Reusable composite membranes for highly efficient chromium removal from real water matrixes

Natural or industrial hexavalent chromium water pollution continues to be a worldwide unresolved threat. Today, there is intense research on new active and cost-effective sorbents for Cr(VI), but most still exhibit a critical limitation: their powdered nature makes their recovery from water cost and energy consuming. In this work, Al(OH)₃, MIL-88-B(Fe), and UiO-66-NH₂ Cr(VI) sorbents were immobilized into a poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymeric substrate to develop an easily reactivable and reusable water filtering technology. The immobilization of the sorbents into the PVDF-HFP porous matrix modified the macro and meso-porous structure of the polymeric matrix, tuning in parallel its wettability. Although a partial blocking of the Cr(VI) adsorptive capacity was observed for of Al(OH)₃ and MIL-88-B(Fe) when immobilized into composite membranes, PVDF-HFP/UiO-66-NH₂ filter (i) exceeded the full capacity of the non-immobilized sorbent to trap Cr(VI), (ii) could be reactivated and reusable, and (iii) it was fully functional when applied in real water effluents.

Multifunctional hybrid membranes for photocatalytic and adsorptive removal of water contaminants of emerging concern

This work focuses on the combination of multifunctional photocatalytic and adsorbent materials in a unique polymeric membrane. For this purpose, Au/TiO₂ and Y₂(CO₃)₃ nanoparticles were immobilised onto a poly (vinylidene fluoride-hexafluoropropylene), (PVDF-HFP) membrane, and the physical-chemical characterisation of these materials was performed, as well as pollutant removal efficiency. An efficient TiO₂ functionalisation with gold nanoparticles was achieved, endowing these particles with the capability to absorb visible radiation absorption. A favourable porous structure was obtained for the membranes, with an average pore size of 4 μm, and the nanoparticles immobilisation did not alter the chemical properties of the polymeric membrane. The produced hybrid materials, including both the Au/TiO₂ and Y₂(CO₃)₃ nanoparticles, presented an efficiency of 57% in the degradation of norfloxacin (5 mg/L) under ultraviolet radiation for 120 min, 80% under visible radiation for 300 min, and 58% in arsenic adsorption for 240 min. These membranes represent a new multifunctional platform for removing several pollutants, which may allow their incorporation in more efficient and less energy-consuming water treatment processes favouring its application, even in low energy resources countries.

Photocatalytic and antimicrobial multifunctional nanocomposite membranes for emerging pollutants water treatment applications

Emerging pollutants represent a new global problem for water quality. As these compounds get into the environment, they cause severe threats to aquatic environments and human health and are typically resistant to conventional wastewater treatments. In this work, TiO₂ nanoparticles surface was functionalized with silver (Ag) nanoparticles, and solvent cast and electrospun membranes of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) were prepared with different concentrations of TiO₂ and Ag-TiO₂ to produce a multifunctional material. The photocatalytic activity of the nanocomposites was evaluated through the degradation of norfloxacin under ultraviolet (UV) and visible radiation. It is shown that nanocomposites with Ag-TiO₂ show the highest degradation efficiencies: 64.2% under UV and 80.7% under visible radiation, for 90 and 300 min, respectively. Furthermore, the recyclability of the membranes has also been demonstrated. Finally, it is shown the antimicrobial activity of the nanocomposite membranes, demonstrating the suitability of the Ag-TiO₂/PVDF-HFP nanocomposites as multifunctional photocatalytic and antimicrobial membranes for water remediation applications.

Deleterious effects of tributyltin on porcine vascular stem cells physiology

The vascular functional and structural integrity is essential for the maintenance of the whole organism and it has been demonstrated that different types of vascular progenitor cells resident in the vessel wall play an important role in this process. The purpose of the present research was to observe the effect of tributyltin (TBT), a risk factor for vascular disorders, on porcine Aortic Vascular Precursor Cells (pAVPCs) in term of cytotoxicity, gene expression profile, functionality and differentiation potential. We have demonstrated that pAVPCs morphology deeply changed following TBT treatment. After 48h a cytotoxic effect has been detected and Annexin binding assay demonstrated that TBT induced apoptosis. The transcriptional profile of characteristic pericyte markers has been altered: TBT 10nM substantially induced alpha-SMA, while, TBT 500nM determined a significant reduction of all pericyte markers. IL-6 protein detected in the medium of pAVPCs treated with TBT at both doses studied and with a dose response. TBT has interfered with normal pAVPC functionality preventing their ability to support a capillary-like network. In addition TBT has determined an increase of pAVPC adipogenic differentiation. In conclusion in the present paper we have demonstrated that TBT alters the vascular stem cells in terms of structure, functionality and differentiating capability, therefore effects of TBT in blood should be deeply explored to understand the potential vascular risk associated with the alteration of vascular stem cell physiology.

Comparative efficiency of TiO2 nanoparticles in suspension vs. immobilization into P(VDF–TrFE) porous membranes

Optimized photocatalytic membranes based on TiO₂ and NaY immobilized into P(VDF–TrFE) have been developed showing a degradation efficiency of 96%.

Effect of tributyltin on mammalian endothelial cell integrity

Tributyltin (TBT), is a man-made pollutants, known to accumulate along the food chain, acting as an endocrine disruptor in marine organisms, with toxic and adverse effects in many tissues including vascular system. Based on the absence of specific studies of TBT effects on endothelial cells, we aimed to evaluate the toxicity of TBT on primary culture of porcine aortic endothelial cells (pAECs), pig being an excellent model to study human cardiovascular disease. pAECs were exposed for 24h to TBT (100, 250, 500, 750 and 1000nM) showing a dose dependent decrease in cell viability through both apoptosis and necrosis. Moreover the ability of TBT (100 and 500nM) to influence endothelial gene expression was investigated at 1, 7 and 15h of treatment. Gene expression of tight junction molecules, occludin (OCLN) and tight junction protein-1 (ZO-1) was reduced while monocyte adhesion and adhesion molecules ICAM-1 and VCAM-1 (intercellular adhesion molecule-1 and vascular cell adhesion molecule-1) levels increased significantly at 1h. IL-6 and estrogen receptors 1 and 2 (ESR-1 and ESR-2) mRNAs, after a transient decrease, reached the maximum levels after 15h of exposure. Finally, we demonstrated that TBT altered endothelial functionality greatly increasing monocyte adhesion. These findings indicate that TBT deeply alters endothelial profile, disrupting their structure and interfering with their ability to interact with molecules and other cells.

Novel Anisotropic Magnetoelectric Effect on δ-FeO(OH)/P(VDF-TrFE) Multiferroic Composites

The past decade has witnessed increased research effort on multiphase magnetoelectric (ME) composites. In this scope, this paper presents the application of novel materials for the development of anisotropic magnetoelectric sensors based on δ-FeO(OH)/P(VDF-TrFE) composites. The composite is able to precisely determine the amplitude and direction of the magnetic field. A new ME effect is reported in this study, as it emerges from the magnetic rotation of the δ-FeO(OH) nanosheets inside the piezoelectric P(VDF-TrFE) polymer matrix. δ-FeO(OH)/P(VDF-TrFE) composites with 1, 5, 10, and 20 δ-FeO(OH) filler weight percentage in three δ-FeO(OH) alignment states (random, transversal, and longitudinal) have been developed. Results have shown that the modulus of the piezoelectric response (10-24 pC·N(-1)) is stable at least up to three months, the shape and magnetization maximum value (3 emu·g(-1)) is dependent on δ-FeO(OH) content, and the obtained ME voltage coefficient, with a maximum of ∼0.4 mV·cm(-1)·Oe(-1), is dependent on the incident magnetic field direction and intensity. In this way, the produced materials are suitable for innovative anisotropic sensor and actuator applications.

Magnetoelectric CoFe2O4/polyvinylidene fluoride electrospun nanofibres

Magnetoelectric 0-1 composites comprising CoFe2O4 (CFO) nanoparticles in a polyvinylidene fluoride (PVDF) polymer-fibre matrix have been prepared by electrospinning. The average diameter of the electrospun composite fibres is ∼325 nm, independent of the nanoparticle content, and the amount of the crystalline polar β phase is strongly enhanced when compared to pure PVDF polymer fibres. The piezoelectric response of these electroactive nanofibres is modified by an applied magnetic field, thus evidencing the magnetoelectric character of the CFO/PVDF 0-1 composites.

Development of magnetoelectric CoFe2O4 /poly(vinylidene fluoride) microspheres

Magnetoelectric microspheres based on piezoelectric poly(vinylidene fluoride) (PVDF) and magnetostrictive CoFe₂O₄ (CFO), a novel morphology for polymer-based ME materials, have been developed by an electrospray process.

Electrosprayed poly(vinylidene fluoride) microparticles for tissue engineering applications

Poly(vinylidene fluoride) microparticles with diameters between 0.80 and 5.50 μm were produced. Cell viability shows their suitability for tissue engineering.

Biodegradation assessment of PLA and its nanocomposites

Poly(lactic acid) nanocomposites containing Cloisite 15A, Cloisite 30B, and Dellite 43B were prepared by melt-mixing in a batch mixer and were exposed to UV radiation, temperature, and microorganism in solution and in a compost. Exposed samples, collected along the time, were characterized by several techniques. While the addition of organoclays had a positive effect on thermal stability, the degradation rate of nanocomposites increased when exposed to UV radiation and microorganism. Moreover, the degradation rate depends on the organoclay type. Even though the degradation rate is higher for nanocomposites, Fourier transform infrared spectrometry and gel permeation chromatography results demonstrated that the degradation mechanism is the same.

Evaluation of Properties and Biodeterioration Potential of Polyethylene and Aliphatic Polyester Blends

Blends of high density polyethylene (HDPE) and biodegradable polymers – polylactic acid, PLA, poly(∊-caprolactone), PCL and Mater-Bi® (thermoplastic starch (TPS) with PLA or PCL) – were prepared in a co-rotating twin-screw extruder, together with polyethylene modified with maleic anhydride (PE-g-MA) used as compatibiliser. The mechanical and rheological properties, morphology and potential for biodeterioration of polymeric materials were evaluated. Blends with PLA showed a reduced elongation at break but an increased Young's modulus while the addition of PCL led to materials with a greater elongation at break and a lower Young modulus. The rheological results evidenced that HPDE and the blend with the highest TPS level exhibited the highest viscosity. The microbial growth test carried out to evaluate the potential for biodeterioration of the blends, using a pure culture of Pseudomonas fluorescens, indicated that HDPE/PCL had a lower resistance to bacterial attack than the blend of HDPE/PLA. This was verified by a higher cell number on its surface after 10 weeks of incubation. The addition of 30% starch to the HDPE/PLA blend enhanced its biodeterioration potential, the same was not observed in the case of the HDPE/PCL blend containing just 18% starch.

Effect of zeolite content in the electrical, mechanical and thermal degradation response of poly(vinylidene fluoride)/NaY zeolite composites

Polymer based composites of a-PVDF doped with different NaY zeolite (Na53Al53Si139O384) content were investigated. A good dispersion of NaY zeolite within the polymer matrix is achieved. The introduction of NaY nanoparticles enhance the storage modulus and the dielectric constant at room temperature. The dielectric constant at room temperature increases up to the value of 500 for the 32 wt% composite, at 1 kHz. The increase of the dielectric constant is mainly attributed to interfacial polarization effects. For increasing zeolite content, the nanocomposite conductivity shows two conducting regimes separted by the so called breaking voltage, which is associated to an intrazeolite charge transport. Thermogravimetric results show that the introduction of zeolites affects the thermal degradation of the polymer for low zeolite contents and also indicate the presence of water that also plays an important role in the electrical response of the materials.

Jarisch-Herxheimer reaction among syphilis patients in Rio de Janeiro, Brazil

The Jarisch-Herxheimer reaction (JHR) is a syndrome observed after antimicrobial treatment of some infectious diseases. The syndrome has clinical characteristics of an inflammatory reaction to antibiotic treatment. A prospective study of patients with a clinical and laboratory diagnosis of syphilis was conducted at a sexually transmitted diseases clinic in Rio de Janeiro, Brazil. Patients were treated with benzathine penicillin and observed for the JHR. A total of 115 patients were included in this study. Fifty-one patients (44%) had secondary syphilis; 37 (32%), primary; 26 (23%), latent; and one (1%), tertiary syphilis. Ten patients (9%) developed the JHR. All JHRs occurred in patients with secondary and latent syphilis. No patients experienced an allergic reaction to penicillin. The JHR occurred less frequently than in previous studies. It is important that health-care professionals recognize the clinical characteristics of the JHR so that it is not misinterpreted as an allergic reaction to penicillin.

Bilateral diskoid medial menisci diagnosed by magnetic resonance imaging: a case report

A diskoid medial meniscus is a rare finding occurring in approximately 0.3% of the general population. Bilateral medial diskoid menisci are even less common, with only three other cases appearing in the literature. This may be the first reported case of bilateral medial diskoid menisci diagnosed by magnetic resonance imaging and verified at arthroscopy.