1,720,969 research outputs found
Development of microarrays for protein and genetic screening with an Electrochemical and Elctrochemiluminescence-based transduction scheme.
No full textConsidering the increasing need for sensing elements that is emerging in different fields and applications, particularly in relation to the Internet of Things, electrochemical sensors and biosensors, also for their exceptional attributes, such as being easy-to-operate, economical, sensitive, portable, are candidates to become essential pillars in future scenarios and to play a significant role biomedical and environmental monitoring.
Electrochemical and electrochemiluminescent sensors, are devices capable of detecting molecules and biomolecules in solutions and determining the concentration through direct electrical measurements, arising from the change in the redox state of the analyte, and monitored through classical electroanalytical techniques. Remarkably, recent achievements in nanoscience and nanotechnology, have demonstrated the potential for improving greatly both the sensitivity and selectivity of electrochemical sensors and biosensors. In fact, an electrochemical sensor can be miniaturized to a size less than one micrometer or to small-size arrays of nano-electrodes, offering advantages in terms of increased sensitivity and compactness (NEA). The attractiveness of such nanostructured systems resides also in the possibility to immobilized biomolecules on the dielectric surface surrounding each nanoelectrode, instead of on the electrode itself. Therefore, in NEAs, where the electrochemical properties of the electrode and the physical-chemical properties of the dielectric surface may be optimized independently, it may result easier to combine the highly specific molecular recognition mechanisms with high sensitivity (low detection limits).
The aim of this work is the development of nanostructured electrochemical and electrochemiluminescence-based sensors for the detection of biomolecules, such as DNA and proteins.
The fabrication of arrays of nanoelectrodes was performed by deposition of a thin film of polycarbonate (PC) as insulator on a layer of Boron Doped Diamond (BDD) or Glassy Carbon (GC). NEAs were obtained by creating an array of nanoholes in the polymeric film using two different nanofabrication techniques: electron beam lithography (EBL) and nanoimprint lithography (NIL). These approaches lead to the formation of recessed nanoelectrodes. Particulary, the optimization of the parameters to fabricate NEAs by nanoimprint lithography (NIL) has allowed to reduce time and manufacturing costs.
We demonstrate the possibility to efficiently immobilize biomolecules, on the relatively large surface of the PC of our NEAs in order to develop sensitive electrochemical biosensors.
Initially, the sensors were tested for the detection of HPV (Human Papilloma Virus) DNA sequences. Later we focused on the optimization of the protocol for the detection of proteins by enzyme immuno-assay with the enzyme Horse Radish Peroxidase (HRP), using Gliadin and Tumor necrosis factor (TNF-α) as target. The process of bio-recognition and detection was carried out by cyclic voltammetry and consists of an immuno-indirect scheme. This method allows to detect a concentration of 0.1 nM for Gliadin fragment and the experiments performed indicate the possibility to further low this limit.
The same samples were tested at the Institut des Sciences Molèculaires University of Bordeaux (Group of Nanosystèmes Analitique) using electrochemiluminescence (ECL). In these sensors the transduction scheme involves a secondary antibody labbeled with Biotin, that provides a strong interaction with the complex streptavidin- Ru(bpy)32+. The ECL signal obtained in the presence of the co-reactant tripropylamine (TPrA) was recorded using both a CCD camera and a photomultiplier tube. Furthemore, additional sensors have been prepared using GC as conductive material and PC as insulating layer
From theory to practice: understanding the challenges in the implementation of electrogenerated chemiluminescence for analytical applications
Full text linkElectrogenerated chemiluminescence (ECL) stands out as a remarkable phenomenon of light emission at electrodes initiated by electrogenerated species in solution. Characterized by its exceptional sensitivity and minimal background optical signals, ECL finds applications across diverse domains, including biosensing, imaging, and various analytical applications. This review aims to serve as a comprehensive guide to the utilization of ECL in analytical applications. Beginning with a brief exposition on the theory at the basis of ECL generation, we elucidate the diverse systems employed to initiate ECL. Furthermore, we delineate the principal systems utilized for ECL generation in analytical contexts, elucidating both advantages and challenges inherent to their use. Additionally, we provide an overview of different electrode materials and novel ECL-based protocols tailored for analytical purposes, with a specific emphasis on biosensing applications. Graphical abstract: (Figure presented.
Enhancing electrochemiluminescence intensity through emission layer control
Full text linkElectrochemiluminescence (ECL), an intriguing luminescent phenomenon induced by electrochemical stimulation, has evolved from studying electron transfer reactions to a powerful analytical method and imaging technique. ECL can be generated through annihilation or co-reactant methods, with recent advancements integrating it into imaging devices for diverse applications. This review traces the evolution of ECL from its early applications to recent developments in imaging technology. Notably, the utilization of charge-coupled devices (CCD) and electron multiplying charge-coupled devices (EMCCD) in ECL microscopy has revolutionized imaging capabilities, making it a cost-effective option for point-of-care testing. The review explores the heterogeneous ECL mechanism, emphasizing its limitations and challenges in visualizing objects away from the electrode surface. The synergy between ECL and microscopy is highlighted, showcasing its diverse applications and contributions to understanding ECL mechanisms and improving its use in biological contexts. Finally, the review encapsulates innovative approaches in material design, surface modification, and electrode architecture, providing a comprehensive overview of strategies to control the active layer of the ECL and advance ECL microscopy
Accurate pH Monitoring of Highly Concentrated Saline Aqueous Solutions (Seawater-like) with a pH Colorimetric Sensor Array
No full textA pH colorimetric sensor array (CSA) was prepared on a nitrocellulose membrane and used for accurate pH measurement in highly concentrated saline solutions. The CSAs consisted of sensing spots made of a suitable OrMoSil polymer prepared from organo-fluorinated-silane precursors and/or organosilane with tetraethyl orthosilicate hosting an acid-base indicator. Four CSAs were prepared: D, 1F, 2F, and 3F. In D, a nonfluorinated organosilane was present. From 1F to 3F, the concentration of the fluorinated organosilane increased and improved the pH measurement accuracy in highly saline concentrations. No recalibrations were required, and the analytical signal was stable in time. D, 1F, 2F, and 3F were deposited in triplicate, and they were prepared to work in the seawater pH interval (7.50-8.50). The use of fluorinated precursors led to a lower pH prediction error and tailored the interval of the CSA at more basic pH values so that the inflection points of the sigmoidal calibrations of D, 1F, 2F, and 3F moved from 6.97 to 7.98. The overall pH prediction error was 0.10 pH (1F), 0.02 pH (2F), and 0.04 pH units (3F). The CSAs were stable, reversible, reusable, and independent of salinity (S) between 20 and 40. The performances of the CSA were compared with those of a glass electrode, whose pHNIST values were converted in the pHSWS scale through a conversion equation. Being unaffected by the typical drawback of the glass electrode, the CSAs can be used directly in seawater real samples, and it validated the proposed conversion equation
A Guide Inside Electrochemiluminescent Microscopy Mechanisms for Analytical Performance Improvement
Full text linkECL is luminescence generated by electrochemical reactions and for this reason it possesses better spatio-temporal control and low background in comparison with photoluminescence or other optical methods that rely on external light illumination.1–3 In the last 20 years ECL has proved to be a versatile and powerful analytical technique in different fields, ranging from fundamental research to commercial clinical and biological applications.4,5 The main reason behind its success is that ECL offers remarkable advantages in comparison to other transduction methods: high sensitivity, an extremely wide dynamic range, very low background signal, good temporal and spatial control, and insensitivity to matrix effects.6,7 Thanks to its simplified optical setup, ECL has been implemented as a powerful imaging technique to visualize electrochemical objects and entities bringing important insight in the ECL mechanism generation. Here we aim to incorporate all the work done in the field of ECL imaging mainly in the last three years with a particular focus on ECL generation mechanisms and their applications
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
Development of an immunoenzymatic method for monitoring glyphosate in water using magnetic nanoparticles for environmental remediation applications
No full textreservedIl glifosato è il principio attivo di numerose formulazioni commerciali di erbicidi non selettivi e, grazie alla sua efficacia, è il più utilizzato al mondo. Dato il suo massiccio ed eccessivo impiego, diversi studi hanno suscitato rilevanti preoccupazioni non solo per le conseguenze che provoca nell’ambiente e nel biota, ma anche per la sua probabile tossicità nell’uomo. L’ardua sfida nel dimostrare la potenziale tossicità e di conseguenza l’assenza di politiche di sanità pubblica derivano dalla difficoltà della sua rilevazione nell’ambiente. Le tecnologie analitiche per la quantificazione e rilevazione del glifosato che generalmente vengono utilizzate richiedono attrezzature di fascia alta e non sono adatte ad un monitoraggio sul campo in tempo reale.
Il presente progetto di tesi si propone di sviluppare un metodo immunoenzimatico per la rilevazione del glifosato nell’acqua, utilizzando nanoparticelle magnetiche di ossido ferroso-ferrico funzionalizzate con titanio, che consentono l’adsorbimento del glifosato sulla loro superficie. La rilevazione è stata effettuata tramite un saggio immuno-indiretto utilizzando un anticorpo secondario marcato con perossidasi di rafano (HRP) e misurando la corrente prodotta con elettrodi di carbonio screen-printed (SPE). Sono state testate concentrazioni di glifosato nel range 100-2000 μg/L, mantenendo costante la concentrazione di nanoparticelle magnetiche (1000 mg/L). Il protocollo è stato in seguito ottimizzato, raggiungendo le condizioni ottimali per la rilevazione e discriminazione delle diverse concentrazioni di glifosato in termini di variazione di corrente di riduzione. Il progetto risulta essere una ricerca preliminare, in cui i risultati ottenuti sono promettenti per un futuro sistema da poter utilizzare come metodo di monitoraggio per applicazioni di risanamento ambientale.Glyphosate is the active ingredient in many commercial formulations of non-selective herbicides and, due to its effectiveness, is the most widely used in the world. Due to its massive and excessive use, several studies have raised significant concerns not only for the consequences it causes in the environment and biota, but also for its likely toxicity in humans. The major challenge in demonstrating potential toxicity and consequently the absence of public health policies arise from the difficulty of detecting it in the environment. The analytical glyphosate quantification and detection technologies that are generally used require high-end equipment and are not suitable for real-time field monitoring.
This thesis project aims to develop an immunoenzymatic method for the detection of glyphosate in water, using magnetic nanoparticles of ferrous-ferric oxide functionalized with titanium, which allow the adsorption of glyphosate on their surface. The detection was carried out by an immuno-indirect assay using a secondary antibody labelled with horseradish peroxidase (HRP) and measuring the current produced with screen-printed carbon electrodes (SPE). Glyphosate concentrations were tested in the range of 100-2000 μg/L, maintaining the concentration of magnetic nanoparticles constant (1000 mg/L). The protocol was subsequently optimized, achieving optimal conditions for detecting and discriminating the different concentrations of glyphosate in terms of reduction current variation. The project turns out to be preliminary research, in which the results obtained are promising for a future system to be used as a monitoring method for environmental remediation applications
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
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