1,720,975 research outputs found
PNA-functionalized magnetic microbeads as substrates for enzyme-labelled voltammetric genoassay for DNA sensing applied to identification of GMO in food
No full textA novel enzyme-labelled voltammetric magnetogenoassay for DNA sensing based on the use of carboxyl-surface coated magnetic microbeads functionalized with PNA probes and subsequent read-out on screen-printed electrode (SPE) substrates was developed. The assay was validated for determination of non-amplified genomic DNA from genetically modified Roundup Ready soy. Outstanding performance with respect to other genoassays requiring preliminary amplification of target DNA via PCR was demonstrated. The analytical performance was also improved compared to previous methods based on the immobilization of the same PNA probes on SPE substrates, since the method was found capable of achieving LOD and LOQ of 415 fM and 995 fM, respectively. The ability of the magnetogenoassay to detect the presence of Roundup Ready soy DNA sequence was tested on genomic DNA extract from European Reference Material soy flours, demonstrating the capability of the method to match the European Union regulation for labelling of food containing a percentage of GM products greater than 0,9%
A Folding-Based Electrochemical Aptasensor for the Single-Step Detection of the SARS-CoV-2 Spike Protein
Full text linkEfficient and timely testing has taken center stage in the management, control, and monitoring of the current COVID-19 pandemic. Simple, rapid, cost-effective diagnostics are needed that can complement current polymerase chain reaction-based methods and lateral flow immunoassays. Here, we report the development of an electrochemical sensing platform based on single-walled carbon nanotube screen-printed electrodes (SWCNT-SPEs) functionalized with a redox-tagged DNA aptamer that specifically binds to the receptor binding domain of the SARS-CoV-2 spike protein S1 subunit. Single-step, reagentless detection of the S1 protein is achieved through a binding-induced, concentration-dependent folding of the DNA aptamer that reduces the efficiency of the electron transfer process between the redox tag and the electrode surface and causes a suppression of the resulting amperometric signal. This aptasensor is specific for the target S1 protein with a dissociation constant (K-D) value of 43 +/- 4 nM and a limit of detection of 7 nM. We demonstrate that the target S1 protein can be detected both in a buffer solution and in an artificial viral transport medium widely used for the collection of nasopharyngeal swabs, and that no cross-reactivity is observed in the presence of different, non-target viral proteins. We expect that this SWCNT-SPE-based format of electrochemical aptasensor will prove useful for the detection of other protein targets for which nucleic acid aptamer ligands are made available
A novel magnetic ligand-based assay for the electrochemical determination of BRD4
No full textThe first magnetic ligand-based electrochemical assay aimed at the determination of BRD4 was developed and validated. BRD4 is an epigenetic regulator of great interest in oncology in relation to its overexpression observed in the pathogenesis of several cancer diseases. BRD4 also represents a major target for the development of innovative treatments aimed at protein inhibition or degradation. Despite the relevance of BRD4 both for diagnostics and therapeutic purposes, current methodologies for its determination are limited to commercial ELISA kits. We present a novel magnetic ligand-based assay for the electrochemical determination of BRD4. The developed assay is based on the use of a small synthetic fragment of the natural protein ligand for BRD4 as receptor, thus exploiting the intrinsic biological protein-protein recognition mechanism. In addition, the assay features the use of magnetic beads as immobilization platforms and peroxidase-conjugated monoclonal anti-BRD4 antibody for the generation of the electrochemical signal. The ligand-based assay shows outstanding performance in terms of rapidity, with results achievable in less than 20 min, no matrix effect when applied to human plasma or cell lysate samples, and excellent specificity. The proposed method exhibits a limit of detection of 2.66 nM and a response range tunable as a function of the amount of immobilized receptor. The developed ligand-based assay was successfully applied to the accurate determination of BRD4 in untreated cell lysates, as proven by the ELISA reference method. The good performance of the proposed bioassay for determination of BRD4 showed potential application of this strategy in convenient point-of-care testing
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
Novel amperometric genosensor based on peptide nucleic acid (PNA) probes immobilized on carbon nanotubes-screen printed electrodes for the determination of trace levels of non-amplified DNA in genetically modified (GM) soy
Full text linkA novel amperometric genosensor based on PNA probes covalently bound on the surface of Single Walled Carbon
Nanotubes – Screen Printed Electrodes (SWCNT-SPEs) was developed and validated in samples of non-amplified
genomic DNA extracted from genetically modified (GM)-Soy. The sandwich assay is based on a first recognition
of a 20-mer portion of the target DNA by a complementary PNA Capture Probe (CP) and a second hybridization
with a PNA Signalling Probe (SP), with a complementary sequence to a different portion of the target DNA. The
SP was labelled with biotin to measure current signal by means of a final incubation of an Alkaline Phosphatasestreptavidin
conjugate (ALP-Strp). The electrochemical detection was carried out using hydroquinone diphosphate
(HQDP) as enzymatic substrate. The genoassay provided a linear range from 250 pM to 2.5 nM, LOD of
64 pM and LOQ of 215 pM Excellent selectivity towards one base mismatch (1-MM) or scrambled (SCR) sequences
was obtained. A simple protocol for extraction and analysis of non-amplified soybean genomic DNA
without sample treatment was developed and validated. Our study provides insight into how the outstanding
recognition efficiency of PNAs can be combined with the unique properties of CNTs in terms of signal response
enhancement for direct detection of genomic DNA samples at the level of interest without previous amplificatio
An integrated IoT-Wi-Fi board for remote data acquisition and sharing from innovative immunosensors. Case of study: Diagnosis of celiac disease
Full text linkA new compact diagnostic device exploiting the integration of screen printed electrode-based immunosensors and remote-controlled IoT-WiFi acquisition board has been realized and validated for diagnosis of Celiac Disease as case of study. The immunodevice is based on chemisorption of open tissue transglutaminase enzyme on the surface of gold nanoparticles-functionalized carbon screen printed electrodes. IgA and IgG anti-tissue transglutaminase target antibodies are recognized by the immobilized bioreceptor as highly specific biomarkers related to Celiac Disease. The signal from the amperometric sensor is acquired and processed through on-purpose developed IoT-WiFi integrated board, allowing for real-time data sharing on cloud services to directly notify all users (physicians, caregivers, etc.) on device outcome. The proposed solution does not require customized hardware or software. The analytical performances of the immunosensors were optimized by experimental design, obtaining diagnostically useful limit of detection (LOD) and limit of quantitation (LOQ) values (LODIgA=3.2 AU mL−1; LODIgG=1.4 AU mL−1; LOQIgA=4.6 AU mL−1; LOQIgG =2.3 AU mL−1) as well as good intermediate precision (RSD < 5%). The high discrimination capability of the IoT-Wi-Fi device between positive and negative serum control resulted to be suitable for diagnostic purposes, with outstanding statistical significance (p < 0,001
A Wi-Fi cloud-based portable potentiostat for electrochemical biosensors
Full text linkThe measurement of the analyte concentration in electrochemical biosensors traditionally requires costly laboratory equipment to obtain accurate results. Innovative portable solutions have recently been proposed, but usually, they lean on personal computers (PCs) or smartphones for data elaboration and they exhibit poor resolution or portability and proprietary software. This paper presents a low-cost portable system, assembling an ad hoc -designed analog front end (AFE) and a development board equipped with a system on chip integrating a microcontroller and a Wi-Fi network processor. The wireless module enables the transmission of measurements directly to a cloud service for sharing device outcome with users (physicians, caregivers, and so on). In doing so, the system does not require neither the customized software nor other devices involved in data acquisition. Furthermore, when any Internet connection is lost, the data are stored on board for subsequent transmission when a Wi-Fi connection is available. The noise output voltage spectrum has been characterized. Since the designed device is intended to be battery-powered to enhance portability, investigations about battery lifetime were carried out. Finally, data acquired with a conventional benchtop Autolab PGSTAT-204 electrochemical workstation are compared with the outcome of our developed device to validate the effectiveness of our proposal. To this end, we selected ferri/ferrocyanide as redox probe, obtaining the calibration curves for both the platforms. The final outcomes are shown to be feasible, accurate, and repeatable
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
- …
