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Sample records for resonance based immunosensor

  1. High-sensitive nonlinear detection of steroids by resonant double grating waveguide structures-based immunosensors

    NASA Astrophysics Data System (ADS)

    Muriano, Alejandro; Salvador, J.-Pablo; Galve, Roger; Marco, M.-Pilar; Thayil K. N., Anisha; Loza-Alvarez, Pablo; Soria, Silvia

    2011-01-01

    We report the non linear fluorescence real-time detection of methylboldenone, an androgenic anabolic steroid used illegally as growth promoter based on a resonant sensing chip: a double grating waveguide structure. The limit of detection of this synthetic steroid is two orders of magnitude lower than the Minimum Required Performance Limit required by the World Anti-Doping Agency. The immunoreagents have been have been immobilized onto the surface of the resonant sensor after being activated with phosphonohexanoic acid spacers. The developed immunosensor presents great potential as a robust sensing device for fast and early detection of illegal dopants and food contaminants.

  2. Surface Plasmon Resonance Based Sensitive Immunosensor for Benzaldehyde Detection

    NASA Astrophysics Data System (ADS)

    Onodera, Takeshi; Shimizu, Takuzo; Miura, Norio; Matsumoto, Kiyoshi; Toko, Kiyoshi

    Fragrant compounds used to add flavor to beverages remain in the manufacturing line after the beverage manufacturing process. Line cleanliness before the next manufacturing cycle is difficult to estimate by sensory analysis, making excessive washing necessary. A new measurement system to determine line cleanliness is desired. In this study, we attempted to detect benzaldehyde (Bz) using an anti-Bz monoclonal antibody (Bz-Ab) and a surface plasmon resonance (SPR) sensor. We fabricated two types of sensor chips using self-assembled monolayers (SAMs) and investigated which sensor surface exhibited higher sensitivity. In addition, anti-Bz antibody conjugated with horseradish peroxidase (HRP-Bz-Ab) was used to enhance the SPR signal. A detection limit of ca. 9ng/mL (ppb) was achieved using an immobilized 4-carboxybenzaldehyde sensor surface using SAMs containing ethylene glycol. When the HRP-Bz-Ab concentration was reduced to 30ng/mL, a detection limit of ca. 4ng/mL (ppb) was achieved for Bz.

  3. Surface plasmon resonance immunosensor for human cardiac troponin T based on self-assembled monolayer.

    PubMed

    Dutra, Rosa Fireman; Mendes, Renata Kelly; Lins da Silva, Valdinete; Kubota, Lauro Tatsuo

    2007-04-11

    The cardiac troponin T (cTnT) is specific biomarker important for trials of acute myocardial infarctions (AMI). In this paper, a SPR sensor in real time to detect the biomarker was developed on a commercially available surface plasmon resonance AUTOLAB SPIRIT. The cTnT receptor molecule was covalently immobilized on a gold substrate via a self-assembled monolayer (SAM) of thiols by using cysteamine-coupling chemistry. This biosensor presented a linear response range for cTnT between 0.05 and 4.5 ng/mL (r=0.997, p<0.01) with a good reproducibility (CV=4.4%). The effect of the cysteamine (CYS) concentrations on the SAM coated gold sensor was studied as a function of the amount of the immobilized cTnT monoclonal antibodies. Analysis using serum samples undiluted was carried out at room temperature showing a well agreement with the ECLIA methods and the sensor surface could be regenerated by using a solution of 1% (w/v) sodium dodecyl sulphate (SDS) without losing the sensor immunoreactivity. These studies open new perspectives of using SAM to develop regenerable immunosensor with a good reproducibility allowing its use in the clinical applications. PMID:17254730

  4. A Surface Plasmon Resonance-Based Immunosensors for Sensitive Detection of Heroin

    NASA Astrophysics Data System (ADS)

    Wu, Zhong-cheng; Chen, Wen-ge; Wang, Lian-chao; Ge, Yu; Yu, Cheng-duan; Fang, Ting-jian

    2000-12-01

    A simple technique for sensitive detection of heroin based on surface-plasmon-resonance has been theoretically and experimentally investigated. The experiment was realized by using an anti-MO monoclonal antibody and a morphine (MO)-bovine serum albumin (MO-BSA) conjugate (antigen). The reason for using MO-BSA in the detection of heroine was also discussed. MO-BSA was immobilized on a gold thin film of SPR sensor chip by physical adsorption. The configuration of the device is allowed to be further miniaturized, which is required for the construction of a portable SPR device in the application of in-situ analysis.

  5. Development of a Surface Plasmon Resonance-Based Immunosensor for Detection of 10 Major O-Antigens on Shiga Toxin-Producing Escherichia coli, with a Gel Displacement Technique To Remove Bound Bacteria.

    PubMed

    Yamasaki, Tomomi; Miyake, Shiro; Nakano, Satoshi; Morimura, Hiroyuki; Hirakawa, Yuki; Nagao, Miki; Iijima, Yoshio; Narita, Hiroshi; Ichiyama, Satoshi

    2016-07-01

    A surface plasmon resonance-based immunosensor (SPR-immunosensor) was developed for the detection of Shiga toxin-producing Escherichia coli (STEC) belonging to the O-antigen groups O26, O91, O103, O111, O115, O121, O128, O145, O157, and O159. The polyclonal antibodies (PoAbs) generated against each of the STEC O-antigen types in rabbits were purified and were immobilized on the sensor chip at 0.5 mg/mL. The limit of detection for STEC O157 by the SPR-immunosensor was found to be 6.3 × 10(4) cells for 75 s. Each of the examined 10 O-antigens on the STECs was detected by the corresponding PoAb with almost no reaction to the other PoAbs. The detected STECs were sufficiently removed from the PoAbs using gelatin or agarose gel without deactivation of the PoAbs, enabling repeatable use of the sensor chip. The developed SPR-immunosensor can be applied for the detection of multiple STEC O-antigens. Furthermore, the new antigen removal technique using the gel displacement approach can be utilized with various immunosensors to improve the detection of pathogens in clinical and public health settings. PMID:27243947

  6. Ring-Resonator/Sol-Gel Interferometric Immunosensor

    NASA Technical Reports Server (NTRS)

    Bearman, Gregory; Cohen, David

    2007-01-01

    A proposed biosensing system would be based on a combination of (1) a sensing volume containing antibodies immobilized in a sol-gel matrix and (2) an optical interferometer having a ring resonator configuration. The antibodies would be specific to an antigen species that one seeks to detect. In the ring resonator of the proposed system, light would make multiple passes through the sensing volume, affording greater interaction length and, hence, greater antibody- detection sensitivity.

  7. Analysis of the Fungicide Boscalid in Horticultural Crops Using an Enzyme-Linked Immunosorbent Assay and an Immunosensor Based on Surface Plasmon Resonance.

    PubMed

    Hirakawa, Yuki; Yamasaki, Tomomi; Harada, Ayako; Ohtake, Toshiya; Adachi, Kayo; Iwasa, Seiji; Narita, Hiroshi; Miyake, Shiro

    2015-09-16

    A direct competitive enzyme-linked immunosorbent assay (dc-ELISA) and an immunosensor based on surface plasmon resonance (SPR-sensor) were developed for fungicide boscalid determination in horticultural crops. To produce antiboscalid monoclonal antibodies (MoAb BSC7 and MoAb BSC72) for these assays, a hapten of boscalid was synthesized and conjugated to keyhole limpet hemocyanin for Balb/c mouse immunization. The working range of the dc-ELISA was 0.8-16 ng/mL with MoAb BSC7 and 2.5-120 ng/mL with MoAb BSC72, and that of the SPR-sensor was 17-80 ng/mL with MoAb BSC7. The dc-ELISA and SPR-sensor were compared for their sensitivity in determining boscalid residues at the maximum residue limit of 1-40 mg/kg for horticultural crops in Japan. Recovery of the spiked boscalid was 85-109% by the SPR-sensor and 100-124% by the dc-ELISA. On real tomato samples, the results obtained by both of these immunoassays correlated well with the results obtained by high-performance liquid chromatography. PMID:26340386

  8. A Flow SPR Immunosensor Based on a Sandwich Direct Method

    PubMed Central

    Tomassetti, Mauro; Conta, Giorgia; Campanella, Luigi; Favero, Gabriele; Sanzò, Gabriella; Mazzei, Franco; Antiochia, Riccarda

    2016-01-01

    In this study, we report the development of an SPR (Surface Plasmon Resonance) immunosensor for the detection of ampicillin, operating under flow conditions. SPR sensors based on both direct (with the immobilization of the antibody) and competitive (with the immobilization of the antigen) methods did not allow the detection of ampicillin. Therefore, a sandwich-based sensor was developed which showed a good linear response towards ampicillin between 10−3 and 10−1 M, a measurement time of ≤20 min and a high selectivity both towards β-lactam antibiotics and antibiotics of different classes. PMID:27187486

  9. A Flow SPR Immunosensor Based on a Sandwich Direct Method.

    PubMed

    Tomassetti, Mauro; Conta, Giorgia; Campanella, Luigi; Favero, Gabriele; Sanzò, Gabriella; Mazzei, Franco; Antiochia, Riccarda

    2016-01-01

    In this study, we report the development of an SPR (Surface Plasmon Resonance) immunosensor for the detection of ampicillin, operating under flow conditions. SPR sensors based on both direct (with the immobilization of the antibody) and competitive (with the immobilization of the antigen) methods did not allow the detection of ampicillin. Therefore, a sandwich-based sensor was developed which showed a good linear response towards ampicillin between 10(-3) and 10(-1) M, a measurement time of ≤20 min and a high selectivity both towards β-lactam antibiotics and antibiotics of different classes. PMID:27187486

  10. The phenomenon of fluorescence in immunosensors.

    PubMed

    Kłos-Witkowska, Aleksandra

    2016-01-01

    The phenomenon of fluorescence in immunosensors is described in this paper. Both structure and characteristics of biosensors and immunosensors are presented. Types of immunosensors and the response of bioreceptor layers to the reaction with analytes as well as measurements of electrochemical, piezoelectric and optical parameters in immunosensors are also presented. In addition, detection techniques used in studies of optical immunosensors based on light-matter interactions (absorbance, reflectance, dispersion, emission) such as: UV/VIS spectroscopy, reflectometric interference spectroscopy (RIfs), surface plasmon resonance (SPR), optical waveguide light-mode spectroscopy (OWLS), fluorescence spectroscopy. The phenomenon of fluorescence in immunosensors and standard configurations of immunoreactions between an antigen and an antibody (direct, competitive, sandwich, displacement) is described. Fluorescence parameters taken into account in analyses and fluorescence detection techniques used in research of immunosensors are presented. Examples of immunosensor applications are given. PMID:27192088

  11. ZnS-nanocrystals/polypyrrole nanocomposite film based immunosensor

    NASA Astrophysics Data System (ADS)

    Mishra, Sujeet K.; Pasricha, Renu; Biradar, Ashok M.; Rajesh

    2012-01-01

    We report an electrochemically synthesized ZnS nanocrystals modified polypyrrole (PPy) nanocomposite film based immunosensor for the detection of C-reactive protein (αCRP). The ZnS-PPy composite film was characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM) and electrochemical techniques. The modified film showed good biocompatibility with efficient binding to protein antibody (αCRP-Ab) molecules through ZnS nanocrystals, exhibited an attractive platform for immunosensor fabrication. The electrical and sensing properties of the polymer composite film of different thickness towards protein antigen (αCRP-Ag) were delineated. The immunosensor exhibited an impedance response to αCRP-Ag concentration in a linear range from 10 ng to 10 μg mL-1.

  12. Development of a surface plasmon resonance immunosensor for detecting melamine in milk products and pet foods.

    PubMed

    Lu, Yang; Xia, Yinqiang; Pan, Mingfei; Wang, Xiaojun; Wang, Shuo

    2014-12-24

    A sensitive and stable surface plasmon resonance (SPR) immunosensor based on the inhibition format was developed and validated for detecting melamine (MEL) in milk products and pet foods. The sensitivity and the limit of detection (LOD) of the proposed method for MEL were 2.32 × 10(-2) and 1.4 × 10(-3) μg/mL, respectively. The immunosensor was highly specific to MEL, which displayed only low cross-reactivity (CR) (<0.01%) for cyanuric acid, cyanuric chloride, and atrazine. The assay was validated for the detection of MEL in full-cream milk, skim milk powder, infant formula, dog food, and cat food. Most of the recovery results ranged between 76 and 115%. The sensitivities of the assay in each type of sample were 2.57 × 10(-2) μg/mL, 2.32 × 10(-2) μg/kg, 2.51 × 10(-2) μg/kg, 2.66 × 10(-2) μg/kg, and 2.68 × 10(-2) μg/kg, respectively, which were much lower than the maximum residue levels (MRLs) of MEL. PMID:25473730

  13. Surface plasmon resonance immunosensor for highly sensitive detection of 2,4,6-trinitrotoluene.

    PubMed

    Shankaran, Dhesingh Ravi; Gobi, K Vengatajalabathy; Sakai, Takatoshi; Matsumoto, Kiyoshi; Toko, Kiyoshi; Miura, Norio

    2005-03-15

    We have examined the sensing characteristics of a surface plasmon resonance (SPR) immunoassay for the detection of 2,4,6-trinitrotoluene (TNT) using an immunoreaction between 2,4,6-trinitrophenol-ovalbumin (TNP-OVA) conjugate and anti-2,4,6-trinitrophenol antibody (anti-TNP antibody). TNP-OVA conjugate was attached to a SPR-gold sensing surface by means of physical immobilization, which undergoes binding interaction with anti-TNP antibody. Both the immobilization and binding processes were studied from a change in the SPR-resonance angle. The quantification of TNT is based on the principle of indirect competitive immunoassay, in which the immunoreaction between the TNP-OVA conjugate and anti-TNP antibody was inhibited in the presence of free TNT in solution. The decrease in the resonance angle shift is proportional to an increase in concentration of TNT used for incubation. The immunoassay exhibited excellent sensitivity for the detection of TNT in the concentration range from 0.09 to 1000 ng/ml with good stability and reproducibility. The immunosensor developed could detect TNT as low as 0.09 ng/ml, within a response time of approximately 22 min. The sensor surface was regenerated by a brief flow of pepsin solution, which disrupts the antigen-antibody complex without destroying the conjugate biofilm. Cross-reactivity of the SPR sensor to some structurally related nitroaromatic derivative and the detection of TNT in the presence of these nitroaromatic compounds were investigated. The cross-reactivity of the SPR sensor to 2,4-dinitrotoluene (2,4-DNT), 1,3-dinitrobenzene (1,3-DNB), 2-amino-4,6-dinitrotoluene (2A-4,6-DNT) and 4-amino-2,6-dinitrotoluene (4A-2,6-DNT) were very low (< or =1.1%). The analytical characteristics of the proposed immunosensor are highly promising for the development of new field-portable sensors for on-site detection of landmines. PMID:15681190

  14. Elaboration of optical immunosensors based on the surface plasmon resonance for detecting specific antibodies and antigens of Epstein-Barr virus and human adenovirus.

    PubMed

    Nesterova, N V; Nosach, L M; Zagorodnya, S D; Povnitsa, O Y; Boltovets, P M; Baranova, G V; Golovan, A V

    2008-01-01

    The study of antigen-antibody interaction on the model of Epstein-Barr virus (EBV) and second type adenovirus (Ad2) based on the surface plasmon resonance (SPR) was carried out. Kinetic and concentration dependences between virus antigens and specific antisera to them at different pH were determined. Experimental samples of biosensors for the detection by SPR method of virus (EBV and Ad2) antigens using monospecific antibodies, immobilized on the surface of gold, and also for detection of specific antibodies in the blood sera of patients with EBV or adenovirus infection were elaborated PMID:19351051

  15. Noncovalently functionalized monolayer graphene for sensitivity enhancement of surface plasmon resonance immunosensors.

    PubMed

    Singh, Meenakshi; Holzinger, Michael; Tabrizian, Maryam; Winters, Sinéad; Berner, Nina C; Cosnier, Serge; Duesberg, Georg S

    2015-03-01

    A highly efficient surface plasmon resonance (SPR) immunosensor is described using a functionalized single graphene layer on a thin gold film. The aim of this approach was two-fold: first, to amplify the SPR signal by growing graphene through chemical vapor deposition and, second, to control the immobilization of biotinylated cholera toxin antigen on copper coordinated nitrilotriacetic acid (NTA) using graphene as an ultrathin layer. The NTA groups were attached to graphene via pyrene derivatives implying π-π interactions. With this setup, an immunosensor for the specific antibody anticholera toxin with a detection limit of 4 pg mL(-1) was obtained. In parallel, NTA polypyrrole films of different thicknesses were electrogenerated on the gold sensing platform where the optimal electropolymerization conditions were determined. For this optimized polypyrrole-NTA setup, the simple presence of a graphene layer between the gold and polymer film led to a significant increase of the SPR signal. PMID:25679322

  16. Impedimetric characterization of adsorption of Listeria monocytogenes on the surface of an aluminum-based immunosensor.

    PubMed

    Chai, Changhoon; Lee, Jooyoung; Oh, Se-Wook; Takhistov, Paul

    2014-11-01

    The impedimetric characteristics of an immunosensor depend on the electrical properties of an immunosensor substrate. The impedimetric characteristics of an immunosensor compared with adsorption of Listeria monocytogenes were investigated on an aluminum surface insulated with an electrically resistive aluminum oxide layer. Antibody for L. monocytogenes (anti-L. monocytogenes) was immobilized on an aluminum surface that was insulated with a native air-formed aluminum oxide layer. The resistance of impedance (R) value of an aluminum-based immunosensor decreased, especially at 10(4) to 10(6) Hz, where the effect of the reactance of impedance (X) was minimal when L. monocytogenes was adsorbed on the immunosensor surface. The R value of the immunosensor at 81 kHz decreased proportionally to the concentration of L. monocytogenes from 1.3 to 4.3 log CFU mL(-1) . The adsorption of L. monocytogenes produced local protrusions on the immunosensor surface, causing physicochemical changes in the ionic layer formed on the immunosensor surface by a sinusoidal electrical signal input, which might help electrical current to flow and cause the R value to decrease. PMID:25296910

  17. Development of an Immunosensor for Determination of the Fungicide Chlorothalonil in Vegetables, Using Surface Plasmon Resonance.

    PubMed

    Hirakawa, Yuki; Yamasaki, Tomomi; Watanabe, Eiki; Okazaki, Fumiko; Murakami-Yamaguchi, Yukie; Oda, Masayuki; Iwasa, Seiji; Narita, Hiroshi; Miyake, Shiro

    2015-07-22

    An immunosensor based on surface plasmon resonance (SPR-sensor) was developed to analyze chlorothalonil residues and maximum residue limits (MRLs; 0.5-50 mg/kg) in vegetables in Japan. Conjugates of N-(pentachlorophenoxyacetyl)glycine and bovine serum albumin were covalently coated on the sensor chip. The SPR-sensor quantitatively determined chlorothalonil at concentrations ranging from 8.0 to 44 ng/mL, using TPN9A, a monoclonal antibody to chlorothalonil. The 50% inhibition concentration was 25 ng/mL. The reactivity was 10-fold lower than that of indirect competitive enzyme-linked immunosorbent assay (ic-ELISA). However, the SPR-sensor could determine chlorothalonil residues in vegetables at concentrations around the above MRLs. Chlorothalonil spiked in vegetables was recovered at 90-118% within 1 day and at 90-115% across 3 days, correlating with HPLC results. The sensor showed good performance for chlorothalonil residue analysis in vegetables with rapid determination, although the sensitivity and the cross-reactivity were less effective than with the ic-ELISA. PMID:26172540

  18. A Renewable Electrochemical Magnetic Immunosensor Based on Gold Nanoparticle Labels

    SciTech Connect

    Liu, Guodong; Lin, Yuehe

    2005-05-24

    A particle-based renewable electrochemical magnetic immunosensor was developed by using magnetic beads and a gold nanoparticle label. Anti-IgG antibody-modified magnetic beads were attached to a renewable carbon paste transducer surface by magnets that were fixed inside the sensor. A gold nanoparticle label was capsulated to the surface of magnetic beads by sandwich immunoassay. Highly sensitive electrochemical stripping analysis offers a simple and fast method to quantify the capatured gold nanoparticle tracer and avoid the use of an enzyme label and substrate. The stripping signal of gold nanoparticle is related to the concentration of target IgG in the sample solution. A transmission electron microscopy image shows that the gold nanoparticles were successfully capsulated to the surface of magnetic beads through sandwich immunoreaction events. The parameters of immunoassay, including the loading of magnetic beads, the amount of gold nanoparticle conjugate, and the immunoreaction time, were optimized. The detection limit of 0.02 μg ml-1of IgG was obtained under optimum experimental conditions. Such particle-based electrochemical magnetic immunosensors could be readily used for simultaneous parallel detection of multiple proteins by using multiple inorganic metal nanoparticle tracers and are expected to open new opportunities for disease diagnostics and biosecurity.

  19. 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

  20. Sensitive electrochemical immunosensor based on three-dimensional nanostructure gold electrode

    PubMed Central

    Zhong, Guangxian; Lan, Ruilong; Zhang, Wenxin; Fu, Feihuan; Sun, Yiming; Peng, Huaping; Chen, Tianbin; Cai, Yishan; Liu, Ailin; Lin, Jianhua; Lin, Xinhua

    2015-01-01

    A sensitive electrochemical immunosensor was developed for detection of alpha-fetoprotein (AFP) based on a three-dimensional nanostructure gold electrode using a facile, rapid, “green” square-wave oxidation-reduction cycle technique. The resulting three-dimensional gold nanocomposites were characterized by scanning electron microscopy and cyclic voltammetry. A “sandwich-type” detection strategy using an electrochemical immunosensor was employed. Under optimal conditions, a good linear relationship between the current response signal and the AFP concentrations was observed in the range of 10–50 ng/mL with a detection limit of 3 pg/mL. This new immunosensor showed a fast amperometric response and high sensitivity and selectivity. It was successfully used to determine AFP in a human serum sample with a relative standard deviation of <5% (n=5). The proposed immunosensor represents a significant step toward practical application in clinical diagnosis and monitoring of prognosis. PMID:25834434

  1. Conductimetric immunosensor based on poly(3,4-ethylenedioxythiophene).

    PubMed

    Kanungo, Mandakini; Srivastava, Divesh N; Kumar, Anil; Contractor, A Q

    2002-04-01

    A conductimetric reagentless immunosensor using the biospecific binding pair of goat antirabbit IgG and rabbit IgG has been designed and fabricated using poly (3,4-ethylenedioxythiophene) as the immobilization matrix-cumtransducer. PMID:12119672

  2. SPR based immunosensor for detection of Legionella pneumophila in water samples

    NASA Astrophysics Data System (ADS)

    Enrico, De Lorenzis; Manera, Maria G.; Montagna, Giovanni; Cimaglia, Fabio; Chiesa, Maurizio; Poltronieri, Palmiro; Santino, Angelo; Rella, Roberto

    2013-05-01

    Detection of legionellae by water sampling is an important factor in epidemiological investigations of Legionnaires' disease and its prevention. To avoid labor-intensive problems with conventional methods, an alternative, highly sensitive and simple method is proposed for detecting L. pneumophila in aqueous samples. A compact Surface Plasmon Resonance (SPR) instrumentation prototype, provided with proper microfluidics tools, is built. The developed immunosensor is capable of dynamically following the binding between antigens and the corresponding antibody molecules immobilized on the SPR sensor surface. A proper immobilization strategy is used in this work that makes use of an important efficient step aimed at the orientation of antibodies onto the sensor surface. The feasibility of the integration of SPR-based biosensing setups with microfluidic technologies, resulting in a low-cost and portable biosensor is demonstrated.

  3. Fabrication of a label-free plasmon immunosensor based on triangular silver nanoplates

    NASA Astrophysics Data System (ADS)

    Dong, Peipei; Lin, Yuanyuan; Di, Junwei

    2013-08-01

    In this work, we have firstly electrodeposited small gold seeds (average diameter of ~40 nm) onto transparent indium tin oxide (ITO) thin film coated glass. Then silver triangular nanoplates with edge lengths of ~200 nm were fabricated using seed-mediated growth method. The localized surface plasmon resonance (LSPR) peak was located at ~700 nm. Finally, a label-free plasmon immunosensor was prepared by directly immobilizing goat anti-mouse IgG onto silver surface. The performance of the LSPR immunosensor was investigated. The red-shift of the biosensor was linearly proportional to mouse IgG concentration ranged from 5 ng/mL to 500 ng/mL, with a detection limit of 2 ng/mL. The label-free immunosensor was simple, sensitive and selective.

  4. Development of an Immunosensor Based on Layered Double Hydroxides for MMR Cancer Biomarker Detection.

    PubMed

    Hammami, M; Soussou, A; Idoudi, F; Cohen-Bouhacina, T; Bouhaouala-Zahar, B; Baccar, Z M

    2015-10-01

    As a potential biomarker for the investigation of cancer inflammatory profiles, macrophage mannose receptor (MMR, CD206) is herein selected to develop an immunosensor based on layered double hydroxide (LDH). Like an endocyte C-type lectin receptor, MMR plays an important role in immune homeostasis by scavenging unwanted mannose glycoproteins. It attracts a progressive attention thanks to its particularly high expression within the tumor microenvironment. There is a great of interest to develop an immunosensor based on an antibody specific to MMR for detection of stroma versus tumor cells. In this work, we studied the feasibility of high sensitive MMR cancer Screen Printed Electrode (SPE) immunosensor. Working electrode of commercialized SPE was modified by immobilization of specific antibody (anti-MMR) into thin layer of LDH nanomaterials. Structural, morphological, and surface properties of LDHs were studied by X-Ray diffraction, atomic force microscopy and Infrared spectroscopy in ATR. Cyclic Voltammetry technique was used to study interaction between the human recombinant MMR protein (rHu-MMR, NSO derived) and an immobilized antibody into developed immunosensor. High specific response of -11.72 μA/ng.mL(-1) (with a correlation coefficient of R(2)=0.994 ) were obtained in linear range of 0.05 ng/mL to 10.0 ng/mL of specific recombinant antigen. The limit of detection (LOD) was less than 15.0 pg/mL. From these attractive results, the feasibility of an electrochemical immunosensor for cancer was proved. Additional experiments to study stability and reproducibility the immunosensor should be completed in perspective to use these anti-MMR based immunosensors for sensing human MMR in patient biopsies and sera. PMID:26316191

  5. Electrochemical Immunosensor Based on Polythionine/Gold Nanoparticles for the Determination of Aflatoxin B1

    PubMed Central

    Owino, Joseph H.O.; Arotiba, Omotayo A.; Hendricks, Nicolette; Songa, Everlyne A.; Jahed, Nazeem; Waryo, Tesfaye T.; Ngece, Rachel F.; Baker, Priscilla G.L.; Iwuoha, Emmanuel I.

    2008-01-01

    An aflatoxin B1 (AFB1) electrochemical immunosensor was developed by the immobilisation of aflatoxin B1-bovine serum albumin (AFB1-BSA) conjugate on a polythionine (PTH)/gold nanoparticles (AuNP)-modified glassy carbon electrode (GCE). The surface of the AFB1-BSA conjugate was covered with horseradish peroxidase (HRP), in order to prevent non-specific binding of the immunosensors with ions in the test solution. The AFB1 immunosensor exhibited a quasi-reversible electrochemistry as indicated by a cyclic voltammetric (CV) peak separation (ΔEp) value of 62 mV. The experimental procedure for the detection of AFB1 involved the setting up of a competition between free AFB1 and the immobilised AFB1-BSA conjugate for the binding sites of free anti-aflatoxin B1 (anti-AFB1) antibody. The immunosensor's differential pulse voltammetry (DPV) responses (peak currents) decreased as the concentration of free AFB1 increased within a dynamic linear range (DLR) of 0.6 - 2.4 ng/mL AFB1 and a limit of detection (LOD) of 0.07 ng/mL AFB1. This immunosensing procedure eliminates the need for enzyme-labeled secondary antibodies normally used in conventional ELISA–based immunosensors.

  6. Single-domain antibody based thermally stable electrochemical immunosensor.

    PubMed

    Singh, Aparajita; Pasha, Syed Khalid; Manickam, Pandiaraj; Bhansali, Shekhar

    2016-09-15

    Conventional monoclonal and polyclonal antibodies are sensitive to changes in environmental factors such as temperature, pH, humidity, etc. This limits the current cost-effective and portable electrochemical immunosensors in harsh environments. Using Ricin Chain-A, a naturally occurring toxin, as a model analyte we report fabrication of a thermally stable electrochemical immunosensor. Single-domain antibodies (sdAb) or nanobodies have been employed as recognition elements for direct detection of Ricin at temperatures great than 4°C. Immunosensor fabricated using the conventional Ricin monoclonal and polyclonal antibodies have also been demonstrated for comparison. In the case of sdAb immunosensor, Ricin was detected in a linear range of 1log(fg/mL)-1log(μg/mL) with a sensitivity of 0.07μA/log(g/mL)/cm(2) using cyclic voltammetry. The fabricated miniaturized sensors have demonstrated higher shelf life and stability at temperatures up to 40°C. Therefore these electrochemical sensors can be integrated as a part of a portable device for point-of-care immunosensing. PMID:27125838

  7. A novel electrochemical immunosensor based on magnetosomes for detection of staphylococcal enterotoxin B in milk.

    PubMed

    Wu, Longyun; Gao, Bo; Zhang, Fang; Sun, Xiulan; Zhang, Yinzhi; Li, Zaijun

    2013-03-15

    In this paper, a novel electrochemical immunosensor to detect staphylococcal enterotoxin B based on bio-magnetosomes, polyaniline nano-gold composite and 1,2-dimethyl-3-butylimidazolium hexafluorophosphate ionic liquid, was developed, and found to exhibit high sensitivity and stability. The specific antibody to staphylococcal enterotoxin B conjugated with the magnetosomes showed rapid immunoreactions and good dispersion, which contributed to the formation of a nanostructurally smooth and dense film on the surface of a gold electrode. Polyaniline nano-gold composite and 1,2-dimethyl-3-butylimidazolium hexafluorophosphate ionic liquid were used to modify the electrode as mediators to improve the electron transfer and offer an excellent biocompatible microenvironment for the antibody to retain its activity to enhance the response of the electrochemical sensor. Under optimal conditions, the developed immunosensor showed a good linear response in the range from 0.05 to 5 ng/mL (R(2)=0.9957) with a detection limit as low as 0.017 ng/mL, compared with the one without magnetosomes (0.05-5 ng/mL, 0.033 ng/mL), this developed immunosensor showed a wider response range and a reduced detection limit. And a good specificity with little adsorption to staphylococcal enterotoxin A, C and Na(+), K(+), Ca(2+) was obtained. Moreover, the immunosensor exhibited a good long-time stability at 4 °C reaching up to 60 days, which showed a relatively long working life. Meanwhile the immunosensor could be regenerated four times using NaOH elution. The sensor also displayed a good repeatability with a relative standard deviation of 5.02% for staphylococcal enterotoxin B detection (1 ng/mL, n=9). Furthermore, high recoveries in milk samples from 81% to 118% were achieved and successfully applied to milk sample detection. The obtained results demonstrate that the developed electrochemical immunosensor is a promising tool for the detection of staphylococcal enterotoxin B in food. PMID:23598138

  8. 3D label-free prostate specific antigen (PSA) immunosensor based on graphene-gold composites.

    PubMed

    Jang, Hee Dong; Kim, Sun Kyung; Chang, Hankwon; Choi, Jeong-Woo

    2015-01-15

    Highly sensitive and label-free detection of the prostate specific antigen (PSA) remains a challenge in the diagnosis of prostate cancer. Here, a novel three-dimensional (3D) electrochemical immunosensor capable of sensitive and label-free detection of PSA is reported. This unique immunosensor is equipped with a highly conductive graphene (GR)-based gold (Au) composite modified electrode. The GR-based Au composite is prepared using aerosol spray pyrolysis and the morphology of the composite is the shape of a crumpled GR ball decorated with Au nanoparticles. Unlike the previous research, this novel 3D immunosensor functions very well over a broad linear range of 0-10 ng/mL with a low detection limit of 0.59 ng/mL; furthermore, it exhibits a significantly increased electron transfer and high sensitivity toward PSA. The highest rate of current change with respect to the PSA concentration is 5 μA/(ng/mL). Satisfactory selectivity, reproducibility, and stability of the 3D immunosensor are also exhibited. PMID:25150936

  9. An amperometric immunosensor for osteoproteogerin based on gold nanoparticles deposited conducting polymer.

    PubMed

    Singh, Kanika; Rahman, Md Aminur; Son, Jung Ik; Kim, Kyung Chun; Shim, Yoon-Bo

    2008-06-15

    An amperometric immunosensor was fabricated for the detection of osteoproteogerin (OPG) by covalently immobilizing a monoclonal OPG antibody (anti-OPG) onto the gold nanoparticles (AuNPs) deposited functionalized conducting polymer (5,2':5',2''-terthiophene-3'-carboxylic acid). AuNPs were electrochemically deposited onto the conducting polymer using cyclic voltammetry. The particle size of deposited AuNPs was controlled by varying the scan rate and was characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The immobilization of anti-OPG was also confirmed using XPS. The principle of immunosensor was based on a competitive immunoassay between free-OPG and labeled-OPG for the active sites of anti-OPG. HRP was used as a label that electrochemically catalyzes the H(2)O(2) reduction. The catalytic reduction was monitored amperometrically at -0.4V vs. Ag/AgCl. The immunosensor showed a linear range between 2.5 and 25pg/ml and the detection limit was determined to be 2pg/ml. The proposed immunosensor was successfully applied for real human samples to detect OPG. PMID:18304799

  10. A novel nanoparticle-based disposable electrochemical immunosensor for diagnosis of exposure to toxic organophosphorus agents

    SciTech Connect

    Lu, Donglai; Wang, Jun; Wang, Limin; Du, Dan; Timchalk, Charles; Barry, Richard C.; Lin, Yuehe

    2011-11-15

    We present a novel disposable electrochemical immunosensor for highly selective and sensitive detection of organophosphorylated butyrylcholinesterase (OP-BChE), a specific biomarker for exposure to toxic organophosphorus agents. In our new approach, the zirconia nanoparticles (ZrO-2) were employed to selectively capture the OP moiety of OP-BChE adducts, and followed by quantum dot (QD)-tagged anti-BChE antibodies for amplified quantification. The captured CdSe-QD tags can be sensitively detected by stripping voltammetry using in situ bismuth-plating method. The OP agent, diisopropylfluorophosphate (DFP), was selected to prepare OP-BChE adducts in various matrices. The formation of OP-BChE adducts in plasma sample was confirmed using mass spectroscopy. The developed electrochemical immunosensor demonstrates a highly linear voltammetric response over the range of 0.1 to 30 nM OP-BChE. Moreover, the immunosensor has been successfully applied for the detection of OP-BChE adducts in the plasma samples. This novel nanoparticle-based electrochemical immunosensor thus provides an alternative way for designing simple, fast, sensitive, and cost-effective sensing platform for on-site screening/evaluating exposure to a variety of OP agents.

  11. 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

  12. 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. PMID:24840469

  13. Label-free C-reactive protein electronic detection with an electrolyte-gated organic field-effect transistor-based immunosensor.

    PubMed

    Magliulo, Maria; De Tullio, Donato; Vikholm-Lundin, Inger; Albers, Willem M; Munter, Tony; Manoli, Kyriaki; Palazzo, Gerardo; Torsi, Luisa

    2016-06-01

    In this contribution, we propose a label-free immunosensor, based on a novel type of electrolyte-gated field-effect transistor (EGOFET), for ultrasensitive detection of the C-reactive protein (CRP). The recognition layer of the biosensor is fabricated by physical adsorption of the anti-CRP monoclonal antibody onto a poly-3-hexyl thiophene (P3HT) organic semiconductor surface. A supplementary nonionic hydrophilic polymer is used as a blocking agent preventing nonspecific interactions and allowing a better orientation of the antibodies immobilized onto the P3HT surface. The whole biomolecule immobilization procedure does not require any pretreatment of the organic semiconductor surface, and the whole functionalization process is completed in less than 30 min. Surface plasmon resonance (SPR) measurements were performed to assess the amount of biomolecules physisorbed onto the P3HT and to evaluate the CRP binding proprieties of the deposited anti-CRP layer. A partial surface coverage of about 23 % of adsorbed antibody molecules was found to most efficiently sense the CRP. The electrical performance of the EGOFET immunosensor was comparable to that of a bare P3HT EGOFET device, and the obtained CRP calibration curve was linear over six orders of magnitude (from 4 pM to 2 μM). The relative standard deviation of the individual calibration points, measured on immunosensors fabricated on different chips, ranged between 1 and 14 %, and a detection limit of 2 pM (220 ng/L) was established. The novel electronic immunosensor is compatible with low-cost fabrication procedures and was successfully employed for the detection of the CRP biomarker in the clinically relevant matrix serum. Graphical abstract Schematic of the EGOFET immunosensor for CRP detection. The anti-CRP monoclonal antibody layer is physisorbed on the P3HT organic semiconductor and the CRP is directly measured by a label-free electronic EGOFET transducer. PMID:27032409

  14. A chitosan-Au-hyperbranched polyester nanoparticles-based antifouling immunosensor for sensitive detection of carcinoembryonic antigen.

    PubMed

    Sun, Chong; Ma, Lie; Qian, Qiuhui; Parmar, Soniya; Zhao, Wenbo; Zhao, Bo; Shen, Jian

    2014-09-01

    Analysts are always interested in finding new functional nanomaterials and devices with good properties for electrochemical sensor applications. In this paper, hyperbranched polyester nanoparticles with carboxylic acid functional groups (HBPE-CA NPs) were synthesized and combined with chitosan wrapped around Au nanoparticles (CS-Au NPs) to prepare a novel and sensitive electrochemical immunosensor by adsorption of carcinoembryonic antibody (anti-CEA) on the (HBPE-CA)/CS-Au NPs modified glass carbon electrode (GCE). Under the optimized conditions, the proposed immunosensor displayed a good amperometric response to carcinoembryonic antigen (CEA). Moreover, based on the antibiofouling properties, the immunosensor could be used for the direct detection of CEA in whole blood, and exhibited a wide detection range (1-10(7) fg mL(-1)), and a low detection limit of 0.251 fg mL(-1) (signal/noise = 3). Control experiments were also carried out by using ascorbic acid (AA), uric acid (UA), human immunoglobulin G (IgG), BSA and glucose in the absence of CEA. The good stability and repeatability of this immunosensor were also proven. Importantly, the results of the detection of clinical whole blood specimens with the proposed immunosensor showed good consistency with the data determined by enzyme-linked immunosorbent assay (ELISA) in serum samples. Furthermore, the developed immunosensor could provide a promising immunoassay strategy for clinical applications, since the values we measured in whole blood directly are likely closer to the real values. PMID:24957417

  15. Microfluidic and Label-Free Multi-Immunosensors Based on Carbon Nanotube Microelectrodes

    NASA Astrophysics Data System (ADS)

    Tsujita, Yuichi; Maehashi, Kenzo; Matsumoto, Kazuhiko; Chikae, Miyuki; Takamura, Yuzuru; Tamiya, Eiichi

    2009-06-01

    We fabricated microfluidic and label-free multi-immunosensors by the integration of carbon nanotube (CNT)-arrayed electrodes and microchannels with pneumatic micropumps made of poly(dimethylsiloxane). In the microfluidic systems, four kinds of sample solutions were transported from each liquid inlet to microchannels using six pneumatic micropumps. As a result, two kinds of antibodies were immobilized onto different CNT electrodes using the microfluidic systems. Next, two kinds of cancer markers, prostate specific antigen and human chorionic gonadotropin in phosphate buffer solution, were simultaneously detected by differential pulse voltammetry. Therefore, microfludic multi-immunosensors based on CNT electrodes and pneumatic micropumps are useful for the development of multiplex hand-held biosensors.

  16. Graphene-based immunosensor for electrochemical quantification of phosphorylated p53 (S15)

    SciTech Connect

    Xie, Yunying; Chen, Aiqiong; Du, Dan; Lin, Yuehe

    2011-08-01

    We reported a graphene-based immunosensor for electrochemical quantification of phosphorylated p53 on serine 15 (phospho-p5315), a potential biomarker of gamma-radiation exposure. The principle is based on sandwich immunoassay and the resulting immunocomplex is formed among phospho-p53 capture antibody, phospho-p5315 antigen, biotinylated phospho-p5315 detection antibody and horseradish peroxidase (HRP)-labeled streptavidin. The introduced HRP results in an electrocatalytic response to reduction of hydrogen peroxide in the presence of thionine. Graphene served as sensor platform not only promotes electron transfer, but also increases the surface area to introduce a large amount of capture antibody, thus increasing the detection sensitivity. The experimental conditions including blocking agent, immunoreaction time and substrate concentration have been optimized. Under the optimum conditions, the increase of response current is proportional to the phospho-p5315 concentration in the range of 0.2–10 ng mL-1, with the detection limit of 0.1 ng mL-1. The developed immunosensor exhibits acceptable stability and reproducibility and the assay results for phospho-p5315 are in good correlation with the known values. This easily fabricated immunosensor provides a new promising tool for analysis of phospho-p5315 and other phosphorylated proteins.

  17. A Fumonisins Immunosensor Based on Polyanilino-Carbon Nanotubes Doped with Palladium Telluride Quantum Dots

    PubMed Central

    Masikini, Milua; Mailu, Stephen N.; Tsegaye, Abebaw; Njomo, Njagi; Molapo, Kerileng M.; Ikpo, Chinwe O.; Sunday, Christopher Edozie; Rassie, Candice; Wilson, Lindsay; Baker, Priscilla G. L.; Iwuoha, Emmanuel I.

    2015-01-01

    An impedimetric immunosensor for fumonisins was developed based on poly(2,5-dimethoxyaniline)-multi-wall carbon nanotubes doped with palladium telluride quantum dots onto a glassy carbon surface. The composite was assembled by a layer-by-layer method to form a multilayer film of quantum dots (QDs) and poly(2,5-dimethoxyaniline)-multi-wall carbon nanotubes (PDMA-MWCNT). Preparation of the electrochemical immunosensor for fumonisins involved drop-coating of fumonisins antibody onto the composite modified glassy carbon electrode. The electrochemical impedance spectroscopy response of the FB1 immunosensor (GCE/PT-PDMA-MWCNT/anti-Fms-BSA) gave a linear range of 7 to 49 ng L−1 and the corresponding sensitivity and detection limits were 0.0162 kΩ L ng−1 and 0.46 pg L−1, respectively, hence the limit of detection of the GCE/PT-PDMA-MWCNT immunosensor for fumonisins in corn certified material was calculated to be 0.014 and 0.011 ppm for FB1, and FB2 and FB3, respectively. These results are lower than those obtained by ELISA, a provisional maximum tolerable daily intake (PMTDI) for fumonisins (the sum of FB1, FB2, and FB3) established by the Joint FAO/WHO expert committee on food additives and contaminants of 2 μg kg−1 and the maximum level recommended by the U.S. Food and Drug Administration (FDA) for protection of human consumption (2–4 mg L−1). PMID:25558993

  18. Troponin T immunosensor based on liquid crystal and silsesquioxane-supported gold nanoparticles.

    PubMed

    Zapp, Eduardo; da Silva, Paulo Sérgio; Westphal, Eduard; Gallardo, Hugo; Spinelli, Almir; Vieira, Iolanda Cruz

    2014-09-17

    A nanostructured immunosensor based on the liquid crystal (E)-1-decyl-4-[(4-decyloxyphenyl)diazenyl]pyridinium bromide (Br-Py) and gold nanoparticles supported by the water-soluble hybrid material 3-n-propyl-4-picolinium silsesquioxane chloride (AuNP-Si4Pic(+)Cl(-)) was built for the detection of troponin T (cTnT), a cardiac marker for acute myocardial infarction (AMI). The functionalized nanostructured surface was used to bind anti-cTnT monoclonal antibodies through electrostatic interaction. The immunosensor (ab-cTnT/AuNP-Si4Pic(+)Cl(-)/Br-Py/GCE) surface was characterized by microscopy techniques. The electrochemical behavior of the immunosensor was studied by cyclic voltammetry and electrochemical impedance spectroscopy. A calibration curve was obtained by square-wave voltammetry. The immnunosensor provided a limit of detection of 0.076 ng mL(-1) and a linear range between 0.1 and 0.9 ng mL(-1) (appropriate for AMI diagnosis). PMID:25111622

  19. Nanoparticle-based immunosensor with apoferritin templated metallic phosphate label for quantification of phosphorylated acetylcholinesterase

    SciTech Connect

    Du, Dan; Chen, Aiqiong; Xie, Yunying; Zhang, Aidong; Lin, Yuehe

    2011-05-15

    A new sandwich-like electrochemical immunosensor has been developed for quantification of organophosphorylated acetylcholinesterase (OP-AChE), an exposure biomarker of organophosphate pesticides and nerve agents. Zirconia nanoparticles (ZrO2 NPs) were anchored on a screen printed electrode (SPE) to preferably capture OP-AChE adducts by metal chelation with phospho-moieties, which was selectively recognized by lead phosphate-apoferritin labeled anti-AChE antibody (LPA-anti-AChE). The sandwich-like immunoreactions were performed among ZrO2 NPs, OP-AChE and LPA-anti-AChE to form ZrO2/OP-AChE/LPA-anti-AChE complex and the released lead ions were detected on a disposable SPE. The binding affinity was investigated by both square wave voltammetry (SWV) and quartz crystal microbalance (QCM) measurements. The proposed immunosensor yielded a linear response current over a broad OP-AChE concentrations range from 0.05 nM to 10 nM, with detection limit of 0.02 nM, which has enough sensitivity for monitoring of low-dose exposure to OPs. This method avoids the drawback of unavailability of commercial OP-specific antibody as well as amplifies detection signal by using apoferritin encoded metallic phosphate nanoparticle tags. This nanoparticle-based immunosensor offers a new method for rapid, sensitive, selective and inexpensive quantification of phosphorylated adducts for monitoring of OP pesticides and nerve agents exposures.

  20. Sensitive sandwich electrochemical immunosensor for alpha fetoprotein based on prussian blue modified hydroxyapatite.

    PubMed

    Dai, Yuxue; Cai, Yanyan; Zhao, Yanfang; Wu, Dan; Liu, Bao; Li, Ru; Yang, Minghui; Wei, Qin; Du, Bin; Li, He

    2011-10-15

    A sandwich electrochemical immunosensor for the sensitive determination of alpha fetoprotein (AFP) has been fabricated. Prussian blue modified hydroxyapatite (PB@HAP) was firstly prepared and used as electrochemical label due to the wonderful conductivity and good biocompatibility of HAP. The results proved that the immunosensor fabricated using the label based on PB@HAP loaded with horse radish peroxidase (HRP) and secondary anti-AFP antibody (Ab(2)) (PB@HAP-HRP-Ab(2)) had high sensitivity, and the sensitivity of the label PB@HAP-HRP-Ab(2) was much higher than labels of PB@HAP-Ab(2), PB-HRP-Ab(2) and HAP-HRP-Ab(2). The mixture of graphene sheet (GS) and thionine (TH) was not only used to immobilize anti-AFP antibody (Ab(1)) but also took part in the signal amplification. The amperometric signal increased linearly with AFP concentration in the range of 0.02-8 ng/mL with a low detection limit of 9 pg/mL. The immunosensor had the advantages of high sensitivity, good selectivity and good stability, and was applied to the analysis of AFP in serum sample with satisfactory results. Due to the low-cost and easy synthesis of PB@HAP, the screen-printed electrodes could be used instead of the bare glass carbon electrode in order to achieve mass production. In addition, it had potential application in the detection of other tumor markers. PMID:21802277

  1. Poly(pyrrole-co-pyrrole propylic acid) film and its application in label-free surface plasmon resonance immunosensors.

    PubMed

    Hu, Weihua; Li, Chang Ming; Dong, Hua

    2008-12-01

    In this work, surface plasmon resonance (SPR) was used to study protein immobilization on poly(pyrrole-co-pyrrole propylic acid) (PPy/PPa) for immunosensing applications. SPR was employed to in situ monitor the electropolymerization process and to control thickness of the PPy/PPa copolymer film. Goat IgG as a model protein was covalently immobilized on the carboxyl-containing film through EDC/NHS as the coupling reagents. The effect of pyrrole propylic acid (Pa) proportion in the deposition solution on the protein immobilization capability was systemically investigated. The immobilization efficiency was demonstrated by a label-free SPR immunosensor. The heterogeneous kinetics of the immune reaction was discussed. This work could provide a facile method to immobilize proteins on an electrode surface by electropolymerized copolymer, and renders a universal approach to in situ study the protein immobilization process and sensing kinetics for scientific insights of the heteroimmunosensing scheme particularly in surface chemistry and molecular biology for further improvement of immunosensors. PMID:19068327

  2. A new method for non-labeling attomolar detection of diseases based on an individual gold nanorod immunosensor.

    PubMed

    Truong, Phuoc Long; Cao, Cuong; Park, Sungho; Kim, Moonil; Sim, Sang Jun

    2011-08-01

    Herein, we present the use of a single gold nanorod sensor for detection of diseases on an antibody-functionalized surface, based on antibody-antigen interaction and the localized surface plasmon resonance (LSPR) λ(max) shifts of the resonant Rayleigh light scattering spectra. By replacing the cetyltrimethylammonium bromide (CTAB), a tightly packed self-assembled monolayer of HS(CH(2))(11)(OCH(2)CH(2))(6)OCH(2)COOH(OEG(6)) has been successfully formed on the gold nanorod surface prior to the LSPR sensing, leading to the successful fabrication of individual gold nanorod immunosensors. Using prostate specific antigen (PSA) as a protein biomarker, the lowest concentration experimentally detected was as low as 111 aM, corresponding to a 2.79 nm LSPR λ(max) shift. These results indicate that the detection platform is very sensitive and outperforms detection limits of commercial tests for PSA so far. Correlatively, its detection limit can be equally compared to the assays based on DNA biobarcodes. This study shows that a gold nanorod has been used as a single nanobiosensor to detect antigens for the first time; and the detection method based on the resonant Rayleigh scattering spectrum of individual gold nanorods enables a simple, label-free detection with ultrahigh sensitivity. PMID:21670836

  3. A Label-Free Electrochemical Immunosensor for Carbofuran Detection Based on a Sol-Gel Entrapped Antibody

    PubMed Central

    Sun, Xia; Du, Shuyuan; Wang, Xiangyou; Zhao, Wenping; Li, Qingqing

    2011-01-01

    In this study, an anti-carbofuran monoclonal antibody (Ab) was immobilized on the surface of a glassy carbon electrode (GCE) using silica sol-gel (SiSG) technology. Thus, a sensitive, label-free electrochemical immunosensor for the direct determination of carbofuran was developed. The electrochemical performance of immunoreaction of antigen with the anti-carbofuran monoclonal antibody was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), in which phosphate buffer solution containing [Fe(CN)6]3−/4− was used as the base solution for test. Because the complex formed by the immunoreaction hindered the diffusion of [Fe(CN)6]3−/4− on the electrode surface, the redox peak current of the immunosensor in the CV obviously decreased with the increase of the carbofuran concentration. The pH of working solution, the concentration of Ab and the incubation time of carbofuran were studied to ensure the sensitivity and conductivity of the immunosensor. Under the optimal conditions, the linear range of the proposed immunosensor for the determination of carbofuran was from 1 ng/mL to 100 μg/mL and from 50 μg/mL to 200 μg/mL with a detection limit of 0.33 ng/mL (S/N = 3). The proposed immunosensor exhibited good high sensitivity and stability, and it was thus suitable for trace detection of carbofuran pesticide residues. PMID:22163709

  4. A novel immunosensor for detecting toxoplasma gondii-specific IgM based on goldmag nanoparticles and graphene sheets.

    PubMed

    Jiang, Shuting; Hua, Erhui; Liang, Mo; Liu, Bei; Xie, Guoming

    2013-01-01

    A novel electrochemical immunosensor for detecting toxoplasma gondii-specific IgM (Tg-IgM) was constructed based on goldmag (Au-Fe(3)O(4)) nanoparticles and graphene sheets (GS). Thionine (Thi), as a mediator, was first electropolymerized on a nafion-GS (Nf-GS) modified electrode. Subsequently, gold nanoparticles (AuNPs) were attached onto the poly-thionine film through π-stacking interactions, and then were used to immobilize toxoplasma gondii antigen (Tg-Ag) for immunosensor fabrication. A sandwich-type immunoassay for Tg-IgM was performed using Au-Fe(3)O(4) labeled anti-IgM-horseradish peroxidase (HRP) as trace label. Electrochemical detection was carried out in the presence of H(2)O(2) as HRP substrate. Using Au-Fe(3)O(4) provided a simple, non-chemical damaging method for regeneration, and enhanced the HRP reduction ability toward H(2)O(2). The AuNPs/Thi/Nf-GS nanocomposite also had good conductivity and biocompatibility, which effectively improved the immunosensor sensitivity. Under optimal conditions, the immunosensor can detect Tg-IgM in two linear ranges from 0.0375 to 1.2 AU mL(-1) and from 2.0 to 18 AU mL(-1) with a detection limit of 0.016 AU mL(-1) (S/N=3). The immunosensor exhibited good reproducibility, stability, and selectivity as well. PMID:23010058

  5. Automated microfluidic platform of bead-based electrochemical immunosensor integrated with bioreactor for continual monitoring of cell secreted biomarkers

    PubMed Central

    Riahi, Reza; Shaegh, Seyed Ali Mousavi; Ghaderi, Masoumeh; Zhang, Yu Shrike; Shin, Su Ryon; Aleman, Julio; Massa, Solange; Kim, Duckjin; Dokmeci, Mehmet Remzi; Khademhosseini, Ali

    2016-01-01

    There is an increasing interest in developing microfluidic bioreactors and organs-on-a-chip platforms combined with sensing capabilities for continual monitoring of cell-secreted biomarkers. Conventional approaches such as ELISA and mass spectroscopy cannot satisfy the needs of continual monitoring as they are labor-intensive and not easily integrable with low-volume bioreactors. This paper reports on the development of an automated microfluidic bead-based electrochemical immunosensor for in-line measurement of cell-secreted biomarkers. For the operation of the multi-use immunosensor, disposable magnetic microbeads were used to immobilize biomarker-recognition molecules. Microvalves were further integrated in the microfluidic immunosensor chip to achieve programmable operations of the immunoassay including bead loading and unloading, binding, washing, and electrochemical sensing. The platform allowed convenient integration of the immunosensor with liver-on-chips to carry out continual quantification of biomarkers secreted from hepatocytes. Transferrin and albumin productions were monitored during a 5-day hepatotoxicity assessment in which human primary hepatocytes cultured in the bioreactor were treated with acetaminophen. Taken together, our unique microfluidic immunosensor provides a new platform for in-line detection of biomarkers in low volumes and long-term in vitro assessments of cellular functions in microfluidic bioreactors and organs-on-chips. PMID:27098564

  6. Automated microfluidic platform of bead-based electrochemical immunosensor integrated with bioreactor for continual monitoring of cell secreted biomarkers.

    PubMed

    Riahi, Reza; Shaegh, Seyed Ali Mousavi; Ghaderi, Masoumeh; Zhang, Yu Shrike; Shin, Su Ryon; Aleman, Julio; Massa, Solange; Kim, Duckjin; Dokmeci, Mehmet Remzi; Khademhosseini, Ali

    2016-01-01

    There is an increasing interest in developing microfluidic bioreactors and organs-on-a-chip platforms combined with sensing capabilities for continual monitoring of cell-secreted biomarkers. Conventional approaches such as ELISA and mass spectroscopy cannot satisfy the needs of continual monitoring as they are labor-intensive and not easily integrable with low-volume bioreactors. This paper reports on the development of an automated microfluidic bead-based electrochemical immunosensor for in-line measurement of cell-secreted biomarkers. For the operation of the multi-use immunosensor, disposable magnetic microbeads were used to immobilize biomarker-recognition molecules. Microvalves were further integrated in the microfluidic immunosensor chip to achieve programmable operations of the immunoassay including bead loading and unloading, binding, washing, and electrochemical sensing. The platform allowed convenient integration of the immunosensor with liver-on-chips to carry out continual quantification of biomarkers secreted from hepatocytes. Transferrin and albumin productions were monitored during a 5-day hepatotoxicity assessment in which human primary hepatocytes cultured in the bioreactor were treated with acetaminophen. Taken together, our unique microfluidic immunosensor provides a new platform for in-line detection of biomarkers in low volumes and long-term in vitro assessments of cellular functions in microfluidic bioreactors and organs-on-chips. PMID:27098564

  7. Ultrasensitive electrochemical immunosensor based on orderly oriented conductive wires for the detection of human monocyte chemotactic protein-1 in serum.

    PubMed

    Li, Yuliang; He, Junlin; Xia, Chunyong; Gao, Liuliu; Yu, Chao

    2015-08-15

    For the first time, a simple, ultrasensitive and label-free electrochemical monocyte chemotactic protein-1 (MCP-1) immunosensor based on orderly oriented conductive wires has been developed. A conductive wire, which is similar to an electron-conducting tunnel, was designed with Au nanoparticles (AuNPs) joined to Au@Pt core-shell microspheres via a cysteamine (CA) crosslinker. To enhance the sensitivity of the immunosensor, Au nanoparticles were electrodeposited onto the gold electrode, and CA was self-assembled via strong Au-S covalent bonds, providing an appropriate surface and promoting electron transfer. Next, Au@Pt core-shell microspheres with large surface area were grafted onto the modified electrode to immobilize more MCP-1 antibodies. MCP-1 is an initiating factor and biomarker of atherosclerotic diseases. Under optimal experimental conditions, differential pulse voltammetry (DPV) current changes were used to detect MCP-1 with a broad linear range of 0.09-360 pg mL(-1) and a low detection limit of 0.03 pg mL(-1) (S/N=3). The proposed immunosensor exhibited good selectivity, reproducibility and reusability. When applied to spiked serum samples, the data for the developed immunosensor were in agreement with an enzyme linked immunosorbent assay, suggesting that the electrochemical immunosensor would be suitable for practical detection. PMID:25845330

  8. Automated microfluidic platform of bead-based electrochemical immunosensor integrated with bioreactor for continual monitoring of cell secreted biomarkers

    NASA Astrophysics Data System (ADS)

    Riahi, Reza; Shaegh, Seyed Ali Mousavi; Ghaderi, Masoumeh; Zhang, Yu Shrike; Shin, Su Ryon; Aleman, Julio; Massa, Solange; Kim, Duckjin; Dokmeci, Mehmet Remzi; Khademhosseini, Ali

    2016-04-01

    There is an increasing interest in developing microfluidic bioreactors and organs-on-a-chip platforms combined with sensing capabilities for continual monitoring of cell-secreted biomarkers. Conventional approaches such as ELISA and mass spectroscopy cannot satisfy the needs of continual monitoring as they are labor-intensive and not easily integrable with low-volume bioreactors. This paper reports on the development of an automated microfluidic bead-based electrochemical immunosensor for in-line measurement of cell-secreted biomarkers. For the operation of the multi-use immunosensor, disposable magnetic microbeads were used to immobilize biomarker-recognition molecules. Microvalves were further integrated in the microfluidic immunosensor chip to achieve programmable operations of the immunoassay including bead loading and unloading, binding, washing, and electrochemical sensing. The platform allowed convenient integration of the immunosensor with liver-on-chips to carry out continual quantification of biomarkers secreted from hepatocytes. Transferrin and albumin productions were monitored during a 5-day hepatotoxicity assessment in which human primary hepatocytes cultured in the bioreactor were treated with acetaminophen. Taken together, our unique microfluidic immunosensor provides a new platform for in-line detection of biomarkers in low volumes and long-term in vitro assessments of cellular functions in microfluidic bioreactors and organs-on-chips.

  9. Solid-state voltammetry-based electrochemical immunosensor for Escherichia coli using graphene oxide-Ag nanoparticle composites as labels.

    PubMed

    Jiang, Xiaochun; Chen, Kun; Wang, Jing; Shao, Kang; Fu, Tao; Shao, Feng; Lu, Donglian; Liang, Jiangong; Foda, M Frahat; Han, Heyou

    2013-06-21

    A new electrochemical immunosensor based on solid-state voltammetry was fabricated for the detection of Escherichia coli (E. coli) by using graphene oxide-Ag nanoparticle composites (P-GO-Ag) as labels. To construct the platform, Au nanoparticles (AuNPs) were first self-assembled on an Au electrode surface through cysteamine and served as an effective matrix for antibody (Ab) attachment. Under a sandwich-type immunoassay format, the analyte and the probe (P-GO-Ag-Ab) were successively captured onto the immunosensor. Finally, the bonded AgNPs were detected through a solid-state redox process in 0.2 M of KCl solution. Combining the advantages of the high-loading capability of graphene oxide with promoted electron-transfer rate of AuNPs, this immunosensor produced a 26.92-fold signal enhancement compared with the unamplified protocol. Under the optimal conditions, the immunosensor exhibited a wide linear dependence on the logarithm of the concentration of E. coli ranging from 50 to 1.0 × 10(6) cfu mL(-1) with a detection limit of 10 cfu mL(-1). Moreover, as a practical application, the proposed immunosensor was used to monitor E. coli in lake water with satisfactory results. PMID:23662298

  10. A Label-Free Immunosensor for Ultrasensitive Detection of Ketamine Based on Quartz Crystal Microbalance

    PubMed Central

    Yang, Ya; Tu, Yifeng; Wang, Xiaoshu; Pan, Jinyin; Ding, Yun

    2015-01-01

    In this study, we have developed a label-free immunosensor with the variation of resonance frequency (Δf) of a quartz crystal microbalance (QCM) as readout signal for ultrasensitive detection of Ketamine (KT). An optimized strategy for immobilization of KT antibody on the surface of the QCM chip was implemented via the self-assembly modification of 3-mercaptopropionic acid, and then activated with 1-ethyl-3- (3-dimethylaminoprophl) carbodiimide and n-hydroxysuccinimide. The specific affinity between the antibody and the antigen ensured a selective response toward KT. The Δf linearly related to the concentration of KT in the range of 1 to 40 pg/mL, with a detection limit of 0.86 pg/mL (S/N = 3). The obtained immunosensor was applied to detect the KT in spiked human urine without any pretreatment but dilution with recoveries from 91.8% to 108%. The developed sensor is promising to perform the portable or on-spot KT detection in clinic or forensic cases. PMID:25871722

  11. Carbon nanotubes-based chemiresistive immunosensor for small molecules: Detection of nitroaromatic explosives

    PubMed Central

    Park, Miso; Cella, Lakshmi N; Chen, Wilfred; Myung, Nosang V.

    2010-01-01

    In recent years, there has been a growing focus on use of one-dimensional (1-D) nanostructures, such as carbon nanotubes and nanowires, as transducer elements for label-free chemiresistive/field-effect transistor biosensors as they provide label-free and high sensitivity detection. While research to-date has elucidated the power of carbon nanotubes- and other 1-D nanostructure- based field effect transistors immunosensors for large charged macromolecules such as proteins and viruses, their application to small uncharged or charged molecules has not been demonstrated. In this paper we report a single-walled carbon nanotubes (SWNTs)-based chemiresistive immunosensor for label-free, rapid, sensitive and selective detection of 2,4,6-trinitrotoluene (TNT), a small molecule. The newly developed immunosensor employed a displacement mode/format in which SWNTs network forming conduction channel of the sensor was first modified with trinitrophenyl (TNP), an analog of TNT, and then ligated with the anti-TNP single chain antibody. Upon exposure to TNT or its derivatives the bound antibodies were displaced producing a large change, several folds higher than the noise, in the resistance/conductance of SWNTs giving excellent limit of detection, sensitivity and selectivity. The sensor detected between 0.5 ppb and 5000 ppb TNT with good selectivity to other nitroaromatic explosives and demonstrated good accuracy for monitoring TNT in untreated environmental water matrix. We believe this new displacement format can be easily generalized to other one-dimensional nanostructure-based chemiresistive immuno/affinity-sensors for detecting small and/or uncharged molecules of interest in environmental monitoring and health care. PMID:20688506

  12. A Nonenzymatic Electrochemical Immunosensor for Ultrasensitive Detection of Tumor Biomarkers Based on Palladium Nanoparticles Conjugated Reduced Graphene Nanosheets.

    PubMed

    Li, WenTing; Li, YiSong; Wu, YongKang; Liao, JinFeng; Qi, TingTing; Li, He; Li, Jun; Zhang, XiaoNing; Qian, ZhiYong

    2015-11-01

    A nonenzymatic electrochemical immunosensor based on palladium nanoparticles conjugated reduced graphene nanosheets (Pd-GS) for sensitive detection of cancer biomarker a-fetoprotein (AFP) is described. Primary antibody-AFP (Ab1) was immobilized onto the surface of reduced graphene nanosheets (rGO) through an amidation reaction between the carboxylic acid group of the rGO and the available amine groups of Ab1. Pd-GS which was prepared by one-spot synthesis is employed to immobilize secondary antibody (Ab2). The resulting Pd-GS-Ab2 conjugate was used as a label for the immunosensor to detect AFP. The amplified immunoassay exhibits high sensitivity, wide linear rang (0.01-10 ng/mL), low detection limit (3.0 pg/mL), acceptable stability and reproducibility. And such immunosensor also shows good recovery in the assay results for AFP in human serum samples. PMID:26554162

  13. Ceria Doped Zinc Oxide Nanoflowers Enhanced Luminol-Based Electrochemiluminescence Immunosensor for Amyloid-β Detection.

    PubMed

    Wang, Jing-Xi; Zhuo, Ying; Zhou, Ying; Wang, Hai-Jun; Yuan, Ruo; Chai, Ya-Qin

    2016-05-25

    In this work, ceria doped ZnO nanomaterials with flower-structure (Ce:ZONFs) were prepared to construct a luminol-based electrochemiluminescence (ECL) immunosensor for amyloid-β protein (Aβ) detection. Herein, carboxyl groups (-COOH) covered Ce:ZONFs were synthesized by a green method with lysine as reductant. After that, Ce:ZONFs-based ECL nanocomposite was prepared by combining the luminophore of luminol and Ce:ZONFs via amidation and physical absorption. Luminol modified on Ce:ZONFs surface could generate a strong ECL signal under the assistance of reactive oxygen species (ROSs) (such as OH(•) and O2(•-)), which were produced by a catalytic reaction between Ce:ZONFs and H2O2. It was worth noticing that a quick Ce(4+) ↔ Ce(3+) reaction in this doped material could increase the rate of electron transfer to realize the signal amplification. Subsequently, the luminol functionalized Ce:ZONFs (Ce:ZONFs-Lum) were covered by secondary antibody (Ab2) and glucose oxidase (GOD), respectively, to construct a novel Ab2 bioconjugate (Ab2-GOD@Ce:ZONFs-Lum). The wire-structured silver-cysteine complex (AgCys NWs) with a large number of -COOH, which was synthesized by AgNO3 and l-cysteine, was used as substrate of the immunosensor to capture the primary antibody (Ab1). Under the optimal conditions, this proposed ECL immunosensor had exhibited high sensitivity for Aβ detection with a wide linear range from 80 fg/mL to 100 ng/mL and an ultralow detection limit of 52 fg/mL. Meanwhile, this biosensor had good specificity for Aβ, indicating that the provided strategy had a promising potential in the detection of Aβ. PMID:27145690

  14. 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. PMID:25629216

  15. Electrochemical signal amplification for immunosensor based on 3D interdigitated array electrodes.

    PubMed

    Han, Donghoon; Kim, Yang-Rae; Kang, Chung Mu; Chung, Taek Dong

    2014-06-17

    We devised an electrochemical redox cycling based on three-dimensional interdigitated array (3D IDA) electrodes for signal amplification to enhance the sensitivity of chip-based immunosensors. The 3D IDA consists of two closely spaced parallel indium tin oxide (ITO) electrodes that are positioned not only on the bottom but also the ceiling, facing each other along a microfluidic channel. We investigated the signal intensities from various geometric configurations: Open-2D IDA, Closed-2D IDA, and 3D IDA through electrochemical experiments and finite-element simulations. The 3D IDA among the four different systems exhibited the greatest signal amplification resulting from efficient redox cycling of electroactive species confined in the microchannel so that the faradaic current was augmented by a factor of ∼100. We exploited the enhanced sensitivity of the 3D IDA to build up a chronocoulometric immunosensing platform based on the sandwich enzyme-linked immunosorbent assay (ELISA) protocol. The mouse IgGs on the 3D IDA showed much lower detection limits than on the Closed-2D IDA. The detection limit for mouse IgG measured using the 3D IDA was ∼10 fg/mL, while it was ∼100 fg/mL for the Closed-2D IDA. Moreover, the proposed immunosensor system with the 3D IDA successfully worked for clinical analysis as shown by the sensitive detection of cardiac troponin I in human serum down to 100 fg/mL. PMID:24842332

  16. Magnetic beads-based electrochemical immunosensor for monitoring allergenic food proteins.

    PubMed

    Čadková, Michaela; Metelka, Radovan; Holubová, Lucie; Horák, Daniel; Dvořáková, Veronika; Bílková, Zuzana; Korecká, Lucie

    2015-09-01

    Screen-printed platinum electrodes as transducer and magnetic beads as solid phase were combined to develop a particle-based electrochemical immunosensor for monitoring the serious food allergen ovalbumin. The standard arrangement of enzyme-linked immunosorbent assay became the basis for designing the immunosensor. A sandwich-type immunocomplex was formed between magnetic particles functionalized with specific anti-ovalbumin immunoglobulin G and captured ovalbumin molecules, and secondary anti-ovalbumin antibodies conjugated with the enzyme horseradish peroxidase were subsequently added as label tag. The electrochemical signal proportional to the enzymatic reaction of horseradish peroxidase during the reduction of hydrogen peroxide with thionine as electron mediator was measured by linear sweep voltammetry. The newly established method of ovalbumin detection exhibits high sensitivity suitable for quantification in the range of 11 to 222nM and a detection limit of 5nM. Magnetic beads-based assay format using external magnets for rapid and simple separation has been proven to be an excellent basis for electrochemical detection and quantification of food allergens in highly complex sample matrices. PMID:25963896

  17. Highly sensitive electrochemical immunosensor for IgG detection based on optimized rigid biocomposites.

    PubMed

    Montes, R; Céspedes, F; Baeza, M

    2016-04-15

    In this work we present the construction of immunosensors based on graphite-epoxy which incorporate RIgG to the composite matrix. In order to improve the electrochemical properties of the immunocomposite electrodes, characterization and optimization was carried out in terms of electrochemical impedance spectroscopy and cyclic voltammetry. Consequently, taking into the account the properties required by a sensitive electrode such as high electron-transfer rate, high signal-to-noise ratio and suitable sensitivity; the optimal proportion of the transducer material (graphite-epoxy ratio) was chosen using constant amount of RIgG. The optimum composition range values, which provide these requirements, were from 16% to 17% of graphite loading. Then, the analytical properties of these immunosensors were evaluated measuring RIgG by using a competitive assay and using alkaline phosphatase-labeled antibody. Amperometric measurements were performed using hydrogen peroxide as substrate. Moreover, it has been the first time that it has been performed an optimization of the antigen-antibody ratio used in the assay, being this reduced significantly. PMID:26667092

  18. An ultrasensitive electrochemical immunosensor for apolipoprotein E4 based on fractal nanostructures and enzyme amplification.

    PubMed

    Liu, Yibiao; Xu, Li-Ping; Wang, Shuqi; Yang, Weizhao; Wen, Yongqiang; Zhang, Xueji

    2015-09-15

    Human apolipoprotein E4 (APOE4) is a major risk factor for Alzheimer's disease (AD) and can greatly increase the morbidity. In this work, an ultrasensitive sandwich-type electrochemical immunosensor for the quantitative detection of APOE4 was designed based on fractal gold (FracAu) nanostructures and enzyme amplification. The FracAu nanostructures were directly electrodeposited by hydrogen tetrachloroaurate (HAuCl4) on polyelectrolytes modified indium tin oxide (ITO) electrode. The sensing performances of the modified interface were investigated by cyclic voltammetry (CV). After functionalization with HRP-labeled APOE4 antibody, the human APOE4 could be detected quantitatively by current response. The current response has a linear relationship with the logarithm of human APOE4 concentrations in a range from 1.0 to 10,000.0 ng/mL, with a detection limit of 0.3 ng/mL. The fabricated APOE4 electrochemical immunosensor exhibits strong specificity, high sensitivity, low detection limit and wide linear range. The detection of human APOE4 provides a strong support for the prevention of AD and early-stage warning for those susceptible populations. PMID:25950934

  19. Comparative determination of two probiotics by QCM and OWLS-based immunosensors.

    PubMed

    Szalontai, Helga; Adányi, Nóra; Kiss, Attila

    2014-09-25

    The regular consumption of foods containing probiotic bacteria has beneficial physiological effects on the health and the digestion system. There is a need for novel analytical approaches for the determination of these bacteria that are faster than the classical plate counting method. For this purpose, two label-free biosensors were investigated and presented in this paper: Quartz Crystal Microbalance (QCM) and Optical Waveguide Lightmode Spectroscopy (OWLS) based direct immunosensors were developed for real-time direct detection of probiotic bacteria in fermented dairy products. Bifidobacterium bifidum O1356 and Lactobacillus acidophilus O1132 were detected by polyclonal anti-B. bifidum IgG and anti-L. acidophilus IgG immobilized on the sensors' surface. Sulfo-LC-SPDP cross linking agent was used to bind antibodies to the gold surface of the QCM's AT-cut quartz wafer. Concerning OWLS, antibodies were covalently bound to the amino groups of the silanized surface of the waveguide by glutaraldehyde. The dynamic measuring range was found between 1.0E+3 and 5.0E+5CFUmL(-1) in 100 fold diluted fermented milk products by QCM and with OWLS. Considering the current legislation of the probiotic content in probiotic products, the two developed immunosensors can be applied for rapid quantification of L. acidophilus and B. bifidum in fermented milk. These examinations offer effective alternatives to the microbiological plate counting method. PMID:24768869

  20. Simultaneous electrochemical immunosensor based on water-soluble polythiophene derivative and functionalized magnetic material.

    PubMed

    Zhang, Xiaoyue; Ren, Xiang; Cao, Wei; Li, Yueyun; Du, Bin; Wei, Qin

    2014-10-01

    A novel, sensitive electrochemical immunosensor for simultaneous determination of squamous cell carcinoma associated antigen (SCC-Ag) and carcinoembryonic antigen (CEA) for the combined diagnosis of cervical cancer was designed. The amplification strategy for electrochemical immunoassay was based on poly[3-(1,1'-dimethyl-4-piperidine-methylene) thiophene-2,5-diylchloride] (PDPMT-Cl) and functionalized mesoporous ferroferric oxide nanoparticles (Fe3O4 NPs). PDPMT-Cl dispersed in chitosan solution with enhanced electrical conductivity and solubility was used as matrices to immobilize the first antibodies. Different redox probes (thionine (Th) and ferrocenecarboxylic acid (Fca)) functionalized Fe3O4 NPs incubated with two kinds of secondary antibodies to fabricate the labels. Using an electrochemical analysis technique, two well-separated peaks were generated by Th and Fca, making the simultaneous detection of two analytes on the electrode possible. Under optimized conditions, this method showed wide linear ranges of three orders of magnitude with the detection limits of 4 pg mL(-1) and 5 pg mL(-1), respectively. The disposable immunosensor possessed excellent clinical value in cervical cancer screening as well as convenient point-of-care diagnostics. PMID:25201276

  1. A novel label-free microfluidic paper-based immunosensor for highly sensitive electrochemical detection of carcinoembryonic antigen.

    PubMed

    Wang, Yang; Xu, Huiren; Luo, Jinping; Liu, Juntao; Wang, Li; Fan, Yan; Yan, Shi; Yang, Yue; Cai, Xinxia

    2016-09-15

    In this work, a highly sensitive label-free paper-based electrochemical immunosensor employing screen-printed working electrode (SPWE) for detection of carcinoembryonic antigen (CEA) was fabricated. In order to raise the detection sensitivity and immobilize anti-CEA, amino functional graphene (NH2-G)/thionine (Thi)/gold nanoparticles (AuNPs) nanocomposites were synthesized and coated on SPWE. The principle of the immunosensor determination was based on the fact that the decreased response currents of Thi were proportional to the concentrations of corresponding antigens due to the formation of antibody-antigen immunocomplex. Experimental results revealed that the immunoassay enabled the determination of standard CEA solutions with linear working ranges of 50pgmL(-1) to 500ngmL(-1), the limit of detections for CEA is 10pgmL(-1) (S/N=3) and its corresponding correlation coefficients were 0.996. Furthermore, the proposed immunosensor could be used for the determination of clinical serum samples. A large number of clinical serum samples were detected and the relative errors between measured values and reference concentrations were calculated. Results showed that this novel paper-based electrochemical immunosensor could provide a new platform for low cost, sensitive, specific, and point-of-care diagnosis in cancer detection. PMID:27132007

  2. A droplet-based microfluidic immunosensor for high efficiency melamine analysis.

    PubMed

    Choi, Jae-Won; Min, Kyong-Mi; Hengoju, Sundar; Kim, Gil-Jung; Chang, Soo-Ik; deMello, Andrew J; Choo, Jaebum; Kim, Hak Yong

    2016-06-15

    We report a droplet-based microfluidic immunosensor for the rapid and accurate detection of melamine, an organic base that has been implicated in widescale adulteration of food products such as milk. Our melamine assay is based on the competitive reaction between native melamine and a melamine-fluorescein isothiocyanate (FITC) conjugate against an anti-hapten antibody. The adoption of fluorescence polarization, allows the quantification of melamine in a more direct and rapid manner than established heterogeneous methods based on liquid chromatography, mass spectrometry, and enzyme-linked immunosorbent assay (ELISA). The detection protocol provides a limit of detection of 300 ppb, which is below the maximum allowable melamine levels (2.5 ppm) defined by the U.S. Food and Drug Administration and the European Commission to a significant extent. PMID:26829578

  3. Ultrasensitive non-enzymatic immunosensor for carcino-embryonic antigen based on palladium hybrid vanadium pentoxide/multiwalled carbon nanotubes.

    PubMed

    Han, Jian; Jiang, Liping; Li, Faying; Wang, Ping; Liu, Qing; Dong, Yunhui; Li, Yueyun; Wei, Qin

    2016-03-15

    A novel and sensitive sandwich-type non-enzymatic electrochemical immunosensor was fabricated for quantitative monitoring of carcino-embryonic antigen (CEA). Nanocomposite of stannic oxide/reduced graphene oxide was used as substrate material to increase the specific surface area and enhance the conductivity of the glassy carbon electrode. Gold nanoparticles (Au NPs) were introduced to link substrate materials and primary antibodies (Ab1) and accelerate the electron transfer in this system. At the same time, the palladium nanoparticles (Pd NPs)-vanadium pentoxide (V2O5)/multiwalled carbon nanotubes (MWCNTs) were used as the label of secondary antibodies (Ab2). This composite label has shown excellent catalytic activity towards the reduction of H2O2. The nanomaterial-based signal amplification can improve the sensitivity and lower the limit of detection. The proposed immunosensor showed wide linear range from 0.5 pgmL(-1) to 25 ngmL(-1) with limit of detection of 0.17 pgmL(-1). This novel immunosensor was used to analyze serum sample. The results indicated that this immunosensor may find huge potential application for quantitative detection of CEA in the clinical diagnosis. PMID:26562331

  4. Highly sensitive luminol electrochemiluminescence immunosensor based on ZnO nanoparticles and glucose oxidase decorated graphene for cancer biomarker detection.

    PubMed

    Cheng, Yinfeng; Yuan, Ruo; Chai, Yaqin; Niu, Huan; Cao, Yaling; Liu, Huijing; Bai, Lijuan; Yuan, Yali

    2012-10-01

    In this work, we reported a sandwiched luminol electrochemiluminescence (ECL) immunosensor using ZnO nanoparticles (ZnONPs) and glucose oxidase (GOD) decorated graphene as labels and in situ generated hydrogen peroxide as coreactant. In order to construct the base of the immunosensor, a hybrid architecture of Au nanoparticles and graphene by reduction of HAuCl(4) and graphene oxide (GO) with ascorbic acid was prepared. The resulted hybrid architecture modified electrode provided an excellent platform for immobilization of antibody with good bioactivity and stability. Then, ZnONPs and GOD functionalized graphene labeled secondary antibody was designed for fabricating a novel sandwiched ECL immunosensor. Enhanced sensitivity was obtained by in situ generating hydrogen peroxide with glucose oxidase and the catalysis of ZnONPs to the ECL reaction of luminol-H(2)O(2) system. The as-prepared ECL immunosensor exhibited excellent analytical property for the detection of carcinoembryonic antigen (CEA) in the range from 10 pg mL(-1) to 80 ng mL(-1) and with a detection limit of 3.3 pg mL(-1) (SN(-1)=3). The amplification strategy performed good promise for clinical application of screening of cancer biomarkers. PMID:22938618

  5. Development of electrochemical immunosensors based on different serum antibody immobilization methods for detection of Japanese encephalitis virus

    NASA Astrophysics Data System (ADS)

    Tran, Quang Huy; Hanh Nguyen, Thi Hong; Mai, Anh Tuan; Thuy Nguyen, Thi; Khue Vu, Quang; Nga Phan, Thi

    2012-03-01

    This paper describes the development of electrochemical immunosensors based on human serum antibodies with different immobilization methods for detection of Japanese encephalitis virus (JEV). Human serum containing anti-JEV antibodies was used to immobilize onto the surface of silanized interdigitated electrodes by four methods: direct adsorption (APTES-serum), covalent binding with a cross linker of glutaraldehyde (APTES-GA-serum), covalent binding with a cross linker of glutaraldehyde combined with anti-human IgG (APTES-GA-anti-HIgG-serum) and covalent binding with a cross linker of glutaraldehyde combined with a bioaffinity of protein A (APTES-GA-PrA-serum). Atomic force microscopy was used to verify surface characteristics of the interdigitated electrodes before and after treatment with serum antibodies. The output signal of the immunosensors was measured by the change of conductivity resulting from the specific binding of JEV antigens and serum antibodies immobilized on the electrodes, with the help of horseradish peroxidase (HRP)-labeled secondary antibody against JEV. The results showed that the APTES-GA-PrA-serum method provided the highest signal of the electrochemical immunosensor for detection of JEV antigens, with the linear range from 25 ng ml‑1 to 1 μg ml‑1, and the limit of detection was about 10 ng ml‑1. This study shows a potential development of novel electrochemical immunosensors applied for virus detection in clinical samples in case of possible outbreaks.

  6. Positive potential operation of a cathodic electrogenerated chemiluminescence immunosensor based on luminol and graphene for cancer biomarker detection.

    PubMed

    Xu, Shoujiang; Liu, Yang; Wang, Taihong; Li, Jinghong

    2011-05-15

    In this work, we report a cathodic electrogenerated chemiluminescence (ECL) of luminol at a positive potential (ca. 0.05 V vs Ag/AgCl) with a strong light emission on the graphene-modified glass carbon electrode. The resulted graphene-modified electrode offers an excellent platform for high-performance biosensing applications. On the basis of the cathodic ECL signal of luminol on the graphene-modified electrode, an ECL sandwich immunosensor for sensitive detection of cancer biomarkers at low potential was developed with a multiple signal amplification strategy from functionalized graphene and gold nanorods multilabeled with glucose oxidase (GOx) and secondary antibody (Ab(2)). The functionalized graphene improved the electron transfer on the electrode interface and was employed to attach the primary antibody (Ab(1)) due to it large surface area. The gold nanorods were not only used as carriers of secondary antibody (Ab(2)) and GOx but also catalyzed the ECL reaction of luminol, which further amplified the ECL signal of luminol in the presence of glucose and oxygen. The as-proposed low-potential ECL immunosensor exhibited high sensitivity and specificity on the detection of prostate protein antigen (PSA), a biomarker of prostate cancer that was used as a model. A linear relationship between ECL signals and the concentrations of PSA was obtained in the range from 10 pg mL(-1) to 8 ng mL(-1). The detection limit of PSA was 8 pg mL(-1) (signal-to-noise ratio of 3). Moreover, the as-proposed low-potential ECL immunosensor exhibited excellent stability and reproducibility. The graphene-based ECL immunosensor accurately detected PSA concentration in 10 human serum samples from patients demonstrated by excellent correlations with standard chemiluminescence immunoassay. The results suggest that the as-proposed graphene ECL immunosensor will be promising in the point-of-care diagnostics application of clinical screening of cancer biomarkers. PMID:21513282

  7. Nanoparticle-based immunosensors and immunoassays for aflatoxins.

    PubMed

    Wang, Xu; Niessner, Reinhard; Tang, Dianping; Knopp, Dietmar

    2016-03-17

    Aflatoxins are naturally existing mycotoxins produced mainly by Aspergillus flavus and Aspergillus parasiticus, present in a wide range of food and feed products. Because of their extremely high toxicity and carcinogenicity, strict control of maximum residue levels of aflatoxins in foodstuff is set by many countries. In daily routine, different chromatographic methods are used almost exclusively. As supplement, in several companies enzyme immunoassay-based sample testing as primary screening is performed. Recently, nanomaterials such as noble metal nanoparticles, magnetic particles, carbon nanomaterials, quantum dots, and silica nanomaterials are increasingly utilized for aflatoxin determination to improve the sensitivity and simplify the detection. They are employed either as supports for the immobilization of biomolecules or as electroactive or optical labels for signal transduction and amplification. Several nanoparticle-based electrochemical, piezoelectric, optical, and immunodipstick assays for aflatoxins have been developed. In this review, we summarize these recent advances and illustrate novel concepts and promising applications in the field of food safety. PMID:26920768

  8. Rapid and Highly Sensitive Detection of Lead Ions in Drinking Water Based on a Strip Immunosensor

    PubMed Central

    Kuang, Hua; Xing, Changrui; Hao, Changlong; Liu, Liqiang; Wang, Libing; Xu, Chuanlai

    2013-01-01

    In this study, we have first developed a rapid and sensitive strip immunosensor based on two heterogeneously-sized gold nanoparticles (Au NPs) probes for the detection of trace lead ions in drinking water. The sensitivity was 4-fold higher than that of the conventional LFA under the optimized conditions. The visual limit of detection (LOD) of the amplified method for qualitative detection lead ions was 2 ng/mL and the LOD for semi-quantitative detection could go down to 0.19 ng/mL using a scanning reader. The method suffered from no interference from other metal ions and could be used to detect trace lead ions in drinking water without sample enrichment. The recovery of the test samples ranged from 96% to 103%. As the detection method could be accomplished within 15 min, this method could be used as a potential tool for preliminary monitoring of lead contamination in drinking water. PMID:23539028

  9. Optical immunosensor for endocrine disruptor nanolayer detection by surface plasmon resonance imaging

    NASA Astrophysics Data System (ADS)

    Karabchevsky, Alina; Tsapovsky, Lev; Marks, Robert S.; Abdulhalim, Ibrahim

    2011-10-01

    Endocrine disrupting compounds (EDCs) such as bisphenol A (BPA) and female hormone Estrone are especially prevalent in surface and waste-waters in nano-molar concentrations and therefore, there is a need for sensitive analytical device for their monitoring. We have designed a miniature, low cost and fast surface plasmon resonance (SPR) imaging liquid sensor based on the angular interrogation using Kretschmann configuration with diverged incident monochromatic light. During this paper we present a surface plasmon resonance imaging (SPRI) biosensor to detect EDCs such as BPA and estrone. A pattern of SPR line which is dark intensity line on bright area was reflected at angles range depending on the dielectric constant of the analye: Rabbit Anti-Estrone polyclonal IgG + Estrone 11-MUA attached to the silver or non-specific sensing of BPA in water with nanoprecision. For analyzing the SPR signals we used an efficient detection algorithm based on Radon Transform with less sensitivity to laser speckle noise and nonuniformity of the illumination.

  10. Nanosphere-based SERS immuno-sensors for protein analysis

    NASA Astrophysics Data System (ADS)

    Li, Honggang; Sun, Jian; Cullum, Brian M.

    2004-12-01

    We have developed and optimized novel nanosphere-based silver coated SERS substrates for the detection of proteins. These SERS substrates were optimized for silver thickness, number of silver layers, and extent of silver oxidation between layers. Immuno-nanosensors capable of being inserted into individual cells and non-invasively positioned to the sub-cellular location of interest using optical tweezers were constructed from monodisperse silica nanospheres. Silica nanospheres ranging in diameter from 100 to 4500 nm were condensed from tetraalkoxysilanes in an alcoholic solution of water and ammonia. By varying the reaction conditions, accurate control of the silica nanospheres" diameter was achieved. Silica sphere sizes were optimized for SERS signal response. Nanosphere-based SERS substrates were made by depositing multiple layers of silver on the nanospheres, followed by binding of the antibody of interest to the silver. In binding the antibodies, different crosslinkers were characterized and compared. On one end, each of these crosslinkers contained sulfur or isothiocyanate groups which bound to the silver surface, while the other end contained a carboxylic or primary amine group which reacted readily with the antibodies. In order to evaluate these substrates, SERS spectra of different proteins, such as insulin and interleukin-2 (IL-2), were obtained. By using silver, as the metal surface for SERS, red and near-infrared excitation wavelengths (i.e., 600-700 nm) can be used. Excitation in this range helps to avoid photodamage to cells and reduces any autofluorescence background. Evaluation of these SERS substrates was performed using a 10 mW HeNe laser, operating at 632.8 nm, in a collinear excitation/detection geometry. The SERS signals were filtered with a holographic notch filter, dispersed by 1/3 meter spectrometer and detected using an intensified charge coupled device (ICCD). This paper discusses the fabrication and optimization of these nanosensors, as

  11. Immunosensor systems with the Langmuir-film-based fluorescence detection

    SciTech Connect

    Chudinova, G K; Nagovitsyn, I A; Savranskii, V V; Karpov, R E

    2003-09-30

    A method is developed for detecting protein antigens for fluorescent immunoassay using a model system based on the technique for preparation of Langmuir films. Fluorescein isothiocyanate and donor-acceptor energy-transfer pairs of markers (the Yb complex of tetraphenyl porphyrin - benzoyl trifluoroacetoneisothiocyanate and derivatives of tetra(carboxyphenyl) porphyrin - cyanine dye containing a five-membered polyene chain), which were nor studied earlier, were used as markers for detecting the binding of an antigen on the surface of Langmuir films of antibodies. Fluorescence was detected in the near-IR region (for the first pair) and in the visible spectral range (for the second pair). To reduce the nonspecific sorption of a protein (antigen), a method was proposed for the preparation of a nonpolar surface by applying an even number of layers of stearic acid as a substrate for the Langmuir - Blodgett film. A high sensitivity of model systems to a protein antigen in solution was achieved ({approx}10{sup -11} M), the assay time being 6 - 8 min. The model system with the first donor - acceptor pair was tested in analysis of the blood plasma. The fluorescence of the Dy{sup 3+}, Tm{sup 3+}, and Yb{sup 3+} complexes of tetraphenyl porphyrin sensitised by diketonate complexes of lanthanides was studied for the first time and the enhancement of the IR fluorescence of these complexes in a Langmuir film was demonstrated. (papers devoted to the memory of academician a m prokhorov)

  12. A supersandwich electrochemiluminescence immunosensor based on mimic-intramolecular interaction for sensitive detection of proteins.

    PubMed

    He, Ying; Chai, Yaqin; Yuan, Ruo; Wang, Haijun; Bai, Lijuan; Liao, Ni

    2014-10-21

    An electrochemiluminescence (ECL) immunoassay protocol was developed based on mimic-intramolecular interaction for sensitive detection of prostate specific antigen (PSA). It was constructed by integrating the ECL luminophore (tris(4,4'-dicarboxylicacid-2,2'-bipyridyl)-ruthenium(ii)dichloride (Ru(dcbpy)3(2+))) and coreactant (histidine) into the supersandwich DNA structure. This strategy was more effective in amplifying the ECL signal by shortening the electronic transmission distance, improving the ECL luminous stability and enhancing the ECL luminous efficiency. The ECL matrices denoted as MWCNTs@PDA-AuNPs were fabricated through spontaneous oxidative polymerization of dopamine (DA) on multiwalled carbon nanotubes (MWCNTs) and reducing HAuCl4 to produce gold nanoparticles (AuNPs) by DA simultaneously. Then, the prepared matrices were applied to bind capture antibodies. Moreover, supersandwich Ab2 bioconjugate was designed using a PAMAM dendrimer to immobilize the detection antibody and supersandwich DNA structure. The PAMAM dendrimer, with a plurality of secondary and tertiary amine groups, not only facilitated high-density immobilization of the detection antibody and supersandwich DNA structure, but also greatly amplified the ECL signal of Ru(dcbpy)3(2+). The supersandwich DNA structure contained multiple Ru(dcbpy)3(2+) and histidine, further amplifying the ECL signal. The proposed supersandwich immunosensor showed high sensitivity with a detection limit of 4.2 fg mL(-1) and a wide linear range of 0.01 pg mL(-1)-40.00 ng mL(-1). With the excellent stability, satisfying precision and reproducibility, the proposed immunosensor indicates promising practicability for clinical diagnosis. PMID:25122008

  13. Towards an Electronic Dog Nose: Surface Plasmon Resonance Immunosensor for Security and Safety

    PubMed Central

    Onodera, Takeshi; Toko, Kiyoshi

    2014-01-01

    This review describes an “electronic dog nose” based on a surface plasmon resonance (SPR) sensor and an antigen–antibody interaction for security and safety. We have concentrated on developing appropriate sensor surfaces for the SPR sensor for practical use. The review covers different surface fabrications, which all include variations of a self-assembled monolayer containing oligo(ethylene glycol), dendrimer, and hydrophilic polymer. We have carried out detection of explosives using the sensor surfaces. For the SPR sensor to detect explosives, the vapor or particles of the target substances have to be dissolved in a liquid. Therefore, we also review the development of sampling processes for explosives, and a protocol for the measurement of explosives on the SPR sensor in the field. Additionally, sensing elements, which have the potential to be applied for the electronic dog nose, are described. PMID:25198004

  14. TiO2 nanowire bundle microelectrode based impedance immunosensor for rapid and sensitive detection of Listeria monocytogenes.

    PubMed

    Wang, Ronghui; Dong, Wenjun; Ruan, Chuanmin; Kanayeva, Damira; Tian, Ryan; Lassiter, Kentu; Li, Yanbin

    2008-09-01

    A novel TiO 2 nanowire bundle microelectrode based immunosensor was demonstrated as a more sensitive, specific, and rapid technology for detection of Listeria monocytogenes. TiO 2 nanowire bundle was prepared through a hydrothermal reaction of alkali with TiO 2 powder and connected to gold microelectrodes with mask welding. Monoclonal antibodies were immobilized on the surface of a TiO 2 nanowire bundle to specifically capture L. monocytogenes. Impedance change caused by the nanowire-antibody-bacteria complex was measured and correlated to bacterial number. This nanowire bundle based immunosensor could detect as low as 10 (2) cfu/ml of L. monocytogenes in 1 h without significant interference from other foodborne pathogens. PMID:18715043

  15. Electrochemical immunosensor for prostate-specific antigens using a label-free second antibody based on silica nanoparticles and polymer brush.

    PubMed

    Rafique, Saima; Bin, Wang; Bhatti, Arshad S

    2015-02-01

    In this paper, we propose a sensitive electrochemical immunosensor synthesized using a surface-initiated atom transfer radical polymerization process for the detection of prostate-specific antigen (PSA). Electrochemical immunosensors based on polymer brush [oligo(ethylene glycol)methacrylate-co-glycidyl methacrylate] (OEGMA-co-GMA) were grown on plane Au and nanostructured (NS) Au electrodes, characterized and compared for their sensitivity to detect PSA. Due to a large capacity for antibody loading and high resistance to nonspecific antibody adsorption of POEGMA-co-GMA brush, the Au-NS immunosensor exhibited detection in a wide dynamic range of five orders of magnitude with an improved lower limit of detection of 2pgml(-1), which was better than the synthesized immunosensor with the polymer brush grown on plane Au electrode. The Au-NS electrode showed improved detection sensitivity of 4.9μAng(-1)ml for PSA detection, which was almost 2 times better than the plane Au electrode. Finally, the use of silica nanoparticles (Si-NPs) conjugated with polyclonal antibody enhanced the response of the immunosensor. The proposed electrochemical immunosensor would be an exciting addition in medical diagnostics for the early detection of cancer biomarkers, e.g., PSA due to improved limit of detection (LOD); eventually helpful in circumventing cancer metastasis. PMID:25156671

  16. A highly sensitive quartz crystal microbalance immunosensor based on magnetic bead-supported bienzymes catalyzed mass enhancement strategy.

    PubMed

    Akter, Rashida; Rhee, Choong Kyun; Rahman, Md Aminur

    2015-04-15

    A highly sensitive quartz crystal microbalance (QCM) immunosensor based on magnetic bead-supported bienzyme catalyzed mass enhanced strategy was developed for the detection of human immunoglobulin G (hIgG) protein. The high sensitive detection was achieved by increasing the deposited mass on the QCM crystal through the enhanced precipitation of 4-chloro-1-naphthol (CN) using higher amounts of horseradish peroxidase (HRP) and glucose oxidase (GOx) bienzymes attached on the magnetic beads (MB). The protein A (PA) and capture antibody (monoclonal anti-human IgG antibody produced in mouse, Ab1)-based QCM probe and the detection antibody (anti-human IgG antibody produced in goat, Ab2)-based MB/HRP/GOx bienzymatic bioconjugates were characterized using scanning electron microscope, transmission electron microscope, cyclic voltammetry, and electrochemical impedance spectroscopy techniques. Under the optimized experimental condition, the linear range and the detection limit of hIgG immunosensor were determined to be 5.0pg/mL-20.0ng/mL and 5.0±0.18pg/mL, respectively. The applicability of the present hIgG immunosensor was examined in hIgG spiked human serum samples and excellent recoveries of hIgG were obtained. PMID:25506902

  17. One-step immobilization of antibodies for α-1-fetoprotein immunosensor based on dialdehyde cellulose/ionic liquid composite.

    PubMed

    Shen, Guangyu; Zhang, Xiangyang; Shen, Youming; Zhang, Songbai; Fang, Li

    2015-02-15

    A novel immunosensor for α-1-fetoprotein based on dialdehyde cellulose/ionic liquid composite film as a matrix has been developed. Microcrystalline cellulose was activated by sodium metaperiodate to produce dialdehyde cellulose. Antibodies can be immobilized on the electrode by a one-step method through covalent bonding of the aldehyde groups of dialdehyde cellulose with the amino groups of antibodies, in which no additional chemical cross-linking step is required. Moreover, ionic liquid added can improve the conductivity of the sensing interface and, therefore, can enhance the electrochemical signal. In this work, α-1-fetoprotein was detected within the range from 0.1 to 60ngml(-1) with a detection limit of 0.07ngml(-1) (signal/noise=3). The proposed immunosensor had good specificity and reproducibility. It was used to determine real samples with satisfactory results. PMID:25286306

  18. A sandwich-type electrochemical immunosensor based on the biotin- streptavidin-biotin structure for detection of human immunoglobulin G

    PubMed Central

    Li, Yueyun; Zhang, Yihe; Jiang, Liping; Chu, Paul K.; Dong, Yunhui; Wei, Qin

    2016-01-01

    A sandwich-type immunosensor is designed and fabricated to detect the human immunoglobulin G (HIgG) using polyaniline and tin dioxide functionalized graphene (GS-SnO2-PAN) as the platform and biotin-functionalized amination magnetic nanoparticles composite (B-Fe3O4@APTES) as the label. GS-SnO2-PAN is used as the sensing agent to capture the primary anti-HIgG (Ab1) and SnO2 reduces the stack of GS. The B-Fe3O4@APTES with a large surface area and excellent biocompatibility captures second antibody (Ab2) efficiently based on the highly selective recognition of streptavidin to biotinylated antibody. The B-Fe3O4@APTES has better electro-catalytic activity in the reduction of hydrogen peroxide (H2O2) and the “biotin-streptavidin-biotin” (B-SA-B) strategy leads to signal amplification. Under optimal conditions, the immunosensor has a wide sensitivity range from 1 pg/L to 10 ng/L and low detection limit of 0.33 pg/L (S/N = 3) for HIgG. The immunosensor has high sensitivity, fast assay rate, as well as good reproducibility, specificity, and stability especially in the quantitative detection of biomolecules in serum samples. PMID:26948273

  19. A sensitive label–free amperometric immunosensor for alpha-fetoprotein based on gold nanorods with different aspect ratio

    PubMed Central

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

    2015-01-01

    A simple and accurate label–free amperometric immunosensor for α–fetoprotein (AFP) detection is developed based on gold nanorods (GNRs) with different aspect ratio and compared with gold particles (GNPs). The positively charged GNRs and GNPs due to the surface immobilized cetyltrimethyl ammonium bromide (CTAB) can adsorb the negatively charged AFP antibody (Ab) directly. The presence of the GNRs not only enhanced the immobilized amount of biomolecules, but also improved the electrochemical properties of the immunosensor. With the aid of GNRs, the electrochemical signal was greatly enhanced in comparison with GNPs. Under optimal conditions, the proposed immunosensor could detect AFP in a linear range from 0.1 to 200 ng/mL with a detection limit of 0.04 ng/mL (signal–to–noise ratio = 3), and it also possessed good reproducibility and storage stability. Moreover, the detection of AFP in five human serum samples also showed satisfactory accuracy. The proposed methodology was potentially attractive for clinical immunoassay. PMID:25909588

  20. Room-temperature ionic liquid assisted fabrication of sensitive electrochemical immunosensor based on ordered macroporous gold film.

    PubMed

    Chen, Xiaojun; Zhou, Jinjun; Xuan, Jie; Yan, Wei; Jiang, Li-Ping; Zhu, Jun-Jie

    2010-10-01

    A novel label-free highly sensitive electrochemical impedance spectroscopy (EIS) immunosensor was fabricated based on the highly ordered macroporous gold film (HOMGF) in the presence of room-temperature ionic liquid (IL) for the detection of human Apolipoprotein B-100 (ApoB-100). The antibody of ApoB-100 (Ab) was adsorbed directly onto the HOMGF electrode surface and maintained its bioactivity. After the residual active sites at the electrode were passivated by BSA, the mixture of BMIm(+)BF(4)(-) and silica sol was dropped onto the electrode to entrap the adsorbed Ab and BSA molecules firmly. The addition of IL could prevent the inactivation of Ab by releasing alcohol during the sol-gel process, and the conductivity of the IL-gel membrane was increased. Of particular interest is the fact that the fabricated immunosensor could be used at 60 °C. This could be attributed to the interconnected porosity of the IL-gel membrane, which can prevent Ab from unfolding and losing its bioactivities. The immunosensor also exhibited a highly sensitive response to ApoB-100 with the lowest concentration of 5 fg mL(-1). The detection of ApoB-100 levels in five sera samples obtained from hospital showed acceptable accuracy with that using commercial immunonephelometry method. PMID:20694205

  1. A novel electrochemical immunosensor based on nonenzymatic Ag@Au-Fe3O4 nanoelectrocatalyst for protein biomarker detection.

    PubMed

    Zhang, Hongfang; Ma, Lina; Li, Pengli; Zheng, Jianbin

    2016-11-15

    A hybrid nanostructure of Fe3O4 nanospheres and Ag@Au nanorods prepared by polydopamine coating was utilized as nanoelectrocatalyst to construct a novel sandwich-type electrochemical immunosensor. Ag@Au-Fe3O4 nanohybrid modified electrode exhibited much better electrocatalytic activity toward the reduction of hydrogen peroxide than Fe3O4 nanospheres or Ag@Au nanorods due to the synergetic catalytic effect. The immunosensor was prepared by immobilizing the capture antibodies on the amine-terminated nanocomposite of carbon nanofibers-chitosan, whilst the trace tag was prepared by loading detection antibodies on the Ag@Au-Fe3O4 nanocomposite. After the parameter optimization, the amperometric signal increased linearly with human IgG concentration in the broad range of 0.1pgmL(-1) to 5μgmL(-1) with a detection limit of 50fgmL(-1). Meanwhile, the enzyme-free catalyst based immunosensor also showed acceptable selectivity, reproducibility and stability. PMID:27183286

  2. Detection of vibrio cholerae O1 by using cerium oxide nanowires - based immunosensor with different antibody immobilization methods

    NASA Astrophysics Data System (ADS)

    Tam, Phuong Dinh; Hoang, Nguyen Luong; Lan, Hoang; Vuong, Pham Hung; Anh, Ta Thi Nhat; Huy, Tran Quang; Thuy, Nguyen Thanh

    2016-05-01

    In this work, we evaluated the effects of different antibody immobilization strategies on the response of a CeO2-nanowires (NWs)-based immunosensor for Vibrio cholerae O1 detection. Accordingly, the changes in the electron-transfer resistance ( R et ) from before to after cells bind to an antibody-modified electrode prepared by using three different methods of antibody immobilization were determined. The values were 16.2%, 8.3%, and 6.65% for the method that utilized protein A, antibodies activated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS), and absorption, respectively. Cyclic voltammetry confirmed that the change in the current was highest for the immunosensors prepared using protein A (11%), followed by those prepared with EDC/NHS-activated antibodies (9%), and finally, those prepared through absorption (7.5%). The order of the antibody immobilization strategies in terms of resulting immunosensor detection limit and sensitivity was as follows order: absorption (3.2 × 103 CFU/mL; 45.1 Ω/CFU·mL-1) < EDC/NHS-activated antibody (1.0 × 103 CFU/mL; 50.6 Ω/CFU·mL-1) < protein A (1.0 × 102 CFU/mL; 65.8 Ω/CFU·mL-1). Thus, we confirmed that the protein A - mediated method showed significantly high cell binding efficiencies compared to the random immobilization method.

  3. Label electrochemical immunosensor for prostate-specific antigen based on graphene and silver hybridized mesoporous silica.

    PubMed

    Li, Yueyun; Han, Jian; Chen, Runhai; Ren, Xiang; Wei, Qin

    2015-01-15

    Prostate-specific antigen (PSA), as the specificity of prostate cancer markers, has been widely used in prostate cancer diagnosis and screening. In this study, we fabricated an electrochemical immunosensor for PSA detection using the amino-functionalized graphene sheet-ferrocenecarboxaldehyde composite materials (NH2-GS@FCA) and silver hybridized mesoporous silica nanoparticles (Ag@NH2-MCM48). Under optimal conditions, the fabricated immunosensor showed a wide linear range with PSA concentration (0.01-10.0ng·ml(-1)). Low detection limit (2pg·ml(-1)) proved the high sensitivity. In addition, the immunosensor possessed good stability and reproducibility. Moreover, the application to PSA analysis in serum samples yielded satisfactory results. PMID:25448622

  4. Measurement of polyphenol oxidase activity using optical waveguide lightmode spectroscopy-based immunosensor.

    PubMed

    Kim, Namsoo; Kim, Woo-Yeon

    2015-02-15

    Polyphenol oxidase (PPO) is an important quality index during food processing involving heat-treatment and sensitive determination of PPO activity has been a critical concern in the food industry. In this study, a new measurement of PPO activity exploiting an optical waveguide lightmode spectroscopy-based immunosensor is presented using a polyclonal anti-PPO antibody that was immobilized in situ to the surface of a 3-aminopropyltriethoxysilane-treated optical grating coupler activated with glutaraldehyde. When analysed with a purified PPO fraction from potato tubers, a linear relationship was found between PPO activities of 0.0005607-560.7U/mL and the sensor responses obtained. The sensor was applicable to measurement of PPO activity in real samples that were prepared from potato tubers, grapes and Kimchi cabbage, and the analytical results were compared with those obtained by a conventional colorimetric assay measuring PPO activity. When tested for long-term stability, the sensor was reusable up to 10th day after preparation. PMID:25236218

  5. The fabrication of a piezoelectric immunosensor based on DNA-antibody conjugate layer.

    PubMed

    Shen, Guangyu; Lu, Jilin; Cai, Chenbo

    2011-11-15

    In this article, we report a method of antibody immobilization carried out by hybridizing DNA-antibody conjugates on a mixed self-assembled monolayer composed of DNA thiols and mercaptopropionic acid via sequence-specific hybridization. The proposed method was applied to fabricate an immunosensor for detecting human immunoglobulin G (IgG). Under the optimized experimental conditions, a wide linear range from 50.0 to 500 μg/ml was reached with a detection limit of 30.13 μg/ml. The developed immunosensor possesses advantages such as simple fabrication, wide linear range, easy regeneration, and excellent reproducibility. PMID:21820399

  6. A capacitive immunosensor for detection of cholera toxin.

    PubMed

    Labib, Mahmoud; Hedström, Martin; Amin, Magdy; Mattiasson, Bo

    2009-02-23

    Contamination of food with biological toxins as well as their potential use as weapons of mass destruction has created an urge for rapid and cost effective analytical techniques capable of detecting trace amounts of these toxins. This paper describes the development of a sensitive method for detection of cholera toxin (CT) using a flow-injection capacitive immunosensor based on self-assembled monolayers. The sensing surface consists of monoclonal antibodies against the B subunit of CT (anti-CT), immobilized on a gold transducer. Experimental results show that the immunosensor responded linearly to CT concentrations in the range from 1.0x10(-13) to 1.0x10(-10) M under optimized conditions. The limit of detection (LOD) was 1.0x10(-14) M. Two more analytical methods were employed for detection of CT using the same antibody namely, sandwich ELISA and surface plasmon resonance (SPR)-based immunosensor. The former had an LOD of 1.2x10(-12) M and a working range from 3.7x10(-11) to 2.9x10(-10) M whereas, the later had an LOD of 1.0x10(-11) M and a linearity ranging from 1.0x10(-9) to 1.0x10(-6) M. These results demonstrate that the developed capacitive immunosensor system has a higher sensitivity than the other two techniques. The binding affinity of CT to the immobilized anti-CT was determined using the SPR-based immunosensor and an association constant (K(A)) of 1.4x10(9) M(-1) was estimated. PMID:19185129

  7. An electrochemical immunosensor for efficient detection of uropathogenic E. coli based on thionine dye immobilized chitosan/functionalized-MWCNT modified electrode.

    PubMed

    Gayathri, Chandran Hema; Mayuri, Pinapeddavari; Sankaran, Krishnan; Kumar, Annamalai Senthil

    2016-08-15

    Uropathogenic Escherichia coli (UPEC) is the major cause of 150 million Urinary Tract Infections (UTI) reported annually world-wide. High prevalence of multi-drug-resistance makes it dangerous and difficult to cure. Therefore simple, quick and early diagnostic tools are essential for effective treatment and control. We report an electrochemical immunosensor based on thionine dye (Th) immobilized on functionalized-multiwalled carbon nanotube+chitosan composite coated on glassy carbon electrode (GCE/f-MWCNT-Chit@Th) for quick and sensitive detection of UPEC in aqueous solution. This immunosensor was constructed by sequential immobilization of UPEC, bovine serum albumin, primary antibody and Horse Radish Peroxidase (HRP) tagged secondary antibody on the surface of GCE/f-MWCNT-Chit@Th. When analyzed using 2.5mM of hydrogen peroxide reduction reaction using cyclic voltammetry in phosphate buffer, pH 7.0, the immunosensor showed excellent linearity in a range of 10(2)-10(9)cfu of UPEC mL(-1) with a current sensitivity of 7.162μA {log(cfumL(-1))}(-1). The specificity of this immunosensor was tested using other UTI and non-UTI bacteria, Staphylococcus, Klebsiella, Proteus and Shigella. The clinical applicability of the immunosensor was also successfully tested directly in UPEC spiked urine samples (simulated sample). PMID:27040944

  8. A label-free electrochemical immunosensor based on an ionic organic molecule and chitosan-stabilized gold nanoparticles for the detection of cardiac troponin T.

    PubMed

    Brondani, Daniela; Piovesan, Jamille Valéria; Westphal, Eduard; Gallardo, Hugo; Fireman Dutra, Rosa Amalia; Spinelli, Almir; Vieira, Iolanda Cruz

    2014-10-21

    A label-free electrochemical immunosensor based on an ionic organic molecule ((E)-4-[(4-decyloxyphenyl)diazenyl]-1-methylpyridinium iodide) and chitosan-stabilized gold nanoparticles (CTS-AuNPs) was developed for the detection of cardiac troponin T (cTnT). The new ionic organic molecule was strategically employed as a redox probe, and CTS-AuNPs were applied as a "green" platform for the immobilization of the monoclonal anti-cTnT antibody, for the construction of the immunosensor. The characterization of the proposed immunosensor was carried out by employing cyclic and square-wave voltammetry and electron microscopy. The film of ionic organic molecules acts as a redox probe and from its electrochemical response the presence of cTnT antigens, which interact specifically with the anti-cTnT antibody immobilized on the surface of the immunosensor, can be detected. This interaction results in a decrease in the analytical signal, which is proportional to the amount of cTnT antigens present in the sample analyzed. Under optimized conditions, using square-wave voltammetry (a frequency of 100 Hz, an amplitude of 100 mV and an increment of 8 mV) and an incubation time of 10 min, the proposed immunosensor showed linearity in the range of 0.20 to 1.00 ng mL(-1) cTnT, with a calculated limit of detection of 0.10 ng mL(-1). The proposed immunosensor shows some advantages when compared to other sensors reported in the literature, especially with regard to the detection limit and the time of incubation. A study of the interday precision (n = 8) showed a coefficient of variation of 3.33%. The potential interference of some compounds (glucose, ascorbic acid, albumin, uric acid, creatine, and creatinine) on the response of the immunosensor was evaluated and the inhibition of the immunosensor response was found to be less than 8.0%. The immunosensor was successfully used for the determination of cTnT in samples of simulated blood serum with a relative error of <13.0%. Furthermore, the

  9. Field-based detection and monitoring of uranium in contaminated groundwater using two immunosensors

    SciTech Connect

    Melton, S.J.; Yu, H.; Williams, K.H.; Morris, S.A.; Long, P.E.; Blake, D.A.

    2009-05-01

    Field-based monitoring of environmental contaminants has long been a need for environmental scientists. Described herein are two kinetic exclusion-based immunosensors, a field portable sensor (FPS) and an inline senor, that were deployed at the Integrated Field Research Challenge Site of the U.S. Department of Energy in Rifle, CO. Both sensors utilized a monoclonal antibody that binds to a U(VI)-dicarboxyphenanthroline complex (DCP) in a kinetic exclusion immunoassay format. These sensors were able to monitor changes of uranium in groundwater samples from {approx} 1 {micro}M to below the regulated drinking water limit of 126 nM (30 ppb). The FPS is a battery-operated sensor platform that can determine the uranium level in a single sample in 5-10 min, if the instrument has been previously calibrated with standards. The average minimum detection level (MDL) in this assay was 0.33 nM (79 ppt), and the MDL in the sample (based on a 1:200?1:400 dilution) was 66?132 nM (15.7?31.4 ppb). The inline sensor, while requiring a grounded power source, has the ability to autonomously analyze multiple samples in a single experiment. The average MDL in this assay was 0.12 nM (29 ppt), and the MDL in the samples (based on 1:200 or 1:400 dilutions) was 24?48 nM (5.7?11.4 ppb). Both sensor platforms showed an acceptable level of agreement (r{sup 2} = 0.94 and 0.76, for the inline and FPS, respectively) with conventional methods for uranium quantification.

  10. Field-Based Detection and Mnitoring of Uranium in Contaminated Groundwater using two Immunosensors

    SciTech Connect

    Melton, Scott J; Yu, Haini; Williams, Kenneth H; Morris, Sarah A; Long, Philip E; Blake, Diane A

    2009-09-01

    Field-based monitoring of environmental contaminants has long been a need for environmental scientists. Described herein are two kinetic exclusion-based immunosensors, a field portable sensor (FPS) and an inline senor, that were deployed at the Integrated Field Research Challenge Site of the U.S. Department of Energy in Rifle, CO. Both sensors utilized a monoclonal antibody that binds to a U(VI)-dicarboxyphenanthroline complex (DCP) in a kinetic exclusion immunoassay format. These sensors were able to monitor changes of uranium in groundwater samples from ~1 μM to below the regulated drinking water limit of 126 nM (30 ppb). The FPS is a battery-operated sensor platform that can determine the uranium level in a single sample in 5-10 min, if the instrument has been previously calibrated with standards. The average minimum detection level (MDL) in this assay was 0.33 nM (79 ppt), and the MDL in the sample (based on a 1:200-1:400 dilution) was 66-132 nM (15.7-31.4 ppb). The inline sensor, while requiring a grounded power source, has the ability to autonomously analyze multiple samples in a single experiment. The average MDL in this assay was 0.12 nM (29 ppt), and the MDL in the samples (based on 1:200 or 1:400 dilutions) was 24-48 nM (5.7-11.4 ppb). Both sensor platforms showed an acceptable level of agreement (r2 = 0.94 and 0.76, for the inline and FPS, respectively) with conventional methods for uranium quantification.

  11. An Electrochemiluminescence Immunosensor Based on Gold-Magnetic Nanoparticles and Phage Displayed Antibodies

    PubMed Central

    Mu, Xihui; Tong, Zhaoyang; Huang, Qibin; Liu, Bing; Liu, Zhiwei; Hao, Lanqun; Dong, Hua; Zhang, Jinping; Gao, Chuan

    2016-01-01

    Using the multiple advantages of the ultra-highly sensitive electrochemiluminescence (ECL) technique, Staphylococcus protein A (SPA) functionalized gold-magnetic nanoparticles and phage displayed antibodies, and using gold-magnetic nanoparticles coated with SPA and coupled with a polyclonal antibody (pcAb) as magnetic capturing probes, and Ru(bpy)32+-labeled phage displayed antibody as a specific luminescence probe, this study reports a new way to detect ricin with a highly sensitive and specific ECL immunosensor and amplify specific detection signals. The linear detection range of the sensor was 0.0001~200 µg/L, and the limit of detection (LOD) was 0.0001 µg/L, which is 2500-fold lower than that of the conventional ELISA technique. The gold-magnetic nanoparticles, SPA and Ru(bpy)32+-labeled phage displayed antibody displayed different amplifying effects in the ECL immunosensor and can decrease LOD 3-fold, 3-fold and 20-fold, respectively, compared with the ECL immunosensors without one of the three effects. The integrated amplifying effect can decrease the LOD 180-fold. The immunosensor integrates the unique advantages of SPA-coated gold-magnetic nanoparticles that improve the activity of the functionalized capturing probe, and the amplifying effect of the Ru(bpy)32+-labeled phage displayed antibodies, so it increases specificity, interference-resistance and decreases LOD. It is proven to be well suited for the analysis of trace amounts of ricin in various environmental samples with high recovery ratios and reproducibility. PMID:26927130

  12. Quinone-Based Polymers for Label-Free and Reagentless Electrochemical Immunosensors: Application to Proteins, Antibodies and Pesticides Detection

    PubMed Central

    Piro, Benoit; Reisberg, Steeve; Anquetin, Guillaume; Duc, Huynh-Thien; Pham, Minh-Chau

    2013-01-01

    Polyquinone derivatives are widely recognized in the literature for their remarkable properties, their biocompatibility, simple synthesis, and easy bio-functionalization. We have shown that polyquinones present very stable electroactivity in neutral aqueous medium within the cathodic potential domain avoiding side oxidation of interfering species. Besides, they can act as immobilized redox transducers for probing biomolecular interactions in sensors. Our group has been working on devices based on such modified electrodes with a view to applications for proteins, antibodies and organic pollutants using a reagentless label-free electrochemical immunosensor format. Herein, these developments are briefly reviewed and put into perspective. PMID:25587398

  13. A novel sandwich electrochemiluminescence immunosensor for ultrasensitive detection of carbohydrate antigen 19-9 based on immobilizing luminol on Ag@BSA core/shell microspheres.

    PubMed

    Zhang, Amin; Xiang, Hongkun; Zhang, Xin; Guo, Weiwei; Yuan, Enhui; Huang, Chusen; Jia, Nengqin

    2016-01-15

    A novel sandwich-type electrochemiluminescence immunosensor based on immobilizing luminol on Ag@BSA core/shell microspheres (Ag@BSA-luminol) for ultrasensitive detection of tumor marker carbohydrate antigen 19-9 (CA19-9) has been developed. Herein, magnetic carbon nanotubes (MAGCNTs) decorated with polyethylenimine (PEI) was used to construct the base of the immunosensor. MAGCNTs with prominent electrical conductivity and high surface area could be beneficial for promoting the electron transfer and loading plenty of primary antibodies (Ab1) via glutaraldehyde (GA). Meanwhile, the magnetic property of MAGCNTs makes it easy to be attached to the surface of magnetic glass carbon electrode (MGCE) through magnetism interaction, which provides an outstanding platform for this immunosensor. Moreover, Ag@BSA microspheres with large surface area, good stability, and excellent biocompatibility were desirable candidates for effective cross-link of CA19-9 detection antibodies (Ab2). A more interesting thing was that ELISA color reaction was used as an ultrasensitive strategy for identifying Ab2 was successfully coated on Ag@BSA with the naked eye. Additionally, we immobilized the luminol on the surface of Ag@BSA to prepare the target immunosensor. Immobilization of luminol on the surface of Ag@BSA could decrease the distance between luminophores and the electrode surface, leading to great enhancement of the ECL intensity of luminol in the present of hydrogen peroxide (H2O2). Under the optimal conditions, the intensity of the ECL immunosensor increased linearly with the logarithm of CA19-9 concentration in a wide linear range from 0.0005 to 150UmL(-1) with a detection limit of 0.0002UmL(-1) (S/N=3). All the results suggested the prepared CA19-9 immunosensor displayed high sensitivity, excellent stability and good specificity. The developed method opened a new avenue to clinical bioassay. PMID:26319163

  14. A gas-phase amplified quartz crystal microbalance immunosensor based on catalase modified immunoparticles.

    PubMed

    Liu, Wei; Huang, Renliang; Qi, Wei; Wang, Mengfan; Su, Rongxin; He, Zhimin

    2015-02-21

    A novel signal amplification strategy for quartz crystal microbalance (QCM) based on catalytic gas generation was developed to construct an ultrasensitive immunosensor for the detection of proteins (immunoglobulin G, IgG, used as a model). A catalase modified immunoparticle was prepared to form a sandwich-type immunocomplex with the IgG and anti-IgG antibodies that were immobilized on the QCM sensor. The amount of immunoparticles on the sensor surface was thus controlled by the IgG concentration. Then H2O2 was added and catalyzed by catalase for oxygen generation. The generated oxygen replaced some of the liquid on the sensor surface, leading to the change in the shear modulus of the immunocomplex layer and the apparent viscosity and density of the liquid layer. Due to the ultrasensitive response of QCM to these changes, a significant frequency shift related to the IgG concentration was achieved. Different parameters, including the flow cell structure, operation temperature, immunoparticle concentration, and H2O2 concentration were optimized to achieve steady and efficient frequency shifts. Under the optimal conditions, the proposed gas-phase amplified QCM sensor could achieve up to 72 times improvement of detection sensitivity compared to the label-free sensor as a control, in the concentration range of 0.1-3.0 μg mL(-1). The detection limit was also reduced from 236 ng mL(-1) to 51.0 ng mL(-1) at the 3Sblank level. PMID:25519742

  15. A new surface plasmon resonance immunosensor for triazine pesticide determination in bovine milk: a comparison with conventional amperometric and screen-printed immunodevices.

    PubMed

    Tomassetti, Mauro; Martini, Elisabetta; Campanella, Luigi; Favero, Gabriele; Sanzó, Gabriella; Mazzei, Franco

    2015-01-01

    A detailed comparison was made of the analytical features of a new Surface Plasmon Resonance (SPR) immunodevice for triazine pesticide determination with those of two other amperometric (conventional and screen-printed) immunosensors and the advantages and disadvantages of the SPR method were thoroughly investigated. For conventional amperometric and screen-printed devices, "competitive" assays were used; conversely, the SPR transduction technique allowed a "direct" measurement format to be used. As far as the main analytical data are concerned, the SPR method does not seem to offer substantial advantages. Nevertheless the measurement time is much shorter and the measurement itself much easier to perform. Lastly several applications and recovery tests were carried out on bovine milk samples, before and after spiking, to check for triazine pesticides in the samples, obtaining satisfactory results. PMID:25942643

  16. Self-powered competitive immunosensor driven by biofuel cell based on hollow-channel paper analytical devices.

    PubMed

    Li, Shuai; Wang, Yanhu; Ge, Shenguang; Yu, Jinghua; Yan, Mei

    2015-09-15

    A mediator-less and compartment-less glucose/O2 enzymatic biofuel cell (BFC) was introduced into microfluidic paper-based analytical devices (μ-PADs) that relies on flow in hollow channels with silver nanoparticles/graphene modified paper electrode as the anodic and cathodic substrate, to implement self-powered sensitive carcinoembryonic antigen (CEA) detection. Glucose dehydrogenase (GDH)-gold nanoparticles bioconjugate modified with CEA acted as a biocatalyst for enhancing glucose oxidation in the bioanode, as well as the transducing enzyme for signaling magnification. Similarly, nanoporous PtNi/bilirubin oxidase (BOD) acted as a biocatalyst for enhancing O2 reduction in the biocathode. With an increase in the concentration of CEA, the amount of CEA-Au-GDH bioconjugate on bioanode decreases, thus leading to the lower output of the as-prepared BFC. This proposed BFC-based self-powered immunosensor for CEA possessed largely increased linear detection range from 1 pg mL(-1) to 0.5 μg mL(-)(1) with a detection limit of 0.7 pg mL(-)(1). The proposed BFC-based self-powered immunosensor shows high sensitivity, stability, and reproducibility and can become a promising platform for other protein detection. PMID:25880834

  17. Magnetic nanoparticle-based immunosensor for electrochemical detection of hepatitis B surface antigen.

    PubMed

    Nourani, Sara; Ghourchian, Hedayatollah; Boutorabi, Seyed Mehdi

    2013-10-01

    An electrochemical immunosensor was developed for the detection of hepatitis B surface antigen (HBsAg). The biotinylated hepatitis B surface antibody was immobilized on streptavidin magnetic nanoparticles and used for targeting the HBsAg. By the addition of horseradish peroxidase conjugated with secondary antibody (HRP-HBsAb), a sandwich-type immunoassay format was formed. Aminophenol as substrate for conjugated HRP was enzymatically changed into 3-aminophenoxazone (3-APZ). This electroactive enzymatic production (3-APZ) was transferred into an electrochemical cell and monitored by cyclic voltammetry. Under optimal conditions, the cathodic current response of 3-APZ, which was proportional to the HBsAg concentration, was measured by a glassy carbon electrode. The immunosensor response was linear toward HBsAg in the concentration range from 0.001 to 0.015 ng/ml with a detection limit of 0.9 pg/ml at a signal/noise ratio of 3. PMID:23831477

  18. Monitoring microbial populations of sulfate-reducing bacteria using an impedimetric immunosensor based on agglutination assay.

    PubMed

    Wan, Yi; Zhang, Dun; Hou, Baorong

    2009-11-15

    An impedimetric immunosensor was fabricated for rapid and non-labeled detection of sulfate-reducing bacteria, Desulforibrio caledoiensis (SRB) by immobilizing lectin-Concanavalin A using an agglutination assay. The immobilization of lectin was conducted using amine coupling on the surface of a gold (Au) electrode assembled with 11-Mercaptoundecanoic acid. Electrochemical impedance spectroscopy (EIS) was used to verify the stepwise assembly of the sensor system. The work conditions of the impedimetric immunosensor, such as pH of the buffer solutions and the incubation time of lectin, were optimized. Faradic impedance spectra for charge transfer for the redox probe Fe(CN)(6)(3-/4-)were measured to determine SRB concentrations. The diameter of the Nyquist diagram that is equal to the charge-transfer resistance (R(ct)) increased with increasing SRB concentration. A linear relationship between R(ct) and SRB concentration was obtained in SRB concentration range of 1.8 to 1.8 x 10(7)cfu/ml. The variation of the SRB population during the growth process was also monitored using the impedimetric immunosensor. This approach has great potential for simple, low-cost, and time-saving monitoring of microbial populations. PMID:19782217

  19. Novel surface antigen based impedimetric immunosensor for detection of Salmonella typhimurium in water and juice samples.

    PubMed

    Mutreja, Ruchi; Jariyal, Monu; Pathania, Preeti; Sharma, Arunima; Sahoo, D K; Suri, C Raman

    2016-11-15

    A specific surface antigen, OmpD has been reported first time as a surface biomarker in the development of selective and sensitive immunosensor for detecting Salmonella typhimurium species. The OmpD surface antigen extraction was done from Salmonella typhimurium serovars, under the optimized growth conditions for its expression. Anti-OmpD antibodies were generated and used as detector probe in immunoassay format on graphene-graphene oxide (G-GO) modified screen printed carbon electrodes. The water samples were spiked with standard Salmonella typhimurium cells, and detection was done by measuring the change in impedimetric response of developed immunosensor to know the concentration of serovar Salmonella typhimurium. The developed immunosensor was able to specifically detect S. typhimurium in spiked water and juice samples with a sensitivity upto 10(1)CFUmL(-1), with high selectivity and very low cross-reactivity with other strains. This is the first report on the detection of Salmonella typhimurum species using a specific biomarker, OmpD. The developed technique could be very useful for the detection of nontyphoidal Salmonellosis and is also important from an epidemiological point of view. PMID:27261886

  20. A competitive photoelectrochemical immunosensor based on a CdS-induced signal amplification strategy for the ultrasensitive detection of dexamethasone.

    PubMed

    Wang, Xueping; Yan, Tao; Li, Yan; Liu, Yixin; Du, Bin; Ma, Hongmin; Wei, Qin

    2015-01-01

    A novel photoelectrochemical immunosensor based on the competitive strategy is proposed for the specific detection of dexamethasone (DXM). Graphitic carbon nitride coupled with bismuth sulfide are used as the sensing matrix for the immobilization of BSA-DXM on the electrode surface, while cadmium sulfide functionalized titanium dioxide (TiO2@CdS) is used as the photoelectric active labels of anti-DXM. Due to the perfect matching of energy levels between TiO2 and CdS, the in situ prepared composite labels show excellent photocurrent response under visible lights. The competitive binding of DXM in sample solutions and BSA-DXM on the electrode surface reduces the specific attachment of labels to the electrode, resulting in a decrease of the photocurrent intensity. Greatly enhanced sensitivity is achieved after the optimization of the detection conditions. Under the optimal detection condition, the well-designed immunosensor for DXM exhibits a low detection limit of 2 pg ∙ mL(-1). Additionally, the proposed immunoassay system shows high specificity, good reproducibility and acceptable stability, which is also expected to become a promising platform for the detection of other small molecules. PMID:26648409

  1. Dual immunosensor based on methylene blue-electroadsorbed graphene oxide for rapid detection of the influenza A virus antigen.

    PubMed

    Veerapandian, Murugan; Hunter, Robert; Neethirajan, Suresh

    2016-08-01

    Rapid detection of influenza viral infections in poultry facilities is advantageous in several aspects such as environmental/personal safety, food-security, and socio-economy. Herein, we report the development of an electrochemical-based dual-sensor platform composed of methylene blue-electroadsorbed graphene oxide nanostructures modified with monoclonal antibodies against the HA proteins of H5N1 and H1N1. Bio-functional layers comprised of chitosan and protein-A molecules were implemented at the interface of the sensor element and antibodies, which synergistically enriched the bio-activity of immobilized antibodies for the immune complex formation. The differential pulse voltammetric signals resulted from the developed immunosensor platform exhibited a good correlation (R(2)=0.9978 for H1N1 and R(2)=0.9997 for H5N1) for the wide range of target concentrations 25-500pM). Chronoamperometric study also revealed the amplified current sensitivity of the immunoelectrodes even at the picomolar level. The proposed immunosensor design not only provides rapid analytical response time (<1min) but simplicity in fabrication and instrumentation, which paves an attractive platform for on-farm monitoring of viral infections. PMID:27216681

  2. An Amperometric Immunosensor Based on Multi-Walled Carbon Nanotubes-Thionine-Chitosan Nanocomposite Film for Chlorpyrifos Detection

    PubMed Central

    Sun, Xia; Cao, Yaoyao; Gong, Zhili; Wang, Xiangyou; Zhang, Yan; Gao, Jinmei

    2012-01-01

    In this work, a novel amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan (MWCNTs-THI-CHIT) nanocomposite film as electrode modified material was developed for the detection of chlorpyrifos residues. The nanocomposite film was dropped onto a glassy carbon electrode (GCE), and then the anti-chlorpyrifos monoclonal antibody was covalently immobilized onto the surface of MWCNTs-THI-CHIT/GCE using the crosslinking agent glutaraldehyde (GA). The modification procedure was characterized by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, a linear relationship between the relative change in peak current of different pulse voltammetry (DPV) and the logarithm of chlorpyrifos solution concentration was obtained in the range from 0.1 to 1.0 × 105 ng/mL with a detection limit of 0.046 ng/mL. The proposed chlorpyrifos immunosensor exhibited high reproducibility, stability, and good selectivity and regeneration, making it a potential alternative tool for ultrasensitive detection of chlorpyrifos residues in vegetables and fruits. PMID:23443396

  3. A highly sensitive flow-through amperometric immunosensor based on the Peroxidase chip and enzyme-channeling principle.

    PubMed

    Zeravik, J; Ruzgas, T; Fránek, M

    2003-10-01

    A concept based on the Peroxidase-chip (P-chip), antibody co-immobilization, competitive and enzyme-channeling principle was exploited to develop an integrated flow-through amperometric biosensor for detection of environmental pollutants such as s-triazine herbicides. In this concept, recombinant peroxidase is immobilized on the gold electrode (P-chip) in such a way that direct electron transfer is achieved. The recognition and quantitation the target analyte is realized through the competition between the simazine-glucose oxidase (GOD) conjugate and free simazine for the binding sites of the monoclonal antibody co-immobilized with peroxidase on the gold electrode. The arrangement allows to generate a specific signal in the presence of glucose through the channeling of H2O2 produced by GOD conjugate bound to the antibody. The immunosensor exhibited 50% signal decrease (IC50 value) at approximately 0.02 microg l(-1). A concentration of 0.1 ng l(-1) gave a signal clearly distinguishable from the blank whereas the ELISA using the same antibody had a typical detection limit of about 1 microg l(-1), which is four orders of magnitude higher compared to the presented biosensor system. The results demonstrated that gene engineering biomolecules, in this case recombinant peroxidase, might be attractive reagents for the development of electrochemical immunosensors. PMID:12896832

  4. A competitive photoelectrochemical immunosensor based on a CdS-induced signal amplification strategy for the ultrasensitive detection of dexamethasone

    PubMed Central

    Wang, Xueping; Yan, Tao; Li, Yan; Liu, Yixin; Du, Bin; Ma, Hongmin; Wei, Qin

    2015-01-01

    A novel photoelectrochemical immunosensor based on the competitive strategy is proposed for the specific detection of dexamethasone (DXM). Graphitic carbon nitride coupled with bismuth sulfide are used as the sensing matrix for the immobilization of BSA-DXM on the electrode surface, while cadmium sulfide functionalized titanium dioxide (TiO2@CdS) is used as the photoelectric active labels of anti-DXM. Due to the perfect matching of energy levels between TiO2 and CdS, the in situ prepared composite labels show excellent photocurrent response under visible lights. The competitive binding of DXM in sample solutions and BSA-DXM on the electrode surface reduces the specific attachment of labels to the electrode, resulting in a decrease of the photocurrent intensity. Greatly enhanced sensitivity is achieved after the optimization of the detection conditions. Under the optimal detection condition, the well-designed immunosensor for DXM exhibits a low detection limit of 2 pg∙mL−1. Additionally, the proposed immunoassay system shows high specificity, good reproducibility and acceptable stability, which is also expected to become a promising platform for the detection of other small molecules. PMID:26648409

  5. A separation-free amperometric immunosensor for vitellogenin based on screen-printed carbon arrays modified with a conductive polymer.

    PubMed

    Darain, Farzana; Park, Doeg Su; Park, Jang-Su; Chang, Seung-Cheol; Shim, Yoon-Bo

    2005-03-15

    A disposable amperometric immunosensor was studied for the rapid detection of carp (Carassius auratus) Vitellogenin (Vtg). The sensor was fabricated based on screen-printed carbon arrays (SPCAs) containing eight carbon working and an integrated carbon counter electrodes. To construct the sensor, a conducting polymer (poly-terthiophene carboxylic acid) was electropolymerized on the surface of working electrodes and the polymer-coated SPCAs was characterized by SEM. Horseradish peroxidase (HRP) and a monoclonal antibody (anti-Vtg) specific to carp Vtg were covalently attached onto the polymer modified SPCAs. The immobilization of HRP and anti-Vtg onto the polymer-coated SPCAs was examined using cyclic voltammetry and quartz crystal microbalance studies. In order to detect the amount of Vtg, glucose oxidase (GOx)-labelled Vtg bound to the sensor surface under competition with the Vtg analyte was quantified amperometrically using glucose as a substrate. The performance of the eight sensors in arrays was evaluated by obtaining the calibration plots for Vtg. The sensor arrays exhibit a linear range of the Vtg concentration from 0.25 to 7.8 ng/ml and the detection limit was determined to be 0.09 ng/ml. Furthermore, the performance of the immunosensor for the determination of Vtg was evaluated by a standard addition method performed in fish serum samples. PMID:15681194

  6. Ultrasensitive electrochemical immunosensor for carbohydrate antigen 72-4 based on dual signal amplification strategy of nanoporous gold and polyaniline-Au asymmetric multicomponent nanoparticles.

    PubMed

    Fan, Haixia; Guo, Zhankui; Gao, Liang; Zhang, Yong; Fan, Dawei; Ji, Guanglei; Du, Bin; Wei, Qin

    2015-02-15

    A sandwich electrochemical immunosensor is described for carbohydrate antigen 72-4 (CA72-4) based on a dual amplification strategy with nanoporous gold (NPG) film as the sensor platform and polyaniline-Au asymmetric multicomponent nanoparticles (PANi-Au AMNPs) as labels. In this study, the second anti-CA72-4 antibody (Ab2) adsorbed onto the Au of the PANi-Au AMNPs, which could be simply synthesized by interfacial reaction and have many characteristics of polyaniline and Au nanoparticle, such as well-controlled size, high conductivity, biocompatibility and catalysis. NPG film was used as electrode substrate material to fix a large number of antibodies, due to its unique properties: good biocompatibility, high conductivity, large surface area, and stability. The synergetic of NPG film and PANi-Au AMNPs could increase signal response, and significantly improve sensitivity of the immunosensor. The proposed immunosensor exhibited a wide linear range from 2 to 200 U/mL, with a detection limit of 0.10 U/mL CA72-4, good reproducibility, selectivity and stability. This new type of labels for immunosensors may provide many potential applications in the detection of carbohydrate antigen in immunoassays. PMID:25194795

  7. Sandwich-type electrochemical immunosensor for the detection of AFP based on Pd octahedral and APTES-M-CeO₂-GS as signal labels.

    PubMed

    Wei, Yicheng; Li, Yan; Li, Na; Zhang, Yong; Yan, Tao; Ma, Hongmin; Wei, Qin

    2016-05-15

    In the present work, an ultrasensitive sandwich-type electrochemical immunosensor based on a novel signal amplification strategy was designed for quantitative detection of alpha fetoprotein (AFP). Au nanoparticles with biocompatibility were electrodeposited on the surface of glassy carbon electrode (GCE) which can effectively capture and immobilize primary anti-AFP (Ab1) to significantly amplify the electrochemical signal. Graphene Oxide and CeO2 mesoporous nanocomposite functionalized by the 3-aminopropyltriethoxysilane supported Pd octahedral nanoparticles (Pd/APTES-M-CeO2-GS) were utilized as labels of detection anti-AFP (Ab2). Pd octahedral nanoparticles presented good catalytic activity towards the reduction of H2O2. Due to the large specific surface area and good adsorption properties of APTES-CeO2-GS nanocomposite, large amount of Pd octahedral nanoparticles could be immobilized, which could amplify the electrochemical signal and improve the sensitivity of the immunosensor. Under optimal conditions, the immunosensor exhibited wide linear range from 0.1 pg/mL to 50 ng/mL with a low detection limit of 0.033 pg/mL (S/N=3) for AFP detection. In addition, high sensitivity, excellent selectivity, good reproducibility and stability were obtained for the immunosensor, which has a promising application for quantitative detection of other tumor markers in clinical diagnosis. PMID:26745795

  8. Label-free Electrochemiluminescent Immunosensor for Detection of Prostate Specific Antigen based on Aminated Graphene Quantum Dots and Carboxyl Graphene Quantum Dots

    PubMed Central

    Wu, Dan; Liu, Yixin; Wang, Yaoguang; Hu, Lihua; Ma, Hongmin; Wang, Guoqin; Wei, Qin

    2016-01-01

    Prostate-specific antigen (PSA) was used as the model, an ultrasensitive label-free electrochemiluminescent immunosensor was developed based on graphene quantum dots. Au/Ag-rGO was sythsized and used as electrode material to load a great deal of graphene quantum dots due to the large surface area and excellent electron conductivity. After aminated graphene quantum dots and acarboxyl graphene quantum dots were modified onto the electrode, the ECL intensity was much high using K2S2O8 as coreactant. Then, antibody of PSA was immobilized on the surface of modified electrode surface through the adsorption of Au/Ag toward proteins, leading to the decrease of the ECL intensity. As proven by ECL spectra test and electrochemical impedance spectroscopy (EIS) analysis, the fabrication process of the immunosensor is successful. Under the optimal conditions, the ECL intensity decreased linearly with the logarithm of PSA concentration in the range of 1 pg/mL ~ 10 ng/mL. The detection limit achieved is 0.29 pg/mL. The immunosensor results were validated through the detection of PSA in serum samples with satisfactory results. Due to excellent stability, high sensitivity, acceptable repeatability and selectivity, the immunosensor has promising applications in disease and drug analysis. PMID:26842737

  9. A label-free electrochemiluminescence immunosensor based on KNbO3-Au nanoparticles@Bi2S3 for the detection of prostate specific antigen.

    PubMed

    Li, Jianxiu; Ma, Hongmin; Wu, Dan; Li, Xiaojian; Zhao, Yongbei; Zhang, Yong; Du, Bin; Wei, Qin

    2015-12-15

    A high sensitive label-free electrochemiluminescence (ECL) immunosensor was fabricated for the detection of prostate specific antigen (PSA) based on potassium niobate-Au nanoparticles@bismuth sulfide (KNbO3-Au NPs@Bi2S3) modified glassy carbon electrode (GCE). The prepared Bi2S3 nanosheets exhibited strong and stable cathodic ECL activity. The synthesized KNbO3-Au NPs was firstly used to fabricate ECL modified electrodes and Bi2S3 nanosheets worked as luminophores for the first time in ECL sensors. Au NPs were used to combine with Bi2S3 and anti-PSA via the Au-S covalent bond and Au-NH2 covalent bond without the usage of crosslinking agents respectively, further enhancing the sensitivity and stability of immunosensor. Under the optimum experimental conditions, the ECL signal of KNbO3-Au NPs@Bi2S3 linearly decreased with the increase of PSA concentration in the range of 0.005-5 ng/mL with a detection limit of 3 pg/mL. The preparated label-free ECL immunosensor exhibited high sensitivity and selectivity, good repeatability and long-term stability. The applicability of the proposed ECL immunosensor was also evaluated by detecting PSA in real samples. PMID:26120817

  10. Electrochemical immunosensor for detection of prostate specific antigen based on an acid cleavable linker into MSN-based controlled release system.

    PubMed

    Fan, Dawei; Li, Na; Ma, Hongmin; Li, Yan; Hu, Lihua; Du, Bin; Wei, Qin

    2016-11-15

    A mesoporous silica nanoparticle (MSN)-based controlled release system with acid cleavable linkage was developed to fabricate an electrochemical immunosensor for the quantitative detection of the prostate-specific antigen (PSA). 3,9-Bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5]undecane functionalized mesoporous silica nanoparticles (MSN-Acetal) were used to immobilize the electron mediator thionine (Th). The encapsulation of Th molecules was achieved by capping the pores of MSN-Acetal with carboxylic acid modified Au nanoparticles (defined as MSN-Th-Au). Under the acidic conditions, the capped Au nanoparticles were removed from MSN-Th-Au through the hydrolysis of the acid-labile acetal linker, resulting in the release of encapsulated Th. In this work, the pH-responsive cargo release system was firstly used as the label of secondary anti-PSA for developing an electrochemical immunosensor, and amination Fe3O4 was used as the sensing matrix for immobilizing primary anti-PSA on magnetic carbon electrode surfaces. The specific recognition of PSA resulted in the attachment of MSN-Th-Au-secondary anti-PSA (MSN-Th-Au-Ab2) onto the electrode surfaces. Subsequently, the released Th was detected by differential pulse voltammetry under the acidic conditions. The developed cargo release system provided an innovative and reliable method for the detection of PSA because the response signal was correlated with the concentration of PSA. Under the optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.001-5.0ng/mL with a low detection limit of 0.31pg/mL. Moreover, the developed immunosensor showed superior reproducibility and long-term stability, which has promising applications in bioassay and biosensing. PMID:27236723

  11. DNA-based hybridization chain reaction for an ultrasensitive cancer marker EBNA-1 electrochemical immunosensor.

    PubMed

    Song, Chao; Xie, Guoming; Wang, Li; Liu, Lingzhi; Tian, Guang; Xiang, Hua

    2014-08-15

    An ultrasensitive and selective electrochemical immunosensor was developed for the detection of Epstein Barr virus nuclear antigen 1 (EBNA-1). Firstly, a suspension of graphene sheets (GS) and multi-walled carbon nanotubes (MWCNTs) was prepared with the aid of chitosan (CS) solution and then modified on a glassy carbon electrode (GCE). Gold nanoparticles (AuNPs) were then electrodeposited onto the surface of the GS-MWCNTs film by cyclic voltammetry (CV) to immobilize the captured antibodies. After that, specific sandwich immunoreactions were formed among the captured antibody, EBNA-1, and secondary antibody, DNA-coated carboxyl multi-wall carbon nanotubes (DNA-MWCNTs-Ab2). DNA initiator strands (S0) and secondary antibodies linked to the MWCNTs and double-helix DNA polymers were obtained by hybridization chain reaction (HCR), and here S0 on the MWCNTs propagates a chain reaction of hybridization events between two alternating hairpins to form a nicked double-helix. Finally, electroactive indicator doxorubicin hydrochloride was intercalated into the CG-GC steps between the HCR products and could produce an electrochemical signal, which was monitored by differential pulse voltammetry (DPV). Under optimum conditions, the amperometric signal increased linearly with the target concentrations (0.05-6.4ngmL(-1)), and the immunosensor exhibited a detection limit as low as 0.7pgmL(-1) (S/N=3). The proposed method showed acceptable stability and reproducibility, as well as favorable recovery for EBNA-1 in human serum. The proposed immunosensor provides a novel avenue for signal amplification and potential applications in bioanalysis and clinical diagnostics. PMID:24632131

  12. Quantum dots based potential-resolution dual-targets electrochemiluminescent immunosensor for subtype of tumor marker and its serological evaluation.

    PubMed

    Liu, Xuan; Jiang, Hui; Fang, Yuan; Zhao, Wei; Wang, Nianyue; Zang, Guizhen

    2015-09-15

    The identification of subtypes of known tumor markers is of great importance for clinical diagnosis but still a great challenge in novel detection methodologies with simple operation and acceptable sensitivity. This work for the first time reported a quantum dots (QDs) based potential-resolved electrochemiluminescent (ECL) immunosensor to realize simultaneous detection of dual targets. Because of different surface microstructures, dimercaptosuccinic acid stabilized CdTe (DMSA-CdTe) QDs and TiO2 nanoparticles-glutathione stabilized CdTe (TiO2-GSH-CdTe) QDs composites showed a large difference of ECL peak potential (∼360 mV), which provided an access for potential-resolution detection. The ECL emission on indium tin oxide electrodes showed consistent strength during the cyclic scan, and intensity data were collected at -0.89 V and -1.25 V (vs Ag/AgCl) for DMSA-CdTe QDs and TiO2-GSH-CdTe QDs composites, respectively. The interface modification procedures of immunosensor construction were characterized by atomic force microscopy. The portion of Lens culinaris lectin affiliated isoform of alpha fetoprotein (AFP), AFP-L3%, in total AFP, is recently a novel criteria showing even higher sensitivity and specificity than AFP at the early stage of cancer. Combined with the enzyme cyclic amplification strategy, linear ranges for AFP-L3 and AFP dual-targets detection were 3.24 pg mL(-1)-32.4 ng mL(-1) and 1.0 pg mL(-1)-20 ng mL(-1), with limits of detection of 3.24 pg mL(-1) and 1.0 pg mL(-1), respectively. Compared with clinical detection data, the calculated portion of AFP-L3% by as-prepared immunosensor showed acceptable accuracy. These results open a new avenue for facile and rapid multiple-components detection based on the nano-ECL technique and provide a new clinical diagnosis platform for HCC. PMID:26291342

  13. An electrochemical immunosensor based on covalent immobilization of okadaic acid onto screen printed carbon electrode via diazotization-coupling reaction.

    PubMed

    Hayat, Akhtar; Barthelmebs, Lise; Sassolas, Audrey; Marty, Jean-Louis

    2011-07-15

    In this work, an electrochemical method based on the diazonium-coupling reaction mechanism for the immobilization of okadaic acid (OA) on screen printed carbon electrode was developed. At first, 4-carboxyphenyl film was grafted by electrochemical reduction of 4-carboxyphenyl diazonium salt, followed by terminal carboxylic group activation by N-hydroxysuccinimide (NHS), N-(3-dimethylaminopropyle)-N'-ethyle-carbodiimide hydrochloride (EDC). Hexamethyldiamine was then covalently bound by one of its terminal amine group to the activated carboxylic group. The carboxyl group of okadaic acid was activated by EDC/NHS and then conjugated to the second terminal amine group on other side of the hexamethyldiamine through amide bond formation. After immobilization of OA, an indirect competitive immunoassay format was employed to detect OA. The immunosensor obtained using this novel approach allowed detection limit of 1.44 ng/L of OA, and was also validated with certified reference mussel samples. PMID:21645734

  14. Immunosensor based on nanocomposite of nanostructured zirconium oxide and gelatin-A.

    PubMed

    Bagbi, Yana; Sharma, Anshu; Bohidar, H B; Solanki, Pratima R

    2016-01-01

    We have reported the studies related to the fabrication of a nanocomposite, comprising of sol-gel derived inorganic zirconium oxide nanoparticles (ZrO2 NPs) and organic biopolymer gelatin-A (GA), deposited on indium-tin-oxide (ITO) coated glass substrate by drop casting method. The GA-ZrO2/ITO electrode was used for immobilization of monoclonal antibodies (Ab) specific to antigen Vibrio cholerae (Vc) followed by bovine serum albumin (BSA) for antigen Vc detection using electrochemical techniques. The structural and morphological behaviour of these ZrO2 NPs, GA-ZrO2/ITO electrode and BSA/Ab/GA-ZrO2/ITO immunosensor was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy techniques. The transmission electron microscopy study exhibited a spherical shape ZrO2 NPs. The average crystalline size of ZrO2 NPs was obtained as 10.3 ± 1 nm from X-ray diffraction measurement and 72 nm hydrodynamic radius measured by dynamic light scattering. GA-ZrO2 nanocomposite provides a porous structure which assists to higher loading of Ab on the matrix surface that improved the biosensing properties. The electrochemical response studies of the fabricated BSA/Ab/GA-ZrO2/ITO immunosensor exhibited good linearity in the range of 50-400 ng mL(-1), low limit of detection of 0.74 ng/mL, sensitivity as 0.03 Ω ng(-1)mL(-1)cm(-2) and reproducibility more than 10 times. PMID:26515440

  15. Nanoparticle-Based Electrochemical Immunosensor for the Detection of Phosphorylated Acetylcholinesterase: An Exposure Biomarker of Organophosphate Pesticides and Nerve AgentsOrganophosphate Pesticides and Nerve Agents

    SciTech Connect

    Liu, Guodong; Wang, Jun; Barry, Richard C.; Petersen, Catherine E.; Timchalk, Charles; Gassman, Paul L.; Lin, Yuehe

    2008-11-01

    A nanoparticle-based electrochemical immunosensor has been developed for the detection of phosphorylated acetylcholinesterase (AChE) adducts, which is a potential exposure biomarker for organophosphate pesticides (OP) and chemical warfare nerve agent exposures. Zirconia nanoparticles (ZrO2 NPs) were used as selective sorbents to capture the phosphorylated AChE adduct, and quantum dots (ZnS@CdS, QDs) were used as tags to label monoclonal anti-AChE antibody to track the immunorecognition events. The sandwich-like immunoreactions were performed among the ZrO2 NPs, which were pre-coated on a screen printed electrode (SPE) by electrodeposition, phosphorylated AChE and QD-anti-AChE. The captured QD tags were determined on the SPE by electrochemical stripping analysis of its metallic component (cadmium) after an acid-dissolution step. Paraoxon was used as a model OP insecticide to prepare the phosphorylated AChE adduct to demonstrate the proof of principle for this sensor technology. The paraoxon-AChE adduct was characterized by Fourier Transform Infrared Spectrum, and the binding affinity of anti-AChE to the paraoxon-AChE was validated with an enzyme-linked immunosorbent assay. The parameters (e.g., amount of ZrO2 NP, QD-anti-AChE concentration,) that govern the electrochemical response of immunosensors were optimized. The voltammetric response of the immunosensor is highly linear over the range of 10 pM to 4 nM paraoxon-AChE, and the limit of detection is estimated to be 8 pM. This new nanoparticle-based electrochemical immunosensor thus provides a sensitive and quantitative tool for biomonitoring exposure to OP pesticides and nerve agents.

  16. Rapid detection of Escherichia coli O157:H7 and Salmonella Typhimurium in foods using an electrochemical immunosensor based on screen-printed interdigitated microelectrode and immunomagnetic separation.

    PubMed

    Xu, Meng; Wang, Ronghui; Li, Yanbin

    2016-02-01

    Foodborne pathogens have continuously been a serious food safety issue and there is a growing demand for a rapid and sensitive method to screen the pathogens for on-line or in-field applications. Therefore, an impedimetric immunosensor based on the use of magnetic beads (MBs) for separation and a screen-printed interdigitated microelectrode (SP-IDME) for measurement was studied for the rapid detection of Escherichia coli O157:H7 and Salmonella Typhimurium in foods. Streptavidin coated MBs were functionalized with corresponding biotinylated antibodies (Ab) to capture the target bacteria. The glucose oxidase (GOx)-Ab conjugates were employed to label the MBs-Ab-cell complexes. The yielded MBs-Ab-cell-Ab-GOx biomass was mixed with the glucose solution to trigger an enzymatic reaction which produced gluconic acid. This increased the ion strength of the solution, thus decreasing the impedance of the solution measured on the SP-IDME. Our results showed that the immunosensor was capable of specifically detecting E. coli O157:H7 and S. Typhimurium within the range of 10(2)-10(6) cfu ml(-1) in the pure culture samples. E. coli O157:H7 in ground beef and S. Typhimurium in chicken rinse water were also examined. The limits of detection (LODs) for the two bacteria in foods were 2.05×10(3) cfu g(-1) and 1.04×10(3) cfu ml(-1), respectively. This immunosensor required only a bare electrode to measure the impedance changes, and no surficial modification on the electrode was needed. It was low-cost, reproducible, easy-to-operate, and easy-to-preserve. All these merits demonstrated this immunosensor has great potential for the rapid and on-site detection of pathogenic bacteria in foods. PMID:26653441

  17. A label-free electrochemiluminescence immunosensor based on EuPO4 nanowire for the ultrasensitive detection of Prostate specific antigen.

    PubMed

    Ma, Hongmin; Zhou, Jing; Li, Yan; Han, Tongqian; Zhang, Yong; Hu, Lihua; Du, Bin; Wei, Qin

    2016-06-15

    EuPO4 nanowire, which exhibited strong and stable cathodic electrochemiluminescence (ECL) activity, was used for the first time to fabricate an immunosensor for the detection of prostate specific antigen (PSA). EuPO4 has some inherent excellent properties such as long luminescence lifetime, narrow emission band, high quantum yield and low toxicity. Based on these properties, a novel label-free ECL immunosensor was developed using EuPO4 as a sensing matrix. Chitosan solution was used to disperse EuPO4 nanowires and the amino groups on chitosan enabled the covalent attachment of capture antibodies. After the modification of the electrode surface with EuPO4 nanowires, anti-PSA was then immobilized on them, forming a label-free immunosensing interface. The specific binding of PSA on the electrode inhibited the ECL reaction of EuPO4 nanowires with the coreactant due to the steric hindrance effect (Deng et al., 2013). Under the optimum conditions, a good linear relationship between ECL intensity and the logarithm of PSA concentration was obtained in the range of 0.0005-80 ng/mL with a detection limit of 177.33 fg/mL. The proposed ECL immunosensor showed good stability, acceptable selectivity and reproducibility. PMID:26855165

  18. Single-step cycle pulse operation of the label-free electrochemiluminescence immunosensor based on branched polypyrrole for carcinoembryonic antigen detection.

    PubMed

    Zhu, Wenjuan; Wang, Qi; Ma, Hongmin; Lv, Xiaohui; Wu, Dan; Sun, Xu; Du, Bin; Wei, Qin

    2016-01-01

    A novel label-free electrochemiluminescence (ECL) immunosensor based on luminol functional-Au NPs@polypyrrole has been developed for the detection of carcinoembryonic antigen (CEA). In this work, polypyrrole prepared by chemical polymerization provided a large surface area to load amounts of gold nanoparticles (Au NPs). Au NPs could not only attach abundant luminol for the enhancement of ECL signal, but also provide a friendly microenvironment for the immobilization of antibodies. Moreover, 1-butylpyridinium tetrafluroborate ([BPy]BF4) were used to disperse luminol functional-Au NPs@polypyrrole nanocomposites, resulting in the film-formation of composites on the electrode, which could improve the stability of immunosensor. In particular, employment of single-step cycle pulse could limit the consecutive reaction between luminol and H2O2 efficiently, thus leading to stable and strong signals. The proposed method presents good ECL response for the detection of CEA allowing a wide linear range from 0.01 pg/mL to 10 ng/mL and a limit of detection as low as 3 fg/mL. The immunosensor would be a promising tool in the early diagnosis of CEA due to its high sensitivity, simplicity and cost-effective. PMID:27091590

  19. 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

  20. Disposable integrated bismuth citrate-modified screen-printed immunosensor for ultrasensitive quantum dot-based electrochemical assay of C-reactive protein in human serum.

    PubMed

    Kokkinos, Christos; Prodromidis, Mamas; Economou, Anastasios; Petrou, Panagiota; Kakabakos, Sotirios

    2015-07-30

    A novel immunosensor based on graphite screen-printed electrodes (SPEs) modified with bismuth citrate was developed for the voltammetric determination of C-reactive protein (CRP) in human serum using quantum dots (QDs) labels. The sandwich-type immunoassay involved physisorption of CRP capture antibody on the surface of the sensor, sequential immunoreactions with CRP and biotinylated CRP reporter antibody and finally reaction with streptavidin-conjugated PbS QDs. The quantification of the target protein was performed with acidic dissolution of the PbS QDs and anodic stripping voltammetric detection of the Pb(II) released. Detection was performed at bismuth nanodomains formed on the sensor surface during the electrolytic preconcentration step, as bismuth citrate was reduced to metallic bismuth simultaneously with the deposition of Pb on the surface of the immunosensor. Under optimal conditions, the response was linear over the range 0.2-100 ng mL(-1) CRP and the limit of detection was 0.05 ng mL(-1) CRP. Since the modified SPE serves as both the biorecognition element and the QDs reader, the analytical procedure is simplified, the drawbacks of existing electroplated immunosensors are minimized while the proposed disposable sensing platform provides convenient, low-cost and ultrasensitive detection of proteins and wider scope for mass-production. PMID:26320633

  1. Ultrasensitive electrochemical immunosensor for SCCA detection based on ternary Pt/PdCu nanocube anchored on three-dimensional graphene framework for signal amplification.

    PubMed

    Liu, Yuanyuan; Ma, Hongmin; Gao, Jian; Wu, Dan; Ren, Xiang; Yan, Tao; Pang, Xuehui; Wei, Qin

    2016-05-15

    In this study, a novel and ultrasensitive sandwich-type electrochemical immunosensor was designed for the quantitative detection of squamous cell carcinoma antigen (SCCA) based on the β-cyclodextrin functionalized graphene nanosheet (CD-GN) and the ternary hollow Pt/PdCu nanocube anchored on three-dimensional graphene framework (Pt/PdCu-3DGF). CD-GN exhibited high specific surface area and good dispersibility and stability in water, which were beneficial to fix captured antibodies (Ab1) through the supramolecular host-guest interaction between CD and Ab1. The abundant oxygen-containing functional groups on 3DGF provided binding sites for anchoring noble metal nanoparticles. Pt/PdCu-3DGF could capture detected antibodies via the interaction of Pd-NH2 and Pt-NH2. Furthermore, the ternary metal nanoparticles exhibited high electrocatalytic activity toward the reduction of hydrogen peroxide. Under optimal conditions, the fabricated immunosensor showed a sensitive response to SCCA with two linear ranges. The linear ranges are 0.0001-1 ng/mL and 1-30 ng/mL with a detection limit of 25 fg/mL. Additionally, the proposed immunosensor showed good reproducibility and stability. PMID:26700578

  2. Highly sensitive impedimetric immunosensor based on single-walled carbon nanohorns as labels and bienzyme biocatalyzed precipitation as enhancer for cancer biomarker detection.

    PubMed

    Yang, Fan; Han, Jing; Zhuo, Ying; Yang, Zhehan; Chai, Yaqin; Yuan, Ruo

    2014-05-15

    A novel sandwich-type electrochemical immunosensor based on functionalized nanomaterial labels and bienzyme (horseradish peroxidase and glucose oxidase) biocatalyzed precipitation was developed for the detection of α-fetoprotein (AFP). The enzymes linked to functionalized nanomaterials as biocatalysts could accelerate the oxidation of 4-chloro-1-naphthol (4-CN) by H2O2 to yield the insoluble product on the electrode surface; the mass loading of the precipitates on the device led to a significant enhanced signal. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to monitor the enhanced precipitation of 4-CN that accumulated on the electrode surface and subsequent decrement in the electrode surface area by monitoring the reduction process of the Fe(CN)6(4-/3-) redox couple. Under optimal conditions, the proposed immunosensor showed a high sensitivity and a wide linear range from 0.001 to 60 ng mL(-1) with a low detection limit of 0.33 pg mL(-1). Moreover, the immunosensor exhibited good selectivity, acceptable stability and reproducibility. The amplification strategy showed good promise for clinical screening of tumor biomarkers. PMID:24419078

  3. Single-step cycle pulse operation of the label-free electrochemiluminescence immunosensor based on branched polypyrrole for carcinoembryonic antigen detection

    PubMed Central

    Zhu, Wenjuan; Wang, Qi; Ma, Hongmin; Lv, Xiaohui; Wu, Dan; Sun, Xu; Du, Bin; Wei, Qin

    2016-01-01

    A novel label-free electrochemiluminescence (ECL) immunosensor based on luminol functional-Au NPs@polypyrrole has been developed for the detection of carcinoembryonic antigen (CEA). In this work, polypyrrole prepared by chemical polymerization provided a large surface area to load amounts of gold nanoparticles (Au NPs). Au NPs could not only attach abundant luminol for the enhancement of ECL signal, but also provide a friendly microenvironment for the immobilization of antibodies. Moreover, 1-butylpyridinium tetrafluroborate ([BPy]BF4) were used to disperse luminol functional-Au NPs@polypyrrole nanocomposites, resulting in the film-formation of composites on the electrode, which could improve the stability of immunosensor. In particular, employment of single-step cycle pulse could limit the consecutive reaction between luminol and H2O2 efficiently, thus leading to stable and strong signals. The proposed method presents good ECL response for the detection of CEA allowing a wide linear range from 0.01 pg/mL to 10 ng/mL and a limit of detection as low as 3 fg/mL. The immunosensor would be a promising tool in the early diagnosis of CEA due to its high sensitivity, simplicity and cost-effective. PMID:27091590

  4. Diagnosis of schistosomiasis japonica with interfacial co-assembly-based multi-channel electrochemical immunosensor arrays

    NASA Astrophysics Data System (ADS)

    Deng, Wangping; Xu, Bin; Hu, Haiyan; Li, Jianyong; Hu, Wei; Song, Shiping; Feng, Zheng; Fan, Chunhai

    2013-05-01

    Schistosomiasis control remains to be an important and challenging task in the world. However, lack of quick, simple, sensitive and specific sero-diagnostic test is still a hurdle in the control practice. The commonly employed enzyme-linked immuno-sorbent assay (ELISA) relies on the native soluble egg antigen (SEA) that is limited in supply. Here we developed an electrochemical immunosensor array (ECISA) assay with an interfacial co-assembly strategy. A recombinant Schistosoma japonicum (Sj) calcium-binding protein (SjE16) was used as a principal antigen, while the SEA as a minor, co-assembling agent, with a ratio of 8:1 (SjE16: SEA, Sj16EA), which was co-immobilized on a disposable 16-channel screen-printed carbon electrode array. A portable electrochemical detector was employed to detect antibodies in serum samples. The sensitivity of ECISA reached 100% with minimal cross-reactions. Therefore, we have demonstrated that this rapid, sensitive and specific ECISA technique has the potential to perform large-scale on-site screening of Sj infection.

  5. Electrochemical immunosensor for simultaneous detection of multiplex cancer biomarkers based on graphene nanocomposites.

    PubMed

    Chen, Xia; Jia, Xinle; Han, Jingman; Ma, Jie; Ma, Zhanfang

    2013-12-15

    In this work, a sandwich-format electrochemical immunosensor for simultaneous determination of carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) was fabricated using biofunctional carboxyl graphene nanosheets (CGS) as immunosensing probes, which were fabricated by means of immobilization of toluidine blue (TB) and labeled anti-CEA (Ab2,1), Prussian blue (PB) and anti-AFP (Ab2,2) successively on CGS. The capture anti-CEA (Ab1,1) and anti-AFP (Ab1,2) were immobilized onto the chitosan-Au nanoparticles (CHIT-AuNPs) modified electrode through 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxy succinimide (EDC/NHS). Experimental results revealed that this sandwich-type immunoassay enabled simultaneous detection of CEA and AFP with linear range of 0.5-60 ng mL(-1) for both analytes. The detection limit was 0.1 ng mL(-1) for CEA and 0.05 ng mL(-1) for AFP (S/N=3). The assay results of serum samples with the proposed method were in a good agreement with the reference values from the standard ELISA method. And the negligible cross-reactivity between the two analytes allows it to possess potential promise in clinical diagnosis. PMID:23891798

  6. Diagnosis of schistosomiasis japonica with interfacial co-assembly-based multi-channel electrochemical immunosensor arrays.

    PubMed

    Deng, Wangping; Xu, Bin; Hu, Haiyan; Li, Jianyong; Hu, Wei; Song, Shiping; Feng, Zheng; Fan, Chunhai

    2013-01-01

    Schistosomiasis control remains to be an important and challenging task in the world. However, lack of quick, simple, sensitive and specific sero-diagnostic test is still a hurdle in the control practice. The commonly employed enzyme-linked immuno-sorbent assay (ELISA) relies on the native soluble egg antigen (SEA) that is limited in supply. Here we developed an electrochemical immunosensor array (ECISA) assay with an interfacial co-assembly strategy. A recombinant Schistosoma japonicum (Sj) calcium-binding protein (SjE16) was used as a principal antigen, while the SEA as a minor, co-assembling agent, with a ratio of 8:1 (SjE16: SEA, Sj16EA), which was co-immobilized on a disposable 16-channel screen-printed carbon electrode array. A portable electrochemical detector was employed to detect antibodies in serum samples. The sensitivity of ECISA reached 100% with minimal cross-reactions. Therefore, we have demonstrated that this rapid, sensitive and specific ECISA technique has the potential to perform large-scale on-site screening of Sj infection. PMID:23648995

  7. Amperometric immunosensor for carbofuran detection based on MWCNTs/GS-PEI-Au and AuNPs-antibody conjugate.

    PubMed

    Zhu, Ying; Cao, Yaoyao; Sun, Xia; Wang, Xiangyou

    2013-01-01

    In this paper, an amperometric immunosensor for the detection of carbofuran was developed. Firstly, multiwall carbon nanotubes (MWCNTs) and graphene sheets-ethyleneimine polymer-Au (GS-PEI-Au) nanocomposites were modified onto the surface of a glass carbon electrode (GCE) via self-assembly. The nanocomposites can increase the surface area of the GCE to capture a large amount of antibody, as well as produce a synergistic effect in the electrochemical performance. Then the modified electrode was coated with gold nanoparticles-antibody conjugate (AuNPs-Ab) and blocked with BSA. The monoclonal antibody against carbofuran was covalently immobilized on the AuNPs with glutathione as a spacer arm. The morphologies of the GS-PEI-Au nanocomposites and the fabrication process of the immunosensor were characterized by X-ray diffraction (XRD), ultraviolet and visible absorption spectroscopy (UV-vis) and scanning electron microscopy (SEM), respectively. Under optimal conditions, the immunosensor showed a wide linear range, from 0.5 to 500 ng/mL, with a detection limit of 0.03 ng/mL (S/N = 3). The as-constructed immunosensor exhibited notable performance features such as high specificity, good reproducibility, acceptable stability and regeneration performance. The results are mainly due to the excellent properties of MWCNTs, GS-PEI-Au nanocomposites and the covalent immobilization of Ab with free hapten binding sites for further immunoreaction. It provides a new avenue for amperometric immunosensor fabrication. PMID:23604029

  8. Optical waveguide lightmode spectroscopy technique-based immunosensor development for aflatoxin B1 determination in spice paprika samples.

    PubMed

    Majer-Baranyi, Krisztina; Zalán, Zsolt; Mörtl, Mária; Juracsek, Judit; Szendrő, István; Székács, András; Adányi, Nóra

    2016-11-15

    Optical waveguide lightmode spectroscopy (OWLS) technique has been applied to label-free detection of aflatoxin B1 in a competitive immunoassay format, with the aim to compare the analytical goodness of the developed OWLS immunosenor with HPLC and enzyme-linked immunosorbent assay (ELISA) methods for the detection of aflatoxin in spice paprika matrix. We have also assessed applicability of the QuEChERS method prior to ELISA measurements, and the results were compared to those obtained by traditional solvent extraction followed by immunoaffinity clean-up. The AFB1 content of sixty commercial spice paprika samples from different countries were measured with the developed and optimized OWLS immunosensor. Comparing the results from the indirect immunosensor to that obtained by HPLC or ELISA provided excellent correlation (with regression coefficients above 0.94) indicating that the competitive OWLS immunosensor has a potential for quick determination of aflatoxin B1 in paprika samples. PMID:27283719

  9. An investigation of the well-water quality: immunosensor for pathogenic Pseudomonas aeruginosa detection based on antibody-modified poly(pyrrole-3 carboxylic acid) screen-printed carbon electrode.

    PubMed

    Bekir, Karima; Bousimma, Feriel; Barhoumi, Houcine; Fedhila, Kais; Maaref, Abderrazak; Bakhrouf, Amina; Ben Ouada, Hafedh; Namour, Philippe; Jaffrezic-Renault, Nicole; Ben Mansour, Hedi

    2015-12-01

    In this report, we describe a new immunosensor designed for the detection and the quantification of Pseudomonas aeruginosa bacteria in water. The developed biosensing system was based on the immobilization of purified polyclonal anti P. aeruginosa antibodies on electropolymerized poly(pyrrole-3-carboxylic acid)/glassy carbon electrode. The building of the immunosensor step by step was evaluated by electrochemical measurements such as cyclic voltammetry (CV) and impedance spectroscopy (EIS). The electrochemical signature of the immunosensor was established by the change of the charge transfer resistance when the bacteria suspended in solution became attached to the immobilized antibodies. As a result, stable and high sensitive impedimetric immunosensor was obtained with a sensitivity of 0.19 kΩ/decade defined in the linear range from 10(1) to 10(7) CFU/mL of cellular concentrations. A low detection limit was obtained for the P. aeruginosa bacteria and a high selectivity when other bacteria were occasioned as well as Escherichia coli. The developed immunosensor was applied in detecting pathogenic P. aeruginosa in well-water. PMID:26178830

  10. Immunosensor based on electrodeposition of gold-nanoparticles and ionic liquid composite for detection of Salmonella pullorum.

    PubMed

    Wang, Dan; Dou, Wenchao; Zhao, Guangying; Chen, Yan

    2014-11-01

    In order to increase the reproducibility and stability of electrochemical immunosensor, which is a key issue for its application and popularization, an accurate and stable immunosensor for rapid detection of Salmonella pullorum (S. pullorum) was proposed in this study. The immunosensor was fabricated by modifying Screen-printed Carbon Electrode (SPCE) with electrodeposited gold nanoparticles (AuNPs), HRP-labeled anti-S. pullorum and ionic liquids (ILs) (AuNP/HRP/IL). AuNPs are electrodeposited on the working electrode surface to increase the amount of antibodies that bind to the electrode and then modified with ILs to protect the antibodies from being inactivated in the test environment and maintain their biological activity and the stability of the detection electrode. The electrochemical characteristics of the stepwise modified electrodes and the detection of S. pullorum were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). As shown in the results of the experiments, AuNPs with unique electrochemical properties as well as biocompatibility characteristics have been proven to be able to strengthen the antibody combination effectively and to increase the electrochemical response signal. In addition, a crucial assessment regarding implementation of stability and reproducibility analysis of a range of immunosensors is provided. We found that application of AuNPs/ILs in the immune modified electrodes showed obvious improvement when compared with other groups. Given their high levels of reproducibility, stability, target specificity and sensitivity, AuNPs and ILs were considered to be excellent elements for electrode modification. PMID:25193438

  11. A highly sensitive immunosensor for calmodulin assay based on enhanced biocatalyzed precipitation adopting a dual-layered enzyme strategy.

    PubMed

    Fu, Ying; Liu, Kai; Sun, Qianqian; Lin, Bin; Lu, Danqin; Xu, Zhiai; Hu, Chen; Fan, Guangjian; Zhang, Shengping; Wang, Chuangui; Zhang, Wen

    2014-06-15

    Calmodulin (CaM) is a ubiquitous protein in eukaryotic cells, and it plays an important role in cancer progression. In this paper, a highly sensitive immunosensor adopting a dual-layered enzyme strategy was proposed for electrochemical detection of CaM. This immunosensor was constructed by introducing honeycomb-like mesoporous carbon (HMPC) as a sensor platform to sequentially immobilize antibody (Ab1), CaM and a multi-functionalized label. The label (HRP-PAupc-Ab1) was synthesized by covalently binding Ab1 and horseradish peroxidase (HRP) to poly(acrylic acid)-functionalized Au popcorn (PAupc) nanoparticles. A novel dual-layered enzyme strategy was employed by incubating HRP-secondary antibody (HRP-Ab2) onto the label surface and the enhanced biocatalyzed precipitation was therefore induced. This immunosensor exhibited satisfactory analytical performances for CaM detection with a linear response ranging from 5.0 pg mL(-1) to 100 ng mL(-1) and a detection limit of 1.5 pg mL(-1). The immunosensor has also been successfully applied to the CaM analysis in two cancer cells (HepG2 and MCF-7) with high sensitivity, which has shown great potency for cancer study. PMID:24508817

  12. Ultrasensitive electrochemical immunosensor based on dual signal amplification process for p16(INK4a) cervical cancer detection in clinical samples.

    PubMed

    Duangkaew, Pattasuda; Tapaneeyakorn, Satita; Apiwat, Chayachon; Dharakul, Tararaj; Laiwejpithaya, Somsak; Kanatharana, Proespichaya; Laocharoensuk, Rawiwan

    2015-12-15

    The p16(INK4a) (p16) is a cyclin-dependent kinase inhibitor, which has been evaluated in several studies as a diagnostic marker of cervical cancer. Immunostaining using p16 specific antibody has confirmed an over-expression of p16 protein in cervical cancer cells and its association with disease progression. This article reports an ultrasensitive electrochemical immunosensor for specific detection of p16 and demonstrates its performance for detection of solubilized p16 protein in cell lysates obtained from patients. Sandwich-based immunoreaction couple with double signal amplification strategy based on catalytic enlargement of particle tag was used for high sensitivity and specificity. The conditions were optimized to create an immunoassay protocol. Disposable screen-printed electrode modified with capture antibodies (Ab1) was selected for further implementation towards point-of-care diagnostics. Small gold nanoparticles (15 nm diameter) conjugated with detection antibodies (Ab2) were found to better serve as a detection label due to limited interference with antigen-antibody interaction. Double signal enhancement was performed by sequential depositions of gold and silver layers. This gave the sensitivity of 1.78 μA mL(ng GST-p16)(-1) cm(-2) and detection limit of 1.3 ng mL(-1) for GST-p16 protein which is equivalent to 0.49 ng mL(-1) for p16 protein and 28 cells for HeLa cervical cancer cells. In addition to purified protein, the proposed immunosensor effectively detected elevated p16 level in cervical swab samples obtained from 10 patients with positive result from standard Pap smear test, indicating that an electrochemical immunosensors hold an excellent promise for detection of cervical cancer in clinical setting. PMID:26201985

  13. Development of a Fluorescent Based Immunosensor for the Serodiagnosis of Canine Leishmaniasis Combining Immunomagnetic Separation and Flow Cytometry

    PubMed Central

    Sousa, Susana; Cardoso, Luís; Reed, Steven G.; Reis, Alexandre B.; Martins-Filho, Olindo A.; Silvestre, Ricardo; Cordeiro da Silva, Anabela

    2013-01-01

    Background An accurate diagnosis is essential for the control of infectious diseases. In the search for effective and efficient tests, biosensors have increasingly been exploited for the development of new and highly sensitive diagnostic methods. Here, we describe a new fluorescent based immunosensor comprising magnetic polymer microspheres coated with recombinant antigens to improve the detection of specific antibodies generated during an infectious disease. As a challenging model, we used canine leishmaniasis due to the unsatisfactory sensitivity associated with the detection of infection in asymptomatic animals where the levels of pathogen-specific antibodies are scarce. Methodology Ni-NTA magnetic microspheres with 1,7 µm and 8,07 µm were coated with the Leishmania recombinant proteins LicTXNPx and rK39, respectively. A mixture of equal proportions of both recombinant protein-coated microspheres was used to recognize and specifically bind anti-rK39 and anti-LicTNXPx antibodies present in serum samples of infected dogs. The microspheres were recovered by magnetic separation and the percentage of fluorescent positive microspheres was quantified by flow cytometry. Principal Findings A clinical evaluation carried out with 129 dog serum samples using the antigen combination demonstrated a sensitivity of 98,8% with a specificity of 94,4%. rK39 antigen alone demonstrated a higher sensitivity for symptomatic dogs (96,9%), while LicTXNPx antigen showed a higher sensitivity for asymptomatic (94,4%). Conclusions Overall, our results demonstrated the potential of a magnetic microsphere associated flow cytometry methodology as a viable tool for highly sensitive laboratorial serodiagnosis of both clinical and subclinical forms of canine leishmaniasis. PMID:23991232

  14. A quantum dot based electrochemiluminescent immunosensor for the detection of pg level phenylethanolamine A using gold nanoparticles as substrates and electron transfer accelerators.

    PubMed

    Yan, Panpan; Zhang, Jing; Tang, Qinghui; Deng, Anping; Li, Jianguo

    2014-09-01

    This study reports the development of an electrochemiluminescent (ECL) immunosensor for ultrasensitive detection of phenylethanolamine A (PA) based on CdSe quantum dots (QDs) and gold nanoparticles (GNPs). The GNPs/ovalbumin-PA/anti-PA-QD immunosensor was fabricated layer by layer using GNPs as substrates and electron transport accelerators. The use of GNPs greatly enhanced the sensitivity for detecting PA due to the excellent electron transportation ability and the large surface area of GNP carriers allowing several binding events of ovalbumin-PA on each nanosphere. Transmission electron microscopy images (TEM), photoluminescence spectra, ultraviolet-visible absorption spectra and dynamic light scattering (DLS) were used to characterize the QDs and GNPs. The sensor was characterized with electrochemical impedance spectra (EIS), and a strong ECL emission of the modified electrode could be observed during the cathodic process of S2O8(2-) and QDs in air-saturated PBS buffer containing 0.1 M K2S2O8 and 0.1 M KCl (pH 7.4). With a competitive immunoassay format, the ECL signal depended linearly on the logarithm of the phenylethanolamine A concentration within a range of 0.02 ng mL(-1) to 50 ng mL(-1), and the detection limit was 0.0047 ng mL(-1), much lower than those reported in the literature. This ECL immunosensor is rapid, simple and sensitive with acceptable precision, and it will extend the application of QD ECL in immunoassays of β-agonists and open new avenues for the detection of food additive residues in the future. PMID:25011489

  15. Electrochemical immunosensor based on bismuth nanocomposite film and cadmium ions functionalized titanium phosphates for the detection of anthrax protective antigen toxin.

    PubMed

    Sharma, Mukesh K; Narayanan, J; Upadhyay, Sanjay; Goel, Ajay K

    2015-12-15

    Bacillus anthracis is a bioterrorism agent classified by the Centers for Disease Control and Prevention (CDC). Herein, a novel electrochemical immunosensor for the sensitive, specific and easy detection of anthrax protective antigen (PA) toxin in picogram concentration was developed. The immunosensor consists of (i) a Nafion-multiwall carbon nanotubes-bismuth nanocomposite film modified glassy carbon electrodes (BiNPs/Nafion-MWCNTs/GCE) as a sensing platform and (ii) titanium phosphate nanoparticles-cadmium ion-mouse anti-PA antibodies (TiP-Cd(2+)-MαPA antibodies) as signal amplification tags. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), thermogravimmetric analysis (TGA), Fourier transform-infra red spectroscopy (FT-IR), zeta-potential analysis, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were employed to characterize the synthesized TiP nanoparticles and modified electrode surfaces. The immunosensing performance of BiNPs/Nafion-MWCNTs/GCE was evaluated based on sandwich immunoassay protocol. A square wave voltammetry (SWV) scan from -1.2 to -0.3 V in HAc-NaAc buffer solution (pH 4.6) without stripping process was performed to record the electrochemical responses at -0.75 V corresponding to high content of Cd(2+) ions loaded in TiP nanoparticles for the measurement of PA toxin. Under optimal conditions, the currents increased with increasing PA toxin concentrations in spiked human serum samples and showed a linear range from 0.1 ng/ml to 100 ng/ml. The limit of detection of developed immunosensor was found to be 50 pg/ml at S/N=3. The total time of analysis was 35 min. PMID:26148674

  16. Novel gold nanocluster electrochemiluminescence immunosensors based on nanoporous NiGd-Ni2O3-Gd2O3 alloys.

    PubMed

    Lv, Xiaohui; Ma, Hongmin; Wu, Dan; Yan, Tao; Ji, Lei; Liu, Yixin; Pang, Xuehui; Du, Bin; Wei, Qin

    2016-01-15

    Herein, three-dimensional nanoporous NiGd alloy (NP-NiGd) was prepared by selectively dealloy Al from NiGdAl alloy in mild alkaline solution, then Ni2O3 and Gd2O3 grew further on the surface of NP-NiGd to obtain the NP-NiGd-Ni2O3-Gd2O3. On this basis, NP-NiGd-Ni2O3-Gd2O3 was further functionalized with gold nanoparticles (NP-NiGd-Ni2O3-Gd2O3@Au) and acted as sensor platform to fabricate a novel electrochemiluminescence (ECL) immunosensor. Bovine serum albumin protected gold nanoclusters (AuNCs@BSA) were prepared and acted as illuminant. AuNCs@BSA modified graphene oxide (GO/AuNCs@BSA) were used as labels of second antibody. In order to characterize the performance of the ECL immunosensor, carcino embryonie antigen (CEA) was used as the model to complete the experiments. Due to the good performances of NP-NiGd-Ni2O3-Gd2O3@Au (high surface area, excellent electron conductivity) and AuNCs@BSA (low toxicity, biocompatibility, easy preparation and good water solubility), the ECL immunosensor exhibited a wide range from 10(-4) to 5ng/mL with a detection limit of 0.03pg/mL (S/N=3). The immunosensor with excellent stability, acceptable repeatability and selectivity provided a promising method to detect CEA in human serum sample sensitively. PMID:26318782

  17. Ultrasensitive electrochemical immunosensor based on horseradish peroxidase (HRP)-loaded silica-poly(acrylic acid) brushes for protein biomarker detection.

    PubMed

    Zhao, Yan; Zheng, Yiqun; Kong, Rongmei; Xia, Lian; Qu, Fengli

    2016-01-15

    We report an ultrasensitive electrochemical immunosensor designed for the detection of protein biomarkers using horseradish peroxidase (HRP)-loaded silica-poly(acrylic acid) brushes (SiO2-SPAABs) as labels. HRP could be efficiently and stably accommodated in the three-dimensional architecture of the SiO2-SPAABs and the SiO2-SPAABs-HRP exhibited high catalytic performance towards o-phenylenediamine (OPD) oxidation in the presence of H2O2, which resulted in significant differential pulse voltammetric (DPV) response change and color change. Using human IgG (HIgG) as a model analyte, a sandwich-type immunosensor was constructed. In particular, graphene oxide (GO) and SiO2-SPAABs-HRP were used to immobilize capture antibody (Ab1) and bind a layer of detection antibody (Ab2), respectively. The current biosensor exhibited a good linear response of HIgG from 100pg/mL to 100μg/mL with a detection limit of 50pg/mL (S/N=5). The sensitivity was 6.70-fold higher than the conventional enzyme-linked immunosorbent assays. The immunosensor results were validated through the detection of HIgG in serum samples. PMID:26342574

  18. An ultrasensitive label-free electrochemical immunosensor based on signal amplification strategy of multifunctional magnetic graphene loaded with cadmium ions

    PubMed Central

    Li, Faying; Li, Yueyun; Dong, Yunhui; Jiang, Liping; Wang, Ping; Liu, Qing; Liu, Hui; Wei, Qin

    2016-01-01

    Herein, a novel and ultrasensitive label-free electrochemical immunosensor was proposed for quantitative detection of human Immunoglobulin G (IgG). The amino functionalized magnetic graphenes nanocomposites (NH2-GS-Fe3O4) were prepared to bond gold and silver core-shell nanoparticles (Au@Ag NPs) by constructing stable Au-N and Ag-N bond between Au@Ag NPs and -NH2. Subsequently, the Au@Ag/GS-Fe3O4 was applied to absorb cadmium ion (Cd2+) due to the large surface area, high conductivity and exceptional adsorption capability. The functional nanocomposites of gold and silver core-shell magnetic graphene loaded with cadmium ion (Au@Ag/GS-Fe3O4/Cd2+) can not only increase the electrocatalytic activity towards hydrogen peroxide (H2O2) but also improve the effective immobilization of antibodies because of synergistic effect presented in Au@Ag/GS-Fe3O4/Cd2+, which greatly extended the scope of detection. Under the optimal conditions, the proposed immunosensor was used for the detection of IgG with good linear relation in the range from 5 fg/mL to 50 ng/mL with a low detection limit of 2 fg/mL (S/N = 3). Furthermore, the proposed immunosensor showed high sensitivity, special selectivity and long-term stability, which had promising application in bioassay analysis. PMID:26880596

  19. Ultrasensitive sandwich-type electrochemical immunosensor based on trimetallic nanocomposite signal amplification strategy for the ultrasensitive detection of CEA.

    PubMed

    Tian, Lihui; Liu, Li; Li, Yueyuan; Wei, Qin; Cao, Wei

    2016-01-01

    A novel and ultrasensitive sandwich-type electrochemical immunosensor was designed for the quantitative detection of carcino-embryonic antigen (CEA). This immunosensor was developed by using the trimetallic NiAuPt nanoparticles on graphene nanosheets (NGs) nanosheets (NiAuPt-NGs) as excellent labels and β-cyclodextrin functionalized reduced graphene oxide nanosheets (CD-NGs) as the platform. The CD-NGs with high specific surface area good biocompatibility and the ideal dispersibility was used to capture the primary antibodies (Ab1) efficiently. The trimetallic NiAuPt-NGs nanocomposites were used as the labels for signal amplification, showing better electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2), which is much better than that the monometallic Pt-NGs, bimetallic NiPt-NGs and AuPt-NGs due to the synergetic effect presented in NiAuPt-NGs. The NiAuPt-NGs nanocomposites consist of tightly coupled nanostructures of Au, Ni and Pt, which have neither an alloy nor a core-shell structure. Under the optimal conditions, a linear range from 0.001-100 ng/mL and a low detection limit of 0.27 pg/mL were obtained for CEA. The proposed electrochemical sandwich-type immunosensor may have a promising application in bioassay and it enriches the electrochemical immunoassays. PMID:27488806

  20. Ultrasensitive sandwich-type electrochemical immunosensor based on trimetallic nanocomposite signal amplification strategy for the ultrasensitive detection of CEA

    PubMed Central

    Tian, Lihui; Liu, Li; Li, Yueyuan; Wei, Qin; Cao, Wei

    2016-01-01

    A novel and ultrasensitive sandwich-type electrochemical immunosensor was designed for the quantitative detection of carcino-embryonic antigen (CEA). This immunosensor was developed by using the trimetallic NiAuPt nanoparticles on graphene nanosheets (NGs) nanosheets (NiAuPt-NGs) as excellent labels and β-cyclodextrin functionalized reduced graphene oxide nanosheets (CD-NGs) as the platform. The CD-NGs with high specific surface area good biocompatibility and the ideal dispersibility was used to capture the primary antibodies (Ab1) efficiently. The trimetallic NiAuPt-NGs nanocomposites were used as the labels for signal amplification, showing better electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2), which is much better than that the monometallic Pt-NGs, bimetallic NiPt-NGs and AuPt-NGs due to the synergetic effect presented in NiAuPt-NGs. The NiAuPt-NGs nanocomposites consist of tightly coupled nanostructures of Au, Ni and Pt, which have neither an alloy nor a core-shell structure. Under the optimal conditions, a linear range from 0.001–100 ng/mL and a low detection limit of 0.27 pg/mL were obtained for CEA. The proposed electrochemical sandwich-type immunosensor may have a promising application in bioassay and it enriches the electrochemical immunoassays. PMID:27488806

  1. Electrochemical immunosensor for detecting the spore wall protein of Nosema bombycis based on the amplification of hemin/G-quadruplex DNAzyme concatamers functionalized Pt@Pd nanowires.

    PubMed

    Wang, Qin; Song, Yue; Chai, Yaqin; Pan, Guoqing; Li, Tian; Yuan, Yali; Yuan, Ruo

    2014-10-15

    In this work, an ultrasensitive electrochemical immunosensor for detecting the Pebrine disease related spore wall protein of Nosema bombycis (SWP N.b) was fabricated based on the amplification of hemin/G-quadruplex functionalized Pt@Pd nanowires (Pt@PdNWs). The synthesized Pt@PdNWs possessed large surface area, which could effectively improve the immobilization amount of hemin/G-quadruplex DNAzyme concatamers produced via hybridization chain reaction (HCR). In the presence of SWP N.b, the hemin/G-quadruplex labeled Pt@PdNWs bioconjugations was captured on electrode surface and thus obtained electrochemical signal. After the addition of NADH into the electrolytic cell, hemin/G-quadruplex firstly acted as an NADH oxidase to locally produce H2O2 in the presence of dissolved O2. Then, the generated H2O2 would be quickly reduced via hemin/G-quadruplex as a horseradish peroxidase mimicking (HRP-mimicking) DNAzyme, which finally promoted the self-redox reaction of hemin/G-quadruplex and a greatly enhanced electrochemical signal was obtained. Furthermore, Pt@PdNWs with excellent electrocatalytic performance could also amplify electrochemical signal. With these amplification factors, the electrochemical immunosensor exhibited a wide linear range from 0.001 ng mL(-1) to 100 ng mL(-1) with a detection limit (LOD) of 0.24 pg mL(-1), providing a new promise for the diagnosis of Pebrine disease. PMID:24787126

  2. Ionic liquid functionalized graphene based immunosensor for sensitive detection of carbohydrate antigen 15-3 integrated with Cd(2+)-functionalized nanoporous TiO2 as labels.

    PubMed

    Zhao, Lifang; Wei, Qin; Wu, Hua; Dou, Jinke; Li, He

    2014-09-15

    A novel electrochemical immunosensor for sensitive detection of carbohydrate antigen 15-3 (CA15-3) based on dual signal amplification strategy of ionic liquid functionalized graphene and Cd(2+)-functionalized nanoporous TiO2 (f-TiO2-Cd(2+)) has been developed. Ionic liquid functionalized graphene was used to anchor primary CA15-3 antibody (Ab1). f-TiO2-Cd(2+) was employed to immobilize secondary cancer antigen 15-3 (CA15-3) antibody (Ab2) and the resulting nanocomposite (Ab2-f-TiO2-Cd(2+)) was used as trace tag for signal amplification. The fabricated immumosensor displayed a wide range of linear response (0.02-60 U/mL), ultra-low detection limit (0.008 U/mL), good reproducibility, selectivity and stability towards CA15-3. The good performance of the immunosensor can be attributed to (1) high surface-to-volume ratio of graphene which allows high-level immobilization of Ab1, (2) excellent biocompatibility and electron transfer rate originating from ionic liquid functionalized graphene, (3) a highly specific surface area of nanoporous TiO2 that facilitates the adsorption of high amount of Cd(2+) for signal amplification. PMID:24690564

  3. A sensitive electrochemiluminescence immunosensor based on luminophore capped Pd@Au core-shell nanoparticles as signal tracers and ferrocenyl compounds as signal enhancers.

    PubMed

    Liu, Yuting; Wang, Haijun; Xiong, Chengyi; Yuan, Yali; Chai, Yaqin; Yuan, Ruo

    2016-07-15

    In this work, N-(aminobutyl)-N-(ethylisoluminol) (ABEI), an analogue of luminol, is served as both the reductant and luminescence reagent to synthesize ABEI capped Pd@Au core-shell nanoparticles (ABEI-Pd@AuNPs). The nanoparticles not only exhibit inherent electrochemiluminescence (ECL) property, but also possess advantages of noble-metal nanomaterials such as outstanding electronic property, high specific surface area and good biocompatibility. In order to enhance the luminescence efficiency, ferrocene monocarboxylic acid (Fc) as catalyzer is grafted on the surface of ABEI-Pd@AuNPs with the aid of l-cysteine (l-Cys). When the Fc is electrochemically oxidized to ferricinium cation species (Fc(+)), the decomposition of H2O2 which existed in detection solution can be catalyzed by Fc(+) to generate oxygen-related free radicals, resulting effective signal amplification for ABEI-H2O2 system. For potential applications, the Pd@Au core-shell nanoparticles bifunctionalized by ABEI and catalyzer are employed as nano-carriers to immobilize detection antibody (Ab2). Based on sandwiched immunoreactions, a "signal-on" ECL immunosensor is developed for detection of human collagen type IV (Col IV), a potential biomarker associated with diabetic nephropathy. Consequently, the proposed immunosensor provides a wide linear detection ranging from 1pgmL(-1) to 10ngmL(-1) with a relatively low detection limit of 0.3pgmL(-1) (S/N=3). PMID:26985586

  4. An ultrasensitive label-free immunosensor based on CdS sensitized Fe-TiO2 with high visible-light photoelectrochemical activity.

    PubMed

    Fan, Dawei; Wu, Dan; Cui, Jiali; Chen, Yucheng; Ma, Hongmin; Liu, Yixin; Wei, Qin; Du, Bin

    2015-12-15

    An ultrasensitive label-free immunosensor was developed for the detection of squamous cell carcinoma antigen (SCCA) based on CdS sensitized Fe-TiO2 nanocomposites with high visible-light photoelectrochemical (PEC) activity. In this protocol, ascorbic acid was used as an efficient electron donor for scavenging photogenerated holes. The Fe-doped TiO2 improved the absorption of TiO2 in the visible light region and promoted the photocurrent production distinctly. Especially, 0.1% Fe-TiO2 showed the highest photocurrent, which was 7.4 times that of pure TiO2. Carboxyl functionalized CdS nanoparticles (CdS NPs) were bonded onto Fe-TiO2 composite through interactions between carboxyl groups and TiO2, which further enhanced the PEC signal strength by approximately 2.9 fold compared with 0.1% Fe-TiO2. The specific binding between SCCA and antibody resulted in a decrease in photocurrent intensity and the intensity decreased linearly with the logarithm of SCCA concentration in the range of 0.001-75 ng mL(-1) with a detection limit of 0.22 pg mL(-1). The developed CdS enhanced Fe-TiO2 PEC immunosensor exhibited high sensitivity, good reproducibility, and low cost, which may have potential applications in clinical diagnosis of cancers, aptasensors, photocatalysis, and other related fields. PMID:26233640

  5. Recent advances in immunosensor for narcotic drug detection

    PubMed Central

    Gandhi, Sonu; Suman, Pankaj; Kumar, Ashok; Sharma, Prince; Capalash, Neena; Suri, C. Raman

    2015-01-01

    Introduction: Immunosensor for illicit drugs have gained immense interest and have found several applications for drug abuse monitoring. This technology has offered a low cost detection of narcotics; thereby, providing a confirmatory platform to compliment the existing analytical methods. Methods: In this minireview, we define the basic concept of transducer for immunosensor development that utilizes antibodies and low molecular mass hapten (opiate) molecules. Results: This article emphasizes on recent advances in immunoanalytical techniques for monitoring of opiate drugs. Our results demonstrate that high quality antibodies can be used for immunosensor development against target analyte with greater sensitivity, specificity and precision than other available analytical methods. Conclusion: In this review we highlight the fundamentals of different transducer technologies and its applications for immunosensor development currently being developed in our laboratory using rapid screening via immunochromatographic kit, label free optical detection via enzyme, fluorescence, gold nanoparticles and carbon nanotubes based immunosensing for sensitive and specific monitoring of opiates. PMID:26929925

  6. A novel self-enhanced electrochemiluminescence immunosensor based on hollow Ru-SiO2@PEI nanoparticles for NSE analysis

    NASA Astrophysics Data System (ADS)

    Zhou, Limin; Huang, Jianshe; Yu, Bin; You, Tianyan

    2016-02-01

    Poly(ethylenimine) (PEI) and Ru(bpy)32+-doped silica (Ru-SiO2) nanoparticles were simply mixed together to prepare a novel self-enhanced electrochemiluminescence (ECL) composite of Ru-SiO2@PEI. The hollow Ru-SiO2@PEI nanoparticles were used to build an ECL immunosensor for the analysis of neuron specific enolase (NSE). PEI not only assembled on the surface of Ru-SiO2 nanoparticles through the electrostatic interaction to act as co-reactant for Ru(bpy)32+ ECL, but also provided alkaline condition to etch the Ru-SiO2 nanoparticles to form the hollow Ru-SiO2@PEI nanoparticles with porous shell. The unique structure of the Ru-SiO2@PEI nanoparticles loaded both a large amount of Ru(bpy)32+ and its co-reactant PEI at the same time, which shortened the electron-transfer distance, thereby greatly enhanced the luminous efficiency and amplified the ECL signal. The developed immunosensor showed a wide linear range from 1.0 × 10-11 to 1.0 × 10-5 mg mL-1 with a low detection limit of 1.0 × 10-11 mg mL-1 for NSE. When the immunosensor was used for the determination of NSE in clinical human serum, the results were comparable with those obtained by using enzyme-linked immunosorbent assay (ELISA) method. The proposed method provides a promising alternative for NSE analysis in clinical samples.

  7. A novel self-enhanced electrochemiluminescence immunosensor based on hollow Ru-SiO2@PEI nanoparticles for NSE analysis

    PubMed Central

    Zhou, Limin; Huang, Jianshe; Yu, Bin; You, Tianyan

    2016-01-01

    Poly(ethylenimine) (PEI) and Ru(bpy)32+-doped silica (Ru-SiO2) nanoparticles were simply mixed together to prepare a novel self-enhanced electrochemiluminescence (ECL) composite of Ru-SiO2@PEI. The hollow Ru-SiO2@PEI nanoparticles were used to build an ECL immunosensor for the analysis of neuron specific enolase (NSE). PEI not only assembled on the surface of Ru-SiO2 nanoparticles through the electrostatic interaction to act as co-reactant for Ru(bpy)32+ ECL, but also provided alkaline condition to etch the Ru-SiO2 nanoparticles to form the hollow Ru-SiO2@PEI nanoparticles with porous shell. The unique structure of the Ru-SiO2@PEI nanoparticles loaded both a large amount of Ru(bpy)32+ and its co-reactant PEI at the same time, which shortened the electron-transfer distance, thereby greatly enhanced the luminous efficiency and amplified the ECL signal. The developed immunosensor showed a wide linear range from 1.0 × 10−11 to 1.0 × 10−5 mg mL−1 with a low detection limit of 1.0 × 10−11 mg mL−1 for NSE. When the immunosensor was used for the determination of NSE in clinical human serum, the results were comparable with those obtained by using enzyme-linked immunosorbent assay (ELISA) method. The proposed method provides a promising alternative for NSE analysis in clinical samples. PMID:26916963

  8. Microfluidic immunosensor with micromagnetic beads coupled to carbon-based screen-printed electrodes (SPCEs) for determination of Botrytis cinerea in tissue of fruits.

    PubMed

    Fernández-Baldo, Martín A; Messina, Germán A; Sanz, Maria I; Raba, Julio

    2010-11-10

    A wide range of plant species, including economically important crops such as vegetables, ornamentals, bulbs, and fundamentally fruits, can be affected by gray mold caused by the fungal pathogen Botrytis cinerea . This paper describes the development of a microfluidic immunosensor with micromagnetic beads (MMBs) coupled to carbon-based screen-printed electrodes (SPCEs) for the rapid and sensitive quantification of B. cinerea in apple (Red Delicious), table grape (pink Moscatel), and pear (William's) tissues. The detection of B. cinerea was carried out using a competitive immunoassay method based on the use of purified B. cinerea antigens immobilized on 3-aminopropyl-modified MMBs. The total assay time was 40 min, and the calculated detection limit was 0.008 μg mL(-1). Moreover, the intra- and interassay coefficients of variation were below 7%. The developed method allowed detects B. cinerea even in asymptomatic fruits and promises to be particularly useful for application in the agricultural industry. PMID:20931959

  9. Nano-magnetic immunosensor based on staphylococcus protein a and the amplification effect of HRP-conjugated phage antibody.

    PubMed

    Mu, Xihui; Tong, Zhaoyang; Huang, Qibin; Liu, Bing; Liu, Zhiwei; Hao, Lanqun; Zhang, Jinping; Gao, Chuan; Wang, Fenwei

    2015-01-01

    In this research, super-paramagnetic Fe3O4 nanoparticles (magnetic particles) were coated with Staphylococcus protein A (SPA) and coupled with polyclonal antibody (pcAb) to construct magnetic capturing probes, and HRP-conjugated phage antibody was then used as specific detecting probe to design a labeled immunosensor for trace detection of Staphylococcus aureus enterotoxin B (SEB). The linear detection range of the sensor was 0.008~125 µg/L, the regression equation was Y = 0.487X + 1.2 (R = 0.996, N = 15, p < 0.0001), the limit of detection (LOD) was 0.008 µg/L, and the limit of quantification (LOQ) was 0.008 µg/L. HRP-conjugated phage antibody, SPA and magnetic particles can enhance the sensitivity 4-fold, 3-fold and 2.6-fold higher, respectively. Compared with conventional double-antibody sandwich ELISA, the detection sensitivity of the sensor was 31-fold higher resulting from the integrated amplifying effect. The immunosensor integrates the unique advantages of SPA-oriented antibody as magnetic capturing probe, HRP-conjugated phage antibody as detecting probe, magnetic separation immunoassay technique, and several other advanced techniques, so it achieves high sensitivity, specificity and interference-resistance. It is proven to be well suited for analysis of trace SEB in various environmental samples with high recovery rate and reproducibility. PMID:25671509

  10. A Novel Sandwich Electrochemical Immunosensor Based on the DNA-Derived Magnetic Nanochain Probes for Alpha-Fetoprotein

    PubMed Central

    Gan, Ning; Jia, Liyong; Zheng, Lei

    2011-01-01

    One novel electrochemical immunosensor was constructed by immobilizing capture antibody of alpha-fetoprotein (AFP Ab1) on a nafion/nanogold-particle modified glassy carbon electrode. With a sandwich immunoassay, one DNA-derived magnetic nanoprobe, simplified as DNA/(ZMPs—HRP-AFP Ab2)n, was employed for the detection of AFP. The fabricated procedure of the proposed biosensor was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The performance and factors influencing the performance of the biosensor were also evaluated. Under optimal conditions, the developed biosensor exhibited a well-defined electrochemical behavior toward the reduction of AFP ranging from 0.01 to 200 ng/mL with a detection limit of 4 pg/mL (S/N = 3). The biosensor was applied to the determination of AFP in serum with satisfactory results. It is important to note that the sandwich nanochainmodified electro-immunosensor provided an alternative substrate for the immobilization of other tumor markers. PMID:22013390

  11. Nano-Magnetic Immunosensor Based on Staphylococcus Protein A and the Amplification Effect of HRP-Conjugated Phage Antibody

    PubMed Central

    Mu, Xihui; Tong, Zhaoyang; Huang, Qibin; Liu, Bing; Liu, Zhiwei; Hao, Lanqun; Zhang, Jinping; Gao, Chuan; Wang, Fenwei

    2015-01-01

    In this research, super-paramagnetic Fe3O4 nanoparticles (magnetic particles) were coated with Staphylococcus protein A (SPA) and coupled with polyclonal antibody (pcAb) to construct magnetic capturing probes, and HRP-conjugated phage antibody was then used as specific detecting probe to design a labeled immunosensor for trace detection of Staphylococcus aureus enterotoxin B (SEB). The linear detection range of the sensor was 0.008∼125 μg/L, the regression equation was Y = 0.487X + 1.2 (R = 0.996, N = 15, p < 0.0001), the limit of detection (LOD) was 0.008 μg/L, and the limit of quantification (LOQ) was 0.008 μg/L. HRP-conjugated phage antibody, SPA and magnetic particles can enhance the sensitivity 4-fold, 3-fold and 2.6-fold higher, respectively. Compared with conventional double-antibody sandwich ELISA, the detection sensitivity of the sensor was 31-fold higher resulting from the integrated amplifying effect. The immunosensor integrates the unique advantages of SPA-oriented antibody as magnetic capturing probe, HRP-conjugated phage antibody as detecting probe, magnetic separation immunoassay technique, and several other advanced techniques, so it achieves high sensitivity, specificity and interference-resistance. It is proven to be well suited for analysis of trace SEB in various environmental samples with high recovery rate and reproducibility. PMID:25671509

  12. Three-dimensional electrochemical immunosensor for sensitive detection of carcinoembryonic antigen based on monolithic and macroporous graphene foam.

    PubMed

    Liu, Jiyang; Wang, Jiao; Wang, Tianshu; Li, Dan; Xi, Fengna; Wang, Jin; Wang, Erkang

    2015-03-15

    A high performance three-dimensional (3D) electrochemical immunosensor was developed for sensitive detection of the tumor biomarker, carcinoembryonic antigen (CEA). Monolithic and macroporous graphene foam grown by chemical vapor deposition (CVD) served as the scaffold of the free-standing 3D electrode. Immuno-recognition interface was fabricated via simple and non-covalent immobilization of antibody using lectin-mediated strategy. Briefly, the well-known lectin macromolecule (concanavalin A, Con A) monolayer was functionalized on 3D graphene (3D-G) using in-situ polymerized polydopamine as the linker. Then the widely used horseradish peroxidase (HRP)-labeled antibody (anti-CEA) in immunoassays was efficiently immobilized to demonstrate the recognition interface via the biospecific affinity of lectin with sugarprotein. The 3D immunosensor is able to detect CEA with a wide linear range (0.1-750.0ngml(-1)), low detection limit (~90pgml(-1) at a signal-to-noise ratio of 3), and short incubation time (30min). Furthermore, this biosensor was used for the detection of the CEA level in real serum samples. PMID:25461170

  13. Sensitive Immunosensor for Cancer Biomarker Based on Dual Signal Amplification Strategy of Graphene Sheets and Multi-Enzyme Functionalized Carbon Nanospheres

    SciTech Connect

    Du, Dan; Zou, Zhexiang; Shin, Yongsoon; Wang, Jun; Wu, Hong; Engelhard, Mark H.; Liu, Jun; Aksay, Ilhan A.; Lin, Yuehe

    2010-03-30

    A novel electrochemical immunosensor for sensitive detection of cancer biomarker α fetoprotein (AFP) is described that uses a graphene sheet sensor platform and functionalized carbon nanospheres (CNSs) labeling with horseradish peroxidase-secondary antibodies (HRP-Ab2). Greatly enhanced sensitivity for the cancer biomarker is based on a dual signal amplification strategy: first, the synthesized CNSs yielded a homogeneous and narrow size distribution, which allowed several binding events of HRP-Ab2 on each nanosphere. Enhanced sensitivity was achieved by introducing the multi-bioconjugates of HRP-Ab2-CNSs onto the electrode surface through sandwich immunoreactions. Secondly, functionalized graphene sheets used for the biosensor platform increased the surface area to capture a large amount of primary antibodies (Ab1), thus amplifying the detection response. This amplification strategy is a promising platform for clinical screening of cancer biomarkers and point-of-care diagnostics.

  14. An electrochemical ELISA-like immunosensor for miRNAs detection based on screen-printed gold electrodes modified with reduced graphene oxide and carbon nanotubes.

    PubMed

    Tran, H V; Piro, B; Reisberg, S; Huy Nguyen, L; Dung Nguyen, T; Duc, H T; Pham, M C

    2014-12-15

    We design an electrochemical immunosensor for miRNA detection, based on screen-printed gold electrodes modified with reduced graphene oxide and carbon nanotubes. An original immunological approach is followed, using antibodies directed to DNA.RNA hybrids. An electrochemical ELISA-like amplification strategy was set up using a secondary antibody conjugated to horseradish peroxidase (HRP). Hydroquinone is oxidized into benzoquinone by the HRP/H2O2 catalytic system. In turn, benzoquinone is electroreduced into hydroquinone at the electrode. The catalytic reduction current is related to HRP amount immobilized on the surface, which itself is related to miRNA.DNA surface density on the electrode. This architecture, compared to classical optical detection, lowers the detection limit down to 10 fM. Two miRNAs were studied: miR-141 (a prostate biomarker) and miR-29b-1 (a lung cancer biomarker). PMID:24973539

  15. Multi-immunosensors based on electrolite-insulator-semiconductor structures for determination of some herbicides

    NASA Astrophysics Data System (ADS)

    Starodub, Nickolaj F.; Starodub, Valentyna M.; Krivenchuk, Vladimir E.; Shapovalenko, Valentyna F.

    2002-02-01

    New type of the multi-immune sensor was elaborated. It is based on electrolyte-insulator-semiconductors structures and intended for determination of such herbicides as simazine, atrazine and 2,4-D. The specific antibodies were immobilized on nitrocellulose disks, which were placed in measuring cells. The analysis was fulfilled by sequential saturation of antibodies, left unbound after their exposure to native herbicide in investigated sample, with labelled herbicide. If horse radish peroxidase (HRP) was used as label the sensitivity of this multi-immune sensor was about 5 and 1.25 (mu) g/L for simazine and 2,4-D, respectively. At the changing of HRP by (beta) -glucose oxidase the sensitivity of analysis of these herbicides increased approximately in 5 times. The linear plots of the registered concentrations were in the range of 1,0-150,0 and 0,25-150,0 ng/mL for simazine and 2,4-D respectively. It was recommended to use the developed immune sensor for wide screening of herbicides in environment. The ways for increasing of its sensitivity were proposed.

  16. Gold nanoparticles doped conducting polymer nanorod electrodes: ferrocene catalyzed aptamer-based thrombin immunosensor.

    PubMed

    Rahman, Md Aminur; Son, Jung Ik; Won, Mi-Sook; Shim, Yoon-Bo

    2009-08-15

    Au nanoparticles-doped conducting polymer nanorods electrodes (AuNPs/CPNEs) were prepared by coating Au nanorods (AuNRs) with a conducting polymer layer. The AuNRs were prepared through an electroless deposition method using the polycarbonate membrane (pore diameter, 50 nm, pore density, 6 x 10(8) pores/cm(2)) as a template. The AuNPs/CPNEs combining catalytic activity of ferrocene to ascorbic acid were used for the fabrication of an ultrasensitive aptamer sensor for thrombin detection. The AuNPs/3D-CPNEs were characterized employing cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Sandwiched immunoassay for alpha-human thrombin with NH(2)-functionalized-thrombin binding aptamer (Apt) immobilized on AuNPs/3D-CPNEs was studied through the electrocatalytic oxidation of ascorbic acid by the ferrocene moiety that was bound with an antithrombin antibody and attached with the Apt/3D-CPNEs probe through target binding. Various experimental parameters affecting thrombin detection were optimized, and the performance of the thrombin aptamer sensor was examined. The Apt/AuNPs/3D-CPNEs based thrombin sensor exhibited a wide dynamic range of 5-2000 ng L(-1) and a low detection limit of 5 ng L(-1) (0.14 pM). The selectivity and the stability of the proposed thrombin aptamer sensor were excellent, and it was tested in a real human serum sample for the detection of spiked concentrations of thrombin. PMID:20337374

  17. Detection of trichinosis using TSM immunosensor.

    PubMed

    He, F; Zhang, L; Liu, H

    2001-10-31

    A thickness shear mode (TSM) immunosensor was developed for detection of trichinosis in this paper; antibody was immobilized on to the surface of a quartz crystal precoated with styrene-butadiene-styrene (SBS) copolymer. The sensor interacted sensitively with trichinosis antigen and produced a change in resonant frequency of the quartz crystal. The fractal analysis was proposed for both processes. This method was applied to the detection of some samples with different amount antigen sera diluted by phosphate buffered saline (PBS) and good results were obtained. PMID:18968436

  18. Amperometric carbohydrate antigen 19-9 immunosensor based on three dimensional ordered macroporous magnetic Au film coupling direct electrochemistry of horseradish peroxidase.

    PubMed

    Zhang, Qi; Chen, Xiaojun; Tang, Yin; Ge, Lingna; Guo, Buhua; Yao, Cheng

    2014-03-01

    A sandwich-type electrochemical immunosensor for the detection of carbohydrate antigen 19-9 (CA 19-9) antigen based on the immobilization of primary antibody (Ab1) on three dimensional ordered macroporous magnetic (3DOMM) electrode, and the direct electrochemistry of horseradish peroxidase (HRP) that was used as both the label of secondary antibody (Ab2) and the blocking reagent. The 3DOMM electrode was fabricated by introducing core-shell Au-SiO2@Fe3O4 nanospheres onto the surface of three dimensional ordered macroporous (3DOM) Au electrode via the application of an external magnet. Au nanoparticles functionalized SBA-15 (Au@SBA-15) was conjugated to the HRP labeled secondary antibody (HRP-Ab2) through the Au-SH or Au-NH3(+) interaction, and HRP was also used as the block reagent. The formation of antigen-antibody complex made the combination of Au@SBA-15 and 3DOMM exhibit remarkable synergistic effects for accelerating direct electron transfer (DET) between HRP and the electrode. Under the optimal conditions, the DET current signal increased proportionally to CA 19-9 concentration in the range of 0.05 to 15.65 U mL(-1) with a detection limit of 0.01 U mL(-1). Moreover, the immunosensor showed high selectivity, good stability, satisfactory reproducibility and regeneration. Importantly, the developed method was used to assay clinical serum specimens, achieving a good relation with those obtained from the commercialized electrochemiluminescent method. PMID:24560371

  19. An immunosensor based on magnetic relaxation switch and polystyrene microparticle-induced immune multivalency enrichment system for the detection of Pantoea stewartii subsp. Stewartii.

    PubMed

    Chen, Yi ping; Zou, Ming qiang; Wang, Da ning; Li, Yong liang; Xue, Qiang; Xie, Meng xia; Qi, Cai

    2013-05-15

    A rapid, sensitive, and simple immunosensor has been developed for the detection of Pantoea stewartii subsp. Stewartii (Pss). This immunosensor combines magnetic relaxation switch (MRS) assay with polystyrene microparticle-induced immune multivalency enrichment system. Comparing to conventional enzyme-linked immunosorbent assay (ELISA), the immunosensor developed in this study provides higher sensitivity and requires less analysis time. The detection limit of Pss obtained by immunosensor was determined to be 10(3)cfu/mL, 50 times lower than that by ELISA (5×10(4)cfu/mL), while the analysis time required by immunosensor is 30min much shorter than that by ELISA. The average recoveries studied with Pss at various spiking levels ranged from 85.5% to 93.4% with a relative standard deviation (RSD) below 6.0%. No cross-reaction with the other five strains was found, demonstrating a good specificity of Pss detection. The results showed that the MRS immunosensor combined with PS-induced immune multivalency enhancement system is a promising platform for the determination of large biological molecules due to its high sensitivity, specificity, homogeneity, and speed. PMID:23274190

  20. Love Wave Immunosensor for the Detection of Carbaryl Pesticide

    PubMed Central

    Rocha-Gaso, María-Isabel; García, José-Vicente; García, Pablo; March-Iborra, Carmen; Jiménez, Yolanda; Francis, Laurent-Alain; Montoya, Ángel; Arnau, Antonio

    2014-01-01

    A Love Wave (LW) immunosensor was developed for the detection of carbaryl pesticide. The experimental setup consisted on: a compact electronic characterization circuit based on phase and amplitude detection at constant frequency; an automated flow injection system; a thermal control unit; a custom-made flow-through cell; and Quartz/SiO2 LW sensors with a 40 μm wavelength and 120 MHz center frequency. The carbaryl detection was based on a competitive immunoassay format using LIB-CNH45 monoclonal antibody (MAb). Bovine Serum Albumin-CNH (BSA-CNH) carbaryl hapten-conjugate was covalently immobilized, via mercaptohexadecanoic acid self-assembled monolayer (SAM), onto the gold sensing area of the LW sensors. This immobilization allowed the reusability of the sensor for at least 70 assays without significant signal losses. The LW immunosensor showed a limit of detection (LOD) of 0.09 μg/L, a sensitivity of 0.31 μg/L and a linear working range of 0.14–1.63 μg/L. In comparison to other carbaryl immunosensors, the LW immunosensor achieved a high sensitivity and a low LOD. These features turn the LW immunosensor into a promising tool for applications that demand a high resolution, such as for the detection of pesticides in drinking water at European regulatory levels. PMID:25192313

  1. Ultrasensitive sandwich-type electrochemical immunosensor based on a novel signal amplification strategy using highly loaded toluidine blue/gold nanoparticles decorated KIT-6/carboxymethyl chitosan/ionic liquids as signal labels.

    PubMed

    Wang, Yulan; Li, Xiaojian; Cao, Wei; Li, Yueyun; Li, He; Du, Bin; Wei, Qin

    2014-11-15

    An ultrasensitive sandwich-type electrochemical immunosensor for the quantitative detection of carcinoembryonic antigen (CEA) was designed based on a novel signal amplification strategy. Gold nanoparticles decorated mesoporous silica KIT-6 (Au@KIT-6) with large specific surface area and good adsorption properties was used as a label matrix to immobilize both the secondary antibodies (Ab2) and the electron transfer mediator toluidine blue (TB). Ab2 was loaded on KIT-6 due to the presence of gold nanoparticles (Au NPs) and TB was loaded on KIT-6 by physical adsorption. Ionic liquids (ILs) doped carboxymethyl chitosan (CMC) was used to prevent the leak of TB and facilitate the electron transfer. For the immobilization of primary antibodies (Ab1), gold nanoparticles decorated 3-aminopropyltriethoxysilane functionalized graphene sheets (Au@APTES-GS) were used as transducing materials to modify glassy carbon electrodes (GCE). High sensitivity was achieved for the designed immunosensor based on this novel signal amplification strategy. Under optimal conditions, the immunosensor exhibited an extremely low detection limit of 3.3 fg/mL and wide liner range from 10(-5) ng/mL to 10(2) ng/mL for CEA. Moreover, it exhibited good selectivity, acceptable reproducibility and stability, indicating potential application promising in clinical monitoring of tumor biomarkers. PMID:24967751

  2. A novel antibody-antigen based impedimetric immunosensor for low level detection of HER2 in serum samples of breast cancer patients via modification of a gold nanoparticles decorated multiwall carbon nanotube-ionic liquid electrode.

    PubMed

    Arkan, Elham; Saber, Reza; Karimi, Ziba; Shamsipur, Mojtaba

    2015-05-18

    A highly sensitive impedimetric immunosensor based on a gold nanoparticles/multiwall carbon nanotube-ionic liquid electrode (AuNPs/MW-CILE) was developed for the determination of human epidermal growth factor receptor 2 (HER2). Gold nanoparticles were used to enhance the extent of immobilization and to retain the immunoactivity of the antibody Herceptin on the electrode. Cyclic voltammetry and electrochemical impedance spectroscopy were employed for characterization of various layers coated onto the AuNPs/MW-CILE. The impedance measurements at different steps were based on the charge transfer kinetics of the [Fe(CN)6](3-/4-) redox pair. The immobilization of antibody and the corresponding antigen-antibody interaction at the electrode surface altered the interfacial electron transfer. The interactions of antibody with various concentrations of antigen were also monitored via the change of impedance response. The results showed that the charge transfer resistance increases linearly with increasing concentrations of HER2 antigen. The linear range and limit of detection were found as 10-110 ng mL(-1) and 7.4 ng mL(-1), respectively. The sensitivity and specificity of the immunosensor were validated. The results showed that the prepared immunosensor is a useful tool for screening of trace amounts of HER2 in serum samples of breast cancer patients. PMID:25910448

  3. An amplified electrochemical immunosensor based on in situ-produced 1-naphthol as electroactive substance and graphene oxide and Pt nanoparticles functionalized CeO2 nanocomposites as signal enhancer.

    PubMed

    Yang, Zhe-Han; Zhuo, Ying; Yuan, Ruo; Chai, Ya-Qin

    2015-07-15

    In this work, an amplified electrochemical immunosensor based on 1-naphthol as electroactive substance and Pt/CeO2/GO composites as catalytic amplifier was constructed for sensitive detection influenza. Through "sandwich" reaction, the Pt/CeO2/GO functionalized bioconjugates were captured on electrode surface and the electrochemical signal directly originated from 1-naphthol, which was in situ produced with high local concentration though the hydrolysis of 1-naphthyl phosphate catalyzed by ALP. Then, 1-naphthol as new reactant was oxidized by Pt/CeO2/GO composites with outstanding catalytic performance, resulting in detection signal amplification. In addition, as compared to label electroactive substance to antibodies, a simplified preparative step of immunosensor could be achieved because the signal probe get rid of introducation other electroactive substances. The proposed immunosensor achieved a linear range of 1.0×10(-3)-1.0ngmL(-1) and 5.0 to 1.0×10(2)ngmL(-1) with a detection limit of 0.43pgmL(-1) (defined as S/N=3). PMID:25791337

  4. Paper-based colorimetric immunosensor for visual detection of carcinoembryonic antigen based on the high peroxidase-like catalytic performance of ZnFe2O4-multiwalled carbon nanotubes.

    PubMed

    Liu, Weiyan; Yang, Hongmei; Ding, Yanan; Ge, Shenguang; Yu, Jinghua; Yan, Mei; Song, Xianrang

    2014-01-01

    A new paper-based colorimetric immunosensor for the detection of carcinoembryonic antigen (CEA) was developed based on the intrinsic peroxidase activity of ZnFe2O4-multiwalled carbon nanotubes (ZnFe2O4@MWNTs). The immunosensor platform was prepared by depositing chitosan and porous gold onto filter paper and entrapping the primary antibodies (Ab1) onto the layers. Secondary antibodies (Ab2) were assembled on the surface of the functionalized ZnFe2O4@MWNTs. The immunosensor response was quantified as a color change resulting from ZnFe2O4@MWNTs catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of H2O2. The catalytic performance of ZnFe2O4@MWNTs was higher than ZnFe2O4 due to the high electrical conductance of MWNTs, moreover, the electron communications between ZnFe2O4@MWNTs and substrates are electrically "wired". Detection was achieved by measuring the color change when the concentrations of CEA were different. The color change can be quantified with the naked eye but a digitalized picture can also be used to provide more sensitive comparison to a calibrated color scheme. This method was simple for CEA detection with a linear range from 0.005 to 30 ng mL(-1) and a detection limit of 2.6 pg mL(-1). Such an equipment-free immunoassay has great potential in resource-limited environments. PMID:24205509

  5. A novel glutathione-S transferase immunosensor based on horseradish peroxidase and double-layer gold nanoparticles.

    PubMed

    Lu, Dingqiang; Lu, Fuping; Pang, Guangchang

    2016-06-01

    GSTs, a biotransformation enzyme group, can perform metabolism, drug transfer and detoxification functions. Rapid detection of the GSTs with more sensitive approaches is of great importance. In the current study, a novel double-layer gold nanoparticles-electrochemical immunosensor electrode (DGN-EIE) immobilized with Glutathione S-Transferase (GST) antibody derived from Balb/c mice was developed. To increase the fixed quantity of antibodies and electrochemical signal, an electrochemical biosensing signal amplification system was utilized with gold nanoparticles-thionine-chitosan absorbing horseradish peroxidase (HRP). In addition, transmission electron microscope (TEM) was used to characterize the nanogold solution. To evaluate the quality of DGN-EIE, the amperometric I-t curve method was applied to determine the GST in PBS. The results showed that the response current had a good linear correlation with the GST concentration ranged from 0.1-10(4) pg/mL. The lowest detection limit was found at 0.03 pg/mL(S/N = 3). The linear equation was deduced as △I/% = 7.386lgC + 22.36 (R(2) = 0.998). Moreover, it was validated with high sensitivity and reproducibility. Apparently, DGN-EIE may be a very useful tool for monitoring the GST. PMID:27220630

  6. Electrogenerated chemiluminescence immunosensor for Bacillus thuringiensis Cry1Ac based on Fe3O4@Au nanoparticles.

    PubMed

    Li, Jianping; Xu, Qian; Wei, Xiaoping; Hao, Zaibin

    2013-02-20

    A highly sensitive electrochemiluminescence (ECL) immunosensor for Cry1Ac was fabricated. The primary antibody anti-Cry1Ac was immobilized onto core-shell structural Fe(3)O(4)@Au nanoparticles. The antigen and glucose-oxidase-labeled secondary antibody were then successively combined to form sandwich-type immunocomplexes through a specific interaction. The magnetic particles loaded with sandwich immune complexes were attracted to a magnet-controlled glass carbon electrode (GCE) by an external magnet applied on top of the GCE. ECL was generated by the reaction between luminol and hydrogen peroxide derived from the enzymatic reaction in the presence of glucose. The sensors exhibited high sensitivity and a wide linear range for Bacillus thuringiensis Cry1Ac detection from 0 to 6 ng/mL, as well as a detection limit of 0.25 pg/mL (S/N = 3). The sensor is one of the most sensitive sensors for Cry1Ac, which can be easily renewed and conveniently used. PMID:23317307

  7. Graphene oxide based electrochemical label free immunosensor for rapid and highly sensitive determination of tumor marker HSP70.

    PubMed

    Özcan, Burcu; Sezgintürk, Mustafa Kemal

    2016-11-01

    In this study, it is aimed to design a label free immunosensor for determination of HSP70 (heat shock protein 70). Glassy carbon electrode was used as a working electrode. Graphene oxide was covered on the working electrode surface. AntiHSP70 as a biorecognition element of the biosensor was covalently immobilized onto the graphene oxide layer by using EDC/NHS chemistry. The immobilization of antiHSP70 and binding of HSP70 protein onto the electrode surface were monitored by cyclic voltammetry and electrochemical impedance spectroscopy. Single frequency technique was also utilized to monitor binding characterization of HSP70 and antiHSP70. Surface morphology was defined by using scanning electron microscopy. All important fabrication steps of the biosensor were optimized to prepare an ultrasensitive biosensor. Under optimum conditions, analytical studies such as linearity, repeatability, and reproducibility were also experienced. A linear detection range of HSP70 was determined between 12 and 144fg/mL. Moreover, Kramer's Kronig transform was applied on impedance data. Finally, the biosensor was applied with real human blood serum samples and hopeful results were obtained. PMID:27591626

  8. Photocatalytic silver enhancement reaction for gravimetric immunosensors

    NASA Astrophysics Data System (ADS)

    Seo, Hyejung; Joo, Jinmyoung; Ko, Wooree; Jung, Namchul; Jeon, Sangmin

    2010-12-01

    A novel microgravimetric immunosensor has been developed using TiO2 nanoparticle-modified immunoassay and silver enhancement reaction. An antibody-conjugated TiO2 nanoparticle is bound to the AFP antigen immobilized on a quartz resonator. When the nanoparticles are exposed to UV light in a silver nitrate solution, the photocatalytic reduction of silver ions results in the formation of metallic silver onto the nanoparticles and induces a decrease in the resonance frequency. The frequency change by this photocatalytic reduction reaction is three orders of magnitude larger than the change by antigen binding alone. The efficiency of the photocatalytic reaction has been found to increase with the fraction of anatase crystallites in the nanoparticles and the concentration of the AgNO3 solution. The results highlight the potential of the photocatalytic nanoparticles for the detection of low concentrations of target molecules using gravimetric sensors.

  9. An impedance immunosensor based on low-cost microelectrodes and specific monoclonal antibodies for rapid detection of avian influenza virus H5N1 in chicken swabs.

    PubMed

    Lin, Jianhan; Wang, Ronghui; Jiao, Peirong; Li, Yuntao; Li, Yanbin; Liao, Min; Yu, Yude; Wang, Maohua

    2015-05-15

    Early screening of suspected cases is the key to control the spread of avian influenza (AI) H5N1. In our previous studies, an impedance biosensor with an interdigitated array microelectrode based biochip was developed and validated with pure AI H5 virus, but had limitations in cost and reliability of the biochip, specificity of the antibody against Asian in-field H5N1 virus and detection of H5N1 virus in real samples. The purpose of this study is to develop a low-cost impedance immunosensor for rapid detection of Asian in-field AI H5N1 virus in chicken swabs within 1h and validate it with the H5N1 virus. Specific monoclonal antibodies against AI H5N1 virus were developed by fusion of mouse myeloma cells with spleen cells isolated from an H5N1-virus-immunized mouse. Dot-ELISA analysis demonstrated that the developed antibodies had good affinity and specificity with the H5N1 virus. The microelectrodes were redesigned with compact size, fabricated using an improved wet-etching micro-fabrication process with a higher qualified production rate of 70-80%, and modified with the antibodies by the Protein A method. Equivalent circuit analysis indicated that electron transfer resistor was effective with the increase in impedance after capturing of the H5N1 viruses. Linear relationship between impedance change and logarithmic value of H5N1 virus at the concentrations from 2(-1) to 2(4) HAU/50 μl was found and the lower limit of detection was 2(-1) HAU/50 μl. No obvious interferences from non-target viruses such as H6N2, H9N2, Newcastle disease virus, and infectious bronchitis virus were found. Chicken swab tests showed that the impedance immunosensor had a comparable accuracy with real-time RT-PCR compared to viral isolation. PMID:25263315

  10. Electrochemical immunosensors for environmental monitoring

    SciTech Connect

    Sadik, O.A.; Van Emon, J.M.

    1995-12-31

    The time involved in field sampling and laboratory analysis of environmental samples has stimulated the development of alternative rapid and cost-effective field screening and monitoring methods for a wide range of toxic chemicals. Current research in our laboratories is directed toward developing portable, continuous and in-situ electrochemical immunosensors for detection of compounds such as polychlorinated biphenyls (PCBs), heavy metals and pesticides. Previous work has shown that the use of these sensors possesses significant advantages over conventional methods in the detection and quantitation of a range of analytes. The advantages of conducting electroactive polymers (CEPs) in combining the function of an antibody-entrapment matrix and the transducer required for the measurement of immunological reactions translate into substantial equipment miniaturization as well as reduction in response time. This promises to open up new horizons in environmental monitoring, medical and clinical applications. This paper will discuss the detection and quantitation of environmental samples using CEP-based sensors. Recent advances in biosensing technologies using electrochemical immunoassays will also be discussed. CEP-based immunosensing systems will be compared with conventional environmental immunoassay procedures. The advantages of utilizing these types of sensors in providing rapid, sensitive and cost-effective options for environmental analysis of pesticides and other potential contaminants will be analyzed and discussed.

  11. Fiber Optic Surface Plasmon Resonance-Based Biosensor Technique: Fabrication, Advancement, and Application.

    PubMed

    Liang, Gaoling; Luo, Zewei; Liu, Kunping; Wang, Yimin; Dai, Jianxiong; Duan, Yixiang

    2016-05-01

    Fiber optic-based biosensors with surface plasmon resonance (SPR) technology are advanced label-free optical biosensing methods. They have brought tremendous progress in the sensing of various chemical and biological species. This review summarizes four sensing configurations (prism, grating, waveguide, and fiber optic) with two ways, attenuated total reflection (ATR) and diffraction, to excite the surface plasmons. Meanwhile, the designs of different probes (U-bent, tapered, and other probes) are also described. Finally, four major types of biosensors, immunosensor, DNA biosensor, enzyme biosensor, and living cell biosensor, are discussed in detail for their sensing principles and applications. Future prospects of fiber optic-based SPR sensor technology are discussed. PMID:27119268

  12. Self-enhanced N-(aminobutyl)-N-(ethylisoluminol) derivative-based electrochemiluminescence immunosensor for sensitive laminin detection using PdIr cubes as a mimic peroxidase

    NASA Astrophysics Data System (ADS)

    Jiang, Xinya; Wang, Huijun; Wang, Haijun; Zhuo, Ying; Yuan, Ruo; Chai, Yaqin

    2016-04-01

    Herein, a self-enhanced N-(aminobutyl)-N-(ethylisoluminol) (ABEI) derivative-based electrochemiluminescence (ECL) immunosensor was constructed for the determination of laminin (LN) using PdIr cubes as a mimic peroxidase for signal amplification. Initially, PdIr cubes with efficient peroxidase mimicking properties, large specific surface areas, and good stability and uniformity were synthesized. Then, l-cysteine (l-Cys) and ABEI were immobilized on the PdIr cubes to form the self-enhanced ECL nanocomplex (PdIr-l-Cys-ABEI). In this nanocomplex, PdIr cubes, whose catalytic constant is higher than that of horseradish peroxidase (HRP), could effectively catalyze H2O2 decomposition and thus enhance the ECL intensity of ABEI. Moreover, PdIr cubes can be easily modified with functional groups, which make them adaptable to desired supported platforms. On the other hand, l-Cys as a coreactant of ABEI could effectively enhance the luminous efficiency due to the intramolecular ECL reaction which could reduce the energy loss between l-Cys and ABEI by giving a shorter electron transfer distance. The developed strategy combined an ABEI derivative as a self-enhanced ECL luminophore and PdIr cubes as a mimic peroxidase, resulting in a significantly enhanced ECL signal output. Also, the strategy showed high sensitivity and selectivity for LN, which suggested that our new approach could be potentially applied in monitoring different proteins.

  13. DIRECT ELECTROCHEMICAL IMMUNOSENSOR FOR POLYCHLORINATED BIPHENYLS. (R825323)

    EPA Science Inventory

    A direct electrochemical immunosensor has been developed for the determination of polychlorinated biphenyls (PCBs) in water. The assay is based on the measurement of the current due to the specific binding between PCB and anti-PCB antibody-immobilized conducting polymer matrix. T...

  14. Amperometric immunosensor for α-fetoprotein antigen in human serum based on co-immobilizing dinuclear copper complex and gold nanoparticle doped chitosan film

    NASA Astrophysics Data System (ADS)

    Gan, Ning; Meng, Ling Hua; Wang, Feng

    2009-09-01

    A sensitive amperometric immunosensor for α-fetoprotein (AFP), a tumor marker for the diagnosis of hepatocellular carcinoma (HCC), was constructed, The immunosensor is prepared by co-immobilizing [Cu2(phen)2Cl2] (μ-Cl)2 (CuL), nano-Au/Chitosan(Chit) composite, horseradish peroxidase (HRP) and AFP antibody(anti-AFP) on a glassy carbon electrode (GCE). Firstly, CuL was irreversibly absorb on GCE electrode through π-π stacking interaction; then nano-Au/Chit composite was immobilized onto the electrode because of its excellent membrane-forming ability, finally HRP and anti-AFP was adsorbed onto the surface of the gold nanoparticles to construct GCE | CuL/nanoAu-chit/HRP/anti-AFP immunosensor. The preparation procedure of the electrode was characterized by electrochemical and spectroscopy method. The results showed that this immunosensor exhibited an excellent electrocatalytic response to the reduction of hydrogen peroxide (H2O2) without the aid of an electron mediator, offers a high-sensitivity (1710 nA · ng-1 · ml-1) for the detection of AFP and has good correlation for detection of AFP in the range of 0.2 to 120.0 ng/ml with a detection limit of 0.05 ng/ml. The biosensor showed high selectivity as well as good stability and reproductivity.

  15. Label-Free Electrochemiluminescent Immunosensor for Detection of Carcinoembryonic Antigen Based on Nanocomposites of GO/MWCNTs-COOH/Au@CeO₂.

    PubMed

    Pang, Xuehui; Li, Jianxiu; Zhao, Yongbei; Wu, Dan; Zhang, Yong; Du, Bin; Ma, Hongmin; Wei, Qin

    2015-09-01

    A high-sensitivity electrochemiluminescence (ECL) sensor was conducted to detect carcinoembryonic antigen (CEA). Nanocomposites of graphene oxide/carboxylated multiwall carbon nanotubes/gold/cerium oxide nanoparticles (GO/MWCNTs-COOH/Au@CeO2) were used as antibody carriers and sensing platforms to modify on glassy carbon electrodes (GCE). CeO2 nanoparticles were first exploited as an ECL luminescent material and the possible ECL mechanism was proposed in this work. GO/MWCNTs-COOH was used as a loading matrix for CeO2 nanoparticles because of the superior conductivity and large specific surface area. Au nanoparticles were further deposited on this matrix to attach anti-CEA and enhance the sensitivity of immunosensor. The proposed sensing platform showed excellent cathodic ECL performance and sensitive response to CEA. The effects of experimental conditions on the ECL performance were investigated. The proposed immunosensor showed the broad linear range (0.05-100 ng/mL) and the low detection limit (LOD, 0.02 ng/mL, signal-to-noise ratio = 3) according to the selected experimental conditions. The excellent analysis performance for determination of CEA in the human serum samples simplied this immunosensor displayed high sensitivity and excellent repeatability. More importantly, this conducted immunosensor broadens the use scope of CeO2 nanoparticles. PMID:26271682

  16. A sensitive amperometric immunosensor for alpha-fetoprotein based on carbon nanotube/DNA/Thi/nano-Au modified glassy carbon electrode.

    PubMed

    Ran, Xiao-Qi; Yuan, Ruo; Chai, Ya-Qin; Hong, Cheng-Lin; Qian, Xiao-Qing

    2010-09-01

    A novel amperometric immunosensor for the determination of alpha-fetoprotein (AFP) was constructed using films of multi-wall carbon nanotubes/DNA/thionine/gold nanoparticles (nano-Au). Firstly, multiwall carbon nanotubes (MWCNT) dispersed in poly(diallydimethlammonium chloride) (PDDA) were immobilized on the nano-Au film which was electrochemically deposited on the surface of glassy carbon electrode. Then a negatively charged DNA film was absorbed on the positively charged PDDA. Subsequently, thionine was attached to the electrode via the electrostatic interaction between thionine and the DNA. Finally, the nano-Au was retained on the thionine film for immobilization of AFP antibody (anti-AFP). The modification process was characterized by cyclic voltammetry (CV) and scanning electron microscope (SEM). The factors possibly influenced the performance of the proposed immunosensors were studied in detail. Under optimal conditions, the proposed immunosensor exhibited good electrochemical behavior to AFP in a two concentration ranges: 0.01-10.0 and 10.0-200.0 ng/mL with a relatively low detection limit of 0.04 ng/mL at three times the background noise. Moreover, the selectivity, repeatability and stability of the proposed immunosensor were acceptable. PMID:20627666

  17. Nanoelectrochemical Immunosensors for Protein Detection

    NASA Astrophysics Data System (ADS)

    Carpentiero, Alessandro; de Leo, Manuela; Garcia Romero, Ivan; Pozzi Mucelli, Stefano; Reuther, Freimut; Stanta, Giorgio; Tormen, Massimo; Ugo, Paolo; Zamuner, Martina

    Nanoelectrochemical immunosensors fabricated by templated electrodeposition of gold nanoelectrodes inside the pores of polycarbonate (PC) track-etched membranes, followed by the immobilization of the biorecognition elements on the surrounding PC, have proven high sensitivity and specificity for protein detection. The signal transduction scheme involves a suitable redox mediator added to the sample solution to shuttle electrons from the gold nanoelectrodes to the biorecognition layer, both elements being in strict spatial proximity. Highly improved signal-to-background current ratio, which are peculiar of NEEs with respect to other electrochemical transducers, can be exploited in this way. Two detection schemes were tested: one based on the direct immobilization of the target protein on the PC of the NEE (approach A) and the other based on the immobilisation on PC of an antibody to capture the target protein (approach B). The biorecognition process was completed by adding a primary antibody and a secondary antibody with horse radish peroxidase (HRP) as enzyme label; methylene blue was the redox mediator added to the electrolyte solution. Typical target analytes were single chain fragment variable proteins, for approach A, and trastuzumab (also known as Herceptin®), for approach B. NEE-based capture sensors were tested successfully to detect small amounts of the receptor protein HER2 in biological samples. Finally, motivated by the target of a better control of the geometrical characteristics of ensembles of nanoelectrodes (size, density, geometrical arrangement, and degree of recession), and by the positive results obtained with track-etch membranes of PC from the standpoint of protein immobilization, we demonstrated the fabrication of nanobiosensors by patterning ordered arrays of nanoelectrodes (NEAs) by electron beam lithography (EBL) on polycarbonate. EBL results perfectly suitable for the top-down fabrication of arrays of nanobiosensors on thin PC films

  18. Conformation-sensitive antibody-based point-of-care immunosensor for serum Ca(2+) using two-dimensional sequential binding reactions.

    PubMed

    Park, Ji-Na; Paek, Sung-Ho; Kim, Dong-Hyung; Seo, Sung-Min; Lim, Guei-Sam; Kang, Ju-Hee; Paek, Sung-Pil; Cho, Il-Hoon; Paek, Se-Hwan

    2016-11-15

    To assess the homeostasis of Ca(2+) metabolism, we have developed a rapid immunosensor for ionic calcium using a membrane chromatographic technique. As calcium-binding protein (CBP) is available for the recognition and undergone conformation change upon Ca(2+) binding, a monoclonal antibody sensitive to the altered structure of CBP has been employed. The sequential binding scheme was mathematically simulated and shown to match with the experimental results. At the initial stage, the rapid analytical system using lateral flow was constructed by immobilizing the antibody on the immuno-strip nitrocellulose membrane and labeling CBP with colloidal gold as a tracer. A major problem with this system in measuring ionic calcium levels was retarded migration of the gold tracer along the immuno-strip. It was conceivable that the divalent cation at a high concentration caused a change in the physical properties of the tracer, resulting in a non-specific interaction with the membrane surface. This problem was circumvented by first eluting a sample containing biotinylated CBP along the immuno-strip and then supplying the gold coupled to streptavidin across the signal generation pad of the strip. The color signal was then generated via biotin-SA linkage and measured using a smartphone-based detector developed in our laboratory. This two-dimensional chromatographic format completed the Ca(2+) analysis within 15min, the analytical performance covered the clinical dynamic range (0.25-2.5mM) and highly correlated with that of the reference system, i-STAT. These results inspired us to eventually investigate a dual-immunoassay system that measures simultaneously ionic calcium and parathyroid hormone, which regulates the ionic calcium level in serum. This will significantly simplify the current diagnostic protocols, which involve separate devices. PMID:27236727

  19. A novel electrochemiluminescent immunosensor based on CdS-coated ZnO nanorod arrays for HepG2 cell detection

    NASA Astrophysics Data System (ADS)

    Liu, Danqing; Wang, Lei; Ma, Shenghua; Jiang, Zhaohua; Yang, Bin; Han, Xiaojun; Liu, Shaoqin

    2015-02-01

    In this work, the highly oriented CdS-coated-ZnO nanorod arrays have been fabricated. The CdS-coated-ZnO nanorod arrays show high electrochemiluminescence intensity, fast response and good stability. All of the desirable properties spur the development of an ECL immunosensor for the detection of the liver cancer cell line (HepG2 cells). Two successive modification steps of 3-aminopropyltriethoxysilane and gold nanoparticles onto the CdS-coated-ZnO nanorod arrays not only offer the substrates for conjugation of antibody, but also effectively enhance the ECL signal, resulting in production of the high performance ECL immunosensor. The ECL immunosensor exhibits a sensitive response to HepG2 cells in a linear range of 300-10 000 cells mL-1 with a detection limit of 256 cells mL-1. The proposed sensor characteristics of high specificity, good reproducibility and remarkable stability will provide a sensitive, selective, and convenient approach for the clinical detection of cancer cells.In this work, the highly oriented CdS-coated-ZnO nanorod arrays have been fabricated. The CdS-coated-ZnO nanorod arrays show high electrochemiluminescence intensity, fast response and good stability. All of the desirable properties spur the development of an ECL immunosensor for the detection of the liver cancer cell line (HepG2 cells). Two successive modification steps of 3-aminopropyltriethoxysilane and gold nanoparticles onto the CdS-coated-ZnO nanorod arrays not only offer the substrates for conjugation of antibody, but also effectively enhance the ECL signal, resulting in production of the high performance ECL immunosensor. The ECL immunosensor exhibits a sensitive response to HepG2 cells in a linear range of 300-10 000 cells mL-1 with a detection limit of 256 cells mL-1. The proposed sensor characteristics of high specificity, good reproducibility and remarkable stability will provide a sensitive, selective, and convenient approach for the clinical detection of cancer cells

  20. A double signal electrochemical human immunoglobulin G immunosensor based on gold nanoparticles-polydopamine functionalized reduced graphene oxide as a sensor platform and AgNPs/carbon nanocomposite as signal probe and catalytic substrate.

    PubMed

    Zhang, Si; Huang, Na; Lu, Qiujun; Liu, Meiling; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

    2016-03-15

    In this paper, a double signal electrochemical Human immunoglobulin G (HIgG) immunosensor based on AgNPs/carbon nanocomposite (Ag/C NC) as the signal probe and catalytic substrate was developed for fast and sensitive detection of HIgG. The as-prepared AuNPs-PDA-rGO nanocomposite and Ag/C NC were confirmed by UV-vis, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. Electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical properties of the proposed immunosensor. The AuNPs-PDA-rGO nanocomposite can improve the electron transfer rate and capture more Ab1. In the sandwich-type immunoassay process, the Ag/C NC functionalized bioconjugates were captured on HIgG/Ab1/AuNPs-PDA-rGO surface and the electrochemical double-signal strategy was employed. These double electrochemical detection signals were directly monitored the oxidation current originated from Ag/C NC and indirectly detected the reduction current of benzoquinone which was produced from the reaction of H2O2 and HQ by catalysis of Ag/C NC in electrochemical detection of HIgG. Under the optimized conditions, the current responses were changed with the concentrations of HIgG for the proposed immunosensor with wide linear ranges of 0.1 to 100 ngmL(-1) and 0.01-100 ngmL(-1) with the lowest detection concentration of 0.001 ng mL(-1) in the absence and presence of H2O2 and HQ. The double-signal strategy is used for detection of HIgG, and the results came from the two signals were well consistent with each other. The proposed immunosensor was successfully applied in analysis of human IgG in real samples and this strategy may provide a relative simple and effective method for construction of other immunsensors in detection of other biomarkers in clinical medicine. PMID:26556185

  1. Electrochemical impedance immunosensor for sub-picogram level detection of bovine interferon gamma based on cylinder-shaped TiO₂ nanorods.

    PubMed

    Yang, Zhanjun; Jian, Zhiqin; Chen, Xiang; Li, Juan; Qin, Piya; Zhao, Jie; Jiao, Xin'an; Hu, Xiaoya

    2015-01-15

    Bovine interferon gamma (BoIFN-γ) released by T cells plays very important roles in early diagnosis of Mycobacterium tuberculosis (MTB) infections and control of bovine tuberculosis. In this work, a label-free electrochemical impedance immunosensor is for the first time developed for highly sensitive determination of BoIFN-γ. Cylinder-shaped TiO2 nanorods are synthesized by a facile hydrothermal method, and show high surface area and good hydrophicility. The immunosensor is fabricated by the immobilization of BoIFN-γ monoclonal antibody on the TiO2 nanorods modified glassy carbon electrode. The prepared TiO2 and immunosensor are characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, contact angle measurement, cyclic voltammetry, and electrochemical impedance spectra. The BoIFN-γ concentration is measured through the relative increase of impedance values in corresponding specific binding of BoIFN-γ antigen and BoIFN-γ antibody. The relative increased impedance values are proportional to the logarithmic value of BoIFN-γ concentrations in a wide range of 0.0001 to 0.1 ng/mL with a low detection limit of 0.1 pg/mL. The developed BoIFN-γ immunosensor shows a 249-fold decrease in detection limit in comparison with current enzyme-linked immunosorbent assay. This study provides a new, simple, and highly sensitive approach for very potential application in early diagnosis of MTB infections and control of bovine tuberculosis. PMID:25089816

  2. 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. PMID:26232003

  3. Sensitive Electrochemical Immunosensor for Detection of Nuclear Matrix Protein-22 based on NH2-SAPO-34 Supported Pd/Co Nanoparticles.

    PubMed

    Wu, Dan; Wang, Yaoguang; Zhang, Yong; Ma, Hongmin; Yan, Tao; Du, Bin; Wei, Qin

    2016-01-01

    A novel sandwich-type electrochemical immunosensor using the new amino group functionalized silicoaluminophosphates molecular sieves (NH2-SAPO-34) supported Pd/Co nanoparticles (NH2-SAPO-34-Pd/Co NPs) as labels for the detection of bladder cancer biomarker nuclear matrix protein-22 (NMP-22) was developed in this work. The reduced graphene oxide-NH (rGO-NH) with good conductivity and large surface area was used to immobilize primary antibody (Ab1). Due to the excellent catalytic activity toward hydrogen peroxide, NH2-SAPO-34-Pd/Co NPs were used as labels and immobilized secondary antibody (Ab2) through adsorption capacity of Pd/Co NPs to protein. The immunosensor displayed a wide linear range (0.001-20 ng/mL) and low detection limit (0.33 pg/mL). Good reproducibility and stability have showed satisfying results in the analysis of clinical urine samples. This novel and ultrasensitive immunosensor may have the potential application in the detection of different tumor markers. PMID:27086763

  4. An electrochemiluminescence immunosensor for thyroid stimulating hormone based on polyamidoamine-norfloxacin functionalized Pd-Au core-shell hexoctahedrons as signal enhancers.

    PubMed

    Liu, Yuting; Zhang, Qiqi; Wang, Haijun; Yuan, Yali; Chai, Yaqin; Yuan, Ruo

    2015-09-15

    In this work, a novel polyamidoamine-norfloxacin (PAMAM-NFLX) complex and core-shell Pd-Au hexoctahedrons (Pd@Au HOHs) as enhancers are employed for development of a sensitive sandwich-type electrochemiluminescence (ECL) immunosensor to detect thyroid stimulating hormone (TSH). Here, norfloxacin (NFLX) is decorated abundantly on the surface of polyamidoamine (PAMAM) dendrimer via amide linkage to form PAMAM-NFLX complex. Thus, the resultant PAMAM-NFLX can serve as a novel co-reactant to efficiently amplify the ECL signal of peroxydisulfate-oxygen (S2O8(2-)-O2) system. Pd@Au HOHs were used as nano-carriers to assemble detection antibody (Ab2) and the PAMAM-NFLX complex. Besides, it can further enhance the ECL signal by promoting the generation of intermediate free radical HO(•) during the ECL reaction of S2O8(2-)-O2 system. The proposed immunosensor shows high sensitivity and specificity, and responds linearly to the concentration of TSH from 0.05 to 20 μIU mL(-1) with a low detection limit of 0.02 μIU mL(-1) (S/N=3). Moreover, the immunosensor successfully achieves the detection of TSH in practical human blood serum with desirable results. PMID:25897886

  5. Spherical vs. granular immobilization support selection and performance on an optical flow cell immunosensor based on the fluorescence of Cyanine-5.

    PubMed

    Silvestre, Oscar F; Silva, Marta G; Oliva, Abel G; Cruz, Helder J

    2006-01-01

    A spherical porous glass support Trisoperl (TRISO) with four pore diameters (ø 47.8; 55.9; 102.6, and 108.8 nm) was characterized and selected for application in an optical flow cell immunosensor, in comparison with controlled pore glass (CPG). The TRISO support was functionalized with aldehyde and isothiocyanate (-NCS) groups to attach bovine serum albumin and alkaline phosphatase (AP). The TRISO isothiocyanate pore diameter 47.8 nm (TRISO(-NCS) 47.8 nm) showed the better potential to be used in the immunosensor. It immobilized more protein (19.3 mg AP per g support) while presenting an optical performance comparable to the CPG. CPG(-NCS) and TRISO(-NCS) 47.8 nm were tested in the immunosensor model where the saturation of the Goat IgG immobilized in the supports with Monoclonal Anti-Goat IgG conjugated with Cyanine-5 was reached, followed by regeneration with the elution buffer modified PBS pH 2.0. The TRISO(-NCS) 47.8 nm presented lower fluorescence intensity at saturation (around 39 AU) than CPG(-NCS) (150 to 104 AU), but revealed a major advantage related to the uniform arrangement of the spherical particles in the flow cell, generating no significant fluorescence differences between gravity and flow package. PMID:16971304

  6. Ru(bpy)32+/nanoporous silver-based electrochemiluminescence immunosensor for alpha fetoprotein enhanced by gold nanoparticles decorated black carbon intercalated reduced graphene oxide

    PubMed Central

    Zhu, Wenjuan; Lv, Xiaohui; Wang, Qi; Ma, Hongmin; Wu, Dan; Yan, Tao; Hu, Lihua; Du, Bin; Wei, Qin

    2016-01-01

    A highly sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was proposed for the quantitative determination of alpha fetoprotein (AFP) using gold nanoparticles decorated black carbon intercalated reduced graphene oxide (Au-rGO@CB) as sensing platform and nanoporous silver (NPS) loaded Ru(bpy)32+ as labels. In this work, intercalation of CB inhibited the accumulation of rGO and Au-rGO@CB was firstly used to immobilize primary antibody (Ab1) in ECL system. NPS prepared by the dealloying of binary alloy has high pore volume and surface areas, which was used to load amount of secondary antibodies (Ab2) and Ru(bpy)32+, which could greatly enhance the ECL intensity. Under optimal conditions, the designed immunosensor exhibited wider linear range from 0.0001 to 30 ng/mL with a relative lower detection limit of 33 fg/mL for AFP detection. Overall, the designed immunosensor exhibited high sensitivity and selectivity, good repeatability and stability. This proposed method provided a potential application for clinical monitoring of AFP. PMID:26829062

  7. A sandwich-type electrochemical immunosensor for carcinoembryonic antigen based on signal amplification strategy of optimized ferrocene functionalized Fe₃O₄@SiO₂ as labels.

    PubMed

    Feng, Taotao; Qiao, Xiuwen; Wang, Haining; Sun, Zhao; Hong, Chenglin

    2016-05-15

    A sandwich-type electrochemical immunosensor was developed for sensitive detection of carcinoembryonic antigen (CEA) by using ferroferric oxide@silica-amino groups (Fe3O4@SiO2-NH2) as carriers and gold nanoparticles-graphene oxide (GO-AuNPs) as platform. The Fe3O4@SiO2-NH2 surface was used as linked reagents for co-immobilization of ferrocenecarboxylic acid (Fc-COOH) and secondary anti-CEA (Ab2) to prepare the signal probe, and it also could hasten the decomposition of hydrogen peroxide (H2O2) to amplify signals. Differential pulse voltammetry (DPV) was successfully used to quantify CEA. Under the optimized conditions, the designed immunosensor shows an excellent analytical performance wide dynamic response range of CEA concentration from 0.001 ng mL(-1) to 80 ng mL(-1) with a relatively low detection limit of 0.0002 ng mL(-1) (S/N=3), and high specificity and good reproducibility. The proposed immunosensor was successfully used to determine CEA in spiked human serum samples. PMID:26686923

  8. Electrochemiluminescence immunosensor for highly sensitive detection of 8-hydroxy-2'-deoxyguanosine based on carbon quantum dot coated Au/SiO2 core-shell nanoparticles.

    PubMed

    Zhang, Ting-Ting; Zhao, Hui-Min; Fan, Xin-Fei; Chen, Shuo; Quan, Xie

    2015-01-01

    An electrochemiluminescence (ECL) immunosensor using Pt electrode modified with carbon quantum dot (CQDs) coated Au/SiO2 core-shell nanoparticles was proposed for sensitive detection of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in this work. Rabbit anti-8-OHdG antibody was covalently bound to CQDs on the surface of Au/SiO2 core-shell nanoparticles. Through signal amplification of Au/SiO2 core-shell nanoparticles, 8-fold enhancement of the ECL signals was achieved. Under optimal conditions, a good linear range from 0.2 to 200 ng mL(-1) with a low detection limit of 0.085 ng mL(-1) (S/N=3) for 8-OHdG detection was obtained. Interfering substances tests showed that the corresponding ECL intensity (ΔECL) of 8-OHdG is 8-18 times higher than that of guanine, uric acid (UA) and ascorbic acid, demonstrating its good selectivity for 8-OHdG detection. The ECL immunosensor exhibits long-term stability with a relative standard deviation (RSD) of 8.5% even after 16 cycles of continuous potential scans. The result of analytical detection of 8-OHdG in real samples was satisfactory. The proposed ECL immunosensor shows good performance with high sensitivity, specificity, repeatability, stability and provided a powerful tool for 8-OHdG monitoring in clinical samples. PMID:25281118

  9. Electrochemical immunosensor for detecting typical bladder cancer biomarker based on reduced graphene oxide-tetraethylene pentamine and trimetallic AuPdPt nanoparticles.

    PubMed

    Ma, Hongmin; Zhang, Xiaoyue; Li, Xiaojian; Li, Rongxia; Du, Bin; Wei, Qin

    2015-10-01

    A highly sensitive electrochemical immunosensor for detection of typical bladder cancer biomarker-nuclear matrix protein 22 (NMP22) was developed by using reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) and trimetallic AuPdPt nanoparticles (NPs). rGO-TEPA was used as the ideal material for signal amplification and AuPdPt NPs immobilization due to its excellent conductivity and large surface area. An effective platform was constructed for antibodies anchoring by using AuPdPt NPs, which kept the antibodies' high stability and bioactivity. Moreover, AuPdPt NPs could accelerate the electron transfer and enhance the signal response, which assisted by the synergistic effect of the three different metals (Au, Pd and Pt). The proposed immunosensor showed satisfied performance such as simple fabrication, low detection limits (0.01 U/mL), wide linear range (from 0.040 to 20 U/mL), short analysis time (2 min), high stability and selectivity in the detection of NMP22. Furthermore, the proposed immunosensor was employed to test real urine samples with satisfactory results. PMID:26078131

  10. Electrochemical aptamer/antibody based sandwich immunosensor for the detection of EGFR, a cancer biomarker, using gold nanoparticles as a signaling probe.

    PubMed

    Ilkhani, Hoda; Sarparast, Morteza; Noori, Abolhassan; Zahra Bathaie, S; Mousavi, Mir F

    2015-12-15

    Detection of epidermal growth factor receptor (EGFR) in biological fluids is of paramount importance, since it has significant application in cancer diagnosis, drug development, and therapy monitoring. EGFR is a cancer biomarker, and its overexpression is associated with the development of some types of cancer. Herein, we report on the development of a sensitive and selective electrochemical aptamer/antibody (Apt/Ab) sandwich immunosensor for detection of EGFR. In this study, a biotinylated anti-human EGFR Apt was immobilized on streptavidin-coated magnetic beads (MB) and served as a capture probe. A polyclonal anti-human EGFR Ab was conjugated to citrate-coated gold nanoparticles (AuNPs) and used as a signaling probe. In the presence of EGFR, an Apt-EGFR-Ab sandwich was formed on the MB surface. The extent of the complexation was evaluated by differential pulse voltammetry of AuNPs after their dissolution in HCl. Under optimal conditions, the dynamic concentration range of the immunosensor for EGFR spanned from 1 to 40 ng/mL, with a low detection limit of 50 pg/mL, and RSD percent of less than 4.2%. The proposed approach takes advantage of sandwich assay for high specificity, MBs for fast separation, and electrochemical method for cost-effective and sensitive detection. In this proof-of-principle study, we demonstrate the potential clinical efficacy of the immunosensor for monitoring of chemotherapy effectiveness in breast cancer samples. PMID:26176209

  11. Sensitive Electrochemical Immunosensor for Detection of Nuclear Matrix Protein-22 based on NH2-SAPO-34 Supported Pd/Co Nanoparticles

    PubMed Central

    Wu, Dan; Wang, Yaoguang; Zhang, Yong; Ma, Hongmin; Yan, Tao; Du, Bin; Wei, Qin

    2016-01-01

    A novel sandwich-type electrochemical immunosensor using the new amino group functionalized silicoaluminophosphates molecular sieves (NH2-SAPO-34) supported Pd/Co nanoparticles (NH2-SAPO-34-Pd/Co NPs) as labels for the detection of bladder cancer biomarker nuclear matrix protein-22 (NMP-22) was developed in this work. The reduced graphene oxide-NH (rGO-NH) with good conductivity and large surface area was used to immobilize primary antibody (Ab1). Due to the excellent catalytic activity toward hydrogen peroxide, NH2-SAPO-34-Pd/Co NPs were used as labels and immobilized secondary antibody (Ab2) through adsorption capacity of Pd/Co NPs to protein. The immunosensor displayed a wide linear range (0.001–20 ng/mL) and low detection limit (0.33 pg/mL). Good reproducibility and stability have showed satisfying results in the analysis of clinical urine samples. This novel and ultrasensitive immunosensor may have the potential application in the detection of different tumor markers. PMID:27086763

  12. 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

  13. Droplet resonator based optofluidic microlasers

    NASA Astrophysics Data System (ADS)

    Kiraz, Alper; Jonáš, Alexandr; Aas, Mehdi; Karadag, Yasin; Brzobohatý, Oto; Ježek, Jan; Pilát, Zdeněk.; Zemánek, Pavel; Anand, Suman; McGloin, David

    2014-03-01

    We introduce tunable optofluidic microlasers based on active optical resonant cavities formed by optically stretched, dye-doped emulsion droplets confined in a dual-beam optical trap. To achieve tunable dye lasing, optically pumped droplets of oil dispersed in water are stretched by light in the dual-beam trap. Subsequently, resonant path lengths of whispering gallery modes (WGMs) propagating in the droplet are modified, leading to shifts in the microlaser emission wavelengths. We also report lasing in airborne, Rhodamine B-doped glycerolwater droplets which were localized using optical tweezers. While being trapped near the focal point of an infrared laser, the droplets were pumped with a Q-switched green laser. Furthermore, biological lasing in droplets supported by a superhydrophobic surface is demonstrated using a solution of Venus variant of the yellow fluorescent protein or E. Coli bacterial cells expressing stably the Venus protein. Our results may lead to new ways of probing airborne particles, exploiting the high sensitivity of stimulated emission to small perturbations in the droplet laser cavity and the gain medium.

  14. Development of a Coulombimetric immunosensor based on specific antibodies labeled with CdS nanoparticles for sulfonamide antibiotic residues analysis and its application to honey samples.

    PubMed

    Valera, Enrique; Muriano, Alejandro; Pividori, Isabel; Sánchez-Baeza, Francisco; Marco, M-P

    2013-05-15

    A new electrochemical immunosensor has been developed to detect sulfonamide antibiotic residues in food samples. The immunosensor presented uses immunoreagents specifically developed for the broad recognition of the sulfonamide antibiotic family, a graphite composite electrode (GEC), biofunctionalized magnetic μ-particles and electrochemical nanoprobes prepared by labeling the specific antibodies with CdS nanoparticles (CdSNP). After the immunochemical reaction, the CdSNP are dissolved and the metal ions released are reduced at the electrode and read as in the form of current or charge signal, by the well-known anodic stripping technique. Due to the amplification effect on the amperometric/coulombimetric signal produced by the CdSNP, a high detectability can be reached. Thus, sulfapyridine (SPY), one of the most widely used sulfonamide congeners, can be detected in buffer with an IC50current of 0.20±0.25μgL(-1). The immunosensor has been applied to the analysis of residues of this antibiotic in honey samples. Due to the reported formation of sulfonamide-sugar conjugates in this type of matrix, honey samples are first hydrolyzed in acidic media. The use of magnetic particles minimizes the matrix effect allowing to reach a detectability (LOD, limit of detection) of 0.11μgkg(-1) (current measurements), far below the limits established in some countries for these types of residues in honey samples. Due to the use of magnetic racks, multiple samples can be run simultaneously. The whole analysis process can be performed in around 22min. PMID:23313703

  15. Current trends in the development of the electrochemiluminescent immunosensors.

    PubMed

    Muzyka, Kateryna

    2014-04-15

    This review presents a general picture of the current trends and developments (2008-2013) related to electrochemiluminescence-based immunosensors. It briefly covers the milestones of qualitative changes in the field of electrochemiluminescent immunosensors; the peculiarities of the electrochemiluminescent immunoassay formats; the basic mechanisms of ECL detection, main features of early and ongoing approaches in electrochemiluminescent immunoassay commercial instruments, and the recent developments in fabrication of solid-state electrochemiluminescent immunosensors. Moreover, systematized data on biomarkers, immunoassay formats, and novel types of electrochemiluminescent label and immobilization support, such as semiconductor nanocrystals, porous noble metals, graphene, TiO2 nanotube arrays, metal-organic composites, multiwall carbon nanotubes, liposomes, photolummonescent carbone nanocrystals are presented as a table. Considerable efforts have also been devoted towards the following two key points: multiplexing analysis (multi-label, and the multianalyte strategies) and integration in microfluidic lab-on-paper devices with capabilities for point-to-care diagnostics. An immuno-like electrochemiluminescent sensor (based on synthetic receptors-molecularly imprinted polymers), as a new alternative to traditional electrochemiluminescent immunoassay is highlighted. Future perspectives and possible challenges in this rapidly developing area are also discussed. PMID:24292145

  16. Supported protein G on gold electrode: characterization and immunosensor application.

    PubMed

    Hafaiedh, Imen; Chammem, Hanen; Abdelghani, Adnane; Ait, Eric; Feldman, Laurent; Meilhac, Olivier; Mora, Laurence

    2013-11-15

    In this work, we study the electrochemical properties of protein layer grafted on gold electrode for C-reactive protein detection. Two CRP-antibody immobilization methods were used: the first method is based on direct physisorption of CRP-antibody onto the gold surface and the second method is based on oriented CRP-antibody with protein G intermediate layer. The two developed immunosensors were tested against CRP antigen in phosphate buffer saline solution and in human plasma. The electrochemical characterization of each immobilized layers was achieved by cyclic voltammetry and impedance spectroscopy. The morphology of the deposited biomolecules was observed by Atomic Force Microscopy and the roughness was measured. Moreover, contact angle measurement was used for wettability studies. The response of the developed immunosensors was reproducible, rapid, and highly stable and a detection limit of 100 fg/mL and 10 pg/mL antigen was observed with and without protein G respectively. The developed immunosensors was used for CRP detection in human plasma. PMID:24148377

  17. Micromachined magnetoflexoelastic resonator based magnetometer

    NASA Astrophysics Data System (ADS)

    Hatipoglu, Gokhan; Tadigadapa, Srinivas

    2015-11-01

    In this paper, we demonstrate the performance of a magnetoflexoelastic magnetometer consisting of a micromachined ultra-thin (7.5 μm) quartz bulk acoustic resonator on which 500 nm thick magnetostrictive Metglas® (Fe85B5Si10) film is deposited. The resonance frequency of the unimorph resonator structure is sensitively affected by the magnetostrictively induced flexoelastic effect in quartz and is exploited to detect low frequency (<100 Hz) and nanoTesla magnetic fields. The resonance frequency shift is measured by tracking the at-resonance admittance of the resonator as a function of the applied magnetic field. The frequency shifts are linearly correlated to the magnetic field strength. A minimum detectable magnetic flux density of ˜79 nT has been measured for 10 Hz modulated magnetic field input signals which corresponds to a frequency sensitivity of 0.883 Hz/μT.

  18. Electrochemical immunosensor for carcinoembryonic antigen based on nanosilver-coated magnetic beads and gold-graphene nanolabels.

    PubMed

    Chen, Huafeng; Tang, Dianping; Zhang, Bing; Liu, Bingqian; Cui, Yuling; Chen, Guonan

    2012-03-15

    A novel redox-active magnetic nanostructure was synthesized by using a wet chemical method for high-efficiency electrochemical immunoassay of carcinoembryonic antigen (CEA, as a model analyte). The nanostructures based on the combination of a magnetic nanocore, a layer of electroactive poly(o-phenylenediamine) (PPD), and a silver metallic shell displayed good adsorption properties for the attachment of anti-CEA antibody selective to CEA. The magnetic nanostructure presented good redox behaviors to facilitate and modulate the way it was integrated into a magnetic carbon paste electrode. The assay was based on a sandwich-type immunoassay protocol by using nanogold-patterned graphene oxide nanoscales (AuNP-GO), conjugated with horseradish peroxidase-labeled anti-CEA, as secondary antibodies and biofunctionalized magnetic nanostructures as immunosensing probes. Under optimal conditions, the nanoparticle-based immunocomposites exhibited good electrochemical responses for the determination of CEA, and allowed the detection of CEA at a concentration as low as 1.0 pg mL(-1) at a signal-to-noise ratio of 3. In addition, the magnetic immunosensing had good reproducibility, and acceptable accuracy, and could be successfully applied for the detection of CEA in the clinical serum specimens. Significantly, by controlling the target biomolecules, this assay can be easily extended for use with other immunosensings, and thus represents a versatile design routine. PMID:22365686

  19. Label-free immunosensor based on one-step electrodeposition of chitosan-gold nanoparticles biocompatible film on Au microelectrode for determination of aflatoxin B1 in maize.

    PubMed

    Ma, Haihua; Sun, Jizhou; Zhang, Yuan; Bian, Chao; Xia, Shanhong; Zhen, Tong

    2016-06-15

    Gold nanoparticles (AuNPs) embedded in chitosan (CHI) film, well-dispersed and smaller in size (about 10 nm), were fabricated by one-step electrodeposion on Au microelectrode in solution containing chitosan and chloride trihydrate. The nano-structure CHI-AuNPs composite film offers abundant amine groups, good conductivity, excellent biocompatibility and stability for antibody immobilization. The combination of aflatoxin B1 (AFB1) with immobilized antibody introduces a barrier to electron transfer, resulting in current decreasement. The morphologies and characterizations of modified microelectrodes were investigated by scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FT-IR). The proposed non-enzyme and label-free immunosensor exhibited high sensitive amperometric response to AFB1 concentration in two linear ranges of 0.1 to 1 ng mL(-1) and 1 to 30 ng mL(-1), with the detection limit of 0.06 ng mL(-1) (S/N=3). The immunoassay was also applied for analysis of maize samples spiked with AFB1. Considering the sample extraction procedure, the linear range and limit of detection were assessed to be 1.6-16 ng mL(-1) and 0.19 ng mL(-1) respectively. The simple method showed good fabrication controllability and reproducibility for immunosensor design. PMID:26851579

  20. Liquid crystal and gold nanoparticles applied to electrochemical immunosensor for cardiac biomarker.

    PubMed

    Zapp, Eduardo; Westphal, Eduard; Gallardo, Hugo; de Souza, Bernardo; Cruz Vieira, Iolanda

    2014-09-15

    A label-free electrochemical immunosensor based on the ionic liquid crystal (E)-1-decyl-4-[(4-decyloxyphenyl)diazenyl]pyridinium bromide (Br-Py) coated on a glassy carbon electrode (GCE) for the quantitative detection of myoglobin (Mb), a cardiac marker for acute myocardial infarction, is reported herein for the first time. The monoclonal anti-myoglobin antibody (ab-Mb) was covalently immobilized using glyoxal on a film of polyethyleneimine-coated gold nanoparticles (AuNP-PEI). The proposed method for Mb detection is based on voltammetric suppression of the Br-Py signal when the immunosensor was incubated with Mb antigen. The electrochemical performance of the Mb immunosensor was studied by electrochemical impedance spectroscopy, and cyclic and square-wave voltammetry. Under the optimal conditions, the proposed immunosensor shows a good linear relationship between the electrochemical inhibition response and the concentration of Mb over the range of 9.96-72.8 ng mL(-1) with a detection limit of 6.29 ng mL(-1). The results obtained indicate that the proposed immunosensor provides good sensitivity and simple operation for detecting acute myocardial infarction with Mb as a biomarker. PMID:24721423

  1. A novel and label-free immunosensor for bisphenol A using rutin as the redox probe.

    PubMed

    Huang, Ying; Li, Xiaofeng; Zheng, Sining

    2016-11-01

    In this work, a new and label-free electrochemical immunosensor for sensitive detection of bisphenol A was reported. MWCNTs and gold nanoparticles (AuNPs) were modified on glassy carbon electrode surface to enhance current response. The Anti-BPA was immobilized on the modified electrode through AuNPs. Rutin was used for the first time as the redox probe to construct electrochemical immunosensor of bisphenol A. The peak current change due to the specific immuno-interaction between anti-BPA and BPA on the modified electrode surface was utilized to detect bisphenol A. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) were employed to trace the assembly process of the electrochemical immunosensor. Experimental factors affecting the sensitivity of the immunosensor were examined in terms of incubation time and pH of phosphate buffer solution (PBS). Under optimized conditions, the linear range of calibration curve based on the relationship between current response and BPA concentration was from 1.0×10(-8)-1.0×10(-6)M with detection limit of 8.7×10(-9)M (S/N=3). The proposed immunosensor showed good reproducibility, selectivity, stability and was successfully applied to the determination of BPA in real sample. PMID:27591610

  2. Photoelectrochemical Immunosensor for Detection of Carcinoembryonic Antigen Based on 2D TiO2 Nanosheets and Carboxylated Graphitic Carbon Nitride

    PubMed Central

    Wang, Huan; Wang, Yaoguang; Zhang, Yong; Wang, Qi; Ren, Xiang; Wu, Dan; Wei, Qin

    2016-01-01

    Carcinoembryonic antigen (CEA) was used as the model, an ultrasensitive label-free photoelectrochemical immunosensor was developed using 2D TiO2 nanosheets and carboxylated graphitic carbon nitride (g-C3N4) as photoactive materials and ascorbic acid as an efficient electron donor. 2D TiO2 nanosheets was sythsized by surfactant self-assembly method and proved to have higher photoelectrochemical signals than TiO2 nanoparticles. Firstly, carboxylated g-C3N4 could be attached to 2D TiO2 nanosheets through the bond formed between carboxyl group of carboxylated g-C3N4 and TiO2. And the photocurrent of g-C3N4/TiO2 drastically enhances compared to carboxylated g-C3N4 and TiO2. Then, antibody of CEA was bonded to TiO2 through the dentate bond formed between carboxyl group of anti-CEA and TiO2, leading to the decrease of the photocurrents. As proven by PEC experiments and electrochemical impedance spectroscopy (EIS) analysis, the fabrication process of the immunosensor is successful. Under the optimal conditions, the intensity decreased linearly with CEA concentration in the range of 0.01~10 ng/mL. The detection limit is 2.1 pg/mL. The work provides an effective method for the detection of tumor markers and can be extended for the application in food safety and environmental monitoring analysis. PMID:27263659

  3. Planar waveguide optical immunosensors

    NASA Astrophysics Data System (ADS)

    Choquette, Steven J.; Locascio-Brown, Laurie E.; Durst, Richard A.

    1991-03-01

    Monoclonal antibodies were covalently bonded to the surfaces of planar waveguides to confer immunoreacth''ity. Silver-ion diffused waveguides were used to measure theophylline concentrations in a fluorescence immunoassay and silicon nitride waveguides were used to detect theophylline in an absorbance-based immunoassay. Liposomes were employed in both assays as the optically detectable label in a competitive reaction to monitor antigen-antibody complexation. Regeneration of the active antibody site will be discussed.

  4. 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

  5. Electrochemiluminescence immunosensor based on multifunctional luminol-capped AuNPs@Fe3O4 nanocomposite for the detection of mucin-1.

    PubMed

    Wang, Jing-Xi; Zhuo, Ying; Zhou, Ying; Yuan, Ruo; Chai, Ya-Qin

    2015-09-15

    In this work, a novel and multifunctional nanocomposite of luminol capped gold modified Fe3O4 (Lu-AuNPs@Fe3O4) was utilized as the carrier of secondary antibody (Ab2) to fabricate a sandwiched electrochemiluminescence (ECL) immunosensor for ultrasensitive detection of mucin-1 (MUC1). Herein, the luminol capped gold nanoparticles (Lu-AuNPs) were synthesized with HAuCl4 and luminol by the help of NaBH4 at room temperature, and then Lu-AuNPs were adsorbed on the Fe3O4 magnetic nanoparticles (MNPs) to form the nanocomposite of Lu-AuNPs@Fe3O4 via electrostatic interaction. Fe3O4 MNPs in Lu-AuNPs@Fe3O4 exhibited excellent conductivity and admirable catalytic activity in H2O2 decomposition, which could enhance the ECL efficiency of luminol-H2O2 system. In addition, the substrates of gold coated ZnO nanoparticles (AuNPs@ZnO), providing large specific surface areas for primary antibody (Ab1) capturing, were modified on the electrode. As a result, a wide linear range of 7 orders of magnitude from 10 fg/mL to 10 ng/mL was obtained with an ultralow detection limit of 4.5 fg/mL for MUC1. PMID:25950936

  6. Electrochemical Impedance Immunosensor Based on Self-Assembled Monolayers for Rapid Detection of Escherichia coli O157:H7 with Signal Amplification Using Lectin.

    PubMed

    Li, Zhanming; Fu, Yingchun; Fang, Weihuan; Li, Yanbin

    2015-01-01

    Escherichia coli O157:H7 is a predominant foodborne pathogen with severe pathogenicity, leading to increasing attention given to rapid and sensitive detection. Herein, we propose an impedance biosensor using new kinds of screen-printed interdigitated microelectrodes (SPIMs) and wheat germ agglutinin (WGA) for signal amplification to detect E. coli O157:H7 with high sensitivity and time-efficiency. The SPIMs integrate the high sensitivity and short response time of the interdigitated electrodes and the low cost of the screen-printed electrodes. Self-assembling of bi-functional 3-dithiobis-(sulfosuccinimidyl-propionate) (DTSP) on the SPIMs was investigated and was proved to be able to improve adsorption quantity and stability of biomaterials. WGA was further adopted to enhance the signal taking advantage of the abundant lectin-binding sites on the bacteria surface. The immunosensor exhibited a detection limit of 102 cfu·mL(-1), with a linear detection range from 10(2) to 10(7) cfu·mL(-1) (r2 = 0.98). The total detection time was less than 1 h, showing its comparable sensitivity and rapid response. Furthermore, the low cost of one SPIM significantly reduced the detection cost of the biosensor. The biosensor may have great promise in food safety analysis and lead to a portable biosensing system for routine monitoring of foodborne pathogens. PMID:26251911

  7. Multiplexed enzyme-free electrochemical immunosensor based on ZnO nanorods modified reduced graphene oxide-paper electrode and silver deposition-induced signal amplification strategy.

    PubMed

    Sun, Guoqiang; Zhang, Lina; Zhang, Yan; Yang, Hongmei; Ma, Chao; Ge, Shenguang; Yan, Mei; Yu, Jinghua; Song, Xianrang

    2015-09-15

    Herein, an origami multiplexed enzyme-free electrochemical (EC) immunodevice is developed for the first time. Typically, ZnO nanorods (ZNRs) modified reduced graphene oxide (rGO)-paper electrode is used as a sensor platform, in which rGO improves the electronic transmission rate and ZNRs provide abundant sites for capture probes binding. Furthermore, by combining the large surface area of rGO and high catalytic activity of bovine serum protein (BSA)-stabilized silver nanoparticles (Ag@BSA) toward H2O2 reduction, rGO/Ag@BSA composites can be used as an excellent signal labels. The current signal is generated from the reduction of H2O2 and further amplified by a subsequent signal labels-promoted deposition of silver. Under optimal conditions, the proposed immunoassays exhibit excellent precision, high sensitivity and a wide linear range of 0.002-120 mIU mL(-1) for human chorionic gonadotropin, 0.001-110 ng mL(-1) for prostate-specific antigen, and 0.001-100 ng mL(-1) for carcinoembryonic antigen. The results for real sample analysis demonstrate that the newly constructed immunosensor arrays provide a simple and cost-effective method for clinical applications. PMID:25884731

  8. Electrochemical Impedance Immunosensor Based on Self-Assembled Monolayers for Rapid Detection of Escherichia coli O157:H7 with Signal Amplification Using Lectin

    PubMed Central

    Li, Zhanming; Fu, Yingchun; Fang, Weihuan; Li, Yanbin

    2015-01-01

    Escherichia coli O157:H7 is a predominant foodborne pathogen with severe pathogenicity, leading to increasing attention given to rapid and sensitive detection. Herein, we propose an impedance biosensor using new kinds of screen-printed interdigitated microelectrodes (SPIMs) and wheat germ agglutinin (WGA) for signal amplification to detect E. coli O157:H7 with high sensitivity and time-efficiency. The SPIMs integrate the high sensitivity and short response time of the interdigitated electrodes and the low cost of the screen-printed electrodes. Self-assembling of bi-functional 3-dithiobis-(sulfosuccinimidyl-propionate) (DTSP) on the SPIMs was investigated and was proved to be able to improve adsorption quantity and stability of biomaterials. WGA was further adopted to enhance the signal taking advantage of the abundant lectin-binding sites on the bacteria surface. The immunosensor exhibited a detection limit of 102 cfu·mL−1, with a linear detection range from 102 to 107 cfu·mL−1 (r2 = 0.98). The total detection time was less than 1 h, showing its comparable sensitivity and rapid response. Furthermore, the low cost of one SPIM significantly reduced the detection cost of the biosensor. The biosensor may have great promise in food safety analysis and lead to a portable biosensing system for routine monitoring of foodborne pathogens. PMID:26251911

  9. Nanoparticle Labels/ Electrochemical Immunosensor for Detection of Biomarkers

    SciTech Connect

    Liu, Guodong; Wang, Jun; Lin, Yuehe

    2006-06-01

    A sensitive electrochemical immunosensor based on poly(guanine) functionalized silica nanoparticle label has been developed for the detection of protein biomarker, biomarker recombinant human tumor necrosis factor-a(TNF-a).This method is simple, selective, and reproducible for trace biomarker analysis. A remarkable LOD has been achieved through dual signal amplification by poly[G] functionalized silica NPs and catalytic guanine oxidation. The work demonstrates the feasibility of developing an inexpensive, sensitive, and portable device for multiplexed diagnoses of different protein biomarkers.

  10. Optical multiple-analyte immunosensor for water pollution control.

    PubMed

    Barzen, Claudia; Brecht, Andreas; Gauglitz, Guenter

    2002-04-01

    A prototype of a portable optical immunosensor (called river analyser) has been developed. It can be applied for the monitoring of surface water quality. Antibodies carrying a fluorescent label are used for the specific recognition of pollutants, such as frequently applied pesticides. The transduction principle is based on total internal reflection fluorescence (TIRF). The outstanding advantage of the river analyser is, that at least three analytes can be detected simultaneously in one sample. Test cycles and fluid handling are automated and enable unattended measuring. PMID:11849925

  11. Immunosensors using a quartz crystal microbalance

    NASA Astrophysics Data System (ADS)

    Kurosawa, Shigeru; Aizawa, Hidenobu; Tozuka, Mitsuhiro; Nakamura, Miki; Park, Jong-Won

    2003-11-01

    Better analytical technology has been demanded for accurate and rapid determination of trace amounts of chemical compounds, such as marker proteins for disease or endocrine disrupters like dioxin, which might be contained in blood, food and the environment. The study of immunosensors using a quartz crystal microbalance (QCM) has recently focused on conventional detection methods for the determination of chemical compounds together with the development of reagents and processes. This paper introduces the principle of the detection method of QCM immunosensors developed at AIST and its application to the detection of trace amounts of chemical compounds.

  12. An ultrasensitive peroxydisulfate electrochemiluminescence immunosensor for Streptococcus suis serotype 2 based on L-cysteine combined with mimicking bi-enzyme synergetic catalysis to in situ generate coreactant.

    PubMed

    Wang, Haijun; Yuan, Ruo; Chai, Yaqin; Cao, Yaling; Gan, Xianxue; Chen, Yinfeng; Wang, Yan

    2013-05-15

    A novel signal amplification strategy of mimicking bi-enzyme synergetic catalysis to generate coreactant in situ was designed to fabricate an ultrasensitive peroxydisulfate electrochemiluminescence (ECL) immunosensor for detection of Streptococcus suis serotype 2 (SS2). It was the first time to detect SS2 by using ECL. Through the interaction between l-cysteine (l-cys) and hollow PtPd bimetal alloy nanoparticles (HPtPd) to form ((l-cys-HPtPd)n) nanocomposites, the loading amount of l-cys and HPtPd was greatly increased, which could greatly enhance the ECL signal of peroxydisulfate. At the same time, Glucose Oxidase (GOD), used to block nonspecific binding sites of (l-cys-HPtPd)n nanocomposites, could rapidly oxidize d-glucose in the detection solution into gluconic acid accompanying with the generation of H2O2, which was further catalyzed by HPtPd to generate O2. And O2, acted as the coreactant of peroxydisulfate, could greatly amplify the ECL signal. In the process, HPtPd could be regarded as mimicking enzyme, the effect of which was similar to horseradish peroxidase (HRP) in generating O2. With the several amplification factors of a sandwich-type structure we designed, a wide linear ranged from 0.0001 to 100ngmL(-1) was acquired with a relatively low detection limit of 33fgmL(-1) for SS2. The present work demonstrated that the novel strategy had the great advantages in sensitivity, selectivity and reproducibility which might hold a new promise for highly sensitive bioassays applied in clinical detection. PMID:23277341

  13. Sensitive Electrochemiluminescence Immunosensor for Detection of N-Acetyl-β-d-glucosaminidase Based on a "Light-Switch" Molecule Combined with DNA Dendrimer.

    PubMed

    Wang, Haijun; Yuan, Yali; Zhuo, Ying; Chai, Yaqin; Yuan, Ruo

    2016-06-01

    Here, a novel "light-switch" molecule of Ru (II) complex ([Ru(dcbpy)2dppz](2+)-DPEA) with self-enhanced electrochemiluminescence (ECL) property is proposed, which is almost nonemissive in aqueous solution but is brightly luminescent when it intercalates into DNA duplex. Owing to less energy loss and shorter electron-transfer distance, the intramolecular ECL reaction between the luminescent [Ru(dcbpy)2dppz](2+) and coreactive tertiary amine group in N,N-diisopropylethylenediamine (DPEA) makes the obtained "light-switch" molecule possess much higher light-switch efficiency compared with the traditional "light-switch" molecule. For increasing the loading amount and further enhancing the luminous efficiency of the "light-switch" molecule, biotin labeled DNA dendrimer (the fourth generation, G4) is prepared from Y-shape DNA by a step-by-step assembly strategy, which provides abundant intercalated sites for [Ru(dcbpy)2dppz](2+)-DPEA. Meanwhile, the obtained nanocomposite (G4-[Ru(dcbpy)2dppz](2+)-DPEA) could well bind with streptavidin labeled detection antibody (SA-Ab2) due to the existence of abundant biotin. Through sandwiched immunoreaction, an ECL immunosensor was fabricated for sensitive determination of N-acetyl-β-d-glucosaminidase (NAG), a typical biomarker for diabetic nephropathy (DN). The detemination linear range was 0.1 pg mL(-1) to 1 ng mL(-1), and the detection limit was 0.028 pg mL(-1). The developed strategy combining the ECL self-enhanced "light-switch" molecular and DNA nanotechnology offers an effective signal amplification mean and provides ample potential for further bioanalysis and clinical study. PMID:27185239

  14. Chemical sensors based on the modification of a resonator cavity

    NASA Astrophysics Data System (ADS)

    Hennig, Oliver; Mendes, Sergio B.; Fallahi, Mahmoud; Peyghambarian, Nasser

    1999-02-01

    In this paper, we present a chemical sensor based on the modification of an optical resonator: the optical path length of the resonant cavity is changed by the chemical in question, thus shifting its resonant frequency.

  15. Temperature Sensors Based on WGM Optical Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Yu, Nan; Maleki, Lute; Itchenko, Vladimir; Matsko, Andrey; Strekalov, Dmitry

    2008-01-01

    A proposed technique for measuring temperature would exploit differences between the temperature dependences of the frequencies of two different electromagnetic modes of a whispering gallery-mode (WGM) optical resonator. An apparatus based on this technique was originally intended to be part of a control system for stabilizing a laser frequency in the face of temperature fluctuations. When suitably calibrated, apparatuses based on this technique could also serve as precise temperature sensors for purposes other than stabilization of lasers. A sensor according to the proposal would include (1) a transparent WGM dielectric resonator having at least two different sets of modes characterized by different thermo-optical constants and (2) optoelectronic instrumentation for measuring the difference between the temperature-dependent shifts of the resonance frequencies of the two sets of modes.

  16. Immunosensor for the ultrasensitive and quantitative detection of bladder cancer in point of care testing.

    PubMed

    Chuang, Cheng-Hsin; Du, Yi-Chun; Wu, Ting-Feng; Chen, Cheng-Ho; Lee, Da-Huei; Chen, Shih-Min; Huang, Ting-Chi; Wu, Hsun-Pei; Shaikh, Muhammad Omar

    2016-10-15

    An ultrasensitive and real-time impedance based immunosensor has been fabricated for the quantitative detection of Galectin-1 (Gal-1) protein, a biomarker for the onset of multiple oncological conditions, especially bladder cancer. The chip consists of a gold annular interdigitated microelectrode array (3×3 format with a sensing area of 200µm) patterned using standard microfabrication processes, with the ability to electrically address each electrode individually. To improve sensitivity and immobilization efficiency, we have utilized nanoprobes (Gal-1 antibodies conjugated to alumina nanoparticles through silane modification) that are trapped on the microelectrode surface using programmable dielectrophoretic manipulations. The limit of detection of the immunosensor for Gal-1 protein is 0.0078mg/ml of T24 (Grade III) cell lysate in phosphate buffered saline, artificial urine and human urine samples. The normalized impedance variations show a linear dependence on the concentration of cell lysate present while specificity is demonstrated by comparing the immunosensor response for two different grades of bladder cancer cell lysates. We have also designed a portable impedance analyzing device to connect the immunosensor for regular checkup in point of care testing with the ability to transfer data over the internet using a personal computer. We believe that this diagnostic system would allow for improved public health monitoring and aid in early cancer diagnosis. PMID:26777732

  17. Volume coil based on hybridized resonators for magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Jouvaud, C.; Abdeddaim, R.; Larrat, B.; de Rosny, J.

    2016-01-01

    We present an electromagnetic device based on hybridization of four half-wavelength dipoles which increases the uniformity and the strength of the radio-frequency (RF) field of a Magnetic Resonant Imaging (MRI) apparatus. Numerical results show that this Hybridized Coil (HC) excited with a classical loop coil takes advantage of the magnetic hybrid modes. The distribution of the RF magnetic field is experimentally confirmed on a 7-T MRI with a gelatin phantom. Finally, the HC is validated in vivo by imaging the head of an anesthetized rat. We measure an overall increase of the signal to noise ratio with up to 2.4 fold increase in regions of interest far from the active loop coil.

  18. Sol-gel-derived thick-film amperometric immunosensors.

    PubMed

    Wang, J; Pamidi, P V; Rogers, K R

    1998-03-15

    Sol-gel processing is used for the first time for the preparation of electrochemical immunosensors. One-step sensor fabrication, based on the coupling of sol-gel and screen-printing technologies, is employed. A low-temperature cured ink is prepared by dispersion of rabbit immunoglobulin G (RIgG), graphite powder, and a binder in the sol-gel solution. The enzyme-labeled antibody can readily diffuse toward the encapsulated antigen, which retains its binding properties, and the association reaction is easily detected at the dispersed graphite surface. Use of anti-RIgG labeled with alkaline phosphatase, naphthyl phosphate as the substrate, and amperometric detection at +400 mV (vs Ag/AgCl) results in a low detection limit of 5 ng/mL (32 pM) for the solution antigen. Tailoring the porosity of the ceramic-carbon matrix can be used for tuning the assay performance. The high sensitivity, low cost, durability, and simplicity of the new single-use immunosensors make them well suited for various on-site applications. PMID:9530007

  19. Flow-through immunosensors using antibody-immobilized polymer monoliths

    PubMed Central

    Liu, Jikun; Chen, Chien-Fu; Chang, Chih-Wei; DeVoe, Don L.

    2010-01-01

    High-sensitivity and rapid flow-through immunosensors based on photopolymerized surface-reactive polymer monoliths are investigated. The porous monoliths were synthesized within silica capillaries from glycidyl methacrylate and ethoxylated trimethylolpropane triacrylate precursors, providing a tortuous pore structure with high surface area for the immobilization of antibodies or other biosensing ligands. The unique morphology of the monolith ensures efficient mass transport and interactions between solvated analyte molecules and covalently immobilize antibodies anchored to the monolith surface, resulting in rapid immunorecognition. The efficacy of this approach is demonstrated through a direct immunoassay model using anti-IgG as a monolith-bound capture antibody and fluorescein-labeled IgG as an antigen. In situ antigen measurements exhibited a linear response over a concentration range between 0.1 - 50 ng/mL with 5 min assay times, while controllable injection of 1 μL volumes of antigen through the monolith elements yielded a mass detection limit of 100 pg (~700 amol). These results suggest that porous monolith supports represent a flexible and promising material for the fabrication of rapid and sensitive immunosensors suitable for integration into capillary or microfluidic devices. PMID:20598520

  20. Copper oxide assisted cysteine hierarchical structures for immunosensor application

    SciTech Connect

    Pandey, Chandra Mouli; Sumana, Gajjala; Tiwari, Ida

    2014-09-08

    The present work describes the promising electrochemical immunosensing strategy based on copper (II) assisted hierarchical cysteine structures (CuCys) varying from star to flower like morphology. The CuCys having average size of 10 μm have been synthesised using L-Cysteine as initial precursor in presence of copper oxide under environmentally friendly conditions in aqueous medium. To delineate the synthesis mechanism, detailed structural investigations have been carried out using characterization techniques such as X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The electrochemical behaviour of self-assembled CuCys on gold electrode shows surface controlled electrode reaction with an apparent electron transfer rate constant of 3.38 × 10{sup −4 }cm s{sup −1}. This innovative platform has been utilized to fabricate an immunosensor by covalently immobilizing monoclonal antibodies specific for Escherichia coli O157:H7 (E. coli). Under the optimal conditions, the fabricated immunosensor is found to be sensitive and specific for the detection of E. coli with a detection limit of 10 cfu/ml.

  1. Aptasensors Based on Whispering Gallery Mode Resonators.

    PubMed

    Nunzi Conti, Gualtiero; Berneschi, Simome; Soria, Silvia

    2016-01-01

    In this paper, we review the literature on optical evanescent field sensing in resonant cavities where aptamers are used as biochemical receptors. The combined advantages of highly sensitive whispering gallery mode resonator (WGMR)-based transducers, and of the unique properties of aptamers make this approach extremely interesting in the medical field, where there is a particularly high need for devices able to provide real time diagnosis for cancer, infectious diseases, or strokes. However, despite the superior performances of aptamers compared to antibodies and WGMR to other evanescent sensors, there is not much literature combining both types of receptors and transducers. Up to now, the WGMR that have been used are silica microspheres and silicon oxynitride (SiON) ring resonators. PMID:27438861

  2. Nano and Microparticle-Enhanced Immunosensor Approaches for the Detection of Cancer Biomarker Proteins

    NASA Astrophysics Data System (ADS)

    Mani, Vigneshwaran

    Accurate, sensitive, point-of-care multiplexed protein measurements are critical for early disease detection and monitoring, impacting biomarker and drug discovery, and personalized medicine. Significant application involves monitoring panels of proteins in the blood that are biomarkers for diagnosing cancer. However, measurements of biomarker panels in blood or other bodily fluids have been slow to integrate into current practice of cancer diagnostics partly due to the lack of technically simple, low-cost, sensitive, point-of-care multiplexed measurement devices, as well as the lack of rigorously validated protein panels. The present thesis in part addresses these limitations by the development of electrochemical and surface plasmon resonance (SPR) immunosensors utilizing 1mum superparamagnetic labels for accurate detection of prostate cancer biomarker proteins in patient serum samples. Electrochemical discrete immunosensors featuring nanostructured surface with densely packed 5 nm glutathione-coated gold nanoparticles coupled with multi-enzyme magnetic particle (MP) labels enabled measurement of prostate specific antigen (PSA) with a detection limit (DL) of 0.5 pg mL-1 in undiluted serum. Such low DLs are attributed to high surface area, conductivity of nanostructured surface, and multi-enzyme signal amplification. DLs are further improved by utilizing MP bioconjugated with more than 100,000 antibody labels to offline capture proteins from the serum sample matrix, minimizing nonspecific binding of interfering proteins on sensor surface before detection. This approach provided an unprecedented 10 fg DL mL-1 for PSA in undiluted serum using a flow SPR biosensor. Finally electrochemical microfluidic immunoarrays featuring nanostructured surface and offline protein capture by multi-label MPs enabled multiplexed detection of prostate cancer biomarkers PSA and interleukin-6 (IL-6). These approaches provided up to 1000-fold lower DLs compared to commercial bead based

  3. Chemical Sensors Based on Optical Ring Resonators

    NASA Technical Reports Server (NTRS)

    Homer, Margie; Manfreda, Allison; Mansour, Kamjou; Lin, Ying; Ksendzov, Alexander

    2005-01-01

    Chemical sensors based on optical ring resonators are undergoing development. A ring resonator according to this concept is a closed-circuit dielectric optical waveguide. The outermost layer of this waveguide, analogous to the optical cladding layer on an optical fiber, is a made of a polymer that (1) has an index of refraction lower than that of the waveguide core and (2) absorbs chemicals from the surrounding air. The index of refraction of the polymer changes with the concentration of absorbed chemical( s). The resonator is designed to operate with relatively strong evanescent-wave coupling between the outer polymer layer and the electromagnetic field propagating along the waveguide core. By virtue of this coupling, the chemically induced change in index of refraction of the polymer causes a measurable shift in the resonance peaks of the ring. In a prototype that has been used to demonstrate the feasibility of this sensor concept, the ring resonator is a dielectric optical waveguide laid out along a closed path resembling a racetrack (see Figure 1). The prototype was fabricated on a silicon substrate by use of standard techniques of thermal oxidation, chemical vapor deposition, photolithography, etching, and spin coating. The prototype resonator waveguide features an inner cladding of SiO2, a core of SixNy, and a chemical-sensing outer cladding of ethyl cellulose. In addition to the ring Chemical sensors based on optical ring resonators are undergoing development. A ring resonator according to this concept is a closed-circuit dielectric optical waveguide. The outermost layer of this waveguide, analogous to the optical cladding layer on an optical fiber, is a made of a polymer that (1) has an index of refraction lower than that of the waveguide core and (2) absorbs chemicals from the surrounding air. The index of refraction of the polymer changes with the concentration of absorbed chemical( s). The resonator is designed to operate with relatively strong

  4. Protein Sensors Based on Optical Ring Resonators

    NASA Technical Reports Server (NTRS)

    Lin, Ying; Ksendzov, Alexander

    2006-01-01

    Prototype transducers based on integrated optical ring resonators have been demonstrated to be useful for detecting the protein avidin in extremely dilute solutions. In an experiment, one of the transducers proved to be capable of indicating the presence of avidin at a concentration of as little as 300 pM in a buffer solution a detection sensitivity comparable to that achievable by previously reported protein-detection techniques. These transducers are serving as models for the further development of integrated-optics sensors for detecting small quantities of other proteins and protein-like substances. The basic principle of these transducers was described in Chemical Sensors Based on Optical Ring Resonators (NPO-40601), NASA Tech Briefs, Vol. 29, No. 10 (October 2005), page 32. The differences between the present transducers and the ones described in the cited prior article lie in details of implementation of the basic principle. As before, the resonator in a transducer of the present type is a closed-circuit dielectric optical waveguide. The outermost layer of this waveguide, analogous to the optical cladding layer on an optical fiber, consists of a layer comprising sublayers having indices of refraction lower than that of the waveguide core. The outermost sublayer absorbs the chemical of interest (in this case, avidin). The index of refraction of the outermost sublayer changes with the concentration of absorbed avidin. The resonator is designed to operate with relatively strong evanescent-wave coupling between the outer sublayer and the electromagnetic field propagating along the waveguide core. By virtue of this coupling, the chemically induced change in the index of refraction of the outermost sublayer causes a measurable change in the spectrum of the resonator output.

  5. The fabrication of a label-free electrochemical immunosensor using Nafion/carbon nanotubes/charged pyridinecarboxaldehyde composite film.

    PubMed

    Zhang, Xiangyang; Shen, Youming; Shen, Guangyu; Wang, Sha

    2016-07-01

    A label-free electrochemical immunosensor based on Nafion/carbon nanotubes (CNTs)/charged pyridinecarboxaldehyde composite film was developed for the detection of hepatitis B surface antigen. Nafion/CNTs/charged pyridinecarboxaldehyde nanocomposites were prepared by dispersing charged pyridinecarboxaldehyde and CNTs in Nafion solution. The nanocomposites were cast on the electrode surface to form aldehyde-terminated composite film that can covalently bind antibody on the film without using other reagent. The immunosensor response was linearly changed with hepatitis B surface antigen concentration in the range from 0.1 to 25 ng ml(-1) with a detection limit (signal/noise ratio = 3) of 0.04 ng ml(-1). Some important advantages such as simple preparation, good stability, reproducibility, and selectivity of the immunosensor were achieved. PMID:27060531

  6. General Bioluminescence Resonance Energy Transfer Homogeneous Immunoassay for Small Molecules Based on Quantum Dots.

    PubMed

    Yu, Xuezhi; Wen, Kai; Wang, Zhanhui; Zhang, Xiya; Li, Chenglong; Zhang, Suxia; Shen, Jianzhong

    2016-04-01

    Here, we describe a general bioluminescence resonance energy transfer (BRET) homogeneous immunoassay based on quantum dots (QDs) as the acceptor and Renilla luciferase (Rluc) as the donor (QD-BRET) for the determination of small molecules. The ratio of the donor-acceptor that could produce energy transfer varied in the presence of different concentrations of free enrofloxacin (ENR), an important small molecule in food safety. The calculated Förster distance (R0) was 7.86 nm. Under optimized conditions, the half-maximal inhibitory concentration (IC50) for ENR was less than 1 ng/mL and the linear range covered 4 orders of magnitude (0.023 to 25.60 ng/mL). The cross-reactivities (CRs) of seven representative fluoroquinolones (FQs) were similar to the data obtained by an enzyme-linked immunosorbent assay (ELISA). The average intra- and interassay recoveries from spiked milk of were 79.8-118.0%, and the relative standard deviations (RSDs) were less than 10%, meeting the requirement of residue detection, which was a satisfactory result. Furthermore, we compared the influence of different luciferase substrates on the performance of the assay. Considering sensitivity and stability, coelenterazine-h was the most appropriate substrate. The results from this study will enable better-informed decisions on the choice of Rluc substrate for QD-BRET systems. For the future, the QD-BRET immunosensor could easily be extended to other small molecules and thus represents a versatile strategy in food safety, the environment, clinical diagnosis, and other fields. PMID:26948147

  7. Cross-talk-free multiplexed immunoassay using a disposable electrochemiluminescent immunosensor array coupled with a non-array detector.

    PubMed

    Li, Cuifang; Fu, Zhifeng; Li, Zongyun; Wang, Zhenxing; Wei, Wei

    2011-09-15

    A disposable electrochemiluminescent (ECL) immunosensor array was fabricated on a screen-printed carbon electrode (SPCE) substrate to perform multiplexed immunoassay (MIA) for the first time. The SPCE substrate was composed of an array of four carbon working electrodes, one common Ag/AgCl reference electrode, and one common carbon counter electrode. The immunosensor array was constructed by site-selectively immobilizing multiple antigens on different working electrodes of the SPCE substrate. With a competitive immunoassay format, the immobilized antigens competed with antigens in the sample to capture their corresponding tri(2,2'-bipyridyl)ruthenium(II)-labeled antibodies. The ECL signals from the immunosensors in this array were sequentially detected by a photomultiplier with the aid of a homemade single-pore-four-throw switch. Due to the ECL readout mechanism and the sequential detection mode, it could avoid the cross-talk between the adjacent immunosensors, which was common in other reported immunosensor array. Human, rabbit and mouse immunoglobulin Gs were near-simultaneously assayed as the model analytes. The linear ranges for them were 10-400, 20-400, and 20-400 ng/mL, with detection limits of 2.9, 6.1 and 6.5 ng/mL (S/N=3), respectively. This novel ECL strategy based on immunosensor array coupled with non-array detector provided a simple, sensitive, low-cost and time-saving approach for MIA. It showed great application potential in point-of-care test and field analysis of bio-agents, with mass production potential and high throughput. PMID:21778047

  8. SIMPLE SURFACE PLASMON RESONANCE-BASED DOSEMETER.

    PubMed

    Urbonavičius, Benas Gabrielis; Adlienė, Diana

    2016-06-01

    The interest to application of various surface plasmon resonance (SPR)-based sensors for the investigation of chemical and biological processes in thin layers deposited on the grating's surface/media is developing. Characterisation of processes as well as specimen's features might be performed analysing variations in optical properties (refraction index) of these thin layers. SPR sensors by default are characterised by high resolution and small uncertainties, and measurements might be performed in situ High-resolution, low-cost, SPR-based dosemeter concept has been proposed and realised depositing dose-sensitive nPAG gel layer onto diffraction grating's surface. The experimental set-up and method for information read out from the sensor were developed and implemented. Obtained results show a potential application of SPR-based dosemeter for dose measurements/mapping in steep gradient fields and/or large area fields. PMID:26535002

  9. Tunable Fano resonance in a single-ring-resonator-based add/drop interferometer.

    PubMed

    Wang, Kaiyang; Liu, Xiaoqi; Yu, Changqiu; Zhang, Yundong

    2013-07-10

    We theoretically study a single-ring-resonator-based add/drop interferometer to achieve tunable Fano resonance. The Fano resonance results from the interference of two resonant beams propagating in the ring resonator. The line shapes of the Fano resonance are tunable by controlling the coupling coefficients between the waveguide and ring resonator. The spectra of the drop port and through port of the add/drop interferometer are horizontally mirror-symmetric. A box-like spectral response can be produced with the proper coupling coefficient owing to the double resonances. When the phase difference between the two light inputs to the add/drop interferometer is compensated, a doubled free spectral range can be obtained. PMID:23852203

  10. Liver Cancer Detection by a Simple, Inexpensive and Effective Immunosensor with Zinc Oxide Nanoparticles

    PubMed Central

    Ching, Congo Tak-Shing; van Hieu, Nguyen; Cheng, Teng-Yun; Fu, Lin-Shien; Sun, Tai-Ping; Liu, Ming-Yen; Huang, Su-Hua; Yao, Yan-Dong

    2015-01-01

    Regular monitoring of blood α-fetoprotein (AFP) and/or carcino-embryonic antigen (CEA) levels is important for the routine screening of liver cancer. However, AFP and CEA have a much lower specificity than des-γ-carboxyprothrombin (DCP) to detect liver cancer. Therefore, the study reported here was designed, to develop a screen-printed DCP immunosensor incorporating zinc oxide nanoparticles, for accurate determination of DCP. The designed immunosensor shows low detection limits for the detection of DCP: 0.440 ng/mL (based on impedance measurement), 0.081 ng/mL (based on real part of impedance measurement) and 0.078 ng/mL (based on imaginary part of impedance measurement), within the range of 3.125 ng/mL to 2000 ng/mL. In addition, there was little interference to DCP determination by molecules such as Na+, K+, Ca2+, Cl−, glucose, urea, and uric acid. It is therefore concluded that the DCP immunosensor developed and reported here is simple, inexpensive and effective, and shows promise in the rapid screening of early-stage liver cancer at home with a point-of-care approach. PMID:26610504

  11. Liver Cancer Detection by a Simple, Inexpensive and Effective Immunosensor with Zinc Oxide Nanoparticles.

    PubMed

    Ching, Congo Tak-Shing; van Hieu, Nguyen; Cheng, Teng-Yun; Fu, Lin-Shien; Sun, Tai-Ping; Liu, Ming-Yen; Huang, Su-Hua; Yao, Yan-Dong

    2015-01-01

    Regular monitoring of blood α-fetoprotein (AFP) and/or carcino-embryonic antigen (CEA) levels is important for the routine screening of liver cancer. However, AFP and CEA have a much lower specificity than des-γ-carboxyprothrombin (DCP) to detect liver cancer. Therefore, the study reported here was designed, to develop a screen-printed DCP immunosensor incorporating zinc oxide nanoparticles, for accurate determination of DCP. The designed immunosensor shows low detection limits for the detection of DCP: 0.440 ng/mL (based on impedance measurement), 0.081 ng/mL (based on real part of impedance measurement) and 0.078 ng/mL (based on imaginary part of impedance measurement), within the range of 3.125 ng/mL to 2000 ng/mL. In addition, there was little interference to DCP determination by molecules such as Na⁺, K⁺, Ca(2+), Cl(-), glucose, urea, and uric acid. It is therefore concluded that the DCP immunosensor developed and reported here is simple, inexpensive and effective, and shows promise in the rapid screening of early-stage liver cancer at home with a point-of-care approach. PMID:26610504

  12. Advances in ovarian cancer diagnosis: A journey from immunoassays to immunosensors.

    PubMed

    Sharma, Shikha; Raghav, Ragini; O'Kennedy, Richard; Srivastava, Sudha

    2016-07-01

    This review focuses on the technological advancements, challenges and trends in immunoassay technologies for ovarian cancer diagnosis. Emphasis is placed on the principles of the technologies, their merits and limitations and on the evolution from laboratory-based methods to point-of-care devices. While the current market is predominantly associated with clinical immunoassay kits, over the last decade a major thrust in development of immunosensors is evident due to their potential in point-of-care devices. Technological advancements in immunosensors, extending from labeled to label-free detection, with and without mediators, for enhancing proficiencies and reliability have been dealt with in detail. Aspects of the utilisation of nanomaterials and immobilization strategies for enhancing sensitivity and altering the detection range have also been addressed. Finally, we have discussed some distinct characteristics and limitations associated with the recently commericalised technologies used for quantitation of relevant ovarian cancer markers. PMID:27233124

  13. Highly selective and sensitive detection of β-agonists using a surface plasmon resonance sensor based on an alkanethiol monolayer functionalized on a Au surface.

    PubMed

    Suherman; Morita, Kinichi; Kawaguchi, Toshikazu

    2015-05-15

    Immunosensor surfaces for surface plasmon resonance (SPR) have been constructed using a functionalized succinimidyl propanethiol monolayer as a linker to immobilize β-agonist protein conjugates on a Au surface. Because β-agonist is a small molecule, an indirect competitive inhibition immunoassay was used for detection. The lowest detection limits for ractopamine and salbutamol were 10 ppt (10 pg mL(-1)) and 5 ppt (5 pg mL(-1)), respectively. The fabricated immunosensor surface can be used again for detection after regeneration in 0.1 M sodium hydroxide. It was found that the same sensor surface could be reused for performing over 100 rapid immunoreactions. Moreover, one immunosensing-regeneration cycle requires only 600 s. The fabricated immunosensor surfaces were characterized using SPR and scanning tunneling microscopy observation. In the kinetic study of the indirect competitive immunosensing inhibition, the affinity constant (K1) of salbutamol antibody was smaller than the K1 of ractopamine antibody. Compared to a previous study of clenbuterol detection, it was concluded that the high K1 was coupled with low sensitivity. In the selectivity study, both immunosensor surfaces provided >90% of confidence level for the specific detection of β-agonist compounds. The fabrication of highly selective and sensitive sensor surfaces for detecting β-agonist compounds was confirmed. PMID:25192871

  14. Nanomaterial Labels in Electrochemical Immunosensors and Immunoassays

    SciTech Connect

    Liu, Guodong; Lin, Yuehe

    2007-12-15

    This article reviews recent advances in nanomaterial labels in electrochemical immunosensors and immunoassays. Various nanomaterial labels are discussed, including colloidal gold/silver, semiconductor nanoparticles, and markers loaded nanocarriers (carbon nanotubes, apoferritin, silica nanoparticles, and liposome beads). The enormous signal enhancement associated with the use of nanomaterial labels and with the formation of nanomaterial–antibody-antigen assemblies provides the basis for ultrasensitive electrochemical detection of disease-related protein biomarkers, biothreat agents, or infectious agents. In general, all endeavors cited here are geared to achieve one or more of the following goals: signal amplification by several orders of magnitude, lower detection limits, and detecting multiple targets.

  15. All optical modulator based on silicon resonator

    NASA Astrophysics Data System (ADS)

    Pinhas, Hadar; Bidani, Liron; Baharav, Oded; Sinvani, Moshe; Danino, Meir; Zalevsky, Zeev

    2015-08-01

    In this paper we present an all-optical silicon modulator, where a silicon slab (450 μm) thick is coated on both sides to get a Fabry-Perot resonator for laser beam at wavelength of 1550nm. Most of the modulators discussed in literature, are driven by electrical field rather than by light. We investigate new approaches regarding the dependence of the absorption of the optical signal on the control laser pulse at 532 nm having 5nm pulse width. Our silicon based Fabry-Perot resonator increases the intrinsic c-Si finesse to >10, instead of the uncoated silicon with natural finesse of 2.5. The improved finesse is shown to have significant effect on the modulation depth using a pulsed laser. A modulation of 12dB was attained. The modulation is ascribed to two different effects - The Plasma Dispersion Effect (PDE) and the Thermo- Optic Effect (TOE). The PDE causes increase in the signal absorption in silicon via the absorption of the control laser light. On top of that, the transmission of the signal can decrease dramatically in high finesse resonators due to change in the refractive index due to TOE. The changes in the signal's absorption coefficient and in the refractive index are the result of incremental change in the concentration of free carriers. The TOE gives rise to higher refractive index as opposed to the PDE which triggers a decrease in the refractive index. Finally, tradeoff considerations are presented on how to modify one effect to counter the other one, leading to an optimal device having reduced temperature dependence.

  16. Resonance Parameter Adjustment Based on Integral Experiments

    DOE PAGESBeta

    Sobes, Vladimir; Leal, Luiz; Arbanas, Goran; Forget, Benoit

    2016-06-02

    Our project seeks to allow coupling of differential and integral data evaluation in a continuous-energy framework and to use the generalized linear least-squares (GLLS) methodology in the TSURFER module of the SCALE code package to update the parameters of a resolved resonance region evaluation. We recognize that the GLLS methodology in TSURFER is identical to the mathematical description of a Bayesian update in SAMMY, the SAMINT code was created to use the mathematical machinery of SAMMY to update resolved resonance parameters based on integral data. Traditionally, SAMMY used differential experimental data to adjust nuclear data parameters. Integral experimental data, suchmore » as in the International Criticality Safety Benchmark Experiments Project, remain a tool for validation of completed nuclear data evaluations. SAMINT extracts information from integral benchmarks to aid the nuclear data evaluation process. Later, integral data can be used to resolve any remaining ambiguity between differential data sets, highlight troublesome energy regions, determine key nuclear data parameters for integral benchmark calculations, and improve the nuclear data covariance matrix evaluation. Moreover, SAMINT is not intended to bias nuclear data toward specific integral experiments but should be used to supplement the evaluation of differential experimental data. Using GLLS ensures proper weight is given to the differential data.« less

  17. Optical immunosensors for detection of Listeria monocytogenes and Salmonella enteritidis from food

    NASA Astrophysics Data System (ADS)

    Bhunia, Arun K.; Geng, Tao; Lathrop, Amanda; Valadez, Angela; Morgan, Mark T.

    2004-03-01

    Listeria monocytogenes and Salmonella are two major foodborne pathogens of significant concern. Two optical evanescent wave immunosensors were evaluated for detection: Antibody-coupled fiber-optic biosensor and a surface plasmon resonant (SPR) immunosensor. In the fiber-optic sensor, polyclonal antibodies for the test organisms were immobilized on polystyrene fiber wave -guides using streptavidin - biotin chemistry. Cyanine 5 -labeled monoclonal antibodies C11E9 (for L. monocytogenes) and SF-11 (for Salmonella Enteritidis) were used to generate a specific fluorescent signal. Signal acquisition was performed by launching a laser-light (635 nm) from an Analyte-2000. This immunosensor was able to detect 103 - 109 cfu/ml of L. monocytogenes or 106-109 cfu/ml of Salmonella Enteritidis and the assays were conducted at near real-time with results obtained within one hour of sampling. The assays were specific and showed signal even in the presence of other microorganisms such as E. coli, Enterococcus faecalis or Salmonella Typhimurium. In the SPR system, IAsys instrument (resonant mirror sensor) was used. Monoclonal antibody-C11E9 was directly immobilized onto a carboxylate cuvette. Whole Listeria cells at various concentrations did not yield any signal while surface protein extracts did. Crude protein extracts from L. monocytogenes and L. innocua had average binding responses of around 150 arc sec (0.25 ng/mm2), which was significantly different from L. grayi, L. ivanovii, or L. welshimeri with average responses of <48 arc sec. Both fiber-optic and SPR sensors show promise in near real-time detection of foodborne L. monocytogenes and Salmonella Enteritidis.

  18. Development of a label-free immunosensor system for detecting plasma cortisol levels in fish.

    PubMed

    Wu, Haiyun; Ohnuki, Hitoshi; Hibi, Kyoko; Ren, Huifeng; Endo, Hideaki

    2016-02-01

    Fishes display a wide variation in their physiological responses to stress, which is clearly evident in the plasma corticosteroid changes, chiefly cortisol levels in fish. In the present study, we describe a novel label-free immunosensor for detecting plasma cortisol levels. The method is based on immunologic reactions and amperometric measurement using cyclic voltammetry. For the immobilization of the antibody on the surface of sensing electrode, we used a self-assembled monolayer of thiol-containing compounds. Using this electrode, we detect the CV signal change caused by the generation of antigen-antibody complex. The immunosensor showed a response to cortisol levels, and the anodic peak value linearly decreased with a correlation coefficient of 0.990 in diluted plasma. The specificity of the label-free immunosensor system was investigated using other steroid hormones, such as 17α, 20β-dihydroxy-4-pregnen-3-one, progesterone, estriol, estradiol, and testosterone. The specific detection of cortisol was suggested by a minimal change from -0.32 to 0.51 μA in the anodic peak value of the other steroid hormones. The sensor system was used to determine the plasma cortisol levels in Nile tilapia (Oreochromis niloticus), and the results were compared with those of the same samples determined using the conventional method (ELISA). A good correlation was obtained between values determined using both methods (correlation coefficient 0.993). These findings suggest that the proposed label-free immunosensor could be useful for rapid and convenient analysis of cortisol levels in fish plasma samples. PMID:26254257

  19. Detection of Explosives in a Dynamic Marine Environment Using a Moored TNT Immunosensor

    PubMed Central

    Charles, Paul T.; Adams, André A.; Deschamps, Jeffrey R.; Veitch, Scott; Hanson, Al; Kusterbeck, Anne W.

    2014-01-01

    A field demonstration and longevity assessment for long-term monitoring of the explosive 2,4,6-trinitrotoluene (TNT) in a marine environment using an anti-TNT microfluidic immunosensor is described. The TNT immunosensor is comprised of a microfluidic device with 39 parallel microchannels (2.5 cm × 250 μm × 500 μm, L × W × D) fabricated in poly(methylmethacrylate) (PMMA), then chemically functionalized with antibodies possessing a high affinity for TNT. Synthesized fluorescence reporter complexes used in a displacement-based assay format were used for TNT identification. For field deployment the TNT immunosensor was configured onto a submersible moored steel frame along with frame controller, pumps and TNT plume generator and deployed pier side for intermittent plume sampling of TNT (1h increments). Under varying current and tidal conditions trace levels of TNT in natural seawater were detected over an extended period (>18 h). Overnight operation and data recording was monitored via a web interface. PMID:24583970

  20. Detection of explosives in a dynamic marine environment using a moored TNT immunosensor.

    PubMed

    Charles, Paul T; Adams, André A; Deschamps, Jeffrey R; Veitch, Scott; Hanson, Al; Kusterbeck, Anne W

    2014-01-01

    A field demonstration and longevity assessment for long-term monitoring of the explosive 2,4,6-trinitrotoluene (TNT) in a marine environment using an anti-TNT microfluidic immunosensor is described. The TNT immunosensor is comprised of a microfluidic device with 39 parallel microchannels (2.5 cm × 250 µm × 500 µm, L × W × D) fabricated in poly(methylmethacrylate) (PMMA), then chemically functionalized with antibodies possessing a high affinity for TNT. Synthesized fluorescence reporter complexes used in a displacement-based assay format were used for TNT identification. For field deployment the TNT immunosensor was configured onto a submersible moored steel frame along with frame controller, pumps and TNT plume generator and deployed pier side for intermittent plume sampling of TNT (1h increments). Under varying current and tidal conditions trace levels of TNT in natural seawater were detected over an extended period (>18 h). Overnight operation and data recording was monitored via a web interface. PMID:24583970

  1. Analysis of zearalenone in cereal and Swine feed samples using an automated flow-through immunosensor.

    PubMed

    Urraca, Javier L; Benito-Peña, Elena; Pérez-Conde, Concepción; Moreno-Bondi, María C; Pestka, James J

    2005-05-01

    The development of a sensitive flow-though immunosensor for the analysis of the mycotoxin zearalenone in cereal samples is described. The sensor was completely automated and was based on a direct competitive immunosorbent assay and fluorescence detection. The mycotoxin competes with a horseradish-peroxidase-labeled derivative for the binding sites of a rabbit polyclonal antibody. Control pore glass covalently bound to Prot A was used for the oriented immobilization of the antibody-antigen immunocomplexes. The immunosensor shows an IC(50) value of 0.087 ng mL(-1) (RSD = 2.8%, n = 6) and a dynamic range from 0.019 to 0.422 ng mL(-1). The limit of detection (90% of blank signal) of 0.007 ng mL(-1) (RSD = 3.9%, n = 3) is lower than previously published methods. Corn, wheat, and swine feed samples have been analyzed with the device after extraction of the analyte using accelerated solvent extraction (ASE). The immunosensor has been validated using a corn certificate reference material and HPLC with fluorescence detection. PMID:15853369

  2. 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. PMID:24292139

  3. Development of optical immunosensors and their application to the analysis of human bone morphogenetic protein-7 (BMP-7)

    NASA Astrophysics Data System (ADS)

    Kim, Chun-Kwang; Rhee, Jong Il; Sohn, Ok-Jae

    2011-03-01

    In this study, a few optical immunosensors were developed to determine the concentration of BMP-7. Hydrophilic CdSe/ZnS quantum dots (QDs) were synthesized and conjugated to the antibody of BMP-7 (BMP-7Ab). The QDconjugated BMP-7Ab was used as a fluorescence probe at excitation and emission wavelengths of 470 nm and 585 nm, respectively. It was immobilized either on the bottom of the well of a 96-well microtiter plate or on the tip of an optical fiber. Two immunoassays, i.e. the direct and sandwich assays, were studied for their sensitivity. The sensitivity of the direct immunoassay was 1296.21, compared to 384.69 for the sandwich assay. The linear detection range was 0.0-1.0 ng/mL for both assays. Based on the results of the microtiter plate technique, the direct assay technique was used for the development of an optical fiber immunosensor. The optical fiber immunosensor has a linear detection range between 0.0 and 10.0 ng/mL with a detection limit of 0.413 ng/mL. The optical fiber immunosensor was applied to the sequential injection analysis for the automatic determination of BMP-7.

  4. Flow immunoassay of trinitrophenol based on a surface plasmon resonance sensor using a one-pot immunoreaction with a high molecular weight conjugate.

    PubMed

    Kobayashi, Masatoshi; Sato, Masahiro; Li, Yan; Soh, Nobuaki; Nakano, Koji; Toko, Kiyoshi; Miura, Norio; Matsumoto, Kiyoshi; Hemmi, Akihide; Asano, Yasukazu; Imato, Toshihiko

    2005-12-15

    A surface plasmon resonance (SPR) immunosensor based on a competitive immunoreaction for the determination of trinitrophenol (TNP) is described. A goat anti-mouse IgG (1st antibody), which recognizes an Fc moiety of an antibody, was immobilized on a gold film of an SPR sensor chip by physical adsorption. A TNP solution containing a fixed concentration of a mouse anti-TNP monoclonal antibody (2nd antibody) and a TNP-keyhole limpet hemocyanin (KLH) conjugate was incubated in one-pot and introduced into the sensor chip. The TNP-KLH conjugate competes with TNP for binding with the 2nd antibody. The resulting complex of the 2nd antibody with the TNP-KLH conjugate was bound to the 1st antibody, which is immobilized on the sensor chip. The SPR sensor signal based on resonance angle shift is dependent on the concentration of TNP in the incubation solution in the range from 25ppt to 25ppb, and the coefficient of variation of the SPR signals for the 25ppb TNP solution was determined to be 13% (n=4). The experimental results for the adsorption constant of the 1st antibody on the sensor chip and the binding constant of the 1st antibody complex with the 2nd antibody are discussed, together with theoretical considerations. PMID:18970305

  5. A lateral flow immunosensor for direct, sensitive, and highly selective detection of hemoglobin A1c in whole blood.

    PubMed

    Ang, Shu Hwang; Thevarajah, T Malathi; Woi, Pei Meng; Alias, Yatimah binti; Khor, Sook Mei

    2016-03-15

    An immunosensor that operates based on the principles of lateral flow was developed for direct detection of hemoglobin A1c (HbA1c) in whole blood. We utilized colloidal gold-functionalized antibodies to transduce the specific signal generated when sandwich immuno-complexes were formed on the strip in the presence of HbA1c. The number and intensity of the test lines on the strips indicate normal, under control, and elevated levels of HbA1c. In addition, a linear relationship between HbA1c levels and immunosensor signal intensity was confirmed, with a dynamic range of 4-14% (20-130 mmol mol(-1)) HbA1c. Using this linear relationship, we determined the HbA1c levels in blood as a function of the signal intensity on the strips. Measurements were validated using the Bio-Rad Variant II HPLC and DCA Vantage tests. Moreover, the immunosensor was verified to be highly selective for detection of HbA1c against HbA0, glycated species of HbA0, and HbA2. The limit of detection was found to be 42.5 μg mL(-1) (1.35 mmol mol(-1)) HbA1c, which is reasonably sensitive compared to the values reported for microarray immunoassays. The shelf life of the immunosensor was estimated to be 1.4 months when stored at ambient temperature, indicating that the immunoassay is stable. Thus, the lateral flow immunosensor developed here was shown to be capable of performing selective, accurate, rapid, and stable detection of HbA1c in human blood samples. PMID:26927875

  6. Correlation of Capture Efficiency with the Geometry, Transport, and Reaction Parameters in Heterogeneous Immunosensors.

    PubMed

    Rath, Dharitri; Panda, Siddhartha

    2016-02-01

    Higher capture efficiency of biomarkers in heterogeneous immunosensors would enable early detection of diseases. Several strategies are used to improve the capture efficiency of these immunosensors including the geometry of the system along with the transport and reaction parameters. Having a prior knowledge of the behavior of the above parameters would facilitate the design of an efficient immunosensor. While the contributions of the transport and reaction parameters toward understanding of the mechanism involved in capture have been well studied in the literature, their effect in combination with the geometry of the sensors has not been explored until now. In this work, we have experimentally demonstrated that the capture efficiency of the antigen-antibody systems is inversely related to the size of the sensor patch. The experimental system was simulated in order to get an in-depth understanding of the mechanism behind the experimental observation. Further, the extent of heterogeneity in the system was analyzed using the Sips isotherm to obtain the heterogeneity index (α) and the reaction rate constant (K(D)) as fitted parameters for a sensor patch of 1.5 mm radius. The experimental kinetic data obtained for the same sensor patch matched reasonably with the simulation results by considering K(D) as the global affinity constant, which indicated that our system can be considered to be homogeneous. Our simulation results associated with the size dependency of the capture efficiency were in agreement with the trends obtained in our experimental observations where an inverse relation was observed owing to the fact that the mass-transfer limitation decreases with the decrease in the size of the sensor patch. The possible underlying mechanism associated with size dependency of capture efficiency was discussed based on the time-dependent radial variation of captured antigens obtained from our simulation results. A study on the parametric variation was further conducted

  7. Microwave Oscillators Based on Nonlinear WGM Resonators

    NASA Technical Reports Server (NTRS)

    Maleki, Lute; Matsko, Andrey; Savchenkov, Anatoliy; Strekalov, Dmitry

    2006-01-01

    Optical oscillators that exploit resonantly enhanced four-wave mixing in nonlinear whispering-gallery-mode (WGM) resonators are under investigation for potential utility as low-power, ultra-miniature sources of stable, spectrally pure microwave signals. There are numerous potential uses for such oscillators in radar systems, communication systems, and scientific instrumentation. The resonator in an oscillator of this type is made of a crystalline material that exhibits cubic Kerr nonlinearity, which supports the four-photon parametric process also known as four-wave mixing. The oscillator can be characterized as all-optical in the sense that the entire process of generation of the microwave signal takes place within the WGM resonator. The resonantly enhanced four-wave mixing yields coherent, phase-modulated optical signals at frequencies governed by the resonator structure. The frequency of the phase-modulation signal, which is in the microwave range, equals the difference between the frequencies of the optical signals; hence, this frequency is also governed by the resonator structure. Hence, further, the microwave signal is stable and can be used as a reference signal. The figure schematically depicts the apparatus used in a proof-of-principle experiment. Linearly polarized pump light was generated by an yttrium aluminum garnet laser at a wavelength of 1.32 microns. By use of a 90:10 fiber-optic splitter and optical fibers, some of the laser light was sent into a delay line and some was transmitted to one face of glass coupling prism, that, in turn, coupled the laser light into a crystalline CaF2 WGM disk resonator that had a resonance quality factor (Q) of 6x10(exp 9). The output light of the resonator was collected via another face of the coupling prism and a single-mode optical fiber, which transmitted the light to a 50:50 fiber-optic splitter. One output of this splitter was sent to a slow photodiode to obtain a DC signal for locking the laser to a particular

  8. Electrical Characterization of a Thiol SAM on Gold as a First Step for the Fabrication of Immunosensors based on a Quartz Crystal Microbalance

    PubMed Central

    Tlili, Asma; Abdelghani, Adnane; Hleli, Salwa; Maaref, Mhamed A.

    2004-01-01

    In order to develop a robust biosensor based on quartz crystal microbalance technique for antigen detection, a control of the steps of the surface functionalization has been performed by impedance spectroscopy. The gold electrode is functionalized with the self-assembled monolayer technique. The high insulating properties of the acidic thiol monolayer has been characterized with cyclic voltammetry and impedance spectroscopy. The modified surface is activated with N-hydroxysuccinimide(NHS) and 1-(3-(dimethylamino)propyl)-3-ethylcarbodimide hydrochloride(EDC) cross-linker for antibody coupling. The non-specific sites are blocked with bovin serum albumine molecules. Different concentrations of antigen can be detected with a good reversibility in real time with the quartz crystal microbalance.

  9. Resonant microphone based on laser beam deflection

    NASA Astrophysics Data System (ADS)

    Roark, Kevin; Diebold, Gerald J.

    2004-07-01

    A microphone consisting of a flexible membrane coupled to a Helmholtz resonator can be constructed to have a resonance at a specific frequency making it, unlike conventional broadband microphones, a frequency selective detector of sound. The present device uses a laser beam reflected from the membrane and directed onto a split photodiode to record the motion of the membrane. Since the microphone has a lightly damped resonance, both the thermal noise fluctuations in the displacement of the membrane from its equilibrium position and the response of the microphone to sound at the resonance frequency are large. The large amplitude of both the signal and the noise fluctuations means that effect of amplifier noise on the microphone's sensitivity is diminished relative to that in broadband microphones. Applications of the microphone include photoacoustic detection of gases employing low power lasers.

  10. Tunable triple Fano resonances based on multimode interference in coupled plasmonic resonator system.

    PubMed

    Li, Shilei; Zhang, Yunyun; Song, Xiaokang; Wang, Yilin; Yu, Li

    2016-07-11

    In this paper, an asymmetric plasmonic structure composed of two MIM (metal-insulator-metal) waveguides and two rectangular cavities is reported, which can support triple Fano resonances originating from three different mechanisms. And the multimode interference coupled mode theory (MICMT) including coupling phases is proposed based on single mode coupled mode theory (CMT), which is used for describing and explaining the multiple Fano resonance phenomenon in coupled plasmonic resonator systems. Just because the triple Fano resonances originate from three different mechanisms, each Fano resonance can be tuned independently or semi-independently by changing the parameters of the two rectangular cavities. Such, a narrow 'M' type of double Lorentzian-like line-shape transmission windows with the position and the full width at half maximum (FWHM) can be tuned freely is constructed by changing the parameters of the two cavities appropriately, which can find widely applications in sensors, nonlinear and slow-light devices. PMID:27410811

  11. Immunosensor with Fluid Control Mechanism for Salivary Cortisol Analysis

    PubMed Central

    Yamaguchi, Masaki; Matsuda, Yohei; Sasaki, Shohei; Sasaki, Makoto; Kadoma, Yoshihiro; Imai, Yoshikatsu; Niwa, Daisuke; Shetty, Vivek

    2012-01-01

    The purpose of this research is to demonstrate a new design for a cortisol immunosensor for the noninvasive and quantitative analysis of salivary cortisol. We propose a cortisol immunosensor with a fluid control mechanism which has both a vertical flow and a lateral flow. The detected current resulting from a competitive reaction between the sample cortisol and a glucose oxidase (GOD)-labeled cortisol conjugate was found to be inversely related to the concentration of cortisol in the sample solution. A calibration curve using the relative detected current showed an R2 = 0.98 and CV = 14% for a range of standard cortisol solutions corresponding to the concentrations of native salivary cortisol (0.1 – 10 ng/ml). The measurement could be accomplished within 35 minutes and the cortisol immunosensor could be reused. These results show promise for realizing an on-site and easy-to-use biosensor for cortisol. Used for evaluation of human salivary cortisol levels, the cortisol immunosensor measurement corresponded closely with commercially available ELISA method (R2 = 0.92). Our results indicate the promise of the new cortisol immunosensor for noninvasive, point-of care measurement of human salivary cortisol levels. PMID:22939507

  12. Final Technical Report - In-line Uranium Immunosensor

    SciTech Connect

    Blake, Diane A.

    2006-07-05

    In this project, personnel at Tulane University and Sapidyne Instruments Inc. developed an in-line uranium immunosensor that could be used to determine the efficacy of specific in situ biostimulation approaches. This sensor was designed to operate autonomously over relatively long periods of time (2-10 days) and was able to provide near real-time data about uranium immobilization in the absence of personnel at the site of the biostimulation experiments. An alpha prototype of the in-line immmunosensor was delivered from Sapidyne Instruments to Tulane University in December of 2002 and a beta prototype was delivered in November of 2003. The beta prototype of this instrument (now available commercially from Sapidyne Instruments) was programmed to autonomously dilute standard uranium to final concentrations of 2.5 to 100 nM (0.6 to 24 ppb) in buffer containing a fluorescently labeled anti-uranium antibody and the uranium chelator, 2,9-dicarboxyl-1,10-phenanthroline. The assay limit of detection for hexavalent uranium was 5.8 nM or 1.38 ppb. This limit of detection is well below the drinking water standard of 30 ppb recently promulgated by the EPA. The assay showed excellent precision; the coefficients of variation (CV’s) in the linear range of the assay were less than 5% and CV’s never rose above 14%. Analytical recovery in the immunosensors-based assay was assessed by adding variable known quantities of uranium to purified water samples. A quantitative recovery (93.75% - 108.17%) was obtained for sample with concentrations from 7.5 to 20 nM (2-4.75 ppb). In August of 2005 the sensor was transported to Oak Ridge National Laboratory, for testing of water samples at the Criddle test site (see Wu et al., Environ. Sci. Technol. 40:3978-3985 2006 for a description of this site). In this first on-site test, the in-line sensor was able to accurately detect changes in the concentrations of uranium in effluent samples from this site. Although the absolute values for the

  13. Piezoelectric resonators based on self-assembled diphenylalanine microtubes

    NASA Astrophysics Data System (ADS)

    Bosne, E. D.; Heredia, A.; Kopyl, S.; Karpinsky, D. V.; Pinto, A. G.; Kholkin, A. L.

    2013-02-01

    Piezoelectric actuation has been widely used in microelectromechanical devices including resonance-based biosensors, mass detectors, resonators, etc. These were mainly produced by micromachining of Si and deposited inorganic piezoelectrics based on metal oxides or perovskite-type materials which have to be further functionalized in order to be used in biological applications. In this work, we demonstrate piezoelectrically driven micromechanical resonators based on individual self-assembled diphenylalanine microtubes with strong intrinsic piezoelectric effect. Tubes of different diameters and lengths were grown from the solution and assembled on a rigid support. The conducting tip of the commercial atomic force microscope was then used to both excite vibrations and study resonance behavior. Efficient piezoelectric actuation at the fundamental resonance frequency ≈2.7 MHz was achieved with a quality factor of 114 for a microtube of 277 μm long. A possibility of using piezoelectric dipeptides for biosensor applications is discussed.

  14. Analysis of an integrated optic micro racetrack resonator based biosensor

    NASA Astrophysics Data System (ADS)

    Malathi, S.; Hegde, Gopalkrishna; Srinivas, T.; Roy, Ugra M.

    2014-06-01

    Silicon-On- Insulator (SOI) technology has huge potential in fabricating compact devices for various applications such as integrated optic waveguides, directional couplers, resonators etc. In this work, we present the analysis of a biosensor based on an integrated optic racetrack resonator, interrogated by a bus waveguide. The biomaterial is applied as a cladding layer. Here we analyze the coupling between the resonator and the bus waveguide, and its dependence on the bio layer. In traditional analysis, the effective refractive index and resonator total path length are the factors influencing the resonant wavelength. Our analysis shows that all parametric values decrease with increase in waveguide width and spacing. The inclusion of waveguide mode overlap and perturbation in coupled mode equation results in enhanced resonator sensitivity of an order of magnitude

  15. Graphene-based waveguide resonators for submillimeter-wave applications

    NASA Astrophysics Data System (ADS)

    Ilić, Andjelija Ž.; Bukvić, Branko; Ilić, Milan M.; Budimir, Djuradj

    2016-08-01

    Utilization of graphene covered waveguide inserts to form tunable waveguide resonators is theoretically explained and rigorously investigated by means of full-wave numerical electromagnetic simulations. Instead of using graphene-based switching elements, the concept we propose incorporates graphene sheets as parts of a resonator. Electrostatic tuning of the graphene surface conductivity leads to changes in the electromagnetic field boundary conditions at the resonator edges and surfaces, thus producing an effect similar to varying the electrical length of a resonator. The presented outline of the theoretical background serves to give phenomenological insight into the resonator behavior, but it can also be used to develop customized software tools for design and optimization of graphene-based resonators and filters. Due to the linear dependence of the imaginary part of the graphene surface impedance on frequency, the proposed concept was expected to become effective for frequencies above 100 GHz, which is confirmed by the numerical simulations. A frequency range from 100 GHz up to 1100 GHz, where the rectangular waveguides are used, is considered. Simple, all-graphene-based resonators are analyzed first, to assess the achievable tunability and to check the performance throughout the considered frequency range. Graphene–metal combined waveguide resonators are proposed in order to preserve the excellent quality factors typical for the type of waveguide discontinuities used. Dependence of resonator properties on key design parameters is studied in detail. Dependence of resonator properties throughout the frequency range of interest is studied using eight different waveguide sections appropriate for different frequency intervals. Proposed resonators are aimed at applications in the submillimeter-wave spectral region, serving as the compact tunable components for the design of bandpass filters and other devices.

  16. An ultra-sensitive impedimetric immunosensor for detection of the serum oncomarker CA-125 in ovarian cancer patients

    NASA Astrophysics Data System (ADS)

    Johari-Ahar, M.; Rashidi, M. R.; Barar, J.; Aghaie, M.; Mohammadnejad, D.; Ramazani, A.; Karami, P.; Coukos, G.; Omidi, Y.

    2015-02-01

    Effective treatment of ovarian cancer depends upon the early detection of the malignancy. Here, we report on the development of a new nanostructured immunosensor for early detection of cancer antigen 125 (CA-125). A gold electrode was modified with mercaptopropionic acid (MPA), and then consecutively conjugated with silica coated gold nanoparticles (AuNP@SiO2), CdSe quantum dots (QDs) and anti-CA-125 monoclonal antibody (mAb). The engineered MPA|AuNP@SiO2|QD|mAb immunosensor was characterised using transmission electron microscopy (TEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Successive conjugation of AuNP@SiO2, CdSe QD and anti-CA-125 mAb onto the gold electrode resulted in sensitive detection of CA-125 with a limit of detection (LOD) of 0.0016 U mL-1 and a linear detection range (LDR) of 0-0.1 U mL-1. Based on the high sensitivity and specificity of the immunosensor, we propose this highly stable and reproducible biosensor for the early detection of CA-125.Effective treatment of ovarian cancer depends upon the early detection of the malignancy. Here, we report on the development of a new nanostructured immunosensor for early detection of cancer antigen 125 (CA-125). A gold electrode was modified with mercaptopropionic acid (MPA), and then consecutively conjugated with silica coated gold nanoparticles (AuNP@SiO2), CdSe quantum dots (QDs) and anti-CA-125 monoclonal antibody (mAb). The engineered MPA|AuNP@SiO2|QD|mAb immunosensor was characterised using transmission electron microscopy (TEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Successive conjugation of AuNP@SiO2, CdSe QD and anti-CA-125 mAb onto the gold electrode resulted in sensitive detection of CA-125 with a limit of detection (LOD) of 0.0016 U mL-1 and a linear detection range (LDR) of 0-0.1 U mL-1. Based on the high sensitivity and specificity of the immunosensor, we propose

  17. Fluorescence resonance energy transfer based immunosensing of human IgG by using quantum dot/GIgG-gold nanoparticles/IgG conjugation.

    PubMed

    Luo, Lin; Liu, Zhao; Li, Jianjun; Zhu, Jian

    2014-06-01

    A novel immunosensor of human immune globulin (IgG) was fabricated based on the fluorescence transfer between luminescent semiconductor quantum dots (QDs) and gold nanoparticles (AuNPs). AuNPs and CdSe/ZnS QDs were respectively labeled with immune reaction pair:IgG and goat anti-human immunoglobulin (GIgG), by optimizing the conditions including pH value and protein amount. In the assembled QD-GIgG-IgG-AuNP fluorescence resonance energy transfer (FRET) immunocomplex system, the presence of AuNP-IgG directly reduced the fluorescence intensity of the GIgG conjugated QDs. As a result, the concentration of AuNP-IgG had a linear relationship with the fluorescence decrease in a range of 0-1.57 microg/mL. Furthermore, the mechanism of the QDs' fluorescence decay has also been discussed and attributed to the light-induced photobleaching. This novel sensing method achieves quantitative detection of trace proteins, suggesting the potential of biomolecule-AuNPs conjugation based analytical methods in further application. PMID:24738348

  18. Flow immunosensor detection of explosives and drugs of abuse

    NASA Astrophysics Data System (ADS)

    Kusterbeck, Anne W.; Judd, Linda L.; Yu, Hao; Myles, June; Ligler, Frances S.

    1994-03-01

    An antibody-based biosensor has been developed at the Naval Research Laboratory which is capable of detecting both drugs and explosives present at low levels in an aqueous sample. In the flow immunosensor, antibodies are immobilized onto a solid substrate, allowed to bind a fluorescently labeled signal molecule, placed in a small column and attached to a buffer flow. Upon sample introduction, an amount of the fluorescent signal molecule is released that is proportional to the concentration of applied sample. The response time of the sensor is under a minute, and multiple samples can be analyzed without the need for additional reagents. Quantitative assays are being developed for a variety of compounds, including TNT, DNT, PETN, and cocaine. The laboratory prototype has been used to study how choice of fluorophore, antibody density, and flow rate affect the signal intensity and column lifetime. A self-contained commercial instrument which can analyze up to seven different compounds from a single sample is currently being engineered under a Cooperative Research and Development Agreement.

  19. Low density lipoprotein detection based on antibody immobilized self-assembled monolayer: investigations of kinetic and thermodynamic properties.

    PubMed

    Matharu, Zimple; Bandodkar, Amay Jairaj; Sumana, G; Solanki, Pratima R; Ekanayake, E M I Mala; Kaneto, Keiichi; Gupta, Vinay; Malhotra, B D

    2009-10-29

    Human plasma low density lipoprotein (LDL) immunosensor based on surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) was fabricated by immobilizing antiapolipoprotein B (AAB) onto self-assembled monolayer (SAM) of 4-aminothiophenol (ATP). The AAB/ATP/Au immunosensor can detect LDL up to 0.252 microM (84 mg/dL) and 0.360 microM (120 mg/dL) with QCM and SPR, respectively. The SPR and QCM measurements were further utilized to study the reaction kinetics of the AAB-LDL interaction. The adsorption process involved was explored using Langmuir adsorption isotherm and Freundlich adsorption models. The thermodynamic parameters such as change in Gibb's free energy (DeltaG(ads)), change in enthalpy (DeltaH(ads)), and change in entropy (DeltaS(ads)) determined at 283, 298, and 308 K revealed that the AAB-LDL interaction is endothermic in nature and is governed by entropy. Kinetic, thermodynamic, and sticking probability studies disclosed that desorption of the water molecules from the active sites of AAB and LDL plays a key role in the interaction process and increase in temperature favors binding of LDL with the AAB/ATP/Au immunosensor. Thus, the studies were utilized to unravel the most important subprocess involved in the adsorption of LDL onto AAB-modified ATP/Au surface that may help in the fabrication of LDL immunosensors with better efficiency. PMID:19810739

  20. Plasmomechanical Resonators Based on Dimer Nanoantennas.

    PubMed

    Thijssen, Rutger; Kippenberg, Tobias J; Polman, Albert; Verhagen, Ewold

    2015-06-10

    Nanomechanical resonators are highly suitable as sensors of minute forces, displacements, or masses. We realize a single plasmonic dimer antenna of subwavelength size, integrated with silicon nitride nanobeams. The sensitive dependence of the antenna response on the beam displacement creates a plasmomechanical system of deeply subwavelength size in all dimensions. We use it to demonstrate transduction of thermal vibrations to scattered light fields and discuss the noise properties and achievable coupling strengths in these systems. PMID:25938170

  1. Detection of hexavalent uranium with inline and field-portable immunosensors

    SciTech Connect

    Melton, Scott J.; Yu, Haini; Ali, Mehnaaz F.; Williams, Kenneth H; Wilkins, Michael J.; Long, Philip E.; Blake, Diane A.

    2008-10-02

    An antibody that recognizes a chelated form of hexavalent uranium was used in the development of two different immunosensors for uranium detection. Specifically, these sensors were utilized for the analysis of groundwater samples collected during a 2007 field study of in situ bioremediation in a aquifer located at Rifle, CO. The antibody-based sensors provided data comparable to that obtained using Kinetic Phosphorescence Analysis (KPA). Thus, these novel instruments and associated reagents should provide field researchers and resource managers with valuable new tools for on-site data acquisition.

  2. Quantify Resonance Inspection with Finite Element-Based Modal Analyses

    SciTech Connect

    Lai, Canhai; Sun, Xin; Dasch, Cameron; Harmon, George; Jones, Martin

    2011-06-01

    Resonance inspection uses the natural acoustic resonances of a part to identify anomalous parts. Modern instrumentation can measure the many resonant frequencies rapidly and accurately. Sophisticated sorting algorithms trained on sets of good and anomalous parts can rapidly and reliably inspect and sort parts. This paper aims at using finite-element-based modal analysis to put resonance inspection on a more quantitative basis. A production-level automotive steering knuckle is used as the example part for our study. First, the resonance frequency spectra for the knuckle are measured with two different experimental techniques. Next, scanning laser vibrometry is used to determine the mode shape corresponding to each resonance. The material properties including anisotropy are next measured to high accuracy using resonance spectroscopy on cuboids cut from the part. Then, finite element model (FEM) of the knuckle is generated by meshing the actual part geometry obtained with computed tomography (CT). The resonance frequencies and mode shapes are next predicted with a natural frequency extraction analysis after extensive mesh size sensitivity study. The good comparison between the predicted and the experimentally measured resonance spectra indicate that finite-element-based modal analyses have the potential to be a powerful tool in shortening the training process and improving the accuracy of the resonance inspection process for a complex, production level part. The finite element based analysis can also provide a means to computationally test the sensitivity of the frequencies to various possible defects such as porosity or oxide inclusions especially in the high stress regions that the part will experience in service.

  3. Quantify Resonance Inspection with Finite Element-Based Modal Analyses

    SciTech Connect

    Sun, Xin; Lai, Canhai; Dasch, Cameron

    2010-11-10

    Resonance inspection uses the natural acoustic resonances of a part to identify anomalous parts. Modern instrumentation can measure the many resonant frequencies rapidly and accurately. Sophisticated sorting algorithms trained on sets of good and anomalous parts can rapidly and reliably inspect and sort parts. This paper aims at using finite-element-based modal analysis to put resonance inspection on a more quantitative basis. A production-level automotive steering knuckle is used as the example part for our study. First, the resonance frequency spectra for the knuckle are measured with two different experimental techniques. Next, scanning laser vibrometry is used to determine the mode shape corresponding to each resonance. The material properties including anisotropy are next measured to high accuracy using resonance spectroscopy on cuboids cut from the part. Then, finite element model (FEM) of the knuckle is generated by meshing the actual part geometry obtained with computed tomography (CT). The resonance frequencies and mode shapes are next predicted with a natural frequency extraction analysis after extensive mesh size sensitivity study. The good comparison between the predicted and the experimentally measured resonance spectra indicate that finite-element-based modal analyses have the potential to be a powerful tool in shortening the training process and improving the accuracy of the resonance inspection process for a complex, production level part. The finite element based analysis can also provide a means to computationally test the sensitivity of the frequencies to various possible defects such as porosity or oxide inclusions especially in the high stress regions that the part will experience in service.

  4. Fe3O4NPs mediated nonenzymatic electrochemical immunosensor for the total protein of Nosema bombycis detection without addition of substrate.

    PubMed

    Xie, Hua; Zhang, Qiqi; Wang, Qin; Chai, Yaqin; Yuan, Yali; Yuan, Ruo

    2015-04-28

    In this work, we proposed a novel electrochemical immunosensor for sensitive detection of the total protein of Nosema bombycis based on Fe3O4 nanoparticles (Fe3O4NPs) as catalyst to electrocatalyze the reduction of methylene blue (MB) with the aid of Fe3O4NPs-DNA dendrimers for the signal amplification. PMID:25806964

  5. Engineering electromagnetic responses of bilayered metamaterials based on Fano resonances

    NASA Astrophysics Data System (ADS)

    Shi, Jinhui; Liu, Ran; Na, Bo; Xu, Yiqun; Zhu, Zheng; Wang, Yuekun; Ma, Huifeng; Cui, Tiejun

    2013-08-01

    We numerically and experimentally demonstrate engineered electromagnetic responses from a single-peak Fano resonance to a fast roll-off behavior by using planar metamaterials, which are constructed by bilayered asymmetrically split rings (ASRs) with twist angles of 0° and 180°. Since each single-layer ASR metamaterial reveals a Fano-type resonance, the dramatic transmission properties are resulted from the hybridization of electromagnetic resonances due to the near-field coupling between two Fano resonances and the far-field retardation effect of the bilayered metamaterials. The surface currents and charges distributions provide an insight into deep understanding of in-phase and out-of-phase coupling of two Fano resonances. The measured and simulated results of bilayered metamaterials agree well to each other. Especially, the proposed metamaterials can be exploited to design metamaterial-based devices in the THz and optical ranges like filters and sensors.

  6. A self-amplified transistor immunosensor under dual gate operation: highly sensitive detection of hepatitis B surface antigen

    NASA Astrophysics Data System (ADS)

    Lee, I.-K.; Jeun, M.; Jang, H.-J.; Cho, W.-J.; Lee, K. H.

    2015-10-01

    Ion-sensitive field-effect transistors (ISFETs), although they have attracted considerable attention as effective immunosensors, have still not been adopted for practical applications owing to several problems: (1) the poor sensitivity caused by the short Debye screening length in media with high ion concentration, (2) time-consuming preconditioning processes for achieving the highly-diluted media, and (3) the low durability caused by undesirable ions such as sodium chloride in the media. Here, we propose a highly sensitive immunosensor based on a self-amplified transistor under dual gate operation (immuno-DG ISFET) for the detection of hepatitis B surface antigen. To address the challenges in current ISFET-based immunosensors, we have enhanced the sensitivity of an immunosensor by precisely tailoring the nanostructure of the transistor. In the pH sensing test, the immuno-DG ISFET showed superior sensitivity (2085.53 mV per pH) to both standard ISFET under single gate operation (58.88 mV per pH) and DG ISFET with a non-tailored transistor (381.14 mV per pH). Moreover, concerning the detection of hepatitis B surface antigens (HBsAg) using the immuno-DG ISFET, we have successfully detected trace amounts of HBsAg (22.5 fg mL-1) in a non-diluted 1× PBS medium with a high sensitivity of 690 mV. Our results demonstrate that the proposed immuno-DG ISFET can be a biosensor platform for practical use in the diagnosis of various diseases.Ion-sensitive field-effect transistors (ISFETs), although they have attracted considerable attention as effective immunosensors, have still not been adopted for practical applications owing to several problems: (1) the poor sensitivity caused by the short Debye screening length in media with high ion concentration, (2) time-consuming preconditioning processes for achieving the highly-diluted media, and (3) the low durability caused by undesirable ions such as sodium chloride in the media. Here, we propose a highly sensitive immunosensor

  7. Label free sensing of creatinine using a 6 GHz CMOS near-field dielectric immunosensor.

    PubMed

    Guha, S; Warsinke, A; Tientcheu, Ch M; Schmalz, K; Meliani, C; Wenger, Ch

    2015-05-01

    In this work we present a CMOS high frequency direct immunosensor operating at 6 GHz (C-band) for label free determination of creatinine. The sensor is fabricated in standard 0.13 μm SiGe:C BiCMOS process. The report also demonstrates the ability to immobilize creatinine molecules on a Si3N4 passivation layer of the standard BiCMOS/CMOS process, therefore, evading any further need of cumbersome post processing of the fabricated sensor chip. The sensor is based on capacitive detection of the amount of non-creatinine bound antibodies binding to an immobilized creatinine layer on the passivated sensor. The chip bound antibody amount in turn corresponds indirectly to the creatinine concentration used in the incubation phase. The determination of creatinine in the concentration range of 0.88-880 μM is successfully demonstrated in this work. A sensitivity of 35 MHz/10 fold increase in creatinine concentration (during incubation) at the centre frequency of 6 GHz is gained by the immunosensor. The results are compared with a standard optical measurement technique and the dynamic range and sensitivity is of the order of the established optical indication technique. The C-band immunosensor chip comprising an area of 0.3 mm(2) reduces the sensing area considerably, therefore, requiring a sample volume as low as 2 μl. The small analyte sample volume and label free approach also reduce the experimental costs in addition to the low fabrication costs offered by the batch fabrication technique of CMOS/BiCMOS process. PMID:25782697

  8. High Quality Factor Mechanical Resonators Based on WSe2 Monolayers.

    PubMed

    Morell, Nicolas; Reserbat-Plantey, Antoine; Tsioutsios, Ioannis; Schädler, Kevin G; Dubin, François; Koppens, Frank H L; Bachtold, Adrian

    2016-08-10

    Suspended monolayer transition metal dichalcogenides (TMD) are membranes that combine ultralow mass and exceptional optical properties, making them intriguing materials for opto-mechanical applications. However, the low measured quality factor of TMD resonators has been a roadblock so far. Here, we report an ultrasensitive optical readout of monolayer TMD resonators that allows us to reveal their mechanical properties at cryogenic temperatures. We find that the quality factor of monolayer WSe2 resonators greatly increases below room temperature, reaching values as high as 1.6 × 10(4) at liquid nitrogen temperature and 4.7 × 10(4) at liquid helium temperature. This surpasses the quality factor of monolayer graphene resonators with similar surface areas. Upon cooling the resonator, the resonant frequency increases significantly due to the thermal contraction of the WSe2 lattice. These measurements allow us to experimentally study the thermal expansion coefficient of WSe2 monolayers for the first time. High Q-factors are also found in resonators based on MoS2 and MoSe2 monolayers. The high quality-factor found in this work opens new possibilities for coupling mechanical vibrational states to two-dimensional excitons, valley pseudospins, and single quantum emitters and for quantum opto-mechanical experiments based on the Casimir interaction. PMID:27459399

  9. Dual band metamaterial perfect absorber based on Mie resonances

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoming; Lan, Chuwen; Bi, Ke; Li, Bo; Zhao, Qian; Zhou, Ji

    2016-08-01

    We numerically and experimentally demonstrated a polarization insensitive dual-band metamaterial perfect absorber working in wide incident angles based on the two magnetic Mie resonances of a single dielectric "atom" with simple structure. Two absorption bands with simulated absorptivity of 99% and 96%, experimental absorptivity of 97% and 94% at 8.45 and 11.97 GHz were achieved due to the simultaneous magnetic and electric resonances in dielectric "atom" and copper plate. Mie resonances of dielectric "atom" provide a simple way to design metamaterial perfect absorbers with high symmetry.

  10. Ring resonator based narrow-linewidth semiconductor lasers

    NASA Technical Reports Server (NTRS)

    Ksendzov, Alexander (Inventor)

    2005-01-01

    The present invention is a method and apparatus for using ring resonators to produce narrow linewidth hybrid semiconductor lasers. According to one embodiment of the present invention, the narrow linewidths are produced by combining the semiconductor gain chip with a narrow pass band external feedback element. The semi conductor laser is produced using a ring resonator which, combined with a Bragg grating, acts as the external feedback element. According to another embodiment of the present invention, the proposed integrated optics ring resonator is based on plasma enhanced chemical vapor deposition (PECVD) SiO.sub.2 /SiON/SiO.sub.2 waveguide technology.

  11. Acoustic superlens using Helmholtz-resonator-based metamaterials

    SciTech Connect

    Yang, Xishan; Yin, Jing; Yu, Gaokun Peng, Linhui; Wang, Ning

    2015-11-09

    Acoustic superlens provides a way to overcome the diffraction limit with respect to the wavelength of the bulk wave in air. However, the operating frequency range of subwavelength imaging is quite narrow. Here, an acoustic superlens is designed using Helmholtz-resonator-based metamaterials to broaden the bandwidth of super-resolution. An experiment is carried out to verify subwavelength imaging of double slits, the imaging of which can be well resolved in the frequency range from 570 to 650 Hz. Different from previous works based on the Fabry-Pérot resonance, the corresponding mechanism of subwavelength imaging is the Fano resonance, and the strong coupling between the neighbouring Helmholtz resonators separated at the subwavelength interval leads to the enhanced sound transmission over a relatively wide frequency range.

  12. A novel electrochemical immunosensor for highly sensitive detection of aflatoxin B1 in corn using single-walled carbon nanotubes/chitosan.

    PubMed

    Zhang, Xian; Li, Chao-Rui; Wang, Wei-Cheng; Xue, Jian; Huang, Ya-Ling; Yang, Xian-Xian; Tan, Bin; Zhou, Xi-Peng; Shao, Chuang; Ding, Shi-Jia; Qiu, Jing-Fu

    2016-02-01

    A sensitive electrochemical immunosensor for aflatoxin B1 (AFB1) detection based on single-walled carbon nanotubes/chitosan was presented. The immunosensor was based on an indirect competitive binding to a fixed amount of anti-AFB1 between free AFB1 and AFB1-bovine serum albumin, which conjugate immobilized on covalently functionalized nanotubes/chitosan laid on the glass carbon electrode. Then, the anti-mouse immunoglobulin G secondary antibody labeled with alkaline phosphatase was bound to the electrode surface through reacting with primary antibody. Finally, alkaline phosphatase catalyzes the hydrolysis of the substrate α-naphthyl phosphate, which produced electrochemical signal. Compared with conventional methods, the established immunosensor was more sensitive and simple. Under optimal conditions, this method could quantitatively detect AFB1 from 0.01 to 100 ng mL(-1) with a detection limit of 3.5 pg mL(-1). Moreover, the immunosensor was successfully applied to assay AFB1 in corn powder, which showed good correlation with the results obtained from high performance liquid chromatography. PMID:26304338

  13. Glyphosate immunosensor. Application for water and soil analysis.

    PubMed

    González-Martínez, Miguel Angel; Brun, Eva María; Puchades, Rosa; Maquieira, Angel; Ramsey, Kristy; Rubio, Fernando

    2005-07-01

    A fully automated immunosensor for the herbicide glyphosate has been developed on the basis of the immunocomplex capture assay protocol. The sensor carries out on-line analyte derivatization prior to the assay and uses a selective anti-glyphosate serum, a glyphosate peroxidase enzyme tracer, and fluorescent detection. Under optimal conditions, the detection limit achieved is 0.021 microg/L with an analysis rate of 25 min per assay, autonomy of more than 48 h, and sensor reusability >500 analytical cycles. The immunosensor is able to discriminate structurally related molecules, such as aminomethylphosphonic acid, the main metabolite of glyphosate, and other related herbicides, such as glufosinate and glyphosine. Interferences from naturally occurring species (anions, cations, and humic substances) and their elimination were also studied. The immunosensor has been successfully applied to water and soil sample analysis, with good recoveries at levels lower than 1 microg/L. Results obtained with the immunosensor correlate well with data from a magnetic particle ELISA and LC/LC/MS chromatographic method. PMID:15987130

  14. A novel photoelectrochemical immunosensor by integration of nanobody and TiO₂ nanotubes for sensitive detection of serum cystatin C.

    PubMed

    Mi, Li; Wang, Pingyan; Yan, Junrong; Qian, Jing; Lu, Jusheng; Yu, Jiachao; Wang, Yuzhen; Liu, Hong; Zhu, Min; Wan, Yakun; Liu, Songqin

    2016-01-01

    Cystatin C (CysC) is a sensitive marker for the estimation of the glomerular filtration rate and the clinical diagnosis of different diseases. In this paper, CysC-specific nanobodies (Nbs) were isolated from a phage display nanobody library. A simple and sensitive photoelectrochemical immunosensor based on TiO2 nanotube arrays (TNAs) was proposed for the sensitive detection of CysC. The TiO2 nanotube arrays deposited by electrochemical anodization displayed a high and stable photocurrent response under irradiation. After coupling CysC-specific nanobody to TNA (Nb/TNA), the proposed immunosensor for CysC can be utilized for tracking the photocurrent change of Nb/TNA caused by immunoreactions between CysC and the immobilized CysC-specific Nb. This allowed for the determination of CysC with a calibration range from 0.72 pM to 7.19 nM. The variation of the photocurrent was in a linear relationship with the logarithm of the CysC concentration in the range of 0.72 pM-3.6 nM. The immunosensor had a correlation coefficient of 0.97 and a detection limit of 0.14 pM at a signal-to-noise ratio of 3. The proposed immunosensor showed satisfactory intra- and inter-assay accuracy, high selectivity and good stability. As a result, this proposed strategy would offer a novel and simple approach for the detection of immunoreactions, provide new insights in popularizing the diagnosis of CysC, and extend the application of TiO2 nanotubes. PMID:26703259

  15. Reliable and integrated technique for determining resonant frequency in radio frequency resonators. Application to a high-precision resonant cavity-based displacement sensor

    NASA Astrophysics Data System (ADS)

    Jauregui, Rigoberto; Asua, Estibaliz; Portilla, Joaquin; Etxebarria, Victor

    2015-03-01

    This paper presents a reliable and integrated technique for determining the resonant frequency of radio frequency resonators, which can be of interest for different purposes. The approach uses a heterodyne scheme as phase detector coupled to a voltage-controlled oscillator. The system seeks the oscillator frequency that produces a phase null in the resonator, which corresponds to the resonant frequency. A complete explanation of the technique to determine the resonant frequency is presented and experimentally tested. The method has been applied to a high-precision displacement sensor based on resonant cavity, obtaining a theoretical nanometric precision.

  16. Realization of a label-free electrochemical immunosensor for detection of low density lipoprotein using NiO thin film.

    PubMed

    Kaur, Gurpreet; Tomar, Monika; Gupta, Vinay

    2016-06-15

    A label-free electrochemical immunosensor, based on nickel oxide (NiO) thin film, for the detection of low density lipoprotein (LDL) has been proposed. P-type semiconducting NiO thin film was deposited by RF sputtering technique and its properties were investigated by X-ray diffraction and Fourier transform infrared spectroscopy. The NiO thin film was utilized as an efficient matrix for the covalent immobilization of apolipoprotein B-100 antibody using EDC/NHS chemistry. The immunoelectrode, thus prepared, was studied using differential pulse voltammetry, cyclic voltammetry and electrochemical impedance spectroscopy. The impedimetric response of the immunosensor exhibited a high sensitivity of 12 kΩ μM(-1) over a wide linear range (0.018-0.5 μM) of LDL. The long shelf life (18 weeks) and enhanced performance characteristics of the immunosensor demonstrate the excellent ability of the NiO matrix for quantification of LDL at commercial level. PMID:26852197

  17. An ultra-sensitive impedimetric immunosensor for detection of the serum oncomarker CA-125 in ovarian cancer patients.

    PubMed

    Johari-Ahar, M; Rashidi, M R; Barar, J; Aghaie, M; Mohammadnejad, D; Ramazani, A; Karami, P; Coukos, G; Omidi, Y

    2015-02-28

    Effective treatment of ovarian cancer depends upon the early detection of the malignancy. Here, we report on the development of a new nanostructured immunosensor for early detection of cancer antigen 125 (CA-125). A gold electrode was modified with mercaptopropionic acid (MPA), and then consecutively conjugated with silica coated gold nanoparticles (AuNP@SiO2), CdSe quantum dots (QDs) and anti-CA-125 monoclonal antibody (mAb). The engineered MPA|AuNP@SiO2|QD|mAb immunosensor was characterised using transmission electron microscopy (TEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Successive conjugation of AuNP@SiO2, CdSe QD and anti-CA-125 mAb onto the gold electrode resulted in sensitive detection of CA-125 with a limit of detection (LOD) of 0.0016 U mL(-1) and a linear detection range (LDR) of 0-0.1 U mL(-1). Based on the high sensitivity and specificity of the immunosensor, we propose this highly stable and reproducible biosensor for the early detection of CA-125. PMID:25644549

  18. A multi-walled carbon nanotubes-poly(L-lysine) modified enantioselective immunosensor for ofloxacin by using multi-enzyme-labeled gold nanoflower as signal enhancer.

    PubMed

    He, Zuyu; Zang, Shuai; Liu, Yingju; He, Yuan; Lei, Hongtao

    2015-11-15

    The enantioselective detection of trace amounts of ofloxacin is very important in many fields. In this work, an enantioselective and sensitive electrochemical immunosensor was constructed for the detection of chiral antibiotic ofloxacin based on a dual amplification strategy using multiwall carbon nanotubes-poly(L-lysine) as a matrix to immobilize the antigen and multi-enzyme-antibody functionalized gold nanoflowers as an electrochemical detection label. The fabrication process of the dual-amplified immunosensor was characterized by scanning electron microscopy, cyclic voltammogram and electrochemical impedance spectroscopy, respectively. After the optimization of the experimental conditions, a competitive immunoassay, i.e., the association ability with the corresponding antibody between the captured antigen and free S-OFL or R-OFL in the solution, showed that the immunosensor exhibited a sensitive response to S-OFL in the range from 0.26 to 25.6 ng/mL with a detection limit of 0.15 ng/mL as well as a sensitive response to R-OFL in the range from 0.37 to 12.8 ng/mL with a detection limit of 0.30 ng/mL. Along with the acceptable sensitivity and stability, the S-OFL or R-OFL immunosensor showed selective ability to its corresponding enantiomer, suggesting this amplification strategy may hold a potential application in the detection of OFL in food or environment. PMID:26047998

  19. Scatter-based magnetic resonance elastography

    NASA Astrophysics Data System (ADS)

    Papazoglou, Sebastian; Xu, Chao; Hamhaber, Uwe; Siebert, Eberhard; Bohner, Georg; Klingebiel, Randolf; Braun, Jürgen; Sack, Ingolf

    2009-04-01

    Elasticity is a sensitive measure of the microstructural constitution of soft biological tissues and increasingly used in diagnostic imaging. Magnetic resonance elastography (MRE) uniquely allows in vivo measurement of the shear elasticity of brain tissue. However, the spatial resolution of MRE is inherently limited as the transformation of shear wave patterns into elasticity maps requires the solution of inverse problems. Therefore, an MRE method is introduced that avoids inversion and instead exploits shear wave scattering at elastic interfaces between anatomical regions of different shear compliance. This compliance-weighted imaging (CWI) method can be used to evaluate the mechanical consistency of cerebral lesions or to measure relative stiffness differences between anatomical subregions of the brain. It is demonstrated that CWI-MRE is sensitive enough to reveal significant elasticity variations within inner brain parenchyma: the caudate nucleus (head) was stiffer than the lentiform nucleus and the thalamus by factors of 1.3 ± 0.1 and 1.7 ± 0.2, respectively (P < 0.001). CWI-MRE provides a unique method for characterizing brain tissue by identifying local stiffness variations.

  20. High sensitivity optical waveguide accelerometer based on Fano resonance.

    PubMed

    Wan, Fenghua; Qian, Guang; Li, Ruozhou; Tang, Jie; Zhang, Tong

    2016-08-20

    An optical waveguide accelerometer based on tunable asymmetrical Fano resonance in a ring-resonator-coupled Mach-Zehnder interferometer (MZI) is proposed and analyzed. A Fano resonance accelerometer has a relatively large workspace of coupling coefficients with high sensitivity, which has potential application in inertial navigation, missile guidance, and attitude control of satellites. Due to the interference between a high-Q resonance pathway and a coherent background pathway, a steep asymmetric line shape is generated, which greatly improves the sensitivity of this accelerometer. The sensitivity of the accelerometer is about 111.75 mW/g. A 393-fold increase in sensitivity is achieved compared with a conventional MZI accelerometer and is approximately equal to the single ring structure. PMID:27556984

  1. Porosity estimation of alumina samples based on resonant backscattering spectrometry

    NASA Astrophysics Data System (ADS)

    Mokhles Gerami, F.; Kakuee, O.; Mohammadi, S.

    2016-04-01

    In this work, columnar porous alumina samples were investigated using the 16O(α,α)16O resonance scattering at 3.045 MeV. If the incident energy is slightly above the resonance energy, a resonance peak appears in the energy spectra of the backscattered ions. The position and width of this peak for non-porous samples are mainly determined by the experimental setup, whilst for porous materials, the peak position shifts towards higher energies under certain conditions. This effect can be explained by the lower amount of material which the ions encounter along the backscattered trajectories. The energy shift of the resonance peak towards higher energies was revealed experimentally and discussed theoretically. The estimated porosities of the samples based on this energy shift were compared with those evaluated from the graphical analysis of the images obtained by field emission scanning electron microscopy.

  2. Nanoscale devices based on plasmonic coaxial waveguide resonators

    NASA Astrophysics Data System (ADS)

    Mahigir, A.; Dastmalchi, P.; Shin, W.; Fan, S.; Veronis, G.

    2015-02-01

    Waveguide-resonator systems are particularly useful for the development of several integrated photonic devices, such as tunable filters, optical switches, channel drop filters, reflectors, and impedance matching elements. In this paper, we introduce nanoscale devices based on plasmonic coaxial waveguide resonators. In particular, we investigate threedimensional nanostructures consisting of plasmonic coaxial stub resonators side-coupled to a plasmonic coaxial waveguide. We use coaxial waveguides with square cross sections, which can be fabricated using lithography-based techniques. The waveguides are placed on top of a silicon substrate, and the space between inner and outer coaxial metals is filled with silica. We use silver as the metal. We investigate structures consisting of a single plasmonic coaxial resonator, which is terminated either in a short or an open circuit, side-coupled to a coaxial waveguide. We show that the incident waveguide mode is almost completely reflected on resonance, while far from the resonance the waveguide mode is almost completely transmitted. We also show that the properties of the waveguide systems can be accurately described using a single-mode scattering matrix theory. The transmission and reflection coefficients at waveguide junctions are either calculated using the concept of the characteristic impedance or are directly numerically extracted using full-wave three-dimensional finite-difference frequency-domain simulations.

  3. Tailored carbon nanotube immunosensors for the detection of microbial contamination.

    PubMed

    Prieto-Simón, B; Bandaru, N M; Saint, C; Voelcker, N H

    2015-05-15

    The use of carbon nanotubes (CNTs) as building blocks in the design of electrochemical biosensors has been attracting attention over the last few years, mainly due to their high electrical conductivity and large surface area. Here, we present two approaches based on tailored single-walled CNTs (SWCNTs) architectures to develop immunosensors for the bacteriophage MS2, a virus often detected in sewage-impacted water supplies. In the first approach, SWCNTs were used in the bottom-up design of sensors as antibody immobilization support. Carboxy-functionalised SWCNTs were covalently tethered onto gold electrodes via carbodiimide coupling to cysteamine-modified gold electrodes. These SWCNTs were hydrazide functionalized by electrochemical grafting of diazonium salts. Site-oriented immobilization of antibodies was then carried out through hydrazone bond formation. Results showed microarray electrode behavior, greatly improving the signal-to-noise ratio. Excellent sensitivity and limit of detection (9.3 pfu/mL and 9.8 pfu/mL in buffer and in river water, respectively) were achieved, due to the combination of the SWCNTs' ability to promote electron transfer reactions with electroactive species at low overpotentials and their high surface-to-volume ratio providing a favorable environment to immobilize biomolecules. In the second approach, SWCNTs were decorated with iron oxide nanoparticles. Diazonium salts were electrochemically grafted on iron-oxide-nanoparticle-decorated SWCNTs to functionalize them with hydrazide groups that facilitate site-directed immobilization of antibodies via hydrazone coupling. These magnetic immunocarriers facilitated MS2 separation and concentration on an electrode surface. This approach minimized non-specific adsorptions and matrix effects and allowed low limits of detection (12 pfu/mL and 39 pfu/mL in buffer and in river water, respectively) that could be further decreased by incubating the magnetic immunocarriers with larger volumes of sample

  4. Voltammetric Immunosensor Assembled on Carbon-Pyrenyl Nanostructures for Clinical Diagnosis of Type of Diabetes

    PubMed Central

    Singh, Vini; Krishnan, Sadagopan

    2015-01-01

    Herein we report the first serum insulin voltammetric immunosensor for diagnosis of type 1 and type 2 diabetic disorders. The sensor is composed of multiwalled carbon nanotube-pyrenebutyric acid frameworks on edge plane pyrolytic graphite electrodes (PGE/MWNT/Py) to which an anti-insulin antibody was covalently attached. The detection of picomolar levels of serum insulin binding to the surface antibody was achieved by monitoring the decrease in voltammetric current signals of a redox probe taken in the electrolyte solution. This method offered a detection limit of 15 pM for free insulin present in serum. This detection limit was further lowered to 5 pM by designing serum insulin conjugates with poly(acrylic acid)-functionalized magnetite nanoparticles (100 nm hydrodynamic diameter) and detecting the binding of MNP-serum insulin conjugate to the surface insulin-antibody on PGE/MWNT/Py electrodes. When tested on real patient serum samples, the sensor accurately measured insulin levels. To our knowledge, this is the first report of a voltammetric immunosensor capable of both diagnosing and distinguishing the type of diabetes based on serum insulin levels in diabetic patients. PMID:25675332

  5. One-step synthesis of potassium ferricyanide-doped polyaniline nanoparticles for label-free immunosensor.

    PubMed

    He, Sijing; Wang, Qiyou; Yu, Yanyan; Shi, Qiujia; Zhang, Lin; Chen, Zuanguang

    2015-06-15

    A novel, label-free and inherent electroactive redox immunosensor for ultrasensitive detection of carcinoembryonic antigen (CEA) was proposed based on gold nanoparticles (AuNPs) and potassium ferricyanide-doped polyaniline (FC-PANI) nanoparticles. FC-PANI composite was synthesized via oxidative polymerization of aniline, using potassium ferricyanide (K3[Fe(CN)6]) as both oxidant and dopant. FC-PANI acting as the signal indicator was first fixed on a gold electrode (GE) to be the signal layer. Subsequently, the negatively charged AuNPs could be adsorbed on the positively charged FC-PANI modified GE surface by electrostatic adsorption, and then to immobilize CEA antibody (anti-CEA) for the assay of CEA. The CEA concentration was measured through the decrease of amperometric signals in the corresponding specific binding of antigen and antibody. The wide linear range of the immunosensor was from 1.0 pg mL(-1) to 500.0 ng mL(-1) with a low detection limit of 0.1 pg mL(-1) (S/N=3). The proposed method would have a potential application in clinical immunoassays with the properties of facile procedure, stability, high sensitivity and selectivity. PMID:25618379

  6. A piezoelectric immunosensor for the determination of pesticide residues and metabolites in fruit juices.

    PubMed

    March, C; Manclús, J J; Jiménez, Y; Arnau, A; Montoya, A

    2009-05-15

    A quartz crystal microbalance (QCM) immunosensor was developed for the determination of the insecticide carbaryl and 3,5,6-trichloro-2-pyridinol (TCP), the main metabolite of the insecticide chlorpyrifos and of the herbicide triclopyr. The detection was based on a competitive conjugate-immobilized immunoassay format using monoclonal antibodies (MAbs). Hapten conjugates were covalently immobilized, via thioctic acid self-assembled monolayer (SAM), onto the gold electrode sensitive surface of the quartz crystal. This covalent immobilization allowed the reusability of the modified electrode surface for at least one hundred and fifty assays without significant loss of sensitivity. The piezoimmunosensor showed detection limits (analyte concentrations producing 10% inhibition of the maximum signal) of 11 and 7 microg l(-1) for carbaryl and TCP, respectively. The sensitivity attained (I(50) value) was around 30 microg l(-1) for both compounds. Linear working ranges were 15-53 microg l(-1) for carbaryl and 13-83 microg l(-1) for TCP. Each complete assay cycle took 20 min. The good sensitivity, specificity, and reusability achieved, together with the short response time, allowed the application of this immunosensor to the determination of carbaryl and TCP in fruits and vegetables at European regulatory levels, with high precision and accuracy. PMID:19269436

  7. Design and Analyses of a MEMS Based Resonant Magnetometer.

    PubMed

    Ren, Dahai; Wu, Lingqi; Yan, Meizhi; Cui, Mingyang; You, Zheng; Hu, Muzhi

    2009-01-01

    A novel design of a MEMS torsional resonant magnetometer based on Lorentz force is presented and fabricated. The magnetometer consists of a silicon resonator, torsional beam, excitation coil, capacitance plates and glass substrate. Working in a resonant condition, the sensor's vibration amplitude is converted into the sensing capacitance change, which reflects the outside magnetic flux-density. Based on the simulation, the key structure parameters are optimized and the air damping effect is estimated. The test results of the prototype are in accordance with the simulation results of the designed model. The resolution of the magnetometer can reach 30 nT. The test results indicate its sensitivity of more than 400 mV/μT when operating in a 10 Pa vacuum environment. PMID:22399981

  8. Ultracompact racetrack resonators based on hybrid plasmonic waveguides

    NASA Astrophysics Data System (ADS)

    Tang, Liangxiao; Hu, Feifei; Yi, Huaxiang; Zhou, Zhiping

    2012-11-01

    To promote the miniaturization and integration of devices, various optical components based on hybrid plasmonic waveguides have been proposed such as microring resonators and Y-splitter. However, their footprints are strongly limited by the radiation loss of the bends. Here, we propose and analyze a novel hybrid plasmonic waveguide (NHPW) which can be used to realize sharp bend with little radiation loss. Based on NHPW, ultracompact racetrack resonators are realized. A racetrack resonator with an outer radius of 0.5μm and straight waveguide of 0.1μm is constructed, which has an extinction ration of 12.56dB and a significantly large free space range of 265nm.

  9. Spherical-sapphire-based whispering gallery mode resonator thermometer

    NASA Astrophysics Data System (ADS)

    Yu, Lili; Fernicola, V.

    2012-09-01

    A novel microwave whispering gallery mode (WGM) resonator based on a spherical sapphire crystal was developed at INRIM and its use as a thermometer was tested. The temperature dependence of the WGM frequencies was studied and the most promising resonance near to 13.6 GHz, with a loaded quality factor as large as 82 000, was carefully investigated. Its potential use in thermometry was evaluated through a study of its main metrological characteristics, such as the temperature sensitivity, the frequency stability, the repeatability, and the resolution at several temperatures over the temperature range -40 °C to 85 °C. Finally, the INRIM spherical sapphire thermometer was compared with the NIST SWGT, a dielectric thermometer based on a cylindrical sapphire resonator [V. B. Braginsky, V. S. Ilchenko, and Kh. S. Bagdassarov, Phys. Lett. A 120(3), 300 (1987), 10.1016/0375-9601(87)90676-1].

  10. Spherical-sapphire-based whispering gallery mode resonator thermometer.

    PubMed

    Yu, Lili; Fernicola, V

    2012-09-01

    A novel microwave whispering gallery mode (WGM) resonator based on a spherical sapphire crystal was developed at INRIM and its use as a thermometer was tested. The temperature dependence of the WGM frequencies was studied and the most promising resonance near to 13.6 GHz, with a loaded quality factor as large as 82 000, was carefully investigated. Its potential use in thermometry was evaluated through a study of its main metrological characteristics, such as the temperature sensitivity, the frequency stability, the repeatability, and the resolution at several temperatures over the temperature range -40 °C to 85 °C. Finally, the INRIM spherical sapphire thermometer was compared with the NIST SWGT, a dielectric thermometer based on a cylindrical sapphire resonator [V. B. Braginsky, V. S. Ilchenko, and Kh. S. Bagdassarov, Phys. Lett. A 120(3), 300 (1987)]. PMID:23020404

  11. THz Emission Based On Intersubband Plasmon Resonances

    SciTech Connect

    Coquelin, M.; Zobl, R.; Strasser, G.; Gornik, E.; Bakshi, P.; Umansky, V.; Heiblum, M.

    2010-01-04

    The radiative decay of collective plasma oscillations as a new mechanism for THz emission is studied. This phenomenon is based on the attractive interaction of two intersubband plasmons. This interaction can be viewed as a collective e-e scattering phenomenon. The emission results fit very well to the results of the current voltage measurements indicating that the conditions for a plasma instability are reached.

  12. Electrochemical immunosensor for ultrasensitive detection of microcystin-LR based on graphene-gold nanocomposite/functional conducting polymer/gold nanoparticle/ionic liquid composite film with electrodeposition.

    PubMed

    Ruiyi, Li; Qianfang, Xia; Zaijun, Li; Xiulan, Sun; Junkang, Liu

    2013-06-15

    The study developed an electrochemical immunosensor for ultrasensitive detection of microcystin-LR in water. Graphene oxide and chloroauric acid were alternately electrodeposited on the surface of glassy carbon electrode for 20 cycles to fabricate graphene-gold nanocomposite. The composite was characterized and its apparent heterogeneous electron transfer rate constant (37.28±0.16 cm s (-1)) was estimated by Laviron's model. To immobilize microcystin-LR antibody and improve the electrical conductivity, 2,5-di-(2-thienyl)-1-pyrrole-1-(p-benzoic acid) and chloroauric acid were electrodeposited on the modified electrode in sequence. The ionic liquid was then dropped on the electrode surface and finally microcystin-LR antibody was covalently connected to the conducting polymer film. Experiment showed the electrochemical technique offers control over reaction parameters and excellent repeatability. The graphene-gold nanocomposite and gold nanoparticles enhance electron transfer of Fe(CN)6(3-/4-) to the electrode. The ionic liquid, 1-isobutyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide, improves stability of the antibody. The sensor displays good repeatability (RSD=1.2%), sensitive electrochemical response to microcystin-LR in the range of 1.0×10(-16)-8.0×10(-15)M and detection limit of 3.7×10(-17)M (S/N=3). The peak current change of the sensor after and before incubation with 2.0×10(-15)M of microcystin-LR can retain 95% over a 20-weeks storage period. Proposed method presents remarkable improvement of sensitivity, repeatability and stability when compared to present microcystin-LR sensors. It has been successfully applied to the microcystin-LR determination in water samples with a spiked recovery in the range of 96.3-105.8%. PMID:23434759

  13. A time domain based method for the accurate measurement of Q-factor and resonance frequency of microwave resonators

    SciTech Connect

    Gyüre, B.; Márkus, B. G.; Bernáth, B.; Simon, F.; Murányi, F.

    2015-09-15

    We present a novel method to determine the resonant frequency and quality factor of microwave resonators which is faster, more stable, and conceptually simpler than the yet existing techniques. The microwave resonator is pumped with the microwave radiation at a frequency away from its resonance. It then emits an exponentially decaying radiation at its eigen-frequency when the excitation is rapidly switched off. The emitted microwave signal is down-converted with a microwave mixer, digitized, and its Fourier transformation (FT) directly yields the resonance curve in a single shot. Being a FT based method, this technique possesses the Fellgett (multiplex) and Connes (accuracy) advantages and it conceptually mimics that of pulsed nuclear magnetic resonance. We also establish a novel benchmark to compare accuracy of the different approaches of microwave resonator measurements. This shows that the present method has similar accuracy to the existing ones, which are based on sweeping or modulating the frequency of the microwave radiation.

  14. [Immunosensors: sources of origin, achievements and perspectives].

    PubMed

    Starodub, M F; Starodub, V M

    2000-01-01

    The analysis of the recent data in the literature and results of investigations in the field of the development and study of function efficiency of different types of immune sensors, that are performed at the Department of Biochemistry Sensory and Regulatory Systems of the A. V. Palladin Institute of Biochemistry of Ukrainian National Academy of Sciences are presented. Sources of origination and perspectives of the devlopment of biosensors are discussed as well. The paper also gives an overview of main research projects at the Department, mainly in the filed of biosensors. They include development of the scientific bases for the creation of a new generation of chemo- and biosensors for their application in medicine and ecology. Multi-immune, multi-enzyme and combined multi-parametrical sensors can provide express analyses in laboratory and field conditions with the purpose to perform immune chemical diagnostics of diabet, kidney diseases, immune defficiencies, autoimmune, allergic, pre-infarction and pre-tumor states as well as to control total toxicity of the environment and identification of main types of toxic elements in it. The investigations are based on the latest achivements in the field of physics, chemistry, information technology and electronics with the use of different types of planar electrodes, ion sensitive field effect transistors (ISFETs), semiconductor capacitive structures, termistors, optrodes, piezocrystalls and application of such methods and effects as laser correlation spectroscopy, chemiluminescence, fluorescence, surface plasmon resonance, photoluminescence of porous silicon, interferometry, evanescent wave technique, nonemmiting energy transfer and holography. PMID:11200443

  15. Fiber-Optic SPR Immunosensors Tailored To Target Epithelial Cells through Membrane Receptors.

    PubMed

    Malachovská, Viera; Ribaut, Clotilde; Voisin, Valérie; Surin, Mathieu; Leclère, Philippe; Wattiez, Ruddy; Caucheteur, Christophe

    2015-06-16

    We report, for the first time, the use of a surface plasmon resonance (SPR) fiber-optic immunosensor for selective cellular detection through membrane protein targeting. The sensor architecture lies on gold-coated tilted fiber Bragg gratings (Au-coated TFBGs) photoimprinted in the fiber core via a laser technique. TFBGs operate in the near-infrared wavelength range at ∼1550 nm, yielding optical and SPR sensing characteristics that are advantageous for the analyses of cellular bindings and technical compatibility with relatively low-cost telecommunication-grade measurement devices. In this work, we take consider their numerous assets to figure out their ability to selectively detect intact epithelial cells as analytes in cell suspensions in the range of 2-5 × 10(6) cells mL(-1). For this, the probe was first thermally annealed to ensure a strong adhesion of the metallic coating to the fiber surface. Its surface was then functionalized with specific monoclonal antibodies via alkanethiol self-assembled monolayers (SAMs) against extracellular domain of epidermal growth factor receptors (EGFRs) and characterized by peak force tapping atomic force microscopy. A differential diagnosis has been demonstrated between two model systems. The developed immunosensors were able to monitor, in real time, the specific attachment of single intact cells in concentrations from 3 × 10(6) cells mL(-1). Such results confirm that the developed probe fits the lab-on-fiber technology and has the potential to be used as a disposable device for in situ and real-time clinical diagnosis. PMID:25962700

  16. Ultra-sensitive thermometer based on a compact optical resonator

    PubMed Central

    Weng, Wenle; Luiten, Andre N

    2014-01-01

    This article demonstrates a thermometer based on millimeter-scale crystalline disk optical-resonator. By measuring the relative speed difference between 2 colors of light that travel inside the disk, the temperature changes of the disk was measured with a precision of 30 billionths of a degree. PMID:27226990

  17. Magnetic Resonance Spectroscopy of siRNA-Based Cancer Therapy

    PubMed Central

    Penet, Marie-France; Chen, Zhihang; Mori, Noriko; Krishnamachary, Balaji; Bhujwalla, Zaver M.

    2016-01-01

    Small interfering RNA (siRNA) is routinely used as a biological tool to silence specific genes, and is under active investigation in cancer treatment strategies. Noninvasive magnetic resonance spectroscopy (MRS) provides the ability to assess the functional effects of siRNA-mediated gene silencing in cultured cancer cells, and following nanoparticle-based delivery in tumors in vivo. Here we describe the use of siRNA to downregulate choline kinase, a critical enzyme in choline phospholipid metabolism of cancer cells and tumors, and the use of 1H MRS of cells and 1H magnetic resonance spectroscopic imaging (MRSI) of tumors to assess the efficacy of the downregulation. PMID:26530913

  18. A prototype-based resonance model of rhythm categorization

    PubMed Central

    Bååth, Rasmus; Lagerstedt, Erik; Gärdenfors, Peter

    2014-01-01

    Categorization of rhythmic patterns is prevalent in musical practice, an example of this being the transcription of (possibly not strictly metrical) music into musical notation. In this article we implement a dynamical systems' model of rhythm categorization based on the resonance theory of rhythm perception developed by Large (2010). This model is used to simulate the categorical choices of participants in two experiments of Desain and Honing (2003). The model accurately replicates the experimental data. Our results support resonance theory as a viable model of rhythm perception and show that by viewing rhythm perception as a dynamical system it is possible to model central properties of rhythm categorization. PMID:26034564

  19. MEMS tunable optical filter based on multi-ring resonator

    SciTech Connect

    Dessalegn, Hailu E-mail: tsrinu@ece.iisc.ernet.in; Srinivas, T. E-mail: tsrinu@ece.iisc.ernet.in

    2014-10-15

    We propose a novel MEMS tunable optical filter with a flat-top pass band based on multi-ring resonator in an electrostatically actuated microcantilever for communication application. The filter is basically structured on a microcantilever beam and built in optical integrated ring resonator which is placed in one end of the beam to gain maximum stress on the resonator. Thus, when a DC voltage is applied, the beam will bend, that induces a stress and strain in the ring, which brings a change in refractive index and perimeter of the rings leading to change in the output spectrum shift, providing the tenability as high as 0.68nm/μN and it is capable of tuning up to 1.7nm.

  20. A microring resonator based negative permeability metamaterial sensor.

    PubMed

    Sun, Jun; Huang, Ming; Yang, Jing-Jing; Li, Ting-Hua; Lan, Yao-Zhong

    2011-01-01

    Metamaterials are artificial multifunctional materials that acquire their material properties from their structure, rather than inheriting them directly from the materials they are composed of, and they may provide novel tools to significantly enhance the sensitivity and resolution of sensors. In this paper, we derive the dispersion relation of a cylindrical dielectric waveguide loaded on a negative permeability metamaterial (NPM) layer, and compute the resonant frequencies and electric field distribution of the corresponding Whispering-Gallery-Modes (WGMs). The theoretical resonant frequency and electric field distribution results are in good agreement with the full wave simulation results. We show that the NPM sensor based on a microring resonator possesses higher sensitivity than the traditional microring sensor since with the evanescent wave amplification and the increase of NPM layer thickness, the sensitivity will be greatly increased. This may open a door for designing sensors with specified sensitivity. PMID:22164062

  1. Fano resonance based optical modulator reaching 85% modulation depth

    NASA Astrophysics Data System (ADS)

    Zhao, Wenyu; Jiang, Huan; Liu, Bingyi; Jiang, Yongyuan; Tang, Chengchun; Li, Junjie

    2015-10-01

    In this paper, we demonstrate the combination of nematic liquid crystal with a binary silicon nanohole array to realize a high performance Fano resonance based optical modulator. The simulations using a finite difference time domain method reveal that the sharp Fano profile in the binary array originates from the interaction of the in-phased and anti-phased lattice collective resonance hybridized through lattice coupling effects. Experimental results agree very well with the simulations and demonstrate the strong dependence of the Q factor and spectral contrast of the resonance on the radius difference of the two nanohole arrays. Infiltrated with nematic liquid crystal, E7, the Fano profile can be dynamically and continuously tuned by an applied voltage, and an unprecedented modulation depth up to 85% is achieved.

  2. Detection of small molecules with a flow immunosensor

    NASA Technical Reports Server (NTRS)

    Kusterbeck, Anne W.; Ligler, Frances S.

    1991-01-01

    We describe the development of an easy-to-use sensor with widespread applications for detecting small molecules. The flow immunosensor can analyze discrete samples in under one minute or continuously monitor a flowing stream for the presence of specific analytes. This detection system is extremely specific, and achieves a level of sensitivity which meets or exceeds the detection limits reported for rival assays. Because the system is also compact, transportable, and automated, it has the potential to impact diverse areas. For example, the flow immunosensor has successfully detected drugs of abuse and explosives, and may well address many of the needs of the environmental community with respect to continuous monitoring for pollutants. Efforts are underway to engineer a portable device in the field.

  3. 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.

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

    PubMed

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

    2016-06-24

    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. PMID:27183363

  5. Microwave Photonics Systems Based on Whispering-gallery-mode Resonators

    PubMed Central

    Coillet, Aurélien; Henriet, Rémi; Phan Huy, Kien; Jacquot, Maxime; Furfaro, Luca; Balakireva, Irina; Larger, Laurent; Chembo, Yanne K.

    2013-01-01

    Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various areas of technology and applied science, such as aerospace and communication engineering, sensing, metrology, nonlinear photonics, and quantum optics. In this article, we present the principal techniques used in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators. First detailed in this article is the protocol for resonator polishing, which is based on a grind-and-polish technique close to the ones used to polish optical components such as lenses or telescope mirrors. Then, a white light interferometric profilometer measures surface roughness, which is a key parameter to characterize the quality of the polishing. In order to launch light in the resonator, a tapered silica fiber with diameter in the micrometer range is used. To reach such small diameters, we adopt the "flame-brushing" technique, using simultaneously computer-controlled motors to pull the fiber apart, and a blowtorch to heat the fiber area to be tapered. The resonator and the tapered fiber are later approached to one another to visualize the resonance signal of the whispering gallery modes using a wavelength-scanning laser. By increasing the optical power in the resonator, nonlinear phenomena are triggered until the formation of a Kerr optical frequency comb is observed with a spectrum made of equidistant spectral lines. These Kerr comb spectra have exceptional characteristics that are suitable for several applications in science and technology. We consider the application related to ultra-stable microwave frequency synthesis and demonstrate the generation of a Kerr comb with GHz intermodal frequency. PMID:23963358

  6. Microwave photonics systems based on whispering-gallery-mode resonators.

    PubMed

    Coillet, Aurélien; Henriet, Rémi; Phan Huy, Kien; Jacquot, Maxime; Furfaro, Luca; Balakireva, Irina; Larger, Laurent; Chembo, Yanne K

    2013-01-01

    Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various areas of technology and applied science, such as aerospace and communication engineering, sensing, metrology, nonlinear photonics, and quantum optics. In this article, we present the principal techniques used in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators. First detailed in this article is the protocol for resonator polishing, which is based on a grind-and-polish technique close to the ones used to polish optical components such as lenses or telescope mirrors. Then, a white light interferometric profilometer measures surface roughness, which is a key parameter to characterize the quality of the polishing. In order to launch light in the resonator, a tapered silica fiber with diameter in the micrometer range is used. To reach such small diameters, we adopt the "flame-brushing" technique, using simultaneously computer-controlled motors to pull the fiber apart, and a blowtorch to heat the fiber area to be tapered. The resonator and the tapered fiber are later approached to one another to visualize the resonance signal of the whispering gallery modes using a wavelength-scanning laser. By increasing the optical power in the resonator, nonlinear phenomena are triggered until the formation of a Kerr optical frequency comb is observed with a spectrum made of equidistant spectral lines. These Kerr comb spectra have exceptional characteristics that are suitable for several applications in science and technology. We consider the application related to ultra-stable microwave frequency synthesis and demonstrate the generation of a Kerr comb with GHz intermodal frequency. PMID:23963358

  7. Fluorescent homogeneous immunosensors for detecting pathogenic bacteria.

    PubMed

    Heyduk, Ewa; Heyduk, Tomasz

    2010-01-15

    We developed a straightforward antibody-based assay for rapid homogeneous detection of bacteria. Our sensors utilize antibody recognizing cell-surface epitopes of the target cell. Two samples of the antibody are prepared, each labeled via nanometer size flexible linkers with short complementary oligonucleotides that are modified with fluorochromes that could participate in fluorescence resonance energy transfer (FRET). The length of the complementary oligonucleotide sequences was designed such that very little annealing occurred in the absence of the target cells. In the presence of the target cells the two labeled antibodies bind to the surface of the cell resulting in a large local concentration of the complementary oligonucleotides that are attached to the antibody. This in turn drives the annealing of the complementary oligonucleotides which brings the fluorescence probes to close proximity producing large FRET signals proportional to the amount of target cells. Long flexible linkers used to attach the oligonucleotides to the antibody enable target-induced oligonucleotide annealing even if the density of surface antigens is only modest. We used Escherichia coli 0157:H7 and Salmonella typhimurium to demonstrate that this design produced sensors exhibiting rapid response time, high specificity, and sensitivity in detecting the target bacteria. PMID:19782039

  8. Experiment study of an electron cyclotron resonant ion source based on a tapered resonance cavity

    SciTech Connect

    Yang, Juan; Shi, Feng; Jin, Yizhou; Wang, Yunmin; Komurasaki, Kimiya

    2013-12-15

    Electron cyclotron resonant plasma is one type of magnetised plasma generated by continuous microwave energy. It has the property of high degree of ionization and large volume at low gas pressure, which makes it useful for space propulsion and material processing. This article presents the experiment study of the plasma properties and ion beam extraction from an electron cyclotron resonant ion source based on a tapered resonance cavity. Optical emission spectroscopy based on a simple collisional radiation model was used for plasma diagnosis. Experiment results show that, at microwave power setting ranging from 7.06 to 17.40 W and mass flow rate ranging from 1 to 10 sccm, argon gas can be ionized. Ion beam of 109.1 mA from the ion source can be extracted at microwave power of 30 W, mass flow rate of 10 sccm, and accel voltage of 800 V. The diagnosed plasma temperature and density are 2.4–5.2 eV and 2 × 10{sup 16}–4.8 × 10{sup 17} m{sup −3}, respectively.

  9. Experiment study of an electron cyclotron resonant ion source based on a tapered resonance cavity

    NASA Astrophysics Data System (ADS)

    Yang, Juan; Shi, Feng; Jin, Yizhou; Wang, Yunmin; Komurasaki, Kimiya

    2013-12-01

    Electron cyclotron resonant plasma is one type of magnetised plasma generated by continuous microwave energy. It has the property of high degree of ionization and large volume at low gas pressure, which makes it useful for space propulsion and material processing. This article presents the experiment study of the plasma properties and ion beam extraction from an electron cyclotron resonant ion source based on a tapered resonance cavity. Optical emission spectroscopy based on a simple collisional radiation model was used for plasma diagnosis. Experiment results show that, at microwave power setting ranging from 7.06 to 17.40 W and mass flow rate ranging from 1 to 10 sccm, argon gas can be ionized. Ion beam of 109.1 mA from the ion source can be extracted at microwave power of 30 W, mass flow rate of 10 sccm, and accel voltage of 800 V. The diagnosed plasma temperature and density are 2.4-5.2 eV and 2 × 1016-4.8 × 1017 m-3, respectively.

  10. Tuning of resonance spacing over whole free spectral range based on Autler-Townes splitting in a single microring resonator.

    PubMed

    Gao, Ge; Li, Danping; Zhang, Yong; Yuan, Shuai; Armghan, Ammar; Huang, Qingzhong; Wang, Yi; Yu, Jinzhong; Xia, Jinsong

    2015-10-19

    In this paper, a single microring resonator structure formed by incorporating a reflectivity-tunable loop mirror is demonstrated for the tuning of resonance spacing. Autler-Townes splitting in the resonator is utilized to tune the spacing between two adjacent resonances by controlling the strength of coupling between the two counter-propagating degenerate modes in the microring resonator. A theoretical model based on the transfer matrix method is built to analyze the device. The theoretical analysis indicates that the resonance spacing can be tuned from zero to one free spectral range (FSR). In experiment, by integrating metallic microheater, the tuning of resonance spacing in the range of the whole FSR (1.17 nm) is achieved within 9.82 mW heating power dissipation. The device has potential for applications in reconfigurable optical filtering and microwave photonics. PMID:26480351

  11. Electrochemical immunosensors for detection of cancer protein biomarkers.

    PubMed

    Chikkaveeraiah, Bhaskara V; Bhirde, Ashwinkumar A; Morgan, Nicole Y; Eden, Henry S; Chen, Xiaoyuan

    2012-08-28

    Bioanalytical methods have experienced unprecedented growth in recent years, driven in large part by the need for faster, more sensitive, more portable ("point of care") systems to detect protein biomarkers for clinical diagnosis. Electrochemical detection strategies, used in conjunction with immunosensors, offer advantages because they are fast, simple, and low cost. Recent developments in electrochemical immunosensors have significantly improved the sensitivity needed to detect low concentrations of biomarkers present in early stages of cancer. Moreover, the coupling of electrochemical devices with nanomaterials, such as gold nanoparticles, carbon nanotubes, magnetic particles, and quantum dots, offers multiplexing capability for simultaneous measurements of multiple cancer biomarkers. This review will discuss recent advances in the development of electrochemical immunosensors for the next generation of cancer diagnostics, with an emphasis on opportunities for further improvement in cancer diagnostics and treatment monitoring. Details will be given for strategies to increase sensitivity through multilabel amplification, coupled with high densities of capture molecules on sensor surfaces. Such sensors are capable of detecting a wide range of protein quantities, from nanogram to femtogram (depending on the protein biomarkers of interest), in a single sample. PMID:22835068

  12. Investigation of a near-infrared fiber optic immunosensor

    NASA Astrophysics Data System (ADS)

    Daneshvar, Maryam I.; Casay, Guillermo A.; Lipowska, Malgorzata; Patonay, Gabor; Strekowski, Lucjan

    1994-03-01

    The designs of NIR optical fiber immunosensors for the detection of biomolecules are discussed. The use of fiber optics combined with laser-excited fluorescence detection ((lambda) max equals 780 nm) and immunochemical techniques has provided the essential components for developing simpler and more practical, sensitive and selective immunosensors. The antibody is immobilized on the distal end of a surface-activated polymethyl methylacrylate sensor. As the probe is placed in different concentrations of antigenic substance, the antibody reacts with its corresponding antigen through sandwich and/or competitive immunoassays. The concentrations varied from 10 - 100 ng/ml. The near-infrared dye labeled antigen - antibody complex is excited and the emitted fluorescence is collected with a silicon photodiode detector equipped with an 820-nm bandpass filter. In order to determine various factors influencing the immunosensor's performance, the fluorescence intensity responses are obtained under a variety of conditions. The sensor response depending on the type of surface-activating reagent, surface activation period, incubation time, and other measurement conditions also are discussed.

  13. Electrochemical Immunosensors for Detection of Cancer Protein Biomarkers

    PubMed Central

    Chikkaveeraiah, Bhaskara V.; Bhirde, Ashwinkumar; Morgan, Nicole Y.; Eden, Henry S.

    2012-01-01

    Bioanalytical methods have experienced unprecedented growth in recent years, driven in large part by the need for faster, more sensitive, more portable (“point of care”) systems to detect protein biomarkers for clinical diagnosis. Electrochemical detection strategies, used in conjunction with immunosensors, offer advantages, because they are fast, simple, and low cost. Recent developments in electrochemical immunosensors have significantly improved the sensitivity needed to detect low concentrations of biomarkers present in early stages of cancer. Moreover, the coupling of electrochemical devices with nanomaterials, such as gold nanoparticles, carbon nanotubes, magnetic particles, and quantum dots, offers multiplexing capability for simultaneous measurements of multiple cancer biomarkers. This review will discuss recent advances in the development of electrochemical immunosensors for the next-generation of cancer diagnostics, with an emphasis on opportunities for further improvement in cancer diagnostics and treatment monitoring. Details will be given for strategies to increase sensitivity through multi-label amplification, coupled with high densities of capture molecules on sensor surfaces. Such sensors are capable of detecting a wide range of protein quantities, from ng to fg (depending on the protein biomarkers of interest), in a single sample. PMID:22835068

  14. Scanning near field microwave microscopy based on an active resonator

    NASA Astrophysics Data System (ADS)

    Qureshi, Naser; Kolokoltsev, Oleg; Ordonez-Romero, Cesar Leonardo

    2014-03-01

    A large number of recent implementations of near field scanning microwave microscopy (NFSMM) have been based on the perturbation of a resonant cavity connected to a sharp scanning probe. In this work we present results from an alternative approach: the perturbation of a microwave source connected to a scanning tip. Based on a yittrium iron garnet (YIG) cavity ring resonator this scanning probe system has a quality factor greater than 106, which allows us to detect very small frequency shifts, which translates to a very high sensitivity in sample impedance measurements. Using a selection of representative semiconductor, metal and biological samples we show how this approach leads to unusually high sensitivity and spatial resolution. Work supported by a grant from PAPIIT, UNAM 104513.

  15. Detection of Tetrodotoxins in Puffer Fish by a Self-Assembled Monolayer-Based Immunoassay and Comparison with Surface Plasmon Resonance, LC-MS/MS, and Mouse Bioassay.

    PubMed

    Reverté, Laia; de la Iglesia, Pablo; del Río, Vanessa; Campbell, Katrina; Elliott, Christopher T; Kawatsu, Kentaro; Katikou, Panagiota; Diogène, Jorge; Campàs, Mònica

    2015-11-01

    The increasing occurrence of puffer fish containing tetrodotoxin (TTX) in the Mediterranean could represent a major food safety risk for European consumers and threaten the fishing industry. The work presented herein describes the development of a new enzyme linked immunosorbent assay (mELISA) based on the immobilization of TTX through dithiol monolayers self-assembled on maleimide plates, which provides an ordered and oriented antigen immobilization and favors the antigen-antibody affinity interaction. The mELISA was found to have a limit of detection (LOD) of TTX of 0.23 mg/kg of puffer fish matrix. The mELISA and a surface plasmon resonance (SPR) immunosensor previously developed were employed to establish the cross-reactivity factors (CRFs) of 5,6,11-trideoxy-TTX, 5,11-deoxy-TTX, 11-nor-TTX-6-ol, and 5,6,11-trideoxy-4-anhydro-TTX, as well as to determine TTX equivalent contents in puffer fish samples. Results obtained by both immunochemical tools were correlated (R(2) = 0.977). The puffer fish samples were also analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the corresponding CRFs were applied to the individual TTX contents. Results provided by the immunochemical tools, when compared with those obtained by LC-MS/MS, showed a good degree of correlation (R(2) = 0.991 and 0.979 for mELISA and SPR, respectively). The mouse bioassay (MBA) slightly overestimated the CRF adjusted TTX content of samples when compared with the data obtained from the other techniques. The mELISA has been demonstrated to be fit for the purpose for screening samples in monitoring programs and in research activities. PMID:26424329

  16. A personal computer-based nuclear magnetic resonance spectrometer

    NASA Astrophysics Data System (ADS)

    Job, Constantin; Pearson, Robert M.; Brown, Michael F.

    1994-11-01

    Nuclear magnetic resonance (NMR) spectroscopy using personal computer-based hardware has the potential of enabling the application of NMR methods to fields where conventional state of the art equipment is either impractical or too costly. With such a strategy for data acquisition and processing, disciplines including civil engineering, agriculture, geology, archaeology, and others have the possibility of utilizing magnetic resonance techniques within the laboratory or conducting applications directly in the field. Another aspect is the possibility of utilizing existing NMR magnets which may be in good condition but unused because of outdated or nonrepairable electronics. Moreover, NMR applications based on personal computer technology may open up teaching possibilities at the college or even secondary school level. The goal of developing such a personal computer (PC)-based NMR standard is facilitated by existing technologies including logic cell arrays, direct digital frequency synthesis, use of PC-based electrical engineering software tools to fabricate electronic circuits, and the use of permanent magnets based on neodymium-iron-boron alloy. Utilizing such an approach, we have been able to place essentially an entire NMR spectrometer console on two printed circuit boards, with the exception of the receiver and radio frequency power amplifier. Future upgrades to include the deuterium lock and the decoupler unit are readily envisioned. The continued development of such PC-based NMR spectrometers is expected to benefit from the fast growing, practical, and low cost personal computer market.

  17. Resonant tunnelling diodes based on graphene/h-BN heterostructure

    NASA Astrophysics Data System (ADS)

    Nguyen, V. Hung; Mazzamuto, F.; Bournel, A.; Dollfus, P.

    2012-08-01

    In this work, we propose a resonant tunnelling diode (RTD) based on a double-barrier graphene/boron nitride (BN) heterostructure as a device suitable to take advantage of the elaboration of atomic sheets containing different domains of BN and C phases within a hexagonal lattice. The device operation and performance are investigated by means of a self-consistent solution within the non-equilibrium Green's function formalism on a tight-binding Hamiltonian. This RTD exhibits a negative differential conductance effect, which involves the resonant tunnelling through both the electron and hole bound states in the graphene quantum well. It is shown that the peak-to-valley ratio reaches a value of ˜4 at room temperature even for zero bandgap and can be higher than 10 when a finite gap opens in the graphene channel.

  18. Magnetically tunable Mie resonance-based dielectric metamaterials

    PubMed Central

    Bi, Ke; Guo, Yunsheng; Liu, Xiaoming; Zhao, Qian; Xiao, Jinghua; Lei, Ming; Zhou, Ji

    2014-01-01

    Electromagnetic materials with tunable permeability and permittivity are highly desirable for wireless communication and radar technology. However, the tunability of electromagnetic parameters is an immense challenge for conventional materials and metamaterials. Here, we demonstrate a magnetically tunable Mie resonance-based dielectric metamaterials. The magnetically tunable property is derived from the coupling of the Mie resonance of dielectric cube and ferromagnetic precession of ferrite cuboid. Both the simulated and experimental results indicate that the effective permeability and permittivity of the metamaterial can be tuned by modifying the applied magnetic field. This mechanism offers a promising means of constructing microwave devices with large tunable ranges and considerable potential for tailoring via a metamaterial route. PMID:25384397

  19. Elastomeric Polymer Resonant Waveguide Grating based Pressure Sensor

    PubMed Central

    Song, Fuchuan; Xie, Antonio Jou; Seo, Sang-Woo

    2014-01-01

    In this paper, we demonstrate an elastomeric polymer resonant waveguide grating structure to be used as a pressure sensor. The applied pressure is measured by optical resonance spectrum peak shift. The sensitivity - as high as 86.74pm/psi or 12.58pm/kPa - has been experimentally obtained from a fabricated sensor. Potentially, the sensitivity of the demonstrated sensor can be tuned to different pressure ranges by the choices of elastic properties and layer thicknesses of the waveguide and cladding layers. The simulation results agree well with experimental results and indicate that the dominant effect on the sensor is the change of grating period when external pressure is applied. Based on the two-dimensional planar structure, the demonstrated sensor can be used to measure applied surface pressure optically, which has potential applications for optical ultrasound imaging and pressure wave detection/mapping. PMID:25419447

  20. Magnetically tunable Mie resonance-based dielectric metamaterials.

    PubMed

    Bi, Ke; Guo, Yunsheng; Liu, Xiaoming; Zhao, Qian; Xiao, Jinghua; Lei, Ming; Zhou, Ji

    2014-01-01

    Electromagnetic materials with tunable permeability and permittivity are highly desirable for wireless communication and radar technology. However, the tunability of electromagnetic parameters is an immense challenge for conventional materials and metamaterials. Here, we demonstrate a magnetically tunable Mie resonance-based dielectric metamaterials. The magnetically tunable property is derived from the coupling of the Mie resonance of dielectric cube and ferromagnetic precession of ferrite cuboid. Both the simulated and experimental results indicate that the effective permeability and permittivity of the metamaterial can be tuned by modifying the applied magnetic field. This mechanism offers a promising means of constructing microwave devices with large tunable ranges and considerable potential for tailoring via a metamaterial route. PMID:25384397

  1. Fano resonance in anodic aluminum oxide based photonic crystals

    PubMed Central

    Shang, Guo Liang; Fei, Guang Tao; Zhang, Yao; Yan, Peng; Xu, Shao Hui; Ouyang, Hao Miao; De Zhang, Li

    2014-01-01

    Anodic aluminum oxide based photonic crystals with periodic porous structure have been prepared using voltage compensation method. The as-prepared sample showed an ultra-narrow photonic bandgap. Asymmetric line-shape profiles of the photonic bandgaps have been observed, which is attributed to Fano resonance between the photonic bandgap state of photonic crystal and continuum scattering state of porous structure. And the exhibited Fano resonance shows more clearly when the sample is saturated ethanol gas than air-filled. Further theoretical analysis by transfer matrix method verified these results. These findings provide a better understanding on the nature of photonic bandgaps of photonic crystals made up of porous materials, in which the porous structures not only exist as layers of effective-refractive-index material providing Bragg scattering, but also provide a continuum light scattering state to interact with Bragg scattering state to show an asymmetric line-shape profile. PMID:24398625

  2. A temperature sensor based on a whispering gallery mode resonator

    NASA Astrophysics Data System (ADS)

    Yu, L.; Fernicola, V.

    2013-09-01

    This paper deals with a microwave temperature sensor based on a whispering gallery mode (WGM) resonator whose dielectric medium is a cylindrical sapphire crystal. The performance as temperature sensor were investigated a three WGMs resonant frequencies over the temperature range from -40 °C to 85 °C. It was found that the quality factor for these WGMs can be in excess of 1.7ṡ105, potentially enabling high-resolution measurements. The temperature repeatability, stability, hysteresis, frequency-vs-temperature sensitivity of the WGM temperature sensor are reported. Moreover, two sapphires, which have the same nominal characteristics, were investigated in order to assess the system reproducibility and the results reported.

  3. A parametric vocal fold model based on magnetic resonance imaging.

    PubMed

    Wu, Liang; Zhang, Zhaoyan

    2016-08-01

    This paper introduces a parametric three-dimensional body-cover vocal fold model based on magnetic resonance imaging (MRI) of the human larynx. Major geometric features that are observed in the MRI images but missing in current vocal fold models are discussed, and their influence on vocal fold vibration is evaluated using eigenmode analysis. Proper boundary conditions for the model are also discussed. Based on control parameters corresponding to anatomic landmarks that can be easily measured, this model can be adapted toward a subject-specific vocal fold model for voice production research and clinical applications. PMID:27586774

  4. Resonance

    NASA Astrophysics Data System (ADS)

    Perozzi, E.; Murdin, P.

    2000-11-01

    A resonance in CELESTIAL MECHANICS occurs when some of the quantities characterizing the motion of two or more celestial bodies can be considered as commensurable, i.e. their ratio is close to an integer fraction. In a simplified form, this can be expressed as ...

  5. Tunable Fano resonances based on microring resonator with feedback coupled waveguide.

    PubMed

    Zhao, Guolin; Zhao, Ting; Xiao, Huifu; Liu, Zilong; Liu, Guipeng; Yang, Jianhong; Ren, Zhaoyu; Bai, Jintao; Tian, Yonghui

    2016-09-01

    We experimentally demonstrate a tunable Fano resonance which originates from the optical interference between two different resonant cavities using silicon micro-ring resonator with feedback coupled waveguide fabricated on silicon-on-insulator (SOI) substrate. The resonance spectrum can be periodically tuned via changing the resonant wavelengths of two resonators through the thermo-optic effect. In addition to this, we can also change the transmission loss of the feedback coupled waveguide (FCW) to tune the resonance spectrum by the injection free carriers to FCW. We also build the theoretical model and we analyze the device performance by using the scattering matrix method. The simulation results are in a good agreement with the experimental results. The measurement maximum extinction ratio of the Fano resonance is as high as 30.8dB. Therefore, the proposed device is a most promising candidate for high on/off ratio optical switching/modulating, high-sensitivity biochemical sensing. PMID:27607626

  6. Investigation of refractive index sensing based on Fano resonance in fiber Bragg grating ring resonators.

    PubMed

    Campanella, Carlo Edoardo; De Leonardis, Francesco; Mastronardi, Lorenzo; Malara, Pietro; Gagliardi, Gianluca; Passaro, Vittorio M N

    2015-06-01

    In this paper we theoretically investigate a ring resonant cavity obtained by closing on itself a π-shifted fiber Bragg grating, to be used for refractive index sensing applications. Differently from a conventional π-shifted fiber Bragg grating, the spectral structure of this cavity is characterized by an asymmetric splitting doublet composed by a right side resonance having an asymmetric Fano profile and a left side resonance having a symmetric Lorentzian profile. The right side resonance shows a narrower and sharper peak than all the other kinds of resonance achievable with both conventional ring resonators and π-shifted fiber Bragg gratings. A reduction of the resonant linewidth with respect to a conventional π-shifted Fiber Bragg grating and a fiber ring resonator, having the same physical parameters, is theoretically proved, achieving up to five orders of magnitude improvement with respect to the usual ring resonator. Due to these resonance features, the π-shifted Bragg grating ring resonator results suitable for RI sensing applications requiring extremely narrow resonances for high resolution measurements. In particular, by assuming a refractive index sensing to detect the presence of sugar in water, the sensor can show a theoretical resolution better than 10-9 RIU. PMID:26072795

  7. Towards Automated Structure-Based NMR Resonance Assignment

    NASA Astrophysics Data System (ADS)

    Jang, Richard; Gao, Xin; Li, Ming

    We propose a general framework for solving the structure-based NMR backbone resonance assignment problem. The core is a novel 0-1 integer programming model that can start from a complete or partial assignment, generate multiple assignments, and model not only the assignment of spins to residues, but also pairwise dependencies consisting of pairs of spins to pairs of residues. It is still a challenge for automated resonance assignment systems to perform the assignment directly from spectra without any manual intervention. To test the feasibility of this for structure-based assignment, we integrated our system with our automated peak picking and sequence-based resonance assignment system to obtain an assignment for the protein TM1112 with 91% recall and 99% precision without manual intervention. Since using a known structure has the potential to allow one to use only N-labeled NMR data and avoid the added expense of using C-labeled data, we work towards the goal of automated structure-based assignment using only such labeled data. Our system reduced the assignment error of Xiong-Pandurangan-Bailey-Kellogg's contact replacement (CR) method, which to our knowledge is the most error-tolerant method for this problem, by 5 folds on average. By using an iterative algorithm, our system has the added capability of using the NOESY data to correct assignment errors due to errors in predicting the amino acid and secondary structure type of each spin system. On a publicly available data set for Ubiquitin, where the type prediction accuracy is 83%, we achieved 91% assignment accuracy, compared to the 59% accuracy that was obtained without correcting for typing errors.

  8. A nanohybrid of platinum nanoparticles-porous ZnO-hemin with electrocatalytic activity to construct an amplified immunosensor for detection of influenza.

    PubMed

    Yang, Zhe-Han; Zhuo, Ying; Yuan, Ruo; Chai, Ya-Qin

    2016-04-15

    In this work, a nanohybrid of platinum nanoparticles-porous ZnO spheres-hemin (Pt-pZnO-hemin) was synthesized for construction of alkaline phosphatase-based immunosensor for detection of influenza. Briefly, porous ZnO spheres (pZnO) were prepared using soluble starches as the capping agent, followed by surface functionalization of platinum nanoparticles via a hydrothermal method (Pt-pZnO). Then, hemin with carboxylic functionality was spontaneously adsorbed onto Pt-pZnO by ester-like binding between carboxylic group of hemin and ZnO. Compared with platinum nanoparticles and hemin, the resulting Pt-pZnO-hemin nanohybrid showed more excellent electrocatalysis activity toward 1-naphthol (1-NP). Taking advantage of the Pt-pZnO-hemin, we have developed an amplified electrochemical immunosensor based on in situ generation of redox probe by alkaline phosphatase (ALP) and Pt-pZnO-hemin as signal enhancer. Herein, electrochemically active 1-NP was generated by enzymatic hydrolysis of inactive 1-naphthyl phosphate by ALP, then Pt-pZnO-hemin was used as catalyst to catalytically oxidize 1-NP, resulting in electrochemical signal amplification. Furthermore, in comparison with other nanomaterials including Au-pZnO, Pt-pZnO and Au-pZnO-hemin, the excellent catalytical property of Pt-pZnO-hemin make it a promising nanohybrid material for ALP-based immunosensor for signal amplification. PMID:26649489

  9. Resonance-based bonding detection for piezoelectric fiber composites

    NASA Astrophysics Data System (ADS)

    Wang, Dwo-Wen; Yin, Ching-Chung

    2008-11-01

    A resonance-based method is presented to determine the bonding conditions of piezoelectric fiber composite (PFC) patches attached to host structures. The PFCs are used to be functional materials by applying voltage through the interdigital electrodes symmetrically aligned on opposite surfaces of the composite patches. Interfacial debonds usually degrade the function. Only the edge debonds are taken into account in this paper. A partially debonded patch bears an in-plane extensional vibration if the interdigital electrodes are excited by a sinusoidal voltage. Electric impedance of the PFC patch adhered on an aluminum plate was measured in a broad frequency range to seek the resonant frequencies. The modal characteristics depend on the size of debond, material properties of the PFC, and stiffness of remaining adhesive in front of the edge debond. Extensional vibration of an elastic sheet is characteristic of the resonant frequencies being inversely proportional to the debonding length. The lowest several modes are considered. Experimental results indicate that self-detecting progressive debonding between the PFC patch and the host plate is feasible.

  10. Resonant energy transfer based biosensor for detection of multivalent proteins.

    SciTech Connect

    Song, X.; Swanson, Basil I.

    2001-01-01

    We have developed a new fluorescence-based biosensor for sensitive detection of species involved in a multivslent interaction. The biosensor system utilizes specific interactions between proteins and cell surface receptors, which trigger a receptor aggregation process. Distance-dependent fluorescence self-quenching and resonant energy transfer mechanisms were coupled with a multivalent interaction to probe the receptor aggregation process, providing a sensitive and specific signal transduction method for such a binding event. The fluorescence change induced by the aggregation process can be monitored by different instrument platforms, e.g. fluorimetry and flow cytometry. In this article, a sensitive detection of pentavalent cholera toxin which recognizes ganglioside GM1 has been demonstrated through the resonant energy transfer scheme, which can achieve a double color change simultaneously. A detection sensitivity as high as 10 pM has been achieved within a few minutes (c.a. 5 minutes). The simultaneous double color change (an increase of acceptor fluorescence and a decrease of donor fluorescence intensity) of two similar fluorescent probes provides particularly high detection reliability owing to the fact that they act as each other's internal reference. Any external perturbation such as environmental temperature change causes no significant change in signal generation. Besides the application for biological sensing, the method also provides a useful tool for investigation of kinetics and thermodynamics of a multivalent interaction. Keywords: Biosensor, Fluorescence resonant energy transfer, Multivalent interaction, Cholera Toxin, Ganglioside GM1, Signal Transduction

  11. Disposable amperometric immunosensor for the detection of polycyclic aromatic hydrocarbons (PAHs) using screen-printed electrodes.

    PubMed

    Fähnrich, K A; Pravda, M; Guilbault, G G

    2003-01-01

    An amperometric immunosensor for polycyclic aromatic hydrocarbons (PAHs) was developed. The immunosensor was based on disposable screen-printed carbon electrodes. The coating antigen used was phenanthrene-9-carboxaldehyde coupled to bovine serum albumin (BSA) via adipic acid dihydrazide. Antibodies were monoclonal mouse anti-phenanthrene. The enzyme alkaline phosphatase (AP) was used in combination with the substrate p-aminophenyl phosphate (pAPP) for detection at +300 mV (vs. Ag/AgCl). Various assay types were compared. Good results were achieved with an indirect co-exposure competition assay with a LOD of 0.8 ng/ml (800 ppt) and an IC(50) of 7.1 ng/ml (7.1 ppb) for phenanthrene. An indirect competition assay could detect phenanthrene with a LOD of 2 ng/ml (IC(50): 15 ng/ml) and an indirect displacement assay with a LOD of 2 ng/ml (IC(50): 11 ng/ml) at a 5 microl surface coating of 8.8 microg/ml phenanthrene-BSA conjugate. A coating concentration of 2.2 microg/ml allowed detection with a LOD of 0.25 ng/ml (250 ppt) with the indirect competition assay. The influence of the coating concentration on the sensor performance was investigated. Cross-reactivities were tested for 16 important PAHs. Anthracene and chrysene showed strong cross-reactivity, whereas benzo[g,h,i]perylene and dibenzo[a,h]anthracene showed no cross-reactivity. PMID:12445447

  12. Theoretical considerations for evanescent-wave immunosensors in biomedical applications

    NASA Astrophysics Data System (ADS)

    Orvedahl, Donna S.; Love, Walter F.; Slovacek, Rudolf E.

    1992-03-01

    Using evanescent wave immunosensors, a fluorescent labeled analyte may be concentrated within the active surface region by a combination of diffusion to the fiber surface and trapping of the molecule or complex by an antigen-antibody affinity reaction. With the dye B- phycoerythrin, approximately 1.5 X 10-22 moles may be sensed over a 1 mm2 surface. From this number (as determined for a particular dye and instrumentation system) and antibody affinity constants, limits to assay sensitivity can be calculated and the kinetics modeled.

  13. An ultrasensitive optical label-free polymeric biosensor based on concentric triple microring resonators with a central microdisk resonator

    NASA Astrophysics Data System (ADS)

    Malmir, Kiana; Habibiyan, Hamidreza; Ghafoorifard, Hassan

    2016-04-01

    In this paper we propose an optical label-free biosensor based on a polymeric platform. Label-free biosensors have not the drawbacks and stability problems of commercialized devices which are used for detection of labeled molecules. In addition, we choose polymeric platform, due to simple and low cost fabrication process and also high biocompatibility properties. The suggested structure consists of concentric triple ring resonators along with a disk resonator which offers deeper notches, higher sensitivity and vaster detection area with respect to other similar configurations such as single ring resonator, double concentric ring resonators, etc. Our numerical simulations based on the finite difference time domain (FDTD) method, show that in optimized structure, a transmission notch depth of -48.7 dB for sensor at rest and a free spectral range of 56 nm are achievable. In addition, resonance wavelength sensitivity and output power sensitivity of sensor are 1000 nm/RIU and 1.8×104 dB/RIU, respectively. The external radius of outer ring resonator is only 5 μm, and detection area of the sensor is 40.37 μm2. With this small size, to the best of our knowledge, the obtained notch depth and sensitivity parameters are one of the highest values in ring resonator-based biosensors reported to date.

  14. Localized surface plasmon resonance of silver nanoisland based glucose sensor

    NASA Astrophysics Data System (ADS)

    Venugopal, N.; Mitra, Anirban

    2013-06-01

    Study of optical properties of glucose is an attractive research topic for years. One of the goals is to develop a portable device for simple, reliable, cost effective and non-invasive monitoring of glucose in blood for diabetics. In this work, we study localized surface plasmon resonance (LSPR) of Ag nanoisland based glucose sensor. The progressive shift in LSPR caused by the various concentration of glucose from 2M to 10M has been investigated to monitor the sensing property. We correlate the redshift of LSPR is due to the change in refractive index of surrounding glucose medium. Preliminary results show that this may possibly reveal a new pathway for sensing glucose.

  15. Magneto-optical switching devices based on Si resonators

    NASA Astrophysics Data System (ADS)

    Noda, Kazuki; Okada, Kazuya; Amemiya, Yoshiteru; Yokoyama, Shin

    2016-04-01

    The magneto-optical switching devices based on Si ring and Si photonic crystal resonators have been fabricated using a Bi3Fe5O12 (BIG) film deposited by the metal organic decomposition (MOD) method. The quality of the obtained BIG film was evaluated by X-ray diffraction and the magneto-optical Kerr effect and relatively good results were obtained. The light modulations of both devices were ≦20% at a wavelength of ˜1.5 µm. The operation mechanisms of both devices are explained by the Cotton-Mouton effect where the magnetic field direction is perpendicular to the light propagation direction.

  16. A 10kW series resonant converter design, transistor characterization, and base-drive optimization

    NASA Technical Reports Server (NTRS)

    Robson, R.; Hancock, D.

    1981-01-01

    Transistors are characterized for use as switches in resonant circuit applications. A base drive circuit to provide the optimal base drive to these transistors under resonant circuit conditions is developed and then used in the design, fabrication and testing of a breadboard, spaceborne type 10 kW series resonant converter.

  17. Miniature Trace Gas Detector Based on Microfabricated Optical Resonators

    NASA Technical Reports Server (NTRS)

    Aveline, David C.; Yu, Nan; Thompson, Robert J.; Strekalov, Dmitry V.

    2013-01-01

    While a variety of techniques exist to monitor trace gases, methods relying on absorption of laser light are the most commonly used in terrestrial applications. Cavity-enhanced absorption techniques typically use high-reflectivity mirrors to form a resonant cavity, inside of which a sample gas can be analyzed. The effective absorption length is augmented by the cavity's high quality factor, or Q, because the light reflects many times between the mirrors. The sensitivity of such mirror-based sensors scales with size, generally making them somewhat bulky in volume. Also, specialized coatings for the high-reflectivity mirrors have limited bandwidth (typically just a few nanometers), and the delicate mirror surfaces can easily be degraded by dust or chemical films. As a highly sensitive and compact alternative, JPL is developing a novel trace gas sensor based on a monolithic optical resonator structure that has been modified such that a gas sample can be directly injected into the cavity. This device concept combines ultra-high Q optical whispering gallery mode resonators (WGMR) with microfabrication technology used in the semiconductor industry. For direct access to the optical mode inside a resonator, material can be precisely milled from its perimeter, creating an open gap within the WGMR. Within this open notch, the full optical mode of the resonator can be accessed. While this modification may limit the obtainable Q, calculations show that the reduction is not significant enough to outweigh its utility for trace gas detection. The notch can be milled from the high- Q crystalline WGMR with a focused ion beam (FIB) instrument with resolution much finer than an optical wavelength, thereby minimizing scattering losses and preserving the optical quality. Initial experimental demonstrations have shown that these opened cavities still support high-Q whispering gallery modes. This technology could provide ultrasensitive detection of a variety of molecular species in an

  18. Design and evaluation of a 1.1-GHz surface coil resonator for electron paramagnetic resonance-based tooth dosimetry.

    PubMed

    Sugawara, Hirotaka; Hirata, Hiroshi; Petryakov, Sergey; Lesniewski, Piotr; Williams, Benjamin B; Flood, Ann Barry; Swartz, Harold M

    2014-06-01

    This paper describes an optimized design of a surface coil resonator for in vivo electron paramagnetic resonance (EPR)-based tooth dosimetry. Using the optimized resonator, dose estimates with the standard error of the mean of approximately 0.5 Gy were achieved with irradiated human teeth. The product of the quality factor and the filling factor of the resonator was computed as an index of relative signal intensity in EPR tooth dosimetry by the use of 3-D electromagnetic wave simulator and radio frequency circuit design environment (ANSYS HFSS and Designer). To verify the simulated results of the signal intensity in our numerical model of the resonator and a tooth sample, we experimentally measured the radiation-induced signals from an irradiated tooth with an optimally designed resonator. In addition to the optimization of the resonator design, we demonstrated the improvement of the stability of EPR spectra by decontamination of the surface coil resonator using an HCl solution, confirming that contamination of small magnetic particles on the silver wire of the surface coil had degraded the stability of the EPR spectral baseline. PMID:24845300

  19. Macromolecular and Dendrimer Based Magnetic Resonance Contrast Agents

    PubMed Central

    Bumb, Ambika; Brechbiel, Martin W.; Choyke, Peter

    2010-01-01

    Magnetic resonance imaging (MRI) is a powerful imaging modality that can provide an assessment of function or molecular expression in tandem with anatomic detail. Over the last 20–25 years, a number of gadolinium based MR contrast agents have been developed to enhance signal by altering proton relaxation properties. This review explores a range of these agents from small molecule chelates, such as Gd-DTPA and Gd-DOTA, to macromolecular structures composed of albumin, polylysine, polysaccharides (dextran, inulin, starch), poly(ethylene glycol), copolymers of cystamine and cystine with GD-DTPA, and various dendritic structures based on polyamidoamine and polylysine (Gadomers). The synthesis, structure, biodistribution and targeting of dendrimer-based MR contrast agents are also discussed. PMID:20590365

  20. Surface plasmon resonance based fiber optic glucose biosensor

    NASA Astrophysics Data System (ADS)

    Srivastava, Sachin K.; Verma, Roli; Gupta, Banshi D.

    2012-02-01

    A surface plasmon resonance (SPR) based fiber optic biosensor has been fabricated and characterized for the detection of blood glucose. Optical fiber sensor was fabricated by first coating a 50 nm thick gold film on the bare core of optical fiber and then immobilizing glucose oxidase (GOx) over it. Aqueous glucose solutions of different concentrations were prepared. To mimic the blood glucose levels, the concentration of glucose solutions were kept equal to that in human blood. The refractive indices of these sample solutions were equal to that of water up to third decimal place. SPR spectra for the sensor were recorded for these glucose solutions. When the glucose comes in contact to glucose oxidase, chemical reactions take place and as a result, the refractive index of the immobilized GOx film changes, giving rise to a shift in the resonance wavelength. Unlike electrochemical sensors, the present sensor is based on optics and can be miniaturized because of optical fiber. The present study provides a different approach for blood glucose sensing and may be commercialized after optimization of certain parameters.

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

    PubMed

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

    2015-09-17

    In this work, a novel sandwich-type electrochemical immunosensor based on host-guest interaction was fabricated for the detection of alpha-fetoprotein (AFP). Due to the large specific surface area of multiwalled carbon nanotubes and the unique supramolecular recognition ability of β-cyclodextrins, ferrocenecarboxylic acid (Fc) was incorporated into this sensor platform by host-guest interaction to generate an electrochemical signal. And β-cyclodextrins functionalized silver supported adamantine-modified glucose oxidase (GOD-CD-Ag), was used as a label to improve the analytical performance of the immunosensor by the dual amplification strategy. The obtained GOD-CD-Ag conjugates could convert glucose into gluconic acid with the formation of hydrogen peroxide (H2O2). And then silver nanoparticles could in situ catalyze the reduction of the generated H2O2, dramatically improving the oxidation reaction of Fc. The developed immunosensor shows a wide linear calibration range from 0.001 to 5.0 ng/mL with a low detection limit (0.2 pg/mL) for the detection of AFP. The method, with ideal reproducibility and selectivity, has a wide application prospect in clinical research. PMID:26398422

  2. Electrochemical immunosensor with NiAl-layered double hydroxide/graphene nanocomposites and hollow gold nanospheres double-assisted signal amplification.

    PubMed

    Qiao, Lu; Guo, Yemin; Sun, Xia; Jiao, Yancui; Wang, Xiangyou

    2015-08-01

    A sensitive electrochemical immunosensor based on NiAl-layered double hydroxide/graphene nanocomposites (NiAl-LDH/G) and hollow gold nanospheres (HGNs) was proposed for chlorpyrifos detection. The NiAl-LDH/G was prepared using a conventional coprecipitation process and reduction of the supporting graphene oxide. Subsequently, the nanocomposites were dispersed with chitosan (CS). The NiAl-LDH/G possessed good electrochemical behavior and high binding affinity to the electrode. The high surface areas of HGNs and the vast aminos and hydroxyls of CS provided a platform for the covalently crosslinking of antibody. Under optimal conditions, the immunosensor exhibited a wide linear range from 5 to 150 μg/mL and from 150 to 2 μg/mL, with a detection limit of 0.052 ng/mL. The detection results showed good agreement with standard gas chromatography method. The constructed immunosensor exhibited good reproducibility, high specificity, acceptable stability and regeneration performance, which provided a new promising tool for chlorpyrifos detection in real samples. PMID:25801002

  3. Impedimetric immunosensor for detection of cardiovascular disorder risk biomarker.

    PubMed

    Khan, Raju; Pal, Mintu; Kuzikov, Alexey V; Bulko, Tanya; Suprun, Elena V; Shumyantseva, Victoria V

    2016-11-01

    We report the construction and characterization of a novel, level free impedimetric immunosensor for rapid, sensitive and selective detection of myoglobin (Mb). Monoclonal anti-myoglobin (anti-Mb-IgG) antibody was immobilized on screen-printed multiwalled carbon nanotubes electrode for signal amplification without the need of natural enzymes. The fabrication of resulting immunosensor was extensively characterized by using scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Electrochemical impedance spectroscopy (EIS) technique offered a linear detection range (0.1-90ngmL(-1)) of myoglobin with sensitivity of 0.74kΩngmL(-1) (correlation coefficient, R(2)=0.97) and detection limit of 0.08ngmL(-1) (S/N=3). The mean percentage recovery of Mb in serum samples using this working biosensor is 97.33%. Furthermore, the proposed strategy can be a promising alternative for detection of Mb related cardiovascular disorders. PMID:27523995

  4. Basic principle of optical immunosensor using fluorescence anisotropy

    NASA Astrophysics Data System (ADS)

    Suzuki, Seiichi; Iida, Masatoshi

    1999-05-01

    An immunosensor, utilizing immobilized antibody, is a promising sensing device for its high specificity and broad spectrum for detecting object. But physical adsorption is often an obstacle for its luck of enzymatic reactions. Fluorescence anisotropy immunosensor is a method which is, in principle, free from interference of physical adsorption. In this study 3 reagents, FITC, DNS-Cl and PAS, were employed for fluorescent labeling of antibody and lifetime of fluorophore was investigated to achieve optimum sensitivity. PAS, fluorophore with longest lifetime of up to 100 ns, showed the highest sensitivity which is in accordance with the correlation time of rotational relaxation of antibody, suggesting the importance of fluorescence lifetime being comparable with the correlation time of anisotropy decay. Immobilization procedure of antibody was also investigated to reduce interference of physical adsorption. Antibody immobilized on hydrophobic surface showed substantial anisotropy change by adsorption of non-antigenic protein but antibody on hydrophilic substrate showed no detectable anisotropy change. Further improvement of experimental condition will lead to application for microanalysis or implantable sensor. For practical use of this method, fluorescence measurement with higher S/N ratio is still to be attained.

  5. Electrochemical immunosensor for detection of epidermal growth factor reaching lower detection limit: toward oxidized glutathione as a more efficient blocking reagent for the antibody functionalized silver nanoparticles and antigen interaction.

    PubMed

    Lin, Yuqing; Liu, Kangyu; Wang, Chao; Li, Linbo; Liu, Yuxin

    2015-08-18

    Blocking reagent is of vital importance for an immunosensor because it ensures the antifouling of the sensing interface and thus selective determination of the target. This Letter investigates a small inactive peptide, oxidized glutathione (GSSG), to replace the commonly used bovine serum albumin (BSA) as blocking reagent for immunosensor fabrication to lower the detection limit of electrochemical immunosensors. The EGF (epidermal growth factor) detection as an example is used here to compare the blocking effects from GSSG and BSA, respectively. The relatively big size of BSA sterically hinders EGF and antibody functionalized silver nanoparticles (Ab-AgNPs) binding. By comparison, GSSG cannot hinder EGF and Ab-AgNPs binding since it is much smaller than EGF, verified by scanning electron microscopy (SEM) results. The established GSSG blocking-based immunosensor for EGF reaches a very low detection limit of 0.01 pM, exhibits wide linearity range between 0.1 pM and 0.1 μM and is more sensitive than the BSA blocking strategy. The proposed GSSG-blocking strategy in the immunoassay paves an attractive platform for other biomolecules to reach a lower detection limit. PMID:26204199

  6. Advances in Magnetic Resonance Imaging of the Skull Base

    PubMed Central

    Kirsch, Claudia F.E.

    2014-01-01

    Introduction Over the past 20 years, magnetic resonance imaging (MRI) has advanced due to new techniques involving increased magnetic field strength and developments in coils and pulse sequences. These advances allow increased opportunity to delineate the complex skull base anatomy and may guide the diagnosis and treatment of the myriad of pathologies that can affect the skull base. Objectives The objective of this article is to provide a brief background of the development of MRI and illustrate advances in skull base imaging, including techniques that allow improved conspicuity, characterization, and correlative physiologic assessment of skull base pathologies. Data Synthesis Specific radiographic illustrations of increased skull base conspicuity including the lower cranial nerves, vessels, foramina, cerebrospinal fluid (CSF) leaks, and effacement of endolymph are provided. In addition, MRIs demonstrating characterization of skull base lesions, such as recurrent cholesteatoma versus granulation tissue or abscess versus tumor, are also provided as well as correlative clinical findings in CSF flow studies in a patient pre- and post-suboccipital decompression for a Chiari I malformation. Conclusions This article illustrates MRI radiographic advances over the past 20 years, which have improved clinicians' ability to diagnose, define, and hopefully improve the treatment and outcomes of patients with underlying skull base pathologies. PMID:25992137

  7. A highly sensitive impedimetric label free immunosensor for Ochratoxin measurement in cocoa beans.

    PubMed

    Malvano, Francesca; Albanese, Donatella; Pilloton, Roberto; Di Matteo, Marisa

    2016-12-01

    In this work the development and optimization of an impedimetric label free immunosensor for the detection of Ochratoxin A (OTA) is reported. Two antibody immobilization methods (oriented and not oriented) were compared highlighting a lower limit of detection (5pg/ml) for the not oriented immobilization but a closer linear range in contrast to oriented anti-OTA immunosensors which showed linearity in the range of 0.01-5ng/mL OTA. The analysis of the Atomic Force Microscopy (AFM) images showed two different nanostructures indicating that the use of oriented immobilization created a more ordered and highly dense antibody surface. Finally the oriented immunosensor was used to quantify OTA in spiked cocoa bean samples and the results were compared with those registered with competitive ELISA kit. The immunosensor was sensitive to OTA lower than 2μg/kg that represents the lower acceptable limit of OTA established by European legislation for the common food products. PMID:27374585

  8. Spectral separation of optical spin based on antisymmetric Fano resonances

    PubMed Central

    Piao, Xianji; Yu, Sunkyu; Hong, Jiho; Park, Namkyoo

    2015-01-01

    We propose a route to the spectral separation of optical spin angular momentum based on spin-dependent Fano resonances with antisymmetric spectral profiles. By developing a spin-form coupled mode theory for chiral materials, the origin of antisymmetric Fano spectra is clarified in terms of the opposite temporal phase shift for each spin, which is the result of counter-rotating spin eigenvectors. An analytical expression of a spin-density Fano parameter is derived to enable quantitative analysis of the Fano-induced spin separation in the spectral domain. As an application, we demonstrate optical spin switching utilizing the extreme spectral sensitivity of the spin-density reversal. Our result paves a path toward the conservative spectral separation of spins without any need of the magneto-optical effect or circular dichroism, achieving excellent purity in spin density superior to conventional approaches based on circular dichroism. PMID:26561372

  9. Evaluation of plasma-based transmit coils for magnetic resonance.

    PubMed

    Webb, A G; Aussenhofer, S A

    2015-12-01

    In this work a new concept for designing transmit coils for magnetic resonance using a plasma is introduced. Unlike conventional coils, a plasma can be turned on and off, eliminating electrical interactions between coils, and enabling radiofrequency-invisibility when desired. A surfatron has been designed to produce a surface-mode wave which propagates along the inner surface of a commercial fluorescent lighting tube. NMR spectra and images have been produced using the plasma as the transmit coil and a copper-based monopole to receive the signal. The transmit efficiency of the plasma tube was estimated, and is currently much lower than that of an equivalently-sized metal-based structure: however, there are many potential methods for increasing the efficiency using a custom-built plasma tube. PMID:26529202

  10. Optical chiral metamaterial based on the resonant behaviour of nanodiscs

    NASA Astrophysics Data System (ADS)

    Kordi, Mahdi; Mojtaba Mirsalehi, Mir

    2016-08-01

    Circular dichorism and optical activity have been achieved by chiral metamaterials in the optical spectrum, but for the case of negative index of refraction, remarkable achievements have not been obtained in this region so far. We employ nanoparticles to shift the resonant frequency of a chiral metamaterial based on twisted cross wires to optical domain. Our proposed structure provides giant optical activity, strong circular dichorism and also negative refractive index in the optical wavelengths. Optical activity in our structure has a rotary power similar to a gyrotropic crystal of quartz, but in a thickness which is four orders of magnitude smaller. The foundation of our method for realizing such an optical chiral metamaterial is based on creating a different coupling between longitudinal modes of localized surface plasmons for right and left circularly polarized incident waves.

  11. Whispering gallery mode resonators based on radiation-sensitive materials

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy (Inventor); Maleki, Lutfollah (Inventor); Ilchenko, Vladimir (Inventor); Handley, Timothy A. (Inventor)

    2005-01-01

    Whispering gallery mode (WGM) optical resonators formed of radiation-sensitive materials to allow for permanent tuning of their resonance frequencies in a controlled manner. Two WGM resonators may be cascaded to form a composite filter to produce a second order filter function where at least one WGM resonator is formed a radiation-sensitive material to allow for proper control in the overlap of the two filter functions.

  12. Terahertz carpet cloak based on a ring resonator metasurface

    NASA Astrophysics Data System (ADS)

    Orazbayev, B.; Mohammadi Estakhri, N.; Beruete, M.; Alù, A.

    2015-05-01

    In this work we present the concept and design of an ultrathin (λ/22) terahertz (THz) unidirectional carpet cloak based on the local phase compensation approach enabled by gradient metasurfaces. A triangular surface bump with center height of 4.1 mm (1.1λ) and tilt angle of 20° is covered with a metasurface composed of an array of suitably designed closed ring resonators with a transverse gradient of surface impedance. The ring resonators provide a wide range of control for the reflection phase with small absorption losses, enabling efficient phase manipulation along the edge of the bump. Our numerical results demonstrate a good performance of the designed cloak in both near field and far field, and the cloaked object mimics a flat ground plane within a broad range of incidence angles, over 35° angular spectrum centered at 45°. The presented cloak design can be applied in radar and antenna systems as a thin, lightweight, and easy to fabricate solution for radio and THz frequencies.

  13. Biosensing based on surface plasmon resonance and living cells.

    PubMed

    Chabot, Vincent; Cuerrier, Charles M; Escher, Emanuel; Aimez, Vincent; Grandbois, Michel; Charette, Paul G

    2009-02-15

    We propose the combination of surface plasmon resonance (SPR) with living cells as a biosensing method. Our detection scheme is based on the premise that cellular activity induced by external agents is often associated with changes in cellular morphology, which in turn should lead to a variation of the effective refractive index at the interface between the cell membrane and the metal layer. We monitored surface plasmon resonance signals originating from a gold surface coated with cells on a custom apparatus after injection of various agents known to influence cellular activity and morphology. Specifically, we evaluated three types of stimulation: response to an endotoxin (lipopolysaccharides), a chemical toxin (sodium azide) and a physiological agonist (thrombin). A comparison with phase contrast microscopy reveals that SPR signal variations are associated with the induction of cell death for lipopolysaccharides treatment and a contraction of the cell body for sodium azide. Thrombin-induced cellular response shows a rapid decrease of the measured laser reflectance over 5min followed by a return to the original value. For this treatment, phase contrast micrographs relate the first phase of the SPR variation to cell contraction and increase of the intercellular gaps, whereas the recovery phase can be associated with a spreading of the cell on the sensing surface. Hence, the SPR signal is very consistent with the cellular response normally observed for these treatments. This confirms the validity of the biosensing method, which could be applied to a large variety of cellular responses involving shape remodeling induced by external agents. PMID:18845432

  14. Magnetic Resonance Based Diagnostics for Polymer Production and Surveillance

    SciTech Connect

    Chinn, S; Herberg, J; Gjersing, E; Cook, A; Sawvel, A M; Maxwell, R; Wheeler, H; Wilson, M

    2006-09-27

    In an effort to develop a magnetic resonance based diagnostic tool to be used for polymer production and surveillance, we have investigated the use of magnetic resonance imaging (MRI) and unilateral relaxometry. MRI provides a spatial map of the polymer, which can be correlated to the structure heterogeneity. Though highly detailed information can be obtained with MRI, the high equipment cost and expertise required to operate the system makes it a poor choice for a production setting. Unilateral relaxometry via the NMR MOUSE provides rapid, inexpensive polymer screening, useful in the development in new polymer parts or to identify potentially defective components. The NMR ProFiler (originally called the NMR MOUSE) was procured by Kansas City originally for production support of the W80 LEP with future applications as a surveillance diagnostic. A robotic autosampler has been designed allowing the detection of several components without the need for any human interaction. A summary of the qualification experiments and results to date from the ProFiler and the robotic unit will be presented.

  15. Resonance Raman based skin carotenoid measurements in newborns and infants

    PubMed Central

    Ermakov, Igor V.; Ermakova, Maia R.; Bernstein, Paul S.; Chan, Gary M.; Gellermann, Werner

    2014-01-01

    We describe Resonance Raman based skin carotenoid measurements in newborns and infants. Skin- and serum carotenoid levels correlate with high statistical significance in healthy newborns and infants, and with reduced accuracy also in prematurely born infants, who in general feature very low carotenoid levels and thin transparent skin giving rise to large background absorption effects. Skin carotenoid levels can be easily compared among subjects and/or tracked in longitudinal studies with the highly molecule-specific Raman method. It therefore holds promise as a rapid, non-invasive, carotenoid antioxidant assessment method for newborns and infants in the field of pediatrics. Photograph of an infant’s skin carotenoid measurement via Resonance Raman spectroscopy. The instrument’s fiber-coupled light delivery and collection module is held against the foot, exposing the heel skin to weak 488 nm laser light for 20 seconds. From spectral analysis of the Raman scattered light intensities, which occur in the green wavelength region, the carotenoid levels in the heel skin are obtained in a rapid, non-invasive, and painless fashion. PMID:23193015

  16. Resonant Magnetic Field Sensors Based On MEMS Technology.

    PubMed

    Herrera-May, Agustín L; Aguilera-Cortés, Luz A; García-Ramírez, Pedro J; Manjarrez, Elías

    2009-01-01

    Microelectromechanical systems (MEMS) technology allows the integration of magnetic field sensors with electronic components, which presents important advantages such as small size, light weight, minimum power consumption, low cost, better sensitivity and high resolution. We present a discussion and review of resonant magnetic field sensors based on MEMS technology. In practice, these sensors exploit the Lorentz force in order to detect external magnetic fields through the displacement of resonant structures, which are measured with optical, capacitive, and piezoresistive sensing techniques. From these, the optical sensing presents immunity to electromagnetic interference (EMI) and reduces the read-out electronic complexity. Moreover, piezoresistive sensing requires an easy fabrication process as well as a standard packaging. A description of the operation mechanisms, advantages and drawbacks of each sensor is considered. MEMS magnetic field sensors are a potential alternative for numerous applications, including the automotive industry, military, medical, telecommunications, oceanographic, spatial, and environment science. In addition, future markets will need the development of several sensors on a single chip for measuring different parameters such as the magnetic field, pressure, temperature and acceleration. PMID:22408480

  17. Resonant Magnetic Field Sensors Based On MEMS Technology

    PubMed Central

    Herrera-May, Agustín L.; Aguilera-Cortés, Luz A.; García-Ramírez, Pedro J.; Manjarrez, Elías

    2009-01-01

    Microelectromechanical systems (MEMS) technology allows the integration of magnetic field sensors with electronic components, which presents important advantages such as small size, light weight, minimum power consumption, low cost, better sensitivity and high resolution. We present a discussion and review of resonant magnetic field sensors based on MEMS technology. In practice, these sensors exploit the Lorentz force in order to detect external magnetic fields through the displacement of resonant structures, which are measured with optical, capacitive, and piezoresistive sensing techniques. From these, the optical sensing presents immunity to electromagnetic interference (EMI) and reduces the read-out electronic complexity. Moreover, piezoresistive sensing requires an easy fabrication process as well as a standard packaging. A description of the operation mechanisms, advantages and drawbacks of each sensor is considered. MEMS magnetic field sensors are a potential alternative for numerous applications, including the automotive industry, military, medical, telecommunications, oceanographic, spatial, and environment science. In addition, future markets will need the development of several sensors on a single chip for measuring different parameters such as the magnetic field, pressure, temperature and acceleration. PMID:22408480

  18. Piezometric biosensors for anti-apoptotic protein survivin based on buried positive-potential barrier and immobilized monoclonal antibodies.

    PubMed

    Stobiecka, Magdalena; Chalupa, Agata; Dworakowska, Beata

    2016-10-15

    The anti-apoptotic protein survivin (Sur) plays an important role in the regulation of cell division and inducing the chemotherapeutic drug resistance. The Sur protein and its mRNA have recently been studied as cancer biomarkers and potential targets for cancer therapy. In this work, we have focused on the design of immunosensors for the detection of Sur based on buried positive-potential barrier layer structure and anti-survivin antibody. The modification of solid AuQC piezoelectrodes was monitored by recording the resonance frequency shift and electrochemical measurements during each step of the sensor preparation. Our results indicate that the immunosensor with covalently bound monoclonal anti-survivin antibody can detect Sur with the limit of detection, LOD=1.7nM (S/N=3σ). The immunosensor applicability for the analysis of real samples was assessed by testing samples of cell lysate solutions obtained from human astrocytoma (glioblastoma) U-87MG cell line, with the experiments performed using the standard addition method. The good linearity of the calibration curves for PBS and lysate solutions at low Sur concentrations confirm the high specificity of the proposed biosensor and good discrimination against nonspecific interactions with lysate components. The calculations indicate that there is still room to increase the Sur capture capacity for Sur while miniaturizing the sensor. The important advantage of the sensor is that it can be reused by a simple regeneration procedure. PMID:26507667

  19. Total internal reflection mirror-based ultra-sensitive triangular ring resonator sensor on the surface plasmon resonance condition

    NASA Astrophysics Data System (ADS)

    Kim, Hong-Seung; Kim, Tae-Ryong; Kim, Doo-Gun; Choi, Young-Wan

    2015-02-01

    In this paper, we have theoretically analyzed using a finite-difference time domain (FDTD) methods and realized a high sensitive triangular ring resonator sensor based on the total internal reflection (TIR) mirror with a thin metal film for surface plasmon resonance (SPR) phenomenon. One of advantages is a high sensitivity with large phase variation at TIR mirror facet with SPR. Previously, the sensing region of the general ring resonator sensor is located on the cladding region or upper core region. However, the triangular ring resonator has a very high sensitivity using the sensing region of the TIR mirror facet, because the length of the evanescent field at TIR mirror is longer than the evanescent field length at the cladding region. Another is a high Q-factor by the round-trip loss compensation through an active medium in the waveguide. Proposed sensor also has an integrated light source using an InP-based semiconductor optical amplifier. The sensitivity of triangular ring resonator with SPR is extremely enhanced by large phase shift at TIR mirror facet on SPR. Optimized metal thickness is a 33.4 nm at the SPR angle of 22.92 degree. The simulation result of the sensitivity for the triangular ring resonator sensor with SPR is 4.2×104 nm/RIU using by FDTD method. To measure the biosensor, we used an antigen/antibody reaction.

  20. Monaural sound localization based on structure-induced acoustic resonance.

    PubMed

    Kim, Keonwook; Kim, Youngwoong

    2015-01-01

    A physical structure such as a cylindrical pipe controls the propagated sound spectrum in a predictable way that can be used to localize the sound source. This paper designs a monaural sound localization system based on multiple pyramidal horns around a single microphone. The acoustic resonance within the horn provides a periodicity in the spectral domain known as the fundamental frequency which is inversely proportional to the radial horn length. Once the system accurately estimates the fundamental frequency, the horn length and corresponding angle can be derived by the relationship. The modified Cepstrum algorithm is employed to evaluate the fundamental frequency. In an anechoic chamber, localization experiments over azimuthal configuration show that up to 61% of the proper signal is recognized correctly with 30% misfire. With a speculated detection threshold, the system estimates direction 52% in positive-to-positive and 34% in negative-to-positive decision rate, on average. PMID:25668214

  1. Monaural Sound Localization Based on Structure-Induced Acoustic Resonance

    PubMed Central

    Kim, Keonwook; Kim, Youngwoong

    2015-01-01

    A physical structure such as a cylindrical pipe controls the propagated sound spectrum in a predictable way that can be used to localize the sound source. This paper designs a monaural sound localization system based on multiple pyramidal horns around a single microphone. The acoustic resonance within the horn provides a periodicity in the spectral domain known as the fundamental frequency which is inversely proportional to the radial horn length. Once the system accurately estimates the fundamental frequency, the horn length and corresponding angle can be derived by the relationship. The modified Cepstrum algorithm is employed to evaluate the fundamental frequency. In an anechoic chamber, localization experiments over azimuthal configuration show that up to 61% of the proper signal is recognized correctly with 30% misfire. With a speculated detection threshold, the system estimates direction 52% in positive-to-positive and 34% in negative-to-positive decision rate, on average. PMID:25668214

  2. APPLICATIONS OF ELECTROCHEMICAL IMMUNOSENSORS TO ENVIRONMENTAL MONITORING

    EPA Science Inventory

    This paper discusses basic electrochemical immunoassay technology. Factors limiting the practical application of antibodies to anlaytical problems are also presented. It addresses the potential use of immunoassay methods based on electrochemical detection for the analysis of env...

  3. Multiple magnetic mode-based Fano resonance in split-ring resonator/disk nanocavities.

    PubMed

    Zhang, Qing; Wen, Xinglin; Li, Guangyuan; Ruan, Qifeng; Wang, Jianfang; Xiong, Qihua

    2013-12-23

    Plasmonic Fano resonance, enabled by the weak interaction between a bright super-radiant and a subradiant resonance mode, not only is fundamentally interesting, but also exhibits potential applications ranging from extraordinary optical transmission to biosensing. Here, we demonstrate strong Fano resonances in split-ring resonators/disk (SRR/D) nanocavities. The high-order magnetic modes are observed in SRRs by polarization-resolved transmission spectroscopy. When a disk is centered within the SRRs, multiple high-order magnetic modes are coupled to a broad electric dipole mode of SRR/D, leading to significant Fano resonance spectral features in near-IR regime. The strength and line shape of the Fano resonances are tuned through varying the SRR split-angle and interparticle distance between SRR and disk. Finite-difference-time-domain (FDTD) simulations are conducted to understand the coupling mechanism, and the results show good agreement with experimental data. Furthermore, the coupled structure gives a sensitivity of ∼282 nm/RIU with a figure of merit ∼4. PMID:24215162

  4. Cancellation of environmental effects in resonant mass sensors based on resonance mode and effective mass

    SciTech Connect

    Naeli, Kianoush; Brand, Oliver

    2009-06-15

    A novel technique is developed to cancel the effect of environmental parameters, e.g., temperature and humidity, in resonant mass sensing. Utilizing a single resonator, the environmental cancellation is achieved by monitoring a pair of resonant overtones and the effective sensed mass in those overtones. As an eminent advantage, especially compared to dual-mode temperature compensation techniques, the presented technique eliminates any need for previously measured look-up tables or fitting the measurement data. We show that a resonant cantilever beam is an appropriate platform for applying this technique, and derive an analytical expression to relate the actual and effective sensed masses on a cantilever beam. Thereby, it is shown that in applying the presented technique successfully, the effective sensed masses must not be the same in the investigated pair of resonance overtones. To prove the feasibility of the proposed technique, flexural resonance frequencies of a silicon cantilever are measured before and after loading with a strip of photoresist. Applying the presented technique shows significant reductions in influence of environmental parameters, with the temperature and humidity coefficients of frequency being improved from -19.5 to 0.2 ppm deg. C{sup -1} and from 0.7 to -0.03 ppm %RH{sup -1}, respectively.

  5. Surface Plasmon Resonance Biosensor Based on Smart Phone Platforms

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Liu, Qiang; Chen, Shimeng; Cheng, Fang; Wang, Hanqi; Peng, Wei

    2015-08-01

    We demonstrate a fiber optic surface plasmon resonance (SPR) biosensor based on smart phone platforms. The light-weight optical components and sensing element are connected by optical fibers on a phone case. This SPR adaptor can be conveniently installed or removed from smart phones. The measurement, control and reference channels are illuminated by the light entering the lead-in fibers from the phone’s LED flash, while the light from the end faces of the lead-out fibers is detected by the phone’s camera. The SPR-sensing element is fabricated by a light-guiding silica capillary that is stripped off its cladding and coated with 50-nm gold film. Utilizing a smart application to extract the light intensity information from the camera images, the light intensities of each channel are recorded every 0.5 s with refractive index (RI) changes. The performance of the smart phone-based SPR platform for accurate and repeatable measurements was evaluated by detecting different concentrations of antibody binding to a functionalized sensing element, and the experiment results were validated through contrast experiments with a commercial SPR instrument. This cost-effective and portable SPR biosensor based on smart phones has many applications, such as medicine, health and environmental monitoring.

  6. Surface Plasmon Resonance Biosensor Based on Smart Phone Platforms.

    PubMed

    Liu, Yun; Liu, Qiang; Chen, Shimeng; Cheng, Fang; Wang, Hanqi; Peng, Wei

    2015-01-01

    We demonstrate a fiber optic surface plasmon resonance (SPR) biosensor based on smart phone platforms. The light-weight optical components and sensing element are connected by optical fibers on a phone case. This SPR adaptor can be conveniently installed or removed from smart phones. The measurement, control and reference channels are illuminated by the light entering the lead-in fibers from the phone's LED flash, while the light from the end faces of the lead-out fibers is detected by the phone's camera. The SPR-sensing element is fabricated by a light-guiding silica capillary that is stripped off its cladding and coated with 50-nm gold film. Utilizing a smart application to extract the light intensity information from the camera images, the light intensities of each channel are recorded every 0.5 s with refractive index (RI) changes. The performance of the smart phone-based SPR platform for accurate and repeatable measurements was evaluated by detecting different concentrations of antibody binding to a functionalized sensing element, and the experiment results were validated through contrast experiments with a commercial SPR instrument. This cost-effective and portable SPR biosensor based on smart phones has many applications, such as medicine, health and environmental monitoring. PMID:26255778

  7. Surface Plasmon Resonance Biosensor Based on Smart Phone Platforms

    PubMed Central

    Liu, Yun; Liu, Qiang; Chen, Shimeng; Cheng, Fang; Wang, Hanqi; Peng, Wei

    2015-01-01

    We demonstrate a fiber optic surface plasmon resonance (SPR) biosensor based on smart phone platforms. The light-weight optical components and sensing element are connected by optical fibers on a phone case. This SPR adaptor can be conveniently installed or removed from smart phones. The measurement, control and reference channels are illuminated by the light entering the lead-in fibers from the phone’s LED flash, while the light from the end faces of the lead-out fibers is detected by the phone’s camera. The SPR-sensing element is fabricated by a light-guiding silica capillary that is stripped off its cladding and coated with 50-nm gold film. Utilizing a smart application to extract the light intensity information from the camera images, the light intensities of each channel are recorded every 0.5 s with refractive index (RI) changes. The performance of the smart phone-based SPR platform for accurate and repeatable measurements was evaluated by detecting different concentrations of antibody binding to a functionalized sensing element, and the experiment results were validated through contrast experiments with a commercial SPR instrument. This cost-effective and portable SPR biosensor based on smart phones has many applications, such as medicine, health and environmental monitoring. PMID:26255778

  8. Novel localized surface plasmon resonance based optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Muri, Harald Ian D. I.; Hjelme, Dag R.

    2016-03-01

    Over the last decade various optical fiber sensing schemes have been proposed based on local surface plasmon resonance (LSPR). LSPR are interacting with the evanescent field from light propagating in the fiber core or by interacting with the light at the fiber end face. Sensor designs utilizing the fiber end face is strongly preferred from a manufacturing point of view. However, the different techniques available to immobilize metallic nanostructures on the fiber end face for LSPR sensing is limited to essentially a monolayer, either by photolithographic structuring of metal film, thermal nucleation of metal film, or by random immobilization of nanoparticles (NP). In this paper, we report on a novel LSPR based optical fiber sensor architecture. The sensor is prepared by immobilizing gold NP's in a hydrogel droplet polymerized on the fiber end face. This design has several advantages over earlier designs. It dramatically increase the number of NP's available for sensing, it offers precise control over the NP density, and the NPs are position in a true 3D aqueous environment. The sensor design is also compatible with low cost manufacturing. The sensor design can measure volumetric changes in a stimuli-responsive hydrogel or measure binding to receptors on the NP surface. It can also be used as a two-parameter sensor by utilizing both effects. We present results from proof-of-concept experiments demonstrating a pH sensor based on LSPR sensing in a poly(acrylamide-co-acrylic acid) hydrogel embedding gold nanoparticles.

  9. Planar terahertz waveguides based on complementary split ring resonators.

    PubMed

    Kumar, Gagan; Cui, Albert; Pandey, Shashank; Nahata, Ajay

    2011-01-17

    We experimentally demonstrate planar plasmonic THz waveguides using metal films that are periodically perforated with complementary split ring resonators (CSRRs). The waveguide transmission spectra exhibit numerous transmission resonances. While the geometry is commonly used in developing negative index materials, the excitation geometry used here does not allow for conventional metamaterial response. Instead, we show that all of the observed resonances can be determined from the geometrical properties of the CSRR apertures. Surprisingly, the Bragg condition does not appear to limit the frequency extent of the observed resonances. The results suggest that metamaterial-inspired geometries may be useful for developing THz guided-wave devices. PMID:21263646

  10. Electrochemical immunosensors for the simultaneous detection of two tumor markers.

    PubMed

    Wilson, Michael S

    2005-03-01

    The microfabrication of electrochemical immunosensors for the simultaneous detection of two protein analytes is described. The sensors consisted of two iridium oxide electrodes (1-mm diameter) patterned on a glass substrate. Capture antibodies were immobilized on the porous iridium oxide electrodes by covalent attachment using (3-aminopropyl)triethoxysilane and glutaraldehyde. The spatial separation of the electrodes (2.5 mm) enabled simultaneous electrochemical immunoassays to be conducted without cross-talk between the electrodes. Proteins were measured using electrochemical ELISA, and detection was achieved by electrochemically oxidizing alkaline phosphatase-generated hydroquinone. Sensors for the simultaneous detection of goat IgG and mouse IgG, and for the tumor markers CEA and AFP, were developed. The sensors had detection limits of 1, 2, 1.2, and 1 ng/mL for goat IgG, mouse IgG, CEA, and AFP, respectively. PMID:15732936

  11. Cellulose antibody films for highly specific evanescent wave immunosensors

    NASA Astrophysics Data System (ADS)

    Hartmann, Andreas; Bock, Daniel; Jaworek, Thomas; Kaul, Sepp; Schulze, Matthais; Tebbe, H.; Wegner, Gerhard; Seeger, Stefan

    1996-01-01

    For the production of recognition elements for evanescent wave immunosensors optical waveguides have to be coated with ultrathin stable antibody films. In the present work non amphiphilic alkylated cellulose and copolyglutamate films are tested as monolayer matrices for the antibody immobilization using the Langmuir-Blodgett technique. These films are transferred onto optical waveguides and serve as excellent matrices for the immobilization of antibodies in high density and specificity. In addition to the multi-step immobilization of immunoglobulin G(IgG) on photochemically crosslinked and oxidized polymer films, the direct one-step transfer of mixed antibody-polymer films is performed. Both planar waveguides and optical fibers are suitable substrates for the immobilization. The activity and specificity of immobilized antibodies is controlled by the enzyme-linked immunosorbent assay (ELISA) technique. As a result reduced non-specific interactions between antigens and the substrate surface are observed if cinnamoylbutyether-cellulose is used as the film matrix for the antibody immobilization. Using the evanescent wave senor (EWS) technology immunosensor assays are performed in order to determine both the non-specific adsorption of different coated polymethylmethacrylat (PMMA) fibers and the long-term stability of the antibody films. Specificities of one-step transferred IgG-cellulose films are drastically enhanced compared to IgG-copolyglutamate films. Cellulose IgG films are used in enzymatic sandwich assays using mucine as a clinical relevant antigen that is recognized by the antibodies BM2 and BM7. A mucine calibration measurement is recorded. So far the observed detection limit for mucine is about 8 ng/ml.

  12. Gold and aluminum based surface plasmon resonance biosensors: sensitivity enhancement

    NASA Astrophysics Data System (ADS)

    Biednov, Mykola; Lebyedyeva, Tetyana; Shpylovyy, Pavlo

    2015-05-01

    In this work we considered Gold and Aluminum thin films coated with additional dielectric layers as sensing platforms. Operation of these sensors is based on measuring shift in the position of the reflectivity dip in angular reflectivity spectrum of the sample. Shift can be caused by changes in the refraction index of either liquid that interacts with sensors surface (refractometric measurements) or thin adjacent biolayer on top of the sensor due to immobilization of the target molecules (biosensing). Calculations based on Fresnel equations and transfer matrix formalism allowed us to make comprehensive analysis of the angular sensitivity, shape of the reflectivity dip and dynamic range of the sensors with different dielectric coatings. Calculations were performed for both cases of bio and refractometric sensing. Results showed different dependence of the sensitivity of Au an Al based sensors upon refraction index of the dielectric coating. For Au-based surface Plasmon resonance sensor up to two times increased sensitivity can be achieved using dielectric coating with high refraction index 2.3 of proper thickness. For sensors based on aluminum we were able to achieve 50% increased angular sensitivity. At the same time width of the reflectivity dip increased proportionally to the optical thickness of the dielectric coating. For estimating sensors quality we analyzed ratio of the angular sensitivity to the width of the reflectivity dip. This ratio decreased with increase in optical thickness of the dielectric, however angular sensitivity of the sensor increased significantly. Deposition of the additional dielectric layer with high refraction index such as Niobium Oxide can also improve chemical and mechanical stability of the sensor.

  13. Dielectric resonator-based resonant structure for sensitive ESR measurements at high-hydrostatic pressures.

    PubMed

    Sienkiewicz, Andrzej; Vileno, Bertrand; Garaj, Slaven; Jaworski, Marek; Forró, László

    2005-12-01

    We present a newly developed microwave probe head that accommodates a gasketed sapphire anvil cell (SAC) for performing sensitive electron spin resonance (ESR) measurements under high-hydrostatic pressures. The system was designed around commercially available dielectric resonators (DRs) having the dielectric permittivity of approximately 30. The microwave resonant structure operates in a wide-stretched double-stacked geometry and resonates in the lowest cylindrical quasi TE(011) mode around 9.2 GHz. The most vital parts of the probe's microwave heart were made of plastic materials, thus making the resonant structure transparent to magnetic field modulation at 100 kHz. The overall ESR sensitivity of the probe was demonstrated for a small speck of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) positioned in the gasket of the SAC, using water as the pressure-transmitting medium. The system was also used for studying pressure-induced changes in spin-relaxation mechanisms of a quasi-1D-conducting polymer, K(1)C(60). For small samples located in the sample hole of the gasket the probe reveals sensitivity that is only approximately 3 times less than that yielded by regular ESR cavities. PMID:16168687

  14. Development of a faradic impedimetric immunosensor for the detection of Salmonella typhimurium in milk.

    PubMed

    Mantzila, Aikaterini G; Maipa, Vassiliki; Prodromidis, Mamas I

    2008-02-15

    The development of a faradic impedimetric immunosensor for the detection of S. typhimurium in milk is described for first time. Polyclonal anti-Salmonella was cross-linked, in the presence of glutaraldehyde, on gold electrodes modified with a single 11-amino-1-undecanethiol (MUAM) self-assembled monolayer (SAM) or a mixed SAM of MUAM and 6-mercapto-1-hexanol at a constant 1 + 3 proportion, respectively. The mixed SAM was also deposited in the presence of triethylamine, which was used to prevent the formation of interplane hydrogen bonds among amine-terminated thiols. The effect of the different surface modifications on both the sensitivity and the selectivity of the immunosensors was investigated. The alteration of the interfacial features of the electrodes due to different modification or recognition steps, was measured by faradic electrochemical impedance spectroscopy in the presence of a hexacyanoferrate(II)/(III) redox couple. A substantial amplification of the measuring signal was achieved by performing the immunoreaction directly in culture samples. This resulted in immunosensors with great analytical features, as follows: (i) high sensitivity; the response of the immunosensors increases with respect to the detection time as a consequence of the simultaneous proliferation of the viable bacteria cells in the tested samples; (ii) validity; the response of the immunosensors is practically insensitive to the presence of dead cells; (iii) working simplicity; elimination of various centrifugation and washing steps, which are used for the isolation of bacteria cells from the culture. The proposed immunosensors were successfully used for the detection of S. typhimurium in experimentally inoculated milk samples. The effect of different postblocking agents on the performance of the immunosensors in real samples was also examined. PMID:18217725

  15. Dual-band terahertz metamaterials based on nested split ring resonators

    NASA Astrophysics Data System (ADS)

    Hussain, Sajid; Min Woo, Jeong; Jang, Jae-Hyung

    2012-08-01

    Two dual-band terahertz metamaterials based on nested split ring resonators (SRRs) were designed and fabricated on a flexible plastic substrate. Each nested SRR structure composed of two electric field coupled resonators exhibited two transmission minimums, which inherently come from the LC resonances of the respective SRRs. The primary and secondary resonance frequencies can be individually fine-tuned by adjusting the geometry of the respective resonator. The fabricated devices exhibited very low insertion loss of 3 dB in the transmission band and the high attenuation of 27 dB in the stop band.

  16. Surface plasmon resonance sensor based on spectral interferometry: numerical analysis.

    PubMed

    Zhang, Yunfang; Li, Hui; Duan, Jingyuan; Shi, Ancun; Liu, Yuliang

    2013-05-10

    In this paper, we introduce a numerical simulation of a phase detecting surface plasmon resonance (SPR) scheme based on spectral interference. Based on the simulation, we propose a method to optimize various aspects of SPR sensors, which enables better performance in both measurement range (MR) and sensitivity. In the simulation, four parameters including the spectrum of the broadband light source, incident angle, Au film thickness, and refractive index of the prism coupler are analyzed. The results show that it is a good solution for better performance to use a warm white broadband (625-800 nm) light source, a divergence angle of the collimated incident light less than 0.02°, and an optimized 48 nm thick Au film when a visible broadband light source is used. If a near-IR light source is used, however, the Au film thickness should be somewhat thinner according the specific spectrum. In addition, a wider MR could be obtained if a prism coupler with higher refractive index is used. With all the parameters appropriately set, the SPR MR could be extended to 0.55 refractive index units while keeping the sensitivity at a level of 10(-8). PMID:23669838

  17. Protein Based Localized Surface Plasmon Resonance Gas Sensing

    NASA Astrophysics Data System (ADS)

    Meisam, Omidi; Gh., Amoabediny; Yazdian, F.; Habibi-Rezaei, M.

    2015-01-01

    We apply the localized surface plasmon resonance (LSPR) of gold nanoparticles (GNPs) covalently coupled with cytochrome c (cyt c) to create a nanobiosensor for detecting hydrogen sulfide (H2S) in the range of 15-100 ppb. Monolayer formation of GNPs on glass surface functionalized with 3-aminopropyltrimethoxysilane (APTMS) is performed for fabricating a chip-based format of the optical transducer. By chemical introduction of short-chain thiol derivatives on cyt c protein shell via its lysine residues, a very fast self-assembled monolayer (SAM) of cyt c is formed on the GNPs. Significant shifts in the LSPR peak (ΔλLSPR) are observed by reacting H2S with cyt c. Results show a linear relationship between ΔλLSPR and H2S concentration. Furthermore, shifts in the LSPR peak are reversible and the peak positions return to their pre-exposure values once the H2S is removed. The experimental results strongly indicate that the protein based LSPR chip can be successfully used as a simple, fast, sensitive and quantitative sensor for H2S detection.

  18. Gallium arsenide based surface plasmon resonance for glucose monitoring

    NASA Astrophysics Data System (ADS)

    Patil, Harshada; Sane, Vani; Sriram, G.; Indumathi, T. S; Sharan, Preeta

    2015-07-01

    The recent trends in the semiconductor and microwave industries has enabled the development of scalable microfabrication technology which produces a superior set of performance as against its counterparts. Surface Plasmon Resonance (SPR) based biosensors are a special class of optical sensors that become affected by electromagnetic waves. It is found that bio-molecular recognition element immobilized on the SPR sensor surface layer reveals a characteristic interaction with various sample solutions during the passage of light. The present work revolves around developing painless glucose monitoring systems using fluids containing glucose like saliva, urine, sweat or tears instead of blood samples. Non-invasive glucose monitoring has long been simulated using label free detection mechanisms and the same concept is adapted. In label-free detection, target molecules are not labeled or altered, and are detected in their natural forms. Label-free detection mechanisms involves the measurement of refractive index (RI) change induced by molecular interactions. These interactions relates the sample concentration or surface density, instead of total sample mass. After simulation it has been observed that the result obtained is highly accurate and sensitive. The structure used here is SPR sensor based on channel waveguide. The tools used for simulation are RSOFT FULLWAVE, MEEP and MATLAB etc.

  19. Ultralow-phase-noise oscillators based on BAW resonators.

    PubMed

    Li, Mingdong; Seok, Seonho; Rolland, Nathalie; Rolland, Paul; El Aabbaoui, Hassan; de Foucauld, Emeric; Vincent, Pierre; Giordano, Vincent

    2014-06-01

    This paper presents two 2.1-GHz low-phase noise oscillators based on BAW resonators. Both a single-ended common base structure and a differential Colpitts structure have been implemented in a 0.25-μm BiCMOS process. The detailed design methods including the realization, optimization, and test are reported. The differential Colpitts structure exhibits a phase noise 6.5 dB lower than the single-ended structure because of its good performance of power noise immunity. Comparison between the two structures is also carried out. The differential Colpitts structure shows a phase noise level of -87 dBc/Hz at 1-kHz offset frequency and a phase noise floor of -162 dBc/Hz, with an output power close to -6.5 dBm and a core consumption of 21.6 mW. Furthermore, with the proposed optimization methods, both proposed devices have achieved promising phase noise performance compared with state-of-the-art oscillators described in the literature. Finally, we briefly present the application of the proposed BAW oscillator to a micro-atomic clock. PMID:24859654

  20. Dual-band microwave duplexer based on spiral resonators (SR) and complementary split ring resonators (CSRR)

    NASA Astrophysics Data System (ADS)

    Vélez, A.; Sisó, G.; Campo, A.; Durán-Sindreu, M.; Bonache, J.; Martín, F.

    2011-06-01

    In this work, a microstrip dual-band microwave duplexer implemented by means of a pair of dual-band branch-line hybrid couplers and a pair of dual-band band-stop filters is presented. The hybrid couplers are implemented by using complementary split ring resonators (CSRRs), etched in the ground plane, while the band-stop filters are made of spiral resonators (SRs) coupled to the host line. The measured duplexer characteristics are good and the device is compact by virtue of the small electrical size of the employed resonant elements. From this paper, it is clear that CSRRs and SRs are useful particles for the design of dual-band microwave systems requiring various microwave components.

  1. The future of magnetic resonance-based techniques in neurology.

    PubMed

    2001-01-01

    Magnetic resonance techniques have become increasingly important in neurology for defining: 1. brain, spinal cord and peripheral nerve or muscle structure; 2. pathological changes in tissue structures and properties; and 3. dynamic patterns of functional activation of the brain. New applications have been driven in part by advances in hardware, particularly improvements in magnet and gradient coil design. New imaging strategies allow novel approaches to contrast with, for example, diffusion imaging, magnetization transfer imaging, perfusion imaging and functional magnetic resonance imaging. In parallel with developments in hardware and image acquisition have been new approaches to image analysis. These have allowed quantitative descriptions of the image changes to be used for a precise, non-invasive definition of pathology. With the increasing capabilities and specificity of magnetic resonance techniques it is becoming more important that the neurologist is intimately involved in both the selection of magnetic resonance studies for patients and their interpretation. There is a need for considerably improved access to magnetic resonance technology, particularly in the acute or intensive care ward and in the neurosurgical theatre. This report illustrates several key developments. The task force concludes that magnetic resonance imaging is a major clinical tool of growing significance and offers recommendations for maximizing the potential future for magnetic resonance techniques in neurology. PMID:11509077

  2. [Fluorescent and Magnetic Relaxation Switch Immunosensor for the Detecting Foodborne Pathogen Salmonella enterica in Water Samples].

    PubMed

    Wang, Song-bai; Zhang, Yan; An, Wen-ting; Wei, Yan-li; Wang, Yu; Shuang, Shao-min

    2015-11-01

    Fluoroimmunoassay based on quantum dots (QDs) and magnetic relaxation switch (MRS) immunoassay based on superparamagnetic nanoparticles (SMN) were constructed to detect Salmonella enterica (S. enterica) in water samples. In fluoroimmunoassay, magnetic beads was conjugated with S. enterica capture antibody (MB-Ab2) to enrich S. enterica from sample solution, then the QDs was conjugated with the S. enterica detection antibody (QDs-Ab1) to detect S. enterica based on sandwich immunoassay format. And the fluorescence intensity is positive related to the bacteria concentration of the sample. Results showed that the limit of detection (LOD) of this method was 102 cfu · mL⁻¹ and analysis time was 2 h. In MRS assay, magnetic nanoparticle-antibody conjugate (MN-Ab1) can switch their dispersed and aggregated state in the presence of the target. This state of change can modulate the spin-spin relaxation time (T₂) of the neighboring water molecule. The change in T₂(ΔT₂) positively correlates with the amount of the target in the sample. Thus, AT can be used as a detection signal in MRS immunosensors. Results showed that LOD of MRS sensor for S. enterica was 10³ cfu · mL⁻¹ and analysis time was 0.5 h. Two methods were compared in terms of advantages and disadvantages in detecting S. enterica. PMID:26978918

  3. Backscattering analysis in optical micro-resonators with mode splitting based on COMSOL

    NASA Astrophysics Data System (ADS)

    Yang, Zhaohua; Huo, Jiayan; Yang, Xu

    2015-10-01

    Rayleigh backscattering noise, which is one of the reasons that limit the sensitivity, has been deemed as noise in traditional resonant optic gyroscopes. However Rayleigh backscattering noise is one of the incentives of mode splitting phenomenon in high-Q resonators. Regarding the change of the resonance frequency of the resonator caused by the scattering signal as a measurement, we can use mode splitting to measure temperature, size of nanoparticle, etc. Light is confined by total internal reflection in whispering gallery mode (WGM) optical resonators, which is characterized by high-Q factors and small mode volumes. With regards to this, we propose a sensing mechanism based on mode splitting in high-Q WGM optical resonators. It is possible for us to measure the angular velocity of carrier according to the changes in the resonant frequencies of the two splitting modes. We propose the Miniature resonant optic gyroscope based on mode splitting (MROG-MS) with WGM resonators in the paper. Considering the Sagnac effect, mode splitting in high quality optical micro-resonators, and the rotation-induced impact on backscattering process, we modify the equations of motion that describe mode splitting, derive the explicit expression of angular rate versus the splitting amount, and verify the sensing mechanism by the simulation based on COMSOL. Furthermore, after monitoring the transmission spectra at different number of scattering particles, the simulation shows that mode splitting phenomenon resulted by single particle is more suitable for angular velocity measurement.

  4. Protein-based flexible whispering gallery mode resonators

    NASA Astrophysics Data System (ADS)

    Yilmaz, Huzeyfe; Pena-Francesch, Abdon; Xu, Linhua; Shreiner, Robert; Jung, Huihun; Huang, Steven H.; Özdemir, Sahin K.; Demirel, Melik C.; Yang, Lan

    2016-02-01

    The idea of creating photonics tools for sensing, imaging and material characterization has long been pursued and many achievements have been made. Approaching the level of solutions provided by nature however is hindered by routine choice of materials. To this end recent years have witnessed a great effort to engineer mechanically flexible photonic devices using polymer substrates. On the other hand, biodegradability and biocompatibility still remains to be incorporated. Hence biomimetics holds the key to overcome the limitations of traditional materials in photonics design. Natural proteins such as sucker ring teeth (SRT) and silk for instance have remarkable mechanical and optical properties that exceed the endeavors of most synthetic and natural polymers. Here we demonstrate for the first time, toroidal whispering gallery mode resonators (WGMR) fabricated entirely from protein structures such as SRT of Loligo vulgaris (European squid) and silk from Bombyx mori. We provide here complete optical and material characterization of proteinaceous WGMRs, revealing high quality factors in microscale and enhancement of Raman signatures by a microcavity. We also present a most simple application of a WGMR as a natural protein add-drop filter, made of SRT protein. Our work shows that with protein-based materials, optical, mechanical and thermal properties can be devised at the molecular level and it lays the groundwork for future eco-friendly, flexible photonics device design.

  5. Temperature Sensing in Seawater Based on Microfiber Knot Resonator

    PubMed Central

    Yang, Hongjuan; Wang, Shanshan; Wang, Xin; Liao, Yipeng; Wang, Jing

    2014-01-01

    Ocean internal-wave phenomena occur with the variation in seawater vertical temperature, and most internal-wave detections are dependent on the measurement of seawater vertical temperature. A seawater temperature sensor based on a microfiber knot resonator (MKR) is designed theoretically and demonstrated experimentally in this paper. Especially, the dependences of sensing sensitivity on fiber diameter and probing wavelength are studied. Calculated results show that sensing sensitivity increases with the increasing microfiber diameter with the range of 2.30–3.91 μm and increases with the increasing probing wavelength, which reach good agreement with results obtained by experiments. By choosing the appropriate parameters, the maximum sensitivity measured can reach to be 22.81 pm/°C. The seawater temperature sensor demonstrated here shows advantages of small size, high sensitivity, easy fabrication, and easy integration with fiber systems, which may offer a new optical method to detect temperature of seawater or ocean internal-wave phenomenon and offer valuable reference for assembling micro sensors used for other parameters related to seawater, such as salinity, refractive index, concentration of NO3− and so on. PMID:25299951

  6. Discrete decoding based ultrafast multidimensional nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Wei, Zhiliang; Lin, Liangjie; Ye, Qimiao; Li, Jing; Cai, Shuhui; Chen, Zhong

    2015-07-01

    The three-dimensional (3D) nuclear magnetic resonance (NMR) spectroscopy constitutes an important and powerful tool in analyzing chemical and biological systems. However, the abundant 3D information arrives at the expense of long acquisition times lasting hours or even days. Therefore, there has been a continuous interest in developing techniques to accelerate recordings of 3D NMR spectra, among which the ultrafast spatiotemporal encoding technique supplies impressive acquisition speed by compressing a multidimensional spectrum in a single scan. However, it tends to suffer from tradeoffs among spectral widths in different dimensions, which deteriorates in cases of NMR spectroscopy with more dimensions. In this study, the discrete decoding is proposed to liberate the ultrafast technique from tradeoffs among spectral widths in different dimensions by focusing decoding on signal-bearing sites. For verifying its feasibility and effectiveness, we utilized the method to generate two different types of 3D spectra. The proposed method is also applicable to cases with more than three dimensions, which, based on the experimental results, may widen applications of the ultrafast technique.

  7. Discrete decoding based ultrafast multidimensional nuclear magnetic resonance spectroscopy

    SciTech Connect

    Wei, Zhiliang; Lin, Liangjie; Ye, Qimiao; Li, Jing; Cai, Shuhui; Chen, Zhong

    2015-07-14

    The three-dimensional (3D) nuclear magnetic resonance (NMR) spectroscopy constitutes an important and powerful tool in analyzing chemical and biological systems. However, the abundant 3D information arrives at the expense of long acquisition times lasting hours or even days. Therefore, there has been a continuous interest in developing techniques to accelerate recordings of 3D NMR spectra, among which the ultrafast spatiotemporal encoding technique supplies impressive acquisition speed by compressing a multidimensional spectrum in a single scan. However, it tends to suffer from tradeoffs among spectral widths in different dimensions, which deteriorates in cases of NMR spectroscopy with more dimensions. In this study, the discrete decoding is proposed to liberate the ultrafast technique from tradeoffs among spectral widths in different dimensions by focusing decoding on signal-bearing sites. For verifying its feasibility and effectiveness, we utilized the method to generate two different types of 3D spectra. The proposed method is also applicable to cases with more than three dimensions, which, based on the experimental results, may widen applications of the ultrafast technique.

  8. Impedimetric Label-Free Immunosensor on Disposable Modified Screen-Printed Electrodes for Ochratoxin A.

    PubMed

    Malvano, Francesca; Albanese, Donatella; Crescitelli, Alessio; Pilloton, Roberto; Esposito, Emanuela

    2016-01-01

    An impedimetric label-free immunosensor on disposable screen-printed carbon electrodes (SPCE) for quantitative determination of Ochratoxin A (OTA) has been developed. After modification of the SPCE surface with gold nanoparticles (AuNPs), the anti-OTA was immobilized on the working electrode through a cysteamine layer. After each coating step, the modified surfaces were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The capacitance was chosen as the best parameter that describes the reproducible change in electrical properties of the electrode surface at different OTA concentrations and it was used to investigate the analytical parameters of the developed immunosensor. Under optimized conditions, the immunosensor showed a linear relationship between 0.3 and 20 ng/mL with a low detection limit of 0.25 ng/mL, making it suitable to control OTA content in many common food products. Lastly, the immunosensor was used to measure OTA in red wine samples and the results were compared with those registered with a competitive ELISA kit. The immunosensor was sensitive to OTA lower than 2 μg/kg, which represents the lower acceptable limit of OTA established by European legislation for common food products. PMID:27376339

  9. Wireless power transfer based on magnetic quadrupole coupling in dielectric resonators

    NASA Astrophysics Data System (ADS)

    Song, Mingzhao; Iorsh, Ivan; Kapitanova, Polina; Nenasheva, Elizaveta; Belov, Pavel

    2016-01-01

    We numerically investigate a magnetic resonant wireless power transfer system based on high refractive index dielectric resonators. We propose to operate at magnetic quadrupole mode of the resonators to enlarge the efficiency due to minimization of ohmic and radiation losses. Numerical estimation predicts the 80% efficiency of the wireless power transfer (WPT) system operating at quadrupole mode at 300 MHz. Moreover, the system operating at magnetic quadrupole mode is capable of transferring power with 70% efficiency when the receiver rotates 90°. We verify the simulated results by experimental investigation of the WPT system based on microwave ceramic resonators (ɛ = 80 and tanδ = 10-4).

  10. The localized surface plasmon resonances based on a Bragg reflector

    NASA Astrophysics Data System (ADS)

    Wang, Jie; Liu, Yumin; Yu, Zhongyuan; Ye, Chunwei; Lv, Hongbo; Shu, Changgan

    2014-09-01

    In this paper, we present the theoretical analysis on how the wavelength of the localized surface plasmon resonances of gold nanoparticle can lead shift for the resonance wavelength. In our results, we calculate the scattering cross-section, the absorption cross-section and the field enhancement due to the nanoparticle. Numerical simulation were done using the finite element method (FEM). The work that we do here is different from the previous work because we use the Bragg reflector as a substrate. The Bragg reflector has a property of high reflectivity in some certain frequency bandwidth because of its periodic structure. The coherence interference of the Bragg reflector contributes to the plasmon resonances and results in some special character for a wide variety application, from sensing to photovoltaic. The periodic number of the Bragg reflector substrate and shapes of the nanoparticles are also discussed that result in a shift of the resonance wavelength.

  11. Near infrared plasmonic sensor based on Fano resonance

    NASA Astrophysics Data System (ADS)

    Sherif, S. M.; Shahada, L.; Zografopoulos, D. C.; Beccherelli, R.; Swillam, M.

    2016-02-01

    We introduce a compact plasmonic resonator that is capable of generating a Fano resonance in the transmission spectrum. The Fano resonance is observed with its unique lineshape. The proposed design is simple, compact, easy to fabricate and can be easily developed for different applications. The device structure is made of a gold layer, a metalinsulator- metal waveguide, and a rectangular cavity. As an application to the proposed plasmonic resonator, we introduce a gas sensor which is operational at the near infrared spectral range. The sensor possesses a high sensitivity of 1500nm/RIU at the telecom wavelength 1.55μm. FDTD simulation tools were conducted for the optimization of the device structure and obtaining the results.

  12. Chemiluminescence resonance energy transfer-based detection for microchip electrophoresis.

    PubMed

    Zhao, Shulin; Huang, Yong; Shi, Ming; Liu, Rongjun; Liu, Yi-Ming

    2010-03-01

    Since the channels in micro- and nanofluidic devices are extremely small, a sensitive detection is required following microchip electrophoresis (MCE). This work describes a highly sensitive and yet universal detection scheme based on chemiluminescence resonance energy transfer (CRET) for MCE. It was found that an efficient CRET occurred between a luminol donor and a CdTe quantum dot (QD) acceptor in the luminol-NaBrO-QD system and that it was sensitively suppressed by the presence of certain organic compounds of biological interest including biogenic amines and thiols, amino acids, organic acids, and steroids. These findings allowed developing sensitive MCE-CL assays for the tested compounds. The proposed MCE-CL methods showed desired analytical figures of merit such as a wide concentration range of linear response. Detection limits obtained were approximately 10(-9) M for biogenic amines including dopamine and epinephrine and approximately 10(-8) M for biogenic thiols (e.g., glutathione and acetylcysteine), organic acids (i.e., ascorbic acid and uric acid), estrogens, and native amino acids. These were 10-1000 times more sensitive than those of previously reported MCE-based methods with chemiluminescence, electrochemical, or laser-induced fluorescence detection for quantifying corresponding compounds. To evaluate the applicability of the present MCE-CL method for analyzing real biological samples, it was used to determine amino acids in individual human red blood cells. Nine amino acids, including Lys, Ser, Ala, Glu, Trp, etc., were detected. The contents ranged from 3 to 31 amol/cell. The assay proved to be simple, quick, reproducible, and very sensitive. PMID:20121202

  13. Theory of double resonance magnetometers based on atomic alignment

    SciTech Connect

    Weis, Antoine; Bison, Georg; Pazgalev, Anatoly S.

    2006-09-15

    We present a theoretical study of the spectra produced by optical-radio-frequency double resonance devices, in which resonant linearly polarized light is used in the optical pumping and detection processes. We extend previous work by presenting algebraic results which are valid for atomic states with arbitrary angular momenta, arbitrary rf intensities, and arbitrary geometries. The only restriction made is the assumption of low light intensity. The results are discussed in view of their use in optical magnetometers.

  14. Plasmon resonance hybridization in self-assembled copper nanoparticle clusters: efficient and precise localization of surface plasmon resonance (LSPR) sensing based on Fano resonances.

    PubMed

    Ahmadivand, Arash; Pala, Nezih

    2015-01-01

    In this work, we have investigated the hybridization of plasmon resonance modes in completely copper (Cu)-based subwavelength nanoparticle clusters from simple symmetric dimers to complex asymmetric self-assembled structures. The quality of apparent bonding and antibonding plasmon resonance modes for all of the clusters has been studied, and we examined the spectral response of each one of the proposed configurations numerically using the finite-difference time domain (FDTD) method. The effect of the geometric sizes of nanoparticles used and substrate refractive index on the cross-sectional profiles of each of the studied structures has been calculated and drawn. We proved that Fano-like resonance can be formed in Cu-based heptamer clusters as in analogous noble metallic particles (e.g., Au and Ag) by determining the coupling strength and interference between sub-radiant and super-radiant resonance modes. Employing certain Cu nanodiscs in designing an octamer structure, we measured the quality of the Fano dip formation along the scattering diagram. Accurate tuning of the geometric sizes for the Cu-based octamer yields an opportunity to observe isotropic, deep, and narrow Fano minima along the scattering profile that are in comparable condition with the response of other plasmonic metallic substances. Immersing investigated final Cu-based octamer in various liquids with different refractive indices, we determined the sensing accuracy of the cluster based on the performance of the Fano dip. Plotting a linear diagram of plasmon energy differences over the refractive index variations as a figure of merit (FoM), which we have quantified as 13.25. With this method, the precision of the completely Cu-based octamer is verified numerically using the FDTD tool. This study paves the way toward the use of Cu as an efficient, low-cost, and complementary metal-oxide semiconductor (CMOS)-compatible plasmonic material with optical properties that are similar to analogous plasmonic

  15. Silicon dual-ring resonator-based push-pull modulators

    NASA Astrophysics Data System (ADS)

    Sun, Xiaomeng; Zhou, Linjie; Jäger, Matthias; Petousi, Despoina; Zimmermann, Lars; Petermann, Klaus

    2016-03-01

    Two types of silicon dual-ring resonator-based high-speed optical modulators are proposed. With two microring resonators cascaded either in series or in parallel, the transmission spectrum evolves from a deep notch to a sharp peak with the resonators operating in a push-pull manner. The frequency chirp of the modulated signals can be highly suppressed by choosing a proper working wavelength.

  16. Visual and efficient immunosensor technique for advancing biomedical applications of quantum dots on Salmonella detection and isolation

    NASA Astrophysics Data System (ADS)

    Tang, Feng; Pang, Dai-Wen; Chen, Zhi; Shao, Jian-Bo; Xiong, Ling-Hong; Xiang, Yan-Ping; Xiong, Yan; Wu, Kai; Ai, Hong-Wu; Zhang, Hui; Zheng, Xiao-Li; Lv, Jing-Rui; Liu, Wei-Yong; Hu, Hong-Bing; Mei, Hong; Zhang, Zhen; Sun, Hong; Xiang, Yun; Sun, Zi-Yong

    2016-02-01

    It is a great challenge in nanotechnology for fluorescent nanobioprobes to be applied to visually detect and directly isolate pathogens in situ. A novel and visual immunosensor technique for efficient detection and isolation of Salmonella was established here by applying fluorescent nanobioprobes on a specially-designed cellulose-based swab (a solid-phase enrichment system). The selective and chromogenic medium used on this swab can achieve the ultrasensitive amplification of target bacteria and form chromogenic colonies in situ based on a simple biochemical reaction. More importantly, because this swab can serve as an attachment site for the targeted pathogens to immobilize and immunologically capture nanobioprobes, our mAb-conjugated QD bioprobes were successfully applied on the solid-phase enrichment system to capture the fluorescence of targeted colonies under a designed excitation light instrument based on blue light-emitting diodes combined with stereomicroscopy or laser scanning confocal microscopy. Compared with the traditional methods using 4-7 days to isolate Salmonella from the bacterial mixture, this method took only 2 days to do this, and the process of initial screening and preliminary diagnosis can be completed in only one and a half days. Furthermore, the limit of detection can reach as low as 101 cells per mL Salmonella on the background of 105 cells per mL non-Salmonella (Escherichia coli, Proteus mirabilis or Citrobacter freundii, respectively) in experimental samples, and even in human anal ones. The visual and efficient immunosensor technique may be proved to be a favorable alternative for screening and isolating Salmonella in a large number of samples related to public health surveillance.It is a great challenge in nanotechnology for fluorescent nanobioprobes to be applied to visually detect and directly isolate pathogens in situ. A novel and visual immunosensor technique for efficient detection and isolation of Salmonella was established here

  17. Direct immobilization of antibodies on a new polymer film for fabricating an electrochemical impedance immunosensor.

    PubMed

    Zhang, Xiangyang; Shen, Guangyu; Shen, Youming; Yin, Dan; Zhang, Chunxiang

    2015-09-15

    A new polymer bearing aldehyde groups was designed and synthesized by grafting 4-pyridinecarboxaldehyde onto poly(epichlorohydrin). Antibodies can be directly immobilized on the surface of the polymer film through the covalent bonding of aldehyde groups of the film with amino groups of antibodies. In this study, human immunoglobulin G (IgG) was used as a model analyte for the fabrication of an electrochemical impedance immunosensor. Using the proposed immunosensor, IgG in the range from 0.1 to 80 ng ml(-1) was detected with a detection limit of 0.07 ng ml(-1) (signal/noise [S/N]=3). In addition, the electrochemical impedance immunosensor displays good stability and reproducibility. PMID:26072006

  18. Visual and efficient immunosensor technique for advancing biomedical applications of quantum dots on Salmonella detection and isolation.

    PubMed

    Tang, Feng; Pang, Dai-Wen; Chen, Zhi; Shao, Jian-Bo; Xiong, Ling-Hong; Xiang, Yan-Ping; Xiong, Yan; Wu, Kai; Ai, Hong-Wu; Zhang, Hui; Zheng, Xiao-Li; Lv, Jing-Rui; Liu, Wei-Yong; Hu, Hong-Bing; Mei, Hong; Zhang, Zhen; Sun, Hong; Xiang, Yun; Sun, Zi-Yong

    2016-02-28

    It is a great challenge in nanotechnology for fluorescent nanobioprobes to be applied to visually detect and directly isolate pathogens in situ. A novel and visual immunosensor technique for efficient detection and isolation of Salmonella was established here by applying fluorescent nanobioprobes on a specially-designed cellulose-based swab (a solid-phase enrichment system). The selective and chromogenic medium used on this swab can achieve the ultrasensitive amplification of target bacteria and form chromogenic colonies in situ based on a simple biochemical reaction. More importantly, because this swab can serve as an attachment site for the targeted pathogens to immobilize and immunologically capture nanobioprobes, our mAb-conjugated QD bioprobes were successfully applied on the solid-phase enrichment system to capture the fluorescence of targeted colonies under a designed excitation light instrument based on blue light-emitting diodes combined with stereomicroscopy or laser scanning confocal microscopy. Compared with the traditional methods using 4-7 days to isolate Salmonella from the bacterial mixture, this method took only 2 days to do this, and the process of initial screening and preliminary diagnosis can be completed in only one and a half days. Furthermore, the limit of detection can reach as low as 10(1) cells per mL Salmonella on the background of 10(5) cells per mL non-Salmonella (Escherichia coli, Proteus mirabilis or Citrobacter freundii, respectively) in experimental samples, and even in human anal ones. The visual and efficient immunosensor technique may be proved to be a favorable alternative for screening and isolating Salmonella in a large number of samples related to public health surveillance. PMID:26853517

  19. Graphene modified screen printed immunosensor for highly sensitive detection of parathion.

    PubMed

    Mehta, Jyotsana; Vinayak, Priya; Tuteja, Satish K; Chhabra, Varun A; Bhardwaj, Neha; Paul, A K; Kim, Ki-Hyun; Deep, Akash

    2016-09-15

    Due to indiscriminate use of pesticides, there is a growing need to develop sensors that can sensitively detect the trace amount of pesticides in food and water samples. Parathion, identified as an acetylcholinesterase inhibitor, had been one of the most widely used pesticides throughout the world. Symptoms of its poisoning are found to be diverse enough to include nausea, vomiting, diarrhea, muscle cramping/twitching, and shortness of breath. In this work, a graphene based impedimetric immunosensor has been fabricated and employed for highly sensitive and specific detection of parathion. The fabrication proceeded through the modification of the screen-printed carbon electrodes (SPE) with graphene sheets, followed by their functionalization with 2-aminobenzyl amine (2-ABA) via an electrochemical reaction. These amine functionalized graphene electrodes were then bio-interfaced with the anti-parathion antibodies. In the impedimetric mode, this biosensor detected parathion in a broad linear range, i.e. 0.1-1000ng/L with a very low limit of detection (52pg/L). It also showed high selectivity towards parathion in the presence of malathion, paraoxon, and fenitrothion. The viability of this biosensor was demonstrated by detecting parathion in real samples (e.g., tomato and carrot) and through cross-calibration against HPLC. PMID:27135939

  20. 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

  1. Explosives detection in soil using a field-portable continuous flow immunosensor.

    PubMed

    Gauger, P R; Holt, D B; Patterson, C H; Charles, P T; Shriver-Lake, L; Kusterbeck, A W

    2001-05-01

    A field method for quantitative analysis of explosives in contaminated soil samples is described. The method is based on a displacement immunoassay performed in a commercial instrument, the FAST 2000, engineered by Research International Inc. The method can be used on-site to measure 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) within 5min. For this study, replicate analyses were performed on soil extracts prepared from each field sample as well as appropriate controls, blanks, and laboratory standards. Statistical analyses were done to assess accuracy, bias, and predictability of the method. The results demonstrated that the immunosensor could be used effectively to screen environmental samples for the presence or absence of explosives. In most samples, the method also provided quantitative values that were in good agreement with standard laboratory analyses using HPLC. A limited number of sample matrices interfered with the immunoassay and produced results that varied significantly from the laboratory data. In each case, the compounds causing the problem have been identified and efforts are being made to minimize these matrix interferences in future field evaluations. PMID:11267745

  2. Evaluation of the Spectral Response of Functionalized Silk Inverse Opals as Colorimetric Immunosensors.

    PubMed

    Burke, Kelly A; Brenckle, Mark A; Kaplan, David L; Omenetto, Fiorenzo G

    2016-06-29

    Regenerated silk fibroin is a high molecular weight protein obtained by purifying the cocoons of the domesticated silkworm, Bombyx mori. This report exploits the aqueous processing and tunable β sheet secondary structure of regenerated silk to produce nanostructures (i.e., inverse opals) that can be used as colorimetric immunosensors. Such sensors would enable direct detection of antigens by changes in reflectance spectra induced by binding events within the nanostructure. Silk inverse opals were prepared by solution casting and annealing in a humidified atmosphere to render the silk insoluble. Next, antigen sensing capabilities were imparted to silk through a three step synthesis: coupling of avidin to silk surfaces, coupling of biotin to antibodies, and lastly antibody attachment to silk through avidin-biotin interactions. Varying the antibody enables detection of different antigens, as demonstrated using different protein antigens: antibodies, red fluorescent protein, and the beta subunit of cholera toxin. Antigen binding to sensors induces a red shift in the opal reflectance spectra, while sensors not exposed to antigen showed either no shift or a slight blue shift. This work constitutes a first step for the design of biopolymer-based optical systems that could directly detect antigens using commercially available reagents and environmentally friendly chemistries. PMID:27322909

  3. Boosting figures of merit of cavity plasmon resonance based refractive index sensing in dielectric-metal core-shell resonators.

    PubMed

    Li, Zhiqin; Sun, Ren; Zhang, Chi; Wan, Mingjie; Gu, Ping; Shen, Qi; Chen, Zhuo; Wang, Zhenling

    2016-08-22

    We theoretically investigate the sensing performance of the dielectric-metal core-shell resonators (DMCSRs) that support multipolar sharp magnetic and electric-based cavity plasmon resonances. We show that at the cavity resonances the ability of the DMCSRs to strongly confine the optical fields inside the cavity is robust against the existence of nano-openings in the metal shell layer. As a result, both the perfect DMCSRs having a complete metal shell layer and the non-perfect DMCSRs with nano-openings in the metal shell layers exhibit high refractive index sensitivities of 700 ~1200 nm/RIU. Furthermore, we demonstrate that such high refractive index sensitivities could be well maintained in an array of interconnected non-perfect DMCSRs. The narrow linewidths of the cavity plasmon resonances coupled with their high index sensitivities make the array of non-perfect DMCSRs possess high figure of merit (FOM) values up to ~88, approaching the theoretically estimated upper limit (FOM ≈108) for gold standard prism coupled surface-plasmon sensors. PMID:27557265

  4. Detection of estradiol at an electrochemical immunosensor with a Cu UPD|DTBP-Protein G scaffold.

    PubMed

    Liu, Xiaoqiang; Wang, Xinhai; Zhang, Jiamei; Feng, Heqing; Liu, Xiuhua; Wong, Danny K Y

    2012-05-15

    A copper monolayer was formed on a gold electrode surface via underpotential deposition (UPD) method to construct a Cu UPD|DTBP-Protein G immunosensor for the sensitive detection of 17β-estradiol. Copper UPD monolayer can minimize the non-specific adsorption of biological molecules on the immunosensor surface and enhance the binding efficiency between immunosensor surface and thiolated Protein G. The crosslinker DTBP (Dimethyl 3,3'-dithiobispropionimidate · 2HCl) has strong ability to immobilize Protein G molecules on the electrode surface and the immobilized Protein G provides an orientation-controlled binding of antibodies. A monolayer of propanethiol was firstly self-assembled on the gold electrode surface, and a copper monolayer was deposited via UPD on the propanethiol modified electrode. Propanethiol monolayer helps to stabilize the copper monolayer by pushing the formation and stripping potentials of the copper UPD monolayer outside the potential range in which copper monolayer can be damaged easily by oxygen in air. A droplet DTBP-Protein G was then applied on the modified electrode surface followed by the immobilization of estradiol antibody. Finally, a competitive immunoassay was conducted between estradiol-BSA (bovine serum albumin) conjugate and free estradiol for the limited binding sites of estradiol antibody. Square wave voltammetry (SWV) was employed to monitor the electrochemical reduction current of ferrocenemethanol and the SWV current decreased with the increase of estradiol-BSA conjugate concentration at the immunosensor surface. Calibration of immunosensors in waste water samples spiked with 17β-estradiol yielded a linear response up to ≈ 2200 pg mL(-1), a sensitivity of 3.20 μA/pg mL(-1) and a detection limit of 12 pg mL(-1). The favorable characteristics of the immunosensors such as high selectivity, sensitivity and low detection limit can be attributed to the Cu UPD|DTBP-Protein G scaffold. PMID:22405841

  5. Nanoscale welding aerosol sensing based on whispering gallery modes in a cylindrical silica resonator

    PubMed Central

    Lee, Aram; Mills, Thomas; Xu, Yong

    2015-01-01

    We report an experimental technique where one uses a standard silica fiber as a cylindrical whispering gallery mode (WGM) resonator to sense airborne nanoscale aerosols produced by electric arc welding. We find that the accumulation of aerosols on the resonator surface induces a measurable red-shift in resonance frequency, and establish an empirical relation that links the magnitude of resonance shift with the amount of aerosol deposition. The WGM quality factors, by contrast, do not decrease significantly, even for samples with a large percentage of surface area covered by aerosols. Our experimental results are discussed and compared with existing literature on WGM-based nanoparticle sensing. PMID:25837078

  6. Effect of angular velocity on sensors based on morphology dependent resonances.

    PubMed

    Ali, Amir R; Ioppolo, Tindaro

    2014-01-01

    We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR) of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS) microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning sensor based on MDR may experience sufficient shift in the optical resonances, therefore interfering with its desirable operational sensor design. Also the results show that angular velocity sensors could be designed using this principle. PMID:24759108

  7. Effect of Angular Velocity on Sensors Based on Morphology Dependent Resonances

    PubMed Central

    Ali, Amir R.; Ioppolo, Tindaro

    2014-01-01

    We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR) of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS) microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning sensor based on MDR may experience sufficient shift in the optical resonances, therefore interfering with its desirable operational sensor design. Also the results show that angular velocity sensors could be designed using this principle. PMID:24759108

  8. Mass spectrometry based on a coupled Cooper-pair box and nanomechanical resonator system

    NASA Astrophysics Data System (ADS)

    Jiang, Cheng; Chen, Bin; Li, Jin-Jin; Zhu, Ka-Di

    2011-10-01

    Nanomechanical resonators (NRs) with very high frequency have a great potential for mass sensing with unprecedented sensitivity. In this study, we propose a scheme for mass sensing based on the NR capacitively coupled to a Cooper-pair box (CPB) driven by two microwave currents. The accreted mass landing on the resonator can be measured conveniently by tracking the resonance frequency shifts because of mass changes in the signal absorption spectrum. We demonstrate that frequency shifts induced by adsorption of ten 1587 bp DNA molecules can be well resolved in the absorption spectrum. Integration with the CPB enables capacitive readout of the mechanical resonance directly on the chip.

  9. Research of resonators based on elastic sheet/membrane elements for hydraulic system

    NASA Astrophysics Data System (ADS)

    Shanghong, He; Yanjun, Zi; Wen, Wang

    2015-10-01

    Based on the theory of dynamic vibration absorber, a class of structure resonators equipped with additional vibrators is put forward to suppress fluid pulsation which causes system unstable or reduces work performance. Working principle of resonators is explained from mechanics and three kinds of elements are used to work as additional vibrators, namely round metal sheet, rectangular metal sheet, round rubber membrane. Multiple vibrators are designed into one resonator to damp the pressure pulsation in system over a wide range of frequency. Mathematical models of resonators based on sheet elements are gained through analyzing the vibration characteristics of sheets in fluid. Lumped parameter method is used to study the attenuation characteristics which are based on matrix model of the entire hydraulic system. Simulations are conducted and results guide the determination of configuration parameters of experimental prototypes. Experimental tests are carried out on prototypes and results show good attenuation performance, especially near the resonant frequencies of sheet/membrane elements in fluid.

  10. A Lateral Differential Resonant Pressure Microsensor Based on SOI-Glass Wafer-Level Vacuum Packaging

    PubMed Central

    Xie, Bo; Xing, Yonghao; Wang, Yanshuang; Chen, Jian; Chen, Deyong; Wang, Junbo

    2015-01-01

    This paper presents the fabrication and characterization of a resonant pressure microsensor based on SOI-glass wafer-level vacuum packaging. The SOI-based pressure microsensor consists of a pressure-sensitive diaphragm at the handle layer and two lateral resonators (electrostatic excitation and capacitive detection) on the device layer as a differential setup. The resonators were vacuum packaged with a glass cap using anodic bonding and the wire interconnection was realized using a mask-free electrochemical etching approach by selectively patterning an Au film on highly topographic surfaces. The fabricated resonant pressure microsensor with dual resonators was characterized in a systematic manner, producing a quality factor higher than 10,000 (~6 months), a sensitivity of about 166 Hz/kPa and a reduced nonlinear error of 0.033% F.S. Based on the differential output, the sensitivity was increased to two times and the temperature-caused frequency drift was decreased to 25%. PMID:26402679

  11. A Lateral Differential Resonant Pressure Microsensor Based on SOI-Glass Wafer-Level Vacuum Packaging.

    PubMed

    Xie, Bo; Xing, Yonghao; Wang, Yanshuang; Chen, Jian; Chen, Deyong; Wang, Junbo

    2015-01-01

    This paper presents the fabrication and characterization of a resonant pressure microsensor based on SOI-glass wafer-level vacuum packaging. The SOI-based pressure microsensor consists of a pressure-sensitive diaphragm at the handle layer and two lateral resonators (electrostatic excitation and capacitive detection) on the device layer as a differential setup. The resonators were vacuum packaged with a glass cap using anodic bonding and the wire interconnection was realized using a mask-free electrochemical etching approach by selectively patterning an Au film on highly topographic surfaces. The fabricated resonant pressure microsensor with dual resonators was characterized in a systematic manner, producing a quality factor higher than 10,000 (~6 months), a sensitivity of about 166 Hz/kPa and a reduced nonlinear error of 0.033% F.S. Based on the differential output, the sensitivity was increased to two times and the temperature-caused frequency drift was decreased to 25%. PMID:26402679

  12. A graphene based tunable terahertz sensor with double Fano resonances

    NASA Astrophysics Data System (ADS)

    Zhang, Yuping; Li, Tongtong; Zeng, Beibei; Zhang, Huiyun; Lv, Huanhuan; Huang, Xiaoyan; Zhang, Weili; Azad, Abul K.

    2015-07-01

    We propose an ultrasensitive terahertz (THz) sensor consisting of a subwavelength graphene disk and an annular gold ring within a unit cell. The interference between the resonances arising from the graphene disk and the gold ring gives rise to Fano type resonances and enables ultrasensitive sensing. Our full wave electromagnetic simulations show frequency sensitivity as high as 1.9082 THz per refractive index unit (RIU) and a figure of merit (FOM) of 6.5662. Furthermore, the sensing range can be actively tuned by adjusting the Fermi level of graphene.

  13. A graphene based tunable terahertz sensor with double Fano resonances.

    PubMed

    Zhang, Yuping; Li, Tongtong; Zeng, Beibei; Zhang, Huiyun; Lv, Huanhuan; Huang, Xiaoyan; Zhang, Weili; Azad, Abul K

    2015-08-01

    We propose an ultrasensitive terahertz (THz) sensor consisting of a subwavelength graphene disk and an annular gold ring within a unit cell. The interference between the resonances arising from the graphene disk and the gold ring gives rise to Fano type resonances and enables ultrasensitive sensing. Our full wave electromagnetic simulations show frequency sensitivity as high as 1.9082 THz per refractive index unit (RIU) and a figure of merit (FOM) of 6.5662. Furthermore, the sensing range can be actively tuned by adjusting the Fermi level of graphene. PMID:26148569

  14. Resonant metamaterial detectors based on THz quantum-cascade structures

    PubMed Central

    Benz, A.; Krall, M.; Schwarz, S.; Dietze, D.; Detz, H.; Andrews, A. M.; Schrenk, W.; Strasser, G.; Unterrainer, K.

    2014-01-01

    We present the design, fabrication and characterisation of an intersubband detector employing a resonant metamaterial coupling structure. The semiconductor heterostructure relies on a conventional THz quantum-cascade laser design and is operated at zero bias for the detector operation. The same active region can be used to generate or detect light depending on the bias conditions and the vertical confinement. The metamaterial is processed directly into the top metal contact and is used to couple normal incidence radiation resonantly to the intersubband transitions. The device is capable of detecting light below and above the reststrahlenband of gallium-arsenide corresponding to the mid-infrared and THz spectral region. PMID:24608677

  15. Tapping mode quartz crystal resonator based scanning force microscopy

    NASA Astrophysics Data System (ADS)

    Seo, Yongho; Jhe, Wonho

    2005-01-01

    We have built a high-speed, tapping mode scanning force microscope using a high frequency quartz crystal resonator. In our design, a cantilever tip was attached to the end of an optical fiber which was glued to a thickness shear mode, AT-cut quartz crystal resonator so as to vibrate in the longitudinal direction. This design allows the microscope to be operated in tapping mode with the flexibility of shear mode operation, which leads to an expected improvement of image quality. Furthermore, combining this geometry with an optical microscope leads to the possibility of commercial applications.

  16. Intrinsically tunable bulk acoustic wave resonators based on sol-gel grown PMN-PT films

    NASA Astrophysics Data System (ADS)

    Vorobiev, A.; Spreitzer, M.; Veber, A.; Suvorov, D.; Gevorgian, S.

    2014-08-01

    Intrinsically tunable bulk acoustic wave resonators, based on sol-gel 0.70Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PMN-PT) thin films, with high effective electromechanical coupling coefficient of 13% and tunability of the series resonance frequency up to 4.0% are fabricated and characterized. The enhanced electroacoustic properties of the PMN-PT resonators are attributed to the mechanism of polarization rotation occurring in the region of the morphotropic phase boundary. Electroacoustic performance of the PMN-PT resonators is analyzed using the theory of dc field-induced piezoelectric effect in ferroelectrics. Extrinsic acoustic loss in the PMN-PT resonators is analyzed using the model of the wave scattering at reflections from rough interfaces. Mechanical Q-factor of the resonators is up to 70 at 4.1 GHz and limited mainly by losses in the PMN-PT film.

  17. Fiber optic immunosensor for cross-linked fibrin concentration

    NASA Astrophysics Data System (ADS)

    Moskowitz, Samuel E.

    2000-08-01

    Working with calcium ions in the blood, platelets produce thromboplastin which transforms prothrombin into thrombin. Removing peptides, thrombin changes fibrinogen into fibrin. Cross-linked insoluble fibrin polymers are solubilized by enzyme plasmin found in blood plasma. Resulting D-dimers are elevated in patients with intravascular coagulation, deep venous thrombosis, pulmonary embolism, myocardial infarction, multiple trauma, cancer, impaired renal and liver functions, and sepsis. Consisting principally of a NIR 780 nm GaAlAs laser diode and a 800 nm avalanche photodiode (APD), the fiber-optic immunosensor can determined D-dimer concentration to levels <0.1 ng/ml. A capture monoclonal antibody to the antigen soluble cross-linked fibrin is employed. Immobilized at the tip of an optical fiber by avidin-biotin, the captured antigen is detected by a second antibody which is labeled with NN 382 fluorescent dye. An evanescent wave traveling on an excitation optical fiber excites the antibody-antigen fluorophore complex. Concentration of cross-linked fibrin is directly proportional to the APD measured intensity of fluorescence. NIR fluorescence has advantages of low background interference, short fluorescence lifetime, and large difference between excitation and emission peaks. Competitive ELISA test for D-dimer concentration requires trained personnel performing a time consuming operation.

  18. Theoretical and experimental study of fiber-optic fluorescence immunosensors

    NASA Astrophysics Data System (ADS)

    Cao, He

    This dissertation investigates the optical detection of antigens (in this case, food pathogens such as Salmonella) with fiber-optic immunosensors. The major techniques used for this optical detection include: (1)Linking the antigens to some physical tracers that can be optically detected; (2)Collecting and transmitting the optical signal to an optical detector. From an optical point of view, the problem is a nonimaging-optics problem to collect a fluorescent signal from an extended Lambertian source and deliver it to an optical detection system with maximum energy transfer and distinct wavelength separation. A raytrace model of the optical detection system was used for numerical simulations to analyze and optimize the optical design. The result leads to an improvement of the optical detection. Related physical problems such as magnetic focusing effect, fluorescence detection, and wavelength separation have also been studied in detail. With the adoption of a single-step immunomagnetic assay, experimental studies have been conducted for the detection of Salmonella, with a dual- fiber optical probe and tapered tubular waveguide probes. The test results have shown that the detection system gives detection limit of approximately 106 CFU/ml with dual-fiber optical probes, and 105 CFU/ml with improved tubular waveguide probes. The system developed for this research project is designed as a cost-effective portable instrument that may be used for field-testing. Rapid and on-site detection, low cost instrumentation and a reusable optical probe have been emphasized throughout the study.

  19. Characterization of multienzyme-antibody-carbon nanotube bioconjugates for immunosensors.

    PubMed

    Jensen, Gary C; Yu, Xin; Gong, Joseph D; Munge, Bernard; Bhirde, Ashwin; Kim, Sang N; Papadimitrakopoulos, Fotios; Rusling, James F

    2009-01-01

    Characterization studies of a multi-enzyme-antibody-carbon nanotube bioconjugate designed for the amplification of electrochemical immunosensing are described. Secondary antibodies for prostate specific antigen (PSA) were covalently linked to highly carboxylated multi-walled carbon nanotube (CNT) along with multiple horseradish peroxidase (HRP) enzyme labels. These bioconjugates provide ultra-sensitive amperometric detection of PSA on a single-wall carbon nanotube forest sandwich immunosensor platform. A single layer of HRP on the surface of the CNT was suggested by images from atomic force microscopy (AFM) and transmission electron microscopy (TEM). HRP on the bioconjugate surface was visualized by confocal microscopy using in-situ HRP-catalyzed polymerization yielding a fluorescent product, and HRP activity was estimated in a conventional assay. Binding of quantum-dot labeled PSA to antibodies on the bioconjugate was used for visualization by TEM. Combining TEM and enzyme activity results gave estimates of approximately 82 HRPs and 30 +/- 15 secondary antibodies per 100 nm of antibody-HRP-CNT bioconjugate. PMID:19441303

  20. Racetrack micro-resonators based on ridge waveguides made of porous silica

    NASA Astrophysics Data System (ADS)

    Girault, P.; Lorrain, N.; Lemaitre, J.; Poffo, L.; Guendouz, M.; Hardy, I.; Gadonna, M.; Gutierrez, A.; Bodiou, L.; Charrier, J.

    2015-12-01

    The fabrication of micro-resonators, made from porous silica ridge waveguides by using an electrochemical etching method of silicon substrate followed by thermal oxidation and then by a standard photolithography process, is reported. The design and fabrication process are described including a study of waveguide dimensions that provide single mode propagation and calculation of the coupling ratio between a straight access waveguide and the racetrack resonator. Scanning electronic microscopy observations and optical characterizations clearly show that the micro-resonator based on porous silica ridge waveguides has been well implemented. This porous micro-resonator is destined to be used as an optical sensor. The porous nature of the ridge waveguide constitutes the detection medium which will enhance the sensor sensitivity compared to usual micro-resonators based on the evanescent wave detection. A theoretical sensitivity of 1170 nm per refractive index unit has been calculated, taking into consideration experimental data obtained from the optical characterizations.

  1. Electrochemical immunosensor assay (EIA) for sensitive detection of E. coli O157:H7 with signal amplification on a SG-PEDOT-AuNPs electrode interface.

    PubMed

    Guo, Yuna; Wang, Yu; Liu, Su; Yu, Jinghua; Wang, Hongzhi; Cui, Min; Huang, Jiadong

    2015-01-21

    A novel electrochemical immunosensor assay (EIA) for highly sensitive and specific detection of Escherichia coli O157:H7 has been developed. This immunosensor is constructed by the assembly of capture antibody on SG-PEDOT-AuNPs composites modified glass carbon electrode. In the presence of target E. coli O157:H7, horseradish peroxidase (HRP)-labeled antibody is captured on the electrode surface to form a sandwich-type system via the specific identification. As a result, E. coli O157:H7 detection is realized by outputting a redox current from electro-reduction of hydrogen peroxide reaction catalyzed by HRP. In our assay, the combination of the unique properties of sulfonated graphene (SG) and gold nanoparticles (AuNPs) can not only accelerate electron transfer on electrode interface, but also provide an excellent scaffold for the conjugation of capture antibody that significantly improves the target capture efficiency and enhances the sensitivity of the biosensor. The results reveal the calibration plot obtained for E. coli O157:H7 is approximately linear from 7.8 × 10-7.8 × 10(6) colony-forming unit (cfu) mL(-1) with the limit of detection of 3.4 × 10 cfu mL(-1). In addition, the biosensor has been successfully applied to the quantitative assay of E. coli O157:H7 in synthetic samples (spring water and milk). Hence, the developed electrochemical-based immunosensor might provide a useful and practical tool for E. coli O157:H7 determination and related food safety analysis and clinical diagnosis. PMID:25412211

  2. A New Z-axis Resonant Micro-Accelerometer Based on Electrostatic Stiffness

    PubMed Central

    Yang, Bo; Wang, Xingjun; Dai, Bo; Liu, Xiaojun

    2015-01-01

    Presented in the paper is the design, the simulation, the fabrication and the experiment of a new z-axis resonant accelerometer based on the electrostatic stiffness. The new z-axis resonant micro-accelerometer, which consists of a torsional accelerometer and two plane resonators, decouples the sensing movement of the accelerometer from the oscillation of the plane resonators by electrostatic stiffness, which will improve the performance. The new structure and the sensitive theory of the acceleration are illuminated, and the equation of the scale factor is deduced under ideal conditions firstly. The Ansys simulation is implemented to verify the basic principle of the torsional accelerometer and the plane resonator individually. The structure simulation results prove that the effective frequency of the torsional accelerometer and the plane resonator are 0.66 kHz and 13.3 kHz, respectively. Then, the new structure is fabricated by the standard three-mask deep dry silicon on glass (DDSOG) process and encapsulated by parallel seam welding. Finally, the detecting and control circuits are designed to achieve the closed-loop self-oscillation, to trace the natural frequency of resonator and to measure the system frequency. Experimental results show that the new z-axis resonant accelerometer has a scale factor of 31.65 Hz/g, a bias stability of 727 μg and a dynamic range of over 10 g, which proves that the new z-axis resonant micro-accelerometer is practicable. PMID:25569748

  3. A new z-axis resonant micro-accelerometer based on electrostatic stiffness.

    PubMed

    Yang, Bo; Wang, Xingjun; Dai, Bo; Liu, Xiaojun

    2015-01-01

    Presented in the paper is the design, the simulation, the fabrication and the experiment of a new z-axis resonant accelerometer based on the electrostatic stiffness. The new z-axis resonant micro-accelerometer, which consists of a torsional accelerometer and two plane resonators, decouples the sensing movement of the accelerometer from the oscillation of the plane resonators by electrostatic stiffness, which will improve the performance. The new structure and the sensitive theory of the acceleration are illuminated, and the equation of the scale factor is deduced under ideal conditions firstly. The Ansys simulation is implemented to verify the basic principle of the torsional accelerometer and the plane resonator individually. The structure simulation results prove that the effective frequency of the torsional accelerometer and the plane resonator are 0.66 kHz and 13.3 kHz, respectively. Then, the new structure is fabricated by the standard three-mask deep dry silicon on glass (DDSOG) process and encapsulated by parallel seam welding. Finally, the detecting and control circuits are designed to achieve the closed-loop self-oscillation, to trace the natural frequency of resonator and to measure the system frequency. Experimental results show that the new z-axis resonant accelerometer has a scale factor of 31.65 Hz/g, a bias stability of 727 µg and a dynamic range of over 10 g, which proves that the new z-axis resonant micro-accelerometer is practicable. PMID:25569748

  4. Modified screen printed electrode for development of a highly sensitive label-free impedimetric immunosensor to detect amyloid beta peptides.

    PubMed

    Lien, Truong T N; Takamura, Yuzuru; Tamiya, Eiichi; Vestergaard, Mun'delanji C

    2015-09-10

    Alzheimer's disease (AD) is a fatal neurodegenerative disease affecting approximately 26 million people world-wide, and the number is increasing as life expectancy increases. Since the only reliable diagnosis for the pathology is histochemical post-mortem examination, there is a rather urgent need for reliable, sensitive and quick detection techniques. Amyloid beta, being one of the established and widely accepted biomarkers of AD is a target biomolecule. Herein, we present fabrication of a labelless impedimetric amyloid beta immunosensor on carbon DEP (disposable electrochemical printed) chip. Three types of amyloid β impedimetric immunosensors were fabricated in a systematic step-wise manner in order to understand the effects that each surface modification chemistry had on detection sensitivity. We found that compared to a bare electrode, surface modification through formation of SAM of AuNPs increased sensitivity by approximately three orders of magnitude (LoD from 2.04 μM to 2.65 nM). A further modification using protein G, which helps orientate antibodies to an optimum position for interaction with antigen, lowered the LoD further to 0.57 nM. We have demonstrated that the presence of one of the most abundance proteins in biological fluids, bovine serum albumin (BSA), did not interfere with the sensitivity of the sensor. Since the DEP chips are disposable and the detection platform label-free, the developed sensor is relatively fast and cheap. These methods could easily be applied for detection of other antigens, with selection of the detection platform based on the desired for sensitivity. PMID:26388476

  5. A wideband deflected reflection based on multiple resonances

    NASA Astrophysics Data System (ADS)

    Chen, Hongya; Ma, Hua; Wang, Jiafu; Qu, Shaobo; Li, Yongfeng; Wang, Jun; Yan, Mingbao; Pang, Yongqiang

    2015-07-01

    We propose to realize wideband deflected reflection in microwave regime through multiple resonances. A wideband deflected reflection of a phase gradient metasurface is designed using a double-head arrow structure, which has demonstrated an ultra-wideband cross-polarized reflection caused by multiple electric and magnetic resonances. The wideband effect benefits from the wideband cross-polarized reflection and flexible phase modulation of the double-head arrow structure. Simulated and experimental results agree well with theoretical predictions. Furthermore, relative bandwidths of deflected reflection reach to 71 % for both x- and y-polarized waves under normal incidence. Our method of expansion bandwidth may pave the way in many practical applications, such as RCS reduction, stealth surfaces.

  6. Long-base free electron laser resonant cavity

    SciTech Connect

    Miller, E.L.; Bender, S.C.; Appert, Q.D.; Saxman, A.C.; Swann, T.A.

    1985-01-01

    A 65-meter resonant cavity has been constructed in order to experimentally determine the characteristics of long resonant cavities as would be required for a free electron laser (FEL). A version using normal incidence mirrors is reported here, and another that includes a grazing incidence mirror is forthcoming. Either version is designed to simulate a FEL operating at 0.5 micron wavelength and is near-concentric with a stability parameter of 0.98. Argon-ion plasma tubes simulate the laser gain that would be provided by a wiggler in an actual FEL. The cavity was constructed on a seismic slab and air turbulence effects were reduced by surrounding the beam with helium in 6 in. diameter tubes. Alignment sensitivities are reported and compared to geometrical and diffraction predictions with good agreement.

  7. Spin microscope based on optically detected magnetic resonance

    SciTech Connect

    Berman, Gennady P.; Chernobrod, Boris M.

    2009-11-10

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of impaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  8. Spin microscope based on optically detected magnetic resonance

    SciTech Connect

    Berman, Gennady P.; Chernobrod, Boris M.

    2010-06-29

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  9. Spin microscope based on optically detected magnetic resonance

    SciTech Connect

    Berman, Gennady P.; Chernobrod, Boris M.

    2010-07-13

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  10. Spin microscope based on optically detected magnetic resonance

    SciTech Connect

    Berman, Gennady P.; Chernobrod, Boris M.

    2009-10-27

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  11. Spin microscope based on optically detected magnetic resonance

    DOEpatents

    Berman, Gennady P.; Chernobrod, Boris M.

    2007-12-11

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  12. Diagnostic measurements of CUEBIT based on the dielectronic resonance process

    SciTech Connect

    Takacs, E. Kimmel, T. D. Brandenburg, K. H. Wilson, R. K. Gall, A. C. Harriss, J. E. Sosolik, C. E.

    2015-01-09

    In this paper we report the first observation of x-ray radiation from the new Clemson University Electron Beam Ion Trap (CUEBIT). The analysis of the emitted dielectronic recombination x-ray photons from highly charged argon ions allowed us to probe parameters specific to the ion cloud inside the machine. Argon dielectronic resonances could provide a standard method to cross-compare the electron beam and ion cloud characteristics of different devices.

  13. Miniature hemispherical shell resonator with large-scale effective electrodes based on piezoelectric drive mechanism.

    PubMed

    Tang, Jian; Zhang, Weiping; Cheng, Yuxiang; Liu, Wu; Wang, Yinghai; Sun, Dianjun

    2016-05-01

    Miniature resonators with three-dimensional curved surface are mostly driven by electrostatic capacitive. However, it is quite difficult to fabricate a curved surface electrostatic resonator with large-scale effective electrodes. This paper presents the first miniature hemispherical shell resonator with large-scale effective electrodes based on piezoelectric drive mechanism. The vibrating body and electrodes of the piezoelectric resonator are easily integrated without micro-scale or nano-scale narrow capacitive gap. Vibration experiment and finite element analysis both reveal that there exist seven significant vibration modes between 10 kHz and 100 kHz. Mode shape validation is also carried out by measuring the vibration velocity of upper perimeter and lateral perimeter with laser doppler vibrometer. Special vibration characteristics of each vibration mode are described in detail, based on which the resonator may be used for many specific applications. Compared with common electrostatic resonators, even smaller drive voltage applied to the piezoelectric resonator may produce larger vibration displacement at atmosphere. According to the experiment results, the resonator may provide a new way of realizing high performance three-dimensional miniature devices for communication and inertial navigation applications. PMID:27250463

  14. A new nonlinear model for analyzing the behaviour of carbon nanotube-based resonators

    NASA Astrophysics Data System (ADS)

    Farokhi, Hamed; Païdoussis, Michael P.; Misra, Arun K.

    2016-09-01

    The present study develops a new size-dependent nonlinear model for the analysis of the behaviour of carbon nanotube-based resonators. In particular, based on modified couple stress theory, the fully nonlinear equations of motion of the carbon nanotube-based resonator are derived using Hamilton's principle, taking into account both the longitudinal and transverse displacements. Molecular dynamics simulation is then performed in order to verify the validity of the developed size-dependent continuum model at the nano scale. The nonlinear partial differential equations of motion of the system are discretized by means of the Galerkin technique, resulting in a high-dimensional reduced-order model of the system. The pseudo-arclength continuation technique is employed to examine the nonlinear resonant behaviour of the carbon nanotube-based resonator. A new universal pull-in formula is also developed for predicting the occurrence of the static pull-in and validated using numerical simulations.

  15. Low dissipative mechanical resonators based on WSe2 monolayers

    NASA Astrophysics Data System (ADS)

    Morell, Nicolas; Reserbat-Plantey, Antoine; Tsioutsios, Ioannis; Schadler, Kevin; Dubin, Francois; Koppens, Frank; Bachtold, Adrian; QuantumNanoMechanics Team; NanoOptoElectronics Team; Nanostructures et systèmes quantiques Team

    Atomically thin nano-electromechanical systems (2D-NEMS) combine low mass resonators having resonant frequencies in the MHz-GHz range, wide tunability and low damping. Atomically thin 2D semi-conductors, such as transition metal dichalcogenides (TMD), have rich optical properties (direct band gap, spin valley, embedded quantum emitters...), which are linked to their low dimensionality. While optical and electronic properties of WSe2 have been intensively investigated, there have not been any studies on WSe2 mechanical resonators. Although TMD NEMs have been fabricated, they have not been measured at cryogenic temperature so far. I will present a new semiconductor 2D-NEMS made of a single layer of WSe2. We measured mechanical and photoluminescence spectra of WSe2 suspended drums at cryogenic temperatures. Our results demonstrate an extremely low damping at low temperature with a quality factor Q >47000 at T =3K, which is higher than what can be achieved with graphene NEMs. In addition, we investigated photothermal and optoelectronic effects on the mechanical degree of freedom, revealing the high potential of semiconductor 2D-NEMS for optomechanics experiments.

  16. Quantum well micro-resonator optical modulator based on electrically controlled coupling

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Taylor, Geoff W.

    2013-09-01

    Micro-resonator optical modulators fabricated with Si/SiO2 planar waveguides have been reported for the optical interconnect application and the modulation is achieved by control of the resonant frequency through resonator index change. In these devices, thermal control is used to adjust/stabilize the resonant frequency and the input coupling constant. In this paper, an III-V based micro-resonator is described in which the modulation is achieved through voltage control of the input coupling parameter and the resonator frequency is adjusted/stabilized through control of the resonator index. This approach offers significant advantages for integrated circuit based optical connectivity. The modulator performance is analyzed via FDTD simulation with refractive index profiles based on measured absorption parameters. The performance is confirmed via MATLAB and a circuit based model for HSPICE is developed and run in a transient simulator to confirm the modulator speed and eye diagram characteristics yielding an extinction ratio of 10.7 dB, a bandwidth of 31 GHz and a energy consumption <2.5 fJ/bit for device dimensions of 28×4 µm2.

  17. Vibration analysis of carbon nanotube-based resonator using nonlocal elasticity theory

    NASA Astrophysics Data System (ADS)

    Natsuki, Toshiaki; Matsuyama, Nobuhiro; Ni, Qing-Qing

    2015-09-01

    Carbon nanotubes (CNTs) are nanomaterials with extremely favorable mass sensor properties. In this paper, we propose that CNTs under clamped boundary condition and an axial tensile load are considered as CNT-based resonators. Moreover, the resonant frequencies and frequency shifts of the CNTs with attached nanomass are investigated based on vibration analysis, which used the nonlocal Euler-Bernoulli beam model. Using the present methods, we analyze and discuss the effects of the aspect ratio, the concentrated mass and the axial force on the resonant frequency of the CNTs. The results indicate that the CNT beam under the axial tensile loads could provide higher sensitivity as nanomechanical mass sensor.

  18. Quantitative evaluation of proteins with bicinchoninic acid (BCA): resonance Raman and surface-enhanced resonance Raman scattering-based methods.

    PubMed

    Chen, Lei; Yu, Zhi; Lee, Youngju; Wang, Xu; Zhao, Bing; Jung, Young Mee

    2012-12-21

    A rapid and highly sensitive bicinchoninic acid (BCA) reagent-based protein quantitation tool was developed using competitive resonance Raman (RR) and surface-enhanced resonance Raman scattering (SERRS) methods. A chelation reaction between BCA and Cu(+), which is reduced by protein in an alkaline environment, is exploited to create a BCA-Cu(+) complex that has strong RR and SERRS activities. Using these methods, protein concentrations in solutions can be quantitatively measured at concentrations as low as 50 μg mL(-1) and 10 pg mL(-1). There are many advantages of using RR and SERRS-based assays. These assays exhibit a much wider linear concentration range and provide an additional one (RR method) to four (SERRS method) orders of magnitude increase in detection limits relative to UV-based methods. Protein-to-protein variation is determined using a reference to a standard curve at concentrations of BSA that exhibits excellent recoveries. These novel methods are extremely accurate in detecting total protein concentrations in solution. This improvement in protein detection sensitivity could yield advances in the biological sciences and medical diagnostic field and extend the applications of reagent-based protein assay techniques. PMID:23099478

  19. A highly integrated FPGA-based nuclear magnetic resonance spectrometer

    NASA Astrophysics Data System (ADS)

    Takeda, Kazuyuki

    2007-03-01

    The digital circuits required for a nuclear magnetic resonance (NMR) spectrometer, including a pulse programmer, a direct digital synthesizer, a digital receiver, and a PC interface, have been built inside a single chip of the field-programmable gate-array (FPGA). By combining the FPGA chip with peripheral analog components, a compact, laptop-sized homebuilt spectrometer has been developed, which is capable of a rf output of up to 400 MHz with amplitude-, phase-, frequency-, and pulse-modulation. The number of rf channels is extendable up to three without further increase in size.

  20. Autoparametric Resonance Systems for Vibration-Based Energy Harvesters

    NASA Astrophysics Data System (ADS)

    Kurmann, L.; Hoffmann, D.; Folkmer, B.; Manoli, Y.; Woias, P.; Anderegg, R.

    2015-12-01

    Motivation for this paper is the creation of a new kind of (vibration) kinetic energy harvester systems that can effectively transfer environmental mechanical vibrations into electrical energy over a wider frequency bandwidth than conventional devices. This paper presents a potential improvement in the 1DoF vibration transducer class and examining therefore analytically the behavior of such systems using strong nonlinear springs. Then a new 2DoF class of vibration transducer is presented having a strong nonlinear characteristic which is well suited for autoparametric resonance vibrations.

  1. A study of biofunctionalized silica nanospring surface for immunosensor applications

    NASA Astrophysics Data System (ADS)

    Timalsina, Yukta P.; McIlroy, David N.

    2012-02-01

    A study of biofunctionalized VANS (vertically aligned (silica) nanospring) surface for immunosensor applications is presented. VANS surface treated with 3-aminopropyltriethoxysilane (APTES) leaves a primary amine groups on the VANS surface. Glutaraldehyde (GA) reacts with APTES modified VANS surface forming imine bonds at one end of glutaraldehyde, leaving aldehyde groups at the other end to react with the antibody. X-ray photoelectron study verifies each step of VANS surface functionalization. A goat anti mouse antibody (GαM IgG I) is immobilized as a biorecognition layer on the APTES-GA modified surface and targeted to mouse IgG. It is investigated that mouse IgG captured from the solution phase specifically binds to goat anti mouse IgG on APTES-GA- GαM IgG I. Then layer of GαM IgG II attached to the APTES-GA- GαM IgG I-mouse IgG surface reacts only when there is mouse IgG instead of rabbit IgG. A modeling of a resistor-inductor-capacitor (RLC) circuit of impedance spectra measured after the addition of successive layer indicates the these biological layers behave as insulating layers. It is explored that there is a greater magnitude of change between successive bio-layers below 10 kHz. Changes in the magnitudes of the elements of the RLC equivalent circuit indicate that the addition of biological layers impedes ionic motion thereby changing the effective dielectric response by the biomolecule polarization.

  2. A method for correlating in vivo prostate magnetic resonance imaging and histopathology using individualized magnetic resonance -based molds

    NASA Astrophysics Data System (ADS)

    Shah, Vijay; Pohida, Thomas; Turkbey, Baris; Mani, Haresh; Merino, Maria; Pinto, Peter A.; Choyke, Peter; Bernardo, Marcelino

    2009-10-01

    A method for the design and rapid manufacture of a patient specific tissue slicing device based on in vivo images in order to facilitate the process of correlating the images with histopathology is presented. The method is applied to radical prostatectomy specimens where the customized mold is designed using magnetic resonance (MR) images of each patient obtained prior to surgery. In this case, the mold holds the prostate in place while a knife with a single blade or multiple blades is inserted in slots which are positioned to obtain tissue blocks corresponding to the slices in the MR images. The resulting histological specimens demonstrate good anatomical correlation with the MR images.

  3. Novel signal amplification strategy for ultrasensitive sandwich-type electrochemical immunosensor employing Pd-Fe3O4-GS as the matrix and SiO2 as the label.

    PubMed

    Wang, Yulan; Ma, Hongmin; Wang, Xiaodong; Pang, Xuehui; Wu, Dan; Du, Bin; Wei, Qin

    2015-12-15

    An ultrasensitive sandwich-type electrochemical immunosensor based on a novel signal amplification strategy was developed for the quantitative determination of human immunoglobulin G (IgG). Pd nanocubes functionalized magnetic graphene sheet (Pd-Fe3O4-GS) was employed as the matrix to immobilize the primary antibodies (Ab1). Owing to the synergetic effect between Pd nanocubes and magnetic graphene sheet (Fe3O4-GS), Pd-Fe3O4-GS can provide an obviously increasing electrochemical signal by electrochemical catalysis towards hydrogen peroxide (H2O2). Silicon dioxide (SiO2) was functionalized as the label to conjugate with the secondary antibodies (Ab2). Due to the larger steric hindrance of the obtained conjugate (SiO2@Ab2), the sensitive decrease of the electrochemical signal can be achieved after the specific recognition between antibodies and antigens. In this sense, this proposed immunosensor can achieve a high sensitivity, especially in the presence of low concentrations of IgG. Under optimum conditions, the proposed immunosensor offered an ultrasensitive and specific determination of IgG down to 3.2 fg/mL. This immunoassay method would open up a new promising platform to detect various tumor markers at ultralow levels for early diagnoses of different cancers. PMID:26120810

  4. Optically tunable Fano resonance in a grating-based Fabry-Perot cavity-coupled microring resonator on a silicon chip.

    PubMed

    Zhang, Weifeng; Li, Wangzhe; Yao, Jianping

    2016-06-01

    A grating-based Fabry-Perot (FP) cavity-coupled microring resonator on a silicon chip is reported to demonstrate an all-optically tunable Fano resonance. In the device, an add-drop microring resonator (MRR) is employed, and one of the two bus waveguides is replaced by an FP cavity consisting of two sidewall Bragg gratings. By choosing the parameters of the gratings, the resonant mode of the FP cavity is coupled to one of the resonant modes of the MRR. Due to the coupling between the resonant modes, a Fano resonance with an asymmetric line shape resulted. Measurement results show a Fano resonance with an extinction ratio of 22.54 dB, and a slope rate of 250.4 dB/nm is achieved. A further study of the effect of the coupling on the Fano resonance is performed numerically and experimentally. Thanks to the strong light-confinement capacity of the MRR and the FP cavity, a strong two-photon absorption induced nonlinear thermal-optic effect resulted, which is used to tune the Fano resonance optically. PMID:27244392

  5. Compact interferometer transducer based on surface plasmon phase resonance.

    PubMed

    Hadjar, Yassine; Renault, Mikael; Blaize, Sylvain; Bruyant, Aurélien; Vincent, Rémi; Hmima, Abdelhamid

    2015-05-01

    We propose a new monolithic interferometric configuration and implement a novel method for spectroscopic phase shift detection of surface plasmon resonance (SPR) sensors. The interference pattern is obtained using a nonpolarizing beam splitter cube with two attached right angle prisms in such a way that each interference field undergoes two total internal reflections (TIR) at prisms/air interface and one attenuated total reflection (ATR) through surface plasmon interaction. The evanescent part of the interferogram around the Zero optical path difference (ZOPD) is sampled and detected in the far field, thanks to a bidimensional array of scattering optical near-field probes deposited on the corresponding prism surface. A Fourier transform of the sampled interferogram is performed to measure the input light wavelength, while a direct comparison of the interferogram in TM and TE polarization modes allows us to determine the differential phase shift induced by the SPR layer. The phase shift measurement is made possible thanks to a remarkable time stability of the interferogram in the glass bulk. By tuning the input laser wavelength around the resonance, we show a good agreement between experimental and theoretical calculations for both amplitude and phase spectral responses. PMID:26366899

  6. Raman resonance in iron-based superconductors: The magnetic scenario

    NASA Astrophysics Data System (ADS)

    Hinojosa, Alberto; Cai, Jiashen; Chubukov, Andrey V.

    2016-02-01

    We perform theoretical analysis of polarization-sensitive Raman spectroscopy on NaFe1 -xCoxAs , EuFe 2 As2 , SrFe2As2 , and Ba (Fe1 -xCox )2As2 , focusing on two features seen in the B1 g symmetry channel (in one Fe unit cell notation): the strong temperature dependence of the static, uniform Raman response in the normal state and the existence of a collective mode in the superconducting state. We show that both features can be explained by the coupling of fermions to pairs of magnetic fluctuations via the Aslamazov-Larkin process. We first analyze magnetically mediated Raman intensity at the leading two-loop order and then include interactions between pairs of magnetic fluctuations. We show that the full Raman intensity in the B1 g channel can be viewed as the result of the coupling of light to Ising-nematic susceptibility via Aslamazov-Larkin process. We argue that the singular temperature dependence in the normal state is the combination of the temperature dependencies of the Aslamazov-Larkin vertex and of Ising-nematic susceptibility. We discuss two scenario for the resonance below Tc. One is the resonance due to development of a pole in the fully renormalized Ising-nematic susceptibility. Another is orbital excitonic scenario, in which spin fluctuations generate attractive interaction between low-energy fermions.

  7. Comparison of gold- and graphene-based resonant nanostructures for terahertz metamaterials and an ultrathin graphene-based modulator

    SciTech Connect

    Shen, Nian-Hai; Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M

    2014-09-01

    Graphene exhibits unique material properties, and in electromagnetic wave technology it raises the prospect of devices miniaturized down to the atomic length scale. Here we study split-ring resonator metamaterials made from graphene and we compare them to gold-based metamaterials. We find that graphene's huge reactive response derived from its large kinetic inductance allows for deeply subwavelength resonances, although its resonance strength is reduced due to higher dissipative loss damping and smaller dipole coupling. Nevertheless, tightly stacked graphene rings may provide for negative permeability and the electric dipole resonance of graphene meta-atoms turns out to be surprisingly strong. Based on these findings, we present a terahertz modulator based on a metamaterial with a multilayer stack of alternating patterned graphene sheets separated by dielectric spacers. Neighboring graphene flakes are biased against each other, resulting in modulation depths of over 75% at a transmission level of around 90%.

  8. Study of node and mass sensitivity of resonant mode based cantilevers with concentrated mass loading

    SciTech Connect

    Zhang, Kewei Chai, Yuesheng; Fu, Jiahui

    2015-12-15

    Resonant-mode based cantilevers are an important type of acoustic wave based mass-sensing devices. In this work, the governing vibration equation of a bi-layer resonant-mode based cantilever attached with concentrated mass is established by using a modal analysis method. The effects of resonance modes and mass loading conditions on nodes and mass sensitivity of the cantilever were theoretically studied. The results suggested that the node did not shift when concentrated mass was loaded on a specific position. Mass sensitivity of the cantilever was linearly proportional to the square of the point displacement at the mass loading position for all the resonance modes. For the first resonance mode, when mass loading position x{sub c} satisfied 0 < x{sub c} < ∼ 0.3l (l is the cantilever beam length and 0 represents the rigid end), mass sensitivity decreased as the mass increasing while the opposite trend was obtained when mass loading satisfied ∼0.3l ≤ x{sub c} ≤ l. Mass sensitivity did not change when concentrated mass was loaded at the rigid end. This work can provide scientific guidance to optimize the mass sensitivity of a resonant-mode based cantilever.

  9. Uncooled resonant infrared detector based on aluminum nitride piezoelectric film through charge generations and lattice absorptions

    NASA Astrophysics Data System (ADS)

    Ang, W. C.; Kropelnicki, P.; Zhu, Y.; Randles, A. B.; Gu, Y. A.; Leong, K. C.; Tan, C. S.

    2014-05-01

    This Letter demonstrates an aluminum nitride (AlN) based uncooled resonant infrared (IR) detector utilizing the photo-sensitive and piezoelectric properties of polycrystalline AlN. The AlN Lamb wave mode resonator is found responsive to IR illuminations by showing a decrease in the S21 magnitude instead of a resonant frequency shift. A -0.08 dB shift of S21 magnitude was observed for an IR incident power of 647 nW, which translates to a responsivity of 124 kdB/W. Photoresponse is proposed for the IR sensing mechanism through additional charge carriers generation rather than thermal effects.

  10. Microwave bandpass filters based on thin-film acoustic resonators: theory and experiment

    NASA Astrophysics Data System (ADS)

    Dvoesherstov, M. Yu.; Cherednik, V. I.

    2015-11-01

    We theoretically and experimentally analyze microwave thin-film acoustoelectronic bandpass ladder filters built on AlN-based thin-film acoustoelectronic microwave resonators operating in the frequency range 4.6-5 GHz and describe the technology of their fabrication. We demonstrate that the parameters of filters are mainly determined by the characteristics of resonators that make up the filter and show that the characteristics of a three-section ladder filter can be significantly improved by optimizing the areas of the upper electrodes of the series and parallel resonators contained in it.

  11. Helmholtz resonance in a piezoelectric-hydraulic pump-based hybrid actuator

    NASA Astrophysics Data System (ADS)

    Kim, Gi-Woo; Wang, K. W.

    2011-01-01

    This paper demonstrates that a hydraulically acting Helmholtz resonator can exist in a piezoelectric-hydraulic pump (PHP) based hybrid actuator, which in turn affects the volumetric efficiency of the PHP. The simulation and experimental results illustrate the effect of Helmholtz resonance on the flow rate performance of the PHP. The study also shows how to shift the Helmholtz resonant frequency to a higher value through changing parameters such as the cylinder diameter and the effective bulk modulus of the working fluid, which will improve the volumetric efficiency and broaden the operating frequency range of the PHP actuator.

  12. Deep-Subwavelength-Scale Directional Sensing Based on Highly Localized Dipolar Mie Resonances

    NASA Astrophysics Data System (ADS)

    Zhu, Xuefeng; Liang, Bin; Kan, Weiwei; Peng, Yugui; Cheng, Jianchun

    2016-05-01

    This paper reports the formation of highly localized Mie resonances on a closed metasurface encapsulating a rigid core and the realization of directional sensing at deep-subwavelength scale (diameter ˜λ /8 ) with the proposed physical model. Based on modal-expansion and mode-matching methods, it is theoretically shown that the extremely anisotropic metasurface shell can support varied orders of Mie resonances around the rigid core. We further experimentally demonstrate that the Mie resonance with a dipolelike profile is strongly excited under the illumination of a plane wave at low frequencies, enabling the sensitive directional sensing due to the intensified and azimuthally dependent pressure field.

  13. A new resonant based measurement method for squeeze mode yield stress of magnetorheological fluids

    NASA Astrophysics Data System (ADS)

    Kaluvan, Suresh; Shah, Kruti; Choi, Seung-Bok

    2014-10-01

    A new approach to measure the field-dependent yield stress of magnetorheological (MR) fluids in squeeze mode using the resonance concept is proposed. The measurement system is designed using the piezolaminated cantilever beam coupled with an electromagnetic coil based MR fluid squeezing setup. The cantilever beam is maintained at resonance using simple closed-loop electronics. The magnetic field produced by the coil changes the viscosity of MR fluids and produces an additional stiffness to the resonating cantilever beam. The shift in resonant frequency due to the change in viscosity of the MR fluid is measured, and the shift in frequency is analytically related to the yield stress. Two types of MR fluids based on sphere and plate iron particles are used to demonstrate the effectiveness of the proposed measurement system.

  14. Magnetic resonance imaging and cell-based neurorestorative therapy after brain injury

    PubMed Central

    Jiang, Quan

    2016-01-01

    Restorative cell-based therapies for experimental brain injury, such as stroke and traumatic brain injury, substantially improve functional outcome. We discuss and review state of the art magnetic resonance imaging methodologies and their applications related to cell-based treatment after brain injury. We focus on the potential of magnetic resonance imaging technique and its associated challenges to obtain useful new information related to cell migration, distribution, and quantitation, as well as vascular and neuronal remodeling in response to cell-based therapy after brain injury. The noninvasive nature of imaging might more readily help with translation of cell-based therapy from the laboratory to the clinic. PMID:26981068

  15. A resonance ionization imaging detector based on cesium atomic vapor

    NASA Astrophysics Data System (ADS)

    Temirov, J. P.; Chigarev, N. V.; Matveev, O. I.; Omenetto, N.; Smith, B. W.; Winefordner, J. D.

    2004-05-01

    A novel Cs resonance ionization imaging detector (RIID) has been developed and evaluated. The detector is capable of two-dimensional imaging with high spectral resolution, which is determined by the Doppler broadened atomic linewidth of Cs at given temperature. Ionization schemes of Cs have been investigated using dye and color center tunable lasers pumped by an excimer laser and by a Nd:YAG laser. It has been experimentally shown that the most efficient ionization scheme for Cs RIID should include a three-step excitation/ionization ladder, for example, with transitions at λ1=852.11 (852.113) nm, λ2=917.22 (917.2197) nm, and λ3=1064 nm. The imaging capabilities of the detector have been evaluated using a simpler two-step ionization scheme with wavelengths λ1=852.11 nm and λ2=508 nm.

  16. Surface Plasmon Resonance for Cell-Based Clinical Diagnosis

    PubMed Central

    Yanase, Yuhki; Hiragun, Takaaki; Ishii, Kaori; Kawaguchi, Tomoko; Yanase, Tetsuji; Kawai, Mikio; Sakamoto, Kenji; Hide, Michihiro

    2014-01-01

    Non-invasive real-time observations and the evaluation of living cell conditions and functions are increasingly demanded in life sciences. Surface plasmon resonance (SPR) sensors detect the refractive index (RI) changes on the surface of sensor chips in label-free and on a real-time basis. Using SPR sensors, we and other groups have developed techniques to evaluate living cells' reactions in response to stimuli without any labeling in a real-time manner. The SPR imaging (SPRI) system for living cells may visualize single cell reactions and has the potential to expand application of SPR cell sensing for clinical diagnosis, such as multi-array cell diagnostic systems and detection of malignant cells among normal cells in combination with rapid cell isolation techniques. PMID:24618778

  17. Analysis and design of terahertz antennas based on plasmonic resonant graphene sheets

    SciTech Connect

    Tamagnone, M.; Gomez-Diaz, J. S.; Perruisseau-Carrier, J.

    2012-12-01

    Resonant graphene antennas used as true interfaces between terahertz (THz) space waves and a source/detector are presented. It is shown that in addition to the high miniaturization related to the plasmonic nature of the resonance, graphene-based THz antenna favorably compare with typical metal implementations in terms of return loss and radiation efficiency. Graphene antennas will contribute to the development of miniature, efficient, and potentially transparent all-graphene THz transceivers for emerging communication and sensing application.

  18. Terahertz response of fractal meta-atoms based on concentric rectangular square resonators

    SciTech Connect

    Song, Zhiqiang; Zhao, Zhenyu Shi, Wangzhou; Peng, Wei

    2015-11-21

    We investigate the terahertz electromagnetic responses of fractal meta-atoms (MAs) induced by different mode coupling mechanisms. Two types of MAs based on concentric rectangular square (CRS) resonators are presented: independent CRS (I-CRS) and junctional-CRS (J-CRS). In I-CRS, each resonator works as an independent dipole so as to result in the multiple resonance modes when the fractal level is above 1. In J-CRS, however, the generated layer is rotated by π/2 radius to the adjacent CRS in one MA. The multiple resonance modes are coupled into a single mode resonance. The fractal level increasing induces resonance modes redshift in I-CRS while blueshift in J-CRS. When the fractal level is below 4, the mode Q factor of J-CRS is in between the two modes of I-CRS; when the fractal level is 4 or above, the mode Q factor of J-CRS exceeds the two modes of I-CRS. Furthermore, the modulation depth (MD) decreases in I-CRS while it increases in J-CRS with the increase in fractal levels. The surface currents analysis reveals that the capacitive coupling of modes in I-CRS results in the modes redshift, while the conductive coupling of modes in J-CRS induces the mode blueshift. A high Q mode with large MD can be achieved via conductive coupling between the resonators of different scales in a fractal MA.

  19. Flexible Non-Constrained RF Wrist Pulse Detection Sensor Based on Array Resonators.

    PubMed

    An, Yong-Jun; Kim, Byung-Hyun; Yun, Gi-Ho; Kim, Sung-Woo; Hong, Seung-Bum; Yook, Jong-Gwan

    2016-04-01

    This paper presents the development of a non-contact, nonintrusive wrist pulse sensor based on the near-field variation of an array resonator. A compact resonator and its array were designed and fabricated on flexible substrate. The reflection coefficient of the resonator can vary as a function of the distance between the resonator and the walls of the major arteries, and the corresponding variation is utilized to obtain heart rate information at the wrist. To detect very weak pulse signals from the main arteries, a sensitivity enhancement technique was devised using a radio frequency (RF) array resonator. The sensor system was implemented with an RF switch to combine or select appropriate signals from the resonator element and was tested using the 2.4 GHz ISM band. The results demonstrated the sensor system's excellent performance in both sequential and simultaneous detection schemes. The measurement results showed that a heartbeat pulse can be detected from both radial and ulnar arteries via the array resonators. Considering the high sensitivity and characteristics, the proposed detection system can be utilized as a wearable, long-term health monitoring device. PMID:25966481

  20. Detection of low levels of Listeria monocytogenes cells by using a fiber-optic immunosensor.

    PubMed

    Geng, Tao; Morgan, Mark T; Bhunia, Arun K

    2004-10-01

    Biosensor technology has a great potential to meet the need for sensitive and nearly real-time microbial detection from foods. An antibody-based fiber-optic biosensor to detect low levels of Listeria monocytogenes cells following an enrichment step was developed. The principle of the sensor is a sandwich immunoassay where a rabbit polyclonal antibody was first immobilized on polystyrene fiber waveguides through a biotin-streptavidin reaction to capture Listeria cells on the fiber. Capture of cells on the fibers was confirmed by scanning electron microscopy. A cyanine 5-labeled murine monoclonal antibody, C11E9, was used to generate a specific fluorescent signal, which was acquired by launching a 635-nm laser light from an Analyte 2000 and collected by a photodetector at 670 to 710 nm. This immunosensor was specific for L. monocytogenes and showed a significantly higher signal strength than for other Listeria species or other microorganisms, including Escherichia coli, Enterococcus faecalis, Salmonella enterica, Lactobacillus plantarum, Carnobacterium gallinarum, Hafnia alvei, Corynebacterium glutamicum, Enterobacter aerogenes, Pseudomonas aeruginosa, and Serratia marcescens, in pure or in mixed-culture setup. Fiber-optic results could be obtained within 2.5 h of sampling. The sensitivity threshold was about 4.3 x 10(3) CFU/ml for a pure culture of L. monocytogenes grown at 37 degrees C. When L. monocytogenes was mixed with lactic acid bacteria or grown at 10 degrees C with 3.5% NaCl, the detection threshold was 4.1 x 10(4) or 2.8 x 10(7) CFU/ml, respectively. In less than 24 h, this method could detect L. monocytogenes in hot dog or bologna naturally contaminated or artificially inoculated with 10 to 1,000 CFU/g after enrichment in buffered Listeria enrichment broth. PMID:15466560

  1. Demonstration of submersible high-throughput microfluidic immunosensors for underwater explosives detection.

    PubMed

    Adams, André A; Charles, Paul T; Deschamps, Jeffrey R; Kusterbeck, Anne W

    2011-11-15

    Significant security threats posed by highly energetic nitroaromatic compounds in aquatic environments and the demilitarization and pending cleanup of areas previously used for munitions manufacture and storage represent a challenge for less expensive, faster, and more sensitive systems capable of analyzing groundwater and seawater samples for trace levels of explosive materials. Presented here is an inexpensive high throughput microfluidic immunosensor (HTMI) platform intended for the rapid, highly selective quantitation of nitroaromatic compounds in the field. Immunoaffinity and fluorescence detection schemes were implemented in tandem on a novel microfluidic device containing 39 parallel microchannels that were 500 μm tall, 250 μm wide, and 2.54 cm long with covalently tethered antibodies that was engineered for high-throughput high-volume sample processing. The devices were produced via a combination of high precision micromilling and hot embossing. Mass transfer limitations were found in conventional microsystems and were minimized due to higher surface area to volume ratios that exceeded those possessed by conventional microdevices and capillaries. Until now, these assays were limited to maximum total volume flow rates of ~1 mL/min due in part to kinetics and high head pressures of single microchannels. In the design demonstrated here, highly parallelized microchannels afforded up to a 100-fold increase in total volume flow rate while maintaining favorable kinetic constraints for efficient antigen-antibody interaction. The assay employed total volume throughput of up to 6 mL/min while yielding signal-to-noise ratios of >15 in all cases. In addition to samples being processed up to 60 times faster than in conventional displacement-based immunoassays, the current system was capable of quantitating 0.01 ng/mL TNT samples without implementing offline preconcentration, thereby, demonstrating the ability to improve sensitivity by as much as 2 orders of magnitude

  2. A Label-Free Impedance Immunosensor Using Screen-Printed Interdigitated Electrodes and Magnetic Nanobeads for the Detection of E. coli O157:H7

    PubMed Central

    Wang, Ronghui; Lum, Jacob; Callaway, Zach; Lin, Jianhan; Bottje, Walter; Li, Yanbin

    2015-01-01

    Escherichia coli O157:H7 is one of the leading bacterial pathogens causing foodborne illness. In this study, an impedance immunosensor based on the use of magnetic nanobeads and screen-printed interdigitated electrodes was developed for the rapid detection of E. coli O157:H7. Magnetic nanobeads coated with anti-E. coli antibody were mixed with an E. coli sample and used to isolate and concentrate the bacterial cells. The sample was suspended in redox probe solution and placed onto a screen-printed interdigitated electrode. A magnetic field was applied to concentrate the cells on the surface of the electrode and the impedance was measured. The impedance immunosensor could detect E. coli O157:H7 at a concentration of 104.45 cfu·mL−1 (~1400 bacterial cells in the applied volume of 25 μL) in less than 1 h without pre-enrichment. A linear relationship between bacteria concentration and impedance value was obtained between 104 cfu·mL−1 and 107 cfu·mL−1. Though impedance measurement was carried out in the presence of a redox probe, analysis of the equivalent circuit model showed that the impedance change was primarily due to two elements: Double layer capacitance and resistance due to electrode surface roughness. The magnetic field and impedance were simulated using COMSOL Multiphysics software. PMID:26694478

  3. Electrochemiluminescence immunosensor using poly(l-histidine)-protected glucose dehydrogenase on Pt/Au bimetallic nanoparticles to generate an in situ co-reactant.

    PubMed

    Xiao, Lijuan; Chai, Yaqin; Wang, Haijun; Yuan, Ruo

    2014-08-21

    In this work, Pt/Au bimetallic nanoparticles (Pt/Au NPs) were used as nanocarriers to develop an electrochemiluminescence (ECL) immunosensor for sensitive cardiac troponin I (cTnI) detection, coupling with enzyme-based signal amplification. First, gold nanoparticles modified Ru(phen)3(2+)-doped silica nanoparticles (Au@RuSiO2 NPs) with numerous luminophores were used as a platform, potentially increasing the signal intensity. Second, Pt/Au NPs with large surface area and rich surface atoms were a superior matrix for the immobilization of numerous antibodies (Ab2), poly(l-histidine) (PLH) and glucose dehydrogenase (GDH). More importantly, the PLH-protected GDH exhibited excellent enzymatic activity for the oxidation of glucose accompanied by the reduction of NAD(+) to NADH. The in situ generated NADH acted as a co-reactant of Ru(phen)3(2+), significantly enhancing the ECL signal. In this manner, the designed immunosensor displayed high sensitivity for the detection of cTnI in the range of 0.010 ng mL(-1) to 10 ng mL(-1) with a detection limit of 3.3 pg mL(-1) (S/N = 3). The proposed strategy holds a new promise for highly sensitive bioassays for application in clinical analyses. PMID:24940578

  4. A Label-Free Impedance Immunosensor Using Screen-Printed Interdigitated Electrodes and Magnetic Nanobeads for the Detection of E. coli O157:H7.

    PubMed

    Wang, Ronghui; Lum, Jacob; Callaway, Zach; Lin, Jianhan; Bottje, Walter; Li, Yanbin

    2015-12-01

    Escherichia coli O157:H7 is one of the leading bacterial pathogens causing foodborne illness. In this study, an impedance immunosensor based on the use of magnetic nanobeads and screen-printed interdigitated electrodes was developed for the rapid detection of E. coli O157:H7. Magnetic nanobeads coated with anti-E. coli antibody were mixed with an E. coli sample and used to isolate and concentrate the bacterial cells. The sample was suspended in redox probe solution and placed onto a screen-printed interdigitated electrode. A magnetic field was applied to concentrate the cells on the surface of the electrode and the impedance was measured. The impedance immunosensor could detect E. coli O157:H7 at a concentration of 10(4.45) cfu·mL(-1) (~1400 bacterial cells in the applied volume of 25 μL) in less than 1 h without pre-enrichment. A linear relationship between bacteria concentration and impedance value was obtained between 10(4.45) cfu·mL(-1) and 10(7) cfu·mL(-1). Though impedance measurement was carried out in the presence of a redox probe, analysis of the equivalent circuit model showed that the impedance change was primarily due to two elements: Double layer capacitance and resistance due to electrode surface roughness. The magnetic field and impedance were simulated using COMSOL Multiphysics software. PMID:26694478

  5. Poly(dopamine) coated gold nanocluster functionalized electrochemical immunosensor for brominated flame retardants using multienzyme-labeling carbon hollow nanochains as signal amplifiers.

    PubMed

    Lin, Mouhong; Liu, Yingju; Chen, Xiaofen; Fei, Shidong; Ni, Chunlin; Fang, Yueping; Liu, Chengbin; Cai, Qingyun

    2013-07-15

    An electrochemical, signal amplified immunosensor was developed to detect 3-bromobiphenyl (BBP) by using a bio-inspired polydopamine (PDOP)/gold nanocluster (AuNc) as the sensor platform and multienzyme-labeled carbon hollow nanochains as the signal amplifier. The self-polymerized dopamine membrane on the AuNc-modified indium tin oxide (ITO) electrode were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle and electrochemical measurements. Such PDOP/AuNc platform featured the mild cross-linking reaction with the dense immobilization of BBP-antigens (BBP-Ag). Moreover, by using multiple horseradish peroxidase (HRP) and secondary antibodies (Ab2) modified one-dimensional carbon hollow nanochains (CHNc) as the signal enhancer, it held promise for improving the sensitivity and detection limit of the immunoassay. Based on the competitive immunoassay protocol, this immunosensor showed a linear range from 1 pM to 2 nM for BBP with a detection limit of 0.5 pM. Also, it exhibited high sensitivity, wide linear range, acceptable stability and reproducibility on a promising immobilization platform using a novel signal amplifier, which may extend its application in other environmental monitoring. PMID:23455046

  6. A new method for wideband characterization of resonator-based sensing platforms

    SciTech Connect

    Munir, Farasat; Wathen, Adam; Hunt, William D.

    2011-03-15

    A new approach to the electronic instrumentation for extracting data from resonator-based sensing devices (e.g., microelectromechanical, piezoelectric, electrochemical, and acoustic) is suggested and demonstrated here. Traditionally, oscillator-based circuitry is employed to monitor shift in the resonance frequency of the resonator. These circuits give a single point measurement at the frequency where the oscillation criterion is met. However, the resonator response itself is broadband and contains much more information than a single point measurement. Here, we present a method for the broadband characterization of a resonator using white noise as an excitation signal. The resonator is used in a two-port filter configuration, and the resonator output is subjected to frequency spectrum analysis. The result is a wideband spectral map analogous to the magnitude of the S21 parameters of a conventional filter. Compared to other sources for broadband excitation (e.g., frequency chirp, multisine, or narrow time domain pulse), the white noise source requires no design of the input signal and is readily available for very wide bandwidths (1 MHz-3 GHz). Moreover, it offers simplicity in circuit design as it does not require precise impedance matching; whereas such requirements are very strict for oscillator-based circuit systems, and can be difficult to fulfill. This results in a measurement system that does not require calibration, which is a significant advantage over oscillator circuits. Simulation results are first presented for verification of the proposed system, followed by measurement results with a prototype implementation. A 434 MHz surface acoustic wave (SAW) resonator and a 5 MHz quartz crystal microbalance (QCM) are measured using the proposed method, and the results are compared to measurements taken by a conventional bench-top network analyzer. Maximum relative differences in the measured resonance frequencies of the SAW and QCM resonators are 0.0004% and 0

  7. Resonant characteristics and sensitivity dependency on the contact surface in QCM-micropillar-based system of coupled resonator sensors

    NASA Astrophysics Data System (ADS)

    Kashan, M. A. M.; Kalavally, V.; Lee, H. W.; Ramakrishnan, N.

    2016-05-01

    We report the characteristics and sensitivity dependence over the contact surface in coupled resonating sensors (CRSs) made of high aspect ratio resonant micropillars attached to a quartz crystal microbalance (QCM). Through experiments and simulation, we observed that when the pillars of resonant heights were placed in maximum displacement regions the resonance frequency of the QCM increased following the coupled resonance characteristics, as the pillar offered elastic loading to the QCM surface. However, the same pillars when placed in relatively lower displacement regions, in spite of their resonant dimension, offered inertial loading and resulted in a decrease in QCM resonance frequency, as the displacement amplitude was insufficient to couple the vibrations from the QCM to the pillars. Accordingly, we discovered that the coupled resonance characteristics not only depend on the resonant structure dimensions but also on the contact regions in the acoustic device. Further analysis revealed that acoustic pressure at the contact surface also influences the resonance frequency characteristics and sensitivity of the CRS. To demonstrate the significance of the present finding for sensing applications, humidity sensing is considered as the example measurand. When a sensing medium made of resonant SU-8 pillars was placed in a maximum displacement region on a QCM surface, the sensitivity increased by 14 times in comparison to a resonant sensing medium placed in a lower displacement region of a QCM surface.

  8. Effect of pairing fluctuations on the spin resonance in Fe-based superconductors

    NASA Astrophysics Data System (ADS)

    Hinojosa, Alberto; Chubukov, Andrey V.; Wölfle, Peter

    2014-09-01

    The spin resonance observed in the inelastic neutron scattering data on Fe-based superconductors has played a prominent role in the quest for determining the symmetry of the order parameter in these compounds. Most theoretical studies of the resonance employ an RPA-type approach in the particle-hole channel and associate the resonance in the spin susceptibility χS(q,ω) at momentum Q =(π,π) with the spin-exciton of an s+- superconductor, pulled below 2Δ by residual attraction associated with the sign change of the gap between Fermi points connected by Q. Here we explore the effect of fluctuations in the particle-particle channel on the spin resonance. Particle-particle and particle-hole channels are coupled in a superconductor and to what extent the spin resonance can be viewed as a particle-hole exciton needs to be addressed. In the case of purely repulsive interactions, we find that the particle-particle channel at total momentum Q (the π channel) contributes little to the resonance. However, if the interband density-density interaction is attractive and the π resonance is possible on its own, along with spin-exciton, we find a much stronger shift of the resonance frequency from the position of the would-be spin-exciton resonance. We also show that the expected double-peak structure in this situation does not appear because of the strong coupling between particle-hole and particle-particle channels, and ImχS(Q ,ω) displays only a single peak.

  9. Firefly Luciferase-Based Sequential Bioluminescence Resonance Energy Transfer (BRET)-Fluorescence Resonance Energy Transfer (FRET) Protease Assays.

    PubMed

    Branchini, Bruce

    2016-01-01

    We describe here the preparation of ratiometric luminescent probes that contain two well-separated emission peaks produced by a sequential bioluminescence resonance energy transfer (BRET)-fluorescence resonance energy transfer (FRET) process. The probes are single soluble fusion proteins consisting of a thermostable firefly luciferase variant that catalyzes yellow-green (560 nm maximum) bioluminescence and a red fluorescent protein covalently labeled with a near-Infrared fluorescent dye. The two proteins are connected by a decapeptide containing a protease recognition site specific for factor Xa, thrombin, or caspase 3. The rates of protease cleavage of the fusion protein substrates were monitored by recording emission spectra and plotting the change in peak ratios over time. Detection limits of 0.41 nM for caspase 3, 1.0 nM for thrombin, and 58 nM for factor Xa were realized with a scanning fluorometer. This method successfully employs an efficient sequential BRET-FRET energy transfer process based on firefly luciferase bioluminescence to assay physiologically important protease activities and should be generally applicable to the measurement of any endoprotease lacking accessible cysteine residues. PMID:27424898

  10. Magnetic Resonance Based Electrical Properties Tomography: A Review

    PubMed Central

    Zhang, Xiaotong; Liu, Jiaen

    2014-01-01

    Frequency-dependent electrical properties (EPs; conductivity and permittivity) of biological tissues provide important diagnostic information (e.g. tumor characterization), and also play an important role in quantifying radiofrequency (RF) coil induced Specific Absorption Rate (SAR) which is a major safety concern in high- and ultrahigh-field Magnetic Resonance Imaging (MRI) applications. Cross-sectional imaging of EPs has been pursued for decades. Recently introduced Electrical Properties Tomography (EPT) approaches utilize the measurable RF magnetic field induced by the RF coil in an MRI system to quantitatively reconstruct the EP distribution in vivo and non-invasively with a spatial resolution of a few millimeters or less. This paper reviews the Electrical Properties Tomography approach from its basic theory in electromagnetism to the state of the art research outcomes. Emphasizing on the imaging reconstruction methods rather than experimentation techniques, we review the developed imaging algorithms, validation results in physical phantoms and biological tissues, as well as their applications in in vivo tumor detection and subject-specific SAR prediction. Challenges for future research are also discussed. PMID:24803104

  11. Surface plasmon resonance-based immunoassay for procalcitonin.

    PubMed

    Vashist, Sandeep Kumar; Schneider, E Marion; Barth, Eberhard; Luong, John H T

    2016-09-28

    A surface plasmon resonance (SPR) biosensor has been developed for rapid immunoassay of procalcitonin (PCT) with high detection sensitivity and reproducibility. The 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC)-activated protein A (PrA), diluted in 1% (v/v) 3-aminopropyltriethoxysilane (APTES) was dispensed on a KOH-treated Au-coated SPR chip, resulting in the covalent binding of PrA in 30 min. This "single-step" PrA immobilization strategy led to the oriented binding of the anti-PCT antibody (Ab) on a PrA-functionalized gold (Au) chip. The leach-proof immobilization procedure is five-fold faster than conventional counterparts, enabling high detection specificity and reproducibility. The IA detects 4-324 ng mL(-1) of PCT with a limit of detection (LOD) and a limit of quantification (LOQ) of 4.2 ng mL(-1) and 9.2 ng mL(-1), respectively. It was capable of detecting PCT in real sample matrices and patient samples with high precision. The Ab-bound SPR chips were stable for more than five weeks. PMID:27619095

  12. Electrostatic charge sensor based on a micromachined resonator with dual micro-levers

    NASA Astrophysics Data System (ADS)

    Zhao, Jiuxuan; Ding, Hong; Xie, Jin

    2015-06-01

    This paper describes an electrostatic charge sensor based on a microelectromechanical systems (MEMS) resonator with dual micro-levers to improve sensitivity. The device comprises a double-ended tuning fork resonant element working at out-of-phase mode with a quality factor (Q) of about 4900 under operating pressure of 40 mTorr. The resonant frequency shifts in proportion to an axial force induced by charge additions and then transformed by dual micro-levers with an amplification factor over 8. The measured responsivity is 1.3 × 10 - 3 Hz / fC 2 , which matches well with the results from analytical models and finite element method. The sensitivity of the charge sensor is 21 fC under 4 ppm frequency fluctuation. Additionally, electrostatic spring softening and nonlinear feature of the resonator are also investigated.

  13. Quasi-static high-resolution magnetic-field detection based on dielectric optical resonators

    NASA Astrophysics Data System (ADS)

    Ioppolo, Tindaro; Rubino, Edoardo

    2013-06-01

    In this paper we present a high resolution magnetic field sensor that is based on the perturbation of the optical modes (whispering gallery mode, WGM) of a spherical dielectric resonator. The optical resonator is side coupled to a tapered single mode optical fiber. One side of the optical fiber is coupled to a distribute feedback diode laser, while the other end is connected to a photodiode. The optical modes of the dielectric cavity are perturbed using a metglas sheet that is in contact with the resonator. When the metglas sheet is exposed to an external magnetic field it elongates perturbing the optical modes of the dielectric cavity. This in turn leads to a shift in the optical resonances. By measuring the induced WGM shift the magnetic field can be measured. Preliminary results show sensor resolution of a few nanoteslas.

  14. Biochemical component identification by plasmonic improved whispering gallery mode optical resonance based sensor

    NASA Astrophysics Data System (ADS)

    Saetchnikov, Vladimir A.; Tcherniavskaia, Elina A.; Saetchnikov, Anton V.; Schweiger, Gustav; Ostendorf, Andreas

    2014-05-01

    Experimental data on detection and identification of variety of biochemical agents, such as proteins, microelements, antibiotic of different generation etc. in both single and multi component solutions under varied in wide range concentration analyzed on the light scattering parameters of whispering gallery mode optical resonance based sensor are represented. Multiplexing on parameters and components has been realized using developed fluidic sensor cell with fixed in adhesive layer dielectric microspheres and data processing. Biochemical component identification has been performed by developed network analysis techniques. Developed approach is demonstrated to be applicable both for single agent and for multi component biochemical analysis. Novel technique based on optical resonance on microring structures, plasmon resonance and identification tools has been developed. To improve a sensitivity of microring structures microspheres fixed by adhesive had been treated previously by gold nanoparticle solution. Another technique used thin film gold layers deposited on the substrate below adhesive. Both biomolecule and nanoparticle injections caused considerable changes of optical resonance spectra. Plasmonic gold layers under optimized thickness also improve parameters of optical resonance spectra. Biochemical component identification has been also performed by developed network analysis techniques both for single and for multi component solution. So advantages of plasmon enhancing optical microcavity resonance with multiparameter identification tools is used for development of a new platform for ultra sensitive label-free biomedical sensor.

  15. Magnetic resonance imaging-compatible tactile sensing device based on a piezoelectric array.

    PubMed

    Hamed, Abbi; Masamune, Ken; Tse, Zion Tsz Ho; Lamperth, Michael; Dohi, Takeyoshi

    2012-07-01

    Minimally invasive surgery is a widely used medical technique, one of the drawbacks of which is the loss of direct sense of touch during the operation. Palpation is the use of fingertips to explore and make fast assessments of tissue morphology. Although technologies are developed to equip minimally invasive surgery tools with haptic feedback capabilities, the majority focus on tissue stiffness profiling and tool-tissue interaction force measurement. For greatly increased diagnostic capability, a magnetic resonance imaging-compatible tactile sensor design is proposed, which allows minimally invasive surgery to be performed under image guidance, combining the strong capability of magnetic resonance imaging soft tissue and intuitive palpation. The sensing unit is based on a piezoelectric sensor methodology, which conforms to the stringent mechanical and electrical design requirements imposed by the magnetic resonance environment The sensor mechanical design and the device integration to a 0.2 Tesla open magnetic resonance imaging scanner are described, together with the device's magnetic resonance compatibility testing. Its design limitations and potential future improvements are also discussed. A tactile sensing unit based on a piezoelectric sensor principle is proposed, which is designed for magnetic resonance imaging guided interventions. PMID:22913103

  16. Orbit-based analysis of resonant excitations of Alfvén waves in tokamaks

    SciTech Connect

    Bierwage, Andreas; Shinohara, Kouji

    2014-11-15

    The exponential growth phase of fast-ion-driven Alfvénic instabilities is simulated and the resonant wave-particle interactions are analyzed numerically. The simulations are carried out in realistic magnetic geometry and with a realistic particle distribution for a JT-60U plasma driven by negative-ion-based neutral beams. In order to deal with the large magnetic drifts of the fast ions, two new mapping methods are developed and applied. The first mapping yields the radii and pitch angles at the points, where the unperturbed orbit of a particle intersects the mid-plane. These canonical coordinates allow to express analysis results (e.g., drive profiles and resonance widths) in a form that is easy to understand and directly comparable to the radial mode structure. The second mapping yields the structure of the wave field along the particle trajectory. This allows us to unify resonance conditions for trapped and passing particles, determine which harmonics are driven, and which orders of the resonance are involved. This orbit-based resonance analysis (ORA) method is applied to fast-ion-driven instabilities with toroidal mode numbers n = 1-3. After determining the order and width of each resonance, the kinetic compression of resonant particles and the effect of linear resonance overlap are examined. On the basis of the ORA results, implications for the fully nonlinear regime, for the long-time evolution of the system in the presence of a fast ion source, and for the interpretation of experimental observations are discussed.

  17. Fluorescence resonance energy transfer-based stoichiometry in living cells.

    PubMed Central

    Hoppe, Adam; Christensen, Kenneth; Swanson, Joel A

    2002-01-01

    Imaging of fluorescence resonance energy transfer (FRET) between fluorescently labeled molecules can measure the timing and location of intermolecular interactions inside living cells. Present microscopic methods measure FRET in arbitrary units, and cannot discriminate FRET efficiency and the fractions of donor and acceptor in complex. Here we describe a stoichiometric method that uses three microscopic fluorescence images to measure FRET efficiency, the relative concentrations of donor and acceptor, and the fractions of donor and acceptor in complex in living cells. FRET stoichiometry derives from the concept that specific donor-acceptor complexes will give rise to a characteristic FRET efficiency, which, if measured, can allow stoichiometric discrimination of interacting components. A first equation determines FRET efficiency and the fraction of acceptor molecules in complex with donor. A second equation determines the fraction of donor molecules in complex by estimating the donor fluorescence lost due to energy transfer. This eliminates the need for acceptor photobleaching to determine total donor concentrations and allows for repeated measurements from the same cell. A third equation obtains the ratio of total acceptor to total donor molecules. The theory and method were confirmed by microscopic measurements of fluorescence from cyan fluorescent protein (CFP), citrine, and linked CFP-Citrine fusion protein, in solutions and inside cells. Together, the methods derived from these equations allow sensitive, rapid, and repeatable detection of donor-, acceptor-, and donor-acceptor complex stoichiometry at each pixel in an image. By accurately imaging molecular interactions, FRET stoichiometry opens new areas for quantitative study of intracellular molecular networks. PMID:12496132

  18. Nanophotonic graphene-based racetrack-resonator add/drop filter

    NASA Astrophysics Data System (ADS)

    Wirth L., A.; da Silva, M. G.; Neves, D. M. C.; Sombra, A. S. B.

    2016-05-01

    We are presenting and analyzing a graphene-based nanophotonic device to operate as a resonator-add/drop filter, whose control is obtained by varying the graphene chemical potential. That device consists of graphene-based waveguides, two directional couplers and a racetrack resonator with 90° bends. Since the graphene chemical potential provides the achievement of the necessary parameters, the resonance and filtering of the signals are obtained by applying the correct value of the graphene chemical potential in the graphene nanoribbons. The results of this study should help in the development of new graphene-based nanophotonic devices operating in the terahertz and infrared range (including in the C-band of the International Telecommunication Union - ITU), for use in future communications networks.

  19. Design and implementation of dual-band antennas based on a complementary split ring resonators

    NASA Astrophysics Data System (ADS)

    Ortiz, Noelia; Iriarte, Juan Carlos; Crespo, Gonzalo; Falcone, Francisco

    2015-07-01

    A simple dual-band antenna design and implementation method is proposed in this work, based on the equivalent media properties inspired by resonant metamaterial elements. The equivalent circuit model of dual-band patch antennas based on a complementary split ring resonator (CSRR) is presented and validated. The dual-band patch antenna is designed etching a CSRR in the patch of a conventional rectangular microstrip patch antenna. The first resonance is governed by the quasi-static resonance of the CSRR while the second resonance is originated by the rectangular patch. The fact of etching a CSRR on a rectangular patch antenna also produces a miniaturization of a conventional patch antenna. The equivalent circuit model proposed in this letter is sound in order to understand the functionality of dual-band patch antennas based on a CSRR. Good agreement between simulation, equivalent circuit model and experimental results is shown and discussed. These results lead the equivalent circuit model to become a simple and straightforward tool for the design of this type of multiband antennas, of low cost and versatile operation for a broad range of wireless communication systems.

  20. Dielectric Resonator-Based Side-Access Probe for Muscle Fiber EPR Study

    NASA Astrophysics Data System (ADS)

    Sienkiewicz, Andrzej; Jaworski, Marek; Smith, Brian G.; Fajer, Piotr G.; Scholes, Charles P.

    2000-03-01

    We present a novel dielectric resonator (DR)-based resonant structure that accommodates aqueous sample capillaries in orientations that are either parallel (i.e., side-access) or perpendicular to the direction of an external (Zeeman) magnetic field, B0. The resonant structure consists of two commercially available X-band DRs that are separated by a Rexolite spacer and resonate in the fundamental TE01δ mode. The separator between the DRs is used to tune the resonator to the desired frequency and, by appropriately drilled sample holes, to provide access for longitudinal samples, notably capillaries containing oriented, spin-labeled muscle fibers. In contrast to the topologically similar cylindrical TE011 cavity, the DR-based structure has distinct microwave properties that favor its use for parallel orientation of lossy aqueous samples. For perpendicular orientation of a dilute (6.25 μM) aqueous solution of IASL spin label, the S/N ratio was at least one order of magnitude better for the side-access DR-based structure than for a standard TE102 cavity. EPR spectra acquired for maleimide spin-labeled myosin filaments also revealed ca. 10 times better S/N ratio than those obtained with a standard TE102 cavity. For the side-access DR with sample capillaries oriented either parallel or perpendicular to the external magnetic field, the Q- and filling factors are in good agreement with the theoretical estimates derived from the distribution of magnetic (H1) and electric (E1) components.

  1. A super narrow band filter based on silicon 2D photonic crystal resonator and reflectors

    NASA Astrophysics Data System (ADS)

    Wang, Yuanyuan; Chen, Deyuan; Zhang, Gang; Wang, Juebin; Tao, Shangbin

    2016-03-01

    In this paper, a novel structure of super narrow band filter based on two-dimensional square lattice photonic crystals of silicon rods in air for 1.5 um communication is proposed and studied. COMSOL Multiphysics4.3b software is used to simulate the optical behavior of the filter. The filter consists of one point-defect-based resonator and two line-defect-based reflectors. The resonance frequency, transmission coefficient and quality factor are investigated by varying the parameters of the structure. In design, a silicon rod is removed to form the resonator; for the rows of rods above and below the resonator, a part of the rods are removed to form the reflectors. By optimizing the parameters of the filter, the quality factor and transmission coefficient of the filter at the resonance frequency of 2e14 Hz can reach 1330 and 0.953, respectively. The super narrow band filter can be integrated into optical circuit for its micron size. Also, it can be used for wavelength selection and noise filtering of optical amplifier in future communication application.

  2. Dual wavelength demultiplexer based on metal–insulator–metal plasmonic circular ring resonators

    NASA Astrophysics Data System (ADS)

    Rakhshani, Mohammad Reza; Mansouri-Birjandi, Mohammad Ali

    2016-06-01

    In this paper, we investigated a plasmonic demultiplexer structure based on Metal-Insulator-Metal (MIM) waveguides and circular ring resonators. In order to achieve the structure of demultiplexer, two improved ring resonators have been used, which input and outputs MIM waveguides coupled by the ring resonators. To improve the transmission efficiency, a reflector was introduced at the right end of the input and output waveguides. By substituting the ring core with dielectric, the possibility of tuning the resonance wavelength of the proposed structure is illustrated, and the effect of various parameters such as radius and refractive index in transmission efficiency is studied in detail. This is useful for the design of integrated circuits in which it is not possible to extend the dimension of the ring resonator to attain a longer resonance wavelength. Transmission efficiency and quality factor of the single ring are 84% and 110, respectively. The simulation results using finite difference time domain method shows that in the proposed demultiplexer, which is composed of two rings with different core refractive indexes, the average power efficiency, bandwidth for each output channel, and the mean value of crosstalk are estimated 80%, 17 nm, and -26.95 dB, respectively. It is revealed that the significant features of the device are high transmission efficiency, low crosstalk, high-quality factor, and tunability for desired wavelengths. Therefore, the proposed structure has the potential to be applied in plasmonic integrated circuits.

  3. Experimental study of intense radiation in terahertz region based on cylindrical surface wave resonator

    SciTech Connect

    Gong, Shaoyan; Ogura, Kazuo; Yambe, Kiyoyuki; Nomizu, Shintaro; Shirai, Akihiro; Yamazaki, Kosuke; Kawamura, Jun; Miura, Takuro; Takanashi, Sho; San, Min Thu

    2015-09-28

    Periodical corrugations structured on a cylindrical conductor have cylindrical surface waves (CSWs), which are reflected at the corrugation ends and form a CSW-resonator. In this paper, intense radiations in terahertz region based on the CSW-resonator are reported. The CSW-resonators with upper cut off frequencies in the modern IEEE G-band (110–300 GHz) are excited by a coaxially injected annular beam in a weakly relativistic region less than 100 kV. It is shown that there exists an oscillation starting energy for the CSW-resonator. Above the starting energy, very intense terahertz radiations on the order of kW are obtained. The operation frequencies in the range of 166–173 GHz and 182–200 GHz are obtained using two types of CSW-resonator with the different corrugation amplitude. Electromagnetic properties of the CSW-resonator can be controlled by the artificial structure and may play an important role in high-intensity terahertz generations and applications.

  4. CORDIC algorithm based digital detection technique applied in resonator fiber optic gyroscope

    NASA Astrophysics Data System (ADS)

    Yang, Zhihuai; Jin, Xiaojun; Ma, Huilian; Jin, Zhonghe

    2009-06-01

    A digital detection technique based on the coordinate rotation digital computer (CORDIC) algorithm is proposed for a resonator fiber optic gyroscope (R-FOG). It makes the generation of modulation signal, synchronous demodulation and signal processing in R-FOG to be realized in a single field programmable gate array (FPGA). The frequency synthesis and synchronous detection techniques based on the CORDIC algorithm have been analyzed and designed firstly. The experimental results indicate that the precision of the detection circuit satisfies the requirements for the closed-loop feedback in R-FOG system. The frequency of the laser is locked to the resonance frequency of the fiber ring resonator stably and the open-loop gyro output signal is observed successfully. The dynamic range and the bias drift of the R-FOG are ±1.91 rad/s and 0.005 rad/s over 10 s, respectively.

  5. Atomic-resolution single-spin magnetic resonance detection concept based on tunneling force microscopy

    NASA Astrophysics Data System (ADS)

    Payne, A.; Ambal, K.; Boehme, C.; Williams, C. C.

    2015-05-01

    A study of a force detected single-spin magnetic resonance measurement concept with atomic spatial resolution is presented. The method is based upon electrostatic force detection of spin-selection rule controlled single-electron tunneling between two electrically isolated paramagnetic states. Single-spin magnetic resonance detection is possible by measuring the force detected tunneling charge noise on and off spin resonance. Simulation results of this charge noise, based upon physical models of the tunneling and spin physics, are directly compared to measured atomic force microscopy system noise. The results show that the approach could provide single-spin measurement of electrically isolated qubit states with atomic spatial resolution at room temperature.

  6. Disposable electrochemical immunosensor by using carbon sphere/gold nanoparticle composites as labels for signal amplification.

    PubMed

    Xu, Qiunan; Yan, Feng; Lei, Jianping; Leng, Chuan; Ju, Huangxian

    2012-04-16

    This work designed a simple, sensitive, and low-cost immunosensor for the detection of protein marker by using a carbon sphere/gold nanoparticle (CNS/AuNP) composite as an electrochemical label. The nanoscale carbon spheres, prepared with a hydrothermal method by using glucose as raw material, were used to load AuNPs for labeling antibody by electrostatic interaction, which provided a feasible pathway for electron transfer due to the remarkable conductivity. The disposable immunosensor was constructed by coating a polyethylene glycol (PEG) film on a screen-printed carbon-working electrode and then immobilizing capture antibody on the film. With a sandwich-type immunoassay format, the analyte and then the CNS/AuNP-labeled antibody were successively bound to the immunosensor. The bound AuNPs were finally electro-oxidized in 0.1  M HCl to produce AuCl(4)(-) for differential pulse voltammetric (DPV) detection. The high-loading capability of AuNPs on CNS for the sandwich-type immunorecognition led to obvious signal amplification. By using human immunoglobulin G (IgG) as model target, the DPV signal of AuNPs after electro-oxidized at optimal potential of +1.40 V for 40 s showed a wide linear dependence on the logarithm of target concentration ranging from 10 pg  mL(-1) to 10 ng  mL(-1). The detection limit was around 9 pg  mL(-1). The immunosensor showed excellent analytical performance with cost effectivity, good fabrication reproducibility, and acceptable precision and accuracy, providing significant potential application in clinical analysis. PMID:22438025

  7. Fabrication of plasmon length-based surface enhanced Raman scattering for multiplex detection on microfluidic device.

    PubMed

    Nguyen, Anh H; Lee, Jeewon; Il Choi, Hong; Seok Kwak, Ho; Jun Sim, Sang

    2015-08-15

    The length of bioreceptors plays an important role in signal enhancement of surface-enhanced Raman scattering (SERS) due to amplification of electromagnetic fields generated by the excitation of localized surface plasmons. Herein, intact antibodies (IgG) and Fab fragments conjugated onto gold nanostar were used to fabricate two kinds of immunosensors for measurement of their SERS signals. Using CA125 as the antigen and Rhodamine-6G (R6G)-conjugated immunogolds, a SERS immunosensor was self-assembled by antigen-antibody interaction. The results showed that the SERS signal from the Fab immunosensor was 2.4 times higher than that of the IgG immunosensor. Furthermore, increased hot-spots by silver atom deposition onto the IgG and Fab immunosensor showed 2.1 and 1.4 times higher signals than before enhancement, respectively. For application, based on the Fab immunosensor, a SERS-compatible microfluidic system was designed for multiplex assays to overcome the drawbacks of conventional assays. This system can measure biological specimens directly from bio fluids instead of using a complex microfluidic device containing separation and detection elements. Four approved biomarkers of breast cancer, including cancer antigen (CA125), HER2, epididymis protein (HE4), and Eotaxin-1, were detected from patient-mimicked serum with limits of 15 fM, 17 fM, 21 fM, and 6.5 fM, respectively. The results indicated that the lengths and geometry of the bioreceptors determined the intensity of SERS signal from the interface and cavity of the sandwich immunosensor. Silver atom deposition at the cavity of the immunosensor increased the SERS signal. Finally, the SERS immunosensor built-in microfluidic system improved the performance of multiplex diagnostics. PMID:25841120

  8. Laterally vibrating resonator based elasto-optic modulation in aluminum nitride

    NASA Astrophysics Data System (ADS)

    Ghosh, Siddhartha; Piazza, Gianluca

    2016-06-01

    An integrated strain-based optical modulator driven by a piezoelectric laterally vibrating resonator is demonstrated. The composite structure consists of an acoustic Lamb wave resonator, in which a photonic racetrack resonator is internally embedded to enable overlap of the guided optical mode with the induced strain field. Both types of resonators are defined in an aluminum nitride (AlN) thin film, which rests upon a layer of silicon dioxide in order to simultaneously define optical waveguides, and the structure is released from a silicon substrate. Lateral vibrations produced by the acoustic resonator are transferred through a partially etched layer of AlN, producing a change in the effective index of the guided wave through the interaction of the strain components with the AlN elasto-optic (p) coefficients. Optical modulation through the elasto-optic effect is demonstrated at electromechanically actuated frequencies of 173 MHz and 843 MHz. This device geometry further enables the development of MEMS-based optical modulators in addition to studying elasto-optic interactions in suspended piezoelectric thin films.

  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. 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

  11. Ionic liquid functionalized graphene/Au nanocomposites and its application for electrochemical immunosensor.

    PubMed

    Liu, Na; Chen, Xia; Ma, Zhanfang

    2013-10-15

    In this work, a new nanocomposite, which was composed of ionic liquid functionalized graphene sheet (IL-GS) loaded gold nanoparticles (AuNPs), was prepared. The IL-GS was directly synthesized by the electrochemical exfoliation of graphite in ionic liquid (IL). Due to the modification of the IL, IL-GS can not only be dispersed easily in aqueous solution to form a homogeneous colloidal suspension of individual sheet, but also exhibits an improved conductivity. Meanwhile, the loaded AuNPs on the nanocomposites can increase the specific surface area to capture a large amount of antibodies as well as improve the capability of electron transfer. The IL-GS-Au nanocomposites were successfully employed for the fabrication of a facile and sensitive electrochemical immunosensor. Carcinoembryonic antigen (CEA) was used as a model protein. The proposed immunosensor exhibits a wide linear detection range (LDR) from 1 fg mL⁻¹ to 100 ng mL⁻¹, and an ultralow limit of detection (LOD) of 0.1 fg mL⁻¹ (S/N=3). In addition, for the detection of clinical serum samples, it is well consistent with the data determined by the developed immunoassay and ELISA, indicating that the immunosensor provides a possible application for the detection of CEA in clinical diagnostics. PMID:23644143

  12. Electrochemical detection of fluoroquinolone antibiotics in milk using a magneto immunosensor.

    PubMed

    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

  13. Explosives detection in the marine environment using UUV-modified immunosensor

    NASA Astrophysics Data System (ADS)

    Charles, Paul T.; Adams, André A.; Deschamps, Jeffrey R.; Veitch, Scott P.; Hanson, Alfred; Kusterbeck, Anne W.

    2011-05-01

    Port and harbor security has rapidly become a point of interest and concern with the emergence of new improvised explosive devices (IEDs). The ability to provide physical surveillance and identification of IEDs and unexploded ordnances (UXO) at these entry points has led to an increased effort in the development of unmanned underwater vehicles (UUVs) equipped with sensing devices. Traditional sensors used to identify and locate potential threats are side scan sonar/acoustic methods and magnetometers. At the Naval Research Laboratory (NRL), we have developed an immunosensor capable of detecting trace levels of explosives that has been integrated into a REMUS payload for use in the marine environment. Laboratory tests using a modified PMMA microfluidic device with immobilized monoclonal antibodies specific for TNT and RDX have been conducted yielding detection levels in the low parts-per-billion (ppb) range. New designs and engineered improvements in microfluidic devices, fluorescence signal probes, and UUV internal fluidic and optical components have been investigated and integrated into the unmanned underwater prototype. Results from laboratory and recent field demonstrations using the prototype UUV immunosensor will be discussed. The immunosensor in combination with acoustic and other sensors could serve as a complementary characterization tool for the detection of IEDs, UXOs and other potential chemical or biological threats.

  14. A label-free impedimetric immunosensor for direct determination of the textile dye Disperse Orange 1.

    PubMed

    Yang, Jing; da Rocha, Carolina Gomes; Wang, Shengfu; Ferreira, Antonio Aparecido Pupim; Yamanaka, Hideko

    2015-09-01

    A strategy for a label-free impedimetric immunosensor is described for detection of the textile dye Disperse Orange 1 (DO1). The compounds 1,12-diaminododecane (DADD) and then 1,7-diaminoheptane (DAH) were firstly successively grafted onto a glassy carbon electrode (GCE) surface by electro-oxidation of one amino group, while the other terminal amino group was modified with the antibody anti-DO1. The construction process of the immunosensor was characterized by cyclic voltammetry, electrochemical impedance spectroscopy and capacitance measurements. The electron transfer resistance (Rct) exhibited an effective response to the affinity between the immobilized antibody and the antigen in solution. The linear range for the target compound was from 5.0 nmol L(-1) to 0.5 μmol L(-1) (R=0.9980), and the limit of detection (LOD) was 7.56 nmol L(-1). The proposed impedimetric immunosensor has the advantages of simplicity, cost-effectiveness, and sensitivity. PMID:26003710

  15. Prototype explosives detection system based on nuclear resonance absorption in nitrogen

    SciTech Connect

    Morgado, R.E.; Arnone, G.; Cappiello, C.C.; Gardner, S.D.; Hollas, C.L.; Ussery, L.E.; White, J.M.; Zahrt, J.D.; Krauss, R.A.

    1993-12-01

    A-prototype explosives detection system that was developed for experimental evaluation of a nuclear resonance absorption techniques is described. The major subsystems are a proton accelerator and beam transport, high-temperature proton target, an airline-luggage tomographic inspection station, and an image-processing/detection- alarm subsystem. The detection system performance, based on a limited experimental test, is reported.

  16. Prototype explosives-detection system based on nuclear-resonance absorption in nitrogen

    SciTech Connect

    Morgado, R.E.; Arnone, G.; Cappiello, C.C.; Gardner, S.D.; Hollas, C.L.; Ussery, L.E.; White, J.M.; Zahrt, J.D.; Krauss, R.A.

    1994-06-01

    A prototype explosives-detection system (EDS) that was developed for experimental evaluation of a nuclear-resonance absorption technique is described. The major subsystems are a proton accelerator and beam transport, high-temperature proton target, an airline-luggage tomographic inspection station, and an image-processing/detection-alarm subsystem. The detection system performance, based on a limited experimental test, is reported.

  17. Long wave infrared tunable filter based on guided mode resonant effect

    NASA Astrophysics Data System (ADS)

    Mirotznik, Mark S.; Gupta, Neelam; McElhiney, Morgan; Carey, Victoria

    2016-05-01

    We describe here a tunable long wave infrared (LWIR) band filter based on the guided mode resonant filter (GMRF) effect. The device consists of a subwavelength dielectric grating sandwiched between planar layers of contrasting dielectric materials. Using a rigorous electromagnetic design and analysis method we demonstrate how a strong narrow band reflectance can be induced. Moreover, the resonant wavelength can be easily tuned over the entire 8-12 micron band by mechanically tilting the device with respect to the optical axis. Simulation and experimental results are presented demonstrating the effectiveness of the device.

  18. Cyclotron resonance in HgTe/CdTe-based heterostructures in high magnetic fields.

    PubMed

    Zholudev, Maxim S; Ikonnikov, Anton V; Teppe, Frederic; Orlita, Milan; Maremyanin, Kirill V; Spirin, Kirill E; Gavrilenko, Vladimir I; Knap, Wojciech; Dvoretskiy, Sergey A; Mihailov, Nikolay N

    2012-01-01

    : Cyclotron resonance study of HgTe/CdTe-based quantum wells with both inverted and normal band structures in quantizing magnetic fields was performed. In semimetallic HgTe quantum wells with inverted band structure, a hole cyclotron resonance line was observed for the first time. In the samples with normal band structure, interband transitions were observed with wide line width due to quantum well width fluctuations. In all samples, impurity-related magnetoabsorption lines were revealed. The obtained results were interpreted within the Kane 8·8 model, the valence band offset of CdTe and HgTe, and the Kane parameter EP being adjusted. PMID:23013642

  19. Periodic large-area metallic split-ring resonator metamaterial fabrication based on shadow nanosphere lithography.

    PubMed

    Gwinner, Michael Christian; Koroknay, Elisabeth; Fu, Liwei; Patoka, Piotr; Kandulski, Witold; Giersig, Michael; Giessen, Harald

    2009-03-01

    A fast and cheap, large-area (>1 cm(2)), high-coverage fabrication technique for periodic metallic split-ring resonator metamaterials is presented, which allows control of inner- and outer-ring diameters, gap angles, as well as thickness and periodicity. This method, based on shadow nanosphere lithography, uses tilted-angle-rotation thermal evaporation onto Langmuir-Blodgett-type monolayers of close-packed polystyrene nanospheres. Excellent agreement of the process parameters with a simplified model is demonstrated. Pronounced, tunable optical metamaterial resonances in the range of 100 THz are consistent with simulations. PMID:19148886

  20. A magneto-optical isolator based on series-coupled race-track resonators

    NASA Astrophysics Data System (ADS)

    Qi, Wei; Jin, Yichang; Yu, Hui; Jiang, Xiaoqing

    2015-01-01

    In this paper, we propose a novel kind of magneto-optical (MO) isolators based on series-coupled race-track resonators. The perturbation theory is used to calculate the non-reciprocal phase shift (NRPS) induced by the MO effect. The numerical result indicates that the isolation is greatly enhanced by the box-like spectra of series-coupled resonators. Optical isolation ratio for the first, second, and third order devices are 7.8, 21, and 36.2 dB, respectively.