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Electrochemical Multi-Sensors Device Coupled with Heurisic or Meta-Heuristic Selection Algorithms for Single-Cultivar Oilive Oil Classification

Publication . Peres, António M.; Veloso, Ana C.A.; Pereira, J.A.; Dias, L.G.

Apply heuristic and meta-heuristic variable selection algorithms. Best Approach? To reduce the number of sensors included in a linear discriminant analysis (LDA) model, avoiding the use of redundant information and multicollinearity problems To classify EVOOs according to cultivar and crop year. The Practical Aim: Improving the discrimination of EVOOs that are highly appreciated and an important componente of the Mediterranean diet, being prone to frauds involving mislabelling and adulteration.

2014Conference object

Open access

Development of an electrochemical RNA-aptasensor to detect human osteopontin

Publication . Meirinho, Sofia G.; Dias, L.G.; Peres, António M.; Rodrigues, Lígia R.

Electrochemical aptasensors may be used to detect protein biomarkers related to tumor activity. Osteopontin (OPN), a protein present in several body fluids, has been suggested as a potential biomarker since its overexpression seems to be associated with breast cancer progression and metastasis. In this work, a simple and label-free voltammetric aptasensor for the detection of OPN, using an RNA aptamer previously reported to have affinity for human OPN as the molecular recognition element, and the ferro/ferricyanide solution as a redox probe, was developed. The RNA aptamer was synthetized and immobilized in a working microelectrode gold surface (diameter of 0.8 mm) of a screen-printed strip with a silver pseudo-reference electrode and a gold counter electrode. The electrochemical behavior of the electrode surface after each preparation step of the aptasensor was studied using cyclic voltammetry and square wave voltammetry. The resulting voltammetric aptasensor was used to detect OPN in standard solutions. Cyclic voltammetry results showed that the aptasensor has reasonable detection and quantification limits(3.7+-0.6 nM and 11+-2 nM, respectively). Indeed, the detection limit falls within the osteopontin levels reported in the literature for patients with metastatic breast cancer. Moreover, the aptasensor is able to selectively detect the target protein in the presence of other interfering proteins, except for thrombin. Considering the overall results, a possible application of the aptasensor for cancer prognosis may be foreseen in a near future.

2015Journal article

Open access

In vitro anti-Candida activity of Glycyrrhiza glabra L.

Publication . Martins, Natália; Ferreira, Isabel C.F.R.; Henriques, Mariana; Silva, Sónia

The severity and frequency of opportunistic fungal infections still growing, concomitantly to the increasing rates of antimicrobial drug’s resistance. Natural matrices have been used over years due to its multitude of health benefits, including antifungal potential. Thus, the present work aims to evaluate the anti-Candida potential of the phenolic extract and individual phenolic compounds of Glycyrrhiza glabra L. (licorice), by disc diffusion assay, followed by determination of the minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) for both planktonic cells and biofilms. Licorice extract evidenced inhibitory potential against the nineteen tested Candida strains, but no pronounced effect was observed by testing the most abundant individual phenolic compounds. Candida tropicalis strains were the most sensible, followed by Candida glabrata, Candida parapsilosis and, then, Candida albicans. Lower MIC and MFC values were achieved to C. glabrata and C. tropicalis, which confirms its susceptibility to licorice extract; however, for C. tropicalis strains a higher variability was observed. Anti-biofilm potential was also achieved, being most evident in some C. glabrata and C. tropicalis strains. In general, a twice concentration of the MIC was necessary for planktonic cells to obtain a similar potential to that one observed for biofilms. Thus, an upcoming approach for new antifungal agents, more effective and safer than the current ones, is stablished; notwithstanding, further studies are necessary in order to understand its mechanism of action, as also to assess kinetic parameters.

2016Journal article

Open access

Electrochemical multi-sensors device coupled with heuristic or meta-heuristic selection algorithms for single-cultivar olive oil classification

Publication . Peres, António M.; Veloso, Ana C.A.; Pereira, J.A.; Dias, L.G.

Potentiometric electrochemical multi-sensors’ performance highly depends on the capability of selecting the best set of sensors. Indeed, signals are usually collinear resulting in over-fitted multivariate models with low predictive applicability. In this work, a comparative study was made to evaluate the predictive performance of classification models coupled with heuristic or metaheuristic variable selection algorithms. In this study, eleven single-cultivar extra virgin olive oils, from two crop years, were used. The results demonstrated that linear discriminant analysis with simulated annealing algorithm allowed selecting the best subset of sensors enabling 100% of correct cross-validation classifications, considering samples split by crop year.

2014Conference object

Open access

In vivo anti-Candida activity of phenolic extracts and compounds: future perspectives focusing on effective clinical interventions

Publication . Martins, Natália; Barros, Lillian; Henriques, Mariana; Silva, Sónia; Ferreira, Isabel C.F.R.

Candida species have increasingly deserved a special attention among the medical community. In spite of the presence of Candida species as a human commensal, alarming rates of local and systemic infections have been observed, varying from moderate to severe impact. Currently available antifungal drugs have progressively lost their effectiveness, pointing urgently the problem of the microorganisms with acquired-resistance. Natural matrices are secularly used for numerous purposes, being inclusive and highly effective as antimicrobials. Increasing evidence gives a particular emphasis to the contribution of phenolic extracts and related individual compounds. In vitro studies clearly confirm their prominent effects, but the confirmation through in vivo studies, including the involved mechanisms of action, is not so much deepened. Therefore, the present report aims to provide extensive knowledge about all these aspects, highlighting the most efficient phytochemical formulations, including therapeutic doses. Further studies need to be incited to deepen knowledge on this area, namely, focused on clinical trials to provide safer and more effective antimicrobials than the current ones.

2015Journal article

Open access