Browsing by Author "Pereira, Clara"
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- Chronoamperometric magnetogenosensing for simultaneous detection of two Roundup Ready™ soybean lines: GTS 40-3-2 and MON89788Publication . Plácido, Alexandra; Pereira, Clara; Barroso, M. Fátima; de-los-Santos-Álvarez, Noemí; Delerue-Matos, CristinaDevelopment of expeditious analytical methods for the detection of genetically modified organisms (GMOs) is increasingly necessary, not only to verify compliance with labelling, but also to help industry to efficiently control the reception of raw materials. On the basis of this, a disposable electrochemical magnetogenoassay is proposed for simultaneous detection of two Roundup Ready (RR) soybean lines GTS 40-3-2 and MON89788, using gold-coated magnetic nanoparticles (Fe3O4@Au) as nanosupport. To perform this magnetogenoassay, a sandwich-type hybridization assay was used with different enzymatic labelling systems (fluorescein isothiocyanate and digoxigenin) and dual screen-printed carbon electrodes (SPdCEs), which allowed the simultaneous readout of each target. A linear relationship ranging from 0.1 to 2.5 nM and from 0.1 to 1.0 nM was achieved for GTS 40-3-2 and MON89788 events, respectively, and both assays showed a similar detection limit of about 0.1 nM. Furthermore, a good performance in terms of precision and selectivity was achieved. The proposed approach is a step forward for event-specific multiplex detection.
- Electrochemical genoassays on gold-coated magnetic nanoparticles to quantify genetically modified organisms (GMOs) in food and feed as GMO percentagePublication . Plácido, Alexandra; Pereira, Clara; Guedes, Alexandra; Barroso, M. Fátima; Miranda-Castro, Rebeca; Santos-Álvarez, Noemí de-los-; Delerue-Matos, CristinaThe integration of nanomaterials in the field of (bio)sensors has allowed developing strategies with improved analytical performance. In this work, ultrasmall core-shell Fe3O4@Au magnetic nanoparticles (MNPs) were used as the platform for the immobilization of event-specific Roundup Ready (RR) soybean and taxon-specific DNA sequences. Firstly, monodisperse Fe3O4 MNPs were synthesized by thermal decomposition and subsequently coated with a gold shell through reduction of Au(III) precursor on the surface of the MNPs in the presence of an organic capping agent. This nanosupport exhibited high colloidal stability, average particle size of 10.2 ± 1.3 nm, and spherical shape. The covalent immobilization of ssDNA probe onto the Au shell of the Fe3O4@Au MNPs was achieved through a self-assembled monolayer (SAM) created from mixtures of alkane thiols (6-mercapto-1-hexanol and mercaptohexanoic acid). The influence of the thiols ratio on the electrochemical performance of the resulting electrochemical genoassays was studied, and remarkably, the best analytical performance was achieved for a pure mercaptohexanoic acid SAM. Two quantification assays were designed; one targeting an RR sequence and a second targeting a reference soybean gene, both with a sandwich format for hybridization, signaling probes labelled with fluorescein isothiocyanate (FITC), enzymatic amplification and chronoamperometric detection at screen-printed carbon electrodes (SPCE). The magnetogenoassays exhibited linear ranges from 0.1 to 10.0 nM and from 0.1 to 5.0 nM with similar detection limits of 0.02 nM and 0.05 nM for the event-specific (RR) and the taxon-specific (lectin) targets, respectively. The usefulness of the approach was demonstrated by its application to detect genetically modified organisms (GMOs) in feed and food.
- Influência da intervenção osteopática na atividade do sistema imunitário: revisão sistemáticaPublication . Azevedo, César; Pereira, Clara; Oliveira, Fábio; Castro, Inês; Oliveira, Rui; Campelo, Natália; Sousa, HelenaO sistema imunitário apresenta funções vitais de proteção do organismo através de vários órgãos, células e proteínas. Existem vários fatores que influenciam a imunidade, sendo que o papel da intervenção osteopática, potenciando e estimulando a sua resposta, tem sido mencionado como promissor coadjuvante não-farmacêutico de baixo custo que visa modular a secreção de citocinas. Realizar uma análise crítica da qualidade metodológica, sobre a intervenção osteopática no sistema imunitário, em adultos, considerando dados laboratoriais de citocinas. Foi realizada uma pesquisa na PubMed, Web of Science Core Collection e EBSCOhost Datasets (Academic Search Complete). Foram incluídos ensaios clínicos randomizados em adultos saudáveis ou com patologias associadas, verificando a influência da intervenção osteopática na atividade do sistema imunitário, através de concentrações laboratoriais de citocinas no organismo. Após a seleção dos estudos, os dados foram extraídos e compilados. Avaliou-se a qualidade metodológica com Cochrane Risk of Bias Tool. Cada etapa foi analisada de forma independente por dois revisores, com auxílio de um terceiro revisor em caso de discordâncias. Foram escolhidos 3 estudos para revisão, num total de 751 artigos identificados, após uma pesquisa realizada até 19 de abril de 2022. Um estudo, classificado com adequada qualidade metodológica, demonstrou redução da concentração sérica do fator de necrose tumoral (TNF)-α em indivíduos com dor lombar crónica inespecífica após serem submetidos a tratamento manipulativo osteopático (TMO) (p = 0,03), reforçada pela diferença estatisticamente significativa na comparação entre os grupos experimental e controle (p = 0,04). Nos restantes dois estudos, não foi possível concluir sobre a sua aplicabilidade clínica, face à baixa qualidade metodológica. Num estudo obteve-se uma redução significativa no TNF-α sérico (p = 0,03), no entanto no segundo estudo considerado, os níveis basais de citocinas não diferiram significativamente entre os grupos. Embora seja sugerido um efeito do TMO na redução dos níveis séricos de TNF-α, os estudos incluídos não são conclusivos quanto à influência da intervenção osteopática sobre o sistema imunitário, considerando os dados laboratoriais de citocinas, sobretudo devido à qualidade metodológica propensa a vieses.
- MnFe2O4@CNT-N as novel electrochemical nanosensor for determination of caffeine, acetaminophen and ascorbic acidPublication . Fernandes, Diana M.; Silva, Nádia; Pereira, Clara; Moura, Cosme; Magalhães, Júlia M.C.S.; Bachiller-Baeza, Belén; Rodríguez-Ramos, Inmaculada; Guerrero-Ruiz, Antonio; Delerue-Matos, Cristina; Freire, CristinaFor the first time, a glassy carbon electrode (GCE) modified with novel N-doped carbon nanotubes (CNT-N) functionalized with MnFe2O4 nanoparticles (MnFe2O4@CNT-N) has been prepared and applied for the electrochemical determination of caffeine (CF), acetaminophen (AC) and ascorbic acid (AA). The electrochemical behaviour of CF, AC and AA on the bare GCE, CNT-N/GCE and MnFe2O4@CNT-N/GCE were carefully investigated using cyclic voltammetry (CV) and square-wave voltammetry (SWV). Compared to bare GCE and CNT-N modified electrode, the MnFe2O4@CNT-N modified electrode can remarkably improve the electrocatalytic activity towards the oxidation of CF, AC and AA with an increase in the anodic peak currents of 52%, 50% and 55%, respectively. Also, the SWV anodic peaks of these molecules could be distinguished from each other at the MnFe2O4@CNT-N modified electrode with enhanced oxidation currents. The linear response ranges for the square wave voltammetric determination of CF, AC and AA were 1.0 × 10−6 to 1.1 × 10−3 mol dm−3, 1.0 × 10−6 to 1.0 × 10−3 mol dm−3 and 2.0 × 10−6 to 1.0 × 10−4 mol dm−3 with detection limit (S/N = 3) of 0.83 × 10−6, 0.83 × 10−6 and 1.8 × 10−6 mol dm−3, respectively. The sensitivity values at the MnFe2O4@CNT-N/GCE for the individual determination of AC, AA and CF and in the presence of the other molecules showed that the quantification of AA and CF show no interferences from the other molecules; however, AA and CF interfered in the determination of AC, with the latter molecule showing the strongest interference. Nevertheless, the obtained results show that MnFe2O4@CNT-N composite material acted as an efficient electrochemical sensor towards the selected biomolecules.