Browsing by Author "Monteiro, Tiago"
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- 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
- 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
- O papel das organizações africanas na resposta ao fenómeno da pirataria e do assalto armado no mar contemporâneo, na região do Golfo da GuinéPublication . Monteiro, TiagoApós a resposta global à pirataria na costa da Somália, as atenções viraram-se para o Golfo da Guiné na última década. Ao tornar-se a zona marítima mais perigosa do continente africano, em termos de ataques, sequestros e outros atos ilícitos, o Conselho de Segurança das Nações Unidas adotou as Resoluções 2018 e 2039, onde expressa a preocupação com a insegurança marítima e as suas consequências globais e regionais. Foi no seguimento das Resoluções que as Comunidades Económicas da África Ocidental e Central criaram um mecanismo cooperativo entre os 25 Estados-membro, chamado Arquitetura de Segurança Marítima de Yaoundé. Considerando o impacto que uma resposta regional coordenada pode ter no combate a este fenómeno, importa analisar e compreender os progressos conseguidos pela Arquitetura e de que forma contribui para a diminuição da atividade da pirataria e assalto armado no mar. A investigação seguiu um raciocínio indutivo, baseado numa estratégia de investigação qualitativa, recorrendo-se à análise documental e a entrevistas semiestruturadas. Da investigação resultou que a Arquitetura, tirando proveito do apoio de organizações internacionais, integra um conjunto de projetos importantes, relativamente às dimensões da proteção, segurança e partilha de informações. No entanto, carece de um esforço regional para responder às necessidades de governança no domínio judicial. Abstract: Following the global response to piracy off the coast of Somalia, attention has turned to the Gulf of Guinea over the past decade. By becoming the most dangerous maritime zone on the African continent with attacks, kidnappings and other illicit acts, the United Nations Security Council adopted Resolutions 2039 and 2018, which expresses concerns about maritime insecurity and its global and regional consequences. It was following the Resolutions that the Economic Communities of West and Central Africa created a cooperative mechanism between the 25 Member States, called the Yaoundé Architecture. Considering the impact that a coordinated regional response can have in combating this phenomenon, it is important to analyze and understand the progress achieved by Architecture and how it contributes to the decrease of piracy and armed robbery at sea. The investigation followed an inductive reasoning, based on a qualitative research strategy, using document analysis and semi-structured interviews. The research concluded that the Architecture, taking benefit of the support of international organizations, integrates a set of important projects, regarding the dimensions of protection, security and information sharing. However, it lacks a regional effort to respond to governance needs in the judicial domain.
- A quasi-reagentless point-of-care test for nitrite and unaffected by oxygen and cyanidePublication . Monteiro, Tiago; Gomes, Sara; Jubete, Elena; Añorga, Larraitz; Silveira, Célia M.; Almeida, Maria GabrielaThe ubiquitous nitrite is a major analyte in the management of human health and environmental risks. The current analytical methods are complex techniques that do not fulfil the need for simple, robust and low-cost tools for on-site monitoring. Electrochemical reductase-based biosensors are presented as a powerful alternative, due to their good analytical performance and miniaturization potential. However, their real-world application is limited by the need of anoxic working conditions, and the standard oxygen removal strategies are incompatible with point-of-care measurements. Instead, a bienzymatic oxygen scavenger system comprising glucose oxidase and catalase can be used to promote anoxic conditions in aired environments. Herein, carbon screen-printed electrodes were modified with cytochrome c nitrite reductase together with glucose oxidase and catalase, so that nitrite cathodic detection could be performed by cyclic voltammetry under ambient air. The resulting biosensor displayed good linear response to the analyte (2–200 µM, sensitivity of 326 ± 5 mA M−1 cm−2 at −0.8 V; 0.8–150 µM, sensitivity of 511 ± 11 mA M−1 cm−2 at −0.5 V), while being free from oxygen interference and stable up to 1 month. Furthermore, the biosensor’s catalytic response was unaffected by the presence of cyanide, a well-known inhibitor of heme-enzymes.