows for a signal-on electrochemical detection of nucleic acids via target recycling using endonucleases. Electron transfer is reduced when the MB is intercalated in the stem of the molecular beacon, but then electron transfer from MB to a gold electrode is enhanced upon cleavage of the junction probe due to increased probability of MB approaching the electrode when attached to the more flexible ssDNA.

  16. Facile electrochemical detection of botulinum neurotoxin type E using a two-step proteolytic cleavage.

    PubMed

    Park, Seonhwa; Shin, Yu Mi; Song, Ji-Joon; Yang, Haesik

    2015-10-15

    Facile electrochemical methods for measuring protease concentration or protease activity are essential for point-of-care testing of toxic proteases. However, electrochemical detection of proteases, such as botulinum neurotoxin type E (BoNT/E), that cleave a peptide bond between two specific amino acid residues is challenging. This study reports a facile and sensitive electrochemical method for BoNT/E detection. The method is based on a two-step proteolytic cleavage using a target BoNT/E light chain (BoNT/E-LC) and an externally supplemented exopeptidase, L-leucine-aminopeptidase (LAP). BoNT/E-LC cleaves a peptide bond between arginine and isoleucine in IDTQNRQIDRI-4-amino-1-naphthol (oligopeptide-AN) to generate isoleucine-AN. Subsequently, LAP cleaves a bond between isoleucine and AN to liberate a free electroactive AN species. The liberated AN participates in electrochemical-chemical-chemical (ECC) redox cycling involving Ru(NH3)6(3+), AN, and a reducing agent, which allows a high signal amplification. Electrochemical detection is carried out without surface modification of indium-tin oxide electrodes. We show that dithiothreitol is beneficial for enhancing the enzymatic activity of BoNT/E-LC and also for achieving a fast ECC redox cycling. An incubation temperature of 37°C and the use of phosphate buffered saline (PBS) buffer resulted in optimal signal-to-background ratios for efficient BoNT/E detection. BoNT/E-LC could be detected at concentrations of approximately 2.0 pg/mL, 0.2, and 3 ng/mL after 4h, 2h, and 15 min incubation in PBS buffer, respectively, and approximately 0.3 ng/mL after 2-h incubation in bottled water. The method developed could be applied in fast, sensitive, and selective detection of any protease that cleaves a peptide bond between two specific amino acid residues.

  17. A novel aptamer-based competition strategy for ultrasensitive electrochemical detection of leukemia cells.

    PubMed

    Zhang, Kui; Tan, Tingting; Fu, Jia-Ju; Zheng, Tingting; Zhu, Jun-Jie

    2013-11-01

    A robust, nanobiotechnology-based electrochemical cytosensing platform for the detection of acute leukemia cells was developed with high sensitivity, selectivity, acceptable rapidity and excellent extensibility. It utilized the competitive binding of cell-specific aptamers to acute leukemia cells and subsequent voltammetric quantification of the metal signature. Greatly enhanced sensitivity was achieved with dual signal amplification by using Fe3O4 magnetic nanoparticles (MNPs) as carriers to load a large amount of gold nanoparticles (AuNPs) and AuNP-catalyzed silver deposition. The proposed competitive cytosensor showed high sensitivity with a detection limit down to 10 cells. This simple and low-cost electrochemical cytosensing approach offers great promise to extend its application to early detection of human leukemia and possibly to other cancer cells.

  18. Electrochemical Proteolytic Beacon for Detection of Matrix Metalloproteinase Activities

    SciTech Connect

    Liu, Guodong; Wang, Jun; Wunschel, David S.; Lin, Yuehe

    2006-09-27

    This communication describes a novel method for detecting of matrix metalloproteinase-7 activity using a peptide substrate labeled with a ferrocene reporter. The substrate serves as a selective ‘electrochemical proteolytic beacon’ (EPB) for this metalloproteinase. The EPB is immobilized on a gold electrode surface to enable ‘on-off’ electrochemical signaling capability for uncleaved and cleaved events. The EPB is efficiently and selectively cleaved by MMP-7 as measured by the rate of decrease in redox current of ferrocene. Direct transduction of a signal corresponding to peptide cleavage events into an electronic signal thus provides a simple, sensitive route for detecting the MMP activity. The new method allows for identification of the activity of MMP-7 in concentrations as low as 3.4 pM. The concept can be extended to design multiple peptide substrate labeled with different electroactive reporters for assaying multiple MMPs activities.

  19. Electrochemical proteolytic beacon for detection of matrix metalloproteinase activities.

    PubMed

    Liu, Guodong; Wang, Jun; Wunschel, David S; Lin, Yuehe

    2006-09-27

    This communication describes a novel method for detecting matrix metalloproteinase-7 activity using a peptide substrate labeled with a ferrocene reporter. The substrate serves as a selective "electrochemical proteolytic beacon" (EPB) for this metalloproteinase. The EPB is immobilized on a gold electrode surface to enable "on-off" electrochemical signaling capability for uncleaved and cleaved events. The EPB is efficiently and selectively cleaved by MMP-7 as measured by the rate of decrease in redox current of ferrocene. Direct transduction of a signal corresponding to peptide cleavage events into an electronic signal thus provides a simple, sensitive route for detecting the MMP activity. The new method allows for identification of the activity of MMP-7 in concentrations as low as 3.4 pM. The concept can be extended to design a multiple peptide substrate labeled with different electroactive reporters for assaying multiple MMPs activities.

  20. Something from nothing: enhancing electrochemical charge storage with cation vacancies.

    PubMed

    Hahn, Benjamin P; Long, Jeffrey W; Rolison, Debra R

    2013-05-21

    The performance of electrochemical energy storage devices (e.g., batteries and electrochemical capacitors) is largely determined by the physicochemical properties of the active electrode materials, such as the thermodynamic potential associated with the charge-storage reaction, ion-storage capacity, and long-term electrochemical stability. In the case of mixed ion/electron-conducting metal oxides that undergo cation-insertion reactions, the presence of cation vacancies in the lattice structure can enhance one or more of these technical parameters without resorting to a drastic change in material composition. Examples of this enhancement include the charge-storage properties of certain cation-deficient oxides such as γ-MnO2 and γ-Fe2O3 relative to their defect-free analogues. The optimal cation-vacancy fraction is both material- and application-dependent because cation vacancies enhance some materials properties at the expense of others, potentially affecting electronic conductivity or thermal stability. Although the advantages of structural cation vacancies have been known since at least the mid-1980s, only a handful of research groups have purposefully integrated cation vacancies into active electrode materials to enhance device performance. Three protocols are available for the incorporation of cation vacancies into transition metal oxides to improve performance in both aqueous and nonaqueous energy storage. Through a processing approach, researchers induce point defects in conventional oxides using traditional solid-state-ionics techniques that treat the oxide under appropriate atmospheric conditions with a driving force such as temperature. In a synthetic approach, substitutional doping of a highly oxidized cation into a metal-oxide framework can significantly increase cation-vacancy content and corresponding charge-storage capacity. In a scaling approach, electrode materials that are expressed in morphologies with high surface areas, such as aerogels

  1. Monitoring environmental pollutants by microchip capillary electrophoresis with electrochemical detection

    SciTech Connect

    Chen, Gang; Lin, Yuehe; Wang, Joseph

    2006-01-15

    This is a review article. During the past decade, significant progress in the development of miniaturized microfluidic systems has Occurred due to the numerous advantages of microchip analysis. This review focuses on recent advances and the key strategies in microchip capillary electrophoresis (CE) with electrochemical detection (ECD) for separating and detecting a variety of environmental pollutants. The subjects covered include the fabrication of microfluidic chips, ECD, typical applications of microchip CE with ECD in environmental analysis, and future prospects. It is expected that microchip CE-ECD will become a powerful tool in the environmental field and will lead to the creation of truly portable devices.

  2. Microchip-based electrochemical detection for monitoring cellular systems.

    PubMed

    Johnson, Alicia S; Selimovic, Asmira; Martin, R Scott

    2013-04-01

    The use of microchip devices to study cellular systems is a rapidly growing research area. There are numerous advantages of using on-chip integrated electrodes to monitor various cellular processes. The purpose of this review is to give examples of advancements in microchip-based cellular analysis, specifically where electrochemistry is used for the detection scheme. These examples include on-chip detection of single-cell quantal exocytosis, electrochemical analysis of intracellular contents, the ability to integrate cell culture/immobilization with electrochemistry, and the use of integrated electrodes to ensure cell confluency in longer-term cell culture experiments. A perspective on future trends in this area is also given.

  3. Screen Printed Carbon Electrode Based Electrochemical Immunosensor for the Detection of Dengue NS1 Antigen

    PubMed Central

    Parkash, Om; Yean Yean, Chan; Hanim Shueb, Rafidah

    2014-01-01

    An electrochemical immunosensor modified with the streptavidin/biotin system on screen printed carbon electrodes (SPCEs) for the detection of the dengue NS1 antigen was developed in this study. Monoclonal anti-NS1 capture antibody was immobilized on streptavidin-modified SPCEs to increase the sensitivity of the assay. Subsequently, a direct sandwich enzyme linked immunosorbent assay (ELISA) format was developed and optimized. An anti-NS1 detection antibody conjugated with horseradish peroxidase enzyme (HRP) and 3,3,5,5'-tetramethybezidine dihydrochloride (TMB/H2O2) was used as an enzyme mediator. Electrochemical detection was conducted using the chronoamperometric technique, and electrochemical responses were generated at −200 mV reduction potential. The calibration curve of the immunosensor showed a linear response between 0.5 µg/mL and 2 µg/mL and a detection limit of 0.03 µg/mL. Incorporation of a streptavidin/biotin system resulted in a well-oriented antibody immobilization of the capture antibody and consequently enhanced the sensitivity of the assay. In conclusion, this immunosensor is a promising technology for the rapid and convenient detection of acute dengue infection in real serum samples. PMID:26852684

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

    PubMed

    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.

  5. Hybrid carbon nanomaterials for electrochemical detection of biomolecules

    NASA Astrophysics Data System (ADS)

    Laurila, Tomi

    2015-09-01

    Electrochemical detection of different biomolecules in vivo is a promising path towards in situ monitoring of human body and its functions. However, there are several major obstacles, such as sensitivity, selectivity and biocompatiblity, which must be tackled in order to achieve reliably and safely operating sensor devices. Here we show that by utilizing hybrid carbon materials as electrodes to detect two types of neurotransmitters, dopamine and glutamate, several advantages over commonly used electrode materials can be achieved. In particular, we will demonstrate here that it is possible to combine the properties of different carbon allotropes to obtain hybrid materials with greatly improved electrochemical performance. Three following examples of the approach are given: (i) diamond-like carbon (DLC) thin film electrodes with different layer thicknesses, (ii) multi-walled carbon nanotubes grown directly on top of DLC and (iii) carbon nanofibres synthesized on top of DLC thin films. Detailed structural and electrochemical characterization is carried out to rationalize the reasons behind the observed behvior. In addition, results from the atomistic simulations are utilized to obtain more information about the properties of the amorphous carbon thin films.

  6. Highly sensitive electrochemical biosensor based on nonlinear hybridization chain reaction for DNA detection.

    PubMed

    Jia, Liping; Shi, Shanshan; Ma, Rongna; Jia, Wenli; Wang, Huaisheng

    2016-06-15

    In the present work we demonstrated an ultrasensitive detection platform for specific DNA based on nonlinear hybridization chain reaction (HCR) by triggering chain-branching growth of DNA dendrimers. HCR was initiated by target DNA (tDNA) and finally formed dendritic structure by self-assembly. The electrochemical signal was drastically enhanced by capturing multiple catalytic peroxidase with high-ordered growth. Electrochemical signals were obtained by measuring the reduction current of oxidized 3, 3', 5, 5'-tetramethylbenzidine sulfate (TMB), which was generated by HRP in the presence of H2O2. This method exhibited ultrahigh sensitivity to tDNA with detection limit of 0.4 fM. Furthermore, the biosensor was also capable of discriminating single-nucleotide difference among concomitant DNA sequences.

  7. Superhydrophobic Surface Enhanced Raman Scattering Sensing using Janus Particle Arrays Realized by Site-Specific Electrochemical Growth

    PubMed Central

    Hricko, Patrick John; Huang, Po-Hsun; Li, Sixing; Zhao, Yanhui; Xie, Yuliang; Guo, Feng; Wang, Lin

    2014-01-01

    Site-specific electrochemical deposition is used to prepare polystyrene (PS)-Ag Janus particle arrays with superhydrophobic properties. The analyte molecules can be significantly enriched using the superhydrophobic property of the PS-Ag Janus particle array before SERS detections, enabling an extremely sensitive detection of molecules in a highly diluted solution (e.g., femtomolar level). This superhydrophobic surface enhanced Raman scattering sensing concept described here is of critical significance in biosensing and bioanalysis. Most importantly, the site-specific electrochemical growth method we developed here is a versatile approach that can be used to prepare Janus particle arrays with different properties for various applications. PMID:24748991

  8. Electrochemical sensors based on carbon nanomaterials for acetaminophen detection: A review.

    PubMed

    Cernat, Andreea; Tertiş, Mihaela; Săndulescu, Robert; Bedioui, Fethi; Cristea, Alexandru; Cristea, Cecilia

    2015-07-30

    This study describes the advancements made over the last five years in the development of electrochemical sensors and biosensors for acetaminophen detection. This study reviews the different configurations based on unmodified and chemically modified carbon nanotubes and graphene. The influence of various modifiers on the two types of materials is presented along with their role on the enhancement of the selectivity and sensitivity of (bio)sensors. The review is focused on a comparative description of the applications of carbon-based nanomaterials towards acetaminophen detection and presents the results in a critical manner.

  9. Botulinum Neurotoxin Serotypes Detected by Electrochemical Impedance Spectroscopy

    PubMed Central

    Savage, Alison C.; Buckley, Nicholas; Halliwell, Jennifer; Gwenin, Christopher

    2015-01-01

    Botulinum neurotoxin is one of the deadliest biological toxins known to mankind and is able to cause the debilitating disease botulism. The rapid detection of the different serotypes of botulinum neurotoxin is essential for both diagnosis of botulism and identifying the presence of toxin in potential cases of terrorism and food contamination. The modes of action of botulinum neurotoxins are well-established in literature and differ for each serotype. The toxins are known to specifically cleave portions of the SNARE proteins SNAP-25 or VAMP; an interaction that can be monitored by electrochemical impedance spectroscopy. This study presents a SNAP-25 and a VAMP biosensors for detecting the activity of five botulinum neurotoxin serotypes (A–E) using electrochemical impedance spectroscopy. The biosensors are able to detect concentrations of toxins as low as 25 fg/mL, in a short time-frame compared with the current standard methods of detection. Both biosensors show greater specificity for their compatible serotypes compared with incompatible serotypes and denatured toxins. PMID:25954998

  10. Aptamer-based electrochemical biosensor for interferon gamma detection.

    PubMed

    Liu, Ying; Tuleouva, Nazgul; Ramanculov, Erlan; Revzin, Alexander

    2010-10-01

    In this paper, we describe the development of an electrochemical DNA aptamer-based biosensor for detection of interferon (IFN)-γ. A DNA hairpin containing IFN-γ-binding aptamer was thiolated, conjugated with methylene blue (MB) redox tag, and immobilized on a gold electrode by self-assembly. Binding of IFN-γ caused the aptamer hairpin to unfold, pushing MB redox molecules away from the electrode and decreasing electron-transfer efficiency. The change in redox current was quantified using square wave voltammetry (SWV) and was found to be highly sensitive to IFN-γ concentration. The limit of detection for optimized biosensor was 0.06 nM with linear response extending to 10 nM. This aptasensor was specific to IFN-γ in the presence of overabundant serum proteins. Importantly, the same aptasensor could be regenerated by disrupting aptamer-IFN-γ complex in urea buffer and reused multiple times. Unlike standard sandwich immunoassays, the aptasensor described here allowed one to detect IFN-γ binding directly without the need for multiple washing steps and reagents. An electrochemical biosensor for simple and sensitive detection of IFN-γ demonstrated in this paper will have future applications in immunology, cancer research, and infectious disease monitoring.

  11. Saturated saline enhances the effect of electrochemical therapy.

    PubMed

    Lin, X Z; Jen, C M; Chou, C K; Chou, C S; Sung, M J; Chou, T C

    2000-03-01

    We conducted this experiment to assess the effect of saline injection in electrochemical therapy. Platinum electrodes using direct current were inserted into egg white or liver parenchyma. Pure water or 0.9%, 3%, or 26% sodium chloride were injected into various objects to compare with the control group (no injection). Power was set at 10 V. In the egg-white experiment, gas bubbles and coagulated protein developed around the electrodes. In ex vivo liver, frothy reddish debris developed around the cathodes, while a hardening and shrunken surface occurred around the anodes. The pH was 14 around the cathodes, 0 around the anodes. The electric current, the amount of coagulated protein, and the severity of tissue damage were all in proportion to the concentrations of the injected saline. The volume destroyed in the 26% saline group was 8.1 times larger than that of the control group. Therefore, injected saline, especially saturated saline, can enhance the effect of electrochemical therapy.

  12. [Electrochemical detection of toxin gene in Listeria monocytogenes].

    PubMed

    Wu, Ling-Wei; Liu, Quan-Jun; Wu, Zhong-Wei; Lu, Zu-Hong

    2010-05-01

    Listeria monocytogenes (LM) is a food-borne pathogen inducing listeriosis, an illness characterized by encephalitis, septicaemia, and meningitis. Listeriolysin O (LLO) is absolutely required for virulence by L. monocytogenes, and is found only in virulent strains of the species. One of the best ways to detect and confirm the pathogen is detection of one of the virulence factors, LLO, produced by the microorganism. This paper focused on the electrical method used to detect the LLO toxin gene in food products and organism without labeling the target DNA. The electrochemical sensor was obtained by immobilizing single-stranded oligonucleotides onto the gold electrode with the mercaptan activated by N-hydroxysulfosuccinimide (NHS) and N-(3-dimethylamion)propyl-N'-ethyl carbodiimidehydrochloride (EDC). The hy-bridization reaction that occurred on the electrode surface was evidenced by Cyclic Voltammetry (CV) analysis using [Co(phen)3](ClO4)3 as an indicator. The covalently immobilized single-stranded DNA could selectively hybridize to its complementary DNA in solution to form double-stranded DNA on the gold surface. A significant increase of the peak cur-rent of Cyclic Voltammetry (CV) upon hybridization of immobilized ssDNA with PCR amplification products in the solu-tion was observed. This peak current change was used to monitor the amount of PCR amplification products. Factors deter-mining the sensitivity of the electrochemical assay, such as DNA target concentration and hybridization conditions, were investigated. The coupling of DNA to the electrochemical sensors has the potential of the quantitative evaluation of gene.

  13. Dual enzyme electrochemical coding for detecting DNA hybridization.

    PubMed

    Wang, Joseph; Kawde, Abdel-Nasser; Musameh, Mustafa; Rivas, Gustavo

    2002-10-01

    Enzyme-based hybridization assays for the simultaneous electrochemical measurements of two DNA targets are described. Two encoding enzymes, alkaline phosphatase and beta-galactosidase, are used to differentiate the signals of two DNA targets in connection to chronopotentiometric measurements of their electroactive phenol and alpha-naphthol products. These products yield well-defined and resolved peaks at +0.31 V (alpha-naphthol) and +0.63 V (phenol) at the graphite working electrode (vs. Ag/AgCl reference). The position and size of these peaks reflect the identity and level of the corresponding target. The dual target detection capability is coupled to the amplification feature of enzyme tags (to yield fmol detection limits) and with an efficient magnetic removal of non-hybridized nucleic acids. Proper attention is given to the choice of the substrates (for attaining well resolved peaks), to the activity of the enzymes (for obtaining similar sensitivities), and to the selection of the enzymes (for minimizing cross interferences). The new bioassay is illustrated for the simultaneous detection of two DNA sequences related to the BCRA1 breast-cancer gene in a single sample in connection to magnetic beads bearing the corresponding oligonucleotide probes. Prospects for electrochemical coding of multiple DNA targets are discussed.

  14. DNA-Redox Cation Interaction Improves the Sensitivity of an Electrochemical Immunosensor for Protein Detection.

    PubMed

    Li, Ping; Ge, Bixia; Ou, Lily M-L; Yao, Zhihui; Yu, Hua-Zhong

    2015-08-20

    A simple DNA-redox cation interaction enhancement strategy has been developed to improve the sensitivity of electrochemical immunosensors for protein detection. Instead of labeling with fluorophores or redox-active groups, the detection antibodies were tethered with DNA single strands. Based on the electrostatic interaction between redox cations ([Ru(NH3)6](3+)) and negatively charged DNA backbone, enhanced electrochemical signals were obtained. Human chorionic gonadotropin (hCG) detection has been performed as a trial analysis. A linear response range up to the concentration of 25 mIU/mL and a detection limit of 1.25 mIU/mL have been achieved, both are comparable with the ultrasensitive enzyme-linked immunosorbent assay (ELISA) tests. The method also shows great selectivity towards hCG over other hormones such as thyroid stimulating hormone (TSH) and follicle stimulating hormone (FSH). By and large, our approach bears the merits of cost effectiveness and simplicity of instrumentation in comparison with conventional optical detection methods.

  15. DNA-Redox Cation Interaction Improves the Sensitivity of an Electrochemical Immunosensor for Protein Detection

    PubMed Central

    Li, Ping; Ge, Bixia; Ou, Lily M.-L.; Yao, Zhihui; Yu, Hua-Zhong

    2015-01-01

    A simple DNA-redox cation interaction enhancement strategy has been developed to improve the sensitivity of electrochemical immunosensors for protein detection. Instead of labeling with fluorophores or redox-active groups, the detection antibodies were tethered with DNA single strands. Based on the electrostatic interaction between redox cations ([Ru(NH3)6]3+) and negatively charged DNA backbone, enhanced electrochemical signals were obtained. Human chorionic gonadotropin (hCG) detection has been performed as a trial analysis. A linear response range up to the concentration of 25 mIU/mL and a detection limit of 1.25 mIU/mL have been achieved, both are comparable with the ultrasensitive enzyme-linked immunosorbent assay (ELISA) tests. The method also shows great selectivity towards hCG over other hormones such as thyroid stimulating hormone (TSH) and follicle stimulating hormone (FSH). By and large, our approach bears the merits of cost effectiveness and simplicity of instrumentation in comparison with conventional optical detection methods. PMID:26307986

  16. An electrochemical immunosensor for quantitative detection of ficolin-3

    NASA Astrophysics Data System (ADS)

    San, Lili; Zeng, Dongdong; Song, Shiping; Zuo, Xiaolei; Zhang, Huan; Wang, Chenguang; Wu, Jiarui; Mi, Xianqiang

    2016-06-01

    Diabetes mellitus (DM) is one of the most common metabolic disorders in the world, of which more than 90% is type-2 diabetes mellitus (T2DM). There is a rather urgent need for reliable, sensitive and quick detection techniques in clinical application of T2DM. Ficolin-3 is a potential biomarker of T2DM, because serum ficolin-3 levels are associated with insulin resistance and predict the incidence of T2DM. Herein, a sandwich-type electrochemical immunosensor was developed for the detection of ficolin-3 in human serum. Cyclic voltammetry and the amperometric current versus time were used to characterize the performance of the immunosensor. Under optimal conditions, the detection limitation of ficolin-3 was 100 ng ml–1 and the linear dynamic range was between 2 and 50 μg ml–1. The method has ideal accuracy, excellent stability and selectivity and has wide application prospects in clinical research.

  17. Electrochemical Detection of Hydrazine Using Poly(dopamine)-Modified Electrodes

    PubMed Central

    Lee, Ji Young; Nguyen, Truc Ly; Park, Jun Hui; Kim, Byung-Kwon

    2016-01-01

    We have developed a simple and selective method for the electrochemical detection of hydrazine (HZ) using poly(dopamine) (pDA)-modified indium tin oxide (ITO) electrodes. Modification with pDA was easily achieved by submerging the ITO electrode in a DA solution for 30 min. The electrocatalytic oxidation of HZ on the pDA-modified ITO electrode was measured by cyclic voltammetry. In buffer solution, the concentration range for linear HZ detection was 100 µM–10 mM, and the detection limit was 1 µM. The proposed method was finally used to determine HZ in tap water to simulate the analysis of real samples. This method showed good recovery (94%–115%) and was not affected by the other species present in the tap water samples. PMID:27164108

  18. An electrochemical immunosensor for quantitative detection of ficolin-3

    NASA Astrophysics Data System (ADS)

    San, Lili; Zeng, Dongdong; Song, Shiping; Zuo, Xiaolei; Zhang, Huan; Wang, Chenguang; Wu, Jiarui; Mi, Xianqiang

    2016-06-01

    Diabetes mellitus (DM) is one of the most common metabolic disorders in the world, of which more than 90% is type-2 diabetes mellitus (T2DM). There is a rather urgent need for reliable, sensitive and quick detection techniques in clinical application of T2DM. Ficolin-3 is a potential biomarker of T2DM, because serum ficolin-3 levels are associated with insulin resistance and predict the incidence of T2DM. Herein, a sandwich-type electrochemical immunosensor was developed for the detection of ficolin-3 in human serum. Cyclic voltammetry and the amperometric current versus time were used to characterize the performance of the immunosensor. Under optimal conditions, the detection limitation of ficolin-3 was 100 ng ml-1 and the linear dynamic range was between 2 and 50 μg ml-1. The method has ideal accuracy, excellent stability and selectivity and has wide application prospects in clinical research.

  19. Development of an electrochemical immunosensor for fumonisins detection in foods.

    PubMed

    Kadir, Mohamad Kamal Abdul; Tothill, Ibtisam E

    2010-04-01

    An electrochemical affinity sensor for the determination of fumonisins mycotoxins (Fms) using monoclonal antibody modified screen-printed gold electrode with carbon counter and silver-silver chloride pseudo-reference electrode is reported in this work. A direct competitive enzyme-linked immunosorbent assay (ELISA) was initially developed, exhibiting a detection limit of 100 µg·L(-1 )for fumonisins. This was then transferred to the surface of a bare gold screen-printed electrode (SPGE) and detection was performed by chronoamperometry, monitoring the reaction of 3,3',5,5'-Tetramethylbenzidine dihydrochloride (TMB) and hydrogen peroxide (H(2)O(2)) catalysed by HRP at -100 mV potential vs. onboard Ag-AgCl pseudo-reference electrode. The immunosensor exhibited detection limit of 5 µg·L(-1) fumonisins with a dynamic range from 1 µg·L(-1)-1000 µg·L(-1). The sensor also performed well in extracted corn samples.

  20. Plasma-Modified, Epitaxial Fabricated Graphene on SiC for the Electrochemical Detection of TNT

    PubMed Central

    Trammell, Scott A.; Hernández, Sandra C.; Myers-Ward, Rachael L.; Zabetakis, Daniel; Stenger, David A.; Gaskill, D. Kurt; Walton, Scott G.

    2016-01-01

    Using square wave voltammetry, we show an increase in the electrochemical detection of trinitrotoluene (TNT) with a working electrode constructed from plasma modified graphene on a SiC surface vs. unmodified graphene. The graphene surface was chemically modified using electron beam generated plasmas produced in oxygen or nitrogen containing backgrounds to introduce oxygen or nitrogen moieties. The use of this chemical modification route enabled enhancement of the electrochemical signal for TNT, with the oxygen treatment showing a more pronounced detection than the nitrogen treatment. For graphene modified with oxygen, the electrochemical response to TNT can be fit to a two-site Langmuir isotherm suggesting different sites on the graphene surface with different affinities for TNT. We estimate a limit of detection for TNT equal to 20 ppb based on the analytical standard S/N ratio of 3. In addition, this approach to sensor fabrication is inherently a high-throughput, high-volume process amenable to industrial applications. High quality epitaxial graphene is easily grown over large area SiC substrates, while plasma processing is a rapid approach to large area substrate processing. This combination facilitates low cost, mass production of sensors. PMID:27529251

  1. Electrochemical detection of Pseudomonas in wound exudate samples from patients with chronic wounds.

    PubMed

    Sismaet, Hunter J; Banerjee, Anirban; McNish, Sean; Choi, Yongwook; Torralba, Manolito; Lucas, Sarah; Chan, Agnes; Shanmugam, Victoria K; Goluch, Edgar D

    2016-03-01

    In clinical practice, point-of-care diagnostic testing has progressed rapidly in the last decade. For the field of wound care, there is a compelling need to develop rapid alternatives for bacterial identification in the clinical setting, where it generally takes over 24 hours to receive a positive identification. Even new molecular and biochemical identification methods require an initial incubation period of several hours to obtain a sufficient number of cells prior to performing the analysis. Here we report the use of an inexpensive, disposable electrochemical sensor to detect pyocyanin, a unique, redox-active quorum sensing molecule released by Pseudomonas aeruginosa, in wound fluid from patients with chronic wounds enrolled in the WE-HEAL Study. By measuring the metabolite excreted by the cells, this electrochemical detection strategy eliminates sample preparation, takes less than a minute to complete, and requires only 7.5 μL of sample to complete the analysis. The electrochemical results were compared against 16S rRNA profiling using 454 pyrosequencing. Blind identification yielded 9 correct matches, 2 false negatives, and 3 false positives giving a sensitivity of 71% and specificity of 57% for detection of Pseudomonas. Ongoing enhancement and development of this approach with a view to develop a rapid point-of-care diagnostic tool is planned. PMID:26815644

  2. Plasma-Modified, Epitaxial Fabricated Graphene on SiC for the Electrochemical Detection of TNT.

    PubMed

    Trammell, Scott A; Hernández, Sandra C; Myers-Ward, Rachael L; Zabetakis, Daniel; Stenger, David A; Gaskill, D Kurt; Walton, Scott G

    2016-01-01

    Using square wave voltammetry, we show an increase in the electrochemical detection of trinitrotoluene (TNT) with a working electrode constructed from plasma modified graphene on a SiC surface vs. unmodified graphene. The graphene surface was chemically modified using electron beam generated plasmas produced in oxygen or nitrogen containing backgrounds to introduce oxygen or nitrogen moieties. The use of this chemical modification route enabled enhancement of the electrochemical signal for TNT, with the oxygen treatment showing a more pronounced detection than the nitrogen treatment. For graphene modified with oxygen, the electrochemical response to TNT can be fit to a two-site Langmuir isotherm suggesting different sites on the graphene surface with different affinities for TNT. We estimate a limit of detection for TNT equal to 20 ppb based on the analytical standard S/N ratio of 3. In addition, this approach to sensor fabrication is inherently a high-throughput, high-volume process amenable to industrial applications. High quality epitaxial graphene is easily grown over large area SiC substrates, while plasma processing is a rapid approach to large area substrate processing. This combination facilitates low cost, mass production of sensors. PMID:27529251

  3. Electrochemical detection of nitromethane vapors combined with a solubilization device.

    PubMed

    Delile, Sébastien; Aussage, Adeline; Maillou, Thierry; Palmas, Pascal; Lair, Virginie; Cassir, Michel

    2015-01-01

    During the past decade, the number of terrorism acts has increased and the need for efficient explosive detectors has become an urgent worldwide necessity. A prototype, Nebulex™, was recently developed in our laboratory. Basically, it couples the solubilization of an analyte from the atmosphere by a nebulization process and in-situ detection. This article presents the development and integration of an electrochemical sensor for the detection of nitromethane, a common chemical product that can be used to make an improvised explosive device. A gold screen-printed electrode was used in a flow-cell and a detection limit of 4.5 µM was achieved by square wave voltammetry. The detection method was also determined to be selective toward nitromethane over a large panel of interfering compounds. Detection tests with the Nebulex™ were thus carried out using a custom-made calibrated nitromethane vapor generator. Detection times of less than one minute were obtained for nitromethane contents of 8 and 90 ppmv. Further measurements were performed in a room-measurement configuration leading to detection times in the range of 1-2 min, clearly demonstrating the system's efficiency under quasi-real conditions.

  4. Single Molecule Electrochemical Detection in Aqueous Solutions and Ionic Liquids.

    PubMed

    Byers, Joshua C; Paulose Nadappuram, Binoy; Perry, David; McKelvey, Kim; Colburn, Alex W; Unwin, Patrick R

    2015-10-20

    Single molecule electrochemical detection (SMED) is an extremely challenging aspect of electroanalytical chemistry, requiring unconventional electrochemical cells and measurements. Here, SMED is reported using a "quad-probe" (four-channel probe) pipet cell, fabricated by depositing carbon pyrolytically into two diagonally opposite barrels of a laser-pulled quartz quadruple-barreled pipet and filling the open channels with electrolyte solution, and quasi-reference counter electrodes. A meniscus forms at the end of the probe covering the two working electrodes and is brought into contact with a substrate working electrode surface. In this way, a nanogap cell is produced whereby the two carbon electrodes in the pipet can be used to promote redox cycling of an individual molecule with the substrate. Anticorrelated currents generated at the substrate and tip electrodes, at particular distances (typically tens of nanometers), are consistent with the detection of single molecules. The low background noise realized in this droplet format opens up new opportunities in single molecule electrochemistry, including the use of ionic liquids, as well as aqueous solution, and the quantitative assessment and analysis of factors influencing redox cycling currents, due to a precisely known gap size.

  5. An electrochemical immunosensing method for detecting melanoma cells.

    PubMed

    Seenivasan, Rajesh; Maddodi, Nityanand; Setaluri, Vijaysaradhi; Gunasekaran, Sundaram

    2015-06-15

    An electrochemical immunosensing method was developed to detect melanoma cells based on the affinity between cell surface melanocortin 1 receptor (MC1R) antigen and anti-MC1R antibody (MC1R-Ab). The MC1R-Abs were immobilized in amino-functionalized silica nanoparticles (n-SiNPs)-polypyrrole (PPy) nanocomposite modified on working electrode surface of screen-printed electrode (SPE). Cyclic voltammetry was employed, with the help of redox mediator ([Fe(CN)6](3-)), to measure the change in anodic oxidation peak current arising due to the specific interaction between MC1R antigens and MC1R-Abs when the target melanoma cells are present in the sample. Various factors affecting the sensor performance, such as the amount of MC1R-Abs loaded, incubation time with the target melanoma cells, the presence of interfering non-melanoma cells, were tested and optimized over different expected melanoma cell loads in the range of 50-7500 cells/2.5 mL. The immunosensor is highly sensitive (20 cells/mL), specific, and reproducible, and the antibody-loaded electrode in ready-to-use stage is stable over two weeks. Thus, in conjunction with a microfluidic lab-on-a-chip device our electrochemical immunosensing approach may be suitable for highly sensitive, selective, and rapid detection of circulating tumor cells (CTCs) in blood samples.

  6. An electrochemical immunosensing method for detecting melanoma cells

    PubMed Central

    Seenivasan, Rajesh; Maddodi, Nityanand; Setaluri, Vijaysaradhi; Gunasekaran, Sundaram

    2015-01-01

    An electrochemical immunosensing method was developed to detect melanoma cells based on the affinity between cell surface melanocortin 1 receptor (MC1R) antigen and anti-MC1R antibody (MC1R-Ab). The MC1R-Abs were immobilized in amino-functionalized silica nanoparticles (n-SiNPs)-polypyrrole (PPy) nanocomposite modified on working electrode surface of screen-printed electrode (SPE). Cyclic voltammetry was employed, with the help of redox mediator ([Fe(CN)6]3−), to measure the change in anodic oxidation peak current arising due to the specific interaction between MC1R antigens and MC1R-Abs when the target melanoma cells are present in the sample. Various factors affecting the sensor performance, such as the amount of MC1R-Abs loaded, incubation time with the target melanoma cells, the presence of interfering non-melanoma cells, were tested and optimized over different expected melanoma cell loads in the range of 50–7500 cells/2.5 mL. The immunosensor is highly sensitive (20 cells/mL), specific, and reproducible, and the antibody-loaded electrode in ready-to-use stage is stable over two weeks. Thus, in conjunction with a microfluidic lab-on-a-chip device our electrochemical immunosensing approach may be suitable for highly sensitive, selective, and rapid detection of circulating tumor cells (CTCs) in blood samples. PMID:25636023

  7. An Electrochemical DNA Biosensor for the Detection of Salmonella Using Polymeric Films and Electrochemical Labels

    NASA Astrophysics Data System (ADS)

    Diaz Serrano, Madeline

    Waterborne and foodborne diseases are one of the principal public health problems worldwide. Microorganisms are the major agents of foodborne illness: pathogens such as Salmonella, Campylobacter jejuni and Escherichia coli, and parasites such as cryptosporidium. The most popular methods to detect Salmonella are based on culture and colony counting methods, ELISA, Gel electrophoresis and the polymerase chain reaction. Conventional detection methods are laborious and time-consuming, allowing for portions of the food to be distributed, marketed, sold and eaten before the analysis is done and the problem even detected. By these reasons, the rapid, easy and portable detection of foodborne organisms will facilitate the disease treatment. Our particular interest is to develop a nucleic acid biosensor (NAB) for the detection of pathogenic microorganisms in food and water samples. In this research, we report on the development of a NAB prototype using a polymer modified electrode surface together with sequences of different lengths for the OmpC gene from Salmonella as probes and Ferrocene-labeled target (Fc-ssDNA), Ferrocene-labeled tri(ethylene glycol) (Fc-PEG) and Ruthenium-Ferrocene (Ru-Fe) bimetallic complex as an electrochemical labels. We have optimized several PS films and anchored nucleic acid sequences with different lengths at gold and carbon surfaces. Non contact mode AFM and XPS were used to monitor each step of the NAB preparation, from polymer modification to oligos hybridization (conventional design). The hybridization reaction was followed electrochemically using a Fc-ssDNA and Fc-PEG in solution taking advantage of the morphological changes generated upon hybridization. We observed a small current at the potential for the Fe oxidation without signal amplification at +296 mV vs. Ag/AgCl for the Fc-ssDNA strategy and a small current at +524 mV for the Fc-PEG strategy. The immobilization, hybridization and signal amplification of Biotin- OmpC Salmonella genes

  8. Microchip-based electrochemical detection for monitoring cellular systems

    PubMed Central

    Johnson, Alicia S.; Selimovic, Asmira; Martin, R. Scott

    2013-01-01

    The use of microchip devices to study cellular systems is a rapidly growing research area. There are numerous advantages of using on-chip integrated electrodes to monitor various cellular processes. The purpose of this review article is to give examples of advancements in microchip-based cellular analysis, specifically where electrochemistry is used for the detection scheme. These examples include on-chip detection of single cell quantal exocytosis, electrochemical analysis of intracellular contents, the ability to integrate cell culture/immobilization with electrochemistry, and the use of integrated electrodes to ensure cell confluency in longer term cell culture experiments. A perspective on future trends in this area is also given. PMID:23340999

  9. Transient Electrochemical Surface-Enhanced Raman Spectroscopy: A Millisecond Time-Resolved Study of an Electrochemical Redox Process.

    PubMed

    Zong, Cheng; Chen, Chan-Juan; Zhang, Meng; Wu, De-Yin; Ren, Bin

    2015-09-16

    The pursuit of techniques with a high time resolution together with molecular signature information at the electrochemical interfaces has never stopped in order to explicitly monitor and understand the dynamic electrochemical processes. Here, we developed a transient electrochemical surface-enhanced Raman spectroscopy (TEC-SERS) to monitor the structural evolution of surface species at a time resolution that equals the transient electrochemical methods (e.g., cyclic voltammetry and chronoamperometry), so that the Raman signal with the molecular signature information and the electrochemical current signal can be precisely correlated. The technique was employed to study the redox process of nile blue on Ag surfaces. We revealed an interesting two-rate constant process and a peculiar increase of the absolute intensity during the reduction of nile blue on the Ag surface, which both related to the dissociation of nile blue aggregates and the follow-up reduction. Therefore, we were able to uncover the processes that are impossible to observe by conventional steady state SERS methods. The ability to provide a time resolution shorter than the charging time of the double layer capacitance with molecular fingerprint information has unprecedented significance for investigation of both reversible and irreversible electrochemical processes.

  10. Liquid chromatography-photolysis-electrochemical detection for organoiodides. 1. Optimization and application

    SciTech Connect

    Selavka, C.M.; Krull, I.S.

    1987-11-15

    An improved high-performance liquid chromatographic detection method has been applied for the trace determination of iodinated organic compounds. The method, which incorporates postcolumn, on-line UV irradiation prior to oxidative electrochemical (EC) detection, exploits the facile photochemical dissociation of the C-I bond to form anionic iodide and a number of solvolyzed products. Following bond cleavage, iodide, is readily detected amperometrically a moderate oxidative potentials, allowing for the determination of a number of organoiodides at the 25-75 pg level. Following optimization of experimental parameters, the detection approach is linear over 3 orders of magnitude, and enhanced selectivity is demonstrated through the utilization of chromatographic retention times, dual electrode response ratios, and qualitative lamp on/off responses for analyte identification. The method is validated in a single-blind study and is successfully applied to the determination of liothyronine (T/sub 3/) in tablets.

  11. Methylene blue not ferrocene: Optimal reporters for electrochemical detection of protease activity.

    PubMed

    González-Fernández, Eva; Avlonitis, Nicolaos; Murray, Alan F; Mount, Andrew R; Bradley, Mark

    2016-10-15

    Electrochemical peptide-based biosensors are attracting significant attention for the detection and analysis of proteins. Here we report the optimisation and evaluation of an electrochemical biosensor for the detection of protease activity using self-assembled monolayers (SAMs) on gold surfaces, using trypsin as a model protease. The principle of detection was the specific proteolytic cleavage of redox-tagged peptides by trypsin, which causes the release of the redox reporter, resulting in a decrease of the peak current as measured by square wave voltammetry. A systematic enhancement of detection was achieved through optimisation of the properties of the redox-tagged peptide; this included for the first time a side-by-side study of the applicability of two of the most commonly applied redox reporters used for developing electrochemical biosensors, ferrocene and methylene blue, along with the effect of changing both the nature of the spacer and the composition of the SAM. Methylene blue-tagged peptides combined with a polyethylene-glycol (PEG) based spacer were shown to be the best platform for trypsin detection, leading to the highest fidelity signals (characterised by the highest sensitivity (signal gain) and a much more stable background than that registered when using ferrocene as a reporter). A ternary SAM (T-SAM) configuration, which included a PEG-based dithiol, minimised the non-specific adsorption of other proteins and was sensitive towards trypsin in the clinically relevant range, with a Limit of Detection (LoD) of 250pM. Kinetic analysis of the electrochemical response with time showed a good fit to a Michaelis-Menten surface cleavage model, enabling the extraction of values for kcat and KM. Fitting to this model enabled quantitative determination of the solution concentration of trypsin across the entire measurement range. Studies using an enzyme inhibitor and a range of real world possible interferents demonstrated a selective response to trypsin

  12. Methylene blue not ferrocene: Optimal reporters for electrochemical detection of protease activity.

    PubMed

    González-Fernández, Eva; Avlonitis, Nicolaos; Murray, Alan F; Mount, Andrew R; Bradley, Mark

    2016-10-15

    Electrochemical peptide-based biosensors are attracting significant attention for the detection and analysis of proteins. Here we report the optimisation and evaluation of an electrochemical biosensor for the detection of protease activity using self-assembled monolayers (SAMs) on gold surfaces, using trypsin as a model protease. The principle of detection was the specific proteolytic cleavage of redox-tagged peptides by trypsin, which causes the release of the redox reporter, resulting in a decrease of the peak current as measured by square wave voltammetry. A systematic enhancement of detection was achieved through optimisation of the properties of the redox-tagged peptide; this included for the first time a side-by-side study of the applicability of two of the most commonly applied redox reporters used for developing electrochemical biosensors, ferrocene and methylene blue, along with the effect of changing both the nature of the spacer and the composition of the SAM. Methylene blue-tagged peptides combined with a polyethylene-glycol (PEG) based spacer were shown to be the best platform for trypsin detection, leading to the highest fidelity signals (characterised by the highest sensitivity (signal gain) and a much more stable background than that registered when using ferrocene as a reporter). A ternary SAM (T-SAM) configuration, which included a PEG-based dithiol, minimised the non-specific adsorption of other proteins and was sensitive towards trypsin in the clinically relevant range, with a Limit of Detection (LoD) of 250pM. Kinetic analysis of the electrochemical response with time showed a good fit to a Michaelis-Menten surface cleavage model, enabling the extraction of values for kcat and KM. Fitting to this model enabled quantitative determination of the solution concentration of trypsin across the entire measurement range. Studies using an enzyme inhibitor and a range of real world possible interferents demonstrated a selective response to trypsin

  13. Electrochemical techniques for subsecond neurotransmitter detection in live rodents.

    PubMed

    Hascup, Kevin N; Hascup, Erin R

    2014-08-01

    Alterations in neurotransmission have been implicated in numerous neurodegenerative and neuropsychiatric disorders, including Alzheimer disease, Parkinson disease, epilepsy, and schizophrenia. Unfortunately, few techniques support the measurement of real-time changes in neurotransmitter levels over multiple days, as is essential for ethologic and pharmacodynamic testing. Microdialysis is commonly used for these research paradigms, but its poor temporal and spatial resolution make this technique inadequate for measuring the rapid dynamics (milliseconds to seconds) of fast signaling neurotransmitters, such as glutamate and acetylcholine. Enzymatic microelectrode arrays (biosensors) coupled with electrochemical recording techniques have demonstrated fast temporal resolution (less than 1 s), excellent spatial resolution (micron-scale), low detection limits (≤200 nM), and minimal damage (50 to 100 μm) to surrounding brain tissue. Here we discuss the benefits, methods, and animal welfare considerations of using platinum microelectrodes on a ceramic substrate for enzyme-based electrochemical recording techniques for real-time in vivo neurotransmitter recordings in both anesthetized and awake, freely moving rodents.

  14. Disordered array of Au covered Silicon nanowires for SERS biosensing combined with electrochemical detection

    PubMed Central

    Convertino, Annalisa; Mussi, Valentina; Maiolo, Luca

    2016-01-01

    We report on highly disordered array of Au coated silicon nanowires (Au/SiNWs) as surface enhanced Raman scattering (SERS) probe combined with electrochemical detection for biosensing applications. SiNWs, few microns long, were grown by plasma enhanced chemical vapor deposition on common microscope slides and covered by Au evaporated film, 150 nm thick. The capability of the resulting composite structure to act as SERS biosensor was studied via the biotin-avidin interaction: the Raman signal obtained from this structure allowed to follow each surface modification step as well as to detect efficiently avidin molecules over a broad range of concentrations from micromolar down to the nanomolar values. The metallic coverage wrapping SiNWs was exploited also to obtain a dual detection of the same bioanalyte by electrochemical impedance spectroscopy (EIS). Indeed, the SERS signal and impedance modifications induced by the biomolecule perturbations on the metalized surface of the NWs were monitored on the very same three-electrode device with the Au/SiNWs acting as both working electrode and SERS probe. PMID:27112197

  15. Disordered array of Au covered Silicon nanowires for SERS biosensing combined with electrochemical detection

    NASA Astrophysics Data System (ADS)

    Convertino, Annalisa; Mussi, Valentina; Maiolo, Luca

    2016-04-01

    We report on highly disordered array of Au coated silicon nanowires (Au/SiNWs) as surface enhanced Raman scattering (SERS) probe combined with electrochemical detection for biosensing applications. SiNWs, few microns long, were grown by plasma enhanced chemical vapor deposition on common microscope slides and covered by Au evaporated film, 150 nm thick. The capability of the resulting composite structure to act as SERS biosensor was studied via the biotin-avidin interaction: the Raman signal obtained from this structure allowed to follow each surface modification step as well as to detect efficiently avidin molecules over a broad range of concentrations from micromolar down to the nanomolar values. The metallic coverage wrapping SiNWs was exploited also to obtain a dual detection of the same bioanalyte by electrochemical impedance spectroscopy (EIS). Indeed, the SERS signal and impedance modifications induced by the biomolecule perturbations on the metalized surface of the NWs were monitored on the very same three-electrode device with the Au/SiNWs acting as both working electrode and SERS probe.

  16. Disordered array of Au covered Silicon nanowires for SERS biosensing combined with electrochemical detection.

    PubMed

    Convertino, Annalisa; Mussi, Valentina; Maiolo, Luca

    2016-04-26

    We report on highly disordered array of Au coated silicon nanowires (Au/SiNWs) as surface enhanced Raman scattering (SERS) probe combined with electrochemical detection for biosensing applications. SiNWs, few microns long, were grown by plasma enhanced chemical vapor deposition on common microscope slides and covered by Au evaporated film, 150 nm thick. The capability of the resulting composite structure to act as SERS biosensor was studied via the biotin-avidin interaction: the Raman signal obtained from this structure allowed to follow each surface modification step as well as to detect efficiently avidin molecules over a broad range of concentrations from micromolar down to the nanomolar values. The metallic coverage wrapping SiNWs was exploited also to obtain a dual detection of the same bioanalyte by electrochemical impedance spectroscopy (EIS). Indeed, the SERS signal and impedance modifications induced by the biomolecule perturbations on the metalized surface of the NWs were monitored on the very same three-electrode device with the Au/SiNWs acting as both working electrode and SERS probe.

  17. Graphene from electrochemical exfoliation and its direct applications in enhanced energy storage devices.

    PubMed

    Wei, Di; Grande, Lorenzo; Chundi, Vishnu; White, Richard; Bower, Chris; Andrew, Piers; Ryhänen, Tapani

    2012-01-30

    Graphite was electrochemically exfoliated in mixtures of room temperature ionic liquids and deionized water containing lithium salts to produce functionalized graphenes and such an electrochemical exfoliation technique can be directly used in making primary battery electrodes with significantly enhanced specific energy capacity. PMID:22170354

  18. Ultrasensitive Electrochemical Detection of mRNA Using Branched DNA Amplifiers

    SciTech Connect

    Mao, Xun; Liu, Guodong; Wang, Shengfu; Lin, Yuehe; Zhang, Aiguo; Zhang, Lurong; Ma, Yunqing

    2008-11-01

    We describe here an ultrasensitive electrochemical detection of m RNA protocol without RNA purification and PCR amplification. The new m RNA electrical detection capability is coupled to the amplification feature of branched DNA (bDNA) technology and with the nagnetic beads based electrochemical bioassay.

  19. Electrochemical detection of single cancer and healthy cell collisions on a microelectrode.

    PubMed

    Dick, Jeffrey E

    2016-09-18

    The electrochemical detection of single cancer cells and healthy cells is reported. Detection was achieved by monitoring the consumption of a single cell's contents upon its collisions with a microelectrode in the presence of surfactant. The electrochemical response between acute lymphoblastic lymphoma T-cells and healthy thymocytes differed by two orders of magnitude.

  20. Development of electrochemical based sandwich enzyme linked immunosensor for Cryptosporidium parvum detection in drinking water.

    PubMed

    Thiruppathiraja, Chinnasamy; Saroja, Veerappan; Kamatchiammal, Senthilkumar; Adaikkappan, Periyakaruppan; Alagar, Muthukaruppan

    2011-10-01

    Cryptosporidium parvum is one of the most important biological contaminants in drinking water and generates significant risks to public health. Due to low infectious dose of C. parvum, remarkably sensitive detection methods are required for water and food industry analysis. This present study describes a simple, sensitive, enzyme amplified sandwich form of an electrochemical immunosensor using dual labeled gold nanoparticles (alkaline phosphatase and anti-oocysts monoclonal antibody) in indium tin oxide (ITO) as an electrode to detect C. parvum. The biosensor was fabricated by immobilizing the anti-oocysts McAb on a gold nanoparticle functionalized ITO electrode, followed by the corresponding capture of analytes and dual labeled gold nanoparticle probe to detect the C. parvum target. The outcome shows the sensitivity of electrochemical immune sensor enhanced by gold nanoparticles with a limit of detection of 3 oocysts/mL in a minimal processing period. Our results demonstrated the sensitivity of the new approach compared to the customary method and the immunosensors showed acceptable precision, reproducibility, stability, and could be readily applied to multi analyte determination for environmental monitoring.

  1. Sensitive Electrochemical Detection of Enzymatically-generated Thiocholine at Carbon Nanotube Modified Glassy Carbon Electrode

    SciTech Connect

    Liu, Guodong; Riechers, Shawn L.; Mellen, Maria C.; Lin, Yuehe

    2005-11-01

    A carbon nanotube modified glassy-carbon (CNT/GC) electrode was used for enhancing the sensitivity of electrochemical measurements of enzymatically-generated thiocholine. Cyclic voltammetric and amperometric characteristics of thiocholine at CNT/GC, glassy carbon, carbon paste, and gold electrodes were compared. The CNT layer leads to a greatly improved anodic detection of enzymatically generated thiocholine product including lower oxidation overpotential (0.15 V) and higher sensitivity because of its electrocatalytic activity, fast electron transfer and large surface area. The sensor performance was optimized with respect to the operating conditions. Under the optimal batch conditions, a detection limit of 5 ?10 -6 mol/L was obtained with good precision (RSD = 5.2%, n=10). Furthermore, the attractive response of thiocholine on a CNT/GC electrode has allowed it to be used for constant-potential flow injection analysis. The detection limit was greatly improved to 0.3 ?10-6 mol/L. The high sensitivity electrochemical detection of enzymatically generated thiocholine with a CNT sensing platform holds great promise to prepare an acetylcholinesterase biosensor for monitoring organophosphate pesticides and nerve agents.

  2. Development of an electrochemical biosensor for alkylphenol detection.

    PubMed

    Belkhamssa, Najet; da Costa, João P; Justino, Celine I L; Santos, Patrícia S M; Cardoso, Susana; Duarte, Armando C; Rocha-Santos, Teresa; Ksibi, Mohamed

    2016-09-01

    In this work, electrochemical biosensors based on field effect transistors (FET) with single-walled carbon nanotubes (SWCNT) were constructed as disposable analytical devices to detect alkylphenols through immunoreaction using 4-nonylphenol (NP) as model analyte, and validated by comparison with enzyme-linked immunosorbent assay (ELISA). The calibration curve displays a working range with five concentrations between 5 and 500µgL(-1), and for each concentration, five biosensors were analysed for reproducibility estimation and two analytical measurements were performed for each biosensor for repeatability estimation. The accuracy of the biosensors was validated by analyzing NP contents in ten spiked artificial seawater samples and comparing these results to those obtained with the traditional ELISA methodology. Excellent analytical performance was obtained with reproducibility of 0.56±0.08%, repeatability of 0.5±0.2%, limit of detection for NP as low as 5µgL(-1), and average recovery between 97.8% and 104.6%. This work demonstrates that simple biosensors can be used to detect hazardous priority substances in seawater samples, even at low concentrations. PMID:27343574

  3. Self-assembled magnetic bead chains for sensitivity enhancement of microfluidic electrochemical biosensor platforms.

    PubMed

    Armbrecht, L; Dincer, C; Kling, A; Horak, J; Kieninger, J; Urban, G

    2015-11-21

    In this paper, we present a novel approach to enhance the sensitivity of microfluidic biosensor platforms with self-assembled magnetic bead chains. An adjustable, more than 5-fold sensitivity enhancement is achieved by introducing a magnetic field gradient along a microfluidic channel by means of a soft-magnetic lattice with a 350 μm spacing. The alternating magnetic field induces the self-assembly of the magnetic beads in chains or clusters and thus improves the perfusion and active contact between the analyte and the beads. The soft-magnetic lattices can be applied independent of the channel geometry or chip material to any microfluidic biosensing platform. At the same time, the bead-based approach achieves chip reusability and shortened measurement times. The bead chain properties and the maximum flow velocity for bead retention were validated by optical microscopy in a glass capillary. The magnetic actuation system was successfully validated with a biotin-streptavidin model assay on a low-cost electrochemical microfluidic chip, fabricated by dry-film photoresist technology (DFR). Labelling with glucose oxidase (GOx) permits rapid electrochemical detection of enzymatically produced H2O2. PMID:26394820

  4. Synthesis of surface roughed Pt nanowires and their application as electrochemical sensors for hydrogen peroxide detection.

    PubMed

    Gao, Fan; Li, Zhiyang; Ruan, Dajiang; Gu, Zhiyong

    2014-09-01

    In this paper, platinum nanowires with roughed surface textures were fabricated by a galvanostatic electrodeposition method for electrochemical sensors toward hydrogen peroxide detection. The electrochemical behavior of the glassy carbon electrode modified with these nanowires has been studied for oxidation of hydrogen peroxide by using cyclic voltammetry and amperometry in phosphate buffer solution. Surface roughness was found to enhance the sensitivity of the Pt nanowire based electrochemical sensor towards H2O2. The Pt nanowires with rough surfaces displayed higher electrocatalytic response compared to nanowires with smooth surfaces, with a sensitivity of 171 μA mM(-1) cm(-2), and linear dynamic range up to 35 mM. The nanowire concentration effect on the sensing behavior was investigated with the best sensitivity output found at a nanowire concentration of roughly 8.6 x 10(7) number of nanowires/cm2. The new sensor also showed good anti-interference property and exhibited high accuracy when a real water sample containing H2O2 was measured. PMID:25924305

  5. Synthesis of surface roughed Pt nanowires and their application as electrochemical sensors for hydrogen peroxide detection.

    PubMed

    Gao, Fan; Li, Zhiyang; Ruan, Dajiang; Gu, Zhiyong

    2014-09-01

    In this paper, platinum nanowires with roughed surface textures were fabricated by a galvanostatic electrodeposition method for electrochemical sensors toward hydrogen peroxide detection. The electrochemical behavior of the glassy carbon electrode modified with these nanowires has been studied for oxidation of hydrogen peroxide by using cyclic voltammetry and amperometry in phosphate buffer solution. Surface roughness was found to enhance the sensitivity of the Pt nanowire based electrochemical sensor towards H2O2. The Pt nanowires with rough surfaces displayed higher electrocatalytic response compared to nanowires with smooth surfaces, with a sensitivity of 171 μA mM(-1) cm(-2), and linear dynamic range up to 35 mM. The nanowire concentration effect on the sensing behavior was investigated with the best sensitivity output found at a nanowire concentration of roughly 8.6 x 10(7) number of nanowires/cm2. The new sensor also showed good anti-interference property and exhibited high accuracy when a real water sample containing H2O2 was measured.

  6. Detection of 1,5-Anhydroglucitol by Electrochemical Impedance Spectroscopy

    PubMed Central

    Adamson, Teagan L.; Cook, Curtiss B.

    2014-01-01

    Multiple markers are used to assess glycemic control in patients with diabetes mellitus (DM). New technology that permits simultaneous detection of multiple biomarkers combined with those used at the point of care indicative of glycemic control, including glycemic variability determined from 1,5-anhydroglucitol measurement, could provide better management and further insight into the disease. This platform was based on previous research involving glucose detection and uses electrochemical impedance spectroscopy to detect a range of 1,5-anhydroglucitol concentrations at an optimal binding frequency. The enzyme pyranose oxidase was fixed to gold electrodes while a sine wave of sweeping frequencies was induced in purified solutions and in variable presence of whole blood. The optimal binding frequency for the detection of 1,5-anhydroglucitol was found to be 3.71 kHz. The impedance response compared to the concentration of target present was found to have a logarithmic slope of 7.04 with an R-squared value of 0.96. This response includes 2 experimental sets, a single test of a low concentration range and a high concentration range with 5 replicates. The relative standard deviation of the high range varied from 28% to 27% from lowest to highest concentrations. Best detection in complex solutions was found in lower blood concentrations of 0.5% and 1%, but maintained relatively high accuracy in concentrations 5% and 10%. The sensor platform was successfully evaluated at a high dynamic range of 1,5-AG in purified solutions. In the presence of whole blood, lowest percentages yielded the best results indicating that filtering interferents may be necessary in final device architecture. PMID:24876587

  7. Electrochemical sensor for rapid detection of triclosan using a multiwall carbon nanotube film.

    PubMed

    Yang, Jinquan; Wang, Peng; Zhang, Xiaojun; Wu, Kangbing

    2009-10-28

    It is of great importance to develop a rapid analytical method for triclosan because it has been widely added in household products and can form highly toxic dioxin-type derivatives. Herein, an electrochemical sensor based on a multiwall carbon nanotube (MWCNT) film was developed for the rapid detection of triclosan. The electrochemical responses of triclosan were examined, given that its oxidation is irreversible and involves one electron. At the MWCNT film, the oxidation signals of triclosan remarkably increase, suggesting that the MWCNT film exhibits a considerable enhancement effect with triclosan. The analytical parameters, such as pH value, amount of MWCNT suspension, and accumulation time, were optimized. The linear range is from 50 microg L(-1) to 1.75 mg L(-1), and the limit of detection is 16.5 microg L(-1) (about 57 nM). Finally, the new method was successfully employed to detect triclosan in different toothpaste samples, which was testified using high-performance liquid chromatography (HPLC).

  8. Determination of iodide in urine by ion-pair chromatography with electrochemical detection.

    PubMed

    Below, H; Kahlert, H

    2001-10-01

    A variety of parameters affecting the determination of iodide in biological materials by ion-pair chromatography and electrochemical detection were examined in detail. It became apparent that the pH value, the ion-pair concentration, the proportion of organic solvent and of organic bases as a component of the buffer solution, as well as the salt concentration in the eluent system could effectively influence the retention characteristics of iodide in the chromatographic system, resulting in the separation of potential interfering substances. The presence of other anions in the sample matrix has to be taken into consideration, particularly thiocyanate because of its long retention time. Investigations of the electrochemical detection mechanism revealed that the reaction hitherto assumed to be responsible for detector signal generation (formation of AgI) is incorrect. In addition, a much more sensitive detection of iodide than that cited in the literature to date is possible if the detector potential is optimally selected and any anticipated interfering substances are removed by chromatography. Use of a gold electrode rather than a silver electrode also considerably enhances the reliability of the procedure.

  9. Electrochemical noise sensors for detection of localized and general corrosion of natural gas transmission pipelines

    SciTech Connect

    Holcomb, Gordon R.; Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Russell, James H.; Ziomek-Moroz, Margaret

    2002-09-01

    The U.S. Department of Energy, National Energy Technology Laboratory funded a Natural Gas Infrastructure Reliability program directed at increasing and enhancing research and development activities in topics such as remote leak detection, pipe inspection, and repair technologies and materials. The Albany Research Center (ARC), U.S. Department of Energy was funded to study the use of electrochemical noise sensors for detection of localized and general corrosion of natural gas transmission pipelines. As part of this, ARC entered into a collaborative effort with the corrosion sensor industry to demonstrate the capabilities of commercially available remote corrosion sensors for use with the Nation's Gas Transmission Pipeline Infrastructure needs. The goal of the research was to develop an emerging corrosion sensor technology into a monitor for the type and degree of corrosion occurring at key locations in gas transmission pipelines.

  10. A microfluidic paper-based electrochemical biosensor array for multiplexed detection of metabolic biomarkers

    NASA Astrophysics Data System (ADS)

    Zhao, Chen; Thuo, Martin M.; Liu, Xinyu

    2013-10-01

    Paper-based microfluidic devices have emerged as simple yet powerful platforms for performing low-cost analytical tests. This paper reports a microfluidic paper-based electrochemical biosensor array for multiplexed detection of physiologically relevant metabolic biomarkers. Different from existing paper-based electrochemical devices, our device includes an array of eight electrochemical sensors and utilizes a handheld custom-made electrochemical reader (potentiostat) for signal readout. The biosensor array can detect several analytes in a sample solution and produce multiple measurements for each analyte from a single run. Using the device, we demonstrate simultaneous detection of glucose, lactate and uric acid in urine, with analytical performance comparable to that of the existing commercial and paper-based platforms. The paper-based biosensor array and its electrochemical reader will enable the acquisition of high-density, statistically meaningful diagnostic information at the point of care in a rapid and cost-efficient way.

  11. Electrochemical flow injection analysis of hydrazine in an excess of an active pharmaceutical ingredient: achieving pharmaceutical detection limits electrochemically.

    PubMed

    Channon, Robert B; Joseph, Maxim B; Bitziou, Eleni; Bristow, Anthony W T; Ray, Andrew D; Macpherson, Julie V

    2015-10-01

    The quantification of genotoxic impurities (GIs) such as hydrazine (HZ) is of critical importance in the pharmaceutical industry in order to uphold drug safety. HZ is a particularly intractable GI and its detection represents a significant technical challenge. Here, we present, for the first time, the use of electrochemical analysis to achieve the required detection limits by the pharmaceutical industry for the detection of HZ in the presence of a large excess of a common active pharmaceutical ingredient (API), acetaminophen (ACM) which itself is redox active, typical of many APIs. A flow injection analysis approach with electrochemical detection (FIA-EC) is utilized, in conjunction with a coplanar boron doped diamond (BDD) microband electrode, insulated in an insulating diamond platform for durability and integrated into a two piece flow cell. In order to separate the electrochemical signature for HZ such that it is not obscured by that of the ACM (present in excess), the BDD electrode is functionalized with Pt nanoparticles (NPs) to significantly shift the half wave potential for HZ oxidation to less positive potentials. Microstereolithography was used to fabricate flow cells with defined hydrodynamics which minimize dispersion of the analyte and optimize detection sensitivity. Importantly, the Pt NPs were shown to be stable under flow, and a limit of detection of 64.5 nM or 0.274 ppm for HZ with respect to the ACM, present in excess, was achieved. This represents the first electrochemical approach which surpasses the required detection limits set by the pharmaceutical industry for HZ detection in the presence of an API and paves the wave for online analysis and application to other GI and API systems. PMID:26302058

  12. Preparation of graphene–Ag composites and their application for electrochemical detection of chloride

    SciTech Connect

    Yu, Mei; Liu, Pengrui; Zhang, Shilu; Liu, Jianhua; An, Junwei; Li, Songmei

    2012-11-15

    Highlights: ► Graphene–Ag composites were prepared in situ using ascorbic acid as green reducing agent. ► The morphology of Ag particles was irregular sheet and Ag particles homogeneously distributed on the graphene matrix. ► The surface-enhanced Raman scattering enhancement factor of D band is 5.85 for composites. ► The composites exhibited good sensitivity for the detection of chloride ions. -- Abstract: Graphene–Ag composites were prepared in situ using ascorbic acid as green reducing agent. The composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected-area electronic diffraction (SAED), and Raman spectrometer. It was showed that Ag particles homogeneously distributed on the graphene matrix. The morphology of Ag particles was irregular sheet with (1 1 1) basal plane. The surface-enhanced Raman scattering (SERS) enhancement factor of D band is 5.85 for composites. The application of the composites for electrochemical detection of chloride was studied by cyclic voltammetry. The composites exhibited good sensitivity for the detection of chloride ions. The maximum peak current of cyclic voltammetry curve in 5 mM KCl was 0.80 mA. In the range of 500 μM to 50 mM for Cl{sup −}, the current response was proportional and linear to the Cl{sup −} concentration. The sensitivity to the detection for Cl{sup −} was 0.059 (mA/mM) and the detection limit was 61 μM for Cl{sup −}. It indicates graphene–Ag composites would be a competitive material for detection of halide.

  13. Aptamer-based highly sensitive electrochemical detection of thrombin via the amplification of graphene.

    PubMed

    Jiang, Liping; Yuan, Ruo; Chai, Yaqin; Yuan, Yali; Bai, Lijuan; Wang, Yan

    2012-05-21

    Herein, we successfully fabricated a highly sensitive label-free electrochemical aptasensor for thrombin based on the amplification of graphene (Gra). The excellent electrochemical probe of nickel hexacyanoferrate nanoparticles (NiHCFNPs) was introduced to form Nafion-Graphene-NiHCFNPs (Nf-Gra-NiHCFNPs) nanocomposites membrane on the gold electrode. The employment of graphene not only enhanced the surface area of the electrode with increased NiHCFNPs immobilization, but also improved the conductivity of the electrode, which further effectively improved the sensitivity of this proposed aptasensor. Subsequently, AuNPs layer was formed to immobilize the thrombin aptamer (TBA) and enhance the stability of the composite monolayer mentioned above. Then, thiol-modified TBA was assembled onto the AuNPs layer. Thereafter, hexanethiol (HT) was employed to block the possible remaining active sites. With the dual amplification of Gra and AuNPs, the resulting aptasensor exhibited good current response to target thrombin with a wide linear range extended from 1 pM to 80 nM (the detection limit was 0.3 pM). Additionally, the morphologies of bare Au substrate, nickel hexacyanoferrate nanoparticles (NiHCFNPs) and nanocomposites were successfully characterized by atomic force microscopy (AFM).

  14. Electrochemical impedance spectroscopy based-on interferon-gamma detection

    NASA Astrophysics Data System (ADS)

    Li, Guan-Wei; Kuo, Yi-Ching; Tsai, Pei-I.; Lee, Chih-Kung

    2014-03-01

    Tuberculosis (TB) is an ancient disease constituted a long-term menace to public health. According to World Health Organization (WHO), mycobacterium tuberculosis (MTB) infected nearly a third of people of the world. There is about one new TB occurrence every second. Interferon-gamma (IFN-γ) is associated with susceptibility to TB, and interferongamma release assays (IGRA) is considered to be the best alternative of tuberculin skin test (TST) for diagnosis of latent tuberculosis infection (LTBI). Although significant progress has been made with regard to the design of enzyme immunoassays for IFN-γ, adopting this assay is still labor-intensive and time-consuming. To alleviate these drawbacks, we used IFN-γ antibody to facilitate the detection of IFN-γ. An experimental verification on the performance of IGRA was done in this research. We developed two biosensor configurations, both of which possess high sensitivity, specificity, and rapid IFN-γ diagnoses. The first is the electrochemical method. The second is a circular polarization interferometry configuration, which incorporates two light beams with p-polarization and s-polarization states individually along a common path, a four photo-detector quadrature configuration to arrive at a phase modulated ellipsometer. With these two methods, interaction between IFN-γ antibody and IFN-γ were explored and presented in detail.

  15. Electrochemical immunosensor based on hyperbranched structure for carcinoembryonic antigen detection.

    PubMed

    Miao, Jingjing; Wang, Xiaobo; Lu, Liandi; Zhu, Peiyuan; Mao, Chun; Zhao, Haolin; Song, Youchao; Shen, Jian

    2014-08-15

    Sensitive determination of carcinoembryonic antigen (CEA) is very important in clinical research and diagnosis. Herein we report the design and synthesis of a new kind of immunosensor based on the benefits of hyperbranched structure. The hyperbranched polyester was grafted to the surface of indium tin oxides glass (ITO) electrode, and the grafting processes were characterized by attentuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). After CEA and horse radish peroxidase (HRP)-labeled antibody-conjugated AuNPs (HRP-Ab2-AuNPs) bioconjugates were immobilized on the surface of the hyperbranched structure-modified electrode, the optimized conditions of the above electrode were investigated. Moreover, the analytical performance of the proposed immunosensor showed a high sensitivity, a linear range from 0.01 to 80ng/mL with a low detection limit of 2.36pg/mL, and good selectivity for CEA. The designed immunoassay system holds great potential for ultrasensitive electrochemical biosensing of other analytes. PMID:24607616

  16. Electro-Chemically Enhanced Mechanical Polishing of Nickel Mandrels

    NASA Technical Reports Server (NTRS)

    Gubarev, Mikhail; Ramsey, Brian; Engelhaupt, Darell

    2006-01-01

    Grinding and mechanical polishing techniques used for x-ray optics mandrel figuring lead to mid-frequency surface ripple. These small figure variations have to be addressed in order to improve the performance of the resulting x-ray mirrors. If the electrochemical etching is combined with mechanical polishing, the figuring and the surface finishing cm be done simultaneously and be used to correct the mid-frequency surface ripple. It is shown that the electrochemical mechanical polishing method allows selective removal of nickel alloy without mandrel surface microroughness degradation.

  17. Electrochemical detection of uric acid using ruthenium-dioxide-coated carbon nanotube directly grown onto Si wafer

    NASA Astrophysics Data System (ADS)

    Shih, Yi-Ting; Lee, Kuei-Yi; Lin, Chung-Kuang

    2015-12-01

    Carbon nanotubes (CNTs) directly grown onto a Si substrate by thermal chemical vapor deposition were used in uric acid (UA) detection. The process is simple and formation is easy without the need for additional chemical treatments. However, CNTs lack selectivity and sensitivity to UA. To enhance the electrochemical analysis, ruthenium oxide was used as a catalytic mediator in the modification of electrodes. The electrochemical results show that RuO2 nanostructures coated onto CNTs can strengthen the UA signal. The peak currents of RuO2 nanostructures coated onto CNTs linearly increase with increasing UA concentration, meaning that they can work as electrodes for UA detection. The lowest detection limit and highest sensitivity were 55 nM and 4.36 µA/µM, respectively. Moreover, the characteristics of RuO2 nanostructures coated onto CNTs were examined by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy.

  18. A Facile Electrochemical Sensor for Nonylphenol Determination Based on the Enhancement Effect of Cetyltrimethylammonium Bromide

    PubMed Central

    Lu, Qing; Zhang, Weina; Wang, Zhihui; Yu, Guangxia; Yuan, Yuan; Zhou, Yikai

    2013-01-01

    A facile electrochemical sensor for the determination of nonylphenol (NP) was fabricated in this work. Cetyltrimethylammonium bromide (CTAB), which formed a bilayer on the surface of the carbon paste (CP) electrode, displayed a remarkable enhancement effect for the electrochemical oxidation of NP. Moreover, the oxidation peak current of NP at the CTAB/CP electrode demonstrated a linear relationship with NP concentration, which could be applied in the direct determination of NP. Some experimental parameters were investigated, such as external solution pH, mode and time of accumulation, concentration and modification time of CTAB and so on. Under optimized conditions, a wide linear range from 1.0 × 10−7 mol·L−1 to 2.5 × 10−5 mol·L−1 was obtained for the sensor, with a low limit of detection at 1.0 × 10−8 mol·L−1. Several distinguishing advantages of the as-prepared sensor, including facile fabrication, easy operation, low cost and so on, suggest a great potential for its practical applications. PMID:23296332

  19. Electrochemical stripping analysis of nanogold label-induced silver deposition for ultrasensitive multiplexed detection of tumor markers.

    PubMed

    Lai, Guosong; Wang, Lili; Wu, Jie; Ju, Huangxian; Yan, Feng

    2012-04-01

    A multiplexed electrochemical immunoassay method was developed for simultaneous ultrasensitive measurement of tumor markers based on electrochemical stripping analysis of silver nanoparticles (Ag NPs). The Ag NPs were deposited on a disposable immunosensor array with a reduction reaction catalyzed by nanogold labels. The immunosensor array was prepared by covalently immobilizing capture antibodies on chitosan modified screen-printed carbon electrodes. Through a sandwich-type immunoreaction, antibody-functionalized Au NPs were captured onto immunosensor surface to induce the silver deposition from a silver enhancer solution. The deposited Ag NPs could be directly measured by anodic stripping analysis in KCl solution. The catalytic deposition enhanced the analytical sensitivity for detection of protein markers. The interference of dissolved oxygen could be avoided as the detection was performed with positive stripping potential range. Using carcinoembryonic antigen and α-fetoprotein as model analytes, the proposed multiplexed immunoassay method showed wide linear ranges of three orders of magnitude with the detection limits down to 3.5 and 3.9 pg mL(-1), respectively. The localized silver deposition, as well as the stripping detection process, eliminated completely the electrochemical cross talk between adjacent immunosensors. The immunosensor array exhibited acceptable reproducibility, stability and accuracy, showing a promising potential in multianalyte determination for clinical application.

  20. Electrochemical impedance spectroscopy based MEMS sensors for phthalates detection in water and juices

    NASA Astrophysics Data System (ADS)

    Zia, Asif I.; Mohd Syaifudin, A. R.; Mukhopadhyay, S. C.; Yu, P. L.; Al-Bahadly, I. H.; Gooneratne, Chinthaka P.; Kosel, Jǘrgen; Liao, Tai-Shan

    2013-06-01

    Phthalate esters are ubiquitous environmental and food pollutants well known as endocrine disrupting compounds (EDCs). These developmental and reproductive toxicants pose a grave risk to the human health due to their unlimited use in consumer plastic industry. Detection of phthalates is strictly laboratory based time consuming and expensive process and requires expertise of highly qualified and skilled professionals. We present a real time, non-invasive, label free rapid detection technique to quantify phthalates' presence in deionized water and fruit juices. Electrochemical impedance spectroscopy (EIS) technique applied to a novel planar inter-digital (ID) capacitive sensor plays a vital role to explore the presence of phthalate esters in bulk fluid media. The ID sensor with multiple sensing gold electrodes was fabricated on silicon substrate using micro-electromechanical system (MEMS) device fabrication technology. A thin film of parylene C polymer was coated as a passivation layer to enhance the capacitive sensing capabilities of the sensor and to reduce the magnitude of Faradic current flowing through the sensor. Various concentrations, 0.002ppm through to 2ppm of di (2-ethylhexyl) phthalate (DEHP) in deionized water, were exposed to the sensing system by dip testing method. Impedance spectra obtained was analysed to determine sample conductance which led to consequent evaluation of its dielectric properties. Electro-chemical impedance spectrum analyser algorithm was employed to model the experimentally obtained impedance spectra. Curve fitting technique was applied to deduce constant phase element (CPE) equivalent circuit based on Randle's equivalent circuit model. The sensing system was tested to detect different concentrations of DEHP in orange juice as a real world application. The result analysis indicated that our rapid testing technique is able to detect the presence of DEHP in all test samples distinctively.

  1. Preparation and characterization of AuNPs/CNTs-ErGO electrochemical sensors for highly sensitive detection of hydrazine.

    PubMed

    Zhao, Zhenting; Sun, Yongjiao; Li, Pengwei; Zhang, Wendong; Lian, Kun; Hu, Jie; Chen, Yong

    2016-09-01

    A highly sensitive electrochemical sensor of hydrazine has been fabricated by Au nanoparticles (AuNPs) coating of carbon nanotubes-electrochemical reduced graphene oxide composite film (CNTs-ErGO) on glassy carbon electrode (GCE). Cyclic voltammetry and potential amperometry have been used to investigate the electrochemical properties of the fabricated sensors for hydrazine detection. The performances of the sensors were optimized by varying the CNTs to ErGO ratio and the quantity of Au nanoparticles. The results show that under optimal conditions, a sensitivity of 9.73μAμM(-1)cm(-2), a short response time of 3s, and a low detection limit of 0.065μM could be achieved with a linear concentration response range from 0.3μM to 319μM. The enhanced electrochemical performances could be attributed to the synergistic effect between AuNPs and CNTs-ErGO film and the outstanding catalytic effect of the Au nanoparticles. Finally, the sensor was successfully used to analyse the tap water, showing high potential for practical applications. PMID:27343607

  2. An aptamer-based electrochemical biosensor for the detection of Salmonella.

    PubMed

    Ma, Xiaoyuan; Jiang, Yihui; Jia, Fei; Yu, Ye; Chen, Jie; Wang, Zhouping

    2014-03-01

    Salmonella is one of the most common causes of food-associated disease. An electrochemical biosensor was developed for Salmonella detection using a Salmonella-specific recognition aptamer. The biosensor was based on a glassy carbon electrode modified with graphene oxide and gold nanoparticles. Then, the aptamer ssDNA sequence could be linked to the electrode. Each assembly step was accompanied by changes to the electrochemical parameters. After incubation of the modified electrode with Salmonella, the electrochemical properties between the electrode and the electrolyte changed accordingly. The electrochemical impedance spectrum was measured to quantify the Salmonella. The results revealed that, when more Salmonella were added to the reaction system, the current between the electrode and electrolyte decreased; in other words, the impendence gradually increased. A detection limit as low as 3 cfu/mL was obtained. This novel method is specific and fast, and it has the potential for real sample detection.

  3. Microchip-based electrochemical detection using a 3-D printed wall-jet electrode device.

    PubMed

    Munshi, Akash S; Martin, R Scott

    2016-02-01

    Three dimensional (3-D) printing technology has evolved dramatically in the last few years, offering the capability of printing objects with a variety of materials. Printing microfluidic devices using this technology offers various advantages such as ease and uniformity of fabrication, file sharing between laboratories, and increased device-to-device reproducibility. One unique aspect of this technology, when used with electrochemical detection, is the ability to produce a microfluidic device as one unit while also allowing the reuse of the device and electrode for multiple analyses. Here we present an alternate electrode configuration for microfluidic devices, a wall-jet electrode (WJE) approach, created by 3-D printing. Using microchip-based flow injection analysis, we compared the WJE design with the conventionally used thin-layer electrode (TLE) design. It was found that the optimized WJE system enhances analytical performance (as compared to the TLE design), with improvements in sensitivity and the limit of detection. Experiments were conducted using two working electrodes - 500 μm platinum and 1 mm glassy carbon. Using the 500 μm platinum electrode the calibration sensitivity was 16 times higher for the WJE device (as compared to the TLE design). In addition, use of the 1 mm glassy carbon electrode led to limit of detection of 500 nM for catechol, as compared to 6 μM for the TLE device. Finally, to demonstrate the versatility and applicability of the 3-D printed WJE approach, the device was used as an inexpensive electrochemical detector for HPLC. The number of theoretical plates was comparable to the use of commercially available UV and MS detectors, with the WJE device being inexpensive to utilize. These results show that 3-D-printing can be a powerful tool to fabricate reusable and integrated microfluidic detectors in configurations that are not easily achieved with more traditional lithographic methods. PMID:26649363

  4. An aptasensor for electrochemical detection of tumor necrosis factor in human blood.

    PubMed

    Liu, Ying; Zhou, Qing; Revzin, Alexander

    2013-08-01

    Electrochemical aptasensors can detect disease markers such as cytokines to provide point-of-care diagnosis that is low-cost, rapid, specific and sensitive. Herein, we describe the development of an aptamer-based electrochemical sensor for detection and analysis of tumor necrosis factor-alpha (TNF-α) - a key inflammatory cytokine - in whole human blood. When testing spiked blood, a TNF-α detection limit of 58 pM (10 ng mL(-1)) and a linear range of 6 nM (100 ng mL(-1)) could be achieved. Furthermore, detection of TNF-α in mitogen stimulated whole blood was demonstrated.

  5. RNA aptamer based electrochemical biosensor for sensitive and selective detection of cAMP.

    PubMed

    Zhao, Fulin; Xie, Qingyun; Xu, Mingfei; Wang, Shouyu; Zhou, Jiyong; Liu, Fei

    2015-04-15

    Cyclic adenosine monophosphate (cAMP) is an important small biological molecule associated with the healthy state of living organism. In order to realize highly sensitive and specific detection of cAMP, here an RNA aptamer and electrochemical impedance spectroscopy (EIS) based biosensor enhanced by gold nanoparticles electrodeposited on the surface of gold electrode is designed. The designed aptasensor has a wide effective measuring range from 50pM to 250pM with a detection limit of 50pM in PBS buffer, and an effective measuring range from 50nM to 1μM with a detection limit of 50nM in serum. The designed biosensor is also able to detect cAMP with high sensitivity, specificity, and stability. Since the biosensor can be easily fabricated with low cost and repeatedly used for at least two times, it owns great potential in wide application fields such as clinical test and food inspection, etc.

  6. Carbon Nanomaterials Based Electrochemical Sensors/Biosensors for the Sensitive Detection of Pharmaceutical and Biological Compounds.

    PubMed

    Adhikari, Bal-Ram; Govindhan, Maduraiveeran; Chen, Aicheng

    2015-09-04

    Electrochemical sensors and biosensors have attracted considerable attention for the sensitive detection of a variety of biological and pharmaceutical compounds. Since the discovery of carbon-based nanomaterials, including carbon nanotubes, C60 and graphene, they have garnered tremendous interest for their potential in the design of high-performance electrochemical sensor platforms due to their exceptional thermal, mechanical, electronic, and catalytic properties. Carbon nanomaterial-based electrochemical sensors have been employed for the detection of various analytes with rapid electron transfer kinetics. This feature article focuses on the recent design and use of carbon nanomaterials, primarily single-walled carbon nanotubes (SWCNTs), reduced graphene oxide (rGO), SWCNTs-rGO, Au nanoparticle-rGO nanocomposites, and buckypaper as sensing materials for the electrochemical detection of some representative biological and pharmaceutical compounds such as methylglyoxal, acetaminophen, valacyclovir, β-nicotinamide adenine dinucleotide hydrate (NADH), and glucose. Furthermore, the electrochemical performance of SWCNTs, rGO, and SWCNT-rGO for the detection of acetaminophen and valacyclovir was comparatively studied, revealing that SWCNT-rGO nanocomposites possess excellent electrocatalytic activity in comparison to individual SWCNT and rGO platforms. The sensitive, reliable and rapid analysis of critical disease biomarkers and globally emerging pharmaceutical compounds at carbon nanomaterials based electrochemical sensor platforms may enable an extensive range of applications in preemptive medical diagnostics.

  7. Carbon Nanomaterials Based Electrochemical Sensors/Biosensors for the Sensitive Detection of Pharmaceutical and Biological Compounds.

    PubMed

    Adhikari, Bal-Ram; Govindhan, Maduraiveeran; Chen, Aicheng

    2015-01-01

    Electrochemical sensors and biosensors have attracted considerable attention for the sensitive detection of a variety of biological and pharmaceutical compounds. Since the discovery of carbon-based nanomaterials, including carbon nanotubes, C60 and graphene, they have garnered tremendous interest for their potential in the design of high-performance electrochemical sensor platforms due to their exceptional thermal, mechanical, electronic, and catalytic properties. Carbon nanomaterial-based electrochemical sensors have been employed for the detection of various analytes with rapid electron transfer kinetics. This feature article focuses on the recent design and use of carbon nanomaterials, primarily single-walled carbon nanotubes (SWCNTs), reduced graphene oxide (rGO), SWCNTs-rGO, Au nanoparticle-rGO nanocomposites, and buckypaper as sensing materials for the electrochemical detection of some representative biological and pharmaceutical compounds such as methylglyoxal, acetaminophen, valacyclovir, β-nicotinamide adenine dinucleotide hydrate (NADH), and glucose. Furthermore, the electrochemical performance of SWCNTs, rGO, and SWCNT-rGO for the detection of acetaminophen and valacyclovir was comparatively studied, revealing that SWCNT-rGO nanocomposites possess excellent electrocatalytic activity in comparison to individual SWCNT and rGO platforms. The sensitive, reliable and rapid analysis of critical disease biomarkers and globally emerging pharmaceutical compounds at carbon nanomaterials based electrochemical sensor platforms may enable an extensive range of applications in preemptive medical diagnostics. PMID:26404304

  8. Carbon Nanomaterials Based Electrochemical Sensors/Biosensors for the Sensitive Detection of Pharmaceutical and Biological Compounds

    PubMed Central

    Adhikari, Bal-Ram; Govindhan, Maduraiveeran; Chen, Aicheng

    2015-01-01

    Electrochemical sensors and biosensors have attracted considerable attention for the sensitive detection of a variety of biological and pharmaceutical compounds. Since the discovery of carbon-based nanomaterials, including carbon nanotubes, C60 and graphene, they have garnered tremendous interest for their potential in the design of high-performance electrochemical sensor platforms due to their exceptional thermal, mechanical, electronic, and catalytic properties. Carbon nanomaterial-based electrochemical sensors have been employed for the detection of various analytes with rapid electron transfer kinetics. This feature article focuses on the recent design and use of carbon nanomaterials, primarily single-walled carbon nanotubes (SWCNTs), reduced graphene oxide (rGO), SWCNTs-rGO, Au nanoparticle-rGO nanocomposites, and buckypaper as sensing materials for the electrochemical detection of some representative biological and pharmaceutical compounds such as methylglyoxal, acetaminophen, valacyclovir, β-nicotinamide adenine dinucleotide hydrate (NADH), and glucose. Furthermore, the electrochemical performance of SWCNTs, rGO, and SWCNT-rGO for the detection of acetaminophen and valacyclovir was comparatively studied, revealing that SWCNT-rGO nanocomposites possess excellent electrocatalytic activity in comparison to individual SWCNT and rGO platforms. The sensitive, reliable and rapid analysis of critical disease biomarkers and globally emerging pharmaceutical compounds at carbon nanomaterials based electrochemical sensor platforms may enable an extensive range of applications in preemptive medical diagnostics. PMID:26404304

  9. Electrochemical affinity biosensors for detection of mycotoxins: A review.

    PubMed

    Vidal, Juan C; Bonel, Laura; Ezquerra, Alba; Hernández, Susana; Bertolín, Juan R; Cubel, Carlota; Castillo, Juan R

    2013-11-15

    This review discusses the current state of electrochemical biosensors in the determination of mycotoxins in foods. Mycotoxins are highly toxic secondary metabolites produced by molds. The acute toxicity of these results in serious human and animal health problems, although it has been only since early 1960s when the first studied aflatoxins were found to be carcinogenic. Mycotoxins affect a broad range of agricultural products, most important cereals and cereal-based foods. A majority of countries, mentioning especially the European Union, have established preventive programs to control contamination and strict laws of the permitted levels in foods. Official methods of analysis of mycotoxins normally requires sophisticated instrumentation, e.g. liquid chromatography with fluorescence or mass detectors, combined with extraction procedures for sample preparation. For about sixteen years, the use of simpler and faster analytical procedures based on affinity biosensors has emerged in scientific literature as a very promising alternative, particularly electrochemical (i.e., amperometric, impedance, potentiometric or conductimetric) affinity biosensors due to their simplicity and sensitivity. Typically, electrochemical biosensors for mycotoxins use specific antibodies or aptamers as affinity ligands, although recombinant antibodies, artificial receptors and molecular imprinted polymers show potential utility. This article deals with recent advances in electrochemical affinity biosensors for mycotoxins and covers complete literature from the first reports about sixteen years ago.

  10. Protein electrochemistry using graphene-based nano-assembly: an ultrasensitive electrochemical detection of protein molecules via nanoparticle-electrode collisions.

    PubMed

    Li, Da; Liu, Jingquan; Barrow, Colin J; Yang, Wenrong

    2014-08-01

    We describe a new electrochemical detection approach towards single protein molecules (microperoxidase-11, MP-11), which are attached to the surface of graphene nanosheets. The non-covalently functionalized graphene nanosheets exhibit enhanced electroactive surface area, where amplified redox current is produced when graphene nanosheets collide with the electrode.

  11. CD/AuNPs/MWCNTs based electrochemical sensor for quercetin dual-signal detection.

    PubMed

    Kan, Xianwen; Zhang, Tingting; Zhong, Min; Lu, Xiaojing

    2016-03-15

    A dual-signal strategy was developed in the present work for quercetin (QR) electrochemical recognition and detection. Mercapto-β-cyclodextrin (HS-β-CD) self-assembled on gold nanoparticles and multi-walled carbon nanotubes modified electrode surface to fabricate an electrochemical sensor. Scanning electron microscope, electrochemical impedance spectroscopy, and cyclic voltammetry were employed to characterize the preparation process of the sensor. Hydroquinone (HQ) was chosen as an electrochemical marker for QR detection due to its small molecular size for the formation of inclusion with HS-β-CD. The results of UV-vis and differential pulse voltammetry demonstrate that the added QR can replace the included HQ in CD cavities, resulting in the dual-signal in electrochemical experiments composed of the decrease of oxidized current of HQ and the increase of oxidized current of QR. Compared with the sensor for QR detection in the absence of HQ, the sensor based dual-signal strategy exhibited a higher sensitivity with a wider detection range from 5.0 × 10(-9) to 7.0 × 10(-6)mol/L. With good selectivity, reproducibility, and stability, the sensor was applied for real samples detection with satisfactory results. The proposed dual-signal strategy can be readily extended to the selective recognition and sensitive detection of other molecules.

  12. Electrochemical detection for dynamic analyses of a redox component in droplets using a local redox cycling-based electrochemical (LRC-EC) chip device.

    PubMed

    Ino, Kosuke; Kanno, Yusuke; Nishijo, Taku; Goto, Takehito; Arai, Toshiharu; Takahashi, Yasufumi; Shiku, Hitoshi; Matsue, Tomokazu

    2012-09-01

    This report describes the electrochemical detection of a redox component in droplets using a local redox cycling-based electrochemical (LRC-EC) chip device consisting of 256 sensors. The time-course analyses showed that the redox compound in the droplet was dynamically changed during droplet evaporation or mass transfer through a water/oil interface.

  13. Amorphous ruthenium nanoparticles for enhanced electrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Tee, Si Yin; Lee, Coryl Jing Jun; Safari Dinachali, Saman; Lai, Szu Cheng; Williams, Evan Laurence; Luo, He-Kuan; Chi, Dongzhi; Hor, T. S. Andy; Han, Ming-Yong

    2015-10-01

    This paper demonstrates an optimized fabrication of amorphous Ru nanoparticles through annealing at various temperatures ranging from 150 to 700 °C, which are used as water oxidation catalyst for effective electrochemical water splitting under a low overpotential of less than 300 mV. The amorphous Ru nanoparticles with short-range ordered structure exhibit an optimal and stable electrocatalytic activity after annealing at 250 °C. Interestingly, a small quantity of such Ru nanoparticles in a thin film on fluorine-doped tin oxide glass is also effectively driven by a conventional crystalline silicon solar cell that has excellent capability for harvesting visible light. Remarkably, it achieves an overall solar-to-hydrogen efficiency of 11.3% in acidic electrolyte.

  14. Amorphous ruthenium nanoparticles for enhanced electrochemical water splitting.

    PubMed

    Tee, Si Yin; Lee, Coryl Jing Jun; Dinachali, Saman Safari; Lai, Szu Cheng; Williams, Evan Laurence; Luo, He-Kuan; Chi, Dongzhi; Andy Hor, T S; Han, Ming-Yong

    2015-10-16

    This paper demonstrates an optimized fabrication of amorphous Ru nanoparticles through annealing at various temperatures ranging from 150 to 700 °C, which are used as water oxidation catalyst for effective electrochemical water splitting under a low overpotential of less than 300 mV. The amorphous Ru nanoparticles with short-range ordered structure exhibit an optimal and stable electrocatalytic activity after annealing at 250 °C. Interestingly, a small quantity of such Ru nanoparticles in a thin film on fluorine-doped tin oxide glass is also effectively driven by a conventional crystalline silicon solar cell that has excellent capability for harvesting visible light. Remarkably, it achieves an overall solar-to-hydrogen efficiency of 11.3% in acidic electrolyte. PMID:26404046

  15. Enhanced photocatalytic activity of electrochemically synthesized aluminum oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Pathania, Deepak; Katwal, Rishu; Kaur, Harpreet

    2016-03-01

    In this study, aluminum oxide (Al2O3) nanoparticles (NPs) were synthesized via an electrochemical method. The effects of reaction parameters such as supporting electrolytes, solvent, current and electrolysis time on the shape and size of the resulting NPs were investigated. The Al2O3 NPs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, thermogravimetric analysis/differential thermal analysis, energy-dispersive X-ray analysis, and ultraviolet-visible spectroscopy. Moreover, the Al2O3 NPs were explored for photocatalytic degradation of malachite green (MG) dye under sunlight irradiation via two processes: adsorption followed by photocatalysis; coupled adsorption and photocatalysis. The coupled process exhibited a higher photodegradation efficiency (45%) compared to adsorption followed by photocatalysis (32%). The obtained kinetic data was well fitted using a pseudo-first-order model for MG degradation.

  16. Electrochemical Patterning and Detection of DNA Arrays on a Two-Electrode Platform

    PubMed Central

    Furst, Ariel; Landefeld, Sally; Hill, Michael G.; Barton, Jacqueline K.

    2014-01-01

    We report a novel method of DNA array formation that is electrochemically formed and addressed with a two-electrode platform. Electrochemical activation of a copper catalyst, patterned with one electrode, enables precise placement of multiple sequences of DNA onto a second electrode surface. The two-electrode patterning and detection platform allows for both spatial resolution of the patterned DNA array and optimization of detection through DNA-mediated charge transport with electrocatalysis. This two-electrode platform has been used to form arrays that enable differentiation between well-matched and mismatched sequences, the detection of TATA-binding protein, and sequence-selective DNA hybridization. PMID:24328227

  17. Electrochemical patterning and detection of DNA arrays on a two-electrode platform.

    PubMed

    Furst, Ariel; Landefeld, Sally; Hill, Michael G; Barton, Jacqueline K

    2013-12-26

    We report a novel method of DNA array formation that is electrochemically formed and addressed with a two-electrode platform. Electrochemical activation of a copper catalyst, patterned with one electrode, enables precise placement of multiple sequences of DNA onto a second electrode surface. The two-electrode patterning and detection platform allows for both spatial resolution of the patterned DNA array and optimization of detection through DNA-mediated charge transport with electrocatalysis. This two-electrode platform has been used to form arrays that enable differentiation between well-matched and mismatched sequences, the detection of TATA-binding protein, and sequence-selective DNA hybridization. PMID:24328227

  18. A nitrogen-doped graphene/carbon nanotube nanocomposite with synergistically enhanced electrochemical activity.

    PubMed

    Chen, Ping; Xiao, Tian-Yuan; Qian, Yu-Hong; Li, Shan-Shan; Yu, Shu-Hong

    2013-06-18

    A new kind of nitrogen-doped graphene/carbon nanotube nanocomposite can be synthesized by a facile hydrothermal process under mild conditions, which exhibits synergistically enhanced electrochemical activity for the oxygen reduction reaction. This research provides a new route to access a metal-free electrocatalyst with high activity under mild conditions.

  19. Dual detection of nitrate and mercury in water using disposable electrochemical sensors.

    PubMed

    Bui, Minh-Phuong N; Brockgreitens, John; Ahmed, Snober; Abbas, Abdennour

    2016-11-15

    Here we report a disposable, cost effective electrochemical paper-based sensor for the detection of both nitrate and mercury ions in lake water and contaminated agricultural runoff. Disposable carbon paper electrodes were functionalized with selenium particles (SePs) and gold nanoparticles (AuNPs). The AuNPs served as a catalyst for the reduction of nitrate ions using differential pulse voltammetry techniques. The AuNPs also served as a nucleation sites for mercury ions. The SePs further reinforced this mercury ion nucleation due to their high binding affinity to mercury. Differential pulse stripping voltammetry techniques were used to further enhance mercury ion accumulation on the modified electrode. The fabricated electrode was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemistry techniques. The obtained results show that the PEG-SH/SePs/AuNPs modified carbon paper electrode has a dual functionality in that it can detect both nitrate and mercury ions without any interference. The modified carbon paper electrode has improved the analytical sensitivity of nitrate and mercury ions with limits of detection of 8.6µM and 1.0ppb, respectively. Finally, the modified electrode was used to measure nitrate and mercury in lake water samples. PMID:27183277

  20. Synthesis of Au/Graphene Oxide Composites for Selective and Sensitive Electrochemical Detection of Ascorbic Acid

    PubMed Central

    Song, Jian; Xu, Lin; Xing, Ruiqing; Li, Qingling; Zhou, Chunyang; Liu, Dali; Song, Hongwei

    2014-01-01

    In this work, we present a novel ascorbic acid (AA) sensor applied to the detection of AA in human sera and pharmaceuticals. A series of Au nanoparticles (NPs) and graphene oxide sheets (Au NP/GO) composites were successfully synthesized by reduction of gold (III) using sodium citrate. Then the Au NP/GO composites were used to construct nonenzymatic electrodes in practical AA measurement. The electrode that has the best performance presents attractive analytical features, such as a low working potential of +0.15 V, a high sensitivity of 101.86 μA mM−1 cm−2 to AA, a low detection limit of 100 nM, good reproducibility and excellent selectivity. And more,it was also employed to accurately and practically detect AA in human serum and clinical vitamin C tablet with the existence of some food additive. The enhanced AA electrochemical properties of the Au NP/GO modified electrode in our work can be attributed to the improvement of electroactive surface area of Au NPs and the synergistic effect from the combination of Au NPs and GO sheets. This work shows that the Au NP/GO/GCEs hold the prospect for sensitive and selective determination of AA in practical clinical application. PMID:25515430

  1. Synthesis of Au/Graphene Oxide Composites for Selective and Sensitive Electrochemical Detection of Ascorbic Acid

    NASA Astrophysics Data System (ADS)

    Song, Jian; Xu, Lin; Xing, Ruiqing; Li, Qingling; Zhou, Chunyang; Liu, Dali; Song, Hongwei

    2014-12-01

    In this work, we present a novel ascorbic acid (AA) sensor applied to the detection of AA in human sera and pharmaceuticals. A series of Au nanoparticles (NPs) and graphene oxide sheets (Au NP/GO) composites were successfully synthesized by reduction of gold (III) using sodium citrate. Then the Au NP/GO composites were used to construct nonenzymatic electrodes in practical AA measurement. The electrode that has the best performance presents attractive analytical features, such as a low working potential of +0.15 V, a high sensitivity of 101.86 μA mM-1 cm-2 to AA, a low detection limit of 100 nM, good reproducibility and excellent selectivity. And more,it was also employed to accurately and practically detect AA in human serum and clinical vitamin C tablet with the existence of some food additive. The enhanced AA electrochemical properties of the Au NP/GO modified electrode in our work can be attributed to the improvement of electroactive surface area of Au NPs and the synergistic effect from the combination of Au NPs and GO sheets. This work shows that the Au NP/GO/GCEs hold the prospect for sensitive and selective determination of AA in practical clinical application.

  2. Aptamer-based electrochemical approach to the detection of thrombin by modification of gold nanoparticles.

    PubMed

    Li, Lidong; Zhao, Hongtao; Chen, Zhengbo; Mu, Xiaojiao; Guo, Lin

    2010-09-01

    This paper presents a simple electrochemical approach for the detection of thrombin, using aptamer-modified electrodes. The use of gold nanoparticles results in significant signal enhancement for subsequent detection. 1,6-Hexanedithiol was used as the medium to link Au nanoparticles to a bare gold electrode. Anti-thrombin aptamers were immobilized on the gold nanoparticles' surfaces by self-assembly. The packing density of aptamers was determined by cyclic voltammetric (CV) studies of redox cations (e.g., [Ru(NH(3))(6)](3+)) which were electrostatically bound to the DNA phosphate backbones. The results indicate that the total amount of aptamer probes immobilized on the gold nanoparticle surface is sixfold higher than that on the bare electrode, leading to increased sensitivity of the aptasensor and a detection limit of 1 pmol L(-1). Based on the Langmuir model, the sensor signal displayed an almost perfect linear relationship over the range of 1 pmol L(-1) to 30 nmol L(-1). Moreover, the proposed aptasensor is highly selective and stable. In summary, this biosensor is simple, highly sensitive, and selective, which is beneficial to the ever-growing interest in fabricating portable bio-analytical devices with simple electrical readout procedures.

  3. Synthesis of Au/graphene oxide composites for selective and sensitive electrochemical detection of ascorbic acid.

    PubMed

    Song, Jian; Xu, Lin; Xing, Ruiqing; Li, Qingling; Zhou, Chunyang; Liu, Dali; Song, Hongwei

    2014-01-01

    In this work, we present a novel ascorbic acid (AA) sensor applied to the detection of AA in human sera and pharmaceuticals. A series of Au nanoparticles (NPs) and graphene oxide sheets (Au NP/GO) composites were successfully synthesized by reduction of gold (III) using sodium citrate. Then the Au NP/GO composites were used to construct nonenzymatic electrodes in practical AA measurement. The electrode that has the best performance presents attractive analytical features, such as a low working potential of +0.15 V, a high sensitivity of 101.86 μA mM(-1) cm(-2) to AA, a low detection limit of 100 nM, good reproducibility and excellent selectivity. And more,it was also employed to accurately and practically detect AA in human serum and clinical vitamin C tablet with the existence of some food additive. The enhanced AA electrochemical properties of the Au NP/GO modified electrode in our work can be attributed to the improvement of electroactive surface area of Au NPs and the synergistic effect from the combination of Au NPs and GO sheets. This work shows that the Au NP/GO/GCEs hold the prospect for sensitive and selective determination of AA in practical clinical application. PMID:25515430

  4. Synthesis of Au/graphene oxide composites for selective and sensitive electrochemical detection of ascorbic acid.

    PubMed

    Song, Jian; Xu, Lin; Xing, Ruiqing; Li, Qingling; Zhou, Chunyang; Liu, Dali; Song, Hongwei

    2014-12-17

    In this work, we present a novel ascorbic acid (AA) sensor applied to the detection of AA in human sera and pharmaceuticals. A series of Au nanoparticles (NPs) and graphene oxide sheets (Au NP/GO) composites were successfully synthesized by reduction of gold (III) using sodium citrate. Then the Au NP/GO composites were used to construct nonenzymatic electrodes in practical AA measurement. The electrode that has the best performance presents attractive analytical features, such as a low working potential of +0.15 V, a high sensitivity of 101.86 μA mM(-1) cm(-2) to AA, a low detection limit of 100 nM, good reproducibility and excellent selectivity. And more,it was also employed to accurately and practically detect AA in human serum and clinical vitamin C tablet with the existence of some food additive. The enhanced AA electrochemical properties of the Au NP/GO modified electrode in our work can be attributed to the improvement of electroactive surface area of Au NPs and the synergistic effect from the combination of Au NPs and GO sheets. This work shows that the Au NP/GO/GCEs hold the prospect for sensitive and selective determination of AA in practical clinical application.

  5. Dual detection of nitrate and mercury in water using disposable electrochemical sensors.

    PubMed

    Bui, Minh-Phuong N; Brockgreitens, John; Ahmed, Snober; Abbas, Abdennour

    2016-11-15

    Here we report a disposable, cost effective electrochemical paper-based sensor for the detection of both nitrate and mercury ions in lake water and contaminated agricultural runoff. Disposable carbon paper electrodes were functionalized with selenium particles (SePs) and gold nanoparticles (AuNPs). The AuNPs served as a catalyst for the reduction of nitrate ions using differential pulse voltammetry techniques. The AuNPs also served as a nucleation sites for mercury ions. The SePs further reinforced this mercury ion nucleation due to their high binding affinity to mercury. Differential pulse stripping voltammetry techniques were used to further enhance mercury ion accumulation on the modified electrode. The fabricated electrode was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemistry techniques. The obtained results show that the PEG-SH/SePs/AuNPs modified carbon paper electrode has a dual functionality in that it can detect both nitrate and mercury ions without any interference. The modified carbon paper electrode has improved the analytical sensitivity of nitrate and mercury ions with limits of detection of 8.6µM and 1.0ppb, respectively. Finally, the modified electrode was used to measure nitrate and mercury in lake water samples.

  6. A regenerated electrochemical biosensor for label-free detection of glucose and urea based on conformational switch of i-motif oligonucleotide probe.

    PubMed

    Gao, Zhong Feng; Chen, Dong Mei; Lei, Jing Lei; Luo, Hong Qun; Li, Nian Bing

    2015-10-15

    Improving the reproducibility of electrochemical signal remains a great challenge over the past decades. In this work, i-motif oligonucleotide probe-based electrochemical DNA (E-DNA) sensor is introduced for the first time as a regenerated sensing platform, which enhances the reproducibility of electrochemical signal, for label-free detection of glucose and urea. The addition of glucose or urea is able to activate glucose oxidase-catalyzed or urease-catalyzed reaction, inducing or destroying the formation of i-motif oligonucleotide probe. The conformational switch of oligonucleotide probe can be recorded by electrochemical impedance spectroscopy. Thus, the difference of electron transfer resistance is utilized for the quantitative determination of glucose and urea. We further demonstrate that the E-DNA sensor exhibits high selectivity, excellent stability, and remarkable regenerated ability. The human serum analysis indicates that this simple and regenerated strategy holds promising potential in future biosensing applications.

  7. A regenerated electrochemical biosensor for label-free detection of glucose and urea based on conformational switch of i-motif oligonucleotide probe.

    PubMed

    Gao, Zhong Feng; Chen, Dong Mei; Lei, Jing Lei; Luo, Hong Qun; Li, Nian Bing

    2015-10-15

    Improving the reproducibility of electrochemical signal remains a great challenge over the past decades. In this work, i-motif oligonucleotide probe-based electrochemical DNA (E-DNA) sensor is introduced for the first time as a regenerated sensing platform, which enhances the reproducibility of electrochemical signal, for label-free detection of glucose and urea. The addition of glucose or urea is able to activate glucose oxidase-catalyzed or urease-catalyzed reaction, inducing or destroying the formation of i-motif oligonucleotide probe. The conformational switch of oligonucleotide probe can be recorded by electrochemical impedance spectroscopy. Thus, the difference of electron transfer resistance is utilized for the quantitative determination of glucose and urea. We further demonstrate that the E-DNA sensor exhibits high selectivity, excellent stability, and remarkable regenerated ability. The human serum analysis indicates that this simple and regenerated strategy holds promising potential in future biosensing applications. PMID:26515000

  8. Deconstructing multisensory enhancement in detection

    PubMed Central

    Pérez-Bellido, Alexis; Pereda-Baños, Alexandre; López-Moliner, Joan; Deco, Gustavo; Soto-Faraco, Salvador

    2014-01-01

    The mechanisms responsible for the integration of sensory information from different modalities have become a topic of intense interest in psychophysics and neuroscience. Many authors now claim that early, sensory-based cross-modal convergence improves performance in detection tasks. An important strand of supporting evidence for this claim is based on statistical models such as the Pythagorean model or the probabilistic summation model. These models establish statistical benchmarks representing the best predicted performance under the assumption that there are no interactions between the two sensory paths. Following this logic, when observed detection performances surpass the predictions of these models, it is often inferred that such improvement indicates cross-modal convergence. We present a theoretical analyses scrutinizing some of these models and the statistical criteria most frequently used to infer early cross-modal interactions during detection tasks. Our current analysis shows how some common misinterpretations of these models lead to their inadequate use and, in turn, to contradictory results and misleading conclusions. To further illustrate the latter point, we introduce a model that accounts for detection performances in multimodal detection tasks but for which surpassing of the Pythagorean or probabilistic summation benchmark can be explained without resorting to early cross-modal interactions. Finally, we report three experiments that put our theoretical interpretation to the test and further propose how to adequately measure multimodal interactions in audiotactile detection tasks. PMID:25520431

  9. DNA Enzyme-Decorated DNA Nanoladders as Enhancer for Peptide Cleavage-Based Electrochemical Biosensor.

    PubMed

    Kou, Bei-Bei; Zhang, Li; Xie, Hua; Wang, Ding; Yuan, Ya-Li; Chai, Ya-Qin; Yuan, Ruo

    2016-09-01

    Herein, we developed a label-free electrochemical biosensor for sensitive detection of matrix metalloproteinase-7 (MMP-7) based on DNA enzyme-decorated DNA nanoladders as enhancer. A peptide and single-stranded DNA S1-modified platinum nanoparticles (P1-PtNPs-S1), which served as recognition nanoprobes, were first immobilized on electrode. When target MMP-7 specifically recognized and cleaved the peptide, the PtNPs-S1 bioconjugates were successfully released from electrode. The remaining S1 on electrode then hybridized with ssDNA1 (I1) and ssDNA2 (I2), which could synchronously trigger two hybridization chain reactions (HCRs), resulting in the in situ formation of DNA nanoladders. The desired DNA nanoladders not only were employed as ideal nanocarriers for enzyme loading, but also maintained its catalytic activity. With the help of hydrogen peroxide (H2O2), manganese porphyrin (MnPP) with peroxidase-like activity accelerated the 4-chloro-1-naphthol (4-CN) oxidation with generation of insoluble precipitation on electrode, causing a very low differential pulse voltammetry (DPV) signal for quantitative determination of MMP-7. Under optimal conditions, the developed biosensor exhibited a wide linear ranging from 0.2 pg/mL to 20 ng/mL, and the detection limit was 0.05 pg/mL. This work successfully realized the combination of DNA signal amplification technique with artificial mimetic enzyme-catalyzed precipitation reaction in peptide cleavage-based protein detection, offering a promising avenue for the detection of other proteases. PMID:27532492

  10. Background current reduction and biobarcode amplification for label-free, highly sensitive electrochemical detection of pathogenic DNA.

    PubMed

    Xu, Jin; Jiang, Bingying; Su, Jiao; Xiang, Yun; Yuan, Ruo; Chai, Yaqin

    2012-04-01

    By using exonuclease I and biobarcode nanoparticles, we describe a novel background current reduction strategy for amplified electrochemical detection of uropathogen specific sequences at ultralow concentrations.

  11. Enhanced electrochemical supercapacitor properties with synergistic effect of polyaniline, graphene and AgxO

    NASA Astrophysics Data System (ADS)

    Usman, Muhammad; Pan, Lujun; Asif, Muhammad; Mahmood, Zafar; Khan, M. A.; Fu, Xin

    2016-05-01

    The graphene-Ag2O/polyaniline (GAP) composite has been synthesized by in-situ polymerization. It has been observed that Ag2O nanoparticles exist on the porous spongy background of PANI (polyaniline). The optimized composition of the synthesized composite exhibits an extraordinary specific capacitance of 1572 Fg-1 at 0.05 Ag-1 current density and good cyclic stability of 85% over 3000 charge-discharge cycles. The extraordinary electrochemical performance indicates the positive synergistic effect of PANI, graphene and Ag2O. The Ag2O nanoparticles might be responsible for improved electrical conductivity, and graphene might contribute in enhancing the electrochemical stability of the PANI electrode.

  12. Resolution enhanced sound detecting apparatus

    NASA Technical Reports Server (NTRS)

    Kendall, J. M. (Inventor)

    1979-01-01

    An apparatus is described for enhancing the resolution of a sound detector of the type which includes an acoustic mirror for focusing sound from an object onto a microphone to enable the determination of the location from which the sound arises. The enhancement apparatus includes an enclosure which surrounds the space between the mirror and microphone, and contains a gas heavier than air, such as Freon, through which sound moves slower and therefore with a shorter wavelength than in air, so that a mirror of given size has greater resolving power. An acoustically transparent front wall of the enclosure which lies forward of the mirror, can include a pair of thin sheets with pressured air between them, to form an end of the region of heavy gas into a concave shape.

  13. [Trace analysis of biological substances by high-performance liquid chromatography with electrochemical detection].

    PubMed

    Shimada, K; Oe, T

    1991-01-01

    High-performance liquid chromatography (HPLC) with electrochemical detection has been developed for the trace analysis of electrochemically active substances in biological fluids such as catecholamines. The recent development of this system, both instruments and application, has been reviewed. The principle of instrument and newly developed electrode for electrochemical detector have been described at the first section. Series electrodes, especially with coulometric detection, gave much higher selectivity to the analysis of biological substances. The application of HPLC with electrochemical detection to the determination of estrogens in biological fluids clarified the metabolic pathway of catechol estrogens. The applicability to the determination of vitamin D3 and related compounds has been also suggested. For the purpose of extending the applicability of HPLC with electrochemical detection to electro-inactive compounds, pre- and post-column labeling methods have been developed. Pre-column derivatization reagents possessing ferrocene as an electrophore provided a selective and sensitive response to the detector, because of their high-reversibility and low applied potential in the redox reaction. Post-column reaction by using immobilized enzyme reactor has been widely used for the determination of acetylcholine and choline in biological fluids.

  14. Acoustic enhancement for photo detecting devices

    DOEpatents

    Thundat, Thomas G; Senesac, Lawrence R; Van Neste, Charles W

    2013-02-19

    Provided are improvements to photo detecting devices and methods for enhancing the sensitivity of photo detecting devices. A photo detecting device generates an electronic signal in response to a received light pulse. An electro-mechanical acoustic resonator, electrically coupled to the photo detecting device, damps the electronic signal and increases the signal noise ratio (SNR) of the electronic signal. Increased photo detector standoff distances and sensitivities will result.

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

    NASA Astrophysics Data System (ADS)

    Ahmadalinezhad, Asieh

    properties, we fabricated a highly sensitive and mediator-free electrochemical biosensor for the determination of total cholesterol. The developed biosensor possessed high selectivity and sensitivity (29.33 microA mM--1cm --2). The apparent Michaelis--Menten constant, KappM of this biosensor was very low (0.64 mM), which originated from both the effective immobilization process and the nanoporous structure of the substrate. The biosensor exhibited a wide linear range, up to 300 mg dL--1 , in a physiological environment (pH 7.4); making it a promising candidate for the clinical determination of cholesterol. The fabricated biosensor was tested further by utilizing actual food samples (e.g., margarine, butter and fish oil). The results indicated that it has the potential capacity to be employed as a facile cholesterol detection tool in the food industry and for supplement quality control. To enhance the stability of the biosensors in the continuous monitoring of glucose, we designed a novel platform that was based on buckypaper. The fabricated biosensor responded to glucose with a considerable functional lifetime of over 80 days and detected glucose with a dynamic linear range of over 9 mM with a detection limit of 0.01 mM. To investigate the effects of the physical dimensions of nanomaterials on electrochemical biosensing, we synthesized TiO2 nanowires with controllable dimensions via a facile thermal oxidation treatment of a Ti substrate. To improve the conductivity of the TiO2 nanowires and to facilitate the immobilization of enzymes, a thin layer of carbon was deposited onto the TiO2 nanowires via a chemical vapour deposition method. Upon the immobilization of glucose oxidase as a model protein, direct electron transfer was observed in a mediator-free biosensing environment. Our electrochemical studies have revealed that the electron transfer rate of the immobilized glucose oxidase is strongly dependent on the dimensions of the carbonized TiO 2 nanowires, and that the

  16. Development of Advanced Electrochemical Sensors for DNA Detection at the Point of Care

    NASA Astrophysics Data System (ADS)

    Hsieh, Kuangwen

    In the post-genomic era, ever-advancing capabilities in DNA detection and analysis have become vital to the detection of infectious diseases and the diagnosis of genetic abnormalities and inheritable diseases. The benefit of such capabilities, however, has yet to reach patients outside of centralized facilities. There thus exists an increasing need to decentralize DNA detection methods and to administer such diagnostics at the "point of care." Electrochemical-based DNA sensors present a compelling approach, but have yet to deliver satisfactory sensitivity, specificity, miniaturization, and real-time monitoring capability to meet the demand of point-of-care diagnostics. Motivated by their potential and their current limitations, in this dissertation, we present a series of strategies that we have undertaken in order to address the key shortcomings of electrochemical DNA sensors and advance them toward point-of-care applications. First, we report a single-step, single reagent, label-free, isothermal electrochemical DNA sensor based on the phenomenon of enzyme catalyzed target recycling amplification. Using this technique, we achieve improved detection limit in comparison to hybridization-based sensors without amplification. We also demonstrate greater than 16-fold amplification of signal at low target concentrations. Next, we present a novel electrochemical DNA sensor that detects single-nucleotide mismatched targets with unprecedented "polarity-switching" responses. This "bipolar" sensor employs a surface-bound and redox-modified (methylene blue) DNA probe architecture, and outputs a decreased Faradaic current when hybridized to a perfectly matched (PM) target, but conversely reports an increased Faradaic current when hybridized to a single-base mismatched (SM) target. Third, we describe the microfluidic electrochemical dynamic allele specific hybridization (microE-DASH) platform for versatile and rapid detection of single-nucleotide polymorphisms. Implementing

  17. Sensitive electrochemical immunoassay with signal enhancement based on nanogold-encapsulated poly(amidoamine) dendrimer-stimulated hydrogen evolution reaction.

    PubMed

    Sun, Ai-Li

    2015-12-01

    A new electrochemical immunosensor with signal enhancement was designed for sensitive detection of disease-related protein (human carbohydrate antigen 19-9, CA 19-9 used in this case). The assay was carried out on a capture antibody-modified screen-printed carbon electrode with a sandwich-type mode by using detection antibody-functionalized nanogold-encapsulated poly(amidoamine) dendrimer (AuNP-PAAD). The AuNP-PAAD was first synthesized through the in situ reduction method and functionalized with the polyclonal rabbit anti-human CA 19-9 antibody. Upon target CA 19-9 introduction, a sandwiched immunocomplex could be formed between the capture antibody and detection antibody. Accompanying the AuNP-PAAD, the electrocatalytic activity of the carried gold nanoparticles toward the hydrogen evolution reaction (HER) allowed the rapid quantification of the target analyte on the electrode. The amplified electrochemical signal mainly derived from AuNP-catalyzed HER in an acidic medium. Under optimal conditions, the immuno-HER assay displayed a wide dynamic concentration range from 0.01 to 300 U mL(-1) toward target CA 19-9 with a detection limit (LOD) of 6.3 mU mL(-1). The reproducibility, precision, specificity and stability of our strategy were acceptable. Additionally, the system was further validated by assaying 13 human serum specimens, giving well matched results obtained from the commercialized enzyme-linked immunosorbent assay (ELISA) method.

  18. Enhanced electrochemical performance of monoclinic WO3 thin film with redox additive aqueous electrolyte.

    PubMed

    Shinde, Pragati A; Lokhande, Vaibhav C; Chodankar, Nilesh R; Ji, Taeksoo; Kim, Jin Hyeok; Lokhande, Chandrakant D

    2016-12-01

    To achieve the highest electrochemical performance for supercapacitor, it is very essential to find out a suitable pair of an active electrode material and an electrolyte. In the present work, a simple approach is employed to enhance the supercapacitor performance of WO3 thin film. The WO3 thin film is prepared by a simple and cost effective chemical bath deposition method and its electrochemical performance is tested in conventional (H2SO4) and redox additive [H2SO4+hydroquinone (HQ)] electrolytes. Two-fold increment in electrochemical performance for WO3 thin film is observed in redox additive aqueous electrolyte compared to conventional electrolyte. WO3 thin film showed maximum specific capacitance of 725Fg(-1), energy density of 25.18Whkg(-1) at current density of 7mAcm(-2) with better cycling stability in redox electrolyte. This strategy provides the versatile way for designing the high performance energy storage devices.

  19. Enhanced electrochemical performance of monoclinic WO3 thin film with redox additive aqueous electrolyte.

    PubMed

    Shinde, Pragati A; Lokhande, Vaibhav C; Chodankar, Nilesh R; Ji, Taeksoo; Kim, Jin Hyeok; Lokhande, Chandrakant D

    2016-12-01

    To achieve the highest electrochemical performance for supercapacitor, it is very essential to find out a suitable pair of an active electrode material and an electrolyte. In the present work, a simple approach is employed to enhance the supercapacitor performance of WO3 thin film. The WO3 thin film is prepared by a simple and cost effective chemical bath deposition method and its electrochemical performance is tested in conventional (H2SO4) and redox additive [H2SO4+hydroquinone (HQ)] electrolytes. Two-fold increment in electrochemical performance for WO3 thin film is observed in redox additive aqueous electrolyte compared to conventional electrolyte. WO3 thin film showed maximum specific capacitance of 725Fg(-1), energy density of 25.18Whkg(-1) at current density of 7mAcm(-2) with better cycling stability in redox electrolyte. This strategy provides the versatile way for designing the high performance energy storage devices. PMID:27565957

  20. Selective Electrochemical Detection of Ciprofloxacin with a Porous Nafion/Multiwalled Carbon Nanotube Composite Film Electrode.

    PubMed

    Gayen, Pralay; Chaplin, Brian P

    2016-01-27

    This study focuses on the development of electrochemical sensors for the detection of Ciprofloxacin (CFX) in natural waters and wastewater effluents. The sensors are prepared by depositing a layer of multiwalled carbon nanotubes (MWCNTs) dispersed in a porous Nafion film on to a boron-doped diamond (BDD) electrode substrate. The porous-Nafion-MWCNT/BDD electrode enhanced detection of CFX due to selective adsorption, which was accomplished by a combination of electrostatic attraction at -SO3(-) sites in the porous Nafion film and the formation of charge assisted hydrogen bonding between CFX and -COOH MWCNT surface functional groups. By contrast, the bare BDD electrode did not show any activity for CFX oxidation. The sensors were selective for CFX detection in the presence of other antibiotics (i.e., amoxicillin) and other nontarget water constituents (i.e., Cl(-), Ca(2+), humic acid, sodium dodecylbenzenesulfonate, salicylic acid, 4-aminobenzoic acid, and 4-hydroxybenzoic acid). A limit of detection of 5 nM (S/N = 5.04 ± 0.26) in a 0.1 M KH2PO4 supporting electrolyte (pH = 4.5) was obtained using differential pulse voltammetry. The linear dynamic ranges with respect to CFX concentration were 0.005-0.05 μM and 0.05-10 μM, and the sensitivities were 41 ± 5.2 μA μM(-1) and 2.1 ± 0.22 μA μM(-1), respectively. Sensor fouling was observed at high concentrations of some organic compounds such as 1 mM 4-aminobenzoic acid and 4-hydroxybenzoic acid. However, a short cathodic treatment fully restores sensor response. The results indicate that these sensors have application in detecting CFX in natural waters and wastewater effluents. PMID:26711553

  1. Selective Electrochemical Detection of Ciprofloxacin with a Porous Nafion/Multiwalled Carbon Nanotube Composite Film Electrode.

    PubMed

    Gayen, Pralay; Chaplin, Brian P

    2016-01-27

    This study focuses on the development of electrochemical sensors for the detection of Ciprofloxacin (CFX) in natural waters and wastewater effluents. The sensors are prepared by depositing a layer of multiwalled carbon nanotubes (MWCNTs) dispersed in a porous Nafion film on to a boron-doped diamond (BDD) electrode substrate. The porous-Nafion-MWCNT/BDD electrode enhanced detection of CFX due to selective adsorption, which was accomplished by a combination of electrostatic attraction at -SO3(-) sites in the porous Nafion film and the formation of charge assisted hydrogen bonding between CFX and -COOH MWCNT surface functional groups. By contrast, the bare BDD electrode did not show any activity for CFX oxidation. The sensors were selective for CFX detection in the presence of other antibiotics (i.e., amoxicillin) and other nontarget water constituents (i.e., Cl(-), Ca(2+), humic acid, sodium dodecylbenzenesulfonate, salicylic acid, 4-aminobenzoic acid, and 4-hydroxybenzoic acid). A limit of detection of 5 nM (S/N = 5.04 ± 0.26) in a 0.1 M KH2PO4 supporting electrolyte (pH = 4.5) was obtained using differential pulse voltammetry. The linear dynamic ranges with respect to CFX concentration were 0.005-0.05 μM and 0.05-10 μM, and the sensitivities were 41 ± 5.2 μA μM(-1) and 2.1 ± 0.22 μA μM(-1), respectively. Sensor fouling was observed at high concentrations of some organic compounds such as 1 mM 4-aminobenzoic acid and 4-hydroxybenzoic acid. However, a short cathodic treatment fully restores sensor response. The results indicate that these sensors have application in detecting CFX in natural waters and wastewater effluents.

  2. Rapid Electrochemical Detection and Identification of Microbiological and Chemical Contaminants for Manned Spaceflight Project

    NASA Technical Reports Server (NTRS)

    Pierson, Duane; Botkin, Douglas; Gazda, Daniel

    2014-01-01

    Microbial control in the spacecraft environment is a daunting task, especially in the presence of human crew members. Currently, assessing the potential crew health risk associated with a microbial contamination event requires return of representative environmental samples that are analyzed in a ground-based laboratory. It is therefore not currently possible to quickly identify microbes during spaceflight. This project addresses the unmet need for spaceflight-compatible microbial identification technology. The electrochemical detection and identification platform is expected to provide a sensitive, specific, and rapid sample-to-answer capability for in-flight microbial monitoring that can distinguish between related microorganisms (pathogens and non-pathogens) as well as chemical contaminants. This will dramatically enhance our ability to monitor the spacecraft environment and the health risk to the crew. Further, the project is expected to eliminate the need for sample return while significantly reducing crew time required for detection of multiple targets. Initial work will focus on the optimization of bacterial detection and identification. The platform is designed to release nucleic acids (DNA and RNA) from microorganisms without the use of harmful chemicals. Bacterial DNA or RNA is captured by bacteria-specific probe molecules that are bound to a microelectrode, and that capture event can generate a small change in the electrical current (Lam, et al. 2012. Anal. Chem. 84(1): 21-5.). This current is measured, and a determination is made whether a given microbe is present in the sample analyzed. Chemical detection can be accomplished by directly applying a sample to the microelectrode and measuring the resulting current change. This rapid microbial and chemical detection device is designed to be a low-cost, low-power platform anticipated to be operated independently of an external power source, characteristics optimal for manned spaceflight and areas where power

  3. Hetero-enzyme-based two-round signal amplification strategy for trace detection of aflatoxin B1 using an electrochemical aptasensor.

    PubMed

    Zheng, Wanli; Teng, Jun; Cheng, Lin; Ye, Yingwang; Pan, Daodong; Wu, Jingjing; Xue, Feng; Liu, Guodong; Chen, Wei

    2016-06-15

    An electrochemical aptasensor for trace detection of aflatoxin B1 (AFB1) was developed by using an aptamer as the recognition unit while adopting the telomerase and EXO III based two-round signal amplification strategy as the signal enhancement units. The telomerase amplification was used to elongate the ssDNA probes on the surface of gold nanoparticles, by which the signal response range of the signal-off model electrochemical aptasensor could be correspondingly enlarged. Then, the EXO III amplification was used to hydrolyze the 3'-end of the dsDNA after the recognition of target AFB1, which caused the release of bounded AFB1 into the sensing system, where it participated in the next recognition-sensing cycle. With this two-round signal amplified electrochemical aptasensor, target AFB1 was successfully measured at trace concentrations with excellent detection limit of 0.6*10(-4)ppt and satisfied specificity due to the excellent affinity of the aptamer against AFB1. Based on this designed two-round signal amplification strategy, both the sensing range and detection limit were greatly improved. This proposed ultrasensitive electrochemical aptasensor method was also validated by comparison with the classic instrumental methods. Importantly, this hetero-enzyme based two-round signal amplified electrochemical aptasensor offers a great promising protocol for ultrasensitive detection of AFB1 and other mycotoxins by replacing the core recognition sequence of the aptamer.

  4. Electrochemical impedance spectroscopy in chromatography paper and its application to latex bead detection

    NASA Astrophysics Data System (ADS)

    Iwahara, Shohei; Miki, Masashi; Hori, Fumitaka; Uno, Shigeyasu

    2014-01-01

    The principle of the quantitative immunochromatographic strip test (IST) is proposed. Electrochemical impedance spectroscopy is shown to be capable of detecting latex beads in chromatography paper, where latex beads can serve as a label in IST. Measurements to examine the impedance changes in the absence and presence of latex beads are conducted. In the presence of latex beads, an increase of 12.5% in the bulk solution resistance is observed. This indicates that the latex-bead-labeled antigen-antibody complex can be detected electrochemically by actual IST.

  5. Electrochemically reduced graphene oxide on silicon nanowire arrays for enhanced photoelectrochemical hydrogen evolution.

    PubMed

    Meng, Huan; Fan, Ke; Low, Jingxiang; Yu, Jiaguo

    2016-09-21

    Photoelectrochemical (PEC) water splitting into hydrogen and oxygen by sunlight is a promising approach to solve energy and environmental problems. In this work, silicon nanowire arrays (SiNWs) photocathodes decorated with reduced graphene oxide (rGO) for PEC water splitting were successfully prepared by a flexible and scalable electrochemical reduction method. The SiNWs photocathode with the optimized rGO decoration (SiNWs/rGO20) shows an enhanced activity with a much higher photocurrent density and significantly positive shift of onset potential compared to the bare SiNWs arrays for the hydrogen evolution reaction (HER). The enhanced PEC activity is ascribed to the high electrical conductivity of rGO and improved separation of the photogenerated charge carriers. This work not only demonstrates a facile, rapid and tunable electrochemical reduction method to produce rGO, but also exhibits an efficient protocol to enhance the PEC water splitting of silicon-based materials. PMID:27461187

  6. Electrochemically reduced graphene oxide on silicon nanowire arrays for enhanced photoelectrochemical hydrogen evolution.

    PubMed

    Meng, Huan; Fan, Ke; Low, Jingxiang; Yu, Jiaguo

    2016-09-21

    Photoelectrochemical (PEC) water splitting into hydrogen and oxygen by sunlight is a promising approach to solve energy and environmental problems. In this work, silicon nanowire arrays (SiNWs) photocathodes decorated with reduced graphene oxide (rGO) for PEC water splitting were successfully prepared by a flexible and scalable electrochemical reduction method. The SiNWs photocathode with the optimized rGO decoration (SiNWs/rGO20) shows an enhanced activity with a much higher photocurrent density and significantly positive shift of onset potential compared to the bare SiNWs arrays for the hydrogen evolution reaction (HER). The enhanced PEC activity is ascribed to the high electrical conductivity of rGO and improved separation of the photogenerated charge carriers. This work not only demonstrates a facile, rapid and tunable electrochemical reduction method to produce rGO, but also exhibits an efficient protocol to enhance the PEC water splitting of silicon-based materials.

  7. Gold-nanoparticle based electrochemical DNA sensor for the detection of fish pathogen Aphanomyces invadans.

    PubMed

    Kuan, Guan Chin; Sheng, Liew Pei; Rijiravanich, Patsamon; Marimuthu, Kasi; Ravichandran, Manickam; Yin, Lee Su; Lertanantawong, Benchaporn; Surareungchai, Werasak

    2013-12-15

    Epizootic ulcerative syndrome (EUS) is a devastating fish disease caused by the fungus, Aphanomyces invadans. Rapid diagnosis of EUS is needed to control and treat this highly invasive disease. The current diagnostic methods for EUS are labor intensive. We have developed a highly sensitive and specific electrochemical genosensor towards the 18S rRNA and internal transcribed spacer regions of A. invadans. Multiple layers of latex were synthesized with the help of polyelectrolytes, and labeled with gold nanoparticles to enhance sensitivity. The gold-latex spheres were functionalized with specific DNA probes. We describe here the novel application of this improved platform for detection of PCR product from real sample of A. invadans using a premix sandwich hybridization assay. The premix assay was easier, more specific and gave higher sensitivity of one log unit when compared to the conventional method of step-by-step hybridization. The limit of detection was 0.5 fM (4.99 zmol) of linear target DNA and 1 fM (10 amol) of PCR product. The binding positions of the probes to the PCR amplicons were optimized for efficient hybridization. Probes that hybridized close to the 5' or 3' terminus of the PCR amplicons gave the highest signal due to minimal steric hindrance for hybridization. The genosensor is highly suitable as a surveillance and diagnostic tool for EUS in the aquaculture industry.

  8. A Nanocoaxial-Based Electrochemical Sensor for the Detection of Cholera Toxin

    NASA Astrophysics Data System (ADS)

    Archibald, Michelle M.; Rizal, Binod; Connolly, Timothy; Burns, Michael J.; Naughton, Michael J.; Chiles, Thomas C.

    2015-03-01

    Sensitive, real-time detection of biomarkers is of critical importance for rapid and accurate diagnosis of disease for point of care (POC) technologies. Current methods do not allow for POC applications due to several limitations, including sophisticated instrumentation, high reagent consumption, limited multiplexing capability, and cost. Here, we report a nanocoaxial-based electrochemical sensor for the detection of bacterial toxins using an electrochemical enzyme-linked immunosorbent assay (ELISA) and differential pulse voltammetry (DPV). Proof-of-concept was demonstrated for the detection of cholera toxin (CT). The linear dynamic range of detection was 10 ng/ml - 1 μg/ml, and the limit of detection (LOD) was found to be 2 ng/ml. This level of sensitivity is comparable to the standard optical ELISA used widely in clinical applications. In addition to matching the detection profile of the standard ELISA, the nanocoaxial array provides a simple electrochemical readout and a miniaturized platform with multiplexing capabilities for the simultaneous detection of multiple biomarkers, giving the nanocoax a desirable advantage over the standard method towards POC applications. Sensitive, real-time detection of biomarkers is of critical importance for rapid and accurate diagnosis of disease for point of care (POC) technologies. Current methods do not allow for POC applications due to several limitations, including sophisticated instrumentation, high reagent consumption, limited multiplexing capability, and cost. Here, we report a nanocoaxial-based electrochemical sensor for the detection of bacterial toxins using an electrochemical enzyme-linked immunosorbent assay (ELISA) and differential pulse voltammetry (DPV). Proof-of-concept was demonstrated for the detection of cholera toxin (CT). The linear dynamic range of detection was 10 ng/ml - 1 μg/ml, and the limit of detection (LOD) was found to be 2 ng/ml. This level of sensitivity is comparable to the standard optical

  9. Alternate pulses of ultrasound and electricity enhanced electrochemical process for p-nitrophenol degradation.

    PubMed

    Xie, Fengchun; Xu, Yun; Xia, Kunyuan; Jia, Caixia; Zhang, Pin

    2016-01-01

    A novel alternated ultrasonic and electric pulse enhanced electrochemical process was developed and used for investigating its effectiveness on the degradation of p-nitrophenol (PNP) in an aqueous solution. The impacts of pulse mode, pH, cell voltage, supporting electrolyte concentration, ultrasonic power and the initial concentration of PNP on the performance of PNP degradation were evaluated. Possible pathway of PNP degradation in this system was proposed based on the intermediates identified by GC-MS. Experimental results showed that 94.1% of PNP could be removed at 2h in the dual-pulse ultrasound enhanced electrochemical (dual-pulse US-EC) process at mild operating conditions (i.e., pulse mode of electrochemical pulse time (TEC)=50 ms and ultrasonic pulse time (T US)=100 ms, initial pH of 3.0, cell voltage of 10 V, Na2SO4 concentration of 0.05 M, ultrasonic powder of 48.8 W and initial concentration of PNP of 100mg/L), compared with 89.0%, 58.9%, 2.4% in simultaneous ultrasound enhanced electrochemical (US-EC) process, pulsed electrochemical (EC) process and pulsed ultrasound (US), respectively. Moreover, energy used in the dual-pulse US-EC process was reduced by 50.4% as compared to the US-EC process. The degradation of PNP in the pulsed EC process, US-EC process and dual-pulse process followed pseudo-first-order kinetics. Therefore, the dual-pulse US-EC process was found to be a more effective technique for the degradation of PNP and would have a promising application in wastewater treatment.

  10. Alternate pulses of ultrasound and electricity enhanced electrochemical process for p-nitrophenol degradation.

    PubMed

    Xie, Fengchun; Xu, Yun; Xia, Kunyuan; Jia, Caixia; Zhang, Pin

    2016-01-01

    A novel alternated ultrasonic and electric pulse enhanced electrochemical process was developed and used for investigating its effectiveness on the degradation of p-nitrophenol (PNP) in an aqueous solution. The impacts of pulse mode, pH, cell voltage, supporting electrolyte concentration, ultrasonic power and the initial concentration of PNP on the performance of PNP degradation were evaluated. Possible pathway of PNP degradation in this system was proposed based on the intermediates identified by GC-MS. Experimental results showed that 94.1% of PNP could be removed at 2h in the dual-pulse ultrasound enhanced electrochemical (dual-pulse US-EC) process at mild operating conditions (i.e., pulse mode of electrochemical pulse time (TEC)=50 ms and ultrasonic pulse time (T US)=100 ms, initial pH of 3.0, cell voltage of 10 V, Na2SO4 concentration of 0.05 M, ultrasonic powder of 48.8 W and initial concentration of PNP of 100mg/L), compared with 89.0%, 58.9%, 2.4% in simultaneous ultrasound enhanced electrochemical (US-EC) process, pulsed electrochemical (EC) process and pulsed ultrasound (US), respectively. Moreover, energy used in the dual-pulse US-EC process was reduced by 50.4% as compared to the US-EC process. The degradation of PNP in the pulsed EC process, US-EC process and dual-pulse process followed pseudo-first-order kinetics. Therefore, the dual-pulse US-EC process was found to be a more effective technique for the degradation of PNP and would have a promising application in wastewater treatment. PMID:26384900

  11. Polyoxometalate-grafted graphene nanohybrid for electrochemical detection of hydrogen peroxide and glucose.

    PubMed

    Yang, MinHo; Kim, Dong Seok; Lee, Tae Jae; Lee, Seok Jae; Lee, Kyoung G; Choi, Bong Gill

    2016-04-15

    The electrochemical performances of electrochemical biosensors largely depend on electrode characteristics, such as size, composition, surface area, and electron and ion conductivities. Herein, highly efficient electrocatalytic polyoxometalate (POM) was directly deposited on polymeric ionic liquid (PIL)-functionalized reduced graphene oxide (rGO) in a simple manner. The nano-sized POM with PIL functional groups was uniformly distributed on the surface of rGO sheets. The unique nanostructure of the resultant POM-g-rGO nanohybrids enabled well-defined multiple redox reaction of POMs and rapid electron transfer. In particular, as-prepared nanohybrids demonstrated high electrocatalytic activity for the electrochemical detection of H2O2 and glucose molecules in flow-injection biosensor device with high sensitivity, rapid response time, and low detection limit. PMID:26828273

  12. Sensitive electrochemical detection of Salmonella with chitosan-gold nanoparticles composite film.

    PubMed

    Xiang, Cuili; Li, Ran; Adhikari, Bimalendu; She, Zhe; Li, Yongxin; Kraatz, Heinz-Bernhard

    2015-08-01

    An ultrasensitive electrochemical immunosensor for detection of Salmonella has been developed based on using high density gold nanoparticles (GNPs) well dispersed in chitosan hydrogel and modified glassy carbon electrode. The composite film has been oxidized in NaCl solution and used as a platform for the immobilization of capture antibody (Ab1) for biorecognition. After incubation in Salmonella suspension and horseradish peroxidase (HRP) conjugated secondary antibody (Ab2) solution, a sandwich electrochemical immunosensor has been constructed. The electrochemical signal was obtained and improved by comparing the composite film with chitosan film. The result has shown that the constructed sensor provides a wide linear range from 10 to 10(5) CFU/mL with a low detection limit of 5 CFU/mL (at the ratio of signal to noise, S/N=3:1). Furthermore, the proposed immunosensor has demonstrated good selectivity and reproducibility, which indicates its potential in the clinical diagnosis of Salmonella contaminations. PMID:26048833

  13. Carbon Nanotube-based microelectrodes for enhanced detection of neurotransmitters

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher B.

    Fast-scan cyclic voltammetry (FSCV) is one of the common techniques used for rapid measurement of neurotransmitters in vivo. Carbon-fiber microelectrodes (CFMEs) are typically used for neurotransmitter detection because of sub-second measurement capabilities, ability to measure changes in neurotransmitter concentration during neurotransmission, and the small size electrode diameter, which limits the amount of damage caused to tissue. Cylinder CFMEs, typically 50 -- 100 microm long, are commonly used for in vivo experiments because the electrode sensitivity is directly related to the electrode surface area. However the length of the electrode can limit the spatial resolution of neurotransmitter detection, which can restrict experiments in Drosophila and other small model systems. In addition, the electrode sensitivity toward dopamine and serotonin detection drops significantly for measurements at rates faster than 10 Hz, limiting the temporal resolution of CFMEs. While the use of FSCV at carbon-fiber microelectrodes has led to substantial strides in our understanding of neurotransmission, techniques that expand the capabilities of CFMEs are crucial to fully maximize the potential uses of FSCV. This dissertation introduces new methods to integrate carbon nanotubes (CNT) into microelectrodes and discusses the electrochemical enhancements of these CNT-microelectrodes. The electrodes are specifically designed with simple fabrication procedures so that highly specialized equipment is not necessary, and they utilize commercially available materials so that the electrodes could be easily integrated into existing systems. The electrochemical properties of CNT modified CFMEs are characterized using FSCV and the effect of CNT functionalization on these properties is explored in Chapter 2. For example, CFME modification using carboxylic acid functionalized CNTs yield about a 6-fold increase in dopamine oxidation current, but modification with octadecylamine CNTs results in a

  14. Robotic Vision With Enhanced Detection Of Edges

    NASA Technical Reports Server (NTRS)

    Davis, V. L.; Shawaga, L.; Walsh, P.; Kambies, K.

    1993-01-01

    Robotic vision subsystem provides enhanced detection of edges as it preprocesses image of target moving in six degrees of freedom. Subsystem designed to filter out high (spatial) frequency components in image, with frequency response tuned to size of object detected. Blurring and background noise reduced to avoid false detection of moving target. Image produced used by another vision subsystem guiding robot to mate with target. Produces less noise and operates more reliably.

  15. Reduced graphene oxide-yttria nanocomposite modified electrode for enhancing the sensitivity of electrochemical genosensor.

    PubMed

    Rasheed, P Abdul; Radhakrishnan, Thulasi; Shihabudeen, P K; Sandhyarani, N

    2016-09-15

    Reduced graphene oxide-yttria nanocomposite (rGO:Y) is applied as electrochemical genosensor platform for ultrahigh sensitive detection of breast cancer 1 (BRCA1) gene for the first time. The sensor is based on the sandwich assay in which gold nanoparticle cluster labeled reporter DNA hybridize to the target DNA. Glassy carbon electrode modified with rGO-yttria serves as the immobilization platform for capture probe DNA. The sensor exhibited a fine capability of sensing BRCA1 gene with linear range of 10attomolar (aM) to 1nanomolar (nM) and a detection limit of 5.95attomolar. The minimum distinguishable response concentration is down to the attomolar level with a high sensitivity and selectivity. We demonstrated that the use of rGO:Y modified electrode along with gold nanoparticle cluster (AuNPC) label leads to the highly sensitive electrochemical detection of BRCA1 gene. PMID:27153526

  16. Reduced graphene oxide-yttria nanocomposite modified electrode for enhancing the sensitivity of electrochemical genosensor.

    PubMed

    Rasheed, P Abdul; Radhakrishnan, Thulasi; Shihabudeen, P K; Sandhyarani, N

    2016-09-15

    Reduced graphene oxide-yttria nanocomposite (rGO:Y) is applied as electrochemical genosensor platform for ultrahigh sensitive detection of breast cancer 1 (BRCA1) gene for the first time. The sensor is based on the sandwich assay in which gold nanoparticle cluster labeled reporter DNA hybridize to the target DNA. Glassy carbon electrode modified with rGO-yttria serves as the immobilization platform for capture probe DNA. The sensor exhibited a fine capability of sensing BRCA1 gene with linear range of 10attomolar (aM) to 1nanomolar (nM) and a detection limit of 5.95attomolar. The minimum distinguishable response concentration is down to the attomolar level with a high sensitivity and selectivity. We demonstrated that the use of rGO:Y modified electrode along with gold nanoparticle cluster (AuNPC) label leads to the highly sensitive electrochemical detection of BRCA1 gene.

  17. Label-Free Toxin Detection by Means of Time-Resolved Electrochemical Impedance Spectroscopy

    PubMed Central

    Chai, Changhoon; Takhistov, Paul

    2010-01-01

    The real-time detection of trace concentrations of biological toxins requires significant improvement of the detection methods from those reported in the literature. To develop a highly sensitive and selective detection device it is necessary to determine the optimal measuring conditions for the electrochemical sensor in three domains: time, frequency and polarization potential. In this work we utilized a time-resolved electrochemical impedance spectroscopy for the detection of trace concentrations of Staphylococcus enterotoxin B (SEB). An anti-SEB antibody has been attached to the nano-porous aluminum surface using 3-aminopropyltriethoxysilane/glutaraldehyde coupling system. This immobilization method allows fabrication of a highly reproducible and stable sensing device. Using developed immobilization procedure and optimized detection regime, it is possible to determine the presence of SEB at the levels as low as 10 pg/mL in 15 minutes. PMID:22315560

  18. Integration of Faradaic electrochemical impedance spectroscopy into a scalable surface plasmon biosensor for in tandem detection.

    PubMed

    Hong, Brandon; Sun, Alexander; Pang, Lin; Venkatesh, A G; Hall, Drew; Fainman, Yeshaiahu

    2015-11-16

    We present an integrated label-free biosensor based on surface plasmon resonance (SPR) and Faradaic electrochemical impedance spectroscopy (f-EIS) sensing modalities, for the simultaneous detection of biological analytes. Analyte detection is based on the angular spectroscopy of surface plasmon resonance and the extraction of charge transfer resistance values from reduction-oxidation reactions at the gold surface, as responses to functionalized surface binding events. To collocate the measurement areas and fully integrate the modalities, holographically exposed thin-film gold SPR-transducer gratings are patterned into coplanar electrodes for tandem impedance sensing. Mutual non-interference between plasmonic and electrochemical measurement processes is shown, and using our scalable and compact detection system, we experimentally demonstrate biotinylated surface capture of neutravidin concentrations as low as 10 nM detection, with a 5.5 nM limit of detection.

  19. Fast and sensitive detection of mycotoxins in wheat using microfluidics based Real-time Electrochemical Profiling.

    PubMed

    Olcer, Zehra; Esen, Elif; Muhammad, Turghun; Ersoy, Aylin; Budak, Sinan; Uludag, Yıldız

    2014-12-15

    The objective of the study has been the development of a new sensing platform, called Real-time Electrochemical Profiling (REP) that relies on real-time electrochemical immunoassay detection. The proposed REP platform consists of new electrode arrays that are easy to fabricate, has a small imprint allowing microfluidic system integration, enables multiplexed amperometric measurements and performs well in terms of electrochemical immunoassay detection as shown through the deoxynivalenol detection assays. The deoxynivalenol detection has been conducted according to an optimised REP assay protocol using deoxynivalenol standards at varying concentrations and a standard curve was obtained (y=-20.33ln(x)+124.06; R(2)=0.97) with a limit of detection of 6.25 ng/ml. As both ELISA and REP detection methods use horse radish peroxidase as the label and 3.3',5.5'-Tetramethylbenzidine as the substrate, the performance of the REP platform as an ELISA reader has also been investigated and a perfect correlation between the deoxynivalenol concentration and the current response was obtained (y=-14.56ln(x)+101.02; R(2)=0.99). The calibration curves of both assays have been compared to conventional ELISA tests for confirmation. After assay optimisation using toxin spiked buffer, the deoxynivalenol detection assay has also been performed to detect toxins in wheat grain.

  20. Fast and sensitive detection of mycotoxins in wheat using microfluidics based Real-time Electrochemical Profiling.

    PubMed

    Olcer, Zehra; Esen, Elif; Muhammad, Turghun; Ersoy, Aylin; Budak, Sinan; Uludag, Yıldız

    2014-12-15

    The objective of the study has been the development of a new sensing platform, called Real-time Electrochemical Profiling (REP) that relies on real-time electrochemical immunoassay detection. The proposed REP platform consists of new electrode arrays that are easy to fabricate, has a small imprint allowing microfluidic system integration, enables multiplexed amperometric measurements and performs well in terms of electrochemical immunoassay detection as shown through the deoxynivalenol detection assays. The deoxynivalenol detection has been conducted according to an optimised REP assay protocol using deoxynivalenol standards at varying concentrations and a standard curve was obtained (y=-20.33ln(x)+124.06; R(2)=0.97) with a limit of detection of 6.25 ng/ml. As both ELISA and REP detection methods use horse radish peroxidase as the label and 3.3',5.5'-Tetramethylbenzidine as the substrate, the performance of the REP platform as an ELISA reader has also been investigated and a perfect correlation between the deoxynivalenol concentration and the current response was obtained (y=-14.56ln(x)+101.02; R(2)=0.99). The calibration curves of both assays have been compared to conventional ELISA tests for confirmation. After assay optimisation using toxin spiked buffer, the deoxynivalenol detection assay has also been performed to detect toxins in wheat grain. PMID:24998314

  1. Dual Detection of Cancer Biomarker CA125 Using Absorbance and Electrochemical Methods

    PubMed Central

    Al-Ogaidi, Israa; Aguilar, Zoraida P.; Suri, Savan; Gou, Honglei; Wu, Nianqiang

    2013-01-01

    An enzyme-linked immunoassay based on the dual signal transduction mechanisms has been developed for detection of ovarian cancer biomarker CA125. The immunoassays use a nanoelectrode array (NEA) chip and absorbance methods for the dual detection. The NEA is used to confirm the optical detection of CA125 that is carried out in a high-binding 96-well plate. An alkaline phosphatase (AP) enzyme was used to label the detection antibody to allow for both the optical and electrochemical detection of CA125. Two kinds of substrates were catalyzed by the AP enzyme. Para-nitrophenylphosphate (PNPP) produces chromogenic para-nitrophenol (PNP), which can be optically detected at 405 nm. Para-aminophenylphosphate (PAPP) produces electroactive para-aminophenol (PAP), which can be detected amperometrically between −0.1 to 0.3 V. The linear ranges have been determined to be 5–1000 U/mL and 5–1000 U/mL for the optical and electrochemical immunoassays, respectively. The limit of detection of the optical immunoassay is 1.3 U/mL and 40 U/mL for the optical and electrochemical methods, respectively. PMID:23917224

  2. Method and device for the detection of phenol and related compounds. [in an electrochemical cell

    NASA Technical Reports Server (NTRS)

    Schiller, J. G.; Liu, C. C. (Inventor)

    1979-01-01

    A method is described which permits the selective oxidation and potentiometric detection of phenol and related compounds in an electrochemical cell. An anode coated with a gel immobilized oxidative enzyme and a cathode are each placed in an electrolyte solution. The potential of the cell is measured by a potentiometer connected to the electrodes.

  3. Electrochemical magnetoimmunosensing approach for the sensitive detection of H9N2 avian influenza virus particles.

    PubMed

    Zhou, Chuan-Hua; Shu, Yun; Hong, Zheng-Yuan; Pang, Dai-Wen; Zhang, Zhi-Ling

    2013-09-01

    A novel electrochemical magnetoimmunosensor for fast and ultrasensitive detection of H9N2 avian influenza virus particles (H9N2 AIV) was designed based on the combination of high-efficiency immunomagnetic separation, enzyme catalytic amplification, and the biotin-streptavidin system. The reusable, homemade magneto Au electrode (M-AuE) was designed and used for the direct sensing. Immunocomplex-coated magnetic beads (IMBs) were easily accumulated on the surface of the M-AuE to obtain the catalytically reduced electrochemical signal of H2 O2 after the immunoreaction. The transducer was regenerated through a simple washing procedure, which made it possible to detect all the samples on a single electrode with higher reproducibility. The magnetic-bead-based electrochemical immunosensor showed better analytical performance than the planar-electrode-based immunosensor with the same sandwich construction. Amounts as low as 10 pg mL(-1) H9N2 AIV could be detected even in samples of chicken dung. This electrochemical magnetoimmunosensor not only provides a simple platform for the detection of the virus with high sensitivity, selectivity, and reproducibility but also shows great potential in the early diagnosis of diseases.

  4. Electrochemical detection of single molecules using abiotic nanopores having electrically tunable dimensions

    DOEpatents

    Sansinena, Jose-Maria; Redondo, Antonio; Olazabal, Virginia; Hoffbauer, Mark A.; Akhadov, Elshan A.

    2009-12-29

    A barrier structure for use in an electrochemical stochastic membrane sensor for single molecule detection. The sensor is based upon inorganic nanopores having electrically tunable dimensions. The inorganic nanopores are formed from inorganic materials and an electrically conductive polymer. Methods of making the barrier structure and sensing single molecules using the barrier structure are also described.

  5. Dual-responses for electrochemical and electrochemiluminescent detection based on a bifunctional probe.

    PubMed

    Han, Jing; Zhuo, Ying; Chai, Yaqin; Yuan, Ruo

    2014-03-28

    A bifunctional probe (PTC-Tb) which acts as not only a well-defined and stable electrochemical redox molecule but also as a highly efficient co-reactant of an electrochemiluminescent oxygen-peroxydisulfate system was firstly synthesized and applied to the construction of dual-response aptasensors for thrombin detection.

  6. A novel M-shape electrochemical aptasensor for ultrasensitive detection of tetracyclines.

    PubMed

    Taghdisi, Seyed Mohammad; Danesh, Noor Mohammad; Ramezani, Mohammad; Abnous, Khalil

    2016-11-15

    Analytical techniques for detection and quantitation of tetracyclines in food products are greatly in demand. In this study, a novel electrochemical aptasensor was designed for ultrasensitive and selective detection of tetracyclines, based on M-shape structure of aptamer (Apt)-complementary strands of aptamer (CSs) complex, exonuclease I (Exo I) and gold electrode. The aptasensor was developed to make a noticeable electrochemical difference in the absence and presence of tetracycline. In the absence of tetracycline, the M-shape structure, which acts as a gate and barrier for the access of redox probe to the surface of gold electrode remains intact, leading to a weak electrochemical signal. Upon addition of tetracycline, Apt leaves CSs, resulting in disassembly of M-shape structure and following the addition of Exo I, a strong electrochemical signal was observed. The developed analytical assay indicated high selectivity toward tetracycline with a limit of detection (LOD) as low as 450 pM. Moreover, the designed aptasensor was effectively used for the detection of tetracycline in milk and serum samples with LODs of 740 and 710 pM, respectively.

  7. Electrochemical aptamer scaffold biosensors for detection of botulism and ricin toxins.

    PubMed

    Fetter, Lisa; Richards, Jonathan; Daniel, Jessica; Roon, Laura; Rowland, Teisha J; Bonham, Andrew J

    2015-10-21

    Protein toxins present considerable health risks, but detection often requires laborious analysis. Here, we developed electrochemical aptamer biosensors for ricin and botulinum neurotoxins, which display robust and specific signal at nanomolar concentrations and function in dilute serum. These biosensors may aid future efforts for the rapid diagnosis of toxins. PMID:26323568

  8. An electrochemical peptide cleavage-based biosensor for matrix metalloproteinase-2 detection with exonuclease III-assisted cycling signal amplification.

    PubMed

    Wang, Ding; Yuan, Yali; Zheng, Yingning; Chai, Yaqin; Yuan, Ruo

    2016-05-01

    In this work, an electrochemical peptide biosensor was developed for matrix metalloproteinase-2 (MMP-2) detection by conversion of a peptide cleavage event into DNA detection with exonuclease III (Exo III)-assisted cycling signal amplification.

  9. Capillary electrophoresis-electrochemical detection microchip device and supporting circuits

    DOEpatents

    Jackson, Douglas J.; Roussel, Jr., Thomas J.; Crain, Mark M.; Baldwin, Richard P.; Keynton, Robert S.; Naber, John F.; Walsh, Kevin M.; Edelen, John. G.

    2008-03-18

    The present invention is a capillary electrophoresis device, comprising a substrate; a first channel in the substrate, and having a buffer arm and a detection arm; a second channel in the substrate intersecting the first channel, and having a sample arm and a waste arm; a buffer reservoir in fluid communication with the buffer arm; a waste reservoir in fluid communication with the waste arm; a sample reservoir in fluid communication with the sample arm; and a detection reservoir in fluid communication with the detection arm. The detection arm and the buffer arm are of substantially equal length.

  10. Detection of radiation-induced changes in electrochemical properties of austenitic stainless steels using miniaturized specimens and the single-loop electrochemical potentiokinetic reactivation method

    SciTech Connect

    Inazumi, T.; Bell, G.E.C.; Kenik, E.A.; Kiuchi, K.

    1993-01-01

    Single-loop electrochemical potentiokinetic reactivation testing of miniaturized (TEM) specimens can provide reliable data comparable to data obtained with larger specimens. Significant changes in electrochemical properties (increased reactivation current and Flade potential) were detected for PCA and type 316 stainless steels irradiated at 200--420{degrees}C up to 7--9 dpa. Irradiations in the FFTF Materials Open Test Assembly and in the Oak Ridge Research Reactor are reported on. 45 figs., 5 tabs., 52 refs.

  11. Detection of radiation-induced changes in electrochemical properties of austenitic stainless steels using miniaturized specimens and the single-loop electrochemical potentiokinetic reactivation method

    SciTech Connect

    Inazumi, T.; Bell, G.E.C.; Kenik, E.A.; Kiuchi, K.

    1993-01-01

    Single-loop electrochemical potentiokinetic reactivation testing of miniaturized (TEM) specimens can provide reliable data comparable to data obtained with larger specimens. Significant changes in electrochemical properties (increased reactivation current and Flade potential) were detected for PCA and type 316 stainless steels irradiated at 200--420[degrees]C up to 7--9 dpa. Irradiations in the FFTF Materials Open Test Assembly and in the Oak Ridge Research Reactor are reported on. 45 figs., 5 tabs., 52 refs.

  12. Magnetic beads-based electrochemical immunosensor for detection of pseudorabies virus antibody in swine serum.

    PubMed

    Li, Fang; Zhou, Rui; Zhao, Kaihong; Chen, Huanchun; Hu, Yonggang

    2011-12-15

    A novel magnetic electrochemical immunosensor has been developed for the detection of pseudorabies virus antibody in swine serum. The magnetic glass carbon electrode was fabricated to manipulate magnetic beads for the direct sensing applications. Magnetic beads were employed as the platforms for the immobilization and immunoreaction process, and gold nanoparticles were chosen as electroactive labels for the electrochemical detection. The parameters concerning the assay strategy were carefully investigated. Under the optimal conditions, the linear response range of pseudorabies virus antibody dilution ratio (standard positive serum) was 1:250 to 1:1000 with a detection limit of 1:1000. Finally, this developed immunoassay method was successfully applied in the detection of pseudorabies virus antibody in swine serum, and had a good diagnostic accordance in comparison with ELISA.

  13. Development of an Automated DNA Detection System Using an Electrochemical DNA Chip Technology

    NASA Astrophysics Data System (ADS)

    Hongo, Sadato; Okada, Jun; Hashimoto, Koji; Tsuji, Koichi; Nikaido, Masaru; Gemma, Nobuhiro

    A new compact automated DNA detection system Genelyzer™ has been developed. After injecting a sample solution into a cassette with a built-in electrochemical DNA chip, processes from hybridization reaction to detection and analysis are all operated fully automatically. In order to detect a sample DNA, electrical currents from electrodes due to an oxidization reaction of electrochemically active intercalator molecules bound to hybridized DNAs are detected. The intercalator is supplied as a reagent solution by a fluid supply unit of the system. The feasibility test proved that the simultaneous typing of six single nucleotide polymorphisms (SNPs) associated with a rheumatoid arthritis (RA) was carried out within two hours and that all the results were consistent with those by conventional typing methods. It is expected that this system opens a new way to a DNA testing such as a test for infectious diseases, a personalized medicine, a food inspection, a forensic application and any other applications.

  14. In situ optimization of pH for parts-per-billion electrochemical detection of dissolved hydrogen sulfide using boron doped diamond flow electrodes.

    PubMed

    Bitziou, Eleni; Joseph, Maxim B; Read, Tania L; Palmer, Nicola; Mollart, Tim; Newton, Mark E; Macpherson, Julie V

    2014-11-01

    A novel electrochemical approach to the direct detection of hydrogen sulfide (H2S), in aqueous solutions, covering a wide pH range (acid to alkali), is described. In brief, a dual band electrode device is employed, in a hydrodynamic flow cell, where the upstream electrode is used to controllably generate hydroxide ions (OH(-)), which flood the downstream detector electrode and provide the correct pH environment for complete conversion of H2S to the electrochemically detectable, sulfide (HS(-)) ion. All-diamond, coplanar conducting diamond band electrodes, insulated in diamond, were used due to their exceptional stability and robustness when applying extreme potentials, essential attributes for both local OH(-) generation via the reduction of water, and for in situ cleaning of the electrode, post oxidation of sulfide. Using a galvanostatic approach, it was demonstrated the pH locally could be modified by over five pH units, depending on the initial pH of the mobile phase and the applied current. Electrochemical detection limits of 13.6 ppb sulfide were achieved using flow injection amperometry. This approach which offers local control of the pH of the detector electrode in a solution, which is far from ideal for optimized detection of the analyte of interest, enhances the capabilities of online electrochemical detection systems.

  15. In situ optimization of pH for parts-per-billion electrochemical detection of dissolved hydrogen sulfide using boron doped diamond flow electrodes.

    PubMed

    Bitziou, Eleni; Joseph, Maxim B; Read, Tania L; Palmer, Nicola; Mollart, Tim; Newton, Mark E; Macpherson, Julie V

    2014-11-01

    A novel electrochemical approach to the direct detection of hydrogen sulfide (H2S), in aqueous solutions, covering a wide pH range (acid to alkali), is described. In brief, a dual band electrode device is employed, in a hydrodynamic flow cell, where the upstream electrode is used to controllably generate hydroxide ions (OH(-)), which flood the downstream detector electrode and provide the correct pH environment for complete conversion of H2S to the electrochemically detectable, sulfide (HS(-)) ion. All-diamond, coplanar conducting diamond band electrodes, insulated in diamond, were used due to their exceptional stability and robustness when applying extreme potentials, essential attributes for both local OH(-) generation via the reduction of water, and for in situ cleaning of the electrode, post oxidation of sulfide. Using a galvanostatic approach, it was demonstrated the pH locally could be modified by over five pH units, depending on the initial pH of the mobile phase and the applied current. Electrochemical detection limits of 13.6 ppb sulfide were achieved using flow injection amperometry. This approach which offers local control of the pH of the detector electrode in a solution, which is far from ideal for optimized detection of the analyte of interest, enhances the capabilities of online electrochemical detection systems. PMID:25263331

  16. Detecting and measuring metabolic byproducts by electrochemical sensing

    NASA Technical Reports Server (NTRS)

    Wilkins, J. R.; Stoner, G. E.

    1974-01-01

    Method of detecting certain groups of bacteria is based on sensing buildup in molecular hydrogen. Apparatus is easy to assemble and use, and it has added advantage that hydrogen evolution by test micro-organisms can be measured automatically and accurately. System has been used to detect and enumerate variety of gram-negative bacteria of enterobacteriaceae group.

  17. Preparation of Electrochemical Biosensor for Detection of Organophosphorus Pesticides

    PubMed Central

    Gothwal, Ashish; Beniwal, Puneet; Dhull, Vikas

    2014-01-01

    Polyvinyl chloride (PVC) can be used to develop reaction beaker which acts as electrochemical cell for the measurement of OP pesticides. Being chemically inert, corrosion resistant, and easy in molding to various shapes and size, PVC can be used for the immobilization of enzyme. Organophosphorus hydrolase was immobilized covalently onto the chemically activated inner surface of PVC beaker by using glutaraldehyde as a coupling agent. The carbon nanotubes paste working electrode was constructed for amperometric measurement at a potential of +0.8 V. The biosensor showed optimum response at pH 8.0 with incubation temperature of 40°C. Km and Imax for substrate (methyl parathion) were 322.58 µM and 1.1 µA, respectively. Evaluation study showed a correlation of 0.985, which was in agreement with the standard method. The OPH biosensor lost 50% of its initial activity after its regular use for 25 times over a period of 50 days when stored in 0.1 M sodium phosphate buffer, pH 8.0 at 4°C. No interference was observed by interfering species. PMID:25667593

  18. DNA Hybridization Sensors Based on Electrochemical Impedance Spectroscopy as a Detection Tool

    PubMed Central

    Park, Jin-Young; Park, Su-Moon

    2009-01-01

    Recent advances in label free DNA hybridization sensors employing electrochemical impedance spectroscopy (EIS) as a detection tool are reviewed. These sensors are based on the modulation of the blocking ability of an electrode modified with a probe DNA by an analyte, i.e., target DNA. The probe DNA is immobilized on a self-assembled monolayer, a conducting polymer film, or a layer of nanostructures on the electrode such that desired probe DNA would selectively hybridize with target DNA. The rate of charge transfer from the electrode thus modified to a redox indicator, e.g., [Fe(CN)6]3−/4−, which is measured by EIS in the form of charge transfer resistance (Rct), is modulated by whether or not, as well as how much, the intended target DNA is selectively hybridized. Efforts made to enhance the selectivity as well as the sensitivity of DNA sensors and to reduce the EIS measurement time are briefly described along with brief future perspectives in developing DNA sensors. PMID:22303136

  19. In Situ Electrochemical Oxidation Tuning of Transition Metal Disulfides to Oxides for Enhanced Water Oxidation.

    PubMed

    Chen, Wei; Wang, Haotian; Li, Yuzhang; Liu, Yayuan; Sun, Jie; Lee, Sanghan; Lee, Jang-Soo; Cui, Yi

    2015-08-26

    The development of catalysts with earth-abundant elements for efficient oxygen evolution reactions is of paramount significance for clean and sustainable energy storage and conversion devices. Our group demonstrated recently that the electrochemical tuning of catalysts via lithium insertion and extraction has emerged as a powerful approach to improve catalytic activity. Here we report a novel in situ electrochemical oxidation tuning approach to develop a series of binary, ternary, and quaternary transition metal (e.g., Co, Ni, Fe) oxides from their corresponding sulfides as highly active catalysts for much enhanced water oxidation. The electrochemically tuned cobalt-nickel-iron oxides grown directly on the three-dimensional carbon fiber electrodes exhibit a low overpotential of 232 mV at current density of 10 mA cm(-2), small Tafel slope of 37.6 mV dec(-1), and exceptional long-term stability of electrolysis for over 100 h in 1 M KOH alkaline medium, superior to most non-noble oxygen evolution catalysts reported so far. The materials evolution associated with the electrochemical oxidation tuning is systematically investigated by various characterizations, manifesting that the improved activities are attributed to the significant grain size reduction and increase of surface area and electroactive sites. This work provides a promising strategy to develop electrocatalysts for large-scale water-splitting systems and many other applications. PMID:27162978

  20. In Situ Electrochemical Oxidation Tuning of Transition Metal Disulfides to Oxides for Enhanced Water Oxidation

    PubMed Central

    2015-01-01

    The development of catalysts with earth-abundant elements for efficient oxygen evolution reactions is of paramount significance for clean and sustainable energy storage and conversion devices. Our group demonstrated recently that the electrochemical tuning of catalysts via lithium insertion and extraction has emerged as a powerful approach to improve catalytic activity. Here we report a novel in situ electrochemical oxidation tuning approach to develop a series of binary, ternary, and quaternary transition metal (e.g., Co, Ni, Fe) oxides from their corresponding sulfides as highly active catalysts for much enhanced water oxidation. The electrochemically tuned cobalt–nickel–iron oxides grown directly on the three-dimensional carbon fiber electrodes exhibit a low overpotential of 232 mV at current density of 10 mA cm–2, small Tafel slope of 37.6 mV dec–1, and exceptional long-term stability of electrolysis for over 100 h in 1 M KOH alkaline medium, superior to most non-noble oxygen evolution catalysts reported so far. The materials evolution associated with the electrochemical oxidation tuning is systematically investigated by various characterizations, manifesting that the improved activities are attributed to the significant grain size reduction and increase of surface area and electroactive sites. This work provides a promising strategy to develop electrocatalysts for large-scale water-splitting systems and many other applications. PMID:27162978

  1. Analytical notes - Electrochemical method for early detection and monitoring of coliforms

    NASA Technical Reports Server (NTRS)

    Wilkins, J. R.; Boykin, E. H.

    1976-01-01

    An electrochemical method for detecting bacteria, based on a linear relationship between inoculum size and the time of hydrogen evolution, was tested for the early detection and monitoring of coliforms in naturally contaminated estuarine and fresh water samples. Standard methods for coliform analysis were performed on each sample, and membrane filtration counts were used to construct dose-response curves; relationships and results are discussed herein.

  2. Molecularly imprinted electrochemical sensor based on amine group modified graphene covalently linked electrode for 4-nonylphenol detection.

    PubMed

    Chen, Hong-Jun; Zhang, Zhao-Hui; Cai, Rong; Chen, Xing; Liu, Yu-Nan; Rao, Wei; Yao, Shou-Zhuo

    2013-10-15

    In this work, an imprinted electrochemical sensor based on electrochemical reduced graphene covalently modified carbon electrode was developed for the determination of 4-nonylphenol (NP). An amine-terminated functional graphene oxide was covalently modified onto the electrode surface with diazonium salt reactions to improve the stability and reproducibility of the imprinted sensor. The electrochemical properties of each modified electrodes were investigated with differential pulse voltammetry (DPV). The electrochemical characteristic of the imprinted sensor was also investigated using electrochemical impedance spectroscopy (EIS) in detail. The response currents of the imprinted electrode exhibited a linear relationship toward 4-nonylphenol concentration ranging from 1.0 × 10(-11) to 1.0 × 10(-8) gm L(-1) with the detection limit of 3.5 × 10(-12) gm L(-1) (S/N=3). The fabricated electrochemical imprinted sensor was successfully applied to the detection of 4-nonylphenol in rain and lake water samples.

  3. In situ detection of TNT contamination using electrochemical sensors in cone penetrometer system

    NASA Astrophysics Data System (ADS)

    Cespedes, Ernesto R.; Cooper, Stafford S.; Davis, William M.; Buttner, William J.; Vickers, William C.

    1995-01-01

    The pyrolysis of TNT and other explosive compounds generates signature compounds that can be efficiently detected by electrochemical sensors. This concept was implemented in the development and testing of a sensor probe for the Site Characterization and Analysis Penetrometer System (SCAPS) for the in situ detection of TNT, RDX, HMX, and other nitrogen-containing soil contaminants. This paper describes the results of laboratory studies and field tests conducted to determine the feasibility of employing electrochemical sensors for detecting subsurface explosives contaminants. A method for the in situ pyrolysis of explosives contaminants in soils was developed, and laboratory tests determined that electrochemical sensing of the pyrolysis products was sensitive, selective, reversible, and capable of broad dynamic range. A penetrometer probe that accommodates the electrochemical sensors (including power supply and signal conditioning electronics), the pyrolyzer unit, the pneumatic components, and geophysical sensors for soil classification was designed and fabricated. Results of tests conducted at the Louisiana Army Ammunition Plant during September 1994, which demonstrated the performance of the SCAPS sensor under actual field conditions, are presented.

  4. Electrochemical detection of protein kinase activity based on carboxypeptidase Y digestion triggered signal amplification.

    PubMed

    Yin, Huanshun; Wang, Xinxu; Guo, Yunlong; Zhou, Yunlei; Ai, Shiyun

    2015-04-15

    An effective assay method for monitoring protein kinase activity and screening inhibitors is greatly beneficial to kinase-related drug discovery, early diagnosis of diseases, and therapeutic effect evaluation. Herein, we develop a simple electrochemical method for detecting the activity of casein kinase II (CK2) based on phosphorylation against carboxypeptidase Y (CPY) digestion triggered signal amplification, where CK2 catalyzed phosphorylation event protects the substrate peptide from the digestion of CPY, maintains the repulsive force of the substrate peptide towards the redox probe, and results in a weak electrochemical signal. Whereas, without phosphorylation, the substrate peptide is digested by CPY and a strong electrochemical signal is obtained. The detection feasibility is demonstrated for the assay of CK2 activity with low detection limit of 0.047unit/mL. Moreover, the biosensor was used for the analysis of kinase inhibition. Based on the electrochemical signal dependent inhibitor concentration, the IC50 value of ellagic acid was estimated to be 39.77nM. The proposed method is also successfully applied to analyze CK2 activity in cell lysates, proving the applicability in complex biological samples.

  5. Use of platinum electrodes for the electrochemical detection of bacteria.

    PubMed

    Wilkins, J R

    1978-11-01

    Platinum electrodes with surface area ratios of four to one were used to detect and enumerate a variety of gram-positive and gram-negative organisms. Linear relationships were established between inoculum size and detection time. End points for platinum electrodes were similar to those obtained with a platinum-reference electrode combination. Shape of the overall response curves and length of detection times for gram-positive organisms were markedly different than those for the majority of gram-negative species. Platinum electrodes are better than the platinum-reference electrode combination because of cost, ease of handling, and clearer definition of the end point.

  6. Use of platinum electrodes for the electrochemical detection of bacteria

    NASA Technical Reports Server (NTRS)

    Wilkins, J. R.

    1978-01-01

    Platinum electrodes with surface area ratios of four to one were used to detect and enumerate a variety of gram-positive and gram-negative organisms. Linear relationships were established between inoculum size and detection time. End points for platinum electrodes were similar to those obtained with a platinum-reference electrode combination. Shape of the overall response curves and length of detection times for gram-positive organisms were markedly different than those for the majority of gram-negative species. Platinum electrodes are better than the platinum-reference electrode combination because of cost, ease of handling, and clearer definition of the end point.

  7. CuO nanowire/microflower/nanowire modified Cu electrode with enhanced electrochemical performance for non-enzymatic glucose sensing.

    PubMed

    Li, Changli; Yamahara, Hiroyasu; Lee, Yaerim; Tabata, Hitoshi; Delaunay, Jean-Jacques

    2015-07-31

    CuO nanowire/microflower structure on Cu foil is synthesized by annealing a Cu(OH)2 nanowire/CuO microflower structure at 250 °C in air. The nanowire/microflower structure with its large surface area leads to an efficient catalysis and charge transfer in glucose detection, achieving a high sensitivity of 1943 μA mM(-1) cm(-2), a wide linear range up to 4 mM and a low detection limit of 4 μM for amperometric glucose sensing in alkaline solution. With a second consecutive growth of CuO nanowires on the microflowers, the sensitivity of the obtained CuO nanowire/microflower/nanowire structure further increases to 2424 μA mM(-1) cm(-2), benefiting from an increased number of electrochemically active sites. The enhanced electrocatalytic performance of the CuO nanowire/microflower/nanowire electrode compared to the CuO nanowire/microflower electrode, CuO nanowire electrode and CuxO film electrode provides evidence for the significant role of available surface area for electrocatalysis. The rational combination of CuO nanowire and microflower nanostructures into a nanowire supporting microflower branching nanowires structure makes it a promising composite nanostructure for use in CuO based electrochemical sensors with promising analytical properties. PMID:26159235

  8. CuO nanowire/microflower/nanowire modified Cu electrode with enhanced electrochemical performance for non-enzymatic glucose sensing.

    PubMed

    Li, Changli; Yamahara, Hiroyasu; Lee, Yaerim; Tabata, Hitoshi; Delaunay, Jean-Jacques

    2015-07-31

    CuO nanowire/microflower structure on Cu foil is synthesized by annealing a Cu(OH)2 nanowire/CuO microflower structure at 250 °C in air. The nanowire/microflower structure with its large surface area leads to an efficient catalysis and charge transfer in glucose detection, achieving a high sensitivity of 1943 μA mM(-1) cm(-2), a wide linear range up to 4 mM and a low detection limit of 4 μM for amperometric glucose sensing in alkaline solution. With a second consecutive growth of CuO nanowires on the microflowers, the sensitivity of the obtained CuO nanowire/microflower/nanowire structure further increases to 2424 μA mM(-1) cm(-2), benefiting from an increased number of electrochemically active sites. The enhanced electrocatalytic performance of the CuO nanowire/microflower/nanowire electrode compared to the CuO nanowire/microflower electrode, CuO nanowire electrode and CuxO film electrode provides evidence for the significant role of available surface area for electrocatalysis. The rational combination of CuO nanowire and microflower nanostructures into a nanowire supporting microflower branching nanowires structure makes it a promising composite nanostructure for use in CuO based electrochemical sensors with promising analytical properties.

  9. CuO nanowire/microflower/nanowire modified Cu electrode with enhanced electrochemical performance for non-enzymatic glucose sensing

    NASA Astrophysics Data System (ADS)

    Li, Changli; Yamahara, Hiroyasu; Lee, Yaerim; Tabata, Hitoshi; Delaunay, Jean-Jacques

    2015-07-01

    CuO nanowire/microflower structure on Cu foil is synthesized by annealing a Cu(OH)2 nanowire/CuO microflower structure at 250 °C in air. The nanowire/microflower structure with its large surface area leads to an efficient catalysis and charge transfer in glucose detection, achieving a high sensitivity of 1943 μA mM-1 cm-2, a wide linear range up to 4 mM and a low detection limit of 4 μM for amperometric glucose sensing in alkaline solution. With a second consecutive growth of CuO nanowires on the microflowers, the sensitivity of the obtained CuO nanowire/microflower/nanowire structure further increases to 2424 μA mM-1 cm-2, benefiting from an increased number of electrochemically active sites. The enhanced electrocatalytic performance of the CuO nanowire/microflower/nanowire electrode compared to the CuO nanowire/microflower electrode, CuO nanowire electrode and CuxO film electrode provides evidence for the significant role of available surface area for electrocatalysis. The rational combination of CuO nanowire and microflower nanostructures into a nanowire supporting microflower branching nanowires structure makes it a promising composite nanostructure for use in CuO based electrochemical sensors with promising analytical properties.

  10. Sensitive and selective electrochemical detection of artemisinin based on its reaction with p-aminophenylboronic acid.

    PubMed

    Wang, Chao; Zholudov, Yuriy T; Nsabimana, Anaclet; Xu, Guobao; Li, Jianping

    2016-09-21

    The electrochemical detection of artemisinin generally requires high oxidation potential or the use of complex electrode modification. We find that artemisinin can react with p-aminophenylboronic acid to produce easily electrochemically detectable aminophenol for the first time. By making use of the new reaction, we report an alternative method to detect artemisinin through the determination of p-aminophenol. The calibration curve for the determination of artemisinin is linear in the range of 2 μmol L(-1) to 200 μmol L(-1) with the detection limit of 0.8 μmol L(-1), which is more sensitive than other reported electrochemical methods. The relative standard deviation is 4.83% for the determination of 10 μM artemisinin. Because the oxidation potential of p-aminophenol is around 0 V, the present method is high selective. When 40 μM, 90 μM and 140 μM of artemisinin were spiked to compound naphthoquine phosphate tablet samples, the recoveries are 107.6%, 105.4% and 101.7%, respectively. This detection strategy is attractive for the detection of artemisinin and its derivatives. The finding that artemisinin can react with aromatic boronic acid has the potential to be exploited for the development of other sensors, such as fluorescence artemisinin sensors. PMID:27590543

  11. High-throughput real-time electrochemical monitoring of LAMP for pathogenic bacteria detection.

    PubMed

    Safavieh, Mohammadali; Ahmed, Minhaz Uddin; Ng, Andy; Zourob, Mohammed

    2014-08-15

    One of the significant challenges in healthcare is the development of point-of-care (POC) diagnostics. POC diagnostics require low-cost devices that offer portability, simplicity in operation and the ability for high-throughput and quantitative analysis. Here, we present a novel roll-to-roll ribbon fluid-handling device for electrochemical real-time monitoring of nucleic acid (NA) amplification and bacteria detection. The device rendered loop-mediated isothermal amplification (LAMP) and real-time electrochemical detection based on the interaction between LAMP amplicon and the redox-reactive osmium complex. We have shown the detection of 30CFU/ml of Escherichia coli (in the range between 30 and 3×10(7)CFU/ml) and 200CFU/ml of Staphylococcus aureus (in the range of 200-2×10(5)CFU/ml) cultured samples in both real-time and end point detection. This device can be used for the detection of various Gram-negative and a number of Gram-positive bacterial pathogens with high sensitivity and specificity in a high-throughput format. Using a roll-to-roll cassette approach, we could detect 12 samples in one assay. Since the LAMP and electrochemical analysis are implemented within sealed flexible biochips, time-consuming processing steps are not required and the risk of contamination is significantly reduced.

  12. Electrochemically enhanced oxidation reactions in sandy soil polluted with mercury

    PubMed

    Thoming; Kliem; Ottosen

    2000-10-16

    problem it is suggested to add chloride to the soil system. Chloride would act as a complexing agent avoiding precipitation and enhancing the dissolution of precipitates as well as elemental mercury. PMID:11036985

  13. Electrochemical detection of benzo(a)pyrene in acetonitrile-water binary medium.

    PubMed

    Du, Chunyan; Hu, Yaqi; Li, Yunchao; Fan, Louzhen; Li, Xiaohong

    2015-06-01

    Electrochemical oxidation of adsorbed benzo(a)pyrene (BaP) on the glassy carbon electrode (GCE) was explored in acetonitrile-water. When the GCE was incubated in 100 nM BaP acetonitrile-water (V(water):V(acetonitrile)=1:1) for 10 min at open circuit, and then transferred into blank acetonitrile-water (V(water):V(acetonitrile)=1:1, pH= 0.70) for differential pulse voltammetry measurement, a distinct oxidation peak at 0.98 V (vs. Ag/AgCl) was observed. The peak potential was about 180 mV lower than that in acetonitrile. Importantly, the peak current was more than 22 times greater. The effects of water on BaP preconcentration on the electrode and electrochemical oxidation were revealed, respectively. Based on the results, an electrochemical assay for BaP detection was developed. The GCE was respectively incubated in acetonitrile-water (V(water):V(acetonitrile)=1:1)with BaP concentration ranged from 0 nM to 1000 nM, and then transferred into the corresponding blank acetonitrile-water (pH= 0.70) for DPV measurements. When the BaP concentration was increased, an increased oxidative current at 0.98 V (vs. Ag/AgCl) was observed, and a detection limit of 0.67 nM was achieved. Because all other priority polycyclic aromatic hydrocarbons could not be electrochemically oxidized at 0.98 V, the electrochemical assay showed very high selectivity to BaP. Finally, the developed electrochemical assay was successfully applied to determination of BaP in a series of real world samples, such as drinking water, tap water, lake water and river water.

  14. Detectivity enhancement in THz electrooptical sampling

    SciTech Connect

    Ahmed, Saima; Savolainen, Janne; Hamm, Peter

    2014-01-15

    We demonstrate and discuss a simple scheme that significantly enhances the detectivity of THz electro-optical sampling by introducing a sequence of Brewster windows that increases the ellipticity of the probe beam. By varying the window material or the number of Brewster windows, the enhancement factor can be adjusted; we demonstrate an enhancement factor of ≈20 with four ZnSe Brewster windows. The scheme is particularly useful when very small THz fields are to be measured in connection with low-repetition rate amplified Ti:S laser systems.

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

    NASA Astrophysics Data System (ADS)

    Ahmadalinezhad, Asieh

    properties, we fabricated a highly sensitive and mediator-free electrochemical biosensor for the determination of total cholesterol. The developed biosensor possessed high selectivity and sensitivity (29.33 microA mM--1cm --2). The apparent Michaelis--Menten constant, KappM of this biosensor was very low (0.64 mM), which originated from both the effective immobilization process and the nanoporous structure of the substrate. The biosensor exhibited a wide linear range, up to 300 mg dL--1 , in a physiological environment (pH 7.4); making it a promising candidate for the clinical determination of cholesterol. The fabricated biosensor was tested further by utilizing actual food samples (e.g., margarine, butter and fish oil). The results indicated that it has the potential capacity to be employed as a facile cholesterol detection tool in the food industry and for supplement quality control. To enhance the stability of the biosensors in the continuous monitoring of glucose, we designed a novel platform that was based on buckypaper. The fabricated biosensor responded to glucose with a considerable functional lifetime of over 80 days and detected glucose with a dynamic linear range of over 9 mM with a detection limit of 0.01 mM. To investigate the effects of the physical dimensions of nanomaterials on electrochemical biosensing, we synthesized TiO2 nanowires with controllable dimensions via a facile thermal oxidation treatment of a Ti substrate. To improve the conductivity of the TiO2 nanowires and to facilitate the immobilization of enzymes, a thin layer of carbon was deposited onto the TiO2 nanowires via a chemical vapour deposition method. Upon the immobilization of glucose oxidase as a model protein, direct electron transfer was observed in a mediator-free biosensing environment. Our electrochemical studies have revealed that the electron transfer rate of the immobilized glucose oxidase is strongly dependent on the dimensions of the carbonized TiO 2 nanowires, and that the

  16. Integrated electrochemical microsystems for genetic detection of pathogens at the point of care.

    PubMed

    Hsieh, Kuangwen; Ferguson, B Scott; Eisenstein, Michael; Plaxco, Kevin W; Soh, H Tom

    2015-04-21

    The capacity to achieve rapid, sensitive, specific, quantitative, and multiplexed genetic detection of pathogens via a robust, portable, point-of-care platform could transform many diagnostic applications. And while contemporary technologies have yet to effectively achieve this goal, the advent of microfluidics provides a potentially viable approach to this end by enabling the integration of sophisticated multistep biochemical assays (e.g., sample preparation, genetic amplification, and quantitative detection) in a monolithic, portable device from relatively small biological samples. Integrated electrochemical sensors offer a particularly promising solution to genetic detection because they do not require optical instrumentation and are readily compatible with both integrated circuit and microfluidic technologies. Nevertheless, the development of generalizable microfluidic electrochemical platforms that integrate sample preparation and amplification as well as quantitative and multiplexed detection remains a challenging and unsolved technical problem. Recognizing this unmet need, we have developed a series of microfluidic electrochemical DNA sensors that have progressively evolved to encompass each of these critical functionalities. For DNA detection, our platforms employ label-free, single-step, and sequence-specific electrochemical DNA (E-DNA) sensors, in which an electrode-bound, redox-reporter-modified DNA "probe" generates a current change after undergoing a hybridization-induced conformational change. After successfully integrating E-DNA sensors into a microfluidic chip format, we subsequently incorporated on-chip genetic amplification techniques including polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP) to enable genetic detection at clinically relevant target concentrations. To maximize the potential point-of-care utility of our platforms, we have further integrated sample preparation via immunomagnetic separation, which

  17. A novel electrochemical sensor based on zirconia/ordered macroporous polyaniline for ultrasensitive detection of pesticides.

    PubMed

    Wang, Yonglan; Jin, Jun; Yuan, Caixia; Zhang, Fan; Ma, Linlin; Qin, Dongdong; Shan, Duoliang; Lu, Xiaoquan

    2015-01-21

    A simple and mild strategy was proposed to develop a novel electrochemical sensor based on zirconia/ordered macroporous polyaniline (ZrO2/OMP) and further used for the detection of methyl parathion (MP), one of the organophosphate pesticides (OPPs). Due to the strong affinity of phosphate groups with ZrO2 and the advantages of OMP such as high catalytic activity and good conductivity, the developed sensor showed a limit of detection as low as 2.28 × 10(-10) mol L(-1) (S/N = 3) by square-wave voltammograms, and good selectivity, acceptable reproducibility and stability. Most importantly, this novel sensor was successfully applied to detect MP in real samples of apple and cabbage. It is expected that this method has potential applications in electrochemical sensing platforms with simple, sensitive, selective and fast analysis.

  18. Flavonoids electrochemical detection in fruit extracts and total antioxidant capacity evaluation.

    PubMed

    Gomes, Sara M C; Ghica, Mariana-Emilia; Rodrigues, Isaide Araujo; de Souza Gil, Eric; Oliveira-Brett, Ana Maria

    2016-07-01

    Phenolic compounds detection in fruit extracts from: açai, bacuri, buriti, blackberry, black mulberry, blueberry, juçara, physalis, raspberry, and tamarillo, have been performed by reverse-phase high performance liquid chromatography with electrochemical detection (RP-HPLC-EC), using two detectors in series: a wall-jet detector flow cell with a glassy carbon electrode, and a thin-layer flow cell detector with a boron doped diamond electrode. This methodology, in gradient elution mode, was successfully used to detect seventeen phenolic compounds in the fruit extracts. The total antioxidant capacity of the fruit extracts by the electrochemical quantitative index (EI) and the method of capture of diphenilpicrilhydrazil (DPPH(●)) free radical "efficient concentration" (EC50), was evaluated. A very good correlation between EI and EC50 assays has been obtained, the fruit with the highest total antioxidant capacity being blackberry, while physalis exhibited the lowest antioxidant power. PMID:27154676

  19. An electrochemical molecular recognition-based aptasensor for multiple protein detection.

    PubMed

    Cheng, Lin; Zhang, Jie; Lin, Yan; Wang, Qiong; Zhang, XiuXiu; Ding, YanHua; Cui, Hanfeng; Fan, Hao

    2015-12-15

    This article reports a simple electrochemical approach for the detection of multiple proteins (thrombin and lysozyme) using Dabcyl-labeled aptamer modified metal nanoparticles (DLAPs). DLAPs were immobilized on β-cyclodextrins (β-CDs) modified electrode by means of host-guest self-assembly. During the time of detection, the aptamers' structure will change due to the specific binding with corresponding proteins that forced DLAPs far away from the electrode that had been modified by β-CDs. Thus, the capture of target proteins onto DLAPs was translated via the electrochemical current signal offered by metal nanoparticles. Linearity of the aptasensor for quantitative measurements was demonstrated. Determinations of proteins in human real serum samples were also performed to demonstrate detection in real clinical samples. PMID:26344894

  20. A Nanocoaxial-Based Electrochemical Sensor for the Detection of Cholera Toxin

    NASA Astrophysics Data System (ADS)

    Archibald, Michelle; Rizal, Binod; Connolly, Timothy; Burns, Michael J.; Naughton, Michael J.; Chiles, Thomas C.; Biology; Physics Collaboration

    We report a nanocoax-based electrochemical sensor for the detection of bacterial toxins using an electrochemical enzyme-linked immunosorbent assay (ELISA) and differential pulse voltammetry (DPV). The device architecture is composed of vertically-oriented, nanoscale coaxial electrodes, with coax cores and shields serving as integrated working and counter electrodes, respectively. Proof-of-concept was demonstrated for the detection of cholera toxin (CT), with a linear dynamic range of detection was 10 ng/ml - 1 µg/ml, and a limit of detection (LOD) of 2 ng/ml. This level of sensitivity is comparable to the standard optical ELISA used widely in clinical applications. The nanocoax array thus matches the detection profile of the standard ELISA while providing a simple electrochemical readout and a miniaturized platform with multiplexing capabilities, toward point-of-care (POC) implementation. In addition, next generation nanocoax devices with extended cores are currently under development, which would provide a POC platform amenable for biofunctionalization of ELISA receptor proteins directly onto the device. This work was supported by the National Institutes of Health (National Cancer Institute Award No. CA137681 and National Institute of Allergy and Infectious Diseases Award No. AI100216).

  1. A multianalyte electrochemical immunosensor based on patterned carbon nanotubes modified substrates for detection of pesticides.

    PubMed

    Liu, Guozhen; Guo, Wenqi; Song, Dandan

    2014-02-15

    A novel multianalyte electrochemical immunosensor based on the assembly of patterned SWNTs on glassy carbon (GC) substrates was developed for simultaneous detection of endosulfan and paraoxon. Based on aryldiazonium salt chemistry, forest of SWNTs can be patterned on GC substrates by C3C bonding using micro contact printing (MCP), which provides an interface showing efficient electron transfer between biomolecules and electrodes. Then redox molecules FDMA and PQQ can be attached to the SWNTs, respectively followed by the attachment of specific epitopes and antibodies. The modified sensing surfaces were characterized by XPS, SEM, AFM and electrochemistry. Based on the current change of specific redox probes, the fabricated immunosensor array can be used for simultaneous detection of endosulfan and paraoxon by a displacement assay. In phosphate buffer solution (50mM, pH 7.0), there is a linear relationship between electrochemical signal of FDMA and the concentration of endosulfan over the range of 0.05-100 ppb with a detection limit of 0.05ppb; the linear range between electrochemical signal of PQQ and the concentration of paraoxon is 2-2500 ppb with a detection limit of 2 ppb. The immunosensor array demonstrates high repeatability, reproducibility, stability and selectivity for the detection of endosulfan and paraoxon.

  2. Electrochemical lateral flow immunosensor for detection and quantification of dengue NS1 protein.

    PubMed

    Sinawang, Prima Dewi; Rai, Varun; Ionescu, Rodica E; Marks, Robert S

    2016-03-15

    An Electrochemical Lateral Flow Immunosensor (ELFI) is developed combining screen-printed gold electrodes (SPGE) enabling quantification together with the convenience of a lateral flow test strip. A cellulose glassy fiber paper conjugate pad retains the marker immunoelectroactive nanobeads which will bind to the target analyte of interest. The specific immunorecognition event continues to occur along the lateral flow bed until reaching the SPGE-capture antibodies at the end of the cellulosic lateral flow strip. The rationale of the immunoassay consists in the analyte antigen NS1 protein being captured selectively and specifically by the dengue NS1 antibody conjugated onto the immunonanobeads thus forming an immunocomplex. With the aid of a running buffer, the immunocomplexes flow and reach the immuno-conjugated electrode surface and form specific sandwich-type detection due to specific, molecular recognition, while unbound beads move along past the electrodes. The successful sandwich immunocomplex formation is then recorded electrochemically. Specific detection of NS1 is translated into an electrochemical signal contributed by a redox label present on the bead-immobilized detection dengue NS1 antibody while a proportional increase of faradic current is observed with increase in analyte NS1 protein concentration. The first generation ELFI prototype is simply assembled in a cassette and successfully demonstrates wide linear range over a concentration range of 1-25 ng/mL with an ultrasensitive detection limit of 0.5 ng/mL for the qualitative and quantitative detection of analyte dengue NS1 protein.

  3. Detection of methyl salicylate using bi-enzyme electrochemical sensor consisting salicylate hydroxylase and tyrosinase.

    PubMed

    Fang, Yi; Bullock, Hannah; Lee, Sarah A; Sekar, Narendran; Eiteman, Mark A; Whitman, William B; Ramasamy, Ramaraja P

    2016-11-15

    Volatile organic compounds have been recognized as important marker chemicals to detect plant diseases caused by pathogens. Methyl salicylate has been identified as one of the most important volatile organic compounds released by plants during a biotic stress event such as fungal pathogen infection. Advanced detection of these marker chemicals could help in early identification of plant diseases and has huge significance for agricultural industry. This work describes the development of a novel bi-enzyme based electrochemical biosensor consisting of salicylate hydroxylase and tyrosinase enzymes immobilized on carbon nanotube modified electrodes. The amperometric detection using the bi-enzyme platform was realized through a series of cascade reactions that terminate in an electrochemical reduction reaction. Electrochemical measurements revealed that the sensitivity of the bi-enzyme sensor was 30.6±2.7µAcm(-2)µM(-1) and the limit of detection and limit of quantification were 13nM (1.80ppb) and 39nM (5.39ppb) respectively. Interference studies showed no significant interference from the other common plant volatile compounds. Synthetic analyte studies revealed that the bi-enzyme based biosensor can be used to reliably detect methyl salicylate released by unhealthy plants. PMID:27236726

  4. Dual-electrode electrochemical detection for poly(dimethylsiloxane)-fabricated capillary electrophoresis microchips.

    PubMed

    Martin, R S; Gawron, A J; Lunte, S M

    2000-07-15

    The development of a poly(dimethylsiloxane)-based (PDMS-based) microchip electrophoresis system employing dual-electrode electrochemical detection is described. This is the first report of dual-electrode electrochemical detection in a microchip format and of electrochemical detection on chips fabricated from PDMS. The device described in this paper consists of a top layer of PDMS containing the separation and injection channels and a bottom glass layer onto which gold detection electrodes have been deposited. The two layers form a tight reversible seal, eliminating the need for high-temperature bonding, which can be detrimental to electrode stability. The channels can also be temporarily removed for cleaning, significantly extending the lifetime of the chip. The performance of the chip was evaluated using catechol as a test compound. The response was linear from 10 to 500 microM with an LOD (S/N = 3) of 4 microM and a sensitivity of 45.9 pA/microM. Collection efficiencies for catechol ranged from 28.7 to 25.9% at field strengths between 200 and 400 V/cm. Dual-electrode detection in the series configuration was shown to be useful for the selective monitoring of species undergoing chemically reversible redox reactions and for peak identification in the electropherogram of an unresolved mixture.

  5. Electrochemical chip-based genomagnetic assay for detection of high-risk human papillomavirus DNA.

    PubMed

    Bartosik, Martin; Durikova, Helena; Vojtesek, Borivoj; Anton, Milan; Jandakova, Eva; Hrstka, Roman

    2016-09-15

    Cervical cancer, being the fourth leading cause of cancer death in women worldwide, predominantly originates from a persistent infection with a high-risk human papillomavirus (HPV). Detection of DNA sequences from these high-risk strains, mostly HPV-16 and HPV-18, represents promising strategy for early screening, which would help to identify women with higher risk of cervical cancer. In developing countries, inadequate screening options lead to disproportionately high mortality rates, making a fast and inexpensive detection schemes highly important. Electrochemical sensors and assays offer an alternative to current methods of detection. We developed an electrochemical-chip based assay, in which target HPV DNA is captured via magnetic bead-modified DNA probes, followed by an antidigoxigenin-peroxidase detection system at screen-printed carbon electrode chips, enabling parallel measurements of eight samples simultaneously. We show sensitive detection in attomoles of HPV DNA, selective discrimination between HPV-16 and HPV-18 and good reproducibility. Most importantly, we show application of the assay into both cancer cell lines and cervical smears from patients. The electrochemical results correlated well with standard methods, making this assay potentially applicable in clinical practice.

  6. Serum Creatinine Detection by a Conducting Polymer Based Electrochemical Sensor to Identify Allograft Dysfunction

    PubMed Central

    Wei, Fang; Cheng, Scott; Korin, Yael; Reed, Elaine F.; Gjertson, David; Ho, Chih-ming; Gritsch, H. Albin; Veale, Jeffrey

    2015-01-01

    Kidney transplant recipients who have abnormally high creatinine levels in their blood often have allograft dysfunction secondary to rejection. Creatinine has become the preferred marker for renal dysfunction and is readily available in hospital clinical settings. We developed a rapid and accurate polymer-based electrochemical point-of-care (POC) assay for creatinine detection from whole blood to identify allograft dysfunction. The creatinine concentrations of 19 blood samples from transplant recipients were measured directly from clinical serum samples by the conducting polymer based electrochemical (EC) sensor arrays. These measurements were compared to the traditional clinical laboratory assay. The time required for detection was less than 5 minutes from sample loading. Sensitivity of the detection was found to be 0.46 mg/dL of creatinine with only 40 μL sample in the creatinine concentration range of 0 mg/dL to 11.33 mg/dL. Signal levels that were detected electrochemically correlated closely with the creatinine blood concentration detected by the UCLA Ronald Reagan Medical Center traditional clinical laboratory assay (correlation coefficient 0.94). This work is encouraging for the development of a rapid and accurate POCT device for measuring creatinine levels in whole blood. PMID:22881369

  7. A single use electrochemical sensor based on biomimetic nanoceria for the detection of wine antioxidants.

    PubMed

    Andrei, Veronica; Sharpe, Erica; Vasilescu, Alina; Andreescu, Silvana

    2016-08-15

    We report the development and characterization of a disposable single use electrochemical sensor based on the oxidase-like activity of nanoceria particles for the detection of phenolic antioxidants. The use of nanoceria in the sensor design enables oxidation of phenolic compounds, particularly those with ortho-dihydroxybenzene functionality, to their corresponding quinones at the surface of a screen printed carbon electrode. Detection is carried out by electrochemical reduction of the resulting quinone at a low applied potential of -0.1V vs the Ag/AgCl electrode. The sensor was optimized and characterized with respect to particle loading, applied potential, response time, detection limit, linear concentration range and sensitivity. The method enabled rapid detection of common phenolic antioxidants including caffeic acid, gallic acid and quercetin in the µM concentration range, and demonstrated good functionality for the analysis of antioxidant content in several wine samples. The intrinsic oxidase-like activity of nanoceria shows promise as a robust tool for sensitive and cost effective analysis of antioxidants using electrochemical detection. PMID:27260442

  8. Electrochemical lateral flow immunosensor for detection and quantification of dengue NS1 protein.

    PubMed

    Sinawang, Prima Dewi; Rai, Varun; Ionescu, Rodica E; Marks, Robert S

    2016-03-15

    An Electrochemical Lateral Flow Immunosensor (ELFI) is developed combining screen-printed gold electrodes (SPGE) enabling quantification together with the convenience of a lateral flow test strip. A cellulose glassy fiber paper conjugate pad retains the marker immunoelectroactive nanobeads which will bind to the target analyte of interest. The specific immunorecognition event continues to occur along the lateral flow bed until reaching the SPGE-capture antibodies at the end of the cellulosic lateral flow strip. The rationale of the immunoassay consists in the analyte antigen NS1 protein being captured selectively and specifically by the dengue NS1 antibody conjugated onto the immunonanobeads thus forming an immunocomplex. With the aid of a running buffer, the immunocomplexes flow and reach the immuno-conjugated electrode surface and form specific sandwich-type detection due to specific, molecular recognition, while unbound beads move along past the electrodes. The successful sandwich immunocomplex formation is then recorded electrochemically. Specific detection of NS1 is translated into an electrochemical signal contributed by a redox label present on the bead-immobilized detection dengue NS1 antibody while a proportional increase of faradic current is observed with increase in analyte NS1 protein concentration. The first generation ELFI prototype is simply assembled in a cassette and successfully demonstrates wide linear range over a concentration range of 1-25 ng/mL with an ultrasensitive detection limit of 0.5 ng/mL for the qualitative and quantitative detection of analyte dengue NS1 protein. PMID:26433352

  9. Carbon Fiber/Epoxy Composite Ring-disk Electrode: Fabrication, Characterization and Application to Electrochemical Detection in Capillary High Performance Liquid Chromatography.

    PubMed

    Xu, Xiaomi; Weber, Stephen G

    2009-05-15

    Carbon fiber/epoxy composite materials, which are manufactured using the pultrusion process, are commercially available in various shapes and sizes at very low cost. Here we demonstrate the application of such a material as an electrochemical detector in a flow system. Cyclic voltammetry shows that the material's electrochemical behavior resembles that of glassy carbon. Using tube and rod composites, we successfully fabricated a ring-disk electrode with a 20 μm gap between the ring and the disk. The narrow gap is favorable for mass transfer in the generator-collector experiment. This composite ring-disk electrode is assembled in a thin-layer radial-flow cell and used as an electrochemical detector. The disk electrode, placed directly opposite to the flow inlet, is operated as a generator electrode with the ring electrode being a collector. The high collection efficiency on the ring electrode (0.8 for a chemically reversible species) enhances the detection selectivity.

  10. Carbon Fiber/Epoxy Composite Ring-disk Electrode: Fabrication, Characterization and Application to Electrochemical Detection in Capillary High Performance Liquid Chromatography

    PubMed Central

    Xu, Xiaomi

    2009-01-01

    Carbon fiber/epoxy composite materials, which are manufactured using the pultrusion process, are commercially available in various shapes and sizes at very low cost. Here we demonstrate the application of such a material as an electrochemical detector in a flow system. Cyclic voltammetry shows that the material's electrochemical behavior resembles that of glassy carbon. Using tube and rod composites, we successfully fabricated a ring-disk electrode with a 20 μm gap between the ring and the disk. The narrow gap is favorable for mass transfer in the generator-collector experiment. This composite ring-disk electrode is assembled in a thin-layer radial-flow cell and used as an electrochemical detector. The disk electrode, placed directly opposite to the flow inlet, is operated as a generator electrode with the ring electrode being a collector. The high collection efficiency on the ring electrode (0.8 for a chemically reversible species) enhances the detection selectivity. PMID:20160941

  11. Immobilization-free electrochemical DNA detection with anthraquinone-labeled pyrrolidinyl peptide nucleic acid probe.

    PubMed

    Kongpeth, Jutatip; Jampasa, Sakda; Chaumpluk, Piyasak; Chailapakul, Orawon; Vilaivan, Tirayut

    2016-01-01

    Electrochemical detection provides a simple, rapid, sensitive and inexpensive method for DNA detection. In traditional electrochemical DNA biosensors, the probe is immobilized onto the electrode. Hybridization with the DNA target causes a change in electrochemical signal, either from the intrinsic signal of the probe/target or through a label or a redox indicator. The major drawback of this approach is the requirement for probe immobilization in a controlled fashion. In this research, we take the advantage of different electrostatic properties between PNA and DNA to develop an immobilization-free approach for highly sequence-specific electrochemical DNA sensing on a screen-printed carbon electrode (SPCE) using a square-wave voltammetric (SWV) technique. Anthraquinone-labeled pyrrolidinyl peptide nucleic acid (AQ-PNA) was employed as a probe together with an SPCE that was modified with a positively-charged polymer (poly quaternized-(dimethylamino-ethyl)methacrylate, PQDMAEMA). The electrostatic attraction between the negatively-charged PNA-DNA duplex and the positively-charged modified SPCE attributes to the higher signal of PNA-DNA duplex than that of the electrostatically neutral PNA probe, resulting in a signal change. The calibration curve of this proposed method exhibited a linear range between 0.35 and 50 nM of DNA target with a limit of detection of 0.13 nM (3SD(blank)/Slope). The sub-nanomolar detection limit together with a small sample volume required (20 μL) allowed detection of <10 fmol (<1 ng) of DNA. With the high specificity of the pyrrolidinyl PNA probe used, excellent discrimination between complementary and various single-mismatched DNA targets was obtained. An application of this new platform for a sensitive and specific detection of isothermally-amplified shrimp's white spot syndrome virus (WSSV) DNA was successfully demonstrated. PMID:26695270

  12. Immobilization-free electrochemical DNA detection with anthraquinone-labeled pyrrolidinyl peptide nucleic acid probe.

    PubMed

    Kongpeth, Jutatip; Jampasa, Sakda; Chaumpluk, Piyasak; Chailapakul, Orawon; Vilaivan, Tirayut

    2016-01-01

    Electrochemical detection provides a simple, rapid, sensitive and inexpensive method for DNA detection. In traditional electrochemical DNA biosensors, the probe is immobilized onto the electrode. Hybridization with the DNA target causes a change in electrochemical signal, either from the intrinsic signal of the probe/target or through a label or a redox indicator. The major drawback of this approach is the requirement for probe immobilization in a controlled fashion. In this research, we take the advantage of different electrostatic properties between PNA and DNA to develop an immobilization-free approach for highly sequence-specific electrochemical DNA sensing on a screen-printed carbon electrode (SPCE) using a square-wave voltammetric (SWV) technique. Anthraquinone-labeled pyrrolidinyl peptide nucleic acid (AQ-PNA) was employed as a probe together with an SPCE that was modified with a positively-charged polymer (poly quaternized-(dimethylamino-ethyl)methacrylate, PQDMAEMA). The electrostatic attraction between the negatively-charged PNA-DNA duplex and the positively-charged modified SPCE attributes to the higher signal of PNA-DNA duplex than that of the electrostatically neutral PNA probe, resulting in a signal change. The calibration curve of this proposed method exhibited a linear range between 0.35 and 50 nM of DNA target with a limit of detection of 0.13 nM (3SD(blank)/Slope). The sub-nanomolar detection limit together with a small sample volume required (20 μL) allowed detection of <10 fmol (<1 ng) of DNA. With the high specificity of the pyrrolidinyl PNA probe used, excellent discrimination between complementary and various single-mismatched DNA targets was obtained. An application of this new platform for a sensitive and specific detection of isothermally-amplified shrimp's white spot syndrome virus (WSSV) DNA was successfully demonstrated.

  13. Electrochemically Reduced Graphene Oxide on Well-Aligned Titanium Dioxide Nanotube Arrays for Betavoltaic Enhancement.

    PubMed

    Chen, Changsong; Wang, Na; Zhou, Peng; San, Haisheng; Wang, Kaiying; Chen, Xuyuan

    2016-09-21

    We report a novel betavoltaic device with significant conversion efficiency by using electrochemically reduced graphene oxide (ERGO) on TiO2 nanotube arrays (TNTAs) for enhancing the absorption of beta radiation as well as the transportation of carriers. ERGO on TNTAs (G-TNTAs) were prepared by electrochemical anodization and subsequently cyclic voltammetry techniques. A 10 mCi of (63)Ni/Ni source was assembled to G-TNTAs to form the sandwich-type betavoltaic devices (Ni/(63)Ni/G-TNTAs/Ti). By I-V measurements, the optimum betavoltaic device exhibits a significant effective energy conversion efficiency of 26.55% with an open-circuit voltage of 2.38 V and a short-circuit current of 14.69 nAcm(-2). The experimental results indicate that G-TNTAs are a high-potential nanocomposite for developing betavoltaic batteries. PMID:27575802

  14. Electrochemically Reduced Graphene Oxide on Well-Aligned Titanium Dioxide Nanotube Arrays for Betavoltaic Enhancement.

    PubMed

    Chen, Changsong; Wang, Na; Zhou, Peng; San, Haisheng; Wang, Kaiying; Chen, Xuyuan

    2016-09-21

    We report a novel betavoltaic device with significant conversion efficiency by using electrochemically reduced graphene oxide (ERGO) on TiO2 nanotube arrays (TNTAs) for enhancing the absorption of beta radiation as well as the transportation of carriers. ERGO on TNTAs (G-TNTAs) were prepared by electrochemical anodization and subsequently cyclic voltammetry techniques. A 10 mCi of (63)Ni/Ni source was assembled to G-TNTAs to form the sandwich-type betavoltaic devices (Ni/(63)Ni/G-TNTAs/Ti). By I-V measurements, the optimum betavoltaic device exhibits a significant effective energy conversion efficiency of 26.55% with an open-circuit voltage of 2.38 V and a short-circuit current of 14.69 nAcm(-2). The experimental results indicate that G-TNTAs are a high-potential nanocomposite for developing betavoltaic batteries.

  15. Significantly enhanced robustness and electrochemical performance of flexible carbon nanotube-based supercapacitors by electrodepositing polypyrrole

    NASA Astrophysics Data System (ADS)

    Chen, Yanli; Du, Lianhuan; Yang, Peihua; Sun, Peng; Yu, Xiang; Mai, Wenjie

    2015-08-01

    Here, we report robust, flexible CNT-based supercapacitor (SC) electrodes fabricated by electrodepositing polypyrrole (PPy) on freestanding vacuum-filtered CNT film. These electrodes demonstrate significantly improved mechanical properties (with the ultimate tensile strength of 16 MPa), and greatly enhanced electrochemical performance (5.6 times larger areal capacitance). The major drawback of conductive polymer electrodes is the fast capacitance decay caused by structural breakdown, which decreases cycling stability but this is not observed in our case. All-solid-state SCs assembled with the robust CNT/PPy electrodes exhibit excellent flexibility, long lifetime (95% capacitance retention after 10,000 cycles) and high electrochemical performance (a total device volumetric capacitance of 4.9 F/cm3). Moreover, a flexible SC pack is demonstrated to light up 53 LEDs or drive a digital watch, indicating the broad potential application of our SCs for portable/wearable electronics.

  16. Enhanced Conversion Efficiency of Cu(In,Ga)Se2 Solar Cells via Electrochemical Passivation Treatment.

    PubMed

    Tsai, Hung-Wei; Thomas, Stuart R; Chen, Chia-Wei; Wang, Yi-Chung; Tsai, Hsu-Sheng; Yen, Yu-Ting; Hsu, Cheng-Hung; Tsai, Wen-Chi; Wang, Zhiming M; Chueh, Yu-Lun

    2016-03-01

    Defect control in Cu(In,Ga)Se2 (CIGS) materials, no matter what the defect type or density, is a significant issue, correlating directly to PV performance. These defects act as recombination centers and can be briefly categorized into interface recombination and Shockley-Read-Hall (SRH) recombination, both of which can lead to reduced PV performance. Here, we introduce an electrochemical passivation treatment for CIGS films that can lower the oxygen concentration at the CIGS surface as observed by X-ray photoelectron spectrometer analysis. Temperature-dependent J-V characteristics of CIGS solar cells reveal that interface recombination is suppressed and an improved rollover condition can be achieved following our electrochemical treatment. As a result, the surface defects are passivated, and the power conversion efficiency performance of the solar cell devices can be enhanced from 4.73 to 7.75%.

  17. Electrochemical biosensor for Mycobacterium tuberculosis DNA detection based on gold nanotubes array electrode platform.

    PubMed

    Torati, Sri Ramulu; Reddy, Venu; Yoon, Seok Soo; Kim, CheolGi

    2016-04-15

    The template assisted electrochemical deposition technique was used for the synthesis of gold nanotubes array (AuNTsA). The morphological structure of the synthesized AuNTsA was observed by scanning electron microscopy and found that the individual nanotubes are around 1.5 μm in length with a diameter of 200 nm. Nanotubes are vertically aligned to the Au thick film, which is formed during the synthesis process of nanotubes. The electrochemical performance of the AuNTsA was compared with the bare Au electrode and found that AuNTsA has better electron transfer surface than bare Au electrode which is due to the high surface area. Hence, the AuNTsA was used as an electrode for the fabrication of DNA hybridization biosensor for detection of Mycobacterium Tuberculosis DNA. The DNA hybridization biosensor constructed by AuNTsA electrode was characterized by cyclic voltammetry technique with Fe(CN)6(3-/4-) as an electrochemical redox indicator. The selectivity of the fabricated biosensor was illustrated by hybridization with complementary DNA and non-complementary DNA with probe DNA immobilized AuNTsA electrode using methylene blue as a hybridization indicator. The developed electrochemical DNA biosensor shows good linear range of complementary DNA concentration from 0.01 ng/μL to 100 ng/μL with high detection limit.

  18. DNA nanostructure-decorated surfaces for enhanced aptamer-target binding and electrochemical cocaine sensors.

    PubMed

    Wen, Yanli; Pei, Hao; Wan, Ying; Su, Yan; Huang, Qing; Song, Shiping; Fan, Chunhai

    2011-10-01

    The sensitivity of aptamer-based electrochemical sensors is often limited by restricted target accessibility and surface-induced perturbation of the aptamer structure, which arise from imperfect packing of probes on the heterogeneous and locally crowded surface. In this study, we have developed an ultrasensitive and highly selective electrochemical aptamer-based cocaine sensor (EACS), based on a DNA nanotechnology-based sensing platform. We have found that the electrode surface decorated with an aptamer probe-pendant tetrahedral DNA nanostructure greatly facilitates cocaine-induced fusion of the split anticocaine aptamer. This novel design leads to a sensitive cocaine sensor with a remarkably low detection limit of 33 nM. It is also important that the tetrahedra-decorated surface is protein-resistant, which not only suits the enzyme-based signal amplification scheme employed in this work, but ensures high selectivity of this sensor when deployed in sera or other adulterated samples.

  19. Graphene-based electrochemical sensor for detection of 2,4,6-trinitrotoluene (TNT) in seawater: the comparison of single-, few-, and multilayer graphene nanoribbons and graphite microparticles.

    PubMed

    Goh, Madeline Shuhua; Pumera, Martin

    2011-01-01

    The detection of explosives in seawater is of great interest. We compared response single-, few-, and multilayer graphene nanoribbons and graphite microparticle-based electrodes toward the electrochemical reduction of 2,4,6-trinitrotoluene (TNT). We optimized parameters such as accumulation time, accumulation potential, and pH. We found that few-layer graphene exhibits about 20% enhanced signal for TNT after accumulation when compared to multilayer graphene nanoribbons. However, graphite microparticle-modified electrode provides higher sensitivity, and there was no significant difference in the performance of single-, few-, and multilayer graphene nanoribbons and graphite microparticles for the electrochemical detection of TNT. We established the limit of detection of TNT in untreated seawater at 1 μg/mL.

  20. Facile synthesis of hexagonal-shaped polypyrrole self-assembled particles for the electrochemical detection of dopamine

    NASA Astrophysics Data System (ADS)

    Lee, Chung-Yi; Hsu, Di-Yao; Prasannan, Adhimoorthy; Kalaivani, Raman; Hong, Po-Da

    2016-02-01

    Nanomaterials have been used as an electroactive medium to enhance the efficiency of bio/chemical sensors, primarily when synergy is reached upon mixing different materials. In this study, we report on the facile synthesis of hexagonal-shaped plate-like polypyrrole (PPY-IC) prepared through inclusion polymerization of the host-guest pyrrole monomeric inclusion complex of β-cyclodextrin (β-CD) to be used in the detection of the neurotransmitter dopamine (DA). The amount of the monomer complex plays a crucial role in the fabrication of well-defined hexagonal-shaped PPY-IC through intermolecular interactions such as π-π interactions and hydrogen bonding between the β-CD and PPY. The microstructure and morphology of the PPY-IC were examined by using various analytical techniques and a tentative mechanism for the growth process proposed which elucidates the formation of the hierarchical structure of the PPY-IC. Cyclo-voltammetry was performed with a PPY-IC modified glassy carbon electrode (GCE) for the electrochemical detection of DA. The concepts behind the novel architecture of the PPY-IC modified electrodes have potential for the production of materials to be used in electrochemical sensors and biosensors.

  1. Acetylcholinesterase Biosensors for Electrochemical Detection of Organophosphorus Compounds: A Review

    PubMed Central

    Dhull, Vikas; Gahlaut, Anjum; Dilbaghi, Neeraj

    2013-01-01

    The exponentially growing population, with limited resources, has exerted an intense pressure on the agriculture sector. In order to achieve high productivity the use of pesticide has increased up to many folds. These pesticides contain organophosphorus (OP) toxic compounds which interfere with the proper functioning of enzyme acetylcholinesterase (AChE) and finally affect the central nervous system (CNS). So, there is a need for routine, continuous, on spot detection of OP compounds which are the main limitations associated with conventional analytical methods. AChE based enzymatic biosensors have been reported by researchers as the most promising tool for analysis of pesticide level to control toxicity and for environment conservation. The present review summarises AChE based biosensors by discussing their characteristic features in terms of fabrication, detection limit, linearity range, time of incubation, and storage stability. Use of nanoparticles in recently reported fabrication strategies has improved the efficiency of biosensors to a great extent making them more reliable and robust. PMID:24383001

  2. Electrochemical methods for detection of post-translational modifications of proteins.

    PubMed

    Shumyantseva, Victoria V; Suprun, Elena V; Bulko, Tatiana V; Archakov, Alexander I

    2014-11-15

    Post-translational modifications of proteins play a key role in the regulation of various cellular processes. The analysis and identification of post-translational modifications are probably the most versatile and difficult, but also most frequently studied area of interest in proteomics research. This review focuses on the electroactivity of amino acids as a tool for analysis of post-translational modifications of proteins. The most attention is paid to the electrochemical detection of phosphorylation/dephosphorylation and glycosylation of proteins, to the best-studied and functionally-significant modifications, and, also, to the electrochemical analysis of activity of enzymes responsible for carrying out phosphorylation/dephosphorylation of proteins. Recent advances in electrochemistry with special references to proteomics are outlined and innovative technologies for protein detection are highlighted.

  3. Enzymatic electrochemical detection coupled to multivariate calibration for the determination of phenolic compounds in environmental samples.

    PubMed

    Hernandez, Silvia R; Kergaravat, Silvina V; Pividori, Maria Isabel

    2013-03-15

    An approach based on the electrochemical detection of the horseradish peroxidase enzymatic reaction by means of square wave voltammetry was developed for the determination of phenolic compounds in environmental samples. First, a systematic optimization procedure of three factors involved in the enzymatic reaction was carried out using response surface methodology through a central composite design. Second, the enzymatic electrochemical detection coupled with a multivariate calibration method based in the partial least-squares technique was optimized for the determination of a mixture of five phenolic compounds, i.e. phenol, p-aminophenol, p-chlorophenol, hydroquinone and pyrocatechol. The calibration and validation sets were built and assessed. In the calibration model, the LODs for phenolic compounds oscillated from 0.6 to 1.4 × 10(-6) mol L(-1). Recoveries for prediction samples were higher than 85%. These compounds were analyzed simultaneously in spiked samples and in water samples collected close to tanneries and landfills. PMID:23598144

  4. General approach for electrochemical detection of persistent pharmaceutical micropollutants: Application to acetaminophen.

    PubMed

    Shi, S; Reisberg, S; Anquetin, G; Noël, V; Pham, M C; Piro, B

    2015-10-15

    We propose in this work a general and versatile methodology for electrochemical monitoring of persistent pharmaceutical micropollutants. The system presented is based on an electroactive and electropolymerized hapten (mimetic molecule of the pollutant to be detected) and a specific antibody that competitively binds either the hapten or the pollutant. The current delivered by the device depends on this competitive equilibrium and therefore on the pollutant's concentration. The determination of the pharmaceutical product operates within minutes, using square wave voltammetry without labeling or addition of a reactant in solution; the competitive hapten/antibody transduction produces a "signal-on" (a current increase). Applied to acetaminophen, this electrochemical immunosensor presents a very low detection limit of ca. 10 pM, (S/N=3) and a very high selectivity towards structural analogs (aspirin, BPA, and piperazine) even in a mixture. PMID:25982729

  5. Highly specific and sensitive electrochemical genotyping via gap ligation reaction and surface hybridization detection.

    PubMed

    Huang, Yong; Zhang, Yan-Li; Xu, Xiangmin; Jiang, Jian-Hui; Shen, Guo-Li; Yu, Ru-Qin

    2009-02-25

    This paper developed a novel electrochemical genotyping strategy based on gap ligation reaction with surface hybridization detection. This strategy utilized homogeneous enzymatic reactions to generate molecular beacon-structured allele-specific products that could be cooperatively annealed to capture probes stably immobilized on the surface via disulfide anchors, thus allowing ultrasensitive surface hybridization detection of the allele-specific products through redox tags in close proximity to the electrode. Such a unique biphasic architecture provided a universal methodology for incorporating enzymatic discrimination reactions in electrochemical genotyping with desirable reproducibility, high efficiency and no interferences from interficial steric hindrance. The developed technique was demonstrated to show intrinsic high sensitivity for direct genomic analysis, and excellent specificity with discriminativity of single nucleotide variations.

  6. Enzymatic electrochemical detection coupled to multivariate calibration for the determination of phenolic compounds in environmental samples.

    PubMed

    Hernandez, Silvia R; Kergaravat, Silvina V; Pividori, Maria Isabel

    2013-03-15

    An approach based on the electrochemical detection of the horseradish peroxidase enzymatic reaction by means of square wave voltammetry was developed for the determination of phenolic compounds in environmental samples. First, a systematic optimization procedure of three factors involved in the enzymatic reaction was carried out using response surface methodology through a central composite design. Second, the enzymatic electrochemical detection coupled with a multivariate calibration method based in the partial least-squares technique was optimized for the determination of a mixture of five phenolic compounds, i.e. phenol, p-aminophenol, p-chlorophenol, hydroquinone and pyrocatechol. The calibration and validation sets were built and assessed. In the calibration model, the LODs for phenolic compounds oscillated from 0.6 to 1.4 × 10(-6) mol L(-1). Recoveries for prediction samples were higher than 85%. These compounds were analyzed simultaneously in spiked samples and in water samples collected close to tanneries and landfills.

  7. Highly conductive nanostructured C-TiO2 electrodes with enhanced electrochemical stability and double layer charge storage capacitance.

    PubMed

    Mole, Fraser; Wang, Jue; Clayton, Daniel A; Xu, Cailing; Pan, Shanlin

    2012-07-17

    The present work reports the structural and electrochemical properties of carbon-modified nanostructured TiO(2) electrodes (C-TiO(2)) prepared by anodizing titanium in a fluoride-based electrolyte followed by thermal annealing in an atmosphere of methane and hydrogen in the presence of Fe precursors. The C-TiO(2) nanostructured electrodes are highly conductive and contain more than 1 × 10(10) /cm(2) of nanowires or nanotubes to enhance their double layer charge capacitance and electrochemical stability. Electrogenerated chemiluminescence (ECL) study shows that a C-TiO(2) electrode can replace noble metal electrodes for ultrasensitive ECL detection. Dynamic potential control experiments of redox reactions show that the C-TiO(2) electrode has a broad potential window for a redox reaction. Double layer charging capacitance of the C-TiO(2) electrode is found to be 3 orders of magnitude higher than an ideal planar electrode because of its high surface area and efficient charge collection capability from the nanowire structured surface. The effect of anodization voltage, surface treatment with Fe precursors for carbon modification, the barrier layer between the Ti substrate, and anodized layer on the double layer charging capacitance is studied. Ferrocene carboxylic acid binds covalently to the anodized Ti surface forming a self-assembled monolayer, serving as an ideal precursor layer to yield C-TiO(2) electrodes with better double layer charging performance than the other precursors.

  8. Label-free electrochemical immunosensor based on enhanced signal amplification between Au@Pd and CoFe2O4/graphene nanohybrid

    PubMed Central

    Zhang, Yong; Li, Jiaojiao; Wang, Zhiling; Ma, Hongmin; Wu, Dan; Cheng, Qianhe; Wei, Qin

    2016-01-01

    The improvement of sensitivity of electrochemical immunosensor can be achieved via two approaches: increasing loading capacities of antibody and enlarging responding electrochemical signals. Based on these, CoFe2O4/graphene nanohybrid (CoFe2O4/rGO) as support was firstly used for preparing electrochemical biosensor, and with the addition of Au@Pd nanorods (NRs) as mimic enzyme, a label-free electrochemical immunosensor was prepared. Due to the high electrical conductivity, open porous structure and large loading capacities of CoFe2O4/rGO, the enhanced signal amplification between Au@Pd NRs and CoFe2O4/rGO was studied. Fabricated as a novel substrate, the prepared immunosensor had a good analytical performance and exhibited a wide linear range from 0.01 to 18.0 ng·mL−1 with a low detection limit of 3.3 pg·mL−1 for estradiol, which was succeeded in applying to detect estradiol in the natural water. PMID:26987503

  9. Complexes of carbon nanotubes with oligonucleotides in thin Langmuir-Blodgett films to detect electrochemically hybridization

    NASA Astrophysics Data System (ADS)

    Egorov, A. S.; Egorova, V. P.; Krylova, H. V.; Lipnevich, I. V.; Orekhovskaya, T. I.; Veligura, A. A.; Govorov, M. I.; Shulitsky, B. G.

    2014-10-01

    Self-assembled complexes consisting of thin multi-walled carbon nanotubes (MWCNTs) and DNA-oligonucleotides which are able to a cooperative binding to complementary oligonucleotides have been investigated. It was establised a high-performance charge transport in nanostructured Langmuir-Blodgett complexes thin MWCNTs/DNA. A method to electrochemically detect DNA hybridization on the self-organized structures has been proposed.

  10. PMMA-based capillary electrophoresis electrochemical detection microchip fabrication

    NASA Astrophysics Data System (ADS)

    Horng, Ray-Hua; Han, Pin; Chen, Hung-Yu; Lin, Kuan-Wen; Tsai, Tung-Mung; Zen, Jyh-Myng

    2005-01-01

    In this paper, a 50 µm (depth) × 50 µm (width) microfluidic channel is made on a poly(methyl methacrylate) (PMMA) substrate using thick photoresist. Openings were drilled for buffer reservoirs on an additional piece of PMMA. A final PMMA/patterned photoresist/PMMA sandwich configuration was completed using a bonding process. The thick photoresist was used as the adhesion layer and also as the microfluidic system. Using screen-printed technology for carbon and silver electrode fabrication, the microchip electrophoretic device functions were demonstrated. Successful detection of uric acid and L-ascorbic acid (the main components in human urine) validates the functionality of the proposed system. Successful ascorbic and uric acid separation in a sample from a urine donor who had consumed 500 mg of vitamins verified the proposed biochip.

  11. Enhanced detection of glycoproteins in polyacrylamide gels.

    PubMed

    Muñoz, G; Marshall, S; Cabrera, M; Horvat, A

    1988-05-01

    A highly sensitive and simple method to enhance detection of glycoproteins resolved by either one- or two-dimensional polyacrylamide gel electrophoresis is described. The method is a modification of the procedure described by D. Fargeaud et al. (D. Fargeaud, J. C. Benoit, F. Kato, and G. Chappuis (1984) Arch. Virol. 80, 69-82) that uses concanavalin A conjugated with fluorescein isothyocyanate to detect the carbohydrate moiety of glycoproteins. Briefly, the electrophoresed gel is exposed to the fluorescent lectin, thoroughly washed, and sequentially transferred to 50% methanol in deionized water and to absolute methanol. The result is an abrupt dehydration of the gel which turns evenly white and stiff. At least a twofold enhancement of fluorescence is obtained as detected by exposing the treated gel to an appropriate uv source. The sensitivity of the procedure allows us to detect purified immunoglobulin molecules by their carbohydrate content in the range of 0.2 microgram of total protein. The specificity of the detection is demonstrated by a comparison with the corresponding polypeptide profile obtained by silver nitrate staining of the gel. PMID:3394948

  12. Enhanced detection of glycoproteins in polyacrylamide gels.

    PubMed

    Muñoz, G; Marshall, S; Cabrera, M; Horvat, A

    1988-05-01

    A highly sensitive and simple method to enhance detection of glycoproteins resolved by either one- or two-dimensional polyacrylamide gel electrophoresis is described. The method is a modification of the procedure described by D. Fargeaud et al. (D. Fargeaud, J. C. Benoit, F. Kato, and G. Chappuis (1984) Arch. Virol. 80, 69-82) that uses concanavalin A conjugated with fluorescein isothyocyanate to detect the carbohydrate moiety of glycoproteins. Briefly, the electrophoresed gel is exposed to the fluorescent lectin, thoroughly washed, and sequentially transferred to 50% methanol in deionized water and to absolute methanol. The result is an abrupt dehydration of the gel which turns evenly white and stiff. At least a twofold enhancement of fluorescence is obtained as detected by exposing the treated gel to an appropriate uv source. The sensitivity of the procedure allows us to detect purified immunoglobulin molecules by their carbohydrate content in the range of 0.2 microgram of total protein. The specificity of the detection is demonstrated by a comparison with the corresponding polypeptide profile obtained by silver nitrate staining of the gel.

  13. Enhancement of electrical conductivity and electrochemical activity of hydrogenated amorphous carbon by incorporating boron atoms

    NASA Astrophysics Data System (ADS)

    Naragino, Hiroshi; Yoshinaga, Kohsuke; Nakahara, Akira; Tanaka, Sakuya; Honda, Kensuke

    2013-06-01

    Conductive boron-doped hydrogenated amorphous carbon (B-DLC) thin films were successfully synthesized with RF plasma-enhanced CVD method. By incorporating boron atoms in amorphous carbon, conduction types were changed from n- to p-type, and volume resistivity was decreased from 30.4 (non-doped) to 6.36 × 10-2 Ω cm (B/C = 2.500 atom%). B-DLC film with sp2/(sp2 + sp3) carbons of 75 atom% exhibited high resistance to electrochemically-induced corrosion in strong acid solution. Furthermore, it was clarified that boron atoms in DLC could enhance kinetics of hydrogen evolution during water electrolysis at B-DLC surface. B-DLC is, therefore, a promising electrode material for hydrogen production by increasing the concentration of boron atoms in B-DLC and enhancing the reactivity of H2 evolution.

  14. Label-free electrochemical impedance detection of kinase and phosphatase activities using carbon nanofiber nanoelectrode arrays

    PubMed Central

    Li, Yifen; Syed, Lateef; Liu, Jianwei; Hua, Duy H.; Li, Jun

    2012-01-01

    We demonstrate the feasibility of a label-free electrochemical method to detect the kinetics of phosphorylation and dephosphorylation of surface-attached peptides catalyzed by kinase and phosphatase, respectively. The peptides with a sequence specific to c-Src tyrosine kinase and protein tyrosine phosphatase 1B (PTP1B) were first validated with ELISA-based protein tyrosine kinase assay and then functionalized on vertically aligned carbon nanofiber (VACNF) nanoelectrode arrays (NEAs). Real-time electrochemical impedance spectroscopy (REIS) measurements showed reversible impedance changes upon the addition of c-Src kinase and PTP1B phosphatase. Only a small and unreliable impedance variation was observed during the peptide phosphorylation, but a large and fast impedance decrease was observed during the peptide dephosphorylation at different PTP1B concentrations. The REIS data of dephosphorylation displayed a well-defined exponential decay following the Michaelis-Menten heterogeneous enzymatic model with a specific constant, kcat/Km, of (2.1 ± 0.1) × 107 M−1 s−1. Consistent values of the specific constant was measured at PTP1B concentration varying from 1.2 to 2.4 nM with the corresponding electrochemical signal decay constant varying from 38.5 to 19.1 s. This electrochemical method can be potentially used as a label-free method for profiling enzyme activities in fast reactions. PMID:22935373

  15. Ion sensors based on novel fiber organic electrochemical transistors for lead ion detection.

    PubMed

    Wang, Yuedan; Zhou, Zhou; Qing, Xing; Zhong, Weibing; Liu, Qiongzhen; Wang, Wenwen; Li, Mufang; Liu, Ke; Wang, Dong

    2016-08-01

    Fiber organic electrochemical transistors (FECTs) based on polypyrrole and nanofibers have been prepared for the first time. FECTs exhibited excellent electrical performances, on/off ratios up to 10(4) and low applied voltages below 2 V. The ion sensitivity behavior of the fiber organic electrochemical transistors was investigated. It exhibited that the transfer curve of FECTs shifted to lower gate voltage with increasing cations concentration, the sensitivity reached to 446 μA/dec in the 10(-5)-10(-2) M Pb(2+) concentration range. The ion selective properties of the FECTs have also been systematically studied for the detection of potassium, calcium, aluminum, and lead ions. The devices with different cations showed great difference in response curves. It was suitable for selectively monitoring Pb(2+) with respect to other cations. The results indicated FECTs were very effective for electrochemical sensing of lead ion, which opened a promising perspective for wearable electronics in healthcare and biological application. Graphical Abstract The schematic diagram of fiber organic electrochemical transistors based on polypyrrole and nanofibers for ion sensing.

  16. Selective detection of endotoxin using an impedance aptasensor with electrochemically deposited gold nanoparticles.

    PubMed

    Su, Wenqiong; Kim, Sung-Eun; Cho, MiSuk; Nam, Jae-Do; Choe, Woo-Seok; Lee, Youngkwan

    2013-01-01

    Using a single-stranded DNA (ssDNA) aptamer exhibiting high binding affinity (Kd = 12 nM) to endotoxin as a probe, an impedance sensor where aptamer-conjugated gold nanoparticles (AuNPs) were electrochemically deposited on a gold electrode was fabricated and its performance in regard to endotoxin detection assessed. AuNPs have been employed widely as biosensors because of their unique physical and chemical properties. In order to maximize the performance of the impedance aptasensor on endotoxin detection, some critical factors affecting aptamer conjugation to AuNPs and target recognition ability (i.e. concentrations of aptamer coupled with AuNPs, pH, ion strength and cation effect at the time of aptamer-endotoxin interaction) were optimized. Electrochemical impendence spectroscopy, cyclic voltametry, atomic force microscope, scanning electron microscope and quartz crystal microbalance were employed to characterize all the modification/detection procedures during the sensor fabrication. The developed aptasensor showed a broad linear dynamic detection range (0.01-10.24 ng/ml) with a very low detection limit for endotoxin (0.005 ng/ml), despite the presence of several biomolecules (e.g. plasmid DNA, RNA, serum albumin, Glc and sucrose) known to interfere with other endotoxin assays. The demonstrated aptasensor required a detection time of only 10 min, providing a simple and fast analytical method to specifically detect endotoxin from complex biological liqors.

  17. Selective detection of endotoxin using an impedance aptasensor with electrochemically deposited gold nanoparticles.

    PubMed

    Su, Wenqiong; Kim, Sung-Eun; Cho, MiSuk; Nam, Jae-Do; Choe, Woo-Seok; Lee, Youngkwan

    2013-01-01

    Using a single-stranded DNA (ssDNA) aptamer exhibiting high binding affinity (Kd = 12 nM) to endotoxin as a probe, an impedance sensor where aptamer-conjugated gold nanoparticles (AuNPs) were electrochemically deposited on a gold electrode was fabricated and its performance in regard to endotoxin detection assessed. AuNPs have been employed widely as biosensors because of their unique physical and chemical properties. In order to maximize the performance of the impedance aptasensor on endotoxin detection, some critical factors affecting aptamer conjugation to AuNPs and target recognition ability (i.e. concentrations of aptamer coupled with AuNPs, pH, ion strength and cation effect at the time of aptamer-endotoxin interaction) were optimized. Electrochemical impendence spectroscopy, cyclic voltametry, atomic force microscope, scanning electron microscope and quartz crystal microbalance were employed to characterize all the modification/detection procedures during the sensor fabrication. The developed aptasensor showed a broad linear dynamic detection range (0.01-10.24 ng/ml) with a very low detection limit for endotoxin (0.005 ng/ml), despite the presence of several biomolecules (e.g. plasmid DNA, RNA, serum albumin, Glc and sucrose) known to interfere with other endotoxin assays. The demonstrated aptasensor required a detection time of only 10 min, providing a simple and fast analytical method to specifically detect endotoxin from complex biological liqors. PMID:23165992

  18. A sensitive nanoporous gold-based electrochemical aptasensor for thrombin detection.

    PubMed

    Qiu, Huajun; Sun, Yanli; Huang, Xirong; Qu, Yinbo

    2010-08-01

    An attempt was made in the present paper to develop a nanoporous gold (NPG)-based electrochemical aptasensor for thrombin detection. The substrate electrode NPG was in situ fabricated by a facile one-step square wave potential pulse (SWPP) treatment. The treatment involved repeated gold oxidation-reduction and intensive H(2) bubbles evolution. After 100min treatment, the active surface area of Au increased greatly (34 times). The electrochemical aptasensor was fabricated using a layer-by-layer assembling strategy. A "sandwich" structure was formed via thrombin connecting the aptamer-modified NPG and the aptamer-modified Au nanoparticles (AuNPs). The AuNPs was modified with two kinds of single strand DNA (ssDNA). One was aptamer of thrombin, but the other was not, reducing the cross-reaction between thrombin and its aptamer on the same AuNP. The electrochemical signal produced by the [Ru(NH(3))(6)](3+) bound to ssDNA via electrostatic interaction was measured by chronocoulometry. Due to the amplification effects of both NPG and AuNPs, this novel NPG-based aptasensor could detect thrombin quantitatively in the range of 0.01-22nM with a detection limit as low as 30fM. The present aptasensor also exhibited excellent selectivity, stability and reusability.

  19. Electrochemical biosensors based on nanofibres for cardiac biomarker detection: A comprehensive review.

    PubMed

    Rezaei, Babak; Ghani, Mozhdeh; Shoushtari, Ahmad Mousavi; Rabiee, Mohammad

    2016-04-15

    The vital importance of early and accurate diagnosis of cardiovascular diseases (CVDs) to prevent the irreversible damage or even death of patients has driven the development of biosensor devices for detection and quantification of cardiac biomarkers. Electrochemical biosensors offer rapid sensing, low cost, portability and ease of use. Over the past few years, nanotechnology has contributed to a tremendous improvement in the sensitivity of biosensors. In this review, the authors summarise the state-of-the-art of the application of one particular type of nanostructured material, i.e. nanofibres, for use in electrochemical biosensors for the ultrasensitive detection of cardiac biomarkers. A new way of classifying the nanofibre-based electrochemical biosensors according to the electrical conductance and the type of nanofibres is presented. Some key data from each article reviewed are highlighted, including the mechanism of detection, experimental conditions and the response range of the biosensor. The primary aim of this review is to emphasise the prospects for nanofibres for the future development of biosensors in diagnosis of CVDs as well as considering how to improve their characteristics for application in medicine.

  20. Detection of Interferon gamma using graphene and aptamer based FET-like electrochemical biosensor.

    PubMed

    Farid, Sidra; Meshik, Xenia; Choi, Min; Mukherjee, Souvik; Lan, Yi; Parikh, Devanshi; Poduri, Shripriya; Baterdene, Undarmaa; Huang, Ching-En; Wang, Yung Yu; Burke, Peter; Dutta, Mitra; Stroscio, Michael A

    2015-09-15

    One of the primary goals in the scientific community is the specific detection of proteins for the medical diagnostics and biomedical applications. Interferon-gamma (IFN-γ) is associated with the tuberculosis susceptibility, which is one of the major health problems globally. We have therefore developed a DNA aptamer-based electrochemical biosensor that is used for the detection of IFN-γ with high selectivity and sensitivity. A graphene monolayer-based FET-like structure is incorporated on a PDMS substrate with the IFN-γ aptamer attached to graphene. Addition of target molecule induces a change in the charge distribution in the electrolyte, resulting in increase in electron transfer efficiency that was actively sensed by monitoring the change in current from the device. Change in current appears to be highly sensitive to the IFN-γ concentrations ranging from nanomolar (nM) to micromolar (μM) range. The detection limit of our IFN-γ electrochemical biosensor is found to be 83 pM. Immobilization of aptamer on graphene surface is verified using unique structural approach by Atomic Force Microscopy. Such simple and sensitive electrochemical biosensor has potential applications in infectious disease monitoring, immunology and cancer research in the future.

  1. A new electrochemical biosensor for DNA detection based on molecular recognition and lead sulfide nanoparticles.

    PubMed

    Fan, Hao; Zhao, Kun; Lin, Yan; Wang, Xiaoyun; Wu, Bo; Li, Qianggen; Cheng, Lin

    2011-12-15

    In this paper, we constructed a new electrochemical biosensor for DNA detection based on a molecule recognition technique. In this sensing protocol, a novel dual-labeled DNA probe (DLP) in a stem-loop structure was employed, which was designed with dabcyl labeled at the 3' end as a guest molecule, and with a Pb nanoparticle labeled at the 5' end as electrochemical tag to indicate hybridization. One α-cyclodextrin-modified electrode (α-CD/MCNT/GCE) was used for capturing the DNA hybridization. Initially, the DLP was in the "closed" state in the absence of the target, which shielded dabcyl from the bulky α-CD/MCNT/GCE conjugate due to a steric effect. After hybridization, the loop sequence (16 bases) formed a rigid duplex with the target, breaking the relatively shorter stem duplex (6 bases). Consequently, dabcyl was forced away from the Pb nanoparticle and became accessible by the electrode. Therefore, the target hybridization event can be sensitively transduced via detecting the electrochemical reduction current signal of Pb. Using this method, as low as 7.1×10(-10)M DNA target had been detected with excellent differentiation ability for even a single mismatch.

  2. Development of an electrochemical immunoassay for detection of gatifloxacin in swine urine.

    PubMed

    Yi, Jian; Meng, Meng; Liu, Zhong-qiu; Zhi, Jin-fang; Zhang, Yuan-yang; Xu, Jing; Wang, Ya-bin; Liu, Jin-ting; Xi, Ri-mo

    2012-02-01

    To detect gatifloxacin (GAT) residue in swine urine, an electrochemical immunoassay was established. An indirect competitive immunoassay was developed, in which the coating antigen is immobilized in an enzyme-linked immunosorbent assay (ELISA) plate and GAT residue from the sample competes with the limited binding sites in added anti-GAT antibody. Horseradish peroxidase (HRP) conjugated to goat anti-rabbit IgG was used as the enzymatic label. A carbon fiber working electrode was constructed and current signals were detected by using hydrogen peroxide as a substrate and hydroquinone as an electrochemical mediator. The electrochemical immunoassay was evaluated by analysis of GAT in buffer or swine urine and an average value of half inhibition concentration (IC(50)) of 8.9 ng/ml was obtained. Excellent specificity of the antibody was achieved with little cross-reaction with lomefloxacin (3.0%), ciprofloxacin (3.0%), and ofloxacin (1.9%) among commonly used (fluoro)quinolones. In conclusion, the immunoassay system developed in this research can be used as a rapid, powerful and on-site analytical tool to detect GAT residue in foods and food products.

  3. Electrochemical detection of leukemia oncogenes using enzyme-loaded carbon nanotube labels

    SciTech Connect

    Lee, Ai Cheng; Du, Dan; Chen, Baowei; Heng, Chew-Kiat; Lim, Tit-Meng; Lin, Yuehe

    2014-09-07

    Here we describe an ultrasensitive electrochemical nucleic acids assay amplified by carbon nanotubes (CNTs)-based labels for the detection of human acute lymphocytic leukemia (ALL) related p185 BCR-ABL fusion transcript. The carboxylated CNTs were functionalized with horseradish peroxidase (HRP) molecules and target-specific detection probes (DP) via diimide-activated amidation, and used to label and amplify target hybridization signal. The activity of captured HRP was monitored by square-wave voltammetry measuring the electroactive enzymatic product in the presence of 2-aminophenol and hydrogen peroxide substrate solution. The effect of DP and HRP loading of the CNT-based labels on its signal-to-noise ratio of electrochemical detection was studied systematically for the first time. Under optimized conditions, the signal-amplified assay achieved a detection limit of 83 fM targets oligonuecleotides and a 4-order wide dynamic range of target concentration. The resulting assay allowed a robust discrimination between the perfect match and a three-base mismatch sequence. When subjected to full-length (491 bp) DNA oncogene, the approach demonstrated a detection limit of approximately 33 pg of the target gene. The high sensitivity and specificity of assay enabled PCR-free detection of target transcripts in as little as 65 ng of mRNA extracted from positive ALL cell lines SUP-B15, in comparison to those obtained from negative cell lines HL-60. The approach holds promise for simple, low cost and ultrasensitive electrochemical nucleic acids detection in portable devices, point-of-care and early disease diagnostic applications.

  4. An Enhanced Smoke Detection Using MODIS Measurements

    NASA Astrophysics Data System (ADS)

    Xie, Y.; Qu, J.; Xiong, X.; Hao, X.; Wang, W.; Wang, L.

    2005-12-01

    Smoke emitted from wildfire fires or prescribed fires is one of the major pollutions that pose a risk to human health and affect the air quality significantly. The remote sensing technique has been demonstrated as an efficient approach for detecting and tracing smoke plume. As a mixture pollutant, smoke does not have stable spectral signature because of diversified component mixing levels in different situation, but it has some particular characteristics different from others such as cloud, soil, water and so on. In earlier studies, we have already developed a multi-threshold algorithm to detect smoke in the eastern United States by combining both MODIS reflective solar bands and thermal emissive bands measurements. In order to apply out approach to global scale, we have enhanced the smoke detection algorithm by taking the land surface type into account. Smoke pixels will be output as well as the confidence in the quality of product in final result. In addition, smoke detection is also helpful to fire detection. With current fire detection algorithm, some small and cool fires can not be detected. However, understanding the features and spread direction of smoke can provide us a potential way to identify these fires.

  5. Fusion and normalization to enhance anomaly detection

    NASA Astrophysics Data System (ADS)

    Mayer, R.; Atkinson, G.; Antoniades, J.; Baumback, M.; Chester, D.; Edwards, J.; Goldstein, A.; Haas, D.; Henderson, S.; Liu, L.

    2009-05-01

    This study examines normalizing the imagery and the optimization metrics to enhance anomaly and change detection, respectively. The RX algorithm, the standard anomaly detector for hyperspectral imagery, more successfully extracts bright rather than dark man-made objects when applied to visible hyperspectral imagery. However, normalizing the imagery prior to applying the anomaly detector can help detect some of the problematic dark objects, but can also miss some bright objects. This study jointly fuses images of RX applied to normalized and unnormalized imagery and has a single decision surface. The technique was tested using imagery of commercial vehicles in urban environment gathered by a hyperspectral visible/near IR sensor mounted in an airborne platform. Combining detections first requires converting the detector output to a target probability. The observed anomaly detections were fitted with a linear combination of chi square distributions and these weights were used to help compute the target probability. Receiver Operator Characteristic (ROC) quantitatively assessed the target detection performance. The target detection performance is highly variable depending on the relative number of candidate bright and dark targets and false alarms and controlled in this study by using vegetation and street line masks. The joint Boolean OR and AND operations also generate variable performance depending on the scene. The joint SUM operation provides a reasonable compromise between OR and AND operations and has good target detection performance. In addition, new transforms based on normalizing correlation coefficient and least squares generate new transforms related to canonical correlation analysis (CCA) and a normalized image regression (NIR). Transforms based on CCA and NIR performed better than the standard approaches. Only RX detection of the unnormalized of the difference imagery in change detection provides adequate change detection performance.

  6. Enhanced photoacoustic detection using photonic crystal substrate

    NASA Astrophysics Data System (ADS)

    Zhao, Yunfei; Liu, Kaiyang; McClelland, John; Lu, Meng

    2014-04-01

    This paper demonstrates the enhanced photoacoustic sensing of surface-bound light absorbing molecules and metal nanoparticles using a one-dimensional photonic crystal (PC) substrate. The PC structure functions as an optical resonator at the wavelength where the analyte absorption is strong. The optical resonance of the PC sensor provides an intensified evanescent field with respect to the excitation light source and results in enhanced optical absorption by surface-immobilized samples. For the analysis of a light absorbing dye deposited on the PC surface, the intensity of photoacoustic signal was enhanced by more than 10-fold in comparison to an un-patterned acrylic substrate. The technique was also applied to detect gold nanorods and exhibited more than 40 times stronger photoacoustic signals. The demonstrated approach represents a potential path towards single molecule absorption spectroscopy with greater performance and inexpensive instrumentation.

  7. Enhanced photoacoustic detection using photonic crystal substrate

    SciTech Connect

    Zhao, Yunfei; Liu, Kaiyang; McClelland, John; Lu, Meng

    2014-04-21

    This paper demonstrates the enhanced photoacoustic sensing of surface-bound light absorbing molecules and metal nanoparticles using a one-dimensional photonic crystal (PC) substrate. The PC structure functions as an optical resonator at the wavelength where the analyte absorption is strong. The optical resonance of the PC sensor provides an intensified evanescent field with respect to the excitation light source and results in enhanced optical absorption by surface-immobilized samples. For the analysis of a light absorbing dye deposited on the PC surface, the intensity of photoacoustic signal was enhanced by more than 10-fold in comparison to an un-patterned acrylic substrate. The technique was also applied to detect gold nanorods and exhibited more than 40 times stronger photoacoustic signals. The demonstrated approach represents a potential path towards single molecule absorption spectroscopy with greater performance and inexpensive instrumentation.

  8. Quantitative visualization of molecular transport through porous membranes: enhanced resolution and contrast using intermittent contact-scanning electrochemical microscopy.

    PubMed

    McKelvey, Kim; Snowden, Michael E; Peruffo, Massimo; Unwin, Patrick R

    2011-09-01

    The use of intermittent contact-scanning electrochemical microscopy (IC-SECM) in diffusion-limited amperometric mode to visualize and quantify mass transport through multiporous membranes is described using dentin as a model example. The IC mode of SECM employs the damping of a vertically modulated ultramicroelectrode (UME) to achieve positioning close to the receptor side of a membrane. In this way the UME can detect electroactive species close to the pore exit. A key aspect of IC-SECM is that in addition to the direct current (dc) from the diffusion-limited detection of the analyte, an alternating current (ac) also develops due to the motion of the probe. It demonstrates that this ac signal enhances the spatial resolution of SECM detection and allows the hydrodynamic flow of species to be detected from individual closely spaced pores. The experimental deductions are supported by three-dimensional finite element modeling which allows IC-SECM current maps to be analyzed to reveal transport rates through individual pores. The method described should be widely applicable to multiporous membrane transport.

  9. Electrochemical genosensor assay using lyophilized gold nanoparticles/latex microsphere label for detection of Vibrio cholerae.

    PubMed

    Liew, Pei Sheng; Lertanantawong, Benchaporn; Lee, Su Yin; Manickam, Ravichandran; Lee, Yook Heng; Surareungchai, Werasak

    2015-07-01

    Vibrio cholerae is a Gram-negative bacterium that causes cholera, a diarrheal disease. Cholera is widespread in poor, under-developed or disaster-hit countries that have poor water sanitation. Hence, a rapid detection method for V. cholerae in the field under these resource-limited settings is required. In this paper, we describe the development of an electrochemical genosensor assay using lyophilized gold nanoparticles/latex microsphere (AuNPs-PSA) reporter label. The reporter label mixture was prepared by lyophilization of AuNPs-PSA-avidin conjugate with different types of stabilizers. The best stabilizer was 5% sorbitol, which was able to preserve the dried conjugate for up to 30 days. Three methods of DNA hybridization were compared and the one-step sandwich hybridization method was chosen as it was fastest and highly specific. The performance of the assay using the lyophilized reagents was comparable to the wet form for detection of 1aM to 1fM of linear target DNA. The assay was highly specific for V. cholerae, with a detection limit of 1fM of PCR products. The ability of the sensor is to detect LAMP products as low as 50ngµl(-1). The novel lyophilized AuNPs-PSA-avidin reporter label with electrochemical genosensor detection could facilitate the rapid on-site detection of V. cholerae.

  10. Screen-printed carbon electrode-based electrochemical immunosensor for rapid detection of microalbuminuria.

    PubMed

    Tsai, Jang-Zern; Chen, Ching-Jung; Settu, Kalpana; Lin, Yu-Feng; Chen, Chien-Lung; Liu, Jen-Tsai

    2016-03-15

    A urinary microalbumin test is used to detect early signs of kidney damage in people who have a risk of chronic kidney disease, such as those with diabetes or hypertension. In this study, we developed a screen-printed carbon electrode-based immunosensor for the detection of microalbumin in urine. Anti-human albumin antibodies were immobilized on the screen-printed sensor surface by the covalent immobilization method. Cyclic voltammetry (CV) and scanning electron microscopy with an energy dispersive spectroscopical (SEM-EDS) analysis demonstrated that the modification process was well performed. Chronoamperometric (CA) electrochemical measurement technique was employed for the quantitative detection of albumin. The electrochemical measurements performed with some possible interfering compounds normally present in urine (ascorbic acid, uric acid, glucose and creatinine samples) demonstrated a high specificity and selectivity of this immunosensor in albumin detection. Under optimum conditions, the immunosensor can detect urinary albumin in a wide linear range from 10 µg/ml to 300 µg/ml with a detection limit of 9.7 µg/ml. The excellent performance of this immunosensor was confirmed by analyzing microalbumin in urine samples; the results were in good agreement with those obtained by the standard immunoturbidimetric method. The biosensor proposed herein is easy to prepare and can be used for low-cost, rapid, and sensitive screening of microalbuminuria. This approach provides a promising platform for developing clinical point-of-care diagnostic applications. PMID:26579935

  11. Magnetically trigged direct electrochemical detection of DNA hybridization using Au67 quantum dot as electrical tracer.

    PubMed

    Pumera, Martin; Castañeda, Maria Teresa; Pividori, Maria Isabel; Eritja, Ramon; Merkoçi, Arben; Alegret, Salvador

    2005-10-11

    A novel gold nanoparticle-based protocol for detection of DNA hybridization based on a magnetically trigged direct electrochemical detection of gold quantum dot tracers is described. It relies on binding target DNA (here called DNA1) with Au(67) quantum dot in a ratio 1:1, followed by a genomagnetic hybridization assay between Au(67)-DNA1 and complementary probe DNA (here called DNA2) marked paramagnetic beads. Differential pulse voltammetry is used for a direct voltammetric detection of resulting Au(67) quantum dot-DNA1/DNA2-paramagnetic bead conjugate on magnetic graphite-epoxy composite electrode. The characterization, optimization, and advantages of the direct electrochemical detection assay for target DNA are demonstrated. The two main highlights of presented assay are (1) the direct voltammetric detection of metal quantum dots obviates their chemical dissolution and (2) the Au(67) quantum dot-DNA1/DNA2-paramagnetic bead conjugate does not create the interconnected three-dimensional network of Au-DNA duplex-paramagnetic beads as previously developed nanoparticle DNA assays, pushing down the achievable detection limits.

  12. An enhanced Monte Carlo outlier detection method.

    PubMed

    Zhang, Liangxiao; Li, Peiwu; Mao, Jin; Ma, Fei; Ding, Xiaoxia; Zhang, Qi

    2015-09-30

    Outlier detection is crucial in building a highly predictive model. In this study, we proposed an enhanced Monte Carlo outlier detection method by establishing cross-prediction models based on determinate normal samples and analyzing the distribution of prediction errors individually for dubious samples. One simulated and three real datasets were used to illustrate and validate the performance of our method, and the results indicated that this method outperformed Monte Carlo outlier detection in outlier diagnosis. After these outliers were removed, the value of validation by Kovats retention indices and the root mean square error of prediction decreased from 3.195 to 1.655, and the average cross-validation prediction error decreased from 2.0341 to 1.2780. This method helps establish a good model by eliminating outliers. © 2015 Wiley Periodicals, Inc.

  13. Detecting insider activity using enhanced directory virtualization.

    SciTech Connect

    Shin, Dongwan; Claycomb, William R.

    2010-07-01

    Insider threats often target authentication and access control systems, which are frequently based on directory services. Detecting these threats is challenging, because malicious users with the technical ability to modify these structures often have sufficient knowledge and expertise to conceal unauthorized activity. The use of directory virtualization to monitor various systems across an enterprise can be a valuable tool for detecting insider activity. The addition of a policy engine to directory virtualization services enhances monitoring capabilities by allowing greater flexibility in analyzing changes for malicious intent. The resulting architecture is a system-based approach, where the relationships and dependencies between data sources and directory services are used to detect an insider threat, rather than simply relying on point solutions. This paper presents such an architecture in detail, including a description of implementation results.

  14. Detection and Identification of Hematologic Malignancies and Solid Tumors by an Electrochemical Technique

    PubMed Central

    Zhang, Bowen; Zhang, Xiaoping; Wang, Xuemei; Cheng, Jian; Chen, Baoan

    2016-01-01

    Purpose Develop and evaluate an electrochemical method to identify healthy individuals, malignant hematopathic patients and solid tumor patients by detecting the leukocytes in whole-blood. Methods A total of 114 individual blood samples obtained from our affiliated hospital in China (June 2015- August 2015) were divided into three groups: healthy individuals (n = 35), hematologic malignancies (n = 41) and solid tumors (n = 38). An electrochemical workstation system was used to measure differential pulse voltammetry due to the different electrochemical behaviors of leukocytes in blood samples. Then, one-way analysis of variance (ANOVA) was applied to analyze the scanning curves and to compare the peak potential and peak current. Results The scanning curve demonstrated the specific electrochemical behaviors of the blank potassium ferricyanide solution and that mixed with blood samples in different groups. Significant differences in mean peak potentials of mixture and shifts (ΔEp (mV)) were observed of the three groups (P< = 0.001). 106.00±9.00 and 3.14±7.48 for Group healthy individuals, 120.90±11.18 and 18.10±8.81 for Group hematologic malignancies, 136.84±11.53 and 32.89±10.50 for Group solid tumors, respectively. In contrast, there were no significant differences in the peak currents and shifts. Conclusions The newly developed method to apply the electrochemical workstation system to identify hematologic malignancies and solid tumors with good sensitivity and specificity might be effective, suggesting a potential utility in clinical application. PMID:27115355

  15. Overview of Electrochemical DNA Biosensors: New Approaches to Detect the Expression of Life

    PubMed Central

    Cagnin, Stefano; Caraballo, Marcelo; Guiducci, Carlotta; Martini, Paolo; Ross, Marty; SantaAna, Mark; Danley, David; West, Todd; Lanfranchi, Gerolamo

    2009-01-01

    DNA microarrays are an important tool with a variety of applications in gene expression studies, genotyping, pharmacogenomics, pathogen classification, drug discovery, sequencing and molecular diagnostics. They are having a strong impact in medical diagnostics for cancer, toxicology and infectious disease applications. A series of papers have been published describing DNA biochips as alternative to conventional microarray platforms to facilitate and ameliorate the signal readout. In this review, we will consider the different methods proposed for biochip construction, focusing on electrochemical detection of DNA. We also introduce a novel single-stranded DNA platform performing high-throughput SNP detection and gene expression profiling. PMID:22574066

  16. Nanomaterial based electrochemical sensors for in vitro detection of small molecule metabolites.

    PubMed

    Xiao, Fei; Wang, Lu; Duan, Hongwei

    2016-01-01

    Small molecule metabolites secreted by pathological processes can act as molecular biomarkers for clinical diagnosis. In vitro detection of the metabolites such as glucose and reactive oxygen species is of great significance for precise screening, monitoring and prognosis of metabolic disorders and relevant diseases such as cancer, and has been under intense research and development in clinical chemistry and molecular diagnostics. In this review, we summarize recent developments in nanomaterial based electrochemical (bio)sensors for in vitro detection of glucose and reactive oxygen species and the progress in utilizing lightweight and flexible electrodes and micro/nanoscale electrodes for flexible and miniaturized sensors.

  17. Detection of Nitroaromatic Explosives Using an Electrical- Electrochemical and Optical Hybrid Sensor

    NASA Astrophysics Data System (ADS)

    Diaz Aguilar, Alvaro

    In today's world there is a great need for sensing methods as tools to provide critical information to solve today's problems in security applications. Real time detection of trace chemicals, such as explosives, in a complex environment containing various interferents using a portable device that can be reliably deployed in a field has been a difficult challenge. A hybrid nanosensor based on the electrochemical reduction of trinitrotoluene (TNT) and the interaction of the reduction products with conducting polymer nanojunctions in an ionic liquid was fabricated. The sensor simultaneously measures the electrochemical current from the reduction of TNT and the conductance change of the polymer nanojunction caused from the reduction product. The hybrid detection mechanism, together with the unique selective preconcentration capability of the ionic liquid, provides a selective, fast, and sensitive detection of TNT. The sensor, in its current form, is capable of detecting parts per trillion level TNT in the presence of various interferents within a few minutes. A novel hybrid electrochemical-colorimetric (EC-C) sensing platform was also designed and fabricated to meet these challenges. The hybrid sensor is based on electrochemical reactions of trace explosives, colorimetric detection of the reaction products, and unique properties of the explosives in an ionic liquid (IL). This approach affords not only increased sensitivity but also selectivity as evident from the demonstrated null rate of false positives and low detection limits. Using an inexpensive webcam a detection limit of part per billion in volume (ppbV) has been achieved and demonstrated selective detection of explosives in the presence of common interferences (perfumes, mouth wash, cleaners, petroleum products, etc.). The works presented in this dissertation, were published in the Journal of the American Chemical Society (JACS, 2009) and Nano Letters (2010), won first place in the National Defense Research

  18. Electrochemical immunosensor for detection of topoisomerase based on graphene-gold nanocomposites.

    PubMed

    Zhong, Guang-Xian; Wang, Peng; Fu, Fei-Huan; Weng, Shao-Huang; Chen, Wei; Li, Shao-Guang; Liu, Ai-Lin; Wu, Zhao-Yang; Zhu, Xia; Lin, Xin-Hua; Lin, Jian-Hua; Xia, Xing-Hua

    2014-07-01

    A facile electrochemical immunosensor based on graphene-three dimensional nanostructure gold nanocomposites (G-3D Au) using simple and rapid one-step electrochemical co-reduction technique was developed for sensitive detection of topoisomerase. The resultant G-3D Au nanocomposites were characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy, and then were used as a substrate for construction of the "sandwich-type" immunosensor. Amperometric current-time curve was employed to monitor the immunoreaction on the protein modified electrode. The proposed method could respond to topoisomerase with a linear calibration range from 0.5 ng mL(-1) to 50 ng mL(-1) with a detection limit of 10 pg mL(-1). This new biosensor exhibited a fast amperometric response, high sensitivity and selectivity, and was successfully used in determining the topoisomerase which was added in human serum with a relative standard deviation (n=5)<5%. The immunosensor served as a significant step toward the practical application of the immunosensor in clinical diagnosis and prognosis monitor.

  19. Ag(I)-cysteamine complex based electrochemical stripping immunoassay: ultrasensitive human IgG detection.

    PubMed

    Noh, Hui-Bog; Rahman, Md Aminur; Yang, Jee Eun; Shim, Yoon-Bo

    2011-07-15

    An ultrasensitive electrochemical immunosensor for a protein using a Ag (I)-cysteamine complex (Ag-Cys) as a label was fabricated. The low detection of a protein was based on the electrochemical stripping of Ag from the adsorbed Ag-Cys complex on the gold nanoparticles (AuNPs) conjugated human immunoglobulin G (anti-IgG) antibody (AuNPs-anti-IgG). The electrochemical immunosensor was fabricated by immobilizing anti-IgG antibody on a poly-5,2':5',2''-terthiophene-3'-carboxylic acid (polyTTCA) film grown on the glassy carbon electrode through the covalent bond formation between amine groups of anti-IgG and carboxylic acid groups of polyTTCA. The target protein, IgG was sandwiched between the anti-IgG antibody that covalently attached onto the polyTTCA layer and AuNPs-anti-IgG. Using square wave voltammetry, well defined Ag stripping voltammograms were obtained for the each target concentration. Various experimental parameters were optimized and interference effects from other proteins were checked out. The immunosensor exhibited a wide dynamic range with the detection limit of 0.4 ± 0.05 fg/mL. To evaluate the analytical reliability, the proposed immunosensor was applied to human IgG spiked serum samples and acceptable results were obtained indicating that the method can be readily extended to other bioaffinity assays of clinical or environmental significance.

  20. Direct electrochemical sensor for label-free DNA detection based on zero current potentiometry.

    PubMed

    Wu, Nai-ying; Gao, Wei; He, Xu-lun; Chang, Zhu; Xu, Mao-tian

    2013-01-15

    A direct electrochemical DNA biosensor based on zero current potentiometry was fabricated by immobilization of ssDNA onto gold nanoparticles (AuNPs) coated pencil graphite electrode (PGE). One ssDNA/AuNPs/PGE was connected in series between clips of working and counter electrodes of a potentiostat, and then immersed into the solution together with a reference electrode, establishing a novel DNA biosensor for specific DNA detection. The variation of zero current potential difference (ΔE(zcp)) before and after hybridization of the self-assembled probe DNA with the target DNA was used as a signal to characterize and quantify the target DNA sequence. The whole DNA biosensor fabrication process was characterized by cyclic voltammetry and electrochemical impedance spectroscopy with the use of ferricyanide as an electrochemical redox indicator. Under the optimized conditions, ΔE(zcp) was linear with the concentrations of the complementary target DNA in the range from 10nM to 1μM, with a detection limit of 6.9nM. The DNA biosensor showed a good reproducibility and selectivity. Prepared DNA biosensor is facile and sensitive, and it eliminates the need of using exogenous reagents to monitor the oligonucleotides hybridization.

  1. Aptamer-based detection of plasma proteins by an electrochemical assay coupled to magnetic beads.

    PubMed

    Centi, Sonia; Tombelli, Sara; Minunni, Maria; Mascini, Marco

    2007-02-15

    The DNA thrombin aptamer has been extensively investigated, and the coupling of this aptamer to different transduction principles has demonstrated the wide applicability of aptamers as bioreceptors in bioanalytical assays. The goal of this work was to design an aptamer-based sandwich assay with electrochemical detection for thrombin analysis in complex matrixes, using a simple target capturing step by aptamer-functionalized magnetic beads. The conditions for the aptamer immobilization and for the protein binding have been first optimized by surface plasmon resonance, and then transferred to the electrochemical-based assay performed onto screen-printed electrodes. The assay was then applied to the analysis of thrombin in buffer, spiked serum, and plasma and high sensitivity and specificity were found. Moreover, thrombin was generated in situ in plasma by the conversion of its precursor prothrombin, and the formation of thrombin was followed at different times. The concentrations detected by the electrochemical assay were in agreement with a simulation software that mimics the formation of thrombin over time (thrombogram). The proposed work demonstrates that the high specificity of aptamers together with the use of magnetic beads are the key features for aptamer-based analysis in complex matrixes, opening the possibility of a real application to diagnostics or medical investigation.

  2. A regenerating ultrasensitive electrochemical impedance immunosensor for the detection of adenovirus.

    PubMed

    Lin, Donghai; Tang, Thompson; Harrison, D Jed; Lee, William E; Jemere, Abebaw B

    2015-06-15

    We report on the development of a regenerable sensitive immunosensor based on electrochemical impedance spectroscopy for the detection of type 5 adenovirus. The multi-layered immunosensor fabrication involved successive modification steps on gold electrodes: (i) modification with self-assembled layer of 1,6-hexanedithiol to which gold nanoparticles were attached via the distal thiol groups, (ii) formation of self-assembled monolayer of 11-mercaptoundecanoic acid onto the gold nanoparticles, (iii) covalent immobilization of monoclonal anti-adenovirus 5 antibody, with EDC/NHS coupling reaction on the nanoparticles, completing the immunosensor. The immunosensor displayed a very good detection limit of 30 virus particles/ml and a wide linear dynamic range of 10(5). An electrochemical reductive desorption technique was employed to completely desorb the components of the immunosensor surface, then re-assemble the sensing layer and reuse the sensor. On a single electrode, the multi-layered immunosensor could be assembled and disassembled at least 30 times with 87% of the original signal intact. The changes of electrode behavior after each assembly and desorption processes were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy techniques. PMID:25562739

  3. Kinetically Enhanced Electrochemical Redox of Polysulfides on Polymeric Carbon Nitrides for Improved Lithium-Sulfur Batteries.

    PubMed

    Liang, Ji; Yin, Lichang; Tang, Xiaonan; Yang, Huicong; Yan, Wensheng; Song, Li; Cheng, Hui-Ming; Li, Feng

    2016-09-28

    The kinetics and stability of the redox of lithium polysulfides (LiPSs) fundamentally determine the overall performance of lithium-sulfur (Li-S) batteries. Inspired by theoretical predictions, we herein validated the existence of a strong electrostatic affinity between polymeric carbon nitride (p-C3N4) and LiPSs, that can not only stabilize the redox cycling of LiPSs, but also enhance their redox kinetics. As a result, utilization of p-C3N4 in a Li-S battery has brought much improved performance in the aspects of high capacity and low capacity fading over prolonged cycling. Especially upon the application of p-C3N4, the kinetic barrier of the LiPS redox reactions has been significantly reduced, which has thus resulted in a better rate performance. Further density functional theory simulations have revealed that the origin of such kinetic enhancement was from the distortion of molecular configurations of the LiPSs anchored on p-C3N4. Therefore, this proof-of-concept study opens up a promising avenue to improve the performance of Li-S batteries by accelerating their fundamental electrochemical redox processes, which also has the potential to be applied in other electrochemical energy storage/conversion systems. PMID:27598825

  4. Combining Electrochemical Sensors with Miniaturized Sample Preparation for Rapid Detection in Clinical Samples

    PubMed Central

    Bunyakul, Natinan; Baeumner, Antje J.

    2015-01-01

    Clinical analyses benefit world-wide from rapid and reliable diagnostics tests. New tests are sought with greatest demand not only for new analytes, but also to reduce costs, complexity and lengthy analysis times of current techniques. Among the myriad of possibilities available today to develop new test systems, amperometric biosensors are prominent players—best represented by the ubiquitous amperometric-based glucose sensors. Electrochemical approaches in general require little and often enough only simple hardware components, are rugged and yet provide low limits of detection. They thus offer many of the desirable attributes for point-of-care/point-of-need tests. This review focuses on investigating the important integration of sample preparation with (primarily electrochemical) biosensors. Sample clean up requirements, miniaturized sample preparation strategies, and their potential integration with sensors will be discussed, focusing on clinical sample analyses. PMID:25558994

  5. Combining electrochemical sensors with miniaturized sample preparation for rapid detection in clinical samples.

    PubMed

    Bunyakul, Natinan; Baeumner, Antje J

    2015-01-01

    Clinical analyses benefit world-wide from rapid and reliable diagnostics tests. New tests are sought with greatest demand not only for new analytes, but also to reduce costs, complexity and lengthy analysis times of current techniques. Among the myriad of possibilities available today to develop new test systems, amperometric biosensors are prominent players-best represented by the ubiquitous amperometric-based glucose sensors. Electrochemical approaches in general require little and often enough only simple hardware components, are rugged and yet provide low limits of detection. They thus offer many of the desirable attributes for point-of-care/point-of-need tests. This review focuses on investigating the important integration of sample preparation with (primarily electrochemical) biosensors. Sample clean up requirements, miniaturized sample preparation strategies, and their potential integration with sensors will be discussed, focusing on clinical sample analyses. PMID:25558994

  6. Method of detecting defects in ion exchange membranes of electrochemical cells by chemochromic sensors

    DOEpatents

    Brooker, Robert Paul; Mohajeri, Nahid

    2016-01-05

    A method of detecting defects in membranes such as ion exchange membranes of electrochemical cells. The electrochemical cell includes an assembly having an anode side and a cathode side with the ion exchange membrane in between. In a configuration step a chemochromic sensor is placed above the cathode and flow isolation hardware lateral to the ion exchange membrane which prevents a flow of hydrogen (H.sub.2) between the cathode and anode side. The anode side is exposed to a first reactant fluid including hydrogen. The chemochromic sensor is examined after the exposing for a color change. A color change evidences the ion exchange membrane has at least one defect that permits H.sub.2 transmission therethrough.

  7. Integration of serpentine channels for microchip electrophoresis with a palladium decoupler and electrochemical detection

    PubMed Central

    Bowen, Amanda L; Martin, R. Scott

    2010-01-01

    While it has been shown that microchip electrophoresis with electrochemical detection can be used to separate and detect electroactive species, there is a need to increase the separation performance of these devices so that complex mixtures can be routinely analyzed. Previous work in microchip electrophoresis has demonstrated that increasing the separation channel length leads to an increase in resolution between closely eluting analytes. This paper details the use of lengthened serpentine microchannels for microchip electrophoresis and electrochemical detection where a palladium decoupler is used to ground the separation voltage so that the working electrodes remain in the fluidic network. In this work, palladium electrodepositions were used to increase the decoupler surface area and more efficiently dissipate hydrogen produced at the decoupler. Dopamine and norepinephrine, which only differ in structure by a hydroxyl group, were used as model analytes. It was found that increasing the separation channel length led to improvements in both resolution and the number of theoretical plates for these analytes. The use of a bi-layer valving device, where PDMS-based valves are utilized for the injection process, along with serpentine microchannels and amperometric detection resulted in a multi-analyte separation and an average of 28,700 theoretical plates. It was also shown that the increased channel length is beneficial when separating and detecting analytes from a high ionic strength matrix. This was demonstrated by monitoring the stimulated release of neuro-transmitters from a confluent layer of PC 12 cells. PMID:19739137

  8. Integration of serpentine channels for microchip electrophoresis with a palladium decoupler and electrochemical detection.

    PubMed

    Bowen, Amanda L; Martin, R Scott

    2009-10-01

    Although it has been shown that microchip electrophoresis (MCE) with electrochemical detection can be used to separate and detect electroactive species, there is a need to increase the separation performance of these devices so that complex mixtures can be routinely analyzed. Previous work in the MCE has demonstrated that increasing the separation channel length leads to an increase in resolution between closely eluting analytes. This paper details the use of lengthened serpentine microchannels for MCE and electrochemical detection where a palladium decoupler is used to ground the separation voltage so that the working electrodes remain in the fluidic network. In this work, palladium electrodepositions were used to increase the decoupler surface area and more efficiently dissipate hydrogen produced at the decoupler. Dopamine and norepinephrine, which only differ in structure by a hydroxyl group, were used as model analytes. It was found that increasing the separation channel length led to improvements in both the resolution and the number of theoretical plates for these analytes. The use of a bilayer valving device, where PDMS-based valves are utilized for the injection process, along with serpentine microchannels and amperometric detection resulted in a multianalyte separation and an average of 28 700 theoretical plates. It was also shown that the increased channel length is beneficial when separating and detecting analytes from a high ionic strength matrix. This was demonstrated by monitoring the stimulated release of neurotransmitters from a confluent layer of PC 12 cells.

  9. High sensitivity and label-free detection of Enterovirus 71 by nanogold modified electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Fang-Yu; Li, Hsing-Yuan; Tseng, Shing-Hua; Cheng, Tsai-Mu; Chu, Hsueh-Liang; Yang, Jyh-Yuan; Chang, Chia-Ching

    2013-03-01

    Enterovirus 71 (EV71), which is the most fulminant and invasive species of enterovirus, can cause children neurologic complications and death within 2-3 days after fever and rash developed. Besides, EV71 has high sequence similarity with Coxsackie A 16 (CA16) that makes differential diagnosis difficult in clinic and laboratory. Since conventional viral diagnostic method cannot diagnose EV71 quickly and EV71 can transmit at low viral titer, the patients might delay in treatment. A quick, high sensitive, and high specific test for EV71 detection is pivotal. Electrochemical impedance spectroscopy (EIS) has been applied for detecting bio-molecules as biosensors recently. In this study, we try to build a detection platform for EV71 detection by nanogold modified EIS probe. The result shows that our probe can detect 3.6 VP1/50 μl (one EV71 particle has 60 VP1) in 3 minutes. The test can also distinguish EV71 from CA16 and lysozyme. Diagnosis of enterovirus 71 by electrochemical impedance spectroscopy has the potential to apply in clinic.

  10. Electrochemical detection of Pseudomonas aeruginosa in human fluid samples via pyocyanin.

    PubMed

    Webster, Thaddaeus A; Sismaet, Hunter J; Conte, Jared L; Chan, I-ping J; Goluch, Edgar D

    2014-10-15

    The ability to quickly detect the presence of pathogenic bacteria in patient samples is of the outmost importance to expedient patient care. Here we report the direct, selective, and sensitive detection of the opportunistic pathogen Pseudomonas aeruginosa, spiked in human whole blood with sodium heparin, urine, sputum, and bronchial lavage samples using unmodified, disposable carbon electrode sensors that detect the presence of pyocyanin, a virulence factor that is unique to this species. Square wave voltammetry scans of biological fluids from healthy individuals spiked with P. aeruginosa showed a clear pyocyanin response within one day of culturing at 37°C. Scans of supernatants taken from cultures of P. aeruginosa, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermis, and Bacillus cereus taken over a span of three days in the potential range from -0.5 to 0 V vs. an Ag/AgCl reference showed no electrochemically detectable molecules with the exception of P. aeruginosa. The results indicate the potential to sensitively and selectively determine the presence of P. aeruginosa in human samples via the electrochemical detection of pyocyanin in less than 5 min, without any sample preparation or separation steps. PMID:24813917

  11. Magnetic Electrochemical Immunoassays with Quantum Dot Labels for Detection of Phosphorylated Acetylcholinesterase in Plasma

    SciTech Connect

    Wang, Hua; Wang, Jun; Timchalk, Charles; Lin, Yuehe

    2008-11-01

    A new magnetic electrochemical immunoassay has been developed as a tool for biomonitoring exposures to organophosphate (OP) compounds, e.g., insecticides and chemical nerve agents, by directly detecting organophosphorylated acetylcholinesterase (OP-AChE). This immunoassay uniquely incorporates highly efficient magnetic separation with ultrasensitive square wave voltammetry (SWV) analysis with quantum dots (QDs) as labels. A pair of antibodies was used to achieve the specific recognition of OP-AChE that was prepared with paraoxon as an OP model agent. Antiphosphoserine polyclonal antibodies were anchored on amorphous magnetic particles preferably chosen to capture OP-AChE from the sample matrixes by binding their phosphoserine moieties that were exposed through unfolding the protein adducts. This was validated by electrochemical examinations and enzyme-linked immunosorbent assays. Furthermore, antihuman AChE monoclonal antibodies were labeled with cadmium-source QDs to selectively recognize the captured OP-AChE, as characterized by transmission electron microscopy. The subsequent electrochemical SWV analysis of the cadmium component released by acid from the coupled QDs was conducted on disposable screen-printed electrodes. Experimental results indicated that the SWV-based immunoassays could yield a linear response over a broad concentration range of 0.3-300 ng/mL OP-AChE in human plasma with a detection limit of 0.15 ng/mL. Such a novel electrochemical immunoassay holds great promise as a simple, selective, sensitive, and field-deployable tool for the effective biomonitoring and diagnosis of potential exposures to nerve agents and pesticides.

  12. Enhanced detection with bimodal sonar displays.

    PubMed

    Doll, T J; Hanna, T E

    1989-10-01

    Signal-to-noise ratios (SNRs) required to detect narrow-band signals in white noise were compared for bimodal and single-modality sonar displays at two levels of signal uncertainty and two degrees of spatial compatibility between the auditory and visual displays. In bimodal test conditions the auditory and visual signals were equated in detectability for each subject. An adaptive, two-alternative, forced-choice procedure was used to maintain a constant percentage of correct responses. The decrement in performance with increased signal uncertainty was significantly greater for visual than for auditory displays, suggesting that auditory displays offer advantages for real-world sonar operations. Bimodal displays produced a reliable advantage in SNR required for detection over single-modality displays. Increased compatibility between the visual and auditory displays did not increase the advantage of bimodal presentation, nor did increased signal uncertainty. It was concluded that bimodal displays enhance operators' perceptual sensitivity. The magnitude of the enhancement was consistent with optimal integration of information in the two modalities.

  13. Exploring students' understanding of electrochemical cells using an enhanced two-tier diagnostic instrument

    NASA Astrophysics Data System (ADS)

    Sin Loy Loh, Adrian; Subramaniam, R.; Tan, Kim Chwee Daniel

    2014-09-01

    Background:The development of two-tier multiple-choice questions has permitted the diagnosis of students' understanding on various topics in the sciences as well as helped to ascertain the alternative conceptions they have. A limitation of two-tier diagnostic instruments that has been noted in the literature, but which has not been systematically explored, is that some questions can have a diagonal response. This can allow students to select a second-tier response based on cues from a particular response in the first tier, and it can limit the analytical utility of the diagnostic instrument to some extent. Purpose:The study explores an enhancement of the traditional two-tier diagnostic instrument to address diagonal response. In the format proposed, there are dual sections for both the answer and reason tiers. The answer tier is in dichotomous form and for each of the dichotomous responses, there are separate polytomous responses in the reason tier. Sample:There were 99 students of grade 10 level who participated in this study. Design and Method:The research design follows the usual approach adopted for the development of diagnostic instruments but with some modifications. The topic of electrochemical cells was chosen to evaluate the effectiveness of the enhanced format of the two-tier instrument. Results:It was found that with the enhanced format, the issue of diagonal response has been satisfactorily addressed. Also, a situation where students get the answer wrong but the reason correct, which is sometimes encountered in two-tier questions, does not arise with this format. The instrument has also been able to shed some light on the students' understanding of electrochemical cells and their alternative conceptions. Conclusions:The enhanced format of the two-tier instrument proposed in this study can also be used for the study of alternative conceptions in science education.

  14. Aggregation of Individual Sensing Units for Signal Accumulation: Conversion of Liquid-Phase Colorimetric Assay into Enhanced Surface-Tethered Electrochemical Analysis.

    PubMed

    Wei, Tianxiang; Dong, Tingting; Wang, Zhaoyin; Bao, Jianchun; Tu, Wenwen; Dai, Zhihui

    2015-07-22

    A novel concept is proposed for converting liquid-phase colorimetric assay into enhanced surface-tethered electrochemical analysis, which is based on the analyte-induced formation of a network architecture of metal nanoparticles (MNs). In a proof-of-concept trial, thymine-functionalized silver nanoparticle (Ag-T) is designed as the sensing unit for Hg(2+) determination. Through a specific T-Hg(2+)-T coordination, the validation system based on functionalized sensing units not only can perform well in a colorimetric Hg(2+) assay, but also can be developed into a more sensitive and stable electrochemical Hg(2+) sensor. In electrochemical analysis, the simple principle of analyte-induced aggregation of MNs can be used as a dual signal amplification strategy for significantly improving the detection sensitivity. More importantly, those numerous and diverse colorimetric assays that rely on the target-induced aggregation of MNs can be augmented to satisfy the ambitious demands of sensitive analysis by converting them into electrochemical assays via this approach. PMID:26149108

  15. Electrochemical behavior of N-methyl-N'-carboxydecyl-4,4'-bipyridinium probed by surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Xu, Jian-Fang; Liu, Guo-Kun

    2013-10-01

    Interfacial structure determines the activity and selectivity of a sensor and plays important roles in interfacial electrochemistry, electroanalysis, biosensing, etc. In situ electrochemical Raman spectroscopy appears to be a powerful tool to probe the electrochemical interface and surface process by providing the molecular fingerprint information. Herein, the electrochemical behaviors of N-methyl-N'-carboxydecyl-4,4'-bipyridinium (derivatives of methyl viologens, MV2+) with different alkyl chain lengths (n = 2 and 10) on roughened Au electrodes were systematically investigated by the electrochemical surface-enhanced Raman spectroscopy (SERS). Three systems with different interfacial structures were constructed. One is to anchor the MV2+ molecules via esterification with the 2-mercaptoethanol molecule pre-assembled on the Au surface. The second system is similar to the first one but without esterification. The third system is the direct adsorption of MV2+ molecules on the bare roughened Au surfaces. The three systems gave different spectral response upon the change of the electrode potential. A drastically increased relative Raman intensity of 19a/8a modes of the MV2+ molecules was observed at negative potentials. The phenomenon is attributed to the formation of the reduced form of MV2+ molecules, which produces resonant Raman effect to enhanced the signal of 19a mode. The third system showed the highest electrochemical reduction activity towards the reduction of MV2+ molecules, followed by the first and second systems. The result indicates that the interfacial structure can sensitively influence electrochemical activity of the electrode.

  16. Nanostructured rough gold electrodes as platforms to enhance the sensitivity of electrochemical genosensors.

    PubMed

    García-Mendiola, T; Gamero, M; Campuzano, S; Revenga-Parra, M; Alonso, C; Pedrero, M; Pariente, F; Pingarrón, J M; Lorenzo, E

    2013-07-25

    An electrochemical DNA genosensor constructed by using rough gold as electrode support is reported in this work. The electrode surface nanopatterning was accomplished by repetitive square-wave perturbing potential (RSWPP). A synthetic 25-mer DNA capture probe, modified at the 5' end with a hexaalkylthiol, able to hybridize with a specific sequence of lacZ gene from the Enterobacteriaceae bacterial family was assembled to the rough gold surface. A 25 bases synthetic sequence fully complementary to the thiolated DNA capture probe and a 326 bases fragment of lacZ containing a fully matched sequence with the capture probe, which was amplified by a specific asymmetric polymerase chain reaction (aPCR), were employed as target sequences. The hybridization event was electrochemically monitored by using two different indicators, hexaammineruthenium (III) chloride showing an electrostatic DNA binding mode, and pentaamineruthenium-[3-(2-phenanthren-9-yl-vinyl)-pyridine] (in brief RuL) which binds to double stranded DNA (dsDNA) following an intercalative mechanism. After optimization of the different variables involved in the hybridization and detection reactions, detection limits of 5.30 pg μL(-1) and 10 pg μL(-1) were obtained for the 25-mer synthetic target DNA and the aPCR amplicon, respectively. A RSD value of 6% was obtained for measurements carried out with 3 different genosensors prepared in the same manner. PMID:23845493

  17. A bacteriophage endolysin-based electrochemical impedance biosensor for the rapid detection of Listeria cells.

    PubMed

    Tolba, Mona; Ahmed, Minhaz Uddin; Tlili, Chaker; Eichenseher, Fritz; Loessner, Martin J; Zourob, Mohammed

    2012-12-21

    The objective of this study was to develop a biosensor using the cell wall binding domain (CBD) of bacteriophage-encoded peptidoglycan hydrolases (endolysin) immobilized on a gold screen printed electrode (SPE) and subsequent electrochemical impedance spectroscopy (EIS) for a rapid and specific detection of Listeria cells. The endolysin was amine-coupled to SPEs using EDC/NHS chemistry. The CBD-based electrode was used to capture and detect the Listeria innocua serovar 6b from pure culture and 2% artificially contaminated milk. In our study, the endolysin functionalized SPEs have been characterized using X-ray photoelectron spectroscopy (XPS). The integration of endolysin-based recognition for specific bacteria and EIS can be used for direct and rapid detection of Listeria cells with high specificity against non-Listeria cells with a limit of detection of 1.1 × 10(4) and 10(5) CFU mL(-1) in pure culture and 2% milk, respectively.

  18. Electrochemical Assay for the Signal-on Detection of Human DNA Methyltransferase Activity

    PubMed Central

    Muren, Natalie B.; Barton, Jacqueline K.

    2013-01-01

    Strategies to detect human DNA methyltransferases are needed, given that aberrant methylation by these enzymes is associated with cancer initiation and progression. Here we describe a non-radioactive, antibody-free, electrochemical assay in which methyltransferase activity on DNA-modified electrodes confers protection from restriction for signal-on detection. We implement this assay with a multiplexed chip platform and show robust detection of both bacterial (SssI) and human (Dnmt1) methyltransferase activity. Essential to work with human methyltransferases, our unique assay design allows activity measurements on both unmethylated and hemimethylated DNA substrates. We validate this assay by comparison with a conventional radioactive method. The advantages of electrochemistry over radioactivity and fluorescence make this assay an accessible and promising new approach for the sensitive, label-free detection of human methyltransferase activity. PMID:24164112

  19. Novel integrated and portable endotoxin detection system based on an electrochemical biosensor.

    PubMed

    Zuzuarregui, Ana; Souto, David; Pérez-Lorenzo, Eva; Arizti, Fernando; Sánchez-Gómez, Susana; Martínez de Tejada, Guillermo; Brandenburg, Klaus; Arana, Sergio; Mujika, Maite

    2015-01-21

    This paper describes the design, implementation and validation of a sensitive and integral technology solution for endotoxin detection. The unified and portable platform is based on the electrochemical detection of endotoxins using a synthetic peptide immobilized on a thin-film biosensor. The work covers the fabrication of an optimized sensor, the biofunctionalization protocol and the design and implementation of the measuring and signalling elements (a microfluidic chamber and a portable potentiostat-galvanostat), framed ad hoc for this specific application. The use of thin-film technologies to fabricate the biosensing device and the application of simple immobilization and detection methods enable a rapid, easy and sensitive technique for in situ and real time LPS detection. PMID:25431806

  20. Aptamer-conjugated silver nanoparticles for electrochemical dual-aptamer-based sandwich detection of staphylococcus aureus.

    PubMed

    Abbaspour, Abdolkarim; Norouz-Sarvestani, Fatemeh; Noori, Abolhassan; Soltani, Noushin

    2015-06-15

    Staphylococcus aureus (S. aureus) is one of the most important human pathogens and causes numerous illnesses. In this study, we report a sensitive and highly selective dual-aptamer-based sandwich immunosensor for the detection of S. aureus. In this bioassay system, a biotinylated primary anti-S.aureus aptamer was immobilized on streptavidin coated magnetic beads (MB), which serves as a capture probe. A secondary anti-S.aureus aptamer was conjugated to silver nanoparticles (Apt-AgNP) that sensitively reports the detection of the target. In the presence of target bacterium, an Apt/S.aureus/apt-AgNP sandwich complex is formed on the MB surface and the electrochemical signal of AgNPs followed through anodic stripping voltammetry. The proposed sandwich assay benefits from advantageous of a sandwich assay for increased specificity, MB as carriers of affinity ligands for solution-phase recognition and fast magnetic separation, AgNPs for signal amplification, and an electrochemical stripping voltammetry read-out as a simple and sensitive detection. The electrochemical immunosensor shows an extended dynamic range from 10 to 1×10(6) cfu/mL with a low detection limit of 1.0 cfu/mL (S/N=3). Furthermore, the possible interference of other analog bacteria was studied. To assess the general applicability of this sensor, we investigated the quantification of S. aureus in real water samples. The results were compared to the experimental results obtained from a plate counting method, which demonstrated an acceptable consistency.

  1. Label-free signal-on aptasensor for sensitive electrochemical detection of arsenite.

    PubMed

    Cui, Lin; Wu, Jie; Ju, Huangxian

    2016-05-15

    A signal-on aptasensor was fabricated for highly sensitive and selective electrochemical detection of arsenite with a label-free Ars-3 aptamer self-assembled on a screen-printed carbon electrode (SPCE) via Au-S bond. The Ars-3 aptamer could adsorb cationic polydiallyldimethylammonium (PDDA) via electrostatic interaction to repel other cationic species. In the presence of arsenite, the change of Ars-3 conformation due to the formation of Ars-3/arsenite complex led to less adsorption of PDDA, and the complex could adsorb more positively charged [Ru(NH3)6](3+) as an electrochemically active indicator on the aptasensor surface, which produced a sensitive "turn-on" response. The target-induced structure switching could be used for sensitive detection of arsenite with a linear range from 0.2 nM to 100 nM and a detection limit down to 0.15 nM. Benefiting from Ars-3 aptamer, the proposed system exhibited excellent specificity against other heavy metal ions. The SPCE-based aptasensor exhibited the advantages of low cost and simple fabrication, providing potential application of arsenite detection in environment.

  2. A hairpin aptamer-based electrochemical biosensing platform for the sensitive detection of proteins.

    PubMed

    Wu, Zai-Sheng; Zheng, Fan; Shen, Guo-Li; Yu, Ru-Qin

    2009-05-01

    An aptamer-based electrochemical sensing platform for the direct protein detection has been developed using IgE and a specifically designed aptamer with hairpin structure as the model analyte and probe sequence, respectively. In the absence of IgE, the aptamer immobilized on an electrode surface forms a large hairpin due to the hybridization of the two complementary arm sequences, and peak currents of redox species dissolved in solution can be achieved. However, the target protein binding can not only cause the increase of the dielectric layer but also trigger the significant conformational switching of the aptamer due to the opening of the designed hairpin structure that pushes the biomolecule layer/electrolyte interface away from the electrode surface, suppressing substantially the electron transfer (eT) and resulting in a strong detection signal. The detection limit of 3.6x10(-11)M and linear response range of 5.4x10(-11) to 3.6x10(-8)M are achieved without any amplifier. The selectivity is confirmed by interference test. More importantly, an innovative concept of adapting intelligently a surface-confined aptamer sequence is introduced, and the limitations of the conventional electrochemical aptasensors have been overcome. The proposed sensing scheme is expected to become a promising strategy for the detection of proteins and other biomacromolecules.

  3. Single strand DNA functionalized single wall carbon nanotubes as sensitive electrochemical labels for arsenite detection.

    PubMed

    Wang, Yonghong; Wang, Ping; Wang, Yiqiang; He, Xiaoxiao; Wang, Kemin

    2015-08-15

    In this work, a simple and sensitive electrochemical strategy for arsenite detection based on the ability of arsenite bound to single-strand DNA (ssDNA) and the signal transduction of single wall carbon nanotubes (SWCNTs) is developed. To realize this purpose, the ssDNA/SWCNTs complexes were formed at first by making ssDNA wrapped around SWCNTs via π-stacking. In the presence of arsenite, the arsenite could strongly bind with the G/T bases of ssDNA and decrease the π-π interaction between ssDNA and SWCNTs, resulting in a certain amount of ssDNA dissociating from the complexes. The separated SWCNTs were selectively assembled on the self-assembled monolayer (SAM) modified Au electrode. Then the SWCNTs onto the SAM-modified Au electrode substantially restored heterogeneous electron transfer that was almost totally blocked by the SAM. The assembled SWCNTs could generate a considerably sensitive and specific tactic for signal transduction, which was related to the concentration of the arsenite. Through detecting the currents mediated by SWCNTs, a linear response to concentration of arsenite ranging from 0.5 to 10ppb and a detection limit of 0.5ppb was readily achieved with desirable specificity and sensitivity. Such a SWCNTs-based biosensor creates a simple, sensitive, nonradioactive route for detection of arsenite. In addition, this demonstration provides a new approach to fabrication of stable biosensors with favorable electrochemical properties believed to be appealing to electroanalytical applications.

  4. Electrochemical detection of methyl nicotinate biomarker using functionalized anodized titania nanotube arrays

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Dhiman; Smith, York R.; Misra, Mano; Mohanty, Swomitra K.

    2015-02-01

    Sensing and detection of volatile organic compounds (VOCs) from exhaled breath is a possible method for early diagnosis of several pulmonary diseases. The use of solid-state TiO2 nanotube array sensors for VOC sensing applications has been of great interest. In this study, titania nanotubular arrays (TNAs) were synthesized through electrochemical anodization and used for the electrochemical detection of methyl nicotinate biomarker vapor. Functionalization of the TNA with cobalt was found to be necessary for methyl nicotinate detection. Titanium dioxide films synthesized through high temperature oxidation and functionalized with cobalt were also compared with cobalt functionalized TNA. The ordered TNA demonstrated itself to be an effective substrate for cobalt deposition and subsequent biomarker detection over thin titanium dioxide films. Surface analysis of the cobalt functionalized TNA by x-ray photoelectron spectroscopy (XPS) studies observed cobalt deposits exist as cobalt hydroxide on the surface. Exposure of the sensor surface to methyl nicotinate vapor results in the reduction of cobalt hydroxide to cobalt metal on the surface. Two mechanisms have been proposed to describe the binding of the nicotinate biomarker to cobalt functionalized TNA consistent with the XPS studies and band theory.

  5. Ratiometric electrochemical proximity assay for sensitive one-step protein detection

    NASA Astrophysics Data System (ADS)

    Ren, Kewei; Wu, Jie; Yan, Feng; Ju, Huangxian

    2014-03-01

    This work proposes the concept of ratiometric electrochemical proximity assay (REPA), which can be used for one-step, highly sensitive and selective detection of protein. The assay strategy was achieved on a sensing interface that was formed by hybridization of methylene blue (MB)-labeled antibody-DNA probe (MB-DNA1-Ab1) with ferrocene (Fc)-labeled DNA capture probe (Fc-P) modified gold electrode. On the interface the target protein could trigger the formation of immunocomplex between MB-DNA1-Ab1 and detection antibody-DNA probe (Ab2-DNA2) and subsequently the proximity hybridization of DNA1-DNA2, which led to the departure of MB-DNA1-Ab1 from the interface. The remained Fc-P could form a hairpin structure to take Fc group to electrode surface. Therefore, the recognition of target protein to Ab1 and Ab2 resulted in both the ``signal-off'' of MB and the ``signal-on'' of Fc for dual-signal electrochemical ratiometric readout. The proposed REPA could be carried out in one-step with 40-min duration and showed a wide detection range from 0.05 to 100 ng/mL with pg/mL limit of detection, displaying great potential for convenient point-of-care testing and commercial application.

  6. Electrochemical DNA sensor-based strategy for sensitive detection of DNA demethylation and DNA demethylase activity.

    PubMed

    Shen, Qingming; Fan, Mengxing; Yang, Yin; Zhang, Hui

    2016-08-31

    DNA demethylation and demethylase activity play important roles in DNA self-repair, and their detection is key to early diagnosis of fatal diseases. Herein, a facile electrochemical DNA (E-DNA) sensor was developed for the sensitive detection of DNA demethylation and demethylase activity based on an enzyme cleavage strategy. The thiol modified hemi-methylated hairpin probe DNA (pDNA) was self-assembled on a Au electrode surface through the formation of AuS bonds. The hemi-methylated pDNA served as the substrate of DNA demethylase (using methyl-CpG-binding domain protein 2 (MBD2) as an example). Following demethylation, the hairpin stem was then recognized and cleaved by BstUI endonuclease. The ferrocene carboxylic acid (FcA)-tagged pDNA strands were released into the buffer solution from the electrode surface, resulting in a significant decrease of electrochemical signal and providing a means to observe DNA demethylation. The activity of DNA demethylase was analyzed in the concentration ranging from 0.5 to 500 ng mL(-1) with a limit of detection as low as 0.17 ng mL(-1). With high specificity and sensitivity, rapid response, and low cost, this simple E-DNA sensor provides a unique platform for the sensitive detection of DNA demethylation, DNA demethylase activity, and related molecular diagnostics and drug screening. PMID:27506345

  7. Label-free signal-on aptasensor for sensitive electrochemical detection of arsenite.

    PubMed

    Cui, Lin; Wu, Jie; Ju, Huangxian

    2016-05-15

    A signal-on aptasensor was fabricated for highly sensitive and selective electrochemical detection of arsenite with a label-free Ars-3 aptamer self-assembled on a screen-printed carbon electrode (SPCE) via Au-S bond. The Ars-3 aptamer could adsorb cationic polydiallyldimethylammonium (PDDA) via electrostatic interaction to repel other cationic species. In the presence of arsenite, the change of Ars-3 conformation due to the formation of Ars-3/arsenite complex led to less adsorption of PDDA, and the complex could adsorb more positively charged [Ru(NH3)6](3+) as an electrochemically active indicator on the aptasensor surface, which produced a sensitive "turn-on" response. The target-induced structure switching could be used for sensitive detection of arsenite with a linear range from 0.2 nM to 100 nM and a detection limit down to 0.15 nM. Benefiting from Ars-3 aptamer, the proposed system exhibited excellent specificity against other heavy metal ions. The SPCE-based aptasensor exhibited the advantages of low cost and simple fabrication, providing potential application of arsenite detection in environment. PMID:26785310

  8. A signal-on electrochemical aptasensor for ultrasensitive detection of endotoxin using three-way DNA junction-aided enzymatic recycling and graphene nanohybrid for amplification.

    PubMed

    Bai, Lijuan; Chai, Yaqin; Pu, Xiaoyun; Yuan, Ruo

    2014-03-01

    Endotoxin, also known as lipopolysaccharide (LPS), is able to induce a strong immune response on its internalization into mammalian cells. To date, aptamer-based biosensors for LPS detection have been rarely reported. This work describes a new signal-on electrochemical aptasensor for the ultrasensitive detection of LPS by combining the three-way DNA hybridization process and nanotechnology-based amplification. With the help of DNA1 (associated with the concentration of target LPS), the capture probe hybridizes with DNA1 and the assistant probe to open its hairpin structure and form a ternary "Y" junction structure. The DNA1 can be released from the structure in the presence of nicking endonuclease to initiate the next hybridization process. Then a great deal of cleaved capture probe produced in the cyclic process can bind with DNA2-nanocomposite, which contains the electroactive toluidine blue (Tb) with the amplification materials graphene (Gra) and gold nanoparticles (AuNPs). Thus, an enhanced electrochemical signal can be easily read out. With the cascade signal amplification, this newly designed protocol provides an ultrasensitive electrochemical detection of LPS down to the femtogram level (8.7 fg mL(-1)) with a linear range of 6 orders of magnitude (from 10 fg mL(-1) to 50 ng mL(-1)). Moreover, the high sensitivity and specificity make this method versatile for the detection of other biomolecules by changing the corresponding sequences of the capture probe and the assistant probe.

  9. A signal-on electrochemical aptasensor for ultrasensitive detection of endotoxin using three-way DNA junction-aided enzymatic recycling and graphene nanohybrid for amplification

    NASA Astrophysics Data System (ADS)

    Bai, Lijuan; Chai, Yaqin; Pu, Xiaoyun; Yuan, Ruo

    2014-02-01

    Endotoxin, also known as lipopolysaccharide (LPS), is able to induce a strong immune response on its internalization into mammalian cells. To date, aptamer-based biosensors for LPS detection have been rarely reported. This work describes a new signal-on electrochemical aptasensor for the ultrasensitive detection of LPS by combining the three-way DNA hybridization process and nanotechnology-based amplification. With the help of DNA1 (associated with the concentration of target LPS), the capture probe hybridizes with DNA1 and the assistant probe to open its hairpin structure and form a ternary ``Y'' junction structure. The DNA1 can be released from the structure in the presence of nicking endonuclease to initiate the next hybridization process. Then a great deal of cleaved capture probe produced in the cyclic process can bind with DNA2-nanocomposite, which contains the electroactive toluidine blue (Tb) with the amplification materials graphene (Gra) and gold nanoparticles (AuNPs). Thus, an enhanced electrochemical signal can be easily read out. With the cascade signal amplification, this newly designed protocol provides an ultrasensitive electrochemical detection of LPS down to the femtogram level (8.7 fg mL-1) with a linear range of 6 orders of magnitude (from 10 fg mL-1 to 50 ng mL-1). Moreover, the high sensitivity and specificity make this method versatile for the detection of other biomolecules by changing the corresponding sequences of the capture probe and the assistant probe.

  10. A signal-on electrochemical aptasensor for ultrasensitive detection of endotoxin using three-way DNA junction-aided enzymatic recycling and graphene nanohybrid for amplification.

    PubMed

    Bai, Lijuan; Chai, Yaqin; Pu, Xiaoyun; Yuan, Ruo

    2014-03-01

    Endotoxin, also known as lipopolysaccharide (LPS), is able to induce a strong immune response on its internalization into mammalian cells. To date, aptamer-based biosensors for LPS detection have been rarely reported. This work describes a new signal-on electrochemical aptasensor for the ultrasensitive detection of LPS by combining the three-way DNA hybridization process and nanotechnology-based amplification. With the help of DNA1 (associated with the concentration of target LPS), the capture probe hybridizes with DNA1 and the assistant probe to open its hairpin structure and form a ternary "Y" junction structure. The DNA1 can be released from the structure in the presence of nicking endonuclease to initiate the next hybridization process. Then a great deal of cleaved capture probe produced in the cyclic process can bind with DNA2-nanocomposite, which contains the electroactive toluidine blue (Tb) with the amplification materials graphene (Gra) and gold nanoparticles (AuNPs). Thus, an enhanced electrochemical signal can be easily read out. With the cascade signal amplification, this newly designed protocol provides an ultrasensitive electrochemical detection of LPS down to the femtogram level (8.7 fg mL(-1)) with a linear range of 6 orders of magnitude (from 10 fg mL(-1) to 50 ng mL(-1)). Moreover, the high sensitivity and specificity make this method versatile for the detection of other biomolecules by changing the corresponding sequences of the capture probe and the assistant probe. PMID:24477782

  11. Seeing Objects as Faces Enhances Object Detection.

    PubMed

    Takahashi, Kohske; Watanabe, Katsumi

    2015-10-01

    The face is a special visual stimulus. Both bottom-up processes for low-level facial features and top-down modulation by face expectations contribute to the advantages of face perception. However, it is hard to dissociate the top-down factors from the bottom-up processes, since facial stimuli mandatorily lead to face awareness. In the present study, using the face pareidolia phenomenon, we demonstrated that face awareness, namely seeing an object as a face, enhances object detection performance. In face pareidolia, some people see a visual stimulus, for example, three dots arranged in V shape, as a face, while others do not. This phenomenon allows us to investigate the effect of face awareness leaving the stimulus per se unchanged. Participants were asked to detect a face target or a triangle target. While target per se was identical between the two tasks, the detection sensitivity was higher when the participants recognized the target as a face. This was the case irrespective of the stimulus eccentricity or the vertical orientation of the stimulus. These results demonstrate that seeing an object as a face facilitates object detection via top-down modulation. The advantages of face perception are, therefore, at least partly, due to face awareness.

  12. Seeing Objects as Faces Enhances Object Detection

    PubMed Central

    Watanabe, Katsumi

    2015-01-01

    The face is a special visual stimulus. Both bottom-up processes for low-level facial features and top-down modulation by face expectations contribute to the advantages of face perception. However, it is hard to dissociate the top-down factors from the bottom-up processes, since facial stimuli mandatorily lead to face awareness. In the present study, using the face pareidolia phenomenon, we demonstrated that face awareness, namely seeing an object as a face, enhances object detection performance. In face pareidolia, some people see a visual stimulus, for example, three dots arranged in V shape, as a face, while others do not. This phenomenon allows us to investigate the effect of face awareness leaving the stimulus per se unchanged. Participants were asked to detect a face target or a triangle target. While target per se was identical between the two tasks, the detection sensitivity was higher when the participants recognized the target as a face. This was the case irrespective of the stimulus eccentricity or the vertical orientation of the stimulus. These results demonstrate that seeing an object as a face facilitates object detection via top-down modulation. The advantages of face perception are, therefore, at least partly, due to face awareness. PMID:27648219

  13. Seeing Objects as Faces Enhances Object Detection

    PubMed Central

    Watanabe, Katsumi

    2015-01-01

    The face is a special visual stimulus. Both bottom-up processes for low-level facial features and top-down modulation by face expectations contribute to the advantages of face perception. However, it is hard to dissociate the top-down factors from the bottom-up processes, since facial stimuli mandatorily lead to face awareness. In the present study, using the face pareidolia phenomenon, we demonstrated that face awareness, namely seeing an object as a face, enhances object detection performance. In face pareidolia, some people see a visual stimulus, for example, three dots arranged in V shape, as a face, while others do not. This phenomenon allows us to investigate the effect of face awareness leaving the stimulus per se unchanged. Participants were asked to detect a face target or a triangle target. While target per se was identical between the two tasks, the detection sensitivity was higher when the participants recognized the target as a face. This was the case irrespective of the stimulus eccentricity or the vertical orientation of the stimulus. These results demonstrate that seeing an object as a face facilitates object detection via top-down modulation. The advantages of face perception are, therefore, at least partly, due to face awareness.

  14. Seeing Objects as Faces Enhances Object Detection.

    PubMed

    Takahashi, Kohske; Watanabe, Katsumi

    2015-10-01

    The face is a special visual stimulus. Both bottom-up processes for low-level facial features and top-down modulation by face expectations contribute to the advantages of face perception. However, it is hard to dissociate the top-down factors from the bottom-up processes, since facial stimuli mandatorily lead to face awareness. In the present study, using the face pareidolia phenomenon, we demonstrated that face awareness, namely seeing an object as a face, enhances object detection performance. In face pareidolia, some people see a visual stimulus, for example, three dots arranged in V shape, as a face, while others do not. This phenomenon allows us to investigate the effect of face awareness leaving the stimulus per se unchanged. Participants were asked to detect a face target or a triangle target. While target per se was identical between the two tasks, the detection sensitivity was higher when the participants recognized the target as a face. This was the case irrespective of the stimulus eccentricity or the vertical orientation of the stimulus. These results demonstrate that seeing an object as a face facilitates object detection via top-down modulation. The advantages of face perception are, therefore, at least partly, due to face awareness. PMID:27648219

  15. Detection of 2D phase transitions at the electrode/electrolyte interface using electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Tymoczko, Jakub; Colic, Viktor; Bandarenka, Aliaksandr S.; Schuhmann, Wolfgang

    2015-01-01

    The capacitance of the electric double layer, CDL, formed at the electrode/electrolyte interface is generally determined by electrochemical impedance spectroscopy (EIS). However, CDL values obtained using EIS data often depend on the ac frequency of the potential perturbation used in EIS. The reasons for the observed frequency dispersions can be various, and hence extracting valuable information about the status of the electrified interface is not possible with the required certainty. In this work, using well-understood electrochemical systems, namely Pt(111) electrodes in contact with a series of acidic sulfate ions containing electrolytes, we provide strong evidence that 2D phase transitions in the adsorbate layers and, in general, structural effects at the electrode/electrolyte interface are in many cases responsible for the frequency dispersion of the double layer capacitance. These empirical findings open new opportunities for the detection and evaluation of 2D phase transition processes and other structural effects using EIS, even in presence of simultaneously occurring electrochemical processes. However, further theoretical elaboration of this effect is necessary.

  16. Electrochemical Surface Plasmon Resonance Fiber-Optic Sensor: In Situ Detection of Electroactive Biofilms.

    PubMed

    Yuan, Yong; Guo, Tuan; Qiu, Xuhui; Tang, Jiahuan; Huang, Yunyun; Zhuang, Li; Zhou, Shungui; Li, Zhaohui; Guan, Bai-Ou; Zhang, Xuming; Albert, Jacques

    2016-08-01

    Spectroelectrochemistry has been found to be an efficient technique for revealing extracellular electron transfer (EET) mechanism of electroactive biofilms (EABs). Herein, we propose a novel electrochemical surface plasmon resonance (EC-SPR) optical fiber sensor for monitoring EABs in situ. The sensor uses a tilted fiber Bragg grating (TFBG) imprinted in a commercial single-mode fiber and coated with nanoscale gold film for high-efficiency SPR excitation. The wavelength shift of the surface plasmon resonance (SPR) over the fiber surface clearly identifies the electrochemical activity of the surface localized (adjacent to the electrode interface) bacterial cells in EABs, which differs from the "bulk" detections of the conventional electrochemical measurements. A close relationship between the variations of redox state of the EABs and the changes of the SPR under potentiostatic conditions has been achieved, pointing to a new way to study the EET mechanism of the EABs. Benefiting from its compact size, high sensitivity, and ease of use, together with remote operation ability, the proposed sensor opens up a multitude of opportunities for monitoring EABs in various hard-to-reach environments. PMID:27214753

  17. Electrochemical detection of nitrite on poly(pyronin Y)/graphene nanocomposites modified ITO substrate

    NASA Astrophysics Data System (ADS)

    Şinoforoğlu, Mehmet; Dağcı, Kader; Alanyalıoğlu, Murat; Meral, Kadem

    2016-06-01

    The present study reports on an easy preparation of poly(pyronin Y)/graphene (poly(PyY)/graphene) nanocomposites thin films on indium tin oxide coated glass substrates (ITO). The thin films of poly(PyY)/graphene nanocomposites are prepared by a novel method consisting of three steps; (i) preparation of graphene oxide (GO) thin films on ITO by spin-coating method, (ii) self-assembly of PyY molecules from aqueous solution onto the GO thin film, (iii) surface-confined electropolymerization (SCEP) of the adsorbed PyY molecules on the GO thin film. The as-prepared poly(PyY)/graphene nanocomposites thin films are characterized by using electroanalytical and spectroscopic techniques. Afterwards, the graphene-based polymeric dye thin film on ITO is used as an electrode in an electrochemical cell. Its performance is tested for electrochemical detection of nitrite. Under optimized conditions, the electrocatalytical effect of the nanocomposites thin film through electrochemical oxidation of nitrite is better than that of GO coated ITO.

  18. Novel reagentless paper-based screen-printed electrochemical sensor to detect phosphate.

    PubMed

    Cinti, Stefano; Talarico, Daria; Palleschi, Giuseppe; Moscone, Danila; Arduini, Fabiana

    2016-05-01

    Herein we describe a novel reagentless paper-based electrochemical phosphate sensor, manufactured with a simple and inexpensive approach. By following three easy steps, consisting of wax patterning, paper chemical modification, and electrode screen-printing, the filter paper provides an effective electroanalytical platform to sense phosphate ions in standard solutions and real samples (river water). The electrochemical properties of the paper-based platform were evaluated, firstly, by using ferricyanide as a redox mediator, proving no analyte-entrapment due to the cellulose lattice. Then, the reference colorimetric method for phosphate ions, which is based on the formation of phosphomolybdic complex, was successfully adapted to a reagentless electrochemically paper-based platform. This novel and highly sustainable configuration readily allows for the determination of phosphate ions with high reproducibility and long storage stability, achieving a detection limit of 4 μM over a wide linear range up to 300 μM. This in-house approach would be able to generically develop an affordable in situ and user-friendly sensing device without the addition of any reagent, to be applied for a broad range of analytes. PMID:27086102

  19. Electrochemical magneto immunosensor for the detection of anti-TG2 antibody in celiac disease.

    PubMed

    Kergaravat, Silvina V; Beltramino, Luis; Garnero, Nidia; Trotta, Liliana; Wagener, Marta; Isabel Pividori, Maria; Hernandez, Silvia R

    2013-10-15

    An electrochemical magneto immunosensor for the detection of anti-transglutaminase antibodies (ATG2) in celiac disease was developed. The immunological reaction is performed on magnetic beads (MBs) as a solid support in which the transglutaminase enzyme (TG2) is covalently immobilized (TG2-MB) and then ATG2 were revealed by an antibody labeled with peroxidase. The electrochemical response of the enzymatic reaction with o-phenilendiamine and H₂O₂ as substrates by square wave voltammetry was correlated with the ATG2. Graphite-epoxi composite cylindrical electrodes and screen printed electrodes were used as transducers in the immunosensor. A total number of 29 sera from clinically confirmed cases of celiac disease and 19 negative control sera were tested by the electrochemical magneto immunosensor. The data were submitted to the receiver-operating characteristic plot (ROC) analysis which indicated that 16.95 units was the most effective cut-off value (COV) to discriminate correctly between celiac and non-celiac patients. Using this point for prediction, sensitivity was found to be 100%, while specificity was 84%. PMID:23685317

  20. Electrochemical magneto immunosensor for the detection of anti-TG2 antibody in celiac disease.

    PubMed

    Kergaravat, Silvina V; Beltramino, Luis; Garnero, Nidia; Trotta, Liliana; Wagener, Marta; Isabel Pividori, Maria; Hernandez, Silvia R

    2013-10-15

    An electrochemical magneto immunosensor for the detection of anti-transglutaminase antibodies (ATG2) in celiac disease was developed. The immunological reaction is performed on magnetic beads (MBs) as a solid support in which the transglutaminase enzyme (TG2) is covalently immobilized (TG2-MB) and then ATG2 were revealed by an antibody labeled with peroxidase. The electrochemical response of the enzymatic reaction with o-phenilendiamine and H₂O₂ as substrates by square wave voltammetry was correlated with the ATG2. Graphite-epoxi composite cylindrical electrodes and screen printed electrodes were used as transducers in the immunosensor. A total number of 29 sera from clinically confirmed cases of celiac disease and 19 negative control sera were tested by the electrochemical magneto immunosensor. The data were submitted to the receiver-operating characteristic plot (ROC) analysis which indicated that 16.95 units was the most effective cut-off value (COV) to discriminate correctly between celiac and non-celiac patients. Using this point for prediction, sensitivity was found to be 100%, while specificity was 84%.

  1. Direct electrochemical detection of kanamycin based on peroxidase-like activity of gold nanoparticles.

    PubMed

    Wang, Chunshuai; Liu, Chang; Luo, Jibao; Tian, Yaping; Zhou, Nandi

    2016-09-14

    An enzyme-free, ultrasensitive electrochemical detection of kanamycin residue was achieved based on mimetic peroxidase activity of gold nanoparticles (AuNPs) and target-induced replacement of the aptamer. AuNPs which were synthesized using tyrosine as a reducing and capping agent, exhibited mimetic peroxidase activity. In the presence of kanamycin-specific aptamer, however, the single-stranded DNA (ssDNA) adsorbed on the surface of AuNPs via the interaction between the bases of ssDNA and AuNPs, and therefore blocked the catalytic site of AuNPs, and inhibited their peroxidase activity. While in the presence of target kanamycin, it bound with the adsorbed aptamer on AuNPs with high affinity, exposed the surface of AuNPs and recovered the peroxidase activity. Then AuNPs catalyzed the reaction between H2O2 and reduced thionine to produce oxidized thionine. The latter exhibited a distinct reduction peak on gold electrode in differential pulse voltammetry (DPV), and could be utilized to quantify the concentration of kanamycin. Under the optimized conditions, the proposed electrochemical assay showed an extremely high sensitivity towards kanamycin, with a linear relationship between the peak current and the concentration of kanamycin in the range of 0.1-60 nM, and a detection limit of 0.06 nM. Moreover, the established approach was successfully applied in the detection of kanamycin in honey samples. Therefore, the proposed electrochemical assay has great potential in the fields of food quality control and environmental monitoring. PMID:27566341

  2. Multi-channel PMMA microfluidic biosensor with integrated IDUAs for electrochemical detection

    PubMed Central

    Wongkaew, Nongnoot; He, Peng; Kurth, Vanessa; Surareungchai, Werasak; Baeumner, Antje J.

    2013-01-01

    A novel multi-channel poly(methyl methacrylate) (PMMA) microfluidic biosensor with interdigitated ultramicroelectrode arrays (IDUAs) for electrochemical detection was developed. The focus of the development was a simple fabrication procedure and the realization of a reliable large IDUA that can provide detection simultaneously to several microchannels. As proof of concept, five microchannels are positioned over a large single IDUA where the channels are parallel with the length of electrode finger. The IDUAs were fabricated on the PMMA cover piece and bonded to a PMMA substrate containing the microfluidic channels using UV/ozone-assisted thermal bonding. Conditions of device fabrication were optimized realizing a rugged large IDUA within a bonded PMMA device. Gold adhesion to the PMMA, protective coatings and pressure during bonding were optimized. Its electrochemical performance was studied using amperometric detection of potassium ferri and ferro hexacyanide. Cumulative signals within the same chip showed very good linearity over a range of 0 - 38 μM (R2 = 0.98) and a limit of detection of 3.48 μM. The bonding of the device was optimized so that no cross-talk between the channels was observed which otherwise would have resulted in unreliable electrochemical responses. The highly reproducible signals achieved were comparable to those obtained with separate single-channel devices. Subsequently, the multi-channel microfluidic chip was applied to a model bioanalytical detection strategy, i.e. the quantification of specific nucleic acid sequences using a sandwich approach. Here probe-coated paramagnetic beads and probe-tagged liposomes entrapping ferri/ferro hexacyanide as the redox marker were used to bind to a single stranded DNA sequence. Flow rates of the non-ionic detergent n-octyl-β-D-glucopyranoside (OG) for liposome lysis were optimized and the detection of the target sequences was carried out coulometrically within 250 s and with a limit of detection of 12

  3. Anomaly detection enhanced classification in computer intrusion detection

    SciTech Connect

    Fugate, M. L.; Gattiker, J. R.

    2002-01-01

    This report describes work with the goal of enhancing capabilities in computer intrusion detection. The work builds upon a study of classification performance, that compared various methods of classifying information derived from computer network packets into attack versus normal categories, based on a labeled training dataset. This previous work validates our classification methods, and clears the ground for studying whether and how anomaly detection can be used to enhance this performance, The DARPA project that initiated the dataset used here concluded that anomaly detection should be examined to boost the performance of machine learning in the computer intrusion detection task. This report investigates the data set for aspects that will be valuable for anomaly detection application, and supports these results with models constructed from the data. In this report, the term anomaly detection means learning a model from unlabeled data, and using this to make some inference about future data. Our data is a feature vector derived from network packets: an 'example' or 'sample'. On the other hand, classification means building a model from labeled data, and using that model to classify unlabeled (future) examples. There is some precedent in the literature for combining these methods. One approach is to stage the two techniques, using anomaly detection to segment data into two sets for classification. An interpretation of this is a method to combat nonstationarity in the data. In our previous work, we demonstrated that the data has substantial temporal nonstationarity. With classification methods that can be thought of as learning a decision surface between two statistical distributions, performance is expected to degrade significantly when classifying examples that are from regions not well represented in the training set. Anomaly detection can be seen as a problem of learning the density (landscape) or the support (boundary) of a statistical distribution so that

  4. Novel quasi-symmetric solid oxide fuel cells with enhanced electrochemical performance

    NASA Astrophysics Data System (ADS)

    Chen, Yonghong; Cheng, Zhuanxia; Yang, Yang; Gu, Qingwen; Tian, Dong; Lu, Xiaoyong; Yu, Weili; Lin, Bin

    2016-04-01

    Symmetrical solid oxide fuel cell (SSOFC) using same materials as both anode and cathode simultaneously has gained extensively attentions, which can simplify fabrication process, minimize inter-diffusion between components, enhance sulfur and coking tolerance by operating the anode as the cathode in turn. With keeping the SSOFC's advantages, a novel quasi-symmetrical solid oxide fuel cell (Q-SSOFC) is proposed to further improve the performance, which optimally combines two different SSOFC electrode materials as both anode and cathode simultaneously. PrBaFe2O5+δ (PBFO) and PrBaFe1.6Ni0.4O5+δ (PBFNO, Fe is partially substituted by Ni.) are prepared and applied as both cathode and anode for SSOFC, which exhibit desirable chemical and thermal compatibility with Sm0.8Ce0.2O1.9 (SDC) electrolyte. PBFO cathode exhibits higher oxygen reduction reaction (ORR) activity than PBFNO cathode in air, whereas PBFNO anode exhibits higher hydrogen oxidation reaction (HOR) activity than PBFO anode in H2. The as-designed Q-SSOFC of PBFNO/SDC/PBFO exhibits higher electrochemical performance than the conventional SSOFCs of both PBFO/SDC/PBFO and PBFNO/SDC/PBFNO. The superior performance of Q-SSOFC is attributed to the lowest polarization resistance (Rp). The newly developed Q-SSOFCs open doors for further improvement of electrochemical performance in SSOFC, which hold more promise for various potential applications.

  5. Electrochemically enhanced adsorption of nonylphenol on carbon nanotubes: Kinetics and isotherms study.

    PubMed

    Li, Xiaona; Chen, Shuo; Li, Liying; Quan, Xie; Zhao, Huimin

    2014-02-01

    Removal of nonylphenol (NP) from aqueous solution has attracted widely attention due to its aquatic toxicity and potential to disrupt the endocrine system. In an effort to develop the effective and environment-friendly treatment method for NP, adsorption of 4-n-nonylphenol (4-NP) on multi-walled carbon nanotubes (MWCNTs) under electrochemical assistance was studied. The adsorption kinetics and isotherms were investigated at different polarization potentials and compared with those of open circuit (OC) and powder MWCNTs adsorption. The adsorption kinetics was simulated by the model including pseudo-first-order model, pseudo-second-order model and intraparticle diffusion model. The isotherm was simulated with Langmuir model and Freudlich model, respectively. Experimental results indicated that 4-NP is able to be efficiently removed at a potential of -0.6V. Comparing with that of powder MWCNTs adsorption, the initial adsorption rate υ0 at -0.6V increased 7.9-fold according to pseudo-second-order model and the maximum adsorption capacity qm improved 1.7-fold according to Langmuir model. The improved adsorption effect at negative potential was ascribed to enhanced π-π electron-donor-acceptor (EDA) interaction between 4-NP and MWCNTs under electrochemical assistance.

  6. Large-Scale Synthesis of Metal-Ion-Doped Manganese Dioxide for Enhanced Electrochemical Performance.

    PubMed

    Peng, Ruichao; Wu, Nian; Zheng, Yu; Huang, Yangbo; Luo, Yunbai; Yu, Ping; Zhuang, Lin

    2016-04-01

    One-dimensional (1D) MnO2 was widely applied in areas of enzyme biosensors, industrial sieves, and energy storage materials owing to its excellent thermal, optical, magnetic, and chemical features. However, its practical application into energy storage devices is often hindered by the bad electronic conductivity (from 10(-5) to 10(-6) S cm(-1)). As is widely known, doping with hetero elements is an efficient way to enhance the electronic conductivity of metal oxides. Herein, a novel and simple molten-salt method is developed to achieve a large-scale preparation of 1D MnO2 nanowires. Such an approach also realizes the easy tuning of electrical properties through doping with different transition metal ions. On the basis of first-principle calculation as well as four-probe measurement, we determined that the conductivity of the doped MnO2 nanowires can be promoted efficiently by utilizing such protocol. Meanwhile, a possible doping route is discussed in detail. As a result, a superior electrochemical performance can be observed in such metal ions (M(+))-doped nanowires. Such high-quality M(+)-doped MnO2 nanowires can satisfy a broad range of application needs beyond the electrochemical capacitors. PMID:26996352

  7. Hydrothermal synthesis of mesoporous metal oxide arrays with enhanced properties for electrochemical energy storage

    SciTech Connect

    Xiao, Anguo Zhou, Shibiao; Zuo, Chenggang; Zhuan, Yongbing; Ding, Xiang

    2015-01-15

    Highlights: • NiO mesoporous nanowall arrays are prepared via hydrothermal method. • Mesoporous nanowall arrays are favorable for fast ion/electron transfer. • NiO mesoporous nanowall arrays show good supercapacitor performance. - Abstract: Mesoporous nanowall NiO arrays are prepared by a facile hydrothermal synthesis method with a following annealing process. The NiO nanowall shows continuous mesopores ranging from 5 to 10 nm and grows vertically on the substrate forming a porous net-like structure with macropores of 20–300 nm. A plausible mechanism is proposed for the growth of mesoporous nanowall NiO arrays. As cathode material of pseudocapacitors, the as-prepared mesoporous nanowall NiO arrays show good pseudocapacitive performances with a high capacitance of 600 F g{sup −1} at 2 A g{sup −1} and impressive high-rate capability with a specific capacitance of 338 F g{sup −1} at 40 A g{sup −1}. In addition, the mesoporous nanowall NiO arrays possess good cycling stability. After 6000 cycles at 2 A g{sup −1}, a high capacitance of 660 F g{sup −1} is attained, and no obvious degradation is observed. The good electrochemical performance is attributed to its highly porous morphology, which provides large reaction surface and short ion diffusion paths, leading to enhanced electrochemical properties.

  8. Separation and detection of angiotensin peptides by Cu(II) complexation and capillary electrophoresis with UV and electrochemical detection.

    PubMed

    Lacher, Nathan A; Garrison, Kenneth E; Lunte, Susan M

    2002-06-01

    The use of capillary electrophoresis (CE) with on-capillary Cu(II) complexation for the determination of angiotensin and its metabolites is described. The resulting copper-peptide complexes can be detected using either UV or electrochemical (EC) detection. Optimal reaction and separation conditions for the angiotensin peptides were first determined using CE with UV detection. With UV detection, the limit of detection (signal-to noise ratio S/N = 3) for native angiotensin II was 18 microM, while the limit of detection (LOD) obtained for the copper-angiotensin II complex is 2 microM. CE with EC detection was then evaluated, yielding significantly lower LODs--2 microM for native angiotensin II and 200 nM for the copper-angiotensin II complex. The addition of copper to the run buffer improved the separation and sensitivity for both CE-UV and CE-EC detection. The method was demonstrated by monitoring the conversion of angiotensin I to angiotensin II in plasma via angiotensin-converting enzyme (ACE) and subsequent inhibition of ACE by captopril. PMID:12179974

  9. Enhancement of SOFC Cathode Electrochemical Performance Using Multi-Phase Interfaces

    SciTech Connect

    Morgan, Dane

    2015-09-30

    This work explored the use of oxide heterostructures for enhancing the catalytic and degradation properties of solid oxide fuel cell (SOFC) cathode electrodes. We focused on heterostructures of Ruddlesden-Popper and perovskite phases. Building on previous work showing enhancement of the Ruddlesden-Popper (La,Sr)2CoO4 / perovskite (La,Sr)CoO3 heterostructure compared to pure (La,Sr)CoO3 we explored the application of related heterostructures of Ruddlesden-Popper phases on perovskite (La,Sr)(Co,Fe)O3. Our approaches included thin-film electrodes, physical and electrochemical characterization, elementary reaction kinetics modeling, and ab initio simulations. We demonstrated that Sr segregation to surfaces is likely playing a critical role in the performance of (La,Sr)CoO3 and (La,Sr)(Co,Fe)O3 and that modification of this Sr segregation may be the mechanism by which Ruddlesden-Popper coatings enhance performances. We determined that (La,Sr)(Co,Fe)O3 could be enhanced in thin films by about 10× by forming a heterostructure simultaneously with (La,Sr)2CoO4 and (La,Sr)CoO3. We hope that future work will develop this heterostructure for use as a bulk porous electrode.

  10. Nitrogen-doped multiple graphene aerogel/gold nanostar as the electrochemical sensing platform for ultrasensitive detection of circulating free DNA in human serum.

    PubMed

    Ruiyi, Li; Ling, Liu; Hongxia, Bei; Zaijun, Li

    2016-05-15

    Graphene aerogel has attracted increasing attention due to its large specific surface area, high-conductivity and electronic interaction. The paper reported a facile synthesis of nitrogen-doped multiple graphene aerogel/gold nanostar (termed as N-doped MGA/GNS) and its use as the electrochemical sensing platform for detection of double stranded (dsDNA). On the one hand, the N-doped MGA offers a much better electrochemical performance compared with classical graphene aerogel. Interestingly, the performance can be enhanced by only increasing the cycle number of graphene oxide gelation. On the other hand, the hybridization with GNS further enhances the electrocatalytic activity towards Fe(CN)6(3-/4-). In addition, the N-doped MGA/GNS provides a well-defined three-dimensional architecture. The unique structure make it is easy to combine with dsDNA to form the electroactive bioconjugate. The integration not only triggers an ultrafast DNA electron and charge transfer, but also realizes a significant synergy between N-doped MGA, GNS and dsDNA. As a result, the electrochemical sensor based on the hybrid exhibits highly sensitive differential pulse voltammetric response (DPV) towards dsDNA. The DPV signal linearly increases with the increase of dsDNA concentration in the range from 1.0×10(-)(21) g ml(-)(1) to 1.0×10(-16) g ml(-1) with the detection limit of 3.9×10(-22) g ml(-1) (S/N=3). The sensitivity is much more than that of all reported DNA sensors. The analytical method was successfully applied in the electrochemical detection of circulating free DNA in human serum. The study also opens a window on the electrical properties of multiple graphene aerogel and DNA as well their hybrids to meet the needs of further applications as special nanoelectronics in molecule diagnosis, bioanalysis and catalysis. PMID:26745792

  11. Nitrogen-doped multiple graphene aerogel/gold nanostar as the electrochemical sensing platform for ultrasensitive detection of circulating free DNA in human serum.

    PubMed

    Ruiyi, Li; Ling, Liu; Hongxia, Bei; Zaijun, Li

    2016-05-15

    Graphene aerogel has attracted increasing attention due to its large specific surface area, high-conductivity and electronic interaction. The paper reported a facile synthesis of nitrogen-doped multiple graphene aerogel/gold nanostar (termed as N-doped MGA/GNS) and its use as the electrochemical sensing platform for detection of double stranded (dsDNA). On the one hand, the N-doped MGA offers a much better electrochemical performance compared with classical graphene aerogel. Interestingly, the performance can be enhanced by only increasing the cycle number of graphene oxide gelation. On the other hand, the hybridization with GNS further enhances the electrocatalytic activity towards Fe(CN)6(3-/4-). In addition, the N-doped MGA/GNS provides a well-defined three-dimensional architecture. The unique structure make it is easy to combine with dsDNA to form the electroactive bioconjugate. The integration not only triggers an ultrafast DNA electron and charge transfer, but also realizes a significant synergy between N-doped MGA, GNS and dsDNA. As a result, the electrochemical sensor based on the hybrid exhibits highly sensitive differential pulse voltammetric response (DPV) towards dsDNA. The DPV signal linearly increases with the increase of dsDNA concentration in the range from 1.0×10(-)(21) g ml(-)(1) to 1.0×10(-16) g ml(-1) with the detection limit of 3.9×10(-22) g ml(-1) (S/N=3). The sensitivity is much more than that of all reported DNA sensors. The analytical method was successfully applied in the electrochemical detection of circulating free DNA in human serum. The study also opens a window on the electrical properties of multiple graphene aerogel and DNA as well their hybrids to meet the needs of further applications as special nanoelectronics in molecule diagnosis, bioanalysis and catalysis.

  12. Amperometric electrochemical detection of pyrroloquinoline quinone in high-performance liquid chromatography.

    PubMed

    Bergethon, P R

    1990-05-01

    The electrochemistry of pyrroloquinoline quinone (PQQ) enables its reduction and oxidation at a variety of electrode surfaces. Two methods of PQQ quantitation are described using amperometric electrochemical detection after HPLC separation. In one method a single electrode is used to reduce PQQ in the eluant stream and is sensitive to as little as 10 pmol of material. The second method is a dual electrode method that takes advantage of the reversible nature of the PQQ redox cycle and though only half as sensitive as the single electrode method, it is more specific. The advantages of the method lie in its simplicity, sensitivity, and low cost.

  13. Detection of γ-radiation and heavy metals using electrochemical bacterial-based sensor

    NASA Astrophysics Data System (ADS)

    Al-Shanawa, M.; Nabok, A.; Hashim, A.; Smith, T.; Forder, S.

    2013-06-01

    The main aim of this work is to develop a simple electrochemical sensor for detection of γ-radiation and heavy metals using bacteria. A series of DC and AC electrical measurements were carried out on samples of two types of bacteria, namely Escherichia coli and Deinococcus radiodurans. As a first step, a correlation between DC and AC electrical conductivity and bacteria concentration in solution was established. The study of the effect of γ-radiation and heavy metal ions (Cd2+) on DC and AC electrical characteristics of bacteria revealed a possibility of pattern recognition of the above inhibition factors.

  14. Fast, sensitive point of care electrochemical molecular system for point mutation and select agent detection.

    PubMed

    MacLeod, J A; Nemeth, A C; Dicke, W C; Wang, D; Manalili Wheeler, S; Hannis, J C; Collier, G B; Drader, J J

    2016-07-01

    Point of care molecular diagnostics benefits from a portable battery-operated device capable of performing a fast turnaround using reliable inexpensive cartridges. We describe a prototype device for performing a molecular diagnostics test for clinical and biodefense samples in 16 minutes using a prototype capable of an 8 minute PCR reaction, followed by hybridization and detection on an electrochemical microarray based on the i-STAT® system. We used human buccal swabs for hemochromatosis testing including in-device DNA extraction. Additional clinical and biodefense samples included influenza A and bacterial select agents Bacillus anthracis, Yersinia pestis and Francisella tularensis. PMID:27280174

  15. Convection of tin in a Bridgman system. II - An electrochemical method for detecting flow regimes

    NASA Technical Reports Server (NTRS)

    Sears, B.; Fripp, A. L.; Debnam, W. J., Jr.; Woodell, G. A.; Anderson, T. J.; Narayanan, R.

    1992-01-01

    An ampoule was designed in order to obtain local flow behavior of the flow fields for convection of tin in a vertical Bridgman configuration. Multiple electrochemical cells were located along the periphery of the ampoule. Oxygen was titrated into the ampoule at one of the cell locations using a potentiostat and the concentration of oxygen was monitored at the other cell locations by operating the cells in a galvanic mode. Onset of oscillations were detected by means of thermocouples. We conclude that the flows are generally three dimensional for an aspect ratio of 5. Results on oscillations concurred with those of earlier workers. Suggestions for improved designs were made.

  16. Selective detection of dopamine with an all PEDOT:PSS Organic Electrochemical Transistor

    PubMed Central

    Gualandi, Isacco; Tonelli, Domenica; Mariani, Federica; Scavetta, Erika; Marzocchi, Marco; Fraboni, Beatrice

    2016-01-01

    An all PEDOT:PSS Organic Electrochemical Transistor (OECT) has been developed and used for the selective detection of dopamine (DA) in the presence of interfering compounds (ascorbic acid, AA and uric acid, UA). The selective response has been implemented using a potentiodynamic approach, by varying the operating gate voltage and the scan rate. The trans-conductance curves allow to obtain a linear calibration plot for AA, UA and DA and to separate the redox waves associated to each compound; for this purpose, the scan rate is an important parameter to achieve a good resolution. The sensitivities and limits of detection obtained with the OECT have been compared with those obtained by potential step amperometric techniques (cyclic voltammetry and differential pulse voltammetry), employing a PEDOT:PSS working electrode: our results prove that the all-PEDOT:PSS OECT sensitivities and limits of detection are comparable or even better than those obtained by DPV, a technique that employs a sophisticate potential wave and read-out system in order to maximize the performance of electrochemical sensors and that can hardly be considered a viable readout method in practical applications. PMID:27739467

  17. An insertion approach electrochemical aptasensor for mucin 1 detection based on exonuclease-assisted target recycling.

    PubMed

    Wen, Wei; Hu, Rong; Bao, Ting; Zhang, Xiuhua; Wang, Shengfu

    2015-09-15

    In this work, a sensitive exonuclease-assisted amplification electrochemical aptasensor through insertion approach was developed for the detection of mucin 1 (MUC 1). In order to construct the aptasensor, 6-Mercapto-1-hexanol (MCH) was used to block partial sites of gold electrode (GE), followed by thiolated capture probe self-assembled on GE. Methylene blue (MB) labeled aptamer hybridized with capture probe at both ends to form double-strand DNA. For the MB labeled termini was close to GE, the electrochemical response was remarkable. The presence of MUC 1 caused the dissociation of the double-strand DNA owing to the specific recognition of aptamer to MUC 1. Then exonuclease I (Exo I) selectively digested the aptamer which bound with MUC 1, the released MUC 1 participated new binding with the rest aptamer. Insertion approach improved the reproducibility and Exo I-catalyzed target recycling improved the sensitivity of the aptasensor significantly. Under optimal experimental conditions, the proposed aptasensor had a good linear correlation ranged from 10 pM to 1 μM with a detection limit of 4 pM (Signal to Noise ratio, S/N=3). The strategy had great potential for the simple and sensitive detection of other cancer markers.

  18. Highly sensitive homogeneous electrochemical aptasensor for antibiotic residues detection based on dual recycling amplification strategy.

    PubMed

    Wang, Xiuzhong; Dong, Shanshan; Gai, Panpan; Duan, Rui; Li, Feng

    2016-08-15

    The ubiquitous presence of antibiotic residues in foodstuff have serious health consequences for consumers from allergic reactions to the evolution of antibiotic-resistant bacteria. To address this problem, a novel homogeneous electrochemical aptasensor with high sensitivity and specificity is designed for antibiotic residues detection based on target-induced and T7 exonuclease-assisted dual recycling signal amplification strategy. It was realized by the remarkable diffusivity difference between hairpin probe and the mononucleotides towards the negatively charged indium tin oxide electrode. For the proof-of-concept experiment, ampicillin, was employed as a model analyte to examine the desirable properties of this assay. A low detection limit of 4.0pM toward ampicillin with an excellent selectivity could be achieved, which has been successfully applied to assay antibiotic in milk. What's more, compared with the immobilization-based electrochemical means, the proposed sensing system avoids the tedious and time-consuming steps of electrode modification, making the experimental processes much simpler and more convenient. With the advantages of high sensitivity, excellent selectivity and simple operation, it is believed that this strategy possesses great potential for the simple, easy and convenient detection of antibiotic residues in food safety field.

  19. Integrated hybrid polystyrene-polydimethylsiloxane device for monitoring cellular release with microchip electrophoresis and electrochemical detection

    PubMed Central

    Johnson, Alicia S.; Mehl, Benjamin T.; Martin, R. Scott

    2015-01-01

    In this work, a polystyrene (PS)-polydimethylsiloxane (PDMS) hybrid device was developed to enable the integration of cell culture with analysis by microchip electrophoresis and electrochemical detection. It is shown that this approach combines the fundamental advantages of PDMS devices (the ability to integrate pumps and valves) and PS devices (the ability to permanently embed fluidic tubing and electrodes). The embedded fused-silica capillary enables high temporal resolution measurements from off-chip cell culture dishes and the embedded electrodes provide close to real-time analysis of small molecule neurotransmitters. A novel surface treatment for improved (reversible) adhesion between PS and PDMS is described using a chlorotrimethylsilane stamping method. It is demonstrated that a Pd decoupler is efficient at handling the high current (and cathodic hydrogen production) resulting from use of high ionic strength buffers needed for cellular analysis; thus allowing an electrophoretic separation and in-channel detection. The separation of norepinephrine (NE) and dopamine (DA) in highly conductive biological buffers was optimized using a mixed surfactant system. This PS-PDMS hybrid device integrates multiple processes including continuous sampling from a cell culture dish, on-chip pump and valving technologies, microchip electrophoresis, and electrochemical detection to monitor neurotransmitter release from PC 12 cells. PMID:25663849

  20. Electrochemical Detection of Circadian Redox Rhythm in Cyanobacterial Cells via Extracellular Electron Transfer.

    PubMed

    Nishio, Koichi; Pornpitra, Tunanunkul; Izawa, Seiichiro; Nishiwaki-Ohkawa, Taeko; Kato, Souichiro; Hashimoto, Kazuhito; Nakanishi, Shuji

    2015-06-01

    Recent research on cellular circadian rhythms suggests that the coupling of transcription-translation feedback loops and intracellular redox oscillations is essential for robust circadian timekeeping. For clarification of the molecular mechanism underlying the circadian rhythm, methods that allow for the dynamic and simultaneous detection of transcription/translation and redox oscillations in living cells are needed. Herein, we report that the cyanobacterial circadian redox rhythm can be electrochemically detected based on extracellular electron transfer (EET), a process in which intracellular electrons are exchanged with an extracellular electrode. As the EET-based method is non-destructive, concurrent detection with transcription/translation rhythm using bioluminescent reporter strains becomes possible. An EET pathway that electrochemically connected the intracellular region of cyanobacterial cells with an extracellular electrode was constructed via a newly synthesized electron mediator with cell membrane permeability. In the presence of the mediator, the open circuit potential of the culture medium exhibited temperature-compensated rhythm with approximately 24 h periodicity. Importantly, such circadian rhythm of the open circuit potential was not observed in the absence of the electron mediator, indicating that the EET process conveys the dynamic information regarding the intracellular redox state to the extracellular electrode. These findings represent the first direct demonstration of the intracellular circadian redox rhythm of cyanobacterial cells.

  1. Enzyme-free signal amplification for electrochemical detection of Mycobacterium lipoarabinomannan antibody on a disposable chip.

    PubMed

    Wang, Lisong; Leng, Chuan; Tang, Sheng; Lei, Jianping; Ju, Huangxian

    2012-01-01

    A simple, rapid, and disposable immunosensor at screen printed carbon electrode (SPCE) was developed by using gold nanoparticles (AuNPs) labeled Staphylococcal protein A (Au-SPA) as the electrochemical tag for detection of lipoarabinomannan antibody (anti-LAM). The immunosensor as the disposable chip was prepared by immobilizing capture antigen on screen printed carbon working electrode by passive adsorption, and characterized with scanning electron microscopy. After binding with the anti-LAM for further capture of Au-SPA, AuNPs were introduced as an electrochemical tag by the eletrooxidation of AuNPs in 0.1M HCl to produce strong electroactive substance for signal amplification. Compared with the enzyme-based immunosensor, AuNPs as enzyme-free tag for signal amplification exhibited many advantages such as no requirement of deoxygenation, and high stability. Under optimal detection conditions and at a preoxidation potential of +1.3 V for 30s, this method achieved the linear concentration of anti-LAM from 15.6 to 1000 ng mL(-1) with a detection limit of 5.3 ng mL(-1). The immunosensor showed a good performance with high selectivity, acceptable stability, and simple operation, providing a promising application as an adjunctive tool in early tuberculosis diagnosis. PMID:22709935

  2. Direct electrochemical stripping detection of cystic-fibrosis-related DNA linked through cadmium sulfide quantum dots

    NASA Astrophysics Data System (ADS)

    Marin, Sergio; Merkoçi, Arben

    2009-02-01

    Electrochemical detection of a cadmium sulfide quantum dots (CdS QDs)-DNA complex connected to paramagnetic microbeads (MB) was performed without the need for chemical dissolving. The method is based on dropping 20 µl of CdS QD-DNA-MB suspension on the surface of a screen-printed electrode. It is followed by magnetic collection on the surface of the working electrode and electrochemical detection using square-wave voltammetry (SWV), giving a well-shaped and sensitive analytical signal. A cystic-fibrosis-related DNA sequence was sandwiched between the two DNA probes. One DNA probe is linked via biotin-streptavidin bonding with MB and the other one via thiol groups with the CdS QD used as tags. Nonspecific signals of DNA were minimized using a blocking agent and the results obtained were successfully employed in a model DNA sensor with an interest in future applications in the clinical field. The developed nanoparticle biosensing system may offer numerous opportunities in other fields where fast, low cost and efficient detection of small volume samples is required.

  3. Aptamer-based electrochemical biosensor for detection of adenosine triphosphate using a nanoporous gold platform.

    PubMed

    Kashefi-Kheyrabadi, Leila; Mehrgardi, Masoud A

    2013-12-01

    In spite of the promising applications of aptamers in the bioassays, the development of aptamer-based electrochemical biosensors with the improved limit of detection has remained a great challenge. A strategy for the amplification of signal, based on application of nanostructures as platforms for the construction of an electrochemical adenosine triphosphate (ATP) aptasensor, is introduced in the present manuscript. A sandwich assay is designed by immobilizing a fragment of aptamer on a nanoporous gold electrode (NPGE) and its association to second fragment in the presence of ATP. Consequently, 3, 4-diaminobenzoic acid (DABA), as a molecular reporter, is covalently attached to the amine-label of the second fragment, and the direct oxidation signal of DABA is followed as the analytical signal. The sensor can detect the concentrations of ATP as low as submicromolar scales. Furthermore, 3.2% decrease in signal is observed by keeping the aptasensor at 4 °C for a week in buffer solution, implying a desirable stability. Moreover, analog nucleotides, including GTP, UTP and CTP, do not show serious interferences and this sensor easily detects its target in deproteinized human blood plasma.

  4. An RNA aptamer-based electrochemical biosensor for detection of theophylline in serum.

    PubMed

    Ferapontova, Elena E; Olsen, Eva M; Gothelf, Kurt V

    2008-04-01

    An electrochemical RNA aptamer-based biosensor for rapid and label-free detection of the bronchodilator theophylline was developed. The 5'-disulfide-functionalized end of the RNA aptamer sequence was immobilized on a gold electrode, and the 3'-amino-functionalized end was conjugated with a ferrocene (Fc) redox probe. Upon binding of theophylline the aptamer switches conformation from an open unfolded state to a closed hairpin-type conformation, resulting in the increased electron-transfer efficiency between Fc and the electrode. The electrochemical response, which was measured by differential pulse voltammetry, reaches saturation within a few minutes after addition of theophylline, and the dynamic range for detecting theophylline is 0.2-10 muM. The electrode displays an inhibited response when applied directly in serum samples treated with RNase inhibitors; however a full response to the theophylline serum concentration was obtained by transferring the electrode to blank serum-free buffer solutions. It was demonstrated that theophylline is detected with high selectivity in the presence of caffeine and theobromine.

  5. Electrochemical genosensor for the rapid detection of GMO using loop-mediated isothermal amplification.

    PubMed

    Ahmed, Minhaz Uddin; Saito, Masato; Hossain, M Mosharraf; Rao, S Ramachandara; Furui, Satoshi; Hino, Akihiro; Takamura, Yuzuru; Takagi, Masahiro; Tamiya, Eiichi

    2009-05-01

    In this study, we are reporting for the first time an efficient, accurate and inexpensive rapid detection system which employs the integration of isothermal amplification and subsequent analysis of unpurified amplicons by an electrochemical system. In our experiments, loop-mediated isothermal amplification (LAMP) with its higher efficiency than PCR was performed at a constant temperature (65 degrees C). Amplification products were combined with a redox active molecule Hoechst 33258 [H33258, 2'-(4-hydroxyphenyl)-5-(4-methyl-1-piperazinyl)-2,5'-bi(1H-benzimidazole)] and analyzed by a DNA stick (DS) which is integrated with a disposable electrochemical printed (DEP) chip using linear sweep voltammetry (LSV). The DNA minor groove binding of the H33258 molecule causes a significant drop in the peak current intensity of the H33258 oxidation. The phenomenon of DNA binding induced by H33258, in addition to changes in the anodic current peak, was used to detect maize CBH 351 variety (StarLink). Since laborious probe immobilization was not required, and amplification and detection were performed on a single device, our biosensor eliminates potential cross-contamination. We believe that this type of sensor will have an unprecedented impact for environmental protection.

  6. Ultrasensitive Detection of Ferulic Acid Using Poly(diallyldimethylammonium chloride) Functionalized Graphene-Based Electrochemical Sensor

    PubMed Central

    Liu, Lin-jie; Gao, Xia; Zhang, Pei; Feng, Shi-lan; Hu, Fang-di; Li, Ying-dong; Wang, Chun-ming

    2014-01-01

    The electrochemical redox of ferulic acid (FA) was investigated systematically by cyclic voltammetry (CV) with a poly(diallyldimethylammonium chloride) functionalized graphene-modified glassy carbon electrode (PDDA-G/GCE) as a working electrode. A simple and sensitive differential pulse voltammetry (DPV) technique was proposed for the direct quantitative determination of FA in Angelica sinensis and spiked human urine samples for the first time. The dependence of the intensities of currents and potentials on nature of the supporting electrolyte, pH, scan rate, and concentration was investigated. Under optimal conditions, the proposed sensor exhibited excellent electrochemical sensitivity to FA, and the oxidation peak current was proportional to FA concentration in the range of 8.95 × 10−8 M ~5.29 × 10−5 M, with a relatively low detection limit of 4.42 × 10−8 M. This fabricated sensor also displayed acceptable reproducibility, long-term stability, and high selectivity with negligible interferences from common interfering species. Besides, it was applied to detect FA in Angelica sinensis and biological samples with satisfactory results, making it a potential alternative tool for the quantitative detection of FA in pharmaceutical analysis. PMID:24900937

  7. An exonuclease-assisted amplification electrochemical aptasensor for Hg(2+) detection based on hybridization chain reaction.

    PubMed

    Bao, Ting; Wen, Wei; Zhang, Xiuhua; Xia, Qinghua; Wang, Shengfu

    2015-08-15

    In this work, a novel electrochemical aptasensor was developed for Hg(2+) detection based on exonuclease-assisted target recycling and hybridization chain reaction (HCR) dual signal amplification strategy. The presence of Hg(2+) induced the T-rich DNA partly folded into duplex-like structure via the Hg(2+) mediated T-Hg(2+)-T base pairs, which triggered the activity of exonuclease III (Exo III). Exo III selectively digested the double-strand DNA containing multiple T-Hg(2+)-T base pairs from its 3'-end, the released Hg(2+) participated analyte recycle. With each digestion cycle, a digestion product named as help DNA was obtained, which acted as a linkage between the capture DNA and auxiliary DNA. The presence of help DNA and two auxiliary DNA collectively facilitated successful HCR process and formed long double-stranded DNA. [Ru(NH3)6](3+) was used as redox indicator, which electrostatically bound to the double strands and produced an electrochemical signal. Exo III-assisted target recycling and HCR dual amplification significantly improved the sensitivity for Hg(2+) with a detection limit of 0.12 pM (S/N=3). Furthermore, the proposed aptasensor had a promising potential for the application of Hg(2+) detection in real aquatic sample analysis. PMID:25840017

  8. Electrochemical genosensor for the rapid detection of GMO using loop-mediated isothermal amplification.

    PubMed

    Ahmed, Minhaz Uddin; Saito, Masato; Hossain, M Mosharraf; Rao, S Ramachandara; Furui, Satoshi; Hino, Akihiro; Takamura, Yuzuru; Takagi, Masahiro; Tamiya, Eiichi

    2009-05-01

    In this study, we are reporting for the first time an efficient, accurate and inexpensive rapid detection system which employs the integration of isothermal amplification and subsequent analysis of unpurified amplicons by an electrochemical system. In our experiments, loop-mediated isothermal amplification (LAMP) with its higher efficiency than PCR was performed at a constant temperature (65 degrees C). Amplification products were combined with a redox active molecule Hoechst 33258 [H33258, 2'-(4-hydroxyphenyl)-5-(4-methyl-1-piperazinyl)-2,5'-bi(1H-benzimidazole)] and analyzed by a DNA stick (DS) which is integrated with a disposable electrochemical printed (DEP) chip using linear sweep voltammetry (LSV). The DNA minor groove binding of the H33258 molecule causes a significant drop in the peak current intensity of the H33258 oxidation. The phenomenon of DNA binding induced by H33258, in addition to changes in the anodic current peak, was used to detect maize CBH 351 variety (StarLink). Since laborious probe immobilization was not required, and amplification and detection were performed on a single device, our biosensor eliminates potential cross-contamination. We believe that this type of sensor will have an unprecedented impact for environmental protection. PMID:19381392

  9. Selective detection of dopamine with an all PEDOT:PSS Organic Electrochemical Transistor

    NASA Astrophysics Data System (ADS)

    Gualandi, Isacco; Tonelli, Domenica; Mariani, Federica; Scavetta, Erika; Marzocchi, Marco; Fraboni, Beatrice

    2016-10-01

    An all PEDOT:PSS Organic Electrochemical Transistor (OECT) has been developed and used for the selective detection of dopamine (DA) in the presence of interfering compounds (ascorbic acid, AA and uric acid, UA). The selective response has been implemented using a potentiodynamic approach, by varying the operating gate voltage and the scan rate. The trans-conductance curves allow to obtain a linear calibration plot for AA, UA and DA and to separate the redox waves associated to each compound; for this purpose, the scan rate is an important parameter to achieve a good resolution. The sensitivities and limits of detection obtained with the OECT have been compared with those obtained by potential step amperometric techniques (cyclic voltammetry and differential pulse voltammetry), employing a PEDOT:PSS working electrode: our results prove that the all-PEDOT:PSS OECT sensitivities and limits of detection are comparable or even better than those obtained by DPV, a technique that employs a sophisticate potential wave and read-out system in order to maximize the performance of electrochemical sensors and that can hardly be considered a viable readout method in practical applications.

  10. Amine functionalized graphene oxide/CNT nanocomposite for ultrasensitive electrochemical detection of trinitrotoluene.

    PubMed

    Sablok, Kavita; Bhalla, Vijayender; Sharma, Priyanka; Kaushal, Roohi; Chaudhary, Shilpa; Suri, C Raman

    2013-03-15

    Binding of electron-deficient trinitrotoluene (TNT) to the electron rich amine groups on a substrate form specific charge-transfer Jackson-Meisenheimer (JM) complex. In the present work, we report formation of specific JM complex on amine functionalized reduced graphene oxide/carbon nanotubes- (a-rGO/CNT) nanocomposite leading to sensitive detection of TNT. The CNT were dispersed using graphene oxide that provides excellent dispersion by attaching to CNT through its hydrophobic domains and solubilizes through the available OH and COOH groups on screen printed electrode (SPE). The GO was reduced electrochemically to form reduced graphene that remarkably increases electrochemical properties owing to the intercalation of high aspect CNT on graphene flakes as shown by TEM micrograph. The surface amine functionalization of dropcasted and rGO/CNT was carried out using a bi-functional cross linker ethylenediamine. The extent of amine functionalization on modified electrodes was confirmed using energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and confocal microscopy. The FTIR and Raman spectra further suggested the formation of JM complex between amine functionalized electrodes and TNT leading to a shift in peak intensity together with peak broadening. The a-rGO/CNT nanocomposite prepared electrode surface leads to ultra-trace detection of TNT upto 0.01 ppb with good reproducibility (n=3). The a-rGO/CNT sensing platform could be an alternate for sensitive detection of TNT explosive for various security and environmental applications.

  11. Electrochemical detection of lung cancer specific microRNAs using 3D DNA origami nanostructures.

    PubMed

    Liu, Shuopeng; Su, Wenqiong; Li, Zonglin; Ding, Xianting

    2015-09-15

    Recent reports have indicated that aberrant expression of microRNAs is highly correlated with occurrence of lung cancer. Therefore, highly sensitive detection of lung cancer specific microRNAs provides an attractive approach in lung cancer early diagnostics. Herein, we designed 3D DNA origami structure that enables electrochemical detection of lung cancer related microRNAs. The 3D DNA origami structure is constituted of a ferrocene-tagged DNA of stem-loop structure combined with a thiolated tetrahedron DNA nanostructure at the bottom. The top portion hybridized with the lung cancer correlated microRNA, while the bottom portion was self-assembled on gold disk electrode surface, which was modified with gold nanoparticles (Au NPs) and blocked with mercaptoethanol (MCH). The preparation process and the performance of the proposed electrochemical genosensor were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimal conditions, the developed genosensor had a detection limit of 10 pM and a good linearity with microRNA concentration ranging from 100 pM to 1 µM, which showed a great potential in highly sensitive clinical cancer diagnosis application.

  12. Graphene electrode modified with electrochemically reduced graphene oxide for label-free DNA detection.

    PubMed

    Li, Bing; Pan, Genhua; Avent, Neil D; Lowry, Roy B; Madgett, Tracey E; Waines, Paul L

    2015-10-15

    A novel printed graphene electrode modified with electrochemically reduced graphene oxide was developed for the detection of a specific oligonucleotide sequence. The graphene oxide was immobilized onto the surface of a graphene electrode via π-π bonds and electrochemical reduction of graphene oxide was achieved by cyclic voltammetry. A much higher redox current was observed from the reduced graphene oxide-graphene double-layer electrode, a 42% and 36.7% increase, respectively, in comparison with that of a bare printed graphene or reduced graphene oxide electrode. The good electron transfer activity is attributed to a combination of the large number of electroactive sites in reduced graphene oxide and the high conductivity nature of graphene. The probe ssDNA was further immobilized onto the surface of the reduced graphene oxide-graphene double-layer electrode via π-π bonds and then hybridized with its target cDNA. The change of peak current due to the hybridized dsDNA could be used for quantitative sensing of DNA concentration. It has been demonstrated that a linear range from 10(-7)M to 10(-12)M is achievable for the detection of human immunodeficiency virus 1 gene with a detection limit of 1.58 × 10(-13)M as determined by three times standard deviation of zero DNA concentration.

  13. One-step electrochemical synthesis of ultrathin graphitic carbon nitride nanosheets and their application to the detection of uric acid.

    PubMed

    Lu, Qiujun; Deng, Jianhui; Hou, Yuxin; Wang, Haiyan; Li, Haitao; Zhang, Youyu

    2015-08-01

    Ultrathin graphitic carbon nitride nanosheets (g-C3N4) with a thickness of about 2 nm were synthesized by a one-step electrochemical method for the first time. The possible mechanism of the electrochemical synthesis was discussed. This as-synthesized g-C3N4 showed intrinsic peroxidase-like activity and was successfully applied for the detection of uric acid.

  14. Office paper platform for bioelectrochromic detection of electrochemically active bacteria using tungsten trioxide nanoprobes.

    PubMed

    Marques, A C; Santos, L; Costa, M N; Dantas, J M; Duarte, P; Gonçalves, A; Martins, R; Salgueiro, C A; Fortunato, E

    2015-01-01

    Electrochemically active bacteria (EAB) have the capability to transfer electrons to cell exterior, a feature that is currently explored for important applications in bioremediation and biotechnology fields. However, the number of isolated and characterized EAB species is still very limited regarding their abundance in nature. Colorimetric detection has emerged recently as an attractive mean for fast identification and characterization of analytes based on the use of electrochromic materials. In this work, WO3 nanoparticles were synthesized by microwave assisted hydrothermal synthesis and used to impregnate non-treated regular office paper substrates. This allowed the production of a paper-based colorimetric sensor able to detect EAB in a simple, rapid, reliable, inexpensive and eco-friendly method. The developed platform was then tested with Geobacter sulfurreducens, as a proof of concept. G. sulfurreducens cells were detected at latent phase with an RGB ratio of 1.10 ± 0.04, and a response time of two hours. PMID:25891213

  15. Detection of methotrexate in a flow system using electrochemical impedance spectroscopy and multivariate data analysis.

    PubMed

    Tesfalidet, Solomon; Geladi, Paul; Shimizu, Kenichi; Lindholm-Sethson, Britta

    2016-03-31

    Methotrexate (MTX), a common pharmaceutical drug in cancer therapy and treatment of rheumatic diseases, is known to cause severe adverse side effects at high dose. As the side effect may be life threatening, there is an urgent need for a continuous, bed-side monitoring of the nominal MTX serum level in a patient while the chemical is being administered. This article describes a detection of MTX using a flow system that consists two modified gold electrodes. Interaction of MTX with the antibodies fixed on the electrode surface is detected by electrochemical impedance spectroscopy and evaluated using singular value decomposition (SVD). The key finding of this work is that the change in the electrode capacitance is found to be quantitative with respect to the concentration of MTX. Moreover a calibration curve constructed using the principal component regression method has a linear range of six orders of magnitude and a detection limit of 1.65 × 10(-10) M.

  16. Development of a PMMA Electrochemical Microfluidic Device for Carcinoembryonic Antigen Detection

    NASA Astrophysics Data System (ADS)

    Van Anh, Nguyen; Van Trung, Hoang; Tien, Bui Quang; Binh, Nguyen Hai; Ha, Cao Hong; Le Huy, Nguyen; Loc, Nguyen Thai; Thu, Vu Thi; Lam, Tran Dai

    2016-05-01

    In this study, a poly(methyl methacrylate) (PMMA) microfluidic device fabricated by an inexpensive CO2 laser etching system was developed for detection of carcino-embryonic antigens (CEA). The device was capable of working in continuous mode and was designed with the aid of numerical simulation. The detection of target CEA was based on immuno-assay via magnetic particles and electrochemical sensing. The as-prepared microfluidic can be used to detect CEA at the relatively low concentration of 150 pg mL-1. The device could be reused many times, since the capture and removal of magnetic particles in the assay could be manipulated by an external magnetic field. The proposed approach appears to be suitable for high-throughput and automated analysis of large biomolecules such as tumor markers and pathogens.

  17. Office Paper Platform for Bioelectrochromic Detection of Electrochemically Active Bacteria using Tungsten Trioxide Nanoprobes

    NASA Astrophysics Data System (ADS)

    Marques, A. C.; Santos, L.; Costa, M. N.; Dantas, J. M.; Duarte, P.; Gonçalves, A.; Martins, R.; Salgueiro, C. A.; Fortunato, E.

    2015-04-01

    Electrochemically active bacteria (EAB) have the capability to transfer electrons to cell exterior, a feature that is currently explored for important applications in bioremediation and biotechnology fields. However, the number of isolated and characterized EAB species is still very limited regarding their abundance in nature. Colorimetric detection has emerged recently as an attractive mean for fast identification and characterization of analytes based on the use of electrochromic materials. In this work, WO3 nanoparticles were synthesized by microwave assisted hydrothermal synthesis and used to impregnate non-treated regular office paper substrates. This allowed the production of a paper-based colorimetric sensor able to detect EAB in a simple, rapid, reliable, inexpensive and eco-friendly method. The developed platform was then tested with Geobacter sulfurreducens, as a proof of concept. G. sulfurreducens cells were detected at latent phase with an RGB ratio of 1.10 +/- 0.04, and a response time of two hours.

  18. Office paper platform for bioelectrochromic detection of electrochemically active bacteria using tungsten trioxide nanoprobes.

    PubMed

    Marques, A C; Santos, L; Costa, M N; Dantas, J M; Duarte, P; Gonçalves, A; Martins, R; Salgueiro, C A; Fortunato, E

    2015-04-20

    Electrochemically active bacteria (EAB) have the capability to transfer electrons to cell exterior, a feature that is currently explored for important applications in bioremediation and biotechnology fields. However, the number of isolated and characterized EAB species is still very limited regarding their abundance in nature. Colorimetric detection has emerged recently as an attractive mean for fast identification and characterization of analytes based on the use of electrochromic materials. In this work, WO3 nanoparticles were synthesized by microwave assisted hydrothermal synthesis and used to impregnate non-treated regular office paper substrates. This allowed the production of a paper-based colorimetric sensor able to detect EAB in a simple, rapid, reliable, inexpensive and eco-friendly method. The developed platform was then tested with Geobacter sulfurreducens, as a proof of concept. G. sulfurreducens cells were detected at latent phase with an RGB ratio of 1.10 ± 0.04, and a response time of two hours.

  19. Determination of aspartame by ion chromatography with electrochemical integrated amperometric detection.

    PubMed

    Qu, F; Qi, Z H; Liu, K N; Mou, S F

    1999-07-30

    In this paper, the separation and determination of the sweetener aspartame by ion chromatography coupled with electrochemical amperometric detection is reported. Sodium saccharin, acesulfame-K and aspartame were separated using 27.5 mmol/l NaOH isocratic elution on a Dionex IonPac AS4A-SC separation column. Aspartame can be determined by integrated amperometric detection without interference from the other two sweeteners. The method can be applied to the determination of aspartame in powered tabletop, fruit juice and carbonated beverage samples, and the results obtained by integrated amperometry were in agreement with those obtained using a UV detection method. A method for determining analytes with an NH2 group by ion chromatography with integrated amperometry was developed.

  20. Aptamer based electrochemical sensor for detection of human lung adenocarcinoma A549 cells

    NASA Astrophysics Data System (ADS)

    Sharma, Rachna; Varun Agrawal, Ved; Sharma, Pradeep; Varshney, R.; Sinha, R. K.; Malhotra, B. D.

    2012-04-01

    We report results of the studies relating to development of an aptamer-based electrochemical biosensor for detection of human lung adenocarcinoma A549 cells. The aminated 85-mer DNA aptamer probe specific for the A549 cells has been covalently immobilized onto silane self assembled monolayer (SAM) onto ITO surface using glutaraldehyde as the crosslinker. The results of cyclic voltammetry and differential pulse voltammetry studies reveal that the aptamer functionalized bioelectrode can specifically detect lung cancer cells in the concentration range of 103 to 107 cells/ml with detection limit of 103 cells/ml within 60 s. The specificity studies of the bioelectrode have been carried out with control KB cells. No significant change in response is observed for control KB cells as compared to that of the A549 target cells.

  1. Functional Polymers in Protein Detection Platforms: Optical, Electrochemical, Electrical, Mass-Sensitive, and Magnetic Biosensors

    PubMed Central

    Hahm, Jong-in

    2011-01-01

    The rapidly growing field of proteomics and related applied sectors in the life sciences demands convenient methodologies for detecting and measuring the levels of specific proteins as well as for screening and analyzing for interacting protein systems. Materials utilized for such protein detection and measurement platforms should meet particular specifications which include ease-of-mass manufacture, biological stability, chemical functionality, cost effectiveness, and portability. Polymers can satisfy many of these requirements and are often considered as choice materials in various biological detection platforms. Therefore, tremendous research efforts have been made for developing new polymers both in macroscopic and nanoscopic length scales as well as applying existing polymeric materials for protein measurements. In this review article, both conventional and alternative techniques for protein detection are overviewed while focusing on the use of various polymeric materials in different protein sensing technologies. Among many available detection mechanisms, most common approaches such as optical, electrochemical, electrical, mass-sensitive, and magnetic methods are comprehensively discussed in this article. Desired properties of polymers exploited for each type of protein detection approach are summarized. Current challenges associated with the application of polymeric materials are examined in each protein detection category. Difficulties facing both quantitative and qualitative protein measurements are also identified. The latest efforts on the development and evaluation of nanoscale polymeric systems for improved protein detection are also discussed from the standpoint of quantitative and qualitative measurements. Finally, future research directions towards further advancements in the field are considered. PMID:21691441

  2. Palladium Nanoparticle Incorporated Porous Activated Carbon: Electrochemical Detection of Toxic Metal Ions.

    PubMed

    Veerakumar, Pitchaimani; Veeramani, Vediyappan; Chen, Shen-Ming; Madhu, Rajesh; Liu, Shang-Bin

    2016-01-20

    A facile method has been developed for fabricating selective and sensitive electrochemical sensors for the detection of toxic metal ions, which invokes incorporation of palladium nanoparticles (Pd NPs) on porous activated carbons (PACs). The PACs, which were derived from waste biomass feedstock (fruit peels), possess desirable textural properties and porosities favorable for dispersion of Pd NPs (ca. 3-4 nm) on the graphitic PAC substrate. The Pd/PAC composite materials so fabricated were characterized by a variety of different techniques, such as X-ray diffraction, field-emission transmission electron microscopy, gas physisorption/chemisorption, thermogravimetric analysis, and Raman, Fourier-transform infrared, and X-ray photon spectroscopies. The Pd/PAC-modified glassy carbon electrodes (GCEs) were exploited as electrochemical sensors for the detection of toxic heavy metal ions, viz., Cd(2+), Pb(2+), Cu(2+), and Hg(2+), which showed superior performances for both individual as well as simultaneous detections. For simultaneous detection of Cd(2+), Pb(2+), Cu(2+), and Hg(2+), a linear response in the ion concentration range of 0.5-5.5, 0.5-8.9, 0.5-5.0, and 0.24-7.5 μM, with sensitivity of 66.7, 53.8, 41.1, and 50.3 μA μM(-1) cm(-2), and detection limit of 41, 50, 66, and 54 nM, respectively, was observed. Moreover, the Pd/PAC-modified GCEs also show perspective applications in detection of metal ions in real samples, as illustrated in this study for a milk sample.

  3. CO2 Activated Carbon Aerogel with Enhanced Electrochemical Performance as a Supercapacitor Electrode Material.

    PubMed

    Lee, Eo Jin; Lee, Yoon Jae; Kim, Jeong Kwon; Hong, Ung Gi; Yi, Jongheop; Yoon, Jung Rag; Song, In Kyu

    2015-11-01

    Carbon aerogel (CA) was prepared by a sol-gel polymerization of resorcinol and formaldehyde in ambient conditions. A series of activated carbon aerogels (ACA-X, X = 1, 2, 3, 4, 5, and 6 h) were then prepared by CO2 activation of CA with a variation of activation time (X) for use as an electrode material for supercapacitor. Specific capacitances of CA and ACA-X electrodes were measured by cyclic voltammetry and galvanostatic charge/discharge methods in 6 M KOH electrolyte. Among the samples, ACA-5 h showed the highest BET surface area (2574 m2/g) and the highest specific capacitance (100 F/g). It was found that CO2 activation was a very efficient method for enhancing physicochemical property and supercapacitive electrochemical performance of activated carbon aerogel.

  4. Enhancement of the photocatalytic activity and electrochemical property of graphene-SrWO4 nanocomposite

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoyan; Nie, Yu; Yang, Hongxun; Sun, Shengnan; Chen, Yingying; Yang, Tongyi; Lin, Shengling

    2016-05-01

    SrWO4 is a promising candidate as not only photocatalyst for the removal of organic pollutants from water, but also electrode material for energy storage devices. However, the drawbacks of its poor adsorptive performance, low electrical conductivity, and high recombination rate of photogenerated electron-hole pair impede its practical applications. In this work, we have developed a new graphene/SrWO4 nanocomposite synthesized via a facile chemical precipitation method. Characterizations show that SrWO4 nanoparticles with 80 nm or so deposited on the surface of graphene nanosheets. Graphene nanosheets in the graphene-SrWO4 hybrid could increase adsorptive property, improve the electrical conductivity of hybrid, and reduce the recombination of electron-hole pairs. As a kind of photocatalyst or electrode material for supercapacitor, the binary graphene-SrWO4 hybrid presents enhanced photocatalytic activity and electrochemical property compared to pure SrWO4.

  5. Peroxidase-encapsulated cyclodextrin nanosponge immunoconjugates as a signal enhancement tool in optical and electrochemical assays.

    PubMed

    Wajs, Ewelina; Caldera, Fabrizio; Trotta, Francesco; Fragoso, Alex

    2014-01-21

    Cyclodextrin nanosponges bearing carboxylate groups have been prepared by crosslinking β-cyclodextrin with pyromellitic dianhydride to form a carboxylic acid terminated nanoporous material. The surface of the particles was covalently modified with an anti-IgG antibody and then loaded with horseradish peroxidase. The structures of unmodified and protein modified nanosponge particles were investigated by Raman spectroscopy and imaging methods. Confocal microscopy indicates that the antibody is located in the outside of the particle while HRP is encapsulated in the inner part. The possibility to use these modified nanosponges as a signal enhancement tool in enzyme-linked colorimetric and electrochemical assays was evaluated using a sandwich format comprising immobilised gliadin as an antigen, a target anti-gliadin antibody and an anti-IgG antibody conjugated to the enzyme-loaded nanosponge immunoconjugates.

  6. CO2 Activated Carbon Aerogel with Enhanced Electrochemical Performance as a Supercapacitor Electrode Material.

    PubMed

    Lee, Eo Jin; Lee, Yoon Jae; Kim, Jeong Kwon; Hong, Ung Gi; Yi, Jongheop; Yoon, Jung Rag; Song, In Kyu

    2015-11-01

    Carbon aerogel (CA) was prepared by a sol-gel polymerization of resorcinol and formaldehyde in ambient conditions. A series of activated carbon aerogels (ACA-X, X = 1, 2, 3, 4, 5, and 6 h) were then prepared by CO2 activation of CA with a variation of activation time (X) for use as an electrode material for supercapacitor. Specific capacitances of CA and ACA-X electrodes were measured by cyclic voltammetry and galvanostatic charge/discharge methods in 6 M KOH electrolyte. Among the samples, ACA-5 h showed the highest BET surface area (2574 m2/g) and the highest specific capacitance (100 F/g). It was found that CO2 activation was a very efficient method for enhancing physicochemical property and supercapacitive electrochemical performance of activated carbon aerogel. PMID:26726618

  7. Cuprous Sulfide/Reduced Graphene Oxide Hybrid Nanomaterials: Solvothermal Synthesis and Enhanced Electrochemical Performance

    NASA Astrophysics Data System (ADS)

    He, Zhanjun; Zhu, Yabo; Xing, Zheng; Wang, Zhengyuan

    2016-01-01

    The cuprous sulfide nanoparticles (CuS NPs)-decorated reduced graphene oxide (rGO) nanocomposites have been successfully prepared via a facile and efficient solvothermal synthesis method. Scanning electron microscopy and transmission electron microscopy images demonstrated that CuS micronspheres composed of nanosheets and distributed on the rGO layer in well-monodispersed form. Fourier-transform infrared spectroscopy analyses and x-ray photoelectron spectroscopy showed that graphene oxide (GO) had been reduced to rGO. The electrochemical performances of CuS/rGO nanocomposites were investigated by cyclic voltammetry and charge/discharge techniques, which showed that the specific capacitance of CuS/rGO nanocomposites was enhanced because of the introduction of rGO.

  8. Optimization for enhancement of signal effectiveness in three-dimensional (3D) cell based electrochemical biosensor.

    PubMed

    Jeong, Se Hoon; Ku, Bosung; Yi, Sang Hyun; Lee, Dong Woo; Lee, Hye Seon; Kim, Jhingook

    2011-01-01

    This study addresses the optimization for enhancement of signal effectiveness in 3D cell based electrochemical biosensor. While 2D culture has a structural limitation to mimic an in vivo, 3D culture can provide more similar cell responses. In addition, although 3D cultured cells have been applied to measure electrically, the intensity of electrical signal from cells on the electrode was extremely low. Thus, we have optimized and evaluated the condition of gelation between several types of sol-gel and cancer cells using the electrical measurement to make fine 3D cell structure on the electrode. These results show that our work can be an useful method for monitoring cell activity by compensating a limitation of 2D culture in real time. PMID:22256300

  9. Electron transfer mediated electrochemical biosensor for microRNAs detection based on metal ion functionalized titanium phosphate nanospheres at attomole level.

    PubMed

    Cheng, Fang-Fang; He, Ting-Ting; Miao, Hai-Tiao; Shi, Jian-Jun; Jiang, Li-Ping; Zhu, Jun-Jie

    2015-02-01

    MicroRNAs (miRNAs) have emerged as new candidates as diagnostic and prognostic biomarkers for the detection of a wide variety of cancers; thus, sensitive and selective detection of microRNAs is significant for early-phase cancer diagnosis and disease prevention. A novel and simple electrochemical miRNA biosensor was developed using Cd(2+)-modified titanium phosphate nanoparticles as signal unit, two DNA as capture probes, and Ru(NH3)6(3+) as electron transfer mediator. Large quantities of cadmium ions were mounted in titanium phosphate spheres to output the electrochemical signal. Because of the presence of Ru(NH3)6(3+) molecules that interacted with DNA base-pairs as electron wire, the electrochemical signal significantly increased more than 5 times. This approach achieved a wide dynamic linear range from 1.0 aM to 10.0 pM with an ultralow limit detection of 0.76 aM, exerting a substantial enhancement in sensitivity. Moreover, the proposed biosensor was sufficiently selective to discriminate the target miRNAs from homologous miRNAs and could be used for rapid and direct analysis of miRNAs in human serum. Therefore, this strategy provides a new and ultrasensitive platform for miRNA expression profiling in biomedical research and clinical diagnosis.

  10. Electrochemical Detection of p-Aminophenol by Flexible Devices Based on Multi-Wall Carbon Nanotubes Dispersed in Electrochemically Modified Nafion

    PubMed Central

    Scandurra, Graziella; Antonella, Arena; Ciofi, Carmine; Saitta, Gaetano; Lanza, Maurizio

    2014-01-01

    A conducting composite prepared by dispersing multi-walled carbon nanotubes (MWCNTs) into a host matrix consisting of Nafion, electrochemically doped with copper, has been prepared, characterized and used to modify one of the gold electrodes of simply designed electrochemical cells having copier grade transparency sheets as substrates. Electrical measurements performed in deionized water show that the Au/Nafion/Au-MWCNTs–Nafion:Cu cells can be successfully used in order to detect the presence of p-aminophenol (PAP) in water, without the need for any supporting electrolyte. The intensity of the redox peaks arising when PAP is added to deionized water is found to be linearly related to the analyte in the range from 0.2 to 1.6 μM, with a detection limit of 90 nM and a sensitivity of 7 μA·(μM−1)·cm−2. PMID:24854357

  11. A novel electrochemical sensor surface for the detection of hydrogen peroxide using cyclic bisureas/gold nanoparticle composite.

    PubMed

    Mathew, Manjusha; Sandhyarani, N

    2011-10-15

    A novel electrochemical sensor surface with enhanced sensitivity for the detection of hydrogen peroxide has been developed based on the layer-by-layer assembly of mercapto propionic acid (MPA), cystine-based polymethylene-bridged cyclic bisureas (CBU)/gold nanoparticle (AuNP) and horseradish peroxidase (HRP) on gold electrode. Possibility of a large number of hydrogen bonds, allowed by the chemical and sterical structure of the CBU ensures the proper immobilization of the enzyme in favorable orientation and retention of enzymatic activity. Efficient electron tunneling property of AuNP together with its electrocatalytic activity leads to higher sensitivity in the detection of H(2)O(2). In cyclic voltammetry measurements a cathodic current due to direct electron transfer of HRP is observed which, indicates excellent electrocatalytic activity of the sensor surface. The biosensor surface modified with gold nanoparticle and CBU showed a lower detection limit of 50 nM for hydrogen peroxide. Chronoamperometry is performed at -0.3 V and Michaelis-Menten constant K(M)(app) value is estimated to be 4.5 μM. The newly developed sensor surface showed very high stability, reproducibility and high sensitivity.

  12. An electrochemical biosensor based on DNA tetrahedron/graphene composite film for highly sensitive detection of NADH.

    PubMed

    Li, Zonglin; Su, Wenqiong; Liu, Shuopeng; Ding, Xianting

    2015-07-15

    Dihydronicotinamide adenine dinucleotide (NADH) is a major biomarker correlated with lethal diseases such as cancers and bacterial infection. Herein, we report a graphene-DNA tetrahedron-gold nanoparticle modified gold disk electrode for highly sensitive NADH detection. By assembling the DNA tetrahedron/graphene composite film on the gold disk electrode surface which prior harnessed electrochemical deposition of gold nanoparticles to enhance the effective surface area, the oxidation potential of NADH was substantially decreased to 0.28V (vs. Ag/AgCl) and surface fouling effects were successfully eliminated. Furthermore, the lower detection limit of NADH by the presented platform was reduced down to 1fM, with an upper limit of 10pM. Both the regeneration and selectivity of composite film-modified electrode are investigated and proved to be robust. The novel sensor developed here could serve as a highly sensitive probe for NADH detection, which would further benefit the field of NADH related disease diagnostics.

  13. An electrochemical biosensor for sensitive detection of microRNA-155: combining target recycling with cascade catalysis for signal amplification.

    PubMed

    Wu, Xiaoyan; Chai, Yaqin; Zhang, Pu; Yuan, Ruo

    2015-01-14

    In this work, a new electrochemical biosensor based on catalyzed hairpin assembly target recycling and cascade electrocatalysis (cytochrome c (Cyt c) and alcohol oxidase (AOx)) for signal amplification was constructed for highly sensitive detection of microRNA (miRNA). It is worth pointing out that target recycling was achieved only based on strand displacement process without the help of nuclease. Moreover, porous TiO2 nanosphere was synthesized, which could offer more surface area for Pt nanoparticles (PtNPs) enwrapping and enhance the amount of immobilized DNA strand 1 (S1) and Cyt c accordingly. With the mimicking sandwich-type reaction, the cascade catalysis amplification strategy was carried out by AOx catalyzing ethanol to acetaldehyde with the concomitant formation of high concentration of H2O2, which was further electrocatalyzed by PtNPs and Cyt c. This newly designed biosensor provided a sensitive detection of miRNA-155 from 0.8 fM to 1 nM with a relatively low detection limit of 0.35 fM.

  14. Rapid in situ detection of ultratrace 2,4-dinitrotoluene solids by a sandwiched paper-like electrochemical sensor.

    PubMed

    Wang, Juan; Jin, Wei; Zhang, Xing; Hu, Chengguo; Luo, Qingying; Lin, Yi; Hu, Shengshui

    2014-08-19

    This work reported the rapid in situ detection of ultratrace 2,4-dinitrotoluene (DNT) solids on various substrates by a sandwiched paper-like electrochemical sensor. The sensor, prepared by a simple electroless deposition method without using special instruments, possessed a unique thin-film structure of an insulated polyvinylidene fluoride (PVDF) membrane in between two gold (Au) conducting layers. The resulting gold-PVDF sandwich (GPVDFS) array exhibited excellent flexibility, porosity and electrochemical performance as a highly integrated dual-electrode sensor platform. The infiltration of nonvolatile ionic liquid (IL) electrolytes containing ferrocene (Fc) into the GPVDFS array produced a paper-like electrochemical sensor, which can directly detect ultratrace DNT solids on various substrate surfaces (e.g., plant leaves, gloves and metal knives) with detection limit as low as 0.33 ng/mm(2). The critical role of Fc in the detection of DNT at this dual-electrode sensor was explored. The compensating electrochemical oxidation of Fc at the counter/reference electrode was found to be essential to the reduction of DNT at the working electrode when IL electrolytes were employed. The present work thus demonstrated the promising applications of paper-based porous electrode arrays in developing IL-based electrochemical sensors for the in situ detection of analyte solids in complicated environments.

  15. Rapid in situ detection of ultratrace 2,4-dinitrotoluene solids by a sandwiched paper-like electrochemical sensor.

    PubMed

    Wang, Juan; Jin, Wei; Zhang, Xing; Hu, Chengguo; Luo, Qingying; Lin, Yi; Hu, Shengshui

    2014-08-19

    This work reported the rapid in situ detection of ultratrace 2,4-dinitrotoluene (DNT) solids on various substrates by a sandwiched paper-like electrochemical sensor. The sensor, prepared by a simple electroless deposition method without using special instruments, possessed a unique thin-film structure of an insulated polyvinylidene fluoride (PVDF) membrane in between two gold (Au) conducting layers. The resulting gold-PVDF sandwich (GPVDFS) array exhibited excellent flexibility, porosity and electrochemical performance as a highly integrated dual-electrode sensor platform. The infiltration of nonvolatile ionic liquid (IL) electrolytes containing ferrocene (Fc) into the GPVDFS array produced a paper-like electrochemical sensor, which can directly detect ultratrace DNT solids on various substrate surfaces (e.g., plant leaves, gloves and metal knives) with detection limit as low as 0.33 ng/mm(2). The critical role of Fc in the detection of DNT at this dual-electrode sensor was explored. The compensating electrochemical oxidation of Fc at the counter/reference electrode was found to be essential to the reduction of DNT at the working electrode when IL electrolytes were employed. The present work thus demonstrated the promising applications of paper-based porous electrode arrays in developing IL-based electrochemical sensors for the in situ detection of analyte solids in complicated environments. PMID:25072393

  16. Plasmonically enhanced thermomechanical detection of infrared radiation.

    PubMed

    Yi, Fei; Zhu, Hai; Reed, Jason C; Cubukcu, Ertugrul

    2013-04-10

    Nanoplasmonics has been an attractive area of research due to its ability to localize and manipulate freely propagating radiation on the nanometer scale for strong light-matter interactions. Meanwhile, nanomechanics has set records in the sensing of mass, force, and displacement. In this work, we report efficient coupling between infrared radiation and nanomechanical resonators through nanoantenna enhanced thermoplasmonic effects. Using efficient conversion of electromagnetic energy to mechanical energy in this plasmo-thermomechanical platform with a nanoslot plasmonic absorber integrated directly on a nanobeam mechanical resonator, we demonstrate room-temperature detection of nanowatt level power fluctuations in infrared radiation. We expect our approach, which combines nanoplasmonics with nanomechanical resonators, to lead to optically controlled nanomechanical systems enabling unprecedented functionality in biomolecular and toxic gas sensing and on-chip mass spectroscopy.

  17. An electrochemical RNA hybridization assay for detection of the fecal indicator bacterium Escherichia coli.

    PubMed

    LaGier, Michael J; Scholin, Christopher A; Fell, Jack W; Wang, Joseph; Goodwin, Kelly D

    2005-11-01

    Monitoring waters for indicator bacteria is required to protect the public from exposure to fecal pollution. Our proof-of-concept study describes a method for detecting fecal coliforms. The coliform Escherichia coli was used as a model fecal indicator. DNA probe-coated magnetic beads in combination with the electrochemical monitoring of the oxidation state of guanine nucleotides should allow for direct detection of bacterial RNA. To demonstrate this concept, we used voltammetry in connection with pencil electrodes to detect isolated E. coli 16S rRNA. Using this approach, 10(7) cells of E. coli were detected in a quantitative, reproducible fashion in 4h. Detection was achieved without a nucleic acid amplification step. The specificity of the assay for coliforms was demonstrated by testing against a panel of bacterial RNA. We also show that E. coli RNA can be detected directly from cell extracts. The method could be used for on-site detection and shows promise for adaptation into automated biosensors for water-quality monitoring. PMID:15922364

  18. Formation of Co3O4 microframes from MOFs with enhanced electrochemical performance for lithium storage and water oxidation.

    PubMed

    Feng, Yi; Yu, Xin-Yao; Paik, Ungyu

    2016-05-01

    Co3O4 microframes are synthesized through a template-engaged strategy via the etching of Co-Co Prussian blue analogue microcubes with ammonia solution and subsequent annealing treatment. Benefitting from their unique structural merits including 3D open structure and high porosity, these Co3O4 microframes exhibit enhanced electrochemical properties for both lithium-ion batteries and water oxidation.

  19. Integrated Circuits for Rapid Sample Processing and Electrochemical Detection of Biomarkers

    NASA Astrophysics Data System (ADS)

    Besant, Justin

    The trade-off between speed and sensitivity of detection is a fundamental challenge in the design of point-of-care diagnostics. As the relevant molecules in many diseases exist natively at extremely low levels, many gold-standard diagnostic tests are designed with high sensitivity at the expense of long incubations needed to amplify the target analytes. The central aim of this thesis is to design new strategies to detect biologically relevant analytes with both high speed and sensitivity. The response time of a biosensor is limited by the ability of the target analyte to accumulate to detectable levels at the sensor surface. We overcome this limitation by designing a range of integrated devices to optimize the flux of the analyte to the sensor by increasing the effective analyte concentration, shortening the required diffusion distance, and confining the analyte in close proximity to the sensor. We couple these devices with novel ultrasensitive electrochemical transduction strategies to convert rare analytes into a detectable signal. We showcase the clinical utility of these approaches with several applications including cancer diagnosis, bacterial identification, and antibiotic susceptibility profiling. We design and optimize a device to isolate rare cancer cells from the bloodstream with near 100% efficiency and 10 000-fold specificity. We analyse pathogen specific nucleic acids by lysing bacteria in close proximity to an electrochemical sensor and find that this approach has 10-fold higher sensitivity than standard lysis in bulk solution. We design an electronic chip to readout the antibiotic susceptibility profile with an hour-long incubation by concentrating bacteria into nanoliter chambers with integrated electrodes. Finally, we report a strategy for ultrasensitive visual readout of nucleic acids as low as 100 fM within 10 minutes using an amplification cascade. The strategies presented could guide the development of fast, sensitive and low-cost diagnostics

  20. Enzyme-free electrochemical immunosensor based on host-guest nanonets catalyzing amplification for procalcitonin detection.

    PubMed

    Shen, Wen-Jun; Zhuo, Ying; Chai, Ya-Qin; Yang, Zhe-Han; Han, Jing; Yuan, Ruo

    2015-02-25

    An enzyme-free electrochemical immunosensor based on the host-guest nanonets of N,N-bis(ferrocenoyl)-diaminoethane/β-cyclodextrins/poly(amidoamine) dendrimer-encapsulated Au nanoparticles (Fc-Fc/β-CD/PAMAM-Au) for procalcitonin (PCT) detection has been developed in this study. The signal probe was constructed as follows: amine-terminated β-CD was adsorbed to PAMAM-Au first, and then the prepared Fc-Fc was recognized by the β-CD to form stable host-guest nanonets. Next, secondary antibodies (Ab2) were attached into the formed netlike nanostructure of Fc-Fc/β-CD/PAMAM-Au by chemical absorption between PAMAM-Au and -NH2 of β-CD. Herein, the PAMAM-Au act not only as nanocarriers for anchoring large amounts of the β-CD and Ab2 but also as nanocatalysts to catalyze the oxidation of ascorbic acid (AA) for signal amplification. Moreover, the Fc-Fc could be stably immobilized by the hydrophobic inner cavity of β-CD as well as improving solubility by the hydrophilic exterior of β-CD. With the unique structure of two ferrocene units, Fc-Fc not only affords more electroactive groups to make the electrochemical response more sensitive but also plays a role of combining dispersive β-CD-functionalized PAMAM-Au to form the netlike nanostructure. Furthermore, Fc-Fc exhibits good catalytic activity for AA oxidation. When the detection solution contained AA, the synergetic catalysis of PAMAM-Au and Fc-Fc to AA oxidation could be obtained, realizing enzyme-free signal amplification. The proposed immunosensor provided a linear range from 1.80 pg/mL to 500 ng/mL for PCT detection and a detection limit of 0.36 pg/mL under optimal experimental conditions. Moreover, the immunosensor has shown potential application in clinical detection of PCT.

  1. Electrochemical preparation of silver and gold nanoparticles: Characterization by confocal and surface enhanced Raman microscopy

    NASA Astrophysics Data System (ADS)

    Plieth, W.; Dietz, H.; Anders, A.; Sandmann, G.; Meixner, A.; Weber, M.; Kneppe, H.

    2005-12-01

    Localized silver and gold nanoparticles, electrochemically prepared by means of the double-pulse technique, were investigated with respect to their optical and spectroscopic properties by scanning confocal microscopy combined with surface enhanced Raman spectroscopy (SERS) and subsequent comparison with the local image of scanning electron microscopy (SEM). Analogous to the silver cluster preparation technique, controlled electrodeposition of gold nanoparticles was demonstrated, varying size from 10 to 500 nm and particle density. The maximum SERS enhancement factors found in the measurements were: (i) 10 10 for silver particles and (ii) 10 8 for gold particles. The optical and spectroscopic data of the local nanoparticle structures investigated showed that SERS is a local phenomenon, because (i) only few particles are Raman active particles, (ii) strongest enhancements in SERS are obtained from particle agglomerates, (iii) typically the Raman radiation is emitted from irregular structures like the necks between two or more particles agglomerated. In the investigated range from 10 to 500 nm no significant influence of the particle size was observed.

  2. Detection EGFR exon 19 status of lung cancer patients by DNA electrochemical biosensor.

    PubMed

    Xu, Xiong-Wei; Weng, Xiu-Hua; Wang, Chang-Lian; Lin, Wei-Wei; Liu, Ai-Lin; Chen, Wei; Lin, Xin-Hua

    2016-06-15

    Epidermal growth factor receptor (EGFR) exon 19 mutation status is a very important prediction index for tyrosine kinase inhibitors (TKIs) therapy. In this paper, we constructed a superior selective sandwich-type electrochemical biosensor to detect in-frame deletions in exon 19 of EGFR in real samples of patients with non-small cell lung carcinoma. Based on the characteristics of different hybridization efficiency in different hybridization phase conditions, different region around EGFR exon 19 deletion hotspots was selected to design DNA probes to improve biosensor performance. The results confirm that alteration of deletion location in target deliberately according to different hybridization phase is able to improve selectivity of sandwich-type DNA biosensor. Satisfactory discrimination ability can be achieved when the deletions are located in the capture probe interaction region. In order to improve efficiency of ssDNA generation from dsDNA, we introduce Lambda exonuclease (λ-exo) to sandwich-type biosensor system. EGFR exon 19 statuses of clinical real samples from lung cancer patients can be discriminated successfully by the proposed method. Our research would make the electrochemical biosensor be an excellent candidate for EGFR detection for lung cancer patients. PMID:26874108

  3. Electrochemical DNA biosensor based on gold nanorods for detecting hepatitis B virus.

    PubMed

    Shakoori, Zahra; Salimian, Samaneh; Kharrazi, Sharmin; Adabi, Mahdi; Saber, Reza

    2015-01-01

    The purpose of this work was to fabricate an electrochemical DNA biosensor for detecting hepatitis B virus. Gold nanorods (GNRs), which are known for their conductivity, were used to increase surface area and consequently increase the immobilization of single-stranded DNA (ss-DNA) on the modified gold electrode. The GNRs were characterized via transmission electron microscopy. The morphology of the gold electrode before and after modification with GNRs was characterized by scanning electron microscopy. Atomic-force microscopy was used to evaluate the morphology of the GNR electrode surface before and after interaction with ss-DNA. Cyclic voltammetry was used to monitor DNA immobilization and hybridization, using [Co(phen)3](3+) as an electrochemical indicator. The target DNA sequences were quantified at a linear range from 1.0 × 10(-12) to 10.0 × 10(-6) mol L(-1), with a detection limit of 2.0 × 10(-12) mol L(-1) by 3σ. The biosensor had good specificity for distinguishing complementary DNA in the presence of non-complementary and mismatched DNA sequences. PMID:25399076

  4. Determination of Vitamin C (Ascorbic Acid) Using High Performance Liquid Chromatography Coupled with Electrochemical Detection

    PubMed Central

    Gazdik, Zbynek; Zitka, Ondrej; Petrlova, Jitka; Adam, Vojtech; Zehnalek, Josef; Horna, Ales; Reznicek, Vojtech; Beklova, Miroslava; Kizek, Rene

    2008-01-01

    Vitamin C (ascorbic acid, ascorbate, AA) is a water soluble organic compound that participates in many biological processes. The main aim of this paper was to utilize two electrochemical detectors (amperometric – Coulouchem III and coulometric – CoulArray) coupled with flow injection analysis for the detection of ascorbic acid. Primarily, we optimized the experimental conditions. The optimized conditions were as follows: detector potential 100 mV, temperature 25 °C, mobile phase 0.09% TFA:ACN, 3:97 (v/v) and flow rate 0.13 mL·min-1. The tangents of the calibration curves were 0.3788 for the coulometric method and 0.0136 for the amperometric one. The tangent of the calibration curve measured by the coulometric detector was almost 30 times higher than the tangent measured by the amperometric detector. Consequently, we coupled a CoulArray electrochemical detector with high performance liquid chromatography and estimated the detection limit for AA as 90 nM (450 fmol per 5 μL injection). The method was used for the determination of vitamin C in a pharmaceutical preparations (98 ± 2 mg per tablet), in oranges (Citrus aurantium) (varied from 30 to 56 mg/100 g fresh weight), in apples (Malus sp.) (varied from 11 to 19 mg/100 g fresh weight), and in human blood serum (varied from 38 to 78 μM). The recoveries were also determined.

  5. Direct In Vivo Electrochemical Detection of Haemoglobin in Red Blood Cells

    NASA Astrophysics Data System (ADS)

    Toh, Rou Jun; Peng, Weng Kung; Han, Jongyoon; Pumera, Martin

    2014-08-01

    The electrochemical behavior of iron ion in haemoglobin provides insight to the chemical activity in the red blood cell which is important in the field of hematology. Herein, the detection of haemoglobin in human red blood cells on glassy carbon electrode (GC) was demonstrated. Red blood cells or raw blood cells was immobilized on a glassy carbon electrode surface with Nafion films employed to sandwich the layer of biological sample firmly on the electrode surface. Cyclic voltammetry (CV) analyses revealed a well-defined reduction peak for haemoglobin at about -0.30 V (vs. Ag/AgCl) at the red blood cell (GC-Nf-RBC-3Nf) and blood (GC-Nf-B-3Nf) film modified GCE in a pH 3.5 phosphate buffer solution. We further demonstrated that the complex biological conditions of a human red blood cell displayed no interference with the detection of haemoglobin. Such findings shall have an implication on the possibilities of studying the electrochemical behaviour of haemoglobin directly from human blood, for various scientific and clinical purposes.

  6. [Comparison of photometric, electrochemical and post-column fluorescence detection for the determination of flavonoids by HPLC].

    PubMed

    Saito, A; Sugisawa, A; Umegaki, K

    2001-06-01

    For the analysis of flavonoids by HPLC, we compared three different detection methods, namely UV, electrochemical detection and post-column chelation with aluminum followed by fluorescence detection. Ten flavonoids were used: apigenin, myricetin, luteorin, taxifolin, quercetin-3-O-sulfate, kaempferol, isorhamnetin, isoquercitrin, quercetin and rutin. Nine flavonoids except apigenin were efficiently detected by the electrochemical method with a detection limit of 0.025-0.05 pmol. Flavonols having free 3-hydroxyl and 4-keto oxygen formed a fluorescent complex by post-column chelation and were detected by the fluorescence method. The detection limit of the fluorescence method was 0.05-0.5 pmol. Nine flavonoids except taxifolin were detected by the UV method (absorbance at 370 nm), but the detection level was poor (5-10 pmol). Flavonols added to human plasma were recovered by solid phase extraction, and were analyzed using the three detection methods. Most of the flavonols were efficiently detected by the electrochemical and fluorescence methods, and the detection limits were similar to those of standard samples. PMID:11577389

  7. Simultaneous analysis of neuroendocrine tumor markers by HPLC-electrochemical detection.

    PubMed

    Manickum, T

    2009-12-15

    A validated, high pressure liquid chromatographic (HPLC) method for simultaneous quantitation of urinary catecholic acids 4-hydroxy-3-methoxymandelic acid (HMMA) (vanylmandelic acid) (VMA), 4-hydroxy-3-methoxyphenylacetic acid (HVA) and 5-hydroxyindole-3-acetic acid (5-HIAA) was developed. Sample preparation involved liquid-liquid extraction of acidified urine, containing iso-HMMA (IS) as internal standard, with ether, evaporation of the organic extract, followed by reconstitution of the residue in phosphate buffer at pH 3.3. After reversed-phase HPLC at 35 degrees C and separation on a Licrospher 125mmx4mm C(18) column (5microm particle size) with phosphate buffer (pH 3.5)-acetone (950:50, v/v) as eluent, quantitation is achieved by electrochemical detection using coulometric detection at a potential of +350mV. The method was successfully applied to routine diagnosis of neuroblastoma, carcinoid syndrome and pheochromocytoma. PMID:19926540

  8. Platinum nanoparticles encapsulated metal-organic frameworks for the electrochemical detection of telomerase activity.

    PubMed

    Ling, Pinghua; Lei, Jianping; Jia, Li; Ju, Huangxian

    2016-01-21

    A simple and rapid electrochemical sensor is constructed for the detection of telomerase activity based on the electrocatalysis of platinum nanoparticle (Pt NP) encapsulated metal-organic frameworks (MOFs), which are synthesized by one-pot encapsulation of Pt NPs into prototypal MOFs, UiO-66-NH2. Integrating with the efficient electrocatalysis of Pt@MOFs towards NaBH4 oxidation, this biosensor shows the wide dynamic correlation of telomerase activity from 5 × 10(2) to 10(7) HeLa cells mL(-1) and the telomerase activity in a single HeLa cell was calculated to be 2.0 × 10(-11) IU, providing a powerful platform for detecting telomerase activity.

  9. Eco-friendly electrochemical lab-on-paper for heavy metal detection.

    PubMed

    Medina-Sánchez, Mariana; Cadevall, Miquel; Ros, Josep; Merkoçi, Arben

    2015-11-01

    A disposable electrochemical lateral flow paper-based sensing device for heavy metal detection is proposed. The quantification of lead and cadmium in aqueous samples is demonstrated in a range from 10 to 100 ppb with a limit of detection of 7 and 11 ppb respectively. Moreover, the platform itself, which is made of paper, served as a sample pretreatment material due to its filtering properties. Real samples, especially in which the matrix is usually turbid and would in principle need a previous filtration, are successfully analyzed. This lab-on-paper device is simple, low cost, easy to fabricate, and portable, being a promising tool for new point-of-care applications in environmental monitoring, public health, and food safety.

  10. Electrochemical impediometric detection of anti-HIV drug taking gold nanorods as a sensing interface.

    PubMed

    Narang, Jagriti; Malhotra, Nitesh; Singh, Gajendra; Pundir, C S

    2015-04-15

    In present work, gold nanorods were used for amplification of electrochemical sensing of anti-HIV replication drug i.e. deferiprone. Gold nanorods (nano Au) deposited onto pencil graphite electrode (PGE) has been utilized for covalent immobilization of horse radish peroxidase (HRP), via glutaraldehyde (Glu), for deferiprone detection using impedimetric technique. Gold nanorods (nano Au) prepared were characterized by TEM and XRD. The resulting nano Au sensor exhibited a good response to deferiprone with a wide linear range (0.005-1000µM) and a low detection limit 0.005µM. The biosensor also showed a short response time (within 15s). In addition, the biosensor exhibited high reproducibility, good storage stability and anti-interference ability. The applicability of the nano Au sensor is to determine deferiprone level in spiked urine and serum samples. PMID:25437372

  11. RECENT DEVELOPMENTS IN ELECTROCHEMICAL SENSORS FOR THE DETECTION OF NEUROTRANSMITTERS FOR APPLICATIONS IN BIOMEDICINE

    PubMed Central

    Özel, Rıfat Emrah; Hayat, Akhtar; Andreescu, Silvana

    2015-01-01

    Neurotransmitters are important biological molecules that are essential to many neurophysiological processes including memory, cognition, and behavioral states. The development of analytical methodologies to accurately detect neurotransmitters is of great importance in neurological and biological research. Specifically designed microelectrodes or microbiosensors have demonstrated potential for rapid, real-time measurements with high spatial resolution. Such devices can facilitate study of the role and mechanism of action of neurotransmitters and can find potential uses in biomedicine. This paper reviews the current status and recent advances in the development and application of electrochemical sensors for the detection of small-molecule neurotransmitters. Measurement challenges and opportunities of electroanalytical methods to advance study and understanding of neurotransmitters in various biological models and disease conditions are discussed. PMID:26973348

  12. Simple and Sensitive Paper-Based Device Coupling Electrochemical Sample Pretreatment and Colorimetric Detection.

    PubMed

    Silva, Thalita G; de Araujo, William R; Muñoz, Rodrigo A A; Richter, Eduardo M; Santana, Mário H P; Coltro, Wendell K T; Paixão, Thiago R L C

    2016-05-17

    We report the development of a simple, portable, low-cost, high-throughput visual colorimetric paper-based analytical device for the detection of procaine in seized cocaine samples. The interference of most common cutting agents found in cocaine samples was verified, and a novel electrochemical approach was used for sample pretreatment in order to increase the selectivity. Under the optimized experimental conditions, a linear analytical curve was obtained for procaine concentrations ranging from 5 to 60 μmol L(-1), with a detection limit of 0.9 μmol L(-1). The accuracy of the proposed method was evaluated using seized cocaine samples and an addition and recovery protocol.

  13. Enhanced Electrochemical Catalytic Efficiencies of Electrochemically Deposited Platinum Nanocubes as a Counter Electrode for Dye-Sensitized Solar Cells.

    PubMed

    Wei, Yu-Hsuan; Tsai, Ming-Chi; Ma, Chen-Chi M; Wu, Hsuan-Chung; Tseng, Fan-Gang; Tsai, Chuen-Horng; Hsieh, Chien-Kuo

    2015-12-01

    Platinum nanocubes (PtNCs) were deposited onto a fluorine-doped tin oxide glass by electrochemical deposition (ECD) method and utilized as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). In this study, we controlled the growth of the crystalline plane to synthesize the single-crystal PtNCs at room temperature. The morphologies and crystalline nanostructure of the ECD PtNCs were examined by field emission scanning electron microscopy and high-resolution transmission electron microscopy. The surface roughness of the ECD PtNCs was examined by atomic force microscopy. The electrochemical properties of the ECD PtNCs were analyzed by cyclic voltammetry, Tafel polarization, and electrochemical impedance spectra. The Pt loading was examined by inductively coupled plasma mass spectrometry. The DSSCs were assembled via an N719 dye-sensitized titanium dioxide working electrode, an iodine-based electrolyte, and a CE. The photoelectric conversion efficiency (PCE) of the DSSCs with the ECD PtNC CE was examined under the illumination of AM 1.5 (100 mWcm(-2)). The PtNCs in this study presented a single-crystal nanostructure that can raise the electron mobility to let up the charge-transfer impedance and promote the charge-transfer rate. In this work, the electrocatalytic mass activity (MA) of the Pt film and PtNCs was 1.508 and 4.088 mAmg(-1), respectively, and the MA of PtNCs was 2.71 times than that of the Pt film. The DSSCs with the pulse-ECD PtNC CE showed a PCE of 6.48 %, which is higher than the cell using the conventional Pt film CE (a PCE of 6.18 %). In contrast to the conventional Pt film CE which is fabricated by electron beam evaporation method, our pulse-ECD PtNCs maximized the Pt catalytic properties as a CE in DSSCs. The results demonstrated that the PtNCs played a good catalyst for iodide/triiodide redox couple reactions in the DSSCs and provided a potential strategy for electrochemical catalytic applications.

  14. Enhanced Electrochemical Catalytic Efficiencies of Electrochemically Deposited Platinum Nanocubes as a Counter Electrode for Dye-Sensitized Solar Cells

    NASA Astrophysics Data System (ADS)

    Wei, Yu-Hsuan; Tsai, Ming-Chi; Ma, Chen-Chi M.; Wu, Hsuan-Chung; Tseng, Fan-Gang; Tsai, Chuen-Horng; Hsieh, Chien-Kuo

    2015-12-01

    Platinum nanocubes (PtNCs) were deposited onto a fluorine-doped tin oxide glass by electrochemical deposition (ECD) method and utilized as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). In this study, we controlled the growth of the crystalline plane to synthesize the single-crystal PtNCs at room temperature. The morphologies and crystalline nanostructure of the ECD PtNCs were examined by field emission scanning electron microscopy and high-resolution transmission electron microscopy. The surface roughness of the ECD PtNCs was examined by atomic force microscopy. The electrochemical properties of the ECD PtNCs were analyzed by cyclic voltammetry, Tafel polarization, and electrochemical impedance spectra. The Pt loading was examined by inductively coupled plasma mass spectrometry. The DSSCs were assembled via an N719 dye-sensitized titanium dioxide working electrode, an iodine-based electrolyte, and a CE. The photoelectric conversion efficiency (PCE) of the DSSCs with the ECD PtNC CE was examined under the illumination of AM 1.5 (100 mWcm-2). The PtNCs in this study presented a single-crystal nanostructure that can raise the electron mobility to let up the charge-transfer impedance and promote the charge-transfer rate. In this work, the electrocatalytic mass activity (MA) of the Pt film and PtNCs was 1.508 and 4.088 mAmg-1, respectively, and the MA of PtNCs was 2.71 times than that of the Pt film. The DSSCs with the pulse-ECD PtNC CE showed a PCE of 6.48 %, which is higher than the cell using the conventional Pt film CE (a PCE of 6.18 %). In contrast to the conventional Pt film CE which is fabricated by electron beam evaporation method, our pulse-ECD PtNCs maximized the Pt catalytic properties as a CE in DSSCs. The results demonstrated that the PtNCs played a good catalyst for iodide/triiodide redox couple reactions in the DSSCs and provided a potential strategy for electrochemical catalytic applications.

  15. Enhanced Electrochemical Catalytic Efficiencies of Electrochemically Deposited Platinum Nanocubes as a Counter Electrode for Dye-Sensitized Solar Cells.

    PubMed

    Wei, Yu-Hsuan; Tsai, Ming-Chi; Ma, Chen-Chi M; Wu, Hsuan-Chung; Tseng, Fan-Gang; Tsai, Chuen-Horng; Hsieh, Chien-Kuo

    2015-12-01

    Platinum nanocubes (PtNCs) were deposited onto a fluorine-doped tin oxide glass by electrochemical deposition (ECD) method and utilized as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). In this study, we controlled the growth of the crystalline plane to synthesize the single-crystal PtNCs at room temperature. The morphologies and crystalline nanostructure of the ECD PtNCs were examined by field emission scanning electron microscopy and high-resolution transmission electron microscopy. The surface roughness of the ECD PtNCs was examined by atomic force microscopy. The electrochemical properties of the ECD PtNCs were analyzed by cyclic voltammetry, Tafel polarization, and electrochemical impedance spectra. The Pt loading was examined by inductively coupled plasma mass spectrometry. The DSSCs were assembled via an N719 dye-sensitized titanium dioxide working electrode, an iodine-based electrolyte, and a CE. The photoelectric conversion efficiency (PCE) of the DSSCs with the ECD PtNC CE was examined under the illumination of AM 1.5 (100 mWcm(-2)). The PtNCs in this study presented a single-crystal nanostructure that can raise the electron mobility to let up the charge-transfer impedance and promote the charge-transfer rate. In this work, the electrocatalytic mass activity (MA) of the Pt film and PtNCs was 1.508 and 4.088 mAmg(-1), respectively, and the MA of PtNCs was 2.71 times than that of the Pt film. The DSSCs with the pulse-ECD PtNC CE showed a PCE of 6.48 %, which is higher than the cell using the conventional Pt film CE (a PCE of 6.18 %). In contrast to the conventional Pt film CE which is fabricated by electron beam evaporation method, our pulse-ECD PtNCs maximized the Pt catalytic properties as a CE in DSSCs. The results demonstrated that the PtNCs played a good catalyst for iodide/triiodide redox couple reactions in the DSSCs and provided a potential strategy for electrochemical catalytic applications. PMID:26625891

  16. High-performance liquid chromatographic determination of linoleic acid peroxide-derived radicals using electrochemical detection.

    PubMed

    Iwahashi, H

    2000-12-29

    High-performance liquid chromatography-electrochemical detection (HPLC-ED) was applied to detect 13-hydroperoxide octadecadienoic acid (13-HPODE)-derived radicals such as the pentyl radical and octanoic acid radical. The 13-HPODE-derived radicals were successfully detected using HPLC-ED by the combined use of the spin-trapping technique with alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN). The 4-POBN-pentyl radical adduct was detected at the retention time of 18.2 +/- 0.3 min on the elution profile of HPLC-ED with an ODS column (15 cm x 4.6 mm I.D.) using a flow-rate of 1.0 ml/min with 50 mM ammonium acetate in 29% (v/v) aqueous acetonitrile. The 4-POBN-octanoic acid radical adduct was also detected at the retention time of 13.7 +/- 0.7 min using a flow-rate of 1.0 ml/min with 50 mM ammonium acetate in 14% (v/v) aqueous acetonitrile. The concentrations of the 4-POBN radical adducts were determined using HPLC-ED without an internal standard. HPLC-ED is 100 times as sensitive as HPLC-electron spin resonance (ESR) under the ESR and ED conditions employed here. Even 1.8 pmol of the 4-POBN-pentyl (or octanoic acid) radical adduct was detectable using PMID:11204234

  17. Lab-on-a-chip for rapid electrochemical detection of nerve agent Sarin.

    PubMed

    Tan, Hsih Yin; Loke, Weng Keong; Nguyen, Nam-Trung; Tan, Swee Ngin; Tay, Nam Beng; Wang, Wei; Ng, Sum Huan

    2014-04-01

    This paper reports a lab-on-a-chip for the detection of Sarin nerve agent based on rapid electrochemical detection. The chemical warfare agent Sarin (C₄H₁₀FO₂P, O-isopropyl methylphosphonofluoridate) is a highly toxic organophosphate that induces rapid respiratory depression, seizures and death within minutes of inhalation. As purified Sarin is colourless, odourless, water soluble and a easily disseminated nerve agent, it has been used as a weapon in terrorist or military attacks. To ascertain whether potable water supplies have been adulterated with this extremely potent poison, an inexpensive, sensitive and easy to use portable test kit would be of interest to first responders investigating such attacks. We report here an amperometric-based approach for detecting trace amounts of Sarin in water samples using a screen-printed electrode (SPE) integrated in a microfluidic chip. Enzymatic inhibition was obtained by exposing the immobilised biosensor in the microfluidic platform to Sarin in water samples. With the aid of cobalt phthalocyanine modified SPE, the device could detect Sarin at part-per-billion levels with concentration as low as 1 nM. The detection method reported here represents a significant improvement over the authors'previous optical-based detection method. PMID:24288016

  18. Electrochemical DNA biosensor for detection of porcine oligonucleotides using ruthenium(II) complex as intercalator label redox

    NASA Astrophysics Data System (ADS)

    Halid, Nurul Izni Abdullah; Hasbullah, Siti Aishah; Ahmad, Haslina; Heng, Lee Yook; Karim, Nurul Huda Abd; Harun, Siti Norain

    2014-09-01

    A DNA biosensor detection of oligonucleotides via the interactions of porcine DNA with redox active complex based on the electrochemical transduction is described. A ruthenium(II) complex, [Ru(bpy)2(PIP)]2+, (bpy = 2,2'bipyridine, PIP = 2-phenylimidazo[4,5-f[[1,10-phenanthroline]) as DNA label has been synthesized and characterized by 1H NMR and mass spectra. The study was carried out by covalent bonding immobilization of porcine aminated DNA probes sequences on screen printed electrode (SPE) modified with succinimide-acrylic microspheres and [Ru(bpy)2(PIP)]2+ was used as electrochemical redox intercalator label to detect DNA hybridization event. Electrochemical detection was performed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) over the potential range where the ruthenium (II) complex was active. The results indicate that the interaction of [Ru(bpy)2(PIP)]2+ with hybridization complementary DNA has higher response compared to single-stranded and mismatch complementary DNA.

  19. Electrochemical sensor for glutathione detection based on mercury ion triggered hybridization chain reaction signal amplification.

    PubMed

    Wang, Yonghong; Jiang, Lun; Leng, Qinggang; Wu, Yaohui; He, Xiaoxiao; Wang, Kemin

    2016-03-15

    In this work, we design a new simple and highly sensitive strategy for electrochemical detection of glutathione (GSH) via mercury ion (Hg(2+)) triggered hybridization chain reaction (HCR) signal amplification. It is observed that in the absence of GSH, a specific thymine-Hg(2+)-thymine (T-Hg(2+)-T) coordination can fold into hairpin structures. While in the presence of GSH, it thus can be chelated with Hg(2+), resulting in Hg(2+) released from the T-Hg(2+)-T hairpin complex which then forms into ssDNA structure to further hybridize with the surface-immobilized capture DNA probe on the gold electrode with a sticky tail left. The presence of two hairpin helper probes through HCR leads to the formation of extended dsDNA superstructure on the electrode surface, which therefore causes the intercalation of numerous electroactive species ([Ru(NH3)6](3+)) into the dsDNA grooves, followed by a significantly amplified signal output whose intensity is related to the concentration of the GSH. Taking advantage of merits of enzyme-free amplification power of the HCR, the inherent high sensitivity of the electrochemical technique, and label-free detection which utilizes an electroactive species as a signaling molecule that binds to the anionic phosphate backbone of DNA strands via electrostatic force, not only does the proposed strategy enable sensitive detection of GSH, but show high selectivity against other amino acid, making our method a simple and sensitive addition to the amplified GSH detection. PMID:26528805

  20. Use of epoxy-embedded electrodes to integrate electrochemical detection with microchip-based analysis systems

    PubMed Central

    Selimovic, Asmira; Johnson, Alicia S.; Kiss, István Z.; Martin, R. Scott

    2011-01-01

    A new method of fabricating electrodes for microchip devices that involves the use of Teflon molds and a commercially available epoxy to embed electrodes of various size and composition is described. The resulting epoxy base can be polished to generate a fresh electrode and sealed against PDMS-based fluidic structures. Microchip-based flow injection analysis was used to characterize the epoxy-embedded electrodes. It was shown that gold electrodes can be amalgamated with liquid mercury and the resulting mercury/gold electrode used to selectively detect glutathione from lysed red blood cells. The ability to encapsulate multiple electrode materials of differing composition enabled the integration of microchip electrophoresis with electrochemical detection. Finally, a unique feature of this approach is that the electrode connection is made from the bottom of the epoxy base. This enables the creation of three-dimensional gold pillar electrodes (65 µm in diameter and 27 µm in height) that can be integrated within a fluidic network. As compared to the use of a flat electrode of a similar diameter, the use of the pillar electrode led to improvements in both the sensitivity (72.1 pA/µM for the pillar vs. 4.2 pA/µM for the flat electrode) and limit of detection (20 nM for the pillar vs. 600 nM for the flat electrode), with catechol being the test analyte. These epoxy-embedded electrodes hold promise for the creation of inexpensive microfluidic devices that can be used to electrochemically detect biologically important analytes in a manner where the electrodes can be polished and a fresh electrode surface generated as desired. PMID:21413031

  1. Stability enhancement of an electrically tunable colloidal photonic crystal using modified electrodes with a large electrochemical potential window

    SciTech Connect

    Shim, HongShik; Gyun Shin, Chang; Heo, Chul-Joon; Jeon, Seog-Jin; Jin, Haishun; Woo Kim, Jung; Jin, YongWan; Lee, SangYoon; Gyu Han, Moon E-mail: jinklee@snu.ac.kr; Lim, Joohyun; Lee, Jin-Kyu E-mail: jinklee@snu.ac.kr

    2014-02-03

    The color tuning behavior and switching stability of an electrically tunable colloidal photonic crystal system were studied with particular focus on the electrochemical aspects. Photonic color tuning of the colloidal arrays composed of monodisperse particles dispersed in water was achieved using external electric field through lattice constant manipulation. However, the number of effective color tuning cycle was limited due to generation of unwanted ions by electrolysis of the water medium during electrical switching. By introducing larger electrochemical potential window electrodes, such as conductive diamond-like carbon or boron-doped diamond, the switching stability was appreciably enhanced through reducing the number of ions generated.

  2. Enhancing lung cancer diagnosis: electrochemical simultaneous bianalyte immunosensing using carbon nanotubes-chitosan nanocomposite.

    PubMed

    Choudhary, Meenakshi; Singh, Anu; Kaur, Satbir; Arora, Kavita

    2014-10-01

    A label-free electrochemical bianalyte immunosensor has been designed for simultaneous detection of lung cancer biomarkers (anti-MAGE A2 and anti-MAGE A11) using carbon nanotubes-chitosan (CNT-CHI) composite. To achieve this, acid-functionalized single-walled CNTs were used to prepare CNT-CHI gel and electrodes were fabricated by drop casting method onto graphite surface. Lung cancer biomarkers specific antigens (Ag), i.e., MAGE A2 and MAGE A11, were covalently immobilized onto CNT-CHI/graphite electrode separately for fabrication process. Fabricated immunoelectrodes (MAGE A2/CNT-CHI/graphite and MAGE A11/CNT-CHI/graphite) were characterized at each modification step by cyclic voltammetry (CV), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Both immunoelectrodes showed successful detection of respective analytes (anti-MAGE A2 and anti-MAGE A11) from 5 fg mL(-1) to 50 ng mL(-1) using differential pulse voltammetry (DPV). Both Ag/CNT-CHI/graphite immunoelectrodes (using MAGE A2 and MAGE A11) were independently capable of distinguishing specific and nonspecific analytes like CD59, D-dimers, etc. Response studies of both immunoelectrodes revealed successful demonstration of simultaneous detection of anti-MAGE A2 and A11 independently in a single experimental run when exposed to a mixture of various analyte concentrations in different combinations irrespective of the presence of other analyte present in the same vessel.

  3. An electrochemical immunosensor for carcinoembryonic antigen enhanced by self-assembled nanogold coatings on magnetic particles.

    PubMed

    Li, Jianping; Gao, Huiling; Chen, Zhiqiang; Wei, Xiaoping; Yang, Catherine F

    2010-04-14

    A quick and reproducible electrochemical-based immunosensor technique, using magnetic core/shell particles that are coated with self-assembled multilayer of nanogold, has been developed. Magnetic particles that are structured from Au/Fe(3)O(4) core-shells were prepared and aminated after a reaction between gold and thiourea, and additional multilayered coatings of gold nanoparticles were assembled on the surface of the core/shell particles. The carcinoembryonic antibody (anti-CEA) was immobilized on the modified magnetic particles, which were then attached on the surface of solid paraffin carbon paste electrode (SPCE) by an external magnetic field. This is an assembly of a novel immuno biosensor for carcinoembryonic antigen (CEA). The sensitivity and response features of this immunoassay are significantly affected by the surface area and the biological compatibility of the multilayered nanogold. The linear range for the detection of CEA was from 0.005 to 50 ng mL(-1) and the limit of detection (LOD) was 0.001 ng mL(-1). The LOD is approximately 500 times more sensitive than that of the traditional enzyme-linked immunosorbent assay for CEA detection.

  4. Toxicity detection of sodium nitrite, borax and aluminum potassium sulfate using electrochemical method.

    PubMed

    Yu, Dengbin; Yong, Daming; Dong, Shaojun

    2013-04-01

    Based on the inhibition effect on the respiratory chain activity of microorganisms by toxicants, an electrochemical method has been developed to measure the current variation of a mediator in the presence of microorganisms contacted with a toxicant. Microelectrode arrays were adopted in this study, which can accelerate the mass transfer rate of an analyte to the electrode and also increase the total current signal, resulting in an improvement in detection sensitivity. We selected Escherichia coli as the testee and the standard glucose-glutamic acid as an exogenous material. Under oxygen restriction, the experiments in the presence of toxicant were performed at optimum conditions (solution pH 7.0, 37 degrees C and reaction for 3 hr). The resulting solution was then separated from the suspended microorganisms and was measured by an electrochemical method, using ferricyanide as a mediator. The current signal obtained represents the reoxidation of ferrocyanide, which was transformed to inhibiting efficiency, IC50, as a quantitative measure of toxicity. The IC50 values measured were 410, 570 and 830 mg/L for sodium nitrite, borax and aluminum potassium sulfate, respectively. The results show that the toxicity sequence for these three food additives is consistent with the value reported by other methods. Furthermore, the order of damage degree to the microorganism was also observed to be: sodium nitrite > borax > aluminum potassium sulfate > blank, according to the atomic force microscopy images of E. coli after being incubated for 3 hr with the toxic compound in buffer solutions. The electrochemical method is expected to be a sensitive and simple alternative to toxicity screening for chemical food additives. PMID:23923788

  5. Toxicity detection of sodium nitrite, borax and aluminum potassium sulfate using electrochemical method.

    PubMed

    Yu, Dengbin; Yong, Daming; Dong, Shaojun

    2013-04-01

    Based on the inhibition effect on the respiratory chain activity of microorganisms by toxicants, an electrochemical method has been developed to measure the current variation of a mediator in the presence of microorganisms contacted with a toxicant. Microelectrode arrays were adopted in this study, which can accelerate the mass transfer rate of an analyte to the electrode and also increase the total current signal, resulting in an improvement in detection sensitivity. We selected Escherichia coli as the testee and the standard glucose-glutamic acid as an exogenous material. Under oxygen restriction, the experiments in the presence of toxicant were performed at optimum conditions (solution pH 7.0, 37 degrees C and reaction for 3 hr). The resulting solution was then separated from the suspended microorganisms and was measured by an electrochemical method, using ferricyanide as a mediator. The current signal obtained represents the reoxidation of ferrocyanide, which was transformed to inhibiting efficiency, IC50, as a quantitative measure of toxicity. The IC50 values measured were 410, 570 and 830 mg/L for sodium nitrite, borax and aluminum potassium sulfate, respectively. The results show that the toxicity sequence for these three food additives is consistent with the value reported by other methods. Furthermore, the order of damage degree to the microorganism was also observed to be: sodium nitrite > borax > aluminum potassium sulfate > blank, according to the atomic force microscopy images of E. coli after being incubated for 3 hr with the toxic compound in buffer solutions. The electrochemical method is expected to be a sensitive and simple alternative to toxicity screening for chemical food additives.

  6. Carbon dots-decorated multiwalled carbon nanotubes nanocomposites as a high-performance electrochemical sensor for detection of H2O2 in living cells.

    PubMed

    Bai, Jing; Sun, Chunhe; Jiang, Xiue

    2016-07-01

    A novel enzyme-free hydrogen peroxide sensor composed of carbon dots (CDs) and multi-walled carbon nanotubes (MWCNTs) was prepared. It was found that the carbon dots-decorated multi-walled carbon nanotubes nanocomposites (CDs/MWCNTs) modified glassy carbon (GC) electrode (CDs/MWCNTs/GCE) exhibited a significant synergistic electrocatalytic activity towards hydrogen peroxide reduction as compared to carbon dots or multi-walled carbon nanotubes alone, and the CDs/MWCNTs/GCE has shown a low detection limit as well as excellent stability, selectivity, and reproducibility. These remarkable analytical advantages enable the practical application of CDs/MWCNTs/GCE for the real-time tracking of hydrogen peroxide (H2O2) released from human cervical cancer cells with satisfactory results. The enhanced electrochemical activity can be assigned to the edge plane-like defective sites and lattice oxygen in the CDs/MWCNTs nanocomposites due to the small amount of decoration of carbon dots on the multi-walled carbon nanotubes. Based on a facile preparation method and with good electrochemical properties, the CDs/MWCNTs nanocomposites represent a new class of carbon electrode for electrochemical sensor applications. Graphical Abstract CDs/MWCNTs exhibited good electrocatalytic activity and stability to H2O2 reduction and can be used for real-time detection of H2O2 released from living cells.

  7. Highly sensitive electrochemical immunosensor for the detection of alpha fetoprotein based on PdNi nanoparticles and N-doped graphene nanoribbons.

    PubMed

    Li, Na; Ma, Hongmin; Cao, Wei; Wu, Dan; Yan, Tao; Du, Bin; Wei, Qin

    2015-12-15

    An ultrasensitive sandwich-type electrochemical immunosensor was designed for the quantitative detection of alpha fetoprotein (AFP). The β-cyclodextrins functionalized graphene sheets (CD-GS) were used as the sensing matrix for immobilizing adamantine-1-carboxylic acid functionalized primary anti-AFP (ADA-Ab1) and enhanced the electron transfer. PdNi alloy nanoparticles decorated N-doped graphene nanoribbons (PdNi/N-GNRs) were used as labels of secondary anti-AFP (Ab2), and PdNi alloy nanoparticles (PdNi NPs) exhibited high catalytic performance towards the reduction of H2O2. Meanwhile, with good dispersion, large specific surface area and good catalytic performance, N-doped graphene nanoribbons (N-GNRs) significantly amplified the electrochemical signal. Under the optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.0001-16 ng/mL with a low detection limit of 0.03 pg/mL. Additionally, the proposed immunosensor showed high specificity, good reproducibility and long-term stability, which have promising application in bioassay analysis.

  8. Synthesis of cobalt oxide-reduced graphene nanocomposite and its enhanced electrochemical properties as negative material for alkaline secondary battery

    NASA Astrophysics Data System (ADS)

    Xu, Yanan; Wang, Xiaofeng; An, Cuihua; Wang, Yijing; Jiao, Lifang; Yuan, Huatang

    2014-12-01

    A potential negative electrode material Co3O4@rGO is synthesized via a facile reflux condensation route. The electrochemical performances of Co3O4@rGO composite for alkaline rechargeable Ni/Co batteries have been systemically investigated for the first time. The reduced-graphene can remarkably enhance the electrochemical activity of Co3O4 materials, leading to a notable improvement of discharge capacity, cycle stability and rate capability. Interestingly, the maximum discharge capacity of Co3O4@rGO-20 (additive amount of GO is 20 mg) electrode can reach 511.4 mAh g-1 with the capacity retention of 89.1% after 100 cycles at a discharge current of 100 mA g-1. A properly electrochemical reaction mechanism of Co3O4@rGO electrode is also constructed in detail.

  9. Three-dimensionally grown thorn-like Cu nanowire arrays by fully electrochemical nanoengineering for highly enhanced hydrazine oxidation.

    PubMed

    Huang, Jianfei; Zhao, Shunan; Chen, Wei; Zhou, Ying; Yang, Xiaoling; Zhu, Yihua; Li, Chunzhong

    2016-03-21

    This communication reports fully electrochemical nanoengineering toward three-dimensionally grown thorn-like Cu nanowire arrays (CNWAs) as a highly efficient and durable electrocatalyst for hydrazine oxidation. Characterized by substantial negative shifting of the onset potential and an enlarged catalytic current density, the CNWAs afforded greatly enhanced hydrazine oxidation activity, even transcending that of the Pt/C catalyst at a higher reaction rate. The parameters of the electrochemical engineering and metallization methods were found to be essentially influential on the microstructure, and thus the electrocatalytic activity of the CNWAs. The present work typifies a flexible and expandible route toward integrated electrodes of metallic 1D nanostructures which are of interest in advancing the performance of cutting-edge electrochemical applications. PMID:26580842

  10. Facile electrochemical method and corresponding automated instrument for the detection of furfural in insulation oil.

    PubMed

    Wang, Ruili; Huang, Xinjian; Wang, Lishi

    2016-02-01

    Determining the concentration of furfural contained in the insulation oil of a transformer has been established as a method to evaluate the health status of the transformer. However, the detection of furfural involves the employment of expensive instruments and/or time-consuming laboratorial operations. In this paper, we proposed a convenient electrochemical method to make the detection. The quantification of furfural was realized by extraction of furfural from oil phase to aqueous phase followed by reductive detection of furfural with differential pulse voltammetry (DPV) at a mercury electrode. This method is very sensitive and the limit of detection, corresponding to furfural contained in oil, is estimated to be 0.03 μg g(-1). Furthermore, excellent linearity can be obtained in the range of 0-10 μg g(-1). These features make the method very suitable for the determination of furfural in real situation. A fully automated instrument that can perform the operations of extraction and detection was developed, and this instrument enables the whole measurement to be finished within eight minutes. The methodology and the instrument were tested with real samples, and very favorable agreement between results obtained with this instrument and HPLC indicates that the proposed method along with instrument can be employed as a facile tool to diagnose the health status of aged transformers.

  11. Electrochemical aptamer sensor for thrombin detection based on Au nanoneedle and enzymatic ascorbic acid oxidization.

    PubMed

    Xu, Feng; Hua, Mei; Luo, Lei; Du, Huali; Yang, Yunhui

    2013-01-01

    In this article, we describe an aptamer-based sandwich-type electrochemical sensor for the detection of human alpha-thrombin. Au nanoneedles were synthesized in the hole of the naked polycarbonate (PC) template using electrodepositing strategy. The thiolated thrombin aptamer I was immobilized as the capture probe on the gold nanoneedles through Au-S bond. After the thrombin was captured, the biotinylated aptamer II, used as the detection probe, was bound to thrombin. Then, the streptavidin-conjugated alkaline phosphatase (SA-ALP) was linked to the biotinylated aptamer II and catalyze hydrolyzation reaction of ascorbic acid 2-phosphate to produce ascorbic acid. Differential pulse voltammetry was used to detect the oxidizing current of ascorbic acid, which is proportional to the concentration of thrombin bound on the electrode surface ranging from 0.24 nM to 150 nM with a detection limit of 0.1 nM at 3 sigma. This assay is rapid, simple, sensitive and highly specific. It could be applied to detect thrombin in complex real sample.

  12. Carbohydrate derivative-functionalized biosensing toward highly sensitive electrochemical detection of cell surface glycan expression as cancer biomarker.

    PubMed

    Zhang, Xinai; Lu, Wenjie; Shen, Jianzhong; Jiang, Yuxiang; Han, En; Dong, Xiaoya; Huang, Jiali

    2015-12-15

    Accurate and highly sensitive detection of glycan expression on cell surface is extremely important for cancer diagnosis and therapy. Herein, a carbohydrate derivative-functionalized biosensor was developed for electrochemical detection of the expression level of cell surface glycan (mannose used as model). Thiomannosyl dimer was synthesized to design the thiomannosyl-functionalized biosensor by direct and rapid one-step protocols. The biosensing surface-confined mannose could effectively mimic the presentation of cell surface mannose and was responsible for competing with mannose on cancer cells in incubation solution. Greatly enhanced sensitivity was achieved by exploiting the excellent conductivity of multiwalled carbon nanotube/Au nanoparticle (MWNT/AuNP), the amplification effect of MWNTs, and the favorable catalytic ability of horseradish peroxidase (HRP). Using competitive strategy, the developed biosensor exhibits attractive performances for the analysis of mannose expression with rapid response, high sensitivity and accuracy, and possesses great promise for evaluation of cell surface glycan expression by using a greater variety of lectins.

  13. An electrochemical biosensor with nanointerface for lactate detection based on lactate dehydrogenase immobilized on zinc oxide nanorods.

    PubMed

    Nesakumar, Noel; Thandavan, Kavitha; Sethuraman, Swaminathan; Krishnan, Uma Maheswari; Rayappan, John Bosco Balaguru

    2014-01-15

    Hepatic immaturity is observed particularly in children whose age is under three, when the lactate concentration is greater than the normal level in blood. An electrochemical lactate biosensor was developed by immobilizing lactate dehydrogenase (LDH) on to ZnO nanorods at pH 7.4 via chitosan. Growth of polycrystalline ZnO nanorods towards (101) plane was confirmed using XRD. The FE-SEM study revealed the formation of ZnO nanorods with an aspect ratio of 3.24. Immobilization of LDH on ZnO nanorods was confirmed using FTIR spectra and surface coverage. Electrochemical studies were carried out through cyclic voltammetry and amperometry using three electrode system with Au/NanoZnO/LDH as working electrode, Ag/AgCl in 0.1 M KCl as reference electrode and Pt wire as counter electrode. The sensitivity of the biosensor was found to be 1.832 μA μmol(-1) L exhibiting linearity 0.2-0.8 μmol L(-1) with the detection and quantification limits of 4.73 and 15.75 nmol L(-1) respectively. The response time of Au/NanoZnO/LDH bioelectrode was found to be <1 s. Prediction band for net current was framed to enhance specificity. Michaelis-Menten constant (KM(app)) and maximum rate (Imax) values for immobilized LDH were found to be 0.38 μmol L(-1) and 2.798 μA respectively. Repeatability and reproducibility of LDH biosensor were also reported. PMID:24231089

  14. A mini-electrochemical system integrated micropipet tip and pencil graphite electrode for detection of anticancer drug sensitivity in vitro.

    PubMed

    Guo, Xiaoling; Wang, Qian; Li, Jinlian; Cui, Jiwen; Zhou, Shi; Hao, Sue; Wu, Dongmei

    2015-02-15

    Developing a reliable and cost-effective miniaturized electroanalysis tool is of vital importance for cell electrochemical analysis. In this work, a novel mini-electrochemical system has been constructed for trace detection of cell samples. The mini-electrochemical system was constructed by integrating a pencil graphite modified by threonine (PT/PGE) as working electrode, an Ag/AgCl (Sat'd) as reference electrode, platinum wire as counter electrode and a micropipet tip as electrochemical cell. The mini-electrochemical system not only saved dramatically usage of samples from 500 μL in traditional electrochemical system to 10 μL, but also possessed an adjustable active surface area by changing the length of PT/PGE immersed into the cell suspension from 3mm to 15 mm, and the linear equation was ipa = 2.25 l-2.64 (R(2) = 0.990). The system was successfully used in detection of MCF-7 cells, and a nonlinear exponent relationship between peak current and the cell number range from 3.0 × l0(3) to 7.0 × l0(6) cells mL(-1) was established firstly with the index equation ipa = 59.557 e (-C/1.709)-71.486 (R(2) = 0.954). Finally, the system was used for evaluating the sensitivity of cyclophosphamide on MCF-7 cell, and the result was corresponded well with that of MTT assay. The proposed system is sufficiently simple, cheap and easy operated, and could be applied in electrochemical detection of other biological samples.

  15. Mismatch detection in DNA monolayers by atomic force microscopy and electrochemical impedance spectroscopy

    PubMed Central

    Ambrosetti, Elena; Scoles, Giacinto; Casalis, Loredana

    2016-01-01

    Summary Background: DNA hybridization is at the basis of most current technologies for genotyping and sequencing, due to the unique properties of DNA base-pairing that guarantee a high grade of selectivity. Nonetheless the presence of single base mismatches or not perfectly matched sequences can affect the response of the devices and the major challenge is, nowadays, to distinguish a mismatch of a single base and, at the same time, unequivocally differentiate devices read-out of fully and partially matching sequences. Results: We present here two platforms based on different sensing strategies, to detect mismatched and/or perfectly matched complementary DNA strands hybridization into ssDNA oligonucleotide monolayers. The first platform exploits atomic force microscopy-based nanolithography to create ssDNA nano-arrays on gold surfaces. AFM topography measurements then monitor the variation of height of the nanostructures upon biorecognition and then follow annealing at different temperatures. This strategy allowed us to clearly detect the presence of mismatches. The second strategy exploits the change in capacitance at the interface between an ssDNA-functionalized gold electrode and the solution due to the hybridization process in a miniaturized electrochemical cell. Through electrochemical impedance spectroscopy measurements on extended ssDNA self-assembled monolayers we followed in real-time the variation of capacitance, being able to distinguish, through the difference in hybridization kinetics, not only the presence of single, double or triple mismatches in the complementary sequence, but also the position of the mismatched base pair with respect to the electrode surface. Conclusion: We demonstrate here two platforms based on different sensing strategies as sensitive and selective tools to discriminate mismatches. Our assays are ready for parallelization and can be used in the detection and quantification of single nucleotide mismatches in microRNAs or in

  16. Three-dimensionally grown thorn-like Cu nanowire arrays by fully electrochemical nanoengineering for highly enhanced hydrazine oxidation

    NASA Astrophysics Data System (ADS)

    Huang, Jianfei; Zhao, Shunan; Chen, Wei; Zhou, Ying; Yang, Xiaoling; Zhu, Yihua; Li, Chunzhong

    2016-03-01

    This communication reports fully electrochemical nanoengineering toward three-dimensionally grown thorn-like Cu nanowire arrays (CNWAs) as a highly efficient and durable electrocatalyst for hydrazine oxidation. Characterized by substantial negative shifting of the onset potential and an enlarged catalytic current density, the CNWAs afforded greatly enhanced hydrazine oxidation activity, even transcending that of the Pt/C catalyst at a higher reaction rate. The parameters of the electrochemical engineering and metallization methods were found to be essentially influential on the microstructure, and thus the electrocatalytic activity of the CNWAs. The present work typifies a flexible and expandible route toward integrated electrodes of metallic 1D nanostructures which are of interest in advancing the performance of cutting-edge electrochemical applications.This communication reports fully electrochemical nanoengineering toward three-dimensionally grown thorn-like Cu nanowire arrays (CNWAs) as a highly efficient and durable electrocatalyst for hydrazine oxidation. Characterized by substantial negative shifting of the onset potential and an enlarged catalytic current density, the CNWAs afforded greatly enhanced hydrazine oxidation activity, even transcending that of the Pt/C catalyst at a higher reaction rate. The parameters of the electrochemical engineering and metallization methods were found to be essentially influential on the microstructure, and thus the electrocatalytic activity of the CNWAs. The present work typifies a flexible and expandible route toward integrated electrodes of metallic 1D nanostructures which are of interest in advancing the performance of cutting-edge electrochemical applications. Electronic supplementary information (ESI) available: Experimental details, additional figures and table. See DOI: 10.1039/c5nr06512g

  17. Detection of parathyroid hormone using an electrochemical impedance biosensor based on PAMAM dendrimers.

    PubMed

    Özcan, Hakkı Mevlüt; Sezgintürk, Mustafa Kemal

    2015-01-01

    This paper presents a novel hormone-based impedimetric biosensor to determine parathyroid hormone (PTH) level in serum for diagnosis and monitoring treatment of hyperparathyroidism, hypoparathyroidism and thyroid cancer. The interaction between PTH and the biosensor was investigated by an electrochemical method. The biosensor was based on the gold electrode modified by 12-mercapto dodecanoic (12MDDA). Antiparathyroid hormone (anti-PTH) was covalently immobilized on to poly amidoamine dendrimer (PAMAM) which was bound to a 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide/N-hydroxysuccinimide (EDC/NHS) couple, self-assembled monolayer structure from one of the other NH2 sites. The immobilization of anti-PTH was monitored by electrochemical impedance spectroscopy, cyclic voltammetry and scanning electron microscope techniques. After the optimization studies of immobilization materials such as 12MDDA, EDC-NHS, PAMAM, and glutaraldehyde, the performance of the biosensor was investigated in terms of linearity, sensitivity, repeatability, and reproducibility. PTH was detected within a linear range of 10-60 fg/mL. Finally the described biosensor was used to monitor PTH levels in artificial serum samples.

  18. Bare and boron-doped cubic silicon carbide nanowires for electrochemical detection of nitrite sensitively

    PubMed Central

    Yang, Tao; Zhang, Liqin; Hou, Xinmei; Chen, Junhong; Chou, Kuo-Chih

    2016-01-01

    Fabrication of eletrochemical sensors based on wide bandgap compound semiconductors has attracted increasing interest in recent years. Here we report for the first time electrochemical nitrite sensors based on cubic silicon carbide (SiC) nanowires (NWs) with smooth surface and boron-doped cubic SiC NWs with fin-like structure. Multiple techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) were used to characterize SiC and boron-doped SiC NWs. As for the electrochemical behavior of both SiC NWs electrode, the cyclic voltammetric results show that both SiC electrodes exhibit wide potential window and excellent electrocatalytic activity toward nitrite oxidation. Differential pulse voltammetry (DPV) determination reveals that there exists a good linear relationship between the oxidation peak current and the concentration in the range of 50–15000 μmoL L−1 (cubic SiC NWs) and 5–8000 μmoL L−1 (B-doped cubic SiC NWs) with the detection limitation of 5 and 0.5 μmoL L−1 respectively. Compared with previously reported results, both as-prepared nitrite sensors exhibit wider linear response range with comparable high sensitivity, high stability and reproducibility. PMID:27109361

  19. Bare and boron-doped cubic silicon carbide nanowires for electrochemical detection of nitrite sensitively.

    PubMed

    Yang, Tao; Zhang, Liqin; Hou, Xinmei; Chen, Junhong; Chou, Kuo-Chih

    2016-04-25

    Fabrication of eletrochemical sensors based on wide bandgap compound semiconductors has attracted increasing interest in recent years. Here we report for the first time electrochemical nitrite sensors based on cubic silicon carbide (SiC) nanowires (NWs) with smooth surface and boron-doped cubic SiC NWs with fin-like structure. Multiple techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) were used to characterize SiC and boron-doped SiC NWs. As for the electrochemical behavior of both SiC NWs electrode, the cyclic voltammetric results show that both SiC electrodes exhibit wide potential window and excellent electrocatalytic activity toward nitrite oxidation. Differential pulse voltammetry (DPV) determination reveals that there exists a good linear relationship between the oxidation peak current and the concentration in the range of 50-15000 μmoL L(-1) (cubic SiC NWs) and 5-8000 μmoL L(-1) (B-doped cubic SiC NWs) with the detection limitation of 5 and 0.5 μmoL L(-1) respectively. Compared with previously reported results, both as-prepared nitrite sensors exhibit wider linear response range with comparable high sensitivity, high stability and reproducibility.

  20. Intergranular corrosion in a martensitic stainless steel detected by electrochemical tests

    SciTech Connect

    Alonso-Falleiros, N.; Magri, M.; Falleiros, I.G.S.

    1999-08-01

    Quenched and tempered martensitic stainless steel UNS S41000 was tested electrochemically for susceptibility to sensitization in specimens quenched from 975 C (1,248 K) and tempered for 2 h at different temperatures between 300 C (573 K) and 700 C (973 K). Besides an oxalic acid etch test, the following tests were performed using a potentiostat and 1 N sulfuric acid (H{sub 2}SO{sub 4}) solution: potentiokinetic polarization, potentiostatic etch, and electrochemical potentiokinetic reactivation in the double-loop version (DL-EPR). Tested surfaces were observed metallographically. The maximum susceptibility to intergranular corrosion was observed in the condition tempered at 550 C (823 K), and a sensitized structure was detected. For lower tempering temperatures, steel was less sensitized, or not at all, and for higher tempering temperatures, steel was less sensitized. All tests except for the oxalic acid etch were able to evaluate quantitatively different degrees of sensitization as a function of tempering temperature. The DL-EPR method was the best to discriminate degrees of sensitization.

  1. Bare and boron-doped cubic silicon carbide nanowires for electrochemical detection of nitrite sensitively.

    PubMed

    Yang, Tao; Zhang, Liqin; Hou, Xinmei; Chen, Junhong; Chou, Kuo-Chih

    2016-01-01

    Fabrication of eletrochemical sensors based on wide bandgap compound semiconductors has attracted increasing interest in recent years. Here we report for the first time electrochemical nitrite sensors based on cubic silicon carbide (SiC) nanowires (NWs) with smooth surface and boron-doped cubic SiC NWs with fin-like structure. Multiple techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) were used to characterize SiC and boron-doped SiC NWs. As for the electrochemical behavior of both SiC NWs electrode, the cyclic voltammetric results show that both SiC electrodes exhibit wide potential window and excellent electrocatalytic activity toward nitrite oxidation. Differential pulse voltammetry (DPV) determination reveals that there exists a good linear relationship between the oxidation peak current and the concentration in the range of 50-15000 μmoL L(-1) (cubic SiC NWs) and 5-8000 μmoL L(-1) (B-doped cubic SiC NWs) with the detection limitation of 5 and 0.5 μmoL L(-1) respectively. Compared with previously reported results, both as-prepared nitrite sensors exhibit wider linear response range with comparable high sensitivity, high stability and reproducibility. PMID:27109361

  2. Homogeneous electrochemical detection of hippuric acid in urine based on the osmium-antigen conjugate.

    PubMed

    Jeon, Won-Yong; Choi, Young-Bong; Kim, Hyug-Han

    2013-07-22

    A homogeneous electrochemical immunoassay is based on the interaction of osmium-antigen conjugate with its antibody. The novelty presented herein is the direct conjugation of the osmium complex to a small antigen and the application of the quantitative analysis of the antigen and its antibody as the electrical signal for homogeneous immunoassay. The small antigen chosen is hippuric acid (HA), a major urinary metabolite in toluene-exposed humans. As a redox mediator, [Os(4,4'-dimethoxy-2,2'-bipyridine)2(4-aminomethylpyridine-HA)Cl](+/2+) (Os-HA antigen) has been synthesized and characterized on screen-printed carbon electrodes. The synthesized Os-HA antigen shows reversible redox peaks at E(½)=0.056 V versus Ag/AgCl. The homogeneous competitive immunoassay relies on the interaction between Os-HA antigen conjugate and free antigen to its antibody, which can generate electrical signals linearly proportional to the free antigen monitored by cyclic voltammetry and differential pulse voltammetry in the range of 10 μg mL(-1) to 5.12 mg mL(-1). The cutoff concentration of HA in urine samples is 2.0 mg mL(-1), so the method can be used to develop a HA immunosensor. Moreover, the proposed homogeneous electrochemical immunoassay method can be applied to detect low concentrations of small antigens found in the healthcare area.

  3. Bare and boron-doped cubic silicon carbide nanowires for electrochemical detection of nitrite sensitively

    NASA Astrophysics Data System (ADS)

    Yang, Tao; Zhang, Liqin; Hou, Xinmei; Chen, Junhong; Chou, Kuo-Chih

    2016-04-01

    Fabrication of eletrochemical sensors based on wide bandgap compound semiconductors has attracted increasing interest in recent years. Here we report for the first time electrochemical nitrite sensors based on cubic silicon carbide (SiC) nanowires (NWs) with smooth surface and boron-doped cubic SiC NWs with fin-like structure. Multiple techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) were used to characterize SiC and boron-doped SiC NWs. As for the electrochemical behavior of both SiC NWs electrode, the cyclic voltammetric results show that both SiC electrodes exhibit wide potential window and excellent electrocatalytic activity toward nitrite oxidation. Differential pulse voltammetry (DPV) determination reveals that there exists a good linear relationship between the oxidation peak current and the concentration in the range of 50–15000 μmoL L‑1 (cubic SiC NWs) and 5–8000 μmoL L‑1 (B-doped cubic SiC NWs) with the detection limitation of 5 and 0.5 μmoL L‑1 respectively. Compared with previously reported results, both as-prepared nitrite sensors exhibit wider linear response range with comparable high sensitivity, high stability and reproducibility.

  4. Electrochemical detection of a single cytomegalovirus at an ultramicroelectrode and its antibody anchoring

    PubMed Central

    Dick, Jeffrey E.; Hilterbrand, Adam T.; Boika, Aliaksei; Upton, Jason W.; Bard, Allen J.

    2015-01-01

    We report observations of stochastic collisions of murine cytomegalovirus (MCMV) on ultramicroelectrodes (UMEs), extending the observation of discrete collision events on UMEs to biologically relevant analytes. Adsorption of an antibody specific for a virion surface glycoprotein allowed differentiation of MCMV from MCMV bound by antibody from the collision frequency decrease and current magnitudes in the electrochemical collision experiments, which shows the efficacy of the method to size viral samples. To add selectivity to the technique, interactions between MCMV, a glycoprotein-specific primary antibody to MCMV, and polystyrene bead “anchors,” which were functionalized with a secondary antibody specific to the Fc region of the primary antibody, were used to affect virus mobility. Bead aggregation was observed, and the extent of aggregation was measured using the electrochemical collision technique. Scanning electron microscopy and optical microscopy further supported aggregate shape and extent of aggregation with and without MCMV. This work extends the field of collisions to biologically relevant antigens and provides a novel foundation upon which qualitative sensor technology might be built for selective detection of viruses and other biologically relevant analytes. PMID:25870261

  5. Electrochemical detection of Francisella tularensis genomic DNA using solid-phase recombinase polymerase amplification.

    PubMed

    del Río, Jonathan Sabaté; Yehia Adly, Nouran; Acero-Sánchez, Josep Lluis; Henry, Olivier Y F; O'Sullivan, Ciara K

    2014-04-15

    Solid-phase isothermal DNA amplification was performed exploiting the homology protein recombinase A (recA). The system was primarily tested on maleimide activated microtitre plates as a proof-of-concept and later translated to an electrochemical platform. In both cases, forward primer for Francisella tularensis holarctica genomic DNA was surface immobilised via a thiol or an amino moiety and then elongated during the recA mediated amplification, carried out in the presence of specific target sequence and reverse primers. The formation of the subsequent surface tethered amplicons was either colorimetrically or electrochemically monitored using a horseradish peroxidase (HRP)-labelled DNA secondary probe complementary to the elongated strand. The amplification time was optimised to amplify even low amounts of DNA copies in less than an hour at a constant temperature of 37°C, achieving a limit of detection of 1.3×10(-13) M (4×10(6) copies in 50 μL) for the colorimetric assay and 3.3×10(-14) M (2×10(5) copies in 10 μL) for the chronoamperometric assay. The system was demonstrated to be highly specific with negligible cross-reactivity with non-complementary targets or primers.

  6. Electrochemically reduced graphene oxide-modified screen-printed carbon electrodes for a simple and highly sensitive electrochemical detection of synthetic colorants in beverages.

    PubMed

    Jampasa, Sakda; Siangproh, Weena; Duangmal, Kiattisak; Chailapakul, Orawon

    2016-11-01

    A simple and highly sensitive electrochemical sensor based on an electrochemically reduced graphene oxide-modified screen-printed carbon electrode (ERGO-SPCE) for the simultaneous determination of sunset yellow (SY) and tartrazine (TZ) was proposed. An ERGO film was coated onto the electrode surface using a cyclic voltammetric method and then characterized by scanning electron microscopy (SEM). In 0.1M phosphate buffer at a pH of 6, the two oxidation peaks of SY and TZ appeared separately at 0.41 and 0.70V, respectively. Surprisingly, the electrochemical response remarkably increased approximately 90- and 20-fold for SY and TZ, respectively, using the modified electrode in comparison to the unmodified electrode. The calibration curves exhibited linear ranges from 0.01 to 20.0µM for SY and from 0.02 to 20.0µM for TZ. The limits of detection were found to be 0.50 and 4.50nM (at S/N=3) for SY and TZ, respectively. Furthermore, this detection platform provided very high selectivity for the measurement of both colorants. This electrochemical sensor was successfully applied to determine the amount of SY and TZ in commercial beverages. Comparison of the results obtained from this proposed method to those obtained by an in-house standard technique proved that this developed method has good agreement in terms of accuracy for practical applications. This sensor offers an inexpensive, rapid and sensitive determination. The proposed system is therefore suitable for routine analysis and should be an alternative method for the analysis of food colorants.

  7. Electrochemically reduced graphene oxide-modified screen-printed carbon electrodes for a simple and highly sensitive electrochemical detection of synthetic colorants in beverages.

    PubMed

    Jampasa, Sakda; Siangproh, Weena; Duangmal, Kiattisak; Chailapakul, Orawon

    2016-11-01

    A simple and highly sensitive electrochemical sensor based on an electrochemically reduced graphene oxide-modified screen-printed carbon electrode (ERGO-SPCE) for the simultaneous determination of sunset yellow (SY) and tartrazine (TZ) was proposed. An ERGO film was coated onto the electrode surface using a cyclic voltammetric method and then characterized by scanning electron microscopy (SEM). In 0.1M phosphate buffer at a pH of 6, the two oxidation peaks of SY and TZ appeared separately at 0.41 and 0.70V, respectively. Surprisingly, the electrochemical response remarkably increased approximately 90- and 20-fold for SY and TZ, respectively, using the modified electrode in comparison to the unmodified electrode. The calibration curves exhibited linear ranges from 0.01 to 20.0µM for SY and from 0.02 to 20.0µM for TZ. The limits of detection were found to be 0.50 and 4.50nM (at S/N=3) for SY and TZ, respectively. Furthermore, this detection platform provided very high selectivity for the measurement of both colorants. This electrochemical sensor was successfully applied to determine the amount of SY and TZ in commercial beverages. Comparison of the results obtained from this proposed method to those obtained by an in-house standard technique proved that this developed method has good agreement in terms of accuracy for practical applications. This sensor offers an inexpensive, rapid and sensitive determination. The proposed system is therefore suitable for routine analysis and should be an alternative method for the analysis of food colorants. PMID:27591594

  8. Sensitivity enhancement of an electrochemical immunosensor through the electrocatalysis of magnetic bead-supported non-enzymatic labels.

    PubMed

    Akter, Rashida; Kyun Rhee, Choong; Rahman, Md Aminur

    2014-04-15

    An ultrasensitive non-enzymatic electrochemical carcinoembryonic antigen (CEA) immunosensor was fabricated by the immobilization of a monoclonal CEA antibody (anti-CEA) on a protein A (PA) attached-gold nanoparticles (AuNPs)-deposited electrochemically prepared polydopamine film (e-PD/AuNPs). Magnetic beads (MB)-supported and CEA-conjugated multiple 3,3',5,5'-tetramethylbenzidine (TMB) was used as electrochemical labels. The detection was based on the measurements of the electrocatalyzed oxidation of ascorbic acid (AA) by the multiple TMB labels after competitive binding between MB/TMB-conjugated-CEA and free-CEA. The electrocatalyzed oxidation current of AA by TMB decreased with increasing concentration of the free-CEA as the amount of CEA/MB/TMB labels decreased at the immunosensor probe. The immunosensor surface was characterized using electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy, quartz crystal microbalance, and scanning electron microscopy techniques. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were used to monitor the electrocatalyzed response. The proposed immunosensor exhibited a wide linear dynamic range (1.0 pg/mL to 10.0 ng/mL), low detection limit (1.0±0.04 pg/mL), good selectivity, and long-time stability. It was successfully applied to various CEA spiked human serum samples for the detection of CEA.

  9. A nanoparticle label/immunochromatographic electrochemical biosensor for rapid and sensitive detection of prostate-specific antigen

    SciTech Connect

    Lin, Ying-Ying; Wang, Jun; Liu, Guodong; Wu, Hong; Wai, Chien M.; Lin, Yuehe

    2008-06-15

    We present a nanoparticle (NP) label/immunochromatographic electrochemical biosensor (IEB) for rapid and sensitive detection of prostate-specific antigen (PSA) in human serum. This IEB integrates the immunochromatographic strip with the electrochemical detector for transducing quantitative signals. The NP label, made of CdSe@ZnS, serves as a signal-amplifier vehicle. A sandwich immunoreaction was performed on the immunochromatographic strip. The captured NP labels in the test zone were determined by highly sensitive stripping voltammetric measurement of the dissolved metallic component (cadmium) with a disposable-screen-printed electrode, which is embedded underneath the membrane of the test zone. Experimental parameters (e.g., immunoreaction time, the amount of anti-PSA-NP conjugations applied) and electrochemical detection conditions (e.g., preconcentration potential and time) were optimized using this biosensor for PSA detection. The analytical performance of this biosensor was evaluated with serum PSA samples according to the “figure-of-merits” (e.g., dynamic range, reproducibility, and detection limit). The results were validated with enzyme-linked immunosorbent assay (ELISA) and show high consistency. It is found that this biosensor is very sensitive with the detection limit of 0.02 ng/mL PSA and is quite reproducible. This method is rapid, clinically accurate, and less expensive than other diagnosis tools for PSA; therefore, this IEB coupled with a portable electrochemical analyzer shows great promise for simple, sensitive, quantitative point-of-care testing of disease-related protein biomarkers.

  10. An integrated electrochemical device based on immunochromatographic test strip and enzyme labels for sensitive detection of disease-related biomarkers

    SciTech Connect

    Zou, Zhexiang; Wang, Jun; Wang, Hua; Li, Yao Q.; Lin, Yuehe

    2012-05-30

    A novel electrochemical biosensing device that integrates an immunochromatographic test strip and a screen-printed electrode (SPE) connected to a portable electrochemical analyzer was presented for rapid, sensitive, and quantitative detection of disease-related biomarker in human blood samples. The principle of the sensor is based on sandwich immunoreactions between a biomarker and a pair of its antibodies on the test strip, followed by highly sensitive square-wave voltammetry (SWV) detection. Horseradish peroxidase (HRP) was used as a signal reporter for electrochemical readout. Hepatitis B surface antigen (HBsAg) was employed as a model protein biomarker to demonstrate the analytical performance of the sensor in this study. Some critical parameters governing the performance of the sensor were investigated in detail. The sensor was further utilized to detect HBsAg in human plasma with an average recovery of 91.3%. In comparison, a colorimetric immunochromatographic test strip assay (ITSA) was also conducted. The result shows that the SWV detection in the electrochemical sensor is much more sensitive for the quantitative determination of HBsAg than the colorimetric detection, indicating that such a sensor is a promising platform for rapid and sensitive point-of-care testing/screening of disease-related biomarkers in a large population

  11. A graphene-based electrochemical competitive immunosensor for the sensitive detection of okadaic acid in shellfish

    NASA Astrophysics Data System (ADS)

    Eissa, Shimaa; Zourob, Mohammed

    2012-11-01

    A novel graphene-based voltammetric immunosensor for sensitive detection of okadaic acid (OA) was developed. A simple and efficient electrografting method was utilized to functionalize graphene-modified screen-printed carbon electrodes (GSPE) by the electrochemical reduction of in situ generated 4-carboxyphenyl diazonium salt in acidic aqueous solution. Next, the okadaic acid antibody was covalently immobilized on the carboxyphenyl modified graphene electrodes via carbodiimide chemistry. Square wave voltammetry (SWV) was used to investigate the stepwise assembly of the immunosensor. A competitive assay between OA and a fixed concentration of okadaic acid-ovalbumin conjugate (OA-OVA) for the immobilized antibodies was employed for the detection of okadaic acid. The decrease of the [Fe(CN)6]3-/4- reduction peak current in the square wave voltammetry for various concentrations of okadaic acid was used for establishing the calibration curve. A linear relationship between the SWV peak current difference and OA concentration was obtained up to ~5000 ng L-1. The developed immunosensor allowed a detection limit of 19 ng L-1 of OA in PBS buffer. The matrix effect studied with spiked shellfish tissue extracts showed a good percentage of recovery and the method was also validated with certified reference mussel samples.A novel graphene-based voltammetric immunosensor for sensitive detection of okadaic acid (OA) was developed. A simple and efficient electrografting method was utilized to functionalize graphene-modified screen-printed carbon electrodes (GSPE) by the electrochemical reduction of in situ generated 4-carboxyphenyl diazonium salt in acidic aqueous solution. Next, the okadaic acid antibody was covalently immobilized on the carboxyphenyl modified graphene electrodes via carbodiimide chemistry. Square wave voltammetry (SWV) was used to investigate the stepwise assembly of the immunosensor. A competitive assay between OA and a fixed concentration of okadaic acid

  12. Zepto-molar electrochemical detection of Brucella genome based on gold nanoribbons covered by gold nanoblooms

    PubMed Central

    Rahi, Amid; Sattarahmady, Naghmeh; Heli, Hossein

    2015-01-01

    Gold nanoribbons covered by gold nanoblooms were sonoelectrodeposited on a polycrystalline gold surface at −1800 mV (vs. AgCl) with the assistance of ultrasound and co-occurrence of the hydrogen evolution reaction. The nanostructure, as a transducer, was utilized to immobilize a Brucella-specific probe and fabrication of a genosensor, and the process of immobilization and hybridization was detected by electrochemical methods, using methylene blue as a redox marker. The proposed method for detection of the complementary sequence, sequences with base-mismatched (one-, two- and three-base mismatches), and the sequence of non-complementary sequence was assayed. The fabricated genosensor was evaluated for the assay of the bacteria in the cultured and human samples without polymerase chain reactions (PCR). The genosensor could detect the complementary sequence with a calibration sensitivity of 0.40 μA dm3 mol−1, a linear concentration range of 10 zmol dm−3 to 10 pmol dm−3, and a detection limit of 1.71 zmol dm−3. PMID:26657828

  13. Electrochemical detection of uric acid via uricase-immobilized graphene oxide.

    PubMed

    Omar, Muhamad Nadzmi; Salleh, Abu Bakar; Lim, Hong Ngee; Ahmad Tajudin, Asilah

    2016-09-15

    Measurement of the uric acid level in the body can be improved by biosensing with respect to the accuracy, sensitivity and time consumption. This study has reported the immobilization of uricase onto graphene oxide (GO) and its function for electrochemical detection of uric acid. Through chemical modification of GO using 1-ethyl-3-(dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHS) as cross-linking reagents, the enzyme activity of the immobilized uricase was much comparable to the free enzyme with 88% of the activity retained. The modified GO-uricase (GOU) was then subjected to electrocatalytic detection of uric acid (UA) via cyclic voltammetry (CV). For that reason, a glassy carbon electrode (GCE) was modified by adhering the GO along with the immobilized uricase to facilitate the redox reaction between the enzyme and the substrate. The modified GOU/GCE outperformed a bare electrode through the electrocatalytic activity with an amplified electrical signal for the detection of UA. The electrocatalytic response showed a linear dependence on the UA concentration ranging from 0.02 to 0.49 mM with a detection limit of 3.45 μM at 3σ/m. The resulting biosensor also exhibited a high selectivity towards UA in the presence of other interference as well as good reproducibility. PMID:27402177

  14. Electrochemical impedance immunosensor for rapid detection of stressed pathogenic Staphylococcus aureus bacteria.

    PubMed

    Bekir, Karima; Barhoumi, Houcine; Braiek, Mohamed; Chrouda, Amani; Zine, Nadia; Abid, Nabil; Maaref, Abdelrazek; Bakhrouf, Amina; Ouada, Hafedh Ben; Jaffrezic-Renault, Nicole; Mansour, Hedi Ben

    2015-10-01

    In this work, we report the adaptation of bacteria to stress conditions that induce instability of their cultural, morphological, and enzymatic characters, on which the identification of pathogenic bacteria is based. These can raise serious issues during the characterization of bacteria. The timely detection of pathogens is also a subject of great importance. For this reason, our objective is oriented towards developing an immunosensing system for rapid detection and quantification of Staphylococcus aureus. Polyclonal anti-S. aureus are immobilized onto modified gold electrode by self-assembled molecular monolayer (SAM) method. The electrochemical performances of the developed immunosensor were evaluated by impedance spectroscopy through the monitoring of the charge transfer resistance at the modified solid/liquid interface using ferri-/ferrocyanide as redox probe. The developed immunosensor was applied to detect stressed and resuscitate bacteria. As a result, a stable and reproducible immunosensor with sensitivity of 15 kΩ/decade and a detection limit of 10 CFU/mL was obtained for the S. aureus concentrations ranging from 10(1) to 10(7) CFU/mL. A low deviation in the immunosensor response (±10 %) was signed when it is exposed to stressed and not stressed bacteria.

  15. Zepto-molar electrochemical detection of Brucella genome based on gold nanoribbons covered by gold nanoblooms.

    PubMed

    Rahi, Amid; Sattarahmady, Naghmeh; Heli, Hossein

    2015-01-01

    Gold nanoribbons covered by gold nanoblooms were sonoelectrodeposited on a polycrystalline gold surface at -1800 mV (vs. AgCl) with the assistance of ultrasound and co-occurrence of the hydrogen evolution reaction. The nanostructure, as a transducer, was utilized to immobilize a Brucella-specific probe and fabrication of a genosensor, and the process of immobilization and hybridization was detected by electrochemical methods, using methylene blue as a redox marker. The proposed method for detection of the complementary sequence, sequences with base-mismatched (one-, two- and three-base mismatches), and the sequence of non-complementary sequence was assayed. The fabricated genosensor was evaluated for the assay of the bacteria in the cultured and human samples without polymerase chain reactions (PCR). The genosensor could detect the complementary sequence with a calibration sensitivity of 0.40 μA dm(3) mol(-1), a linear concentration range of 10 zmol dm(-3) to 10 pmol dm(-3), and a detection limit of 1.71 zmol dm(-3). PMID:26657828

  16. Zepto-molar electrochemical detection of Brucella genome based on gold nanoribbons covered by gold nanoblooms

    NASA Astrophysics Data System (ADS)

    Rahi, Amid; Sattarahmady, Naghmeh; Heli, Hossein

    2015-12-01

    Gold nanoribbons covered by gold nanoblooms were sonoelectrodeposited on a polycrystalline gold surface at -1800 mV (vs. AgCl) with the assistance of ultrasound and co-occurrence of the hydrogen evolution reaction. The nanostructure, as a transducer, was utilized to immobilize a Brucella-specific probe and fabrication of a genosensor, and the process of immobilization and hybridization was detected by electrochemical methods, using methylene blue as a redox marker. The proposed method for detection of the complementary sequence, sequences with base-mismatched (one-, two- and three-base mismatches), and the sequence of non-complementary sequence was assayed. The fabricated genosensor was evaluated for the assay of the bacteria in the cultured and human samples without polymerase chain reactions (PCR). The genosensor could detect the complementary sequence with a calibration sensitivity of 0.40 μA dm3 mol-1, a linear concentration range of 10 zmol dm-3 to 10 pmol dm-3, and a detection limit of 1.71 zmol dm-3.

  17. Determination of xanthomegnin in grains and animal feeds by liquid chromatography with electrochemical detection.

    PubMed

    Carman, A S; Kuan, S S; Francis, O J; Ware, G M; Luedtke, A E

    1984-01-01

    A sensitive, highly selective liquid chromatographic (LC) method is described which uses electrochemical (EC) reduction of the analyte in the determinative step. The method is capable of determining xanthomegnin in mixed animal feeds and grains at levels ranging from 15 to 1200 ng/g. The method can detect as little as 0.5 ng xanthomegnin injected on the LC column. Xanthomegnin is extracted with chloroform and 0.1M phosphoric acid. An aliquot of the crude extract is purified by silica gel column chromatography using a Sep-Pak silica gel cartridge. A novel feature of the method is that xanthomegnin is "backed off" the column by reversing the flow of the eluant through the column. LC is then used to separate xanthomegnin from other interfering substances. Xanthomegnin is detected by EC reduction at -0.16 V. Recoveries of xanthomegnin added to samples at levels ranging from 15 to 1200 ng/g averaged 79% with a coefficient of variation of 7.9%. Results also demonstrate that this LC system can separate the related metabolites viomellein and rubrosulphin from each other and from xanthomegnin and that the same EC detection system can be used to detect these metabolites.

  18. Electrochemical biosensor for Ni(2+) detection based on a DNAzyme-CdSe nanocomposite.

    PubMed

    Yang, Ying; Yuan, Zheng; Liu, Xing-Pei; Liu, Qiao; Mao, Chang-Jie; Niu, He-Lin; Jin, Bao-Kang; Zhang, Sheng-Yi

    2016-03-15

    The detection and speciation analysis of metal-ion is very important for environmental monitoring. A novel electrochemical biosensor for Nickel(II) detection based on a DNAzyme-CdSe nanocomposite was developed. We firstly hybridized with capture probe (DNA1) and sequentially with DNA (DNA2) on the gold electrode. Then CdSe QDs were incorporated the specific recognition of DNA2 by covalent assembling. Upon addition of nickel ion into the above system, the substrate strand of the immobilized DNAzyme was catalytically cleaved by target Ni(2+), resulting in disassociation of the shorter DNA fragments containing CdSe QDs. The remaining CdSe QDs on the electrode surface detected by differential pulse anodic stripping voltammetry (DPASV). Under optimal conditions, the as-prepared sensor exhibited high sensitivity and fast response to Ni(2+) with the linear range from 20 nM to 0.2mM and a low detection limit of 6.67 nM. The prepared biosensor also shows good stability and good reproducibility and high selectivity toward target Ni(2+) against other metal ions because of highly specific Ni(2+)-dependent DNAzyme. Thus, our strategy has a good potential in the environment surveys. PMID:26385732

  19. Molecularly imprinted polymer based electrochemical detection of L-cysteine at carbon paste electrode.

    PubMed

    Aswini, K K; Vinu Mohan, A M; Biju, V M

    2014-04-01

    A methacrylic acid (MAA) based molecularly imprinted polymer (MIP) modified carbon paste electrode (CPE) was developed for electrochemical detection of L-cysteine (Cys). Characterisation of MIP was done with FTIR and the modified electrode with cyclic voltammetry (CV) and differential pulse voltammetry (DPV). CV, DPV and impedance analysis demonstrated that the modified electrode is responsive towards the target molecule. The optimum percentage composition of MIP for MIP/CPE and the effect of pH towards the electrode response for Cys were studied. The detection of Cys in the range of 2×10(-8) to 18×10(-8)M at MIP/CPE was monitored by DPV with a limit of detection of 9.6nM and R(2) of 0.9974. Also, various physiological interferents such as ascorbic acid, L-tryptophan, D-glucose, D-cysteine and L-cysteine were found to have little effect on DPV response at MIP/CPE. The utility of the electrode was proved by the effective detection of Cys from tap water and human blood plasma samples with reproducible results.

  20. Enzymatically amplified electrochemical detection for lipopolysaccharide using ferrocene-attached polymyxin B and its analogue.

    PubMed

    Iijima, Seiichiro; Kato, Dai; Yabuki, Soichi; Niwa, Osamu; Mizutani, Fumio

    2011-01-15

    Ferrocene-attached polymyxin B (PMB-Fc) was prepared by the reaction of polymyxin B with ferrocenoyl chloride in a toluene/pyridine mixture. An electrochemical detection of lipopolysaccharide (LPS) was carried out using a combination of PMB-Fc and an enzyme-modified electrode constructed from a glassy carbon electrode modified with a bovine serum albumin membrane containing glucose oxidase. The ferrocene units of the PMB-Fc molecules were oxidized on the electrode, and then reduced to the original neutral form by a glucose oxidase-catalyzed reaction in the presence of D-glucose. The consumption/regeneration cycle for PMB-Fc resulted in a chemically amplified current response. The current response for PMB-Fc decreased in association with its complexation with LPS, and the magnitude of this current decrease caused by LPS was also amplified by the recycling process. The enzyme-modified electrode exhibited a rapid response of 5 min for LPS with the detection limit as low as 50 ng ml(-1). Further, the addition of D-solbitol or poly(vinyl alcohol) of high concentration over 1 mg ml(-1) substantially induced no response, and three kinds of LPS from different strains exhibited similar magnitudes of current response for the same concentrations; these results suggest the advantages of this detection system for practical applications. Ferrocene-attached colistin, an analogue of PMB-Fc, was also effective for the LPS detection using the glucose oxidase-modified electrode. PMID:20947333

  1. A Graphene and Aptamer Based Liquid Gated FET-Like Electrochemical Biosensor to Detect Adenosine Triphosphate.

    PubMed

    Mukherjee, Souvik; Meshik, Xenia; Choi, Min; Farid, Sidra; Datta, Debopam; Lan, Yi; Poduri, Shripriya; Sarkar, Ketaki; Baterdene, Undarmaa; Huang, Ching-En; Wang, Yung Yu; Burke, Peter; Dutta, Mitra; Stroscio, Michael A

    2015-12-01

    Here we report successful demonstration of a FET-like electrochemical nano-biosensor to accurately detect ultralow concentrations of adenosine triphosphate. As a 2D material, graphene is a promising candidate due to its large surface area, biocompatibility, and demonstrated surface binding chemistries and has been employed as the conducting channel. A short 20-base DNA aptamer is used as the sensing element to ensure that the interaction between the analyte and the aptamer occurs within the Debye length of the electrolyte (PBS). Significant increase in the drain current with progressive addition of ATP is observed whereas for control experiments, no distinct change in the drain current occurs. The sensor is found to be highly sensitive in the nanomolar (nM) to micromolar ( μM) range with a high sensitivity of 2.55 μA (mM) (-1), a detection limit as low as 10 pM, and it has potential application in medical and biological settings to detect low traces of ATP. This simplistic design strategy can be further extended to efficiently detect a broad range of other target analytes.

  2. Aptamer-based electrochemical detection of picomolar platelet-derived growth factor directly in blood serum.

    PubMed

    Lai, Rebecca Y; Plaxco, Kevin W; Heeger, Alan J

    2007-01-01

    We report an electrochemical, aptamer-based (E-AB) sensor for the detection of platelet-derived growth factor (PDGF) directly in blood serum. The E-AB approach employs alternating current voltammetry to monitor target-induced folding in a methylene blue-modified, PDGF-binding aptamer. The sensor is sensitive, highly selective, and essentially reagentless: we readily detect the BB variant of PDGF at 1 nM directly in undiluted, unmodified blood serum and at 50 pM (1.25 ng/mL) in serum-diluted 2-fold with aqueous buffer. The sensitivity and selectivity achieved by this sensor match or significantly exceed those of the best analogous optical approaches. For example, the detection limit attained in 50% serum is achieved against a >25 million-fold excess of contaminating blood proteins and represents a 4 order of magnitude improvement over the most sensitive optical PDGF aptasensor reported to date. Moreover, the E-AB sensor combines these promising attributes in a platform that is reusable, label-free, and electronic. Given these advantages, E-AB sensors appear well suited for implementation in portable microdevices directed at the direct detection of proteins and small molecules in complex, largely unprocessed clinical samples.

  3. Detection of greenhouse gas precursors from diesel engines using electrochemical and photoacoustic sensors.

    PubMed

    Mothé, Geórgia; Castro, Maria; Sthel, Marcelo; Lima, Guilherme; Brasil, Laisa; Campos, Layse; Rocha, Aline; Vargas, Helion

    2010-01-01

    Atmospheric pollution is one of the worst threats to modern society. The consequences derived from different forms of atmospheric pollution vary from the local to the global scale, with deep impacts on climate, environment and human health. Several gaseous pollutants, even when present in trace concentrations, play a fundamental role in important processes that occur in atmosphere. Phenomena such as global warming, photochemical smog formation, acid rain and the depletion of the stratospheric ozone layer are strongly related to the increased concentration of certain gaseous species in the atmosphere. The transport sector significantly produces atmospheric pollution, mainly when diesel oil is used as fuel. Therefore, new methodologies based on selective and sensitive gas detection schemes must be developed in order to detect and monitor pollutant gases from this source. In this work, CO(2) Laser Photoacoustic Spectroscopy was used to evaluate ethylene emissions and electrochemical analyzers were used to evaluate the emissions of CO, NO(x) and SO(2) from the exhaust of diesel powered vehicles (rural diesel with 5% of biodiesel, in this paper called only diesel) at different engine rotation speeds. Concentrations in the range 6 to 45 ppmV for ethylene, 109 to 1,231 ppmV for carbon monoxide, 75 to 868 ppmV for nitrogen oxides and 3 to 354 ppmV for sulfur dioxide were obtained. The results indicate that the detection techniques used were sufficiently selective and sensitive to detect the gaseous species mentioned above in the ppmV range.

  4. Detection of Greenhouse Gas Precursors from Diesel Engines Using Electrochemical and Photoacoustic Sensors

    PubMed Central

    Mothé, Geórgia; Castro, Maria; Sthel, Marcelo; Lima, Guilherme; Brasil, Laisa; Campos, Layse; Rocha, Aline; Vargas, Helion

    2010-01-01

    Atmospheric pollution is one of the worst threats to modern society. The consequences derived from different forms of atmospheric pollution vary from the local to the global scale, with deep impacts on climate, environment and human health. Several gaseous pollutants, even when present in trace concentrations, play a fundamental role in important processes that occur in atmosphere. Phenomena such as global warming, photochemical smog formation, acid rain and the depletion of the stratospheric ozone layer are strongly related to the increased concentration of certain gaseous species in the atmosphere. The transport sector significantly produces atmospheric pollution, mainly when diesel oil is used as fuel. Therefore, new methodologies based on selective and sensitive gas detection schemes must be developed in order to detect and monitor pollutant gases from this source. In this work, CO2 Laser Photoacoustic Spectroscopy was used to evaluate ethylene emissions and electrochemical analyzers were used to evaluate the emissions of CO, NOx and SO2 from the exhaust of diesel powered vehicles (rural diesel with 5% of biodiesel, in this paper called only diesel) at different engine rotation speeds. Concentrations in the range 6 to 45 ppmV for ethylene, 109 to 1,231 ppmV for carbon monoxide, 75 to 868 ppmV for nitrogen oxides and 3 to 354 ppmV for sulfur dioxide were obtained. The results indicate that the detection techniques used were sufficiently selective and sensitive to detect the gaseous species mentioned above in the ppmV range. PMID:22163437

  5. Zepto-molar electrochemical detection of Brucella genome based on gold nanoribbons covered by gold nanoblooms.

    PubMed

    Rahi, Amid; Sattarahmady, Naghmeh; Heli, Hossein

    2015-12-14

    Gold nanoribbons covered by gold nanoblooms were sonoelectrodeposited on a polycrystalline gold surface at -1800 mV (vs. AgCl) with the assistance of ultrasound and co-occurrence of the hydrogen evolution reaction. The nanostructure, as a transducer, was utilized to immobilize a Brucella-specific probe and fabrication of a genosensor, and the process of immobilization and hybridization was detected by electrochemical methods, using methylene blue as a redox marker. The proposed method for detection of the complementary sequence, sequences with base-mismatched (one-, two- and three-base mismatches), and the sequence of non-complementary sequence was assayed. The fabricated genosensor was evaluated for the assay of the bacteria in the cultured and human samples without polymerase chain reactions (PCR). The genosensor could detect the complementary sequence with a calibration sensitivity of 0.40 μA dm(3) mol(-1), a linear concentration range of 10 zmol dm(-3) to 10 pmol dm(-3), and a detection limit of 1.71 zmol dm(-3).

  6. Quantification of ethanol in plasma by electrochemical detection with an unmodified screen printed carbon electrode

    PubMed Central

    Tian, Gang; Zhang, Xiao-Qing; Zhu, Ming-Song; Zhang, Zhong; Shi, Zheng-Hu; Ding, Min

    2016-01-01

    Simple, rapid and accurate detection of ethanol concentration in blood is very crucial in the diagnosis and management of potential acute ethanol intoxication patients. A novel electrochemical detection method was developed for the quantification of ethanol in human plasma with disposable unmodified screen-printed carbon electrode (SPCE) without sample preparation procedure. Ethanol was detected indirectly by the reaction product of ethanol dehydrogenase (ADH) and cofactor nicotinamide adenine dinucleotide (NAD+). Method validation indicated good quantitation precisions with intra-day and inter-day relative standard deviations of ≤9.4% and 8.0%, respectively. Ethanol concentration in plasma is linear ranging from 0.10 to 3.20 mg/mL, and the detection limit is 40.0 μg/mL (S/N > 3). The method shows satisfactory correlation with the reference method of headspace gas chromatography in twenty human plasma samples (correlation coefficient 0.9311). The proposed method could be applied to diagnose acute ethanol toxicity or ethanol-related death. PMID:27006081

  7. Electrochemical Biosensor for Rapid and Sensitive Detection of Magnetically Extracted Bacterial Pathogens

    PubMed Central

    Setterington, Emma B.; Alocilja, Evangelyn C.

    2012-01-01

    Biological defense and security applications demand rapid, sensitive detection of bacterial pathogens. This work presents a novel qualitative electrochemical detection technique which is applied to two representative bacterial pathogens, Bacillus cereus (as a surrogate for B. anthracis) and Escherichia coli O157:H7, resulting in detection limits of 40 CFU/mL and 6 CFU/mL, respectively, from pure culture. Cyclic voltammetry is combined with immunomagnetic separation in a rapid method requiring approximately 1 h for presumptive positive/negative results. An immunofunctionalized magnetic/polyaniline core/shell nano-particle (c/sNP) is employed to extract target cells from the sample solution and magnetically position them on a screen-printed carbon electrode (SPCE) sensor. The presence of target cells significantly inhibits current flow between the electrically active c/sNPs and SPCE. This method has the potential to be adapted for a wide variety of target organisms and sample matrices, and to become a fully portable system for routine monitoring or emergency detection of bacterial pathogens. PMID:25585629

  8. Microfluidic Electrochemical Immunoarray for Ultrasensitive Detection of Two Cancer Biomarker Proteins in Serum

    PubMed Central

    Chikkaveeraiah, Bhaskara V.; Mani, Vigneshwaran; Patel, Vyomesh; Gutkind, J. Silvio; Rusling, James F.

    2011-01-01

    A microfluidic electrochemical immunoassay system for multiplexed detection of protein cancer biomarkers was fabricated using a molded polydimethylsiloxane channel and routine machined parts interfaced with a pump and sample injector. Using off-line capture of analytes by heavily-enzyme-labeled 1 μm superparamagnetic particle (MP)-antibody bioconjugates and capture antibodies attached to an 8-electrode measuring chip, simultaneous detection of cancer biomarker proteins prostate specific antigen (PSA) and interleukin-6 (IL-6) in serum was achieved at sub-pg mL−1 levels. MPs were conjugated with ~90,000 antibodies and ~200,000 horseradish peroxidase (HRP) labels to provide efficient off-line capture and high sensitivity. Measuring electrodes feature a layer of 5 nm glutathione-decorated gold nanoparticles to attach antibodies that capture MP-analyte bioconjugates. Detection limits of 0.23 pg mL−1 for PSA and 0.30 pg mL−1 for IL-6 were obtained in diluted serum mixtures. PSA and IL-6 biomarkers were measured in serum of prostate cancer patients in total assay time 1.15 h and sensor array results gave excellent correlation with standard enzyme-linked immunosorbent assays (ELISA). These microfluidic immunosensors employing nanostructured surfaces and off-line analyte capture with heavily-labeled paramagnetic particles hold great promise for accurate, sensitive multiplexed detection of diagnostic cancer biomarkers. PMID:21632234

  9. Electrochemical Detection of Fluoroquinolone Antibiotics in Milk Using a Magneto Immunosensor

    PubMed Central

    Pinacho, Daniel G.; Sánchez-Baeza, Francisco; Pividori, María-Isabel; Marco, María-Pilar

    2014-01-01

    An amperometric magneto-immunosensor (AMIS) for the detection of residues of fluoroquinolone antibiotics in milk samples is described for the first time. The immunosensor presented combines magnetic beads biomodified with an antibody with a broad recognition profile of fluoroquinolones, a haptenized enzyme and a magnetic graphite–epoxy composite (m-GEC) electrode. After the immunochemical reaction with specific enzyme tracer, the antibody biomodified magnetic beads are easily captured by an electrode made of graphite-epoxy composite containing a magnet, which also acts as transducer for the electrochemical detection. In spite of the complexity of milk, the use of magnetic beads allows elimination of potential interferences caused by the matrix components; hence the AMIS could perform quantitative measurements, directly in these samples, without any additional sample cleanup or extraction step. The immunosensor is able to detect up to seven different fluoroquinolones far below the MRLs defined by the UE for milk; for example ciprofloxacin is detected directly in milk with an IC50 of 0.74 μg/L and a LOD of 0.009 μg/L. This strategy offers great promise for rapid, simple, cost-effective, and on-site analysis fluoroquinolones in complex samples. PMID:25171120

  10. Ultrasensitive Electrochemical Biosensor for HIV Gene Detection Based on Graphene Stabilized Gold Nanoclusters with Exonuclease Amplification.

    PubMed

    Wang, Yijia; Bai, Xiaoning; Wen, Wei; Zhang, Xiuhua; Wang, Shengfu

    2015-08-26

    Because human immunodeficiency virus (HIV) has been one of the most terrible viruses in recent decades, early diagnosis of the HIV gene is of great importance for all scientists around the world. In our work, we developed a novel electrochemical biosensor based on one-step ultrasonic synthesized graphene stabilized gold nanocluster (GR/AuNC) modified glassy carbon electrode (GCE) with an exonuclease III (Exo III)-assisted target recycling amplification strategy for the detection of HIV DNA. It is the first time that GR/AuNCs have been used as biosensor platform and aptamer with cytosine-rich base set as capture probe to construct the biosensor. With the combination of cytosine-rich capture probe, good conductivity and high surfaces of GR/AuNCs, and Exo III-assisted target recycling amplification, we realized high sensitivity and good selectivity detection of target HIV DNA with a detection limit of 30 aM (S/N = 3). Furthermore, the proposed biosensor has a promising potential application for target detection in human serum analysis.

  11. An electrochemical method for making enzyme microsensors. Application to the detection of dopamine and glutamate.

    PubMed

    Cosnier, S; Innocent, C; Allien, L; Poitry, S; Tsacopoulos, M

    1997-03-01

    A novel method of microbiosensor fabrication is described. It is based on the electrochemical polymerization of an enzyme-amphiphilic pyrroleammonium solution on the surface of a microelectrode in the absence of supporting electrolyte. By trapping glutamate oxidase (GMO) or polyphenol oxidase (PPO) in such polypyrrole films, we made microbiosensors for the amperometric determination of glutamate or dopamine, respectively. The response of the GMO microelectrode to glutamate was based on the amperometric detection of the enzymically generated hydrogen peroxide at 0.6 V vs SCE. The detection limit and sensitivity of this microbiosensor were 1 μM and 32 mA M(-1) cm(-2), respectively. The response of the PPO microelectrode to dopamine was based on the amperometric detection of the enzymically generated quinoid product at -0.2 V. The calibration range for dopamine measurement was 5 × 10(-8)-8 × 10(-5) M and the detection limit and sensitivity were 5 × 10(-8) M and 59 mA M(-1) cm(-2), respectively.

  12. Modified Electrodes Used for Electrochemical Detection of Metal Ions in Environmental Analysis

    PubMed Central

    March, Gregory; Nguyen, Tuan Dung; Piro, Benoit

    2015-01-01

    Heavy metal pollution is one of the most serious environmental problems, and regulations are becoming stricter. Many efforts have been made to develop sensors for monitoring heavy metals in the environment. This review aims at presenting the different label-free strategies used to develop electrochemical sensors for the detection of heavy metals such as lead, cadmium, mercury, arsenic etc. The first part of this review will be dedicated to stripping voltammetry techniques, on unmodified electrodes (mercury, bismuth or noble metals in the bulk form), or electrodes modified at their surface by nanoparticles, nanostructures (CNT, graphene) or other innovative materials such as boron-doped diamond. The second part will be dedicated to chemically modified electrodes especially those with conducting polymers. The last part of this review will focus on bio-modified electrodes. Special attention will be paid to strategies using biomolecules (DNA, peptide or proteins), enzymes or whole cells. PMID:25938789

  13. Integrating Paper Chromatography with Electrochemical Detection for the Trace Analysis of TNT in Soil

    PubMed Central

    Ryan, Patrick; Zabetakis, Daniel; Stenger, David A.; Trammell, Scott A.

    2015-01-01

    We report on the development of an electrochemical probe for the trace analysis of 2,4,6-trinitrotoluene (TNT) in soil samples. The probe is a combination of graphite electrodes, filter paper, with ethylene glycol and choline chloride as the solvent/electrolyte. Square wave chromatovoltammograms show the probes have a sensitivity for TNT of 0.75 nA/ng and a limit of detection of 100 ng. In addition, by taking advantage of the inherent paper chromatography step, TNT can be separated in both time and cathodic peak potential from 4-amino-dinitrotolene co-spotted on the probe or in soil samples with the presence of methyl parathion as a possible interferent. PMID:26184223

  14. Electrochemically amplified molecular beacon biosensor for ultrasensitive DNA sequence-specific detection of Legionella sp.

    PubMed

    Rai, Varun; Nyine, Yin Thu; Hapuarachchi, Hapuarachchige C; Yap, Hooi Ming; Ng, Lee Ching; Toh, Chee-Seng

    2012-02-15

    An electrochemically amplified molecular beacon (EAMB) biosensor is constructed using thiolated hairpin DNA-ferrocene probes on gold electrode. The switching from "on" to "off" states of individual probes in the presence of complementary DNA target influences the electrode potential, besides the current, owing to changes in surface density of the electroactive hairpin DNA-ferrocene probes. The EAMB biosensor demonstrates linear range over 8 orders of magnitude with ultrasensitive detection limit of 2.3 × 10(-14)M for the quantification of a 21-mer DNA sequence. Its applicability is tested against PCR amplicons derived from genomic DNA of live Legionella pneumophila. Excellent specificity down to one and three nucleotides mismatches in another strain of L. pneumophila and a different bacterium species, respectively, is demonstrated.

  15. Small-volume multiparametric electrochemical detection at low cost polymeric devices featuring nanoelectrodes

    NASA Astrophysics Data System (ADS)

    Kitsara, Maria; Cirera, Josep Maria; Aller-Pellitero, Miguel; Sabaté, Neus; Punter, Jaume; Colomer-Farrarons, Jordi; Miribel-Català, Pere; del Campo, F. Javier

    2015-06-01

    The development of a low-cost multiparametric platform for enzymatic electrochemical biosensing that can be integrated in a disposable, energy autonomous analytical device is the target of the current work. We propose a technology to fabricate nano-electrodes and ultimately biosensors on flexible polymeric-based substrates (cyclo olefin polymer, and polyimide) using standard microfabrication (step and repeat lithography and lift-off) and rapid prototyping techniques (blade cutting). Our target is towards the fabrication of a miniaturized prototype that can work with small sample volumes in the range of 5-10μL without the need for external pumps for sample loading and handling. This device can be used for the simultaneous detection of metabolites such as glucose, cholesterol and triglycerides for the early diagnosis of diabetes.

  16. A repeatable assembling and disassembling electrochemical aptamer cytosensor for ultrasensitive and highly selective detection of human liver cancer cells.

    PubMed

    Sun, Duanping; Lu, Jing; Chen, Zuanguang; Yu, Yanyan; Mo, Manni

    2015-07-23

    In this work, a repeatable assembling and disassembling electrochemical aptamer cytosensor was proposed for the sensitive detection of human liver hepatocellular carcinoma cells (HepG2) based on a dual recognition and signal amplification strategy. A high-affinity thiolated TLS11a aptamer, covalently attached to a gold electrode through Au-thiol interactions, was adopted to recognize and capture the target HepG2 cells. Meanwhile, the G-quadruplex/hemin/aptamer and horseradish peroxidase (HRP) modified gold nanoparticles (G-quadruplex/hemin/aptamer-AuNPs-HRP) nanoprobe was designed. It could be used for electrochemical cytosensing with specific recognition and enzymatic signal amplification of HRP and G-quadruplex/hemin HRP-mimicking DNAzyme. With the nanoprobes as recognizing probes, the HepG2 cancer cells were captured to fabricate an aptamer-cell-nanoprobes sandwich-like superstructure on a gold electrode surface. The proposed electrochemical cytosensor delivered a wide detection range from 1×10(2) to 1×10(7) cells mL(-1) and high sensitivity with a low detection limit of 30 cells mL(-1). Furthermore, after the electrochemical detection, the activation potential of -0.9 to -1.7V was performed to break Au-thiol bond and regenerate a bare gold electrode surface, while maintaining the good characteristic of being used repeatedly. The changes of gold electrode behavior after assembling and desorption processes were investigated by electrochemical impedance spectroscopy and cyclic voltammetry techniques. These results indicate that the cytosensor has great potential in disease diagnostic of cancers and opens new insight into the reusable gold electrode with repeatable assembling and disassembling in the electrochemical sensing.

  17. Impact of Surface Chemistry on Nanoparticle-Electrode Interactions in the Electrochemical Detection of Nanoparticle Collisions.

    PubMed

    Chen, Chang-Hui; Ravenhill, Emma R; Momotenko, Dmitry; Kim, Yang-Rae; Lai, Stanley C S; Unwin, Patrick R

    2015-11-01

    The electrochemical detection of a single nanoparticle (NP) at a support electrode can provide key information on surface chemistry and fundamental electron transfer (ET) properties at the nanoscale. This study employs scanning electrochemical cell microscopy (SECCM) as a fluidic device to both deliver individual citrate-capped gold nanoparticles (AuNPs) and study the interactions between them and a range of alkanethiol-modified Au electrodes with different terminal groups, namely, -COOH, -OH, and -CH3. Single NP collisions were detected through the AuNP-mediated ET reaction of Fe(CN)6(4-/3-) in aqueous solution. The collision frequency, residence time, and current-time characteristics of AuNPs are greatly affected by the terminal groups of the alkanethiol. Methods to determine these parameters, including the effect of the instrument response function, and derive ET kinetics are outlined. To further understand the interactions of AuNPs with these surfaces, atomic force microscopy (AFM) force measurements were performed using citrate-modified Au-coated AFM tips and the same alkanethiol-modified Au substrates in aqueous solution at the same potential bias as for the AuNP collision experiments. Force curves on OH-terminated surfaces showed no repulsion and negligible adhesion force. In contrast, a clear repulsion (on approach) was seen for COOH-terminated surface and adhesion forces (on retract) were observed for both COOH- and CH3-terminated surfaces. These interactions help to explain the residence times and collision frequencies in AuNP collisions. More generally, as the interfacial properties probed by AFM appear to be amplified in NP collision experiments, and new features also become evident, it is suggested that such experiments provide a new means of probing surface chemistry at the nanoscale.

  18. Optimal probe length and target location for electrochemical detection of selected uropathogens at ambient temperature.

    PubMed

    Mastali, Mitra; Babbitt, Jane T; Li, Yang; Landaw, Elliot M; Gau, Vincent; Churchill, Bernard M; Haake, David A

    2008-08-01

    We have previously demonstrated the clinical validity of the rapid detection of uropathogens by use of a DNA biosensor. This assay involves the hybridization of capture and detector probe pairs with bacterial 16S rRNA target molecules to form a DNA-RNA sandwich on the sensor surface. Horseradish peroxidase-conjugated antibody binds to the detector probe to enzymatically amplify the hybridization signal. These previous studies involved the hybridization of bacterial 16S rRNA target sequences with 35-mer oligonucleotide probe pairs at 65 degrees C. Achievement of point-of-care technology will be greatly facilitated by ambient-temperature detection. The purpose of this study was to examine the effects of probe length and target location on signal intensity using hybridization temperatures of 20 to 25 degrees C. Signal intensity was found to vary dramatically with hybridization location in the species-specific bulge region of 16S rRNA helix 18. Probe pairs of as short as 10 nucleotides in length were able to produce a significant electrochemical signal, and signal intensity was correlated with probe length for probes of 10 to 20 nucleotides in length. The sensitivity of the Escherichia coli-specific 15-mer probe pairs was approximately 330 cells. These shorter probes allowed differentiation of Klebsiella pneumoniae from Proteus mirabilis 16S rRNA target sequences differing by a single nucleotide. A panel of oligonucleotide probe pairs ranging from 11 to 23 nucleotides in length was able to distinguish among seven groups of urinary tract pathogens. In conclusion, we have developed short oligonucleotide probe pairs for the species-specific identification of uropathogens at ambient temperature by use of an electrochemical sensor.

  19. Silver nanoparticles anchored on nitrogen-doped graphene as a novel electrochemical biosensing platform with enhanced sensitivity for aptamer-based pesticide assay.

    PubMed

    Jiang, Ding; Du, Xiaojiao; Liu, Qian; Zhou, Lei; Dai, Liming; Qian, Jing; Wang, Kun

    2015-09-21

    Silver nanoparticles (NPs) decorated nitrogen doped graphene (NG) nanocomposites were prepared through a one-step thermal-treatment route using arginine as the nitrogen source. By integrating the excellent electrical properties and large surface area of Ag NPs and NG, the obtained Ag/NG nanocomposites show more effective electron transfer and high loading capacity than Ag-graphene and pure NG. In the presence of a target, the stronger interaction between the aptamer and the target promotes the formation of a target-aptamer complex on the electrode surface which blocks the electron transfer. Based on this sensing mechanism, a novel and highly sensitive biosensing platform by the use of Ag/NG as enhancing materials is demonstrated for detection of the model target, acetamiprid. The presented aptasensor exhibited a wide linear response for acetamiprid in the range of 1 × 10(-13) M to 5 × 10(-9) M with a low detection limit of 3.3 × 10(-14) M (S/N = 3). Moreover, this electrochemical aptasensor avoided complicated labeling procedures and showed magnificent sensitivity, high selectivity and low cost, which made it not only convenient but also time-saving and applicable. Furthermore, the proposed design may offer a promising way to develop a new electrochemical aptasensor for sensitive and specific detection of a wide spectrum of analytes in food, medical and environmental fields. PMID:26252168

  20. Silver nanoparticles anchored on nitrogen-doped graphene as a novel electrochemical biosensing platform with enhanced sensitivity for aptamer-based pesticide assay.

    PubMed

    Jiang, Ding; Du, Xiaojiao; Liu, Qian; Zhou, Lei; Dai, Liming; Qian, Jing; Wang, Kun

    2015-09-21

    Silver nanoparticles (NPs) decorated nitrogen doped graphene (NG) nanocomposites were prepared through a one-step thermal-treatment route using arginine as the nitrogen source. By integrating the excellent electrical properties and large surface area of Ag NPs and NG, the obtained Ag/NG nanocomposites show more effective electron transfer and high loading capacity than Ag-graphene and pure NG. In the presence of a target, the stronger interaction between the aptamer and the target promotes the formation of a target-aptamer complex on the electrode surface which blocks the electron transfer. Based on this sensing mechanism, a novel and highly sensitive biosensing platform by the use of Ag/NG as enhancing materials is demonstrated for detection of the model target, acetamiprid. The presented aptasensor exhibited a wide linear response for acetamiprid in the range of 1 × 10(-13) M to 5 × 10(-9) M with a low detection limit of 3.3 × 10(-14) M (S/N = 3). Moreover, this electrochemical aptasensor avoided complicated labeling procedures and showed magnificent sensitivity, high selectivity and low cost, which made it not only convenient but also time-saving and applicable. Furthermore, the proposed design may offer a promising way to develop a new electrochemical aptasensor for sensitive and specific detection of a wide spectrum of analytes in food, medical and environmental fields.

  1. Electrochemical detection of commercial silver nanoparticles: identification, sizing and detection in environmental media

    NASA Astrophysics Data System (ADS)

    Stuart, E. J. E.; Tschulik, K.; Omanović, D.; Cullen, J. T.; Jurkschat, K.; Crossley, A.; Compton, R. G.

    2013-11-01

    The electrochemistry of silver nanoparticles contained in a consumer product has been studied. The redox properties of silver particles in a commercially available disinfectant cleaning spray were investigated via cyclic voltammetry before particle-impact voltammetry was used to detect single particles in both a typical aqueous electrolyte and authentic seawater media. We show that particle-impact voltammetry is a promising method for the detection of nanoparticles that have leached into the environment from consumer products, which is an important development for the determination of risks associated with the incorporation of nanotechnology into everyday products.

  2. Electrochemical Techniques

    SciTech Connect

    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.

  3. Label-free, isothermal and ultrasensitive electrochemical detection of DNA and DNA 3'-phosphatase using a cascade enzymatic cleavage strategy.

    PubMed

    Liu, Shufeng; Liu, Tao; Wang, Li

    2015-01-01

    Label-free and ultrasensitive electrochemical assays of target DNA and T4 polynucleotide kinase phosphatase (PNKP) were developed, which took full advantage of three enzymes to realize the signal readout and amplification. It can ultimately achieve the low detection limits of 10 fM and 1 mU mL(-1) for target DNA and PNKP, respectively.

  4. Manganese porphyrin-double stranded DNA complex guided in situ deposition of polyaniline for electrochemical thrombin detection.

    PubMed

    Xie, Shunbi; Chai, Yaqin; Yuan, Yali; Yuan, Ruo

    2014-07-11

    In this work, we proposed a novel electrochemical strategy for sensitive detection of thrombin (TB) based on in situ generation of polyaniline (PANI) as a redox mediator by using a manganese porphyrin-double stranded DNA (MnTMPyP-dsDNA) peroxidase-like artificial enzyme mimic as a powerful catalyst and template.

  5. Detection of IP-10 protein marker in undiluted blood serum via an electrochemical E-DNA scaffold sensor

    PubMed Central

    Bonham, Andrew J.; Paden, Nicole G.; Ricci, Francesco

    2014-01-01

    We describe an electrochemical analog of fluorescence polarization that supports the quantitative measurement of a specific protein, the chemokine IP-10, directly in undiluted blood serum. The sensor is label-free, wash-free, and electronic, suggesting it could support point-of-care detection of diagnostic proteins in largely unprocessed clinical samples. PMID:23905162

  6. Mesoporous transition metal oxides quasi-nanospheres with enhanced electrochemical properties for supercapacitor applications.

    PubMed

    Wang, Lu; Duan, Guorong; Zhu, Junwu; Chen, Shen-Ming; Liu, Xiao-Heng; Palanisamy, Selvakumar

    2016-12-01

    In this report, we obtain mesoporous transition metal oxides quasi-nanospheres (includes MnO2, NiO, and Co3O4) by utilizing mesoporous silica nanospheres as a template for high-performance supercapacitor electrodes. All samples have a large specific surface area of approximately 254-325m(2)g(-1) and a relatively narrow pore size distribution in the region of 7nm. Utilization of a nanosized template resulted in a product with a relative uniform morphology and a small particle diameter in the region of 50-100nm. As supercapacitor electrodes, MnO2, NiO, and Co3O4 exhibit an outstanding capacity as high as 838-1185Fg(-1) at 0.5Ag(-1) and a superior long-term stability with minimal loss of 3-7% after 6000 cycles at 1Ag(-1). Their excellent electrochemical performances are attributed to favorable morphologies with a large surface area and a uniform architecture with abundant pores. The associated enhancement of electrolyte ion circulation within the electrode facilitates a significant increase in availability of Faradic reaction electroactive sites.

  7. Enhanced Electrochemical Lithium Storage Activity of LiCrO2 by Size Effect

    SciTech Connect

    Feng, G.; Li, L; Liu, J; Liu, N; Li, H; Yang, X; Huang, X; Chen, L; Nam, K; Yoon, W

    2009-01-01

    Cr8O21 was chemically lithiated using a lithium-biphenyl-dimethoxyethane solution. Lithiated Cr8O21 shows a structure in which as-formed LiCrO2 units are sandwiched between Cr2O3 superlattice layers. Chemically lithiated Cr8O21 shows a delithiation capacity of 200 mAh g-1. It means that LiCrO2 units in lithiated Cr8O21 are electrochemically active. This finding is opposite to previous reports that LiCrO2 materials have very poor Li-storage capacities. Our new result implies that LiCrO2 with extremely small domain size could show enhanced reactivity. This proposal is proved unambiguously by the fact that LiCrO2 powder materials with smaller grain size (<20 nm) show much higher capacities than LiCrO2 materials with larger grain size (>50 nm). In addition, it is found that the cation mixing is more significantly in LiCrO2 materials with smaller grain size, which seems a key factor for the storage and transport of lithium in layered Cr-based materials. The cation mixing may also explain the result that the lattice parameters of LiCrO2 do not change significantly upon lithium extraction and insertion, investigated by in situ and ex situ XRD techniques.

  8. Enhanced Conductivity and Electrochemical Performance of Electrode Material Based on Multifunctional Dye Doped Polypyrrole.

    PubMed

    Zang, Limin; Qiu, Jianhui; Yang, Chao; Sakai, Eiichi

    2016-03-01

    Polypyrrole were prepared via in-situ chemical oxidative polymerization in the presence of multisulfonate acid dye (acid violet 19). In this work, acid violet 19 could play the role as dopant, surfactant and physical cross-linker for pyrrole polymerization, and had impact on the morphology, dispersion stability, thermal stability, electrical conductivity and electrochemical behavior of the samples. The thermal stability of the dye doped polypyrrole was enhanced than pure polypyrrole due to the strong interactions between polypyrrole and acid violet 19. The dispersion stability of the samples in water was also improved by incorporating an appropriate amount of acid violet 19. The sample with 20% of acid violet 19 showed granular morphology with the smallest diameter of -50 nm and possessed the maximum electrical conductivity of 39.09 S/cm. The as-prepared multifunctional dye doped polypyrrole samples were used to fabricate electrodes and exhibited a mass specific capacitance of 379-206 F/g in the current density range of 0.2-1.0 A/g. The results indicated that the multifunctional dye could improve the performances of polypyrrole as electrode material for supercapacitors. PMID:27455670

  9. Mesoporous transition metal oxides quasi-nanospheres with enhanced electrochemical properties for supercapacitor applications.

    PubMed

    Wang, Lu; Duan, Guorong; Zhu, Junwu; Chen, Shen-Ming; Liu, Xiao-Heng; Palanisamy, Selvakumar

    2016-12-01

    In this report, we obtain mesoporous transition metal oxides quasi-nanospheres (includes MnO2, NiO, and Co3O4) by utilizing mesoporous silica nanospheres as a template for high-performance supercapacitor electrodes. All samples have a large specific surface area of approximately 254-325m(2)g(-1) and a relatively narrow pore size distribution in the region of 7nm. Utilization of a nanosized template resulted in a product with a relative uniform morphology and a small particle diameter in the region of 50-100nm. As supercapacitor electrodes, MnO2, NiO, and Co3O4 exhibit an outstanding capacity as high as 838-1185Fg(-1) at 0.5Ag(-1) and a superior long-term stability with minimal loss of 3-7% after 6000 cycles at 1Ag(-1). Their excellent electrochemical performances are attributed to favorable morphologies with a large surface area and a uniform architecture with abundant pores. The associated enhancement of electrolyte ion circulation within the electrode facilitates a significant increase in availability of Faradic reaction electroactive sites. PMID:27552415

  10. Generation of Small Single Domain Nanobody Binders for Sensitive Detection of Testosterone by Electrochemical Impedance Spectroscopy.

    PubMed

    Li, Guanghui; Zhu, Min; Ma, Lu; Yan, Junrong; Lu, Xiaoling; Shen, Yanfei; Wan, Yakun

    2016-06-01

    A phage display library of variable domain of the heavy chain only antibody or nanobody (Nb) was constructed after immunizing a bactrian camel with testosterone. With the smaller molecular size (15 kDa), improved solubility, good stability, high affinity, specificity, and lower immunogenicity, Nbs are a promising tool in the next generation of diagnosis and medical applications. Testosterone is a reproductive hormone, playing an important role in normal cardiac function and being the highly predictive marker for many diseases. Herein, a simple and sensitive immunosensor based on electrochemical impedance spectroscopy (EIS) and Nbs was successfully developed for the determination of testosterone. We successfully isolated the antitestosterone Nbs from an immune phage display library. Moreover, one of the Nbs was biotinylated according to in vivo BirA system, which showed the highest production yield and the most stable case. Further, the EIS immunosensor was set up for testosterone detection by applying the biotinylated antitestosterone Nb. As a result, the biosensor exhibited a linear working range from 0.05 to 5 ng mL(-1) with a detection limit of 0.045 ng mL(-1). In addition, the proposed immunosensor was successfully applied in determining testosterone in serum samples. In conclusion, the proposed immunosensor revealed high specificity of testosterone detection and showed as a potential approach for sensitive and accurate diagnosis of testosterone.

  11. A label-free electrochemical impedance aptasensor for cylindrospermopsin detection based on thionine-graphene nanocomposites.

    PubMed

    Zhao, Zhen; Chen, Hongda; Ma, Lina; Liu, Dianjun; Wang, Zhenxin

    2015-08-21

    It is important to develop methods to determine cylindrospermopsin (CYN) at trace levels since CYN is a kind of widespread cyanobacterial toxin in water sources. In this study, a label-free impedimetric aptasensor has been fabricated for detecting CYN. In this case, the amino-substituted aptamer of CYN was covalently grafted onto the surface of the thionine-graphene (TH-G) nanocomposite through the cross-linker glutaraldehyde (GA). The reaction of the aptamer with CYN was monitored by electrochemical impedance spectroscopy because the CYN induced conformation change of the aptamer can cause a remarkable decrease of the electron transfer resistance. Under optimum conditions, the aptasensor exhibits high sensitivity and a low detection limit for CYN determination. The CYN can be quantified in a wide range of 0.39 to 78 ng mL(-1) with a good linearity (R(2) = 0.9968) and a low detection limit of 0.117 ng mL(-1). In addition, the proposed aptasensor displays excellent stability, reusability and reproducibility. PMID:26111280

  12. Rapid detection and quantification of free hemoglobin and haptoglobin by nanogold modified electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Lu, Yu-Ning; Li, Hsing-Yuan; Chu, Hsueh-Liang; Cheng, Tsia-Mu; Tseng, Shin-Hua; Chang, Chia-Ching

    2013-03-01

    Free Hemoglobin (Hb) is a metabolic substance that damage tissue and vessel. It is released from destructed red blood cell and causes infection or inflammatory of human body. In blood plasma, haptoglobin (Hp) binds free Hb with high affinity and prevents the damage which is caused by cell free Hb. Hp has three phenotypes, that are Hp1-1, Hp 2-1, and Hp 2-2. Different phenotypes of Hp has been different affinities to Hb. It is known that electrochemical impedance spectroscopy (EIS) provide more information for detecting the small amount bio-molecules, include protein and DNA. In this study, we have developed a simple, fast, reliable and sensitive platform to quantify concentration of free Hb and Hp. In this platform, detection probe has been modified with nano gold and the surface charge transfer resistance of Hb and Hp binding could be detected and quantified within 18 min. This is a whole new platform to quantify free Hb in the serum of human to our knowledge.

  13. Determination of paroxetine in blood and urine using micellar liquid chromatography with electrochemical detection.

    PubMed

    Agrawal, Nitasha; Marco-Peiró, Sergio; Esteve-Romero, Josep; Durgbanshi, Abhilasha; Bose, Devasish; Peris-Vicente, Juan; Carda-Broch, Samuel

    2014-01-01

    Paroxetine is a potent selective serotonin reuptake inhibitor used for the treatment of depression and related mood disorders. A micellar liquid chromatographic method was developed for the determination of paroxetine in serum and urine. Detection of paroxetine was carried out using a C18 column and a mobile phase of 0.15 M sodium dodecyl sulfate, 6% 1-pentanol at pH 3 (buffer salt 0.01 M NaH2PO4) running under isocratic mode at 1.0 mL/min and electrochemical detection at 0.8 V. The analyte was eluted without interferences in <15 min. The proposed methodology was validated under the guidelines of the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use in matrix in terms of specificity, linearity (r(2) > 0.9999; 0.5-5 μg/mL range), accuracy (88-97.5%, recovery), repeatability (RSD < 0.54%), intermediate precision (RSD < 0.54%), limit of detection and quantification (0.001 and 0.005 μg/mL, respectively) and robustness (RSD < 3.63%). Developed method was successfully applied to real blood and urine samples as well as in spiked serum and urine samples. The developed method was specific, rapid, precise, reliable, accurate, inexpensive and then suitable for routine analysis of paroxetine in monitorized samples.

  14. Electrochemical detection of aqueous Ag+ based on Ag+-assisted ligation reaction

    PubMed Central

    Miao, Peng; Han, Kun; Wang, Bidou; Luo, Gangyin; Wang, Peng; Chen, Mingli; Tang, Yuguo

    2015-01-01

    In this work, a novel strategy to fabricate a highly sensitive and selective biosensor for the detection of Ag+ is proposed. Two DNA probes are designed and modified on a gold electrode surface by gold-sulfur chemistry and hybridization. In the presence of Ag+, cytosine-Ag+-cytosine composite forms and facilitates the ligation event on the electrode surface, which can block the release of electrochemical signals labeled on one of the two DNA probes during denaturation process. Ag+ can be sensitively detected with the detection limit of 0.1 nM, which is much lower than the toxicity level defined by U.S. Environmental Protection Agency. This biosensor can easily distinguish Ag+ from other interfering ions and the performances in real water samples are also satisfactory. Moreover, the two DNA probes are designed to contain the recognition sequences of a nicking endonuclease, and the ligated DNA can thus be cleaved at the original site. Therefore, the electrode can be regenerated, which allows the biosensor to be reused for additional tests. PMID:25779347

  15. Hierarchic micro-patterned porous scaffolds via electrochemical replica-deposition enhance neo-vascularization.

    PubMed

    Varoni, Elena Maria; Altomare, Lina; Cochis, Andrea; GhalayaniEsfahani, Arash; Cigada, Alberto; Rimondini, Lia; De Nardo, Luigi

    2016-04-21

    Neo-vascularization is a key factor in tissue regeneration within porous scaffolds. Here, we tested the hypothesis that micro-patterned scaffolds, with precisely-designed, open micro-channels, might help endothelial cells to produce intra-scaffold vascular networks. Three series of micro-patterned scaffolds were produced via electrochemical replica-deposition of chitosan and cross-linking. All had regularly-oriented micro-channels (ϕ 500 μm), which differed for the inter-channel spacing, at 600, 700, or 900 μm, respectively. Random-pore scaffolds, using the same technique, were taken as controls. Physical-mechanical characterization revealed high water uptake and favorable elastic mechanical behavior for all scaffolds, slightly reduced in the presence of cross-linking and enhanced with the 700 μm-spaced micro-pattern. At MTT assay, mouse endothelial cell viability was >90% at day 1, 3 and 7, confirmed by visual examination with scanning electron microscopy (SEM). Intra-scaffold cell density, at fluorescence analysis, was higher for the 600 μm-spaced and the 700 μm-spaced micro-patterns over the others. The 700 μm-spaced scaffold was selected for the in vivo testing, to be compared to the random-pore one. Neither type produced an inflammatory reaction; both showed excellent tissue ingrowth. Micro-patterned scaffolds enhanced neo-vascularization, demonstrated by immunofluorescent, semi-quantitative analyses. These findings support the use of micro-patterned porous scaffolds, with adequately spaced micro-channels, to promote neo-vascularization.

  16. Highly Sensitive Bacteria Quantification Using Immunomagnetic Separation and Electrochemical Detection of Guanine-Labeled Secondary Beads

    PubMed Central

    Jayamohan, Harikrishnan; Gale, Bruce K.; Minson, Bj; Lambert, Christopher J.; Gordon, Neil; Sant, Himanshu J.

    2015-01-01

    In this paper, we report the ultra-sensitive indirect electrochemical detection of E. coli O157:H7 using antibody functionalized primary (magnetic) beads for capture and polyguanine (polyG) oligonucleotide functionalized secondary (polystyrene) beads as an electrochemical tag. Vacuum filtration in combination with E. coli O157:H7 specific antibody modified magnetic beads were used for extraction of E. coli O157:H7 from 100 mL samples. The magnetic bead conjugated E. coli O157:H7 cells were then attached to polyG functionalized secondary beads to form a sandwich complex (magnetic bead/E. coli/ secondary bead). While the use of magnetic beads for immuno-based capture is well characterized, the use of oligonucleotide functionalized secondary beads helps combine amplification and potential multiplexing into the system. The antibody functionalized secondary beads can be easily modified with a different antibody to detect other pathogens from the same sample and enable potential multiplexing. The polyGs on the secondary beads enable signal amplification up to 108 guanine tags per secondary bead (7.5 × 106 biotin-FITC per secondary bead, 20 guanines per oligonucleotide) bound to the target (E. coli). A single-stranded DNA probe functionalized reduced graphene oxide modified glassy carbon electrode was used to bind the polyGs on the secondary beads. Fluorescent imaging was performed to confirm the hybridization of the complex to the electrode surface. Differential pulse voltammetry (DPV) was used to quantify the amount of polyG involved in the hybridization event with tris(2,2′-bipyridine)ruthenium(II) ( Ru(bpy)32+) as the mediator. The amount of polyG signal can be correlated to the amount of E. coli O157:H7 in the sample. The method was able to detect concentrations of E. coli O157:H7 down to 3 CFU/100 mL, which is 67 times lower than the most sensitive technique reported in literature. The signal to noise ratio for this work was 3. We also demonstrate the use of the

  17. Preparation of gold tips suitable for tip-enhanced Raman spectroscopy and light emission by electrochemical etching

    NASA Astrophysics Data System (ADS)

    Ren, Bin; Picardi, Gennaro; Pettinger, Bruno

    2004-04-01

    We describe a method of preparing gold scanning tunneling microscopy (STM) tips by direct current electrochemical etching in concentrated HCl and ethanol solution. Gold tips with tip apex radius lower than 30 nm can be reproducibly prepared by this method. The influence of the solution composition, etching voltage on the surface structure, and sharpness has been investigated. These tips can be efficiently used for STM imaging, tip-enhanced Raman spectroscopy, and light emission investigations on the same sample.

  18. Human haptoglobin phenotypes and concentration determination by nanogold-enhanced electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Cheng, Tsai-Mu; Lee, Tzu-Cheng; Tseng, Shin-Hua; Chu, Hsueh-Liang; Pan, Ju-Pin; Chang, Chia-Ching

    2011-06-01

    Haptoglobin (Hp) is an acute phase protein that binds free hemoglobin (Hb), preventing Hb-induced oxidative damage in the vascular system. There are three phenotypes in human Hp, whose heterogeneous polymorphic structures and varying concentrations in plasma have been attributed to the cause of diseases and outcome of clinical treatments. Different phenotypes of Hp may be composed of the same subunits but different copy numbers, rendering their determination difficult by a single procedure. In this study, we have developed a simple, fast, reliable and sensitive method, using label-free nanogold-modified bioprobes coupled with self-development electrochemical impedance spectroscopy (EIS). By this method, probe surface charge transfer resistance is detected. The relative charge transfer resistance ratios for Hp 1-1, Hp 2-1 and Hp 2-2 were characterized. We were able to determine protein size difference within 3 nm, and the linear region of the calibration curve for Hp levels in the range of 90 pg ml - 1 and 90 µg ml - 1 (~1 fM to 1 pM). We surmise that similar approaches can be used to investigate protein polymorphism and altered protein-protein interaction associated with diseases.

  19. Sensitive and direct electrochemical detection of double-stranded DNA utilizing alkaline phosphatase-labelled zinc finger proteins.

    PubMed

    Noh, Soodong; Ha, Dat Thinh; Yang, Haesik; Kim, Moon-Soo

    2015-06-21

    Direct detection of double-stranded DNA (dsDNA) using zinc finger proteins (ZFPs) is of great importance in biomedical applications such as identifying pathogens and circulating DNAs. However, its sensitivity is still not sufficiently high because limited signalling labels can be conjugated or fused. Herein, we report sensitive and direct detection of dsDNA using (i) alkaline phosphatase (ALP) as a fast catalytic label conjugated to ZFPs along with (ii) electrochemical measurement of an ALP product (l-ascorbic acid) at the indium-tin oxide electrode with a high signal-to-background ratio. ALP is simply conjugated to a ZFP through lysine residues in a ZFP purification tag, a maltose binding protein (MBP). Sandwich-type electrochemical detection of dsDNA allows a detection limit of ca. 100 fM without using DNA amplification. PMID:25969923

  20. Fast and sensitive detection of foodborne pathogen using electrochemical impedance analysis, urease catalysis and microfluidics.

    PubMed

    Chen, Qi; Wang, Dan; Cai, Gaozhe; Xiong, Yonghua; Li, Yuntao; Wang, Maohua; Huo, Huiling; Lin, Jianhan

    2016-12-15

    Early screening of pathogenic bacteria is a key to prevent and control of foodborne diseases. In this study, we developed a fast and sensitive bacteria detection method integrating electrochemical impedance analysis, urease catalysis with microfluidics and using Listeria as model. The Listeria cells, the anti-Listeria monoclonal antibodies modified magnetic nanoparticles (MNPs), and the anti-Listeria polyclonal antibodies and urease modified gold nanoparticles (AuNPs) were incubated in a fluidic separation chip with active mixing to form the MNP-Listeria-AuNP-urease sandwich complexes. The complexes were captured in the separation chip by applying a high gradient magnetic field, and the urea was injected to resuspend the complexes and hydrolyzed under the catalysis of the urease on the complexes into ammonium ions and carbonate ions, which were transported into a microfluidic detection chip with an interdigitated microelectrode for impedance measurement to determine the amount of the Listeria cells. The capture efficiency of the Listeria cells in the separation chip was ∼93% with a shorter time of 30min due to the faster immuno-reaction using the active magnetic mixing. The changes on both impedance magnitude and phase angle were demonstrated to be able to detect the Listeria cells as low as 1.6×10(2)CFU/mL. The detection time was reduced from original ∼2h to current ∼1h. The recoveries of the spiked lettuce samples ranged from 82.1% to 89.6%, indicating the applicability of this proposed biosensor. This microfluidic impedance biosensor has shown the potential for online, automatic and sensitive bacteria separation and detection.