Gd2O3: Eu Nanoparticle-Based Poly(vinylidene fluoride) Composites for Indirect X-ray Detection

Polymer based scintillator composites have been fabricated by combining poly(vinylidene fluoride) (PVDF) and Gd2O3:Eu nanoparticles (50nm). PVDF has been used since it is a flexible and stable binder matrix and highly resistance to thermal and light deterioration. Gd2O3:Eu has been selected as scintillator material due to its wide band gap, high density and suitable visible light yield. The structural, mechanical, thermal and electrical characteristics of the composites were studied as a function of filler content, together with their performance as scintillator material. The introduction of Gd2O3:Eu nanoparticles into the PVDF matrix does not influence the morphology of the polymer or the degree of crystallinity. On the other hand, an increase of the Young´s modulus with respect to PVDF matrix is observed for filler contents of 0.1-0.75 wt.%. The introduction of Gd2O3:Eu into the PVDF matrix increases dielectric constant and DC electrical conductivity as well as the visible light yield in the nanocomposite, being this increase dependent upon Gd2O3:Eu content and X-ray input power. In this way, Gd2O3:Eu/PVDF composites shows suitable characteristics to be used as X-ray radiation transducers, in particular for large area applications.

Effect of ionic liquid anion type in the performance of solid polymer electrolytes based on Poly(Vinylidene fluoride-trifluoroethylene)

The effect of different anions within the ionic liquid in the characteristics of solid polymer electrolytes (SPEs) based on P(VDF-TrFE) has been investigated. 1-ethyl-3-methylimidazolium acetate, [C2mim][OAc], 1-ethyl-3-methylimidazolium triflate, [C2mim][(CF3SO3)3], 1-ethyl-3-methylimidazolium lactate, [C2mim][Lactate], 1-ethyl-3-methylimidazolium thiocyanate, [C2mim][SNC] and 1-ethyl-3-methylimidazolium hydrogen sulphate [C2mim][HSO4] have been used in SPE prepared by thermally induced phase separation (TIPS). The polymer phase, thermal and electrochemical properties of the SPE have been determined. The thermal and electrical properties of the SPEs strongly depend on the selected IL, as determined by their different interactions with the polymer matrix. The room temperature ionic conductivity increases in the following way for the different anions: [SNC] > [CF3SO3)3] > [HSO4] > [Lactate] > [OAc], which is mainly dependent on the viscosity of the ionic liquid.

Transcranial direct current stimulation based metaplasticity protocols in working memory

It has been already shown that delivering tDCS that are spaced by an interval alters its impact on motor plasticity. These effects can be explained, based on metaplasticity in which a previous modification of activity in a neuronal network can change the effects of subsequent interventions in the same network. But to date there is limited data assessing metaplasticity effects in cognitive functioning.

[Letter to the editor] Sustained effects of a neural-based intervention in a refractory case of Tourette syndrome

There are only a few treatments available for Tourette syndrome (TS). These treatments frequently do notwork in patients with moderate to severe TS [1]. Neuroimaging studies show a correlation between tics severity and increased activation over motor pathways, along with reduced activation over the control areas of the cortico-striato-thalamo-cortical circuits [2]. Moreover, the temporal pattern of tic generation suggests that cortical activation especially in the SMA precedes subcortical activation [3]. Following this assumption, here we explored the brain effects of 10-daily sessions of cathodal transcranial Direct Current Stimulation (tDCS) delivered over the pre-SMA in a patient with refractory and severe TS and also assessed whether those changes were long lasting (up to 6 months).

Metabolic profiling and classification of propolis samples from Southern Brazil: an NMR-based platform coupled with machine learning

The chemical composition of propolis is affected by environmental factors and harvest season, making it difficult to standardize its extracts for medicinal usage. By detecting a typical chemical profile associated with propolis from a specific production region or season, certain types of propolis may be used to obtain a specific pharmacological activity. In this study, propolis from three agroecological regions (plain, plateau, and highlands) from southern Brazil, collected over the four seasons of 2010, were investigated through a novel NMR-based metabolomics data analysis workflow. Chemometrics and machine learning algorithms (PLS-DA and RF), including methods to estimate variable importance in classification, were used in this study. The machine learning and feature selection methods permitted construction of models for propolis sample classification with high accuracy (>75%, reaching 90% in the best case), better discriminating samples regarding their collection seasons comparatively to the harvest regions. PLS-DA and RF allowed the identification of biomarkers for sample discrimination, expanding the set of discriminating features and adding relevant information for the identification of the class-determining metabolites. The NMR-based metabolomics analytical platform, coupled to bioinformatic tools, allowed characterization and classification of Brazilian propolis samples regarding the metabolite signature of important compounds, i.e., chemical fingerprint, harvest seasons, and production regions.

Racial inequalities in the socioeconomic, demographic and health conditions of elderly from Maranhão State, Legal Amazon, Brazil: a population-based study

Aging with quality of life does not occur equally among the racial groups of Brazilian elderly, and few studies have analyzed this issue in the states of the Brazilian Legal Amazon. The objective of this study was to investigate racial inequalities in the socioeconomic, demographic and health conditions of elderly residents of Maranhão state, Brazil. The present work is a cross-sectional study of 450 elders aged 60 years or older included in the 2008 National Household Sample Survey. The prevalence of socioeconomic, demographic, health and habit indicators and of risk factors were estimated in white, brown and black racial categories that were self-reported by the survey participants. The chi-square test was used for comparisons (a=5%). The majority of the elderly respondents identified themselves as brown (66.4%) or white (23.3%). There were significant socioeconomic, demographic, habit and lifestyle differences among the racial groups. Most of the black and brown elderly lived alone, reported lower educational levels and were in the lowest quintile for income. These respondents were also highly dependent on the Unified Health System (Sistema Único de Saúde - SUS), exhibited low rates of screening mammograms and lower physical activity levels and had a greater proportion of smokers. However, there was no difference in the prevalence of health indicators or in the proportion of elderly by gender, age, social role in the family or the urban-rural location of the household. These results indicate the presence of racial inequalities in the socioeconomic and demographic status and in the practice of healthy habits and lifestyles among elderly from Maranhão, but suggest equity in health status. The results also suggest the complexity and challenges of interlinking race with socioeconomic aspects, and the findings reinforce the need for the implementation of public policies for these population groups.

Development of elastin-like recombinamer films with antimicrobial activity

In the present work we explored the ABP-CM4 peptide properties from Bombyx mori for the creation of biopolymers with broad antimicrobial activity. An antimicrobial recombinant protein-based polymer (rPBP) was designed by cloning the DNA sequence coding for ABP-CM4 in frame with the N-terminus of the elastin-like recombinamer consisting of 200 repetitions of the pentamer VPAVG, here named A200. The new rPBP, named CM4-A200, was purified via a simplified nonchromatographic method, making use of the thermoresponsive behavior of the A200 polymer. ABP-CM4 peptide was also purified through the incorporation of a formic acid cleavage site between the peptide and the A200 sequence. In soluble state the antimicrobial activity of both CM4-A200 polymer and ABP-CM4 peptide was poorly effective. However, when the CM4-A200 polymer was processed into free-standing films high antimicrobial activity against Gram-positive and Gram-negative bacteria, yeasts and filamentous fungi was observed. The antimicrobial activity of CM4-A200 was dependent on the physical contact of cells with the film surface. Furthermore, CM4-A200 films did not reveal a cytotoxic effect against both normal human skin fibroblasts and human keratinocytes. Finally, we have developed an optimized ex vivo assay with pig skin demonstrating the antimicrobial properties of the CM4-A200 cast films for skin applications.

Poly lactic acid based biodegradable stents and functionalization techniques: brief review

Commercial stents, especially metallic ones, present several disadvantages, and this gives rise to the necessity of producing or coating stents with different materials, like natural polymers, in order to improve their biocompatibility and minimize the disadvantages of metallic ones. This review paper discusses some applications of natural-based polymers in stents, namely polylactic acid (PLA) for stent development and chitosan for biocompatible coatings of stents . Furthermore, some effective stent functionalization techniques will be discussed, namely Layer by Layer (LBL) technique.

Fluorescence-based approaches towards the assessment of structural and functional alterations in lysosomes and vacuoles induced by lactoferrin and acetic acid

Dissertação de mestrado em Biofísica e Bionanossistemas

The influence of nitrogen and oxygen additions on the thermal characteristics of aluminium-based thin films

The ternary aluminium oxynitride (AlNxOy) system offers the possibility to obtain a wide range of properties by tailoring the ratio between pure Al, AlNx and AlOy and therefore opening a significant number of possible applications. In this work the thermal behaviour of AlNxOy thin films was analysed by modulated infrared radiometry (MIRR), taking as reference the binary AlOy and AlNx systems. MIRR is a non-contact and non-destructive thermal wave measurement technique based on the excitation, propagation and detection of temperature oscillations of very small amplitudes. The intended change of the partial pressure of the reactive gas (N2 and/or O2) influenced the target condition and hence the deposition characteristics which, altogether, affected the composition and microstructure of the films. Based on the MIRR measurements and their qualitative and quantitative interpretation, some correlations between the thermal transport properties of the films and their chemical/physical properties have been found. Furthermore, the potential of such technique applied in this oxynitride system, which present a wide range of different physical responses, is also discussed. The experimental results obtained are consistent with those reported in previous works and show a high potential to fulfil the demands needed for the possible applications of the systems studied. They are clearly indicative of an adequate thermal response if this particular thin film system is aimed to be applied in small sensor devices or in electrodes for biosignal acquisition, such as those for electroencephalography or electromyography as it is the case of the main research area that is being developed in the group.

Personalized-based dietary recommendation for weightlifting

Dissertação de mestrado integrado em Engenharia Eletrónica Industrial e Computadores

Chitosan-based scaffolds for tissue regeneration: preparation and microstructure characterization

Scaffolds are porous three-dimensional supports, designed to mimic the extracellular environment and remain temporarily integrated into the host tissue while stimulating, at the molecular level, specific cellular responses to each type of body tissues. The major goal of the research work entertained herein was to study the microstructure of scaffolds made from chitosan (Ch), blends of chitosan and sodium alginate (Ch/NaAlg), blends of chitosan, sodium alginate and calcium chloride (Ch/NaAlg/CaCl2) and blends of chitosan, sodium alginate and hydroxyapatite (Ch/NaAlg/HA). Scaffolds possessing ideal physicochemical properties facilitate cell proliferation and greatly increase the rate of recovery of a damaged organ tissue. Using CT three-dimensional images of the scaffolds, it was observed that all scaffolds had a porosity in the range 64%-92%, a radius of maximum pore occurrence in the range 95m-260m and a permeability in the range 1×10-10-18×10-10 m2. From the results obtained, the scaffolds based on Ch, Ch/NaAlg and Ch/NaAlg/CaCl2 would be most appropriate both for the growth of osteoid and for bone tissue regeneration, while the scaffold made with a blend of Ch/NaAlg/HA, by possessing larger pores size, might be used as a support for fibrovascular tissue.

Delivery as nanoparticles reduces imatinib mesylate-induced cardiotoxicity and improves anticancer activity

Clinical effectiveness of imatinib mesylate in cancer treatment is compromised by its off-target cardiotoxicity. In the present study, we have developed physically stable imatinib mesylate-loaded poly(lactide-co-glycolide) nanoparticles (INPs) that could sustainably release the drug, and studied its efficacy by in vitro anticancer and in vivo cardiotoxicity assays. MTT (methylthiazolyldiphenyl-tetrazolium bromide) assay revealed that INPs are more cytotoxic to MCF-7 breast cancer cells compared to the equivalent concentration of free imatinib mesylate. Wistar rats orally administered with 50 mg/kg INPs for 28 days showed no significant cardiotoxicity or associated changes. Whereas, increased alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase levels, and reduced white blood cell, red blood cell, and hemoglobin content were observed in the animals administered with free drug. While the histological sections from hearts of animals that received INPs did not show any significant cardiotoxic symptoms, loss of normal architecture and increased cytoplasmic vacuolization were observed in the heart sections of animals administered with free imatinib mesylate. Based on these results, we conclude that nano-encapsulation of imatinib mesylate increases its efficacy against cancer cells, with almost no cardiotoxicity.

Development of advanced cell/tissue culture systems, based on enhanced polymeric scaffolds and sophisticated bioreactors, for tissue engineering applications

Programa Doutoral em Engenharia Biomédica

Systems biology approaches for the design of novel Saccharomyces cerevisiae winemaking strains for enhanced flavour compounds synthesis

Tese de Doutoramento em Biologia Ambiental e Molecular