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- Bioelectrical signal detection using conducting polymer electrodes and the displacement current methodPublication . Inácio, Pedro; Mestre, Ana L G; Medeiros, C.R.; Asgarifar, Sanaz; ELAMINE, Youssef; Canudo, Joana; Santos, João; Bragança, José; Morgado, Jorge; Biscarini, Fabio; Gomes, Henrique L.Conducting polymer electrodes based on poly (3, 4 ethylenedioxythiophene): polystyrene sulfonate were used to record electrophysiological signals from autonomous cardiac contractile cells present in embryoid bodies. Signal detection was carried out by measuring the displacement current across the polymer/electrolyte double-layer capacitance, and compared with voltage detection. While for relatively low capacitance electrodes, the voltage amplification provides higher signal quality, and for high capacitive electrodes, the displacement current method exhibits a higher signal-to-noise ratio. It is proposed that the displacement current method combined with high capacitive polymer-based electrodes is adequate to measure clusters of cells and whole organs. Our approach has a great potential in fundamental studies of drug discovery and safety pharmacology.
- Preliminary characterization of a Moroccan honey with a predominance of Bupleurum spinosum pollenPublication . ELAMINE, Youssef; S, Azza; Lyoussi, Badiaa; Antunes, Maria Dulce; Estevinho, Letícia M.; Anjos, Ofélia; Resende, Mafalda; Faleiro, Maria Leonor; Miguel, MariaHoney with Bupleurum spinosum (zandaz) as a main pollen source has not been the subject of previous detailed study. Therefore, twelve Moroccan samples of this honey were subjected to melissopalynological, physicochemical and microbiological quality characterization, as well as antioxidant activity assessment. From a quality point of view, almost all samples were within the limits established by Codex Alimentarius, and/or the European legislation. All samples presented predominance of B. spinosum pollen (more than 48%). Relatively high levels of trehalose (1.3-4.0 g/100 g) and melezitose (1.5-2.8 g/100 g) were detected. Those sugars, not common in monofloral honeys, could be used as an important factor to discriminate zandaz honey. Flavonoid content correlated positively with the honey color, melanoidin and polyphenol content, and negatively with the IC50 values of scavenging ABTS (2,2' - azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) free radicals, while proline amount correlated negatively with IC50 values of nitric oxide scavenging activity and chelating power. This correlation supports the use of anti-oxidant activities as important variables for PCA (principal component analysis). Both components explained 70% from the given data, and showed certain homogeneity upon analyzed samples independent of the region, suggesting the importance of B. spinosum nectar in the resulting honey characteristics.
- Zantaz honey “monoflorality”: Chemometric applied to the routinely assessed parametersPublication . ELAMINE, Youssef; Lyoussi, Badiâa; Anjos, Ofélia; Estevinho, Leticia M.; AAZZA, Smail; Carlier, Jorge; Costa, Maria Clara; Miguel, MariaThe comparison of Zantaz honey samples harvested in Morocco in two different years was performed through chemometric analysis of routinely assessed parameters. The objective was to study how the pollen profile of this newly reported honey shapes its physicochemical characteristics as well as to determine its monoflorality threshold, which has not yet been defined. The predominance of B. spinosum pollen was confirmed in the majority of samples reaching 45%, generally requested for monoflorality declaration. The principal component analysis (PCA) was used for clustering and variables correlations. Pollen qualitative and quantitative differences could discriminate the samples belonging to both seasons when combined with the sugar analysis (59.44%) better than the combination with physicochemical parameters (pH, acidity, ash content, electrical conductivity and color) (60.62%). Positive correlation between the presence of B. spinosum pollen and melanoidins, color, fructose, moisture, trehalose, melezitose, iron, manganese and calcium could be seen. Integrating all the parameters except the pollen data allowed distinguishing two groups with significant differences (P < 0.05) in B. spinosum representability (58 +/- 11.24% against 40 +/- 15.98%). This may suggest that 40% is the monoflorality threshold of the Moroccan Zantaz honey, although a confirmation with sensorial analysis is required.
- Extracellular electrophysiological measurements of cooperative signals in astrocytes populationsPublication . Mestre, Ana L. G.; INÁCIO, PEDRO; ELAMINE, Youssef; Asgarifar, Sanaz; Lourenco, Ana S.; Cristiano, Maria L. S.; Aguiar, Paulo; Medeiros, Maria C. R.; Araújo, Inês; Ventura, Joao; Gomes, Henrique L.Astrocytes are neuroglial cells that exhibit functional electrical properties sensitive to neuronal activity and capable of modulating neurotransmission. Thus, electrophysiological recordings of astroglial activity are very attractive to study the dynamics of glial signaling. This contribution reports on the use of ultra-sensitive planar electrodes combined with low noise and low frequency amplifiers that enable the detection of extracellular signals produced by primary cultures of astrocytes isolated from mouse cerebral cortex. Recorded activity is characterized by spontaneous bursts comprised of discrete signals with pronounced changes on the signal rate and amplitude. Weak and sporadic signals become synchronized and evolve with time to higher amplitude signals with a quasi-periodic behavior, revealing a cooperative signaling process. The methodology presented herewith enables the study of ionic fluctuations of population of cells, complementing the single cells observation by calcium imaging as well as by patch-clamp techniques.
- Electrical impedance spectroscopy for potassium content analysis and botanical origin identification of honeyPublication . Elamine, Youssef; INÁCIO, PEDRO; Miguel, Maria da Graça; Carlier, Jorge; Costa, Maria Clara; Estevinho, Leticia M.; Gomes, Henrique L.Minerals are reported to dominate the electrical properties of honey and indicate its botanical and geographical origins. In this study, Electrochemical Impedance Spectroscopy (EIS) was used to assess the relation between mineral elements, electrical properties and botanical origin using three honey varieties - Citrus sp., Eucalyptus sp., and Erica sp. These varieties are identified through pollen analysis and market labelling. Flame atomic absorption and emission spectroscopies were used to quantify the concentrations of eight elements (potassium, sodium, calcium, magnesium, manganese, zinc, copper, and iron). Among all the mineral elements, potassium showed a consistent correlation with impedance. The potassium estimation in honey and standard solutions (calibration curve) had similar sensitivities of 153.43 nF/mM and 132.68 nF/mM, respectively. Additionally, the analysis revealed that potassium dominates the mineral composition, with the other species present in minimal quantities. The EIS technique showed high sensitivity to potassium and other ionisable species, making it possible to classify the botanical origin of these three honey types. The EIS technique proved to be both time and cost effective, yielding a classification rate higher than that achieved by analysing mineral composition.