1,354,079 research outputs found
Layer-By-Layer Biofunctionalization As a Novel Route for High-Sensitivity and High-Specificity Label-Free Affinity Biosensing with Nanostructured Materials
No full textNanostructured materials hold the promise to revolutionize the label-free biosensing of analytes at concentrations down to those required for clinical applications, beyond what microstructured materials did so far, by leveraging the deeper interaction between materials and analytes with comparable size. On the other hand, when the characteristic dimension of the materials gets down to the nanoscale, the biofunctionalization chemistry commonly used to promote the binding of bioreceptors and enable, in turn, the specific detection of target analytes becomes less effective.
Here, we propose an effective and robust route for the surface biofunctionalization of nanostructured materials based on the layer-by-layer electrostatic nano-assembling of oppositely-charged polyelectrolytes, which were engineered with bioreceptors covalently linked to the polymer chain. LbL biofunctionalization allows stability, density, and distribution of bioreceptors available on the transducer surface to be carefully controlled, thus solving most of the drawbacks of the common biofunctionalization chemistry on nanostructured materials.
The proof-of-concept demonstration of advantages of LbL biofunctionalization is given on nanostuctured porous silicon (PSi) interferometers, which are biofunctionalized for the affinity detection of streptavidin in raw saliva via LbL nano-assembling of a positively-charged poly(allylamine hydrochloride) (PAH) with a negatively-charged biotinylated poly(methacrylic acid) (b-PMAA). LbL-biofunctionalizion of PSi interferometers results to be very effective and highly robust, enabling high-sensitivity and high-specificity detection of streptavidin with a detection limit of 600 fM. This represents a 100000-fold improvement with respect to control PSi interferometers biofunctionalized using common silane-based chemistry and a 300-fold improvement with respect to best PSi label-free biosensors reported in the current literature, pushing PSi optical biosensors to performance comparable to those of best label-free plasmonic and photonic platforms.
[1] Layer-by-layer biofunctionalization of nanostructured porous silicon for high-sensitivity and high-selectivity label-free affinity biosensing, S Mariani, V Robbiano, LM Strambini, A Debrassi, G Egri, L Dähne, G. Barillaro, Nature Communications 9 (1), 5256 (2018
Decoration of Porous Silicon with Gold Nanoparticles via Layer-by-Layer Nanoassembly for Interferometric and Hybrid Photonic/Plasmonic (Bio)sensing
No full textGold nanoparticle layers (AuNPLs) enable the coupling of morphological, optical, and electrical properties of gold nanoparticles (AuNPs) with tailored and specific surface topography, making them exploitable in many bioapplications (e.g., biosensing, drug delivery, and photothermal therapy). Herein, we report the formation of AuNPLs on porous silicon (PSi) interferometers and distributed Bragg reflectors (DBRs) for (bio)sensing applications via layer-by-layer (LbL) nanoassembling of a positively charged polyelectrolyte, namely, poly(allylamine hydrochloride) (PAH), and negatively charged citrate-capped AuNPs. Decoration of PSi interferometers with AuNPLs enhances the Fabry-Pérot fringe contrast due to increased surface reflectivity, resulting in an augmented sensitivity for both bulk and surface refractive index sensing, namely, about 4.5-fold using NaCl aqueous solutions to infiltrate the pores and 2.6-fold for unspecific bovine serum albumin (BSA) adsorption on the pore surface, respectively. Sensitivity enhancing, about 2.5-fold, is also confirmed for affinity and selective biosensing of streptavidin using a biotinylated polymer, namely, negatively charged poly(methacrylic acid) (b-PMAA). Further, decoration of PSi DBR with AuNPLs envisages building up a hybrid photonic/plasmonic optical sensing platform. Both photonic (DBR stop-band) and plasmonic (localized surface plasmon resonance, LSPR) peaks of the hybrid structure are sensitive to changes of bulk (using glucose aqueous solutions) and surface (due to BSA unspecific adsorption) refractive index. To the best of our knowledge, this is the first report about the formation of AuNPLs via LbL nanoassembly on PSi for (i) the enhancing of the interferometric performance in (bio)sensing applications and (ii) the building up of hybrid photonic/plasmonic platforms for sensing and perspective biosensing applications
Ultrathin Ambipolar Polyelectrolyte Capacitors Prepared via Layer-by-Layer Assembling
No full textMiniaturized solid state capacitors leveraging migration of unipolar ions in a single polyelectrolyte layer sandwiched between metal electrodes, namely, polyelectrolyte capacitors (PECs), have been recently reported with areal capacitance up to 100–200 nF mm−2. Nonetheless, application of PECs in consumer and industrial electronics has been hindered so far by their small operational frequency range, up to a few kHz, due to the resistive behavior (phase angle >−45°) of PECs in the range kHz-to-MHz. Here, it is reported on multilayer polyelectrolyte capacitors (mPECs) that leverage as dielectric an ambipolar nanometer-thick (down to 10 nm) stack of anionic and cationic polyelectrolytes assembled layer-by-layer between metal electrodes to eliminate the resistive behavior at frequencies from kHz to MHz. This significantly extends the operational range of mPECs over PECs. mPECs with areal capacitance as high as 25 nF mm−2 at 20 Hz and full capacitive behavior from 100 mHz to 10 MHz are demonstrated using different assembling conditions and anionic/cationic polyelectrolyte pairs. The mPECs reliably operate over time for >300 million cycles, at different biasing voltages up to 3 V, and temperatures up to 80 °C, showing a reversible capacitive behavior without significant hysteresis. Application of mPECs in flexible electronics, also operating at high frequency, is envisaged
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Layer-by-layer nano-assembly of charged polyelectrolytes for label-free optical biosensing with nanostructured materials: The case of nanostructured porous silicon interferometers
No full textThe nano-assembly of charged polyelectrolytes via layer-by-layer (LbL) technology on porous silicon (PSi) interferometers is here demonstrated as an effective biofunctionalization approach for high-sensitivity/selectivity labelfree optical biosensing, using streptavidin/biotin affinity detection as case study. Nanostructured PSi interferometers are biofunctionalized with a nano-assembly of a positively-charged polyelectrolyte, namely, PAH (poly(allylamine hydrochloride)), and a negatively-charged biotinylated polyelectrolyte, namely, b-PMAA (poly(methacrylic acid)), via LbL technology. The nano-assembly is stable under operating conditions and enables the selective and sensitive detection of streptavidin with a sub-picomolar detection limit (namely, DL=0.6 pM), which is 105-fold lower than that achieved with PSi interferometers biofunctionalized using standard silane chemistry. Remarkably, the analytical performance achieved for LbL-biofunctionalized PSi interferometers is comparable to those of state-of-the-art label-free photonic and plasmonic platforms
Variations on the Author
No full text“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
No full textWe 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
No full textWe 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
Author, publisher and bookseller : a tripartite synergy in Nigerian book industry
No full textThis work is about the roles of Author, Publisher and Bookseller in Book development in
Nigeria. The paper started by delving into the history of Book Publishing in Nigeria after
which it proceeded by defining who an author, a publisher, and a bookseller is and
expatiated on the indispensable roles of these key actors in Nigerian Book Industry and in
the emerging Information Society. Furthermore, the various constraints to book
development were identified while the paper advised on how the Book Industry can be
further promoted in Nigeria. However, the paper concluded and made recommendations
on how the Book sector can help in enhancing scholarship in the country
The Thursday Murder Club: Launching a megabrand author - a publishing case study
No full textIn 2020, the Christmas book charts in the UK made headlines: Barack Obama’s eagerly awaited autobiography, The Promised Land, was beaten to the top spot by The Thursday Murder Club by Richard Osman, a debut cosy crime novel set in a retirement village. Not only did Osman’s book beat the former US president’s expected bestseller, it also broke records, becoming the fastest-selling debut crime novel of all time. Although Osman has a certain level of fame in the UK from his TV appearances on shows such as Pointless, his celebrity status does not entirely explain the novel’s huge sales. This article tracks the acquisition, publication, and promotion journey of The Thursday Murder Club in order to understand the industry and cultural context of its success and to interrogate the role of celebrity in the creation of author brands. The findings suggest that the unexpected scale of the success of the book owed to a number of factors, including in-depth editing by the novel’s agent, editor, and author to tighten up the plot, an extensive and strategic promotional campaign, the pandemic (which drove interest in the book’s genre and themes), and the quality of the writing. We find that the book’s success was accentuated by Osman’s celebrity status rather than being entirely reliant on it. This research adds to the growing scholarship on celebrity authorship by means of an in-depth case study and provides insight into the processes behind publishing a ‘celebrity’ book and launching a megabrand author
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