1,721,055 research outputs found
The role of peptides in the design of electrochemical biosensors for clinical diagnostics
Full text linkPeptides represent a promising class of biorecognition elements that can be coupled to electrochemical transducers. The benefits lie mainly in their stability and selectivity toward a target analyte. Furthermore, they can be synthesized rather easily and modified with specific functional groups, thus making them suitable for the development of novel architectures for biosensing platforms, as well as alternative labelling tools. Peptides have also been proposed as antibiofouling agents. Indeed, biofouling caused by the accumulation of biomolecules on electrode surfaces is one of the major issues and challenges to be addressed in the practical application of electrochemical biosensors. In this review, we summarise trends from the last three years in the design and development of electrochemical biosensors using synthetic peptides. The different roles of peptides in the design of electrochemical biosensors are described. The main procedures of selection and synthesis are discussed. Selected applications in clinical diagnostics are also described
Aligned carbon nanotube thin films for DNA electrochemical sensing
No full textCarbon nanotubes are interesting materials for DNA electrochemical sensing due to their unique electric
properties: high surface area, fast heterogeneous electron transfer, and electrochemical stability. In this
work aligned Carbon NanoTube (CNT) thin films were designed and tested as candidate platforms for
DNA immobilization and for the development of an electrochemical genosensor.
The filmswere prepared by Chemical Vapor Deposition (CVD) using acetylene and ammonia as precursor
gases and nickel particles as catalyst. A preliminary electrochemical characterization was performed
using cyclic voltammetry since, so far, these films have been used only for gas sensing. The surfaces were
then covalently functionalized with a DNA oligonucleotide probe, complementary to the sequence of
the most common inserts in the GMOs: the Promoter 35S. The genosensor format involved the immobilization
of the probe onto the sensor surface, the hybridization with the target-sequence and the
electrochemical detection of the duplex formation. Careful attention was paid to the probe immobilization
conditions in order to minimize the signal due to non-specifically adsorbed sequences. For the
detection of the hybridization event both label-free and enzyme-labelled methods were investigated. In
case of the enzyme-labelled method a target concentration at nanomolar level can be easily detected,
with a linear response from 50nM to 200 nM, whereas the label-free method showed a linear response
between 0.5Mand 10M. The reproducibility was 11% and 20% with the enzyme-labelledmethod and
the label-free method, respectively. The batch-to-batch reproducibility of the different sensors was also
evaluated
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Electrochemical bioassay for the detection of TNF-a using magnetic beads and disposable screen-printed array of electrodes
No full textIn this study we have developed an electrochemical bioassay for the analysis of TNF-a, coupling magnetic beads with disposable electrochemical platforms. TNF-a is a pro inflammatory cytokine that participates in the regulation of immune defense against various pathogens and the recovery from injury. It plays a central role in the development of many inflammatroy diseases. The bioassay was based on a sandwich format using alkaline phosphatase as an enzymatic label and an eight -sensor screen-printed array as an electrochmical transducer.Bettazzi, F.; Enayati, L.; Campos Sánchez, I.; Motaghed, R.; Mascini, M.; Palchetti, I. (2013). Electrochemical bioassay for the detection of TNF-a using magnetic beads and disposable screen-printed array of electrodes. Bioanalysis. 5(1):11-19. doi:10.4155/BIO.12.293S111951Wang, J., Liu, G., Engelhard, M. H., & Lin, Y. (2006). Sensitive Immunoassay of a Biomarker Tumor Necrosis Factor-α Based on Poly(guanine)-Functionalized Silica Nanoparticle Label. Analytical Chemistry, 78(19), 6974-6979. doi:10.1021/ac060809fYuan, L., Hua, X., Wu, Y., Pan, X., & Liu, S. (2011). Polymer-Functionalized Silica Nanosphere Labels for Ultrasensitive Detection of Tumor Necrosis Factor-alpha. Analytical Chemistry, 83(17), 6800-6809. doi:10.1021/ac201558wDe Kossodo, S., Houba, V., & Grau, G. . (1995). Assaying tumor necrosis factor concentrations in human serum a WHO International Collaborative Study. Journal of Immunological Methods, 182(1), 107-114. doi:10.1016/0022-1759(95)00028-9Palladino, M. A., Bahjat, F. R., Theodorakis, E. A., & Moldawer, L. L. (2003). Anti-TNF-α therapies: the next generation. Nature Reviews Drug Discovery, 2(9), 736-746. doi:10.1038/nrd1175Corti, A., Poiesi, C., Merli, S., & Cassani, G. (1994). Tumor Necrosis Factor (TNF) α quantification by ELISA and bioassay: effects of TNFα-soluble TNF receptor (p55) complex dissociation during assay incubations. Journal of Immunological Methods, 177(1-2), 191-198. doi:10.1016/0022-1759(94)90156-2Bosnjakovic, A., Mishra, M. K., Han, H. J., Romero, R., & Kannan, R. M. (2012). A dendrimer-based immunosensor for improved capture and detection of tumor necrosis factor-α cytokine. Analytica Chimica Acta, 720, 118-125. doi:10.1016/j.aca.2012.01.017Laing, S., Hernandez-Santana, A., Sassmannshausen, J., Asquith, D. L., McInnes, I. B., Faulds, K., & Graham, D. (2011). Quantitative Detection of Human Tumor Necrosis Factor α by a Resonance Raman Enzyme-Linked Immunosorbent Assay. Analytical Chemistry, 83(1), 297-302. doi:10.1021/ac1024039Renberg, B., Nordin, J., Merca, A., Uhlén, M., Feldwisch, J., Nygren, P.-Å., & Eriksson Karlström, A. (2007). Affibody Molecules in Protein Capture Microarrays: Evaluation of Multidomain Ligands and Different Detection Formats. Journal of Proteome Research, 6(1), 171-179. doi:10.1021/pr060316rHerrmann, M., Veres, T., & Tabrizian, M. (2008). Quantification of Low-Picomolar Concentrations of TNF-α in Serum Using the Dual-Network Microfluidic ELISA Platform. Analytical Chemistry, 80(13), 5160-5167. doi:10.1021/ac800427zHurst, G. B., Buchanan, M. V., Foote, L. J., & Kennel, S. J. (1999). Analysis for TNF-α Using Solid-Phase Affinity Capture with Radiolabel and MALDI-MS Detection. Analytical Chemistry, 71(20), 4727-4733. doi:10.1021/ac9905423Luo, L., Zhang, Z., & Ma, L. (2005). Determination of recombinant human tumor necrosis factor-α in serum by chemiluminescence imaging. Analytica Chimica Acta, 539(1-2), 277-282. doi:10.1016/j.aca.2005.02.046Law, W.-C., Yong, K.-T., Baev, A., & Prasad, P. N. (2011). Sensitivity Improved Surface Plasmon Resonance Biosensor for Cancer Biomarker Detection Based on Plasmonic Enhancement. ACS Nano, 5(6), 4858-4864. doi:10.1021/nn2009485Battaglia, T. M., Masson, J.-F., Sierks, M. R., Beaudoin, S. P., Rogers, J., Foster, K. N., … Booksh, K. S. (2005). Quantification of Cytokines Involved in Wound Healing Using Surface Plasmon Resonance. Analytical Chemistry, 77(21), 7016-7023. doi:10.1021/ac050568wYin, Z., Liu, Y., Jiang, L.-P., & Zhu, J.-J. (2011). Electrochemical immunosensor of tumor necrosis factor α based on alkaline phosphatase functionalized nanospheres. Biosensors and Bioelectronics, 26(5), 1890-1894. doi:10.1016/j.bios.2010.03.025Kerman, K., Saito, M., Morita, Y., Takamura, Y., Ozsoz, M., & Tamiya, E. (2004). Electrochemical Coding of Single-Nucleotide Polymorphisms By Monobase-Modified Gold Nanoparticles. Analytical Chemistry, 76(7), 1877-1884. doi:10.1021/ac0351872Shelbourne, M., Chen, X., Brown, T., & El-Sagheer, A. H. (2011). Fast copper-free click DNA ligation by the ring-strain promoted alkyne-azide cycloaddition reaction. Chemical Communications, 47(22), 6257. doi:10.1039/c1cc10743gCenti, S., Laschi, S., Fránek, M., & Mascini, M. (2005). A disposable immunomagnetic electrochemical sensor based on functionalised magnetic beads and carbon-based screen-printed electrodes (SPCEs) for the detection of polychlorinated biphenyls (PCBs). Analytica Chimica Acta, 538(1-2), 205-212. doi:10.1016/j.aca.2005.01.073Conzuelo, F., Gamella, M., Campuzano, S., Reviejo, A. J., & Pingarrón, J. M. (2012). Disposable amperometric magneto-immunosensor for direct detection of tetracyclines antibiotics residues in milk. Analytica Chimica Acta, 737, 29-36. doi:10.1016/j.aca.2012.05.051Laschi, S., Miranda-Castro, R., González-Fernández, E., Palchetti, I., Reymond, F., Rossier, J. S., & Marrazza, G. (2010). A new gravity-driven microfluidic-based electrochemical assay coupled to magnetic beads for nucleic acid detection. ELECTROPHORESIS, 31(22), 3727-3736. doi:10.1002/elps.201000288Laschi, S., Palchetti, I., Marrazza, G., & Mascini, M. (2006). Development of disposable low density screen-printed electrode arrays for simultaneous electrochemical measurements of the hybridisation reaction. Journal of Electroanalytical Chemistry, 593(1-2), 211-218. doi:10.1016/j.jelechem.2006.04.015Centi, S., Stoica, A. I., Laschi, S., & Mascini, M. (2010). Development of an Electrochemical Immunoassay Based on the Use of an Eight-Electrodes Screen-Printed Array Coupled with Magnetic Beads for the Detection of Antimicrobial Sulfonamides in Honey. Electroanalysis, 22(16), 1881-1888. doi:10.1002/elan.200900618BERTI, F., LASCHI, S., PALCHETTI, I., ROSSIER, J., REYMOND, F., MASCINI, M., & MARRAZZA, G. (2009). Microfluidic-based electrochemical genosensor coupled to magnetic beads for hybridization detection. Talanta, 77(3), 971-978. doi:10.1016/j.talanta.2008.07.064Centi, S., Silva, E., Laschi, S., Palchetti, I., & Mascini, M. (2007). Polychlorinated biphenyls (PCBs) detection in milk samples by an electrochemical magneto-immunosensor (EMI) coupled to solid-phase extraction (SPE) and disposable low-density arrays. Analytica Chimica Acta, 594(1), 9-16. doi:10.1016/j.aca.2007.04.064Centi, S., Messina, G., Tombelli, S., Palchetti, I., & Mascini, M. (2008). Different approaches for the detection of thrombin by an electrochemical aptamer-based assay coupled to magnetic beads. Biosensors and Bioelectronics, 23(11), 1602-1609. doi:10.1016/j.bios.2008.01.020PALECEK, E., & FOJTA, M. (2007). Magnetic beads as versatile tools for electrochemical DNA and protein biosensing. Talanta, 74(3), 276-290. doi:10.1016/j.talanta.2007.08.020Cai, F., Li, C.-R., Wu, J.-L., Chen, J.-G., Liu, C., Min, Q., … Chen, J.-H. (2006). Theaflavin Ameliorates Cerebral Ischemia-Reperfusion Injury in Rats Through Its Anti-Inflammatory Effect and Modulation of STAT-1. Mediators of Inflammation, 2006, 1-9. doi:10.1155/mi/2006/30490Pantsulaia, I., Trofimov, S., Kobyliansky, E., & Livshits, G. (2002). GENETIC AND ENVIRONMENTAL INFLUENCES ON IL-6 AND TNF-α PLASMA LEVELS IN APPARENTLY HEALTHY GENERAL POPULATION. Cytokine, 19(3), 138-146. doi:10.1006/cyto.2002.1959Centi, S., Bonel Sanmartin, L., Tombelli, S., Palchetti, I., & Mascini, M. (2009). Detection of C Reactive Protein (CRP) in Serum by an Electrochemical Aptamer-Based Sandwich Assay. Electroanalysis, 21(11), 1309-1315. doi:10.1002/elan.20080456
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Practical tips and new trends in electrochemical biosensing of cancer-related extracellular vesicles
No full textTo tackle cancer and provide prompt diagnoses and prognoses, the constantly evolving biosensing field is continuously on the lookout for novel markers that can be non-invasively analysed. Extracellular vesicles (EVs) may represent a promising biomarker that also works as a source of biomarkers. The augmented cellular activity of cancerous cells leads to the production of higher numbers of EVs, which can give direct information on the disease due to the presence of general and cancer-specific surface-tethered molecules. Moreover, the intravesicular space is enriched with other molecules that can considerably help in the early detection of neoplasia. Even though EV-targeted research has indubitably received broad attention lately, there still is a wide lack of practical and effective quantitative procedures due to difficulties in pre-analytical and analytical phases. This review aims at providing an exhaustive outline of the recent progress in EV detection using electrochemical and photoelectrochemical biosensors, with a focus on handling approaches and trends in the selection of bioreceptors and molecular targets related to EVs that might guide researchers that are approaching such an unstandardised field
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