1,720,966 research outputs found
Prussian Blue Nanoparticles as labels in a Sandwich-type Nanostructured Immunosensor to detect Immunoglobulin G
No full textThe need for small, portable, accurate, and simple-to-use analytical devices for biomedical applications has drawn the scientific community attention to electrochemical biosensors. In this work, a sandwich-type electrochemical immunosensor based on Gold Nanowires (GNWs) was developed for Human Immunoglobulin G (H-IgG) detection. H-IgG was selected as model analyte because of its physical, chemical, and biological features similar to many other protein biomarkers. The sensor substrate was a GNW electrode. GNWs were obtained through electrochemical template deposition into a nanoporous polycarbonate membrane. To achieve the best morphology, various deposition conditions were analyzed such as the time of deposition, and Au salt concentration in the deposition bath solution. The best deposition conditions that ensure the formation of mechanically stable nanowires were selected. Prussian blue (PB) is a transition metal hexacyanometalate with the formula of Fe4III[FeII(CN)6]3. This compost drew a lot of attention because Prussian White, a reduced form of PB, can catalyze the electrochemical reduction of hydrogen peroxide. For this reason, PB Nanoparticles (PBNPs) were fabricated to serve as secondary antibody catalytic label. Figure 1b shows the PBNPs with a typical cubic shape. A sandwich-type immunosensor consists of a primary antibody covalently attached to the electrode surface, the antigen (H-IgG) selectively bound by the primary antibody, and a secondary PBNP-labelled antibody. The fabrication process requires several incubation steps, which are summarized in Figure 2. Since PBNPs act as catalysts for H2O2 reduction, chronoamperometry in an H2O2 probe solution can detect H-IgG. This is due to the fact that the amount of PB catalyst on the electrode increases with analyte concentration. Therefore, the electrode was used to measure H2O2 reduction current density, which is indirectly related to the concentration of H-IgG. In this way, the calibration curve was constructed obtaining a linear range of 1-1000 ng mL-1 and high sensitivity
Electrochemical detection of H2O2 by means of gold foam-based electrode
Get PDFIn this work, a low-cost electrochemical sensor was developed for the detection of hydrogen peroxide. Hydrogen peroxide is the most used biomarker in monitoring oxidative stress due to its stability and ability to diffuse across the cell membrane. Oxidative stress occurs when the concentration of reactive oxygen species (ROS) in biological fluids increases with respect to the physiological concentration; this condition is a risk factor for many diseases. Among ROS, hydrogen peroxide is the more stable and thus it can be used as a biomarker. Since oxidative stress is not associated with specific symptoms, it is important to monitor the concentration of hydrogen peroxide to prevent the onset of serious diseases or to slow down their progression. In this field, research aims to develop electrochemical sensors for hydrogen peroxide quantification as an alternative to time-consuming and expensive traditional techniques.
The proposed sensor was obtained using the common substrate of the printed circuit board (PCB) fabrication. A design consisting of three electrodes of copper was optimized to obtain a complete cell. The working electrode was modified by electrodeposition to obtain a gold foam. Before gold foam deposition, the copper surface was covered with a thin planar film of gold using sputtering. The foam was electrodeposited by potenziostatic deposition at - 2 V using a water solution containing gold precursor and sulfuric acid. The detection of hydrogen peroxide was carried out with a conventional three-electrode system using a homemade cell obtained by 3D printing. Electrochemical tests were carried out in phosphate buffer as blank and by chronoamperometry at – 0.1 V. To build the calibration line, different concentrations of hydrogen peroxide, ranging from 25 to 1000 μM, were tested. The obtained results showed that the current density was proportional to the concentration of hydrogen peroxide, so the sensor can quantify this analyte. Further study will be addressed to characterize the device in terms of selectivity, stability and reproducibility
Electrochemical detection of human immunoglobulin-G using immunosensor based on ZnO nanorods
No full textNanostructured Electrochemical Immunosensor based on Gold Nanowires for the Detection of Model Protein
No full textNowadays the demand for new devices capable of accurate, fast, and in situ real-time analyses is growing rapidly in the medical field. These devices could have various applications, such as clinical diagnosis and remote patient monitoring. In this work, an electrochemical immunosensor based on Gold Nanowire (GNWs) was developed for the detection of a model protein. Human immunoglobulin G (H-IgG) was selected as model analyte because of its physical, chemical, and biological features like many other biomarkers.
GNWs were obtained through electrochemical template deposition into nanoporous polycarbonate membrane. To achieve the best morphology, various deposition conditions have been analyzed such as deposition time and Au precursor concentration in the deposition bath. The best deposition conditions were selected, ensuring the formation of mechanically stable nanowires.
To detect proteins, a sandwich configuration was assembled on the surface of the electrode through several incubation steps. The sandwich configuration consists of a) a primary antibody covalently attached on the electrode surface, b) the antigen to be detected (H-IgG) that is selectively bound by the primary antibody, and c) a secondary labelled antibody. The immunosensor is electrochemically active thanks to the presence of gold nanoparticles (GNPs) tagging the secondary antibody. Given that GNPs catalyze hydrogen evolution reaction, the electrode has been used to measure the current density of the hydrogen evolution, which is indirectly related to the concentration of H-IgG antigens. In this way the calibration curve was constructed obtaining linear range of 1-1000 ng mL-1 with a high sensitivity
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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