Ionic liquid-based electroactive materials: a novel approach for cardiac tissue engineering strategies.

Cardiac tissue regeneration strategies are increasingly taking advantage of electroactive scaffolds to actively recreate the tissue microenvironment. In this context, this work reports on advanced materials based on two different ionic liquids (ILs), 2-hydroxyethyl-trimethylammonium dihydrogen phosphate ([Ch][DHP]) and choline bis(trifluoromethylsulfonyl)imide ([Ch][TFSI]), combined with poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) for the development of ionic electroactive IL/polymer hybrid materials for cardiac tissue engineering (TE). The morphological, physico-chemical, thermal and electrical properties of the hybrid materials, as well as their potential use as scaffolds for cardiac TE applications, were evaluated. Besides inducing changes in surface topography, roughness and wettability of the composites, the incorporation of [Ch][DHP] and [Ch][TFSI] leads to the increase in surface (σsurface) and volume (σvolume) electrical conductivities. Furthermore, washing the hybrid samples with phosphate-buffered saline solution strongly decreases the σsurface, whereas σsurface and σvolume of the composites remain almost unaltered after exposure to ultraviolet sterilization treatment. Additionally, it is verified that the incorporation of IL influences the P(VDF-TrFE) microstructure and crystallization process, acting as a defect during its crystallization. Cytotoxicity assays revealed that hybrid films based on [Ch][DHP] alone are not cytotoxic. These films also support H9c2 myoblast cell adhesion and proliferation, demonstrating their suitability for cardiac TE strategies based on electroactive microenvironments.

Enhanced ionic conductivity in poly(vinylidene fluoride) electrospun separator membranes blended with different ionic liquids for lithium ion batteries.

Electrospun poly(vinylidene fluoride) (PVDF) fiber membranes doped with different ionic liquids (ILs) and sharing the same anion were produced and their potential as separator membranes for battery applications was evaluated. Different types of ILs containing the same anion, bis(trifluoromethylsulfonyl)imide [TFSI]-, were used with IL concentrations ranging between 0 and 15 wt% The morphology, microstructure, thermal and electrical properties (ionic conductivity and electrochemical window) of the membranes were evaluated. The presence of ILs in the PVDF polymer matrix influences the fiber diameter and the content of the polar ß phase within the polymer, as well as the degree of crystallinity. The thermal stability of the membranes decreases with the incorporation of IL. Impedance spectroscopy tests show a maximum ionic conductivity of 2.8 mS.cm-1 for 15% of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][TFSI]) at room temperature. The electrochemical stability of the samples ranges from 0.0 to 6.0 V. When evaluated as battery separator membranes in C-LiFePO4 half-cells, a maximum discharge capacity of 119 mAh.g-1 at C-rate was obtained for the PVDF membrane with 15% [Emim][TFSI], with a coulombic efficiency close to 100%. The results demonstrate that the produced electrospun membranes are suitable for applications as separators for lithium ion batteries (LIBs).

Poly(vinylidene) fluoride membranes coated by heparin/collagen layer-by-layer, smart biomimetic approaches for mesenchymal stem cell culture.

The use of piezoelectric materials in tissue engineering has grown considerably since inherent bone piezoelectricity was discovered. Combinations of piezoelectric polymers with magnetostrictive nanoparticles (MNP) can be used to magnetoelectrically stimulate cells by applying an external magnetic field which deforms the magnetostrictive nanoparticles in the polymer matrix, deforming the polymer itself, which varies the surface charge due to the piezoelectric effect. Poly(vinylidene) fluoride (PVDF) is the piezoelectric polymer with the largest piezoelectric coefficients, being a perfect candidate for osteogenic differentiation. As a first approach, in this paper, we propose PVDF membranes containing magnetostrictive nanoparticles and a biomimetic heparin/collagen layer-by-layer (LbL) coating for mesenchymal stem cell culture. PVDF membranes 20% (w/v) with and without cobalt ferrite oxide (PVDF-CFO) 10% (w/w) were produced by non-solvent induced phase separation (NIPS). These membranes were found to be asymmetric, with a smooth surface, crystallinity ranging from 65% to 61%, and an electroactive ß-phase content of 51.8% and 55.6% for PVDF and PVDF-CFO, respectively. Amine groups were grafted onto the membrane surface by an alkali treatment, confirmed by ninhydrin test and X-ray photoelectron spectroscopy (XPS), providing positive charges for the assembly of heparin/collagen layers by the LbL technique. Five layers of each polyelectrolyte were deposited, ending with collagen. Human mesenchymal stem cells (hMSC) were used to test cell response in a short-term culture (1, 3 and 7 days). Nucleus cell counting showed that LbL favored cell proliferation in PVDF-CFO over non-coated membranes.

Polymer-based actuators: back to the future.

Polymer-based actuators play a key role in the area of smart materials and devices, and for this reason different polymer-based actuators have appeared in recent years and are implemented in a broad range of fields, including biomedical, optical or electronics, among others. Although it is possible to find more types, they are mainly classified into two main groups according to their different working principles: electromechanical - with electrical to mechanical energy conversion - and magnetomechanical - with magnetic to mechanical energy conversion. The present work provides a comprehensive and critical review of the recent studies in this field. The operating principles, some representative designs, performance analyses and practical applications will be presented. The future development perspectives of this interesting field will be also discussed. Thus, the present work provides a comprehensive understanding of the effects reported in the past, introduces solutions to the present limitations and, back to the future, serves as a useful guidance for the design of new polymer-based actuators aiming to improve their output performances.

Human Mesenchymal Stem Cells Growth and Osteogenic Differentiation on Piezoelectric Poly(vinylidene fluoride) Microsphere Substrates.

The aim of this work was to determine the influence of the biomaterial environment on human mesenchymal stem cell (hMSC) fate when cultured in supports with varying topography. Poly(vinylidene fluoride) (PVDF) culture supports were prepared with structures ranging between 2D and 3D, based on PVDF films on which PVDF microspheres were deposited with varying surface density. Maintenance of multipotentiality when cultured in expansion medium was studied by flow cytometry monitoring the expression of characteristic hMSCs markers, and revealed that cells were losing their characteristic surface markers on these supports. Cell morphology was assessed by scanning electron microscopy (SEM). Alkaline phosphatase activity was also assessed after seven days of culture on expansion medium. On the other hand, osteoblastic differentiation was monitored while culturing in osteogenic medium after cells reached confluence. Osteocalcin immunocytochemistry and alizarin red assays were performed. We show that flow cytometry is a suitable technique for the study of the differentiation of hMSC seeded onto biomaterials, giving a quantitative reliable analysis of hMSC-associated markers. We also show that electrosprayed piezoelectric poly(vinylidene fluoride) is a suitable support for tissue engineering purposes, as hMSCs can proliferate, be viable and undergo osteogenic differentiation when chemically stimulated.

Kinetic study of thermal degradation of chitosan as a function of deacetylation degree.

Thermal degradation of chitosan with varying deacetylation degree (DD) ranging between 50 and 85% was analyzed by dynamic thermogravimetric analysis at different heating rates. The present study focused on the temperature range between 500 and 800K, above water evaporation. Thermal degradation showed a main degradation stage in this temperature interval with a second stage that appeared in the weight derivative curves as a shoulder in the high temperature side of the main peak with increasing intensity as the DD decreased. The Kissinger and isoconversional Ozawa-Flynn-Wall models were employed to evaluate the Ea of both thermal degradation processes. Different kinetic models were tested to computer simulate the thermogravimetric traces calculating the model parameters with a non-linear least squares fitting routine. The Sestack-Berggren model allowed reproducing accurately the overlapping of the two degradation mechanisms and calculating the mass fraction lost in each of them revealing the coupling between the two degradation mechanisms.

Processing and size range separation of pristine and magnetic poly(l-lactic acid) based microspheres for biomedical applications.

Biodegradable poly(l-lactic acid) (PLLA) and PLLA/CoFe2O4 magnetic microspheres with average sizes ranging between 0.16-3.9µm and 0.8-2.2µm, respectively, were obtained by an oil-in-water emulsion method using poly(vinyl alcohol) (PVA) solution as the emulsifier agent. The separation of the microspheres in different size ranges was then performed by centrifugation and the colloidal stability assessed at different pH values. Neat PLLA spheres are more stable in alkaline environments when compared to magnetic microspheres, both types being stable for pHs higher than 4, resulting in a colloidal suspension. On the other hand, in acidic environments the microspheres tend to form aggregates. The neat PLLA microspheres show a degree of crystallinity of 40% whereas the composite ones are nearly amorphous (17%). Finally, the biocompatibility was assessed by cell viability studies with MC3T3-E1 pre-osteoblast cells.

Central and peripheral fat body mass have a protective effect on osteopenia or osteoporosis in adults and elderly?

UNLABELLED: This cross-sectional study involves randomly selected men aged 50 to 99 years and postmenopausal women. Either central fat mass or peripheral fat mass were associated to osteoporosis or osteopenia independently from fat-free body mass and other confounding factors. INTRODUCTION: Obesity and osteoporosis are public health problems that probably share common pathophysiological mechanisms. The question if body fat mass, central or peripheral, is protective or harmful for osteoporosis or osteopenia is not completely resolved. This study aims to investigate the association between osteoporosis or osteopenia, and fat body mass (central and peripheral) independently from fat-free body mass, in men aged 50 to 99 years old and postmenopausal women randomly selected in the community. METHODS: This is a cross-sectional investigation with a random sample of registered population in Niterói Family Doctor Program (FDP), State of Rio de Janeiro, Brazil. Bone mineral density (BMD) and fat-free mass were assessed by dual X-ray absorptiometry (DXA). RESULTS: There was statistically significant bivariate association between bone loss with gender, age, skin color, alcohol consumption at risk dose, use of thiazide, fat-free body mass, and fat body mass (central and peripheral). In the multiple analysis of fat-free body mass, central and peripheral fat body mass showed an independent and protective effect on the presence of osteoporosis or osteopenia (p value <0.001). CONCLUSION: Since both obesity and osteoporosis are public health problems worldwide, strategies aimed at preventing both conditions should be encouraged during aging.

Optimization of culture conditions to improve Helicobacter pylori growth in Ham's F-12 medium by response surface methodology.

Helicobacter pylori is a gastroduodenal pathogen that colonizes the human stomach and is the causal agent of gastric diseases. From the clinical and epidemiological point of view, enhancing and improving the growth of this bacterium in liquid media is an important goal to achieve in order to allow the performance of accurate physiological studies. The aim of this work was to optimize three culture conditions that influence the growth of H. pylori in the defined medium Ham s F-12 supplemented with 5 percent fetal bovine serum by using response surface methodology as a statistical technique to obtain the optimal conditions. The factors studied in this experimental design (Box-Behnken design) were the pH of the medium, the shaking speed (rpm) and the percentage of atmospheric oxygen, in a total of 17 experiments. The biomass specific growth rate was the response measured. The model was validated for pH and shaking speed. The percentage of atmospheric oxygen did not influence the growth for the range of values studied. At the optimal values found for pH and shaking speed, 8 and 130 rpm, respectively, a specific growth rate value of 0.164 h-1, corresponding to a maximal concentration of approximately 1.5x108 CFU/ml, was reached after 8 h. The experimental design strategy allowed, for the first time, the optimization of H. pylori growth in a semi-synthetic medium, which may be important to improve physiological and metabolic studies of this fastidious bacterium.

Raw bovine meat fatty acids profile as an origin discriminator.

Consumers are very concerned in "Protected Designation of Origin" (PDO) products, namely meat, since they associate these products to quality and healthy foods. Thus, it is necessary to implement analytical methodologies that could assure consumers about the products they purchase. Since this kind of meat is usually sold with no information concerning cattle sex, age and slaughter season, these characteristics were intentionally not taken into account. In this study, two Portugueses PDO bovine breeds (Mirandesa and Barrosã) and two production sub-systems (traditional and organic farming) were studied during a two-year period. Statistical analysis showed that production system and breed had a significant effect on the overall raw meat fatty acids (FA) content. Besides, the FA profiles could be used as an effective tool to differentiate the four groups studied allowing a 100% correct classification. The meat FA content was also correlated with the relative importance of the animal feeding stuff area.

[Computerized electrocardiography system of Porto. I -- General description and experience with its use]. / O sistema do Porto de electrocardiografia computorizado. I--Descrição geral e experiência de Utilização.

After a brief review of computer assisted ECG interpretation techniques, a microcomputer-based system for off-line ECG (Frank) analysis and interpretation developed at the University of Porto is presented. The program is menu-structured and includes report correction and editing facilities. Clinical data can be stored along with the ECG in the individual patient file. More than 500 characteristics are extracted from the ECG signal by the measurement section of the program. The diagnostic section uses Boolean-tree logic. The diagnostic threshold values and interpretation statements are kept in an independent file and can be changed at any moment by the user. Taking the cardiologist using the same logic and criteria as reference standard, an evaluation of the diagnostic efficiency of the system was performed in 509 reports from pediatric and adult patients: 7% of the reports needed corrections and 113 (3.7%) out of 3070 diagnostic statements produced had to be changed. Output options include the clinical data, more or less extensive listings of the wave measurements, X, Y and Z and polar plots and the 12-lead (derived) ECG, besides the interpretation report itself.

A new ECG classification system for myocardial infarction based on receiver operating characteristic curve analysis and information theory.

An optimized three-lead ECG hierarchial decision-tree type of classification system for myocardial infarction is presented. For selection of the best threshold values for each criterion and the best association of features, we developed a procedure based on "receiver operating characteristic" (ROC) curve data analysis and information theory. Optimization was obtained through maximization of information content of the criteria. The classifier is based on nine measurements that can be easily obtained by hand (QX duration, Q/R Y amplitude, R Y amplitude, Q/R Y duration, Q Z amplitude, QRS and T axes in the horizontal plane, Q Z duration and R Z amplitude) and achieved a satisfactory performance in an independent group of patients (true-positive ratio 0.853, false-positive ratio 0.105, average information content 0.308 bits).