Percorrer por autor "Almeida, M. Gabriela"
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- Construction of effective disposable biosensors for point of care testing of nitritePublication . Monteiro, Tiago; Rodrigues, Patrícia R.; Gonçalves, Ana Luisa; Moura, José J.G.; Jubete, Elena; Añorga, Larraitz; Piknova, Barbora Piknova; Schechter, Alan N.; Silveira, Célia M.; Almeida, M. Gabriela"In this paper we aim to demonstrate, as a proof-of-concept, the feasibility of the mass production of effective point of care tests for nitrite quantification in environmental, food and clinical samples. Following our previous work on the development of third generation electrochemical biosensors based on the ammonia forming nitrite reductase (ccNiR), herein we reduced the size of the electrodes’ system to a miniaturized format, solved the problem of oxygen interference and performed simple quantification assays in real samples. In particular, carbon paste screen printed electrodes (SPE) were coated with a ccNiR/carbon ink composite homogenized in organic solvents and cured at low temperatures. The biocompatibility of these chemical and thermal treatments was evaluated by cyclic voltammetry showing that the catalytic performance was higher with the combination acetone and a 40 °C curing temperature. The successful incorporation of the protein in the carbon ink/solvent composite, while remaining catalytically competent, attests for ccNiR’s robustness and suitability for application in screen printed based biosensors. Because the direct electrochemical reduction of molecular oxygen occurs when electroanalytical measurements are performed at the negative potentials required to activate ccNiR (ca. -0.4 V vs Ag/AgCl), an oxygen scavenging system based on the coupling of glucose oxidase and catalase activities was successfully used. This enabled the quantification of nitrite in different samples (milk, water, plasma and urine) in a straightforward way and with small error (1 – 6%). The sensitivity of the biosensor towards nitrite reduction under optimized conditions was 0.55 A M-1 cm-2 with a linear response range 0.7 – 370 μM."
- Development of new analytical tools for monitoring of cardiovascular disease markers – towards the detection of homocysteine-thiolactonePublication . Monteiro, Tiago; Oliveira, Francisco; Silveira, Célia M.; Pereira, Sofia A.; Almeida, M. Gabriela
- Diagnosis of SARS-Cov-2 infection by RT-PCR using specimens other than naso- and oropharyngeal swabs : a systematic review and meta-analysisPublication . Moreira, Vânia M.; Mascarenhas, Paulo; Machado, Vanessa; Botelho, João; Mendes, José João; Taveira, Nuno; Almeida, M. GabrielaThe rapid and accurate testing of SARS-CoV-2 infection is still crucial to mitigate, and eventually halt, the spread of this disease. Currently, nasopharyngeal swab (NPS) and oropharyngeal swab (OPS) are the recommended standard sampling techniques, yet, these have some limitations such as the complexity of collection. Hence, several other types of specimens that are easier to obtain are being tested as alternatives to nasal/throat swabs in nucleic acid assays for SARS-CoV-2 detection. This study aims to critically appraise and compare the clinical performance of RT-PCR tests using oral saliva, deep-throat saliva/posterior oropharyngeal saliva (DTS/POS), sputum, urine, feces, and tears/conjunctival swab (CS) against standard specimens (NPS, OPS, or a combination of both). In this systematic review and meta-analysis, five databases (PubMed, Scopus, Web of Science, ClinicalTrial.gov and NIPH Clinical Trial) were searched up to the 30th of December, 2020. Case-control and cohort studies on the detection of SARS-CoV-2 were included. The methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS 2). We identified 1560 entries, 33 of which (1.1%) met all required criteria and were included for the quantitative data analysis. Saliva presented the higher accuracy, 92.1% (95% CI: 70.0–98.3), with an estimated sensitivity of 83.9% (95% CI: 77.4–88.8) and specificity of 96.4% (95% CI: 89.5–98.8). DTS/POS samples had an overall accuracy of 79.7% (95% CI: 43.3–95.3), with an estimated sensitivity of 90.1% (95% CI: 83.3–96.9) and specificity of 63.1% (95% CI: 36.8–89.3). The remaining index specimens could not be adequately assessed given the lack of studies available. Our meta-analysis shows that saliva samples from the oral region provide a high sensitivity and specificity; therefore, these appear to be the best candidates for alternative specimens to NPS/OPS in SARS-CoV-2 detection, with suitable protocols for swab-free sample collection to be determined and validated in the future. The distinction between oral and extra-oral salivary samples will be crucial, since DTS/POS samples may induce a higher rate of false positives. Urine, feces, tears/CS and sputum seem unreliable for diagnosis. Saliva testing may increase testing capacity, ultimately promoting the implementation of truly deployable COVID-19 tests, which could either work at the point-of-care (e.g. hospitals, clinics) or at outbreak control spots (e.g., schools, airports, and nursing homes).
- Effect of saccharomycin, a natural Saccharomyces cerevisiae biocide, on Hanseniaspora guilliermondii cells surfacePublication . Calvário, Joana; Silva, Nelly; Almeida, M. Gabriela; Albergaria, Helena; Eaton, Peter; Macedo, Anjos; Caldeira, Jorge
- Inhibition-based biosensor for cyanide detection – a preliminary studyPublication . Coelho, Ana R.; Monteiro, Tiago; Viana, Ana S.; Almeida, M. Gabriela
- Microelectrode sensor for real-time measurements of nitrite in the living brain, in the presence of ascorbatePublication . Monteiro, Tiago; Dias, Cândida; Lourenço, Cátia F.; Ledo, Ana; Barbosa, Rui M.; Almeida, M. GabrielaThe impaired blood flow to the brain causes a decrease in the supply of oxygen that can result in cerebral ischemia; if the blood flow is not restored quickly, neuronal injury or death will occur. Under hypoxic conditions, the production of nitric oxide (●NO), via the classical L-arginine–●NO synthase pathway, is reduced, which can compromise ●NO-dependent vasodilation. However, the alternative nitrite (NO2−) reduction to ●NO, under neuronal hypoxia and ischemia conditions, has been viewed as an in vivo storage pool of ●NO, complementing its enzymatic synthesis. Brain research is thus demanding suitable tools to probe nitrite’s temporal and spatial dynamics in vivo. In this work, we propose a new method for the real-time measurement of nitrite concentration in the brain extracellular space, using fast-scan cyclic voltammetry (FSCV) and carbon microfiber electrodes as sensing probes. In this way, nitrite was detected anodically and in vitro, in the 5–500 µM range, in the presence of increasing physiological concentrations of ascorbate (100–500 µM). These sensors were then tested for real-time and in vivo recordings in the anesthetized rat hippocampus; using fast electrochemical techniques, local and reproducible transients of nitrite oxidation signals were observed, upon pressure ejection of an exogenous nitrite solution into the brain tissue. Nitrite microsensors are thus a valuable tool for investigating the role of this inorganic anion in brain redox signaling.
- New PON1-based biosensor for the detection of homocysteine-thiolactone in human plasmaPublication . Monteiro, Tiago; Oliveira, Francisco; Silveira, Célia M.; Pereira, Sofia A.; Almeida, M. Gabriela
- Nitrite reduction in bacteria : a comprehensive view of nitrite reductasesPublication . Besson, Stéphane; Almeida, M. Gabriela; Silveira, Célia M.The last years have witnessed a steady increase of social and political awareness for the need of studying, monitoring, and controlling several anthropological activities that are dramatically impacting the environment and human health. The increasing turnover rates of the nitrogen cycle across the Planet are of major concern, so the understanding of the biological, chemical, and physical processes associated with the biogeochemical nitrogen cycle has been attracting the attention of several scientific disciplines. For many years, the primary focus has been the so-called “dissimilatory reduction of nitrate”, which refers to the stepwise conversion of nitrate into molecular nitrogen, closely followed by the assimilatory nitrate reduction pathway, which allow nitrogen incorporation into biomolecules. The contribution of bioinorganic chemists to better understand the enzymology underlying these two branches of the N-cycle has been remarkable. The constant development of mechanistic, structural, and biological tools has been keeping this bioinorganic chemistry field very active, making it a highly relevant research area still today. In this paper, we review the state-of-the-art in both dissimilatory and assimilatory nitrite reducing enzymes, highlighting the structural peculiarities of the different metalloenzymes involved in this step.
- Probing the surface chemistry of different oxidized MWCNT for the improved electrical wiring of cytochrome c nitrite reductasePublication . Silveira, Célia M.; Pimpão, Marta; Pedroso, Humberto A.; Rodrigues, Patrícia R. S.; Moura, José J. G.; Pereira, Manuel F. R.; Almeida, M. Gabriela"This work reports the evaluation of a set of multi-walled carbon nanotubes (MWCNT) presenting different surface chemistries, as interfaces for the direct electrochemistry of the multihemic nitrite reductase (ccNiR) from Desulfovibrio desulfuricans ATCC27774 (Dd). The carbon nanotubes dispersions were prepared in aqueous media and deposited on pyrolytic graphite (PG) macroelectrodes, following a layer-by-layer methodology. The resulting MWCNT bed was coated with ccNiR and studied by cyclic voltammetry. Interestingly, although small non-catalytic cathodic waves were detected in all carbon nanotubes bioconjugates, the complexity of these electrochemical signals was partially deconvoluted in some materials, the less acidic ones emphasizing the contribution of the catalytic centre. Consistently, these MWCNT were the most favourable for enzyme catalysis, highlighting the importance of the surface oxide functionalities to enzyme reactivity."
- Respiratory versatility in Desulfovibrio desulfuricans ATCC 27774 – a proteomic approachPublication . Sousa, Joana R.; Silveira, Célia M.; Moura, Isabel; Moura, José J. G.; Almeida, M. Gabriela