1,720,972 research outputs found
Microneedle-based electrochemical devices for transdermal biosensing: a review
No full textMany research efforts over the last decade have been devoted to the development of microneedle-based diagnostic devices for minimally invasive transdermal biosensing and for long-term health monitoring. Transdermal biosensing via microneedle allows the development of minimally invasive easy-to-use point-of-care biodevices. The main objective of this short review is to provide a general overview of the most immediate and relevant progress in microneedle-based transdermal biosensing in the last five years. A critical analysis of the recent literature is finally presented
Inhibition-based biosensor for atrazine detection
No full textThis work presents an inhibition-based biosensor for the fast, simple and inexpensive determination of atrazine. The method is based on the inhibition of the enzyme tyrosinase from mushrooms (Tyr), immobilized on screen printed electrodes (SPEs). To optimize the biosensor performances several carbon based SPEs: graphite (G), graphene (GP), and multiwalled carbon nanotubes (MWCNTs) and immobilization techniques (physical and chemical) have been tested. Tyrosinase was immobilized on the electrode surface by either polyvinyl alcohol with styrylpyridinium groups (PVA-SbQ) as cross-linking agent or Nafion membranes as physical entrapment or bovine serum albumin with glutaraldehyde as chemical immobilization. In the presence of catechol as substrate, atrazine can be determined thanks to its inhibition activity towards the enzyme which catalyzes the oxidation of catechol to o-quinone. Under optimum experimental conditions, the best performance in terms of catalytic efficiency has been demonstrated by MWCNTs screen printed electrode with PVA-SbQ as immobilization method. The developed inhibition biosensor displays a linearity range towards atrazine within 0.5-20 ppm, a LOD of 0.3 ppm and acceptable repeatability and stability. This analysis method was applied to spiked drinking water samples with recoveries close to 95% respect to measurements carried out in PBS buffer. The low cost of this device and its good analytical performances suggest its application for the screening and monitoring of atrazine in real matrices
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
Metal oxide nanoparticle based electrochemical sensor for total antioxidant capacity (TAC) detection in wine samples
No full textA single-use electrochemical screen-printed electrode is reported based on biomimetic properties of nanoceria particles (CeNPs). The developed tool showed an easy approach compared to the classical spectrophotometric methods reported in literature in terms of ease of use, cost, portability, and unnecessary secondary reagents. The sensor allowed the detection of the total antioxidant capacity (TAC) in wine samples. The sensor has been optimized and characterized electrochemically and then tested with antioxidant compounds occurred in wine samples. The electrochemical CeNPs modified sensor has been used for detection of TAC in white and red commercial wines and the data compared to the 2,20-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS)-based spectrophotometric method. Finally, the obtained results have demonstrated that the proposed sensor was suitable for the simple and quick evaluation of TAC in beverage samples
Beyond graphene: Electrochemical sensors and biosensors for biomarkers detection
No full textGraphene's success has stimulated great interest and research in the synthesis and characterization of graphene-like 2D materials, single and few-atom-thick layers of van der Waals materials, which show fascinating and technologically useful properties. This review presents an overview of recent electrochemical sensors and biosensors based on graphene and on graphene-like 2D materials for biomarkers detection. Initially, we will outline different electrochemical sensors and biosensors based on chemically derived graphene, including graphene oxide and reduced graphene oxide, properly functionalized for improved performances and we will discuss the various strategies to prepare graphene modified electrodes. Successively, we present electrochemical sensors and biosensors based on graphene-like 2D materials, such as boron nitride (BN), graphite-carbon nitride (g-C3N4), transition metal dichalcogenides (TMDs), transition metal oxides and graphane, outlining how the new modified 2D nanomaterials will improve the electrochemical performances. Finally, we will compare the results obtained with different sensors and biosensors for the detection of important biomarkers such as glucose, hydrogen peroxide and cancer biomarkers and highlight the advantages and disadvantages of the use of graphene and graphene-like 2D materials in different sensing platforms
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
Evaluation of different storage processes of passion fruit (Passiflora edulis Sims) using a new dual biosensor platform based on a conducting polymer
No full textIn this work, we present a new electrochemical biosensor array for the evaluation of pH changes and total polyphenols content based on a conductive polymer used to immobilize anthraquinone-2-carboxylic acid (ANTQ), on the first electrode, and Trametes versicolor laccase on the second one. In particular, the anthraquinone based electrode was sensitive to pH changes detected through potentiometric measurements, while the laccase-based electrode was used to detect the total polyphenols content by using amperometry. After a preliminary characterization of both electrodes, the so prepared array was used to monitor the variation of pH and polyphenols content in different samples of purple passion fruit (Passiflora edulis Sims) stored post harvesting at different temperatures such as room temperature, 4 oC and -20 oC
Evaluation of new cholinium-amino acids based room temperature ionic liquids (RTILs) as immobilization matrix for electrochemical biosensor development: Proof-of-concept with Trametes Versicolor laccase
No full textIn this work, we present new cholinium-amino acids room temperature ionic liquids (ChAARTILs) that can be used as an efficient immobilization matrix for electrochemical biosensor development. The ideal immobilization strategy should be able to ensure the highest enzyme loading and a tight enzymatic immobilization, preserving its native structure and biological activity. In this regard, ChAARTILs present different side chains on the amino acids giving rise to van der Waals, π-π stacking and hydrogen bonding interactions. All these interactions can affect the nanomaterial organization onto the electrode surface. To this aim, we have evaluated the main electrochemical parameters, namely electroactive area (AEA) and the heterogeneous electron transfer rate constant (k0), showing how both cations and anions of room temperature ionic liquids (RTILs) can independently affect multi-walled carbon nanotubes (MWCNTs) organization. In particular, [Ch][Phe] showed the best performance in terms of AEA (3.432 cm2) and k0 (4.71·10−3 cm s−1) with a homogeneous distribution of MWCNTs bundles onto the electrodes and a faster electron transfer rate. Finally, the modified electrode (MWCNTs-[Ch][Phe]) has been tested with a model enzyme, namely Trametes versicolor laccase (Tvl), in order to evaluate the possibility to use ChAARTILs as immobilization matrix, preventing enzymatic denaturation phenomena which would affect the biosensor performance in terms of sensitivity, linear range, and stability
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