Seawater activated TiO2 photocatalyst for degradation of organic compounds

The world's oceans are polluted by a continuous inflow of plastic. Plastic fragments finally into microplastic, which can be taken up, for example by plankton, and subsequently by the entire ocean food web. An approach to reduce plastic pollution constitutes the accelerated microplastic degradation in marine environments. TiO₂ (anatase) is commonly used as an oxidative photocatalyst and well known to catalyze the degradation of organic compounds upon UV irradiation.In this study, a selective activation of TiO₂ (anatase) particles encapsulated by Ca- or Sr-polyphosphate is presented. The TiO₂ polyphosphate core-shell particles are envisaged as additives in plastic products. The highly concentrated cations from seawater, viz. Na⁺ and Mg²⁺, displace the Ca²⁺ or Sr²⁺ cations from the polyphosphate shell. As a result, the polyphosphate coating dissolves and thus the photocatalytically active TiO₂ core is released. The stability of the TiO₂ polyphosphate particles in potable water and the seawater activated disintegration of methylene blue, methyl methacrylate, terephtalic acid, and poly(vinyl alcohol) was shown. It has been demonstrated, that the sweetwater stable polyphosphate coating degrades in the presence of seawater, which could be monitored by the activation of the TiO₂ (anatase) photocatalyst.     

Guanidinylated block copolymers for gene transfer: A comparison with amine-based materials for in vitro and in vivo gene transfer efficiency

There is currently no cure for neuron loss in the brain, which can occur due to traumatic injury or neurodegenerative disease. One proposed method to enhance brain neurogenesis is gene transfer to neural progenitor cells. In this work, a guanidine-based copolymer was synthesized and compared to an amine-based copolymer analog previously shown to effectively deliver genes in the murine brain. The guanidine-based copolymer was more efficient at gene transfer to immortalized, cultured cell lines; however, the amine-based copolymer was more effective at gene transfer in the brain. DNA condensation studies revealed that the nucleic acid complexes formed with the guanidine-based copolymer were more susceptible to unpackaging in the presence of anionic proteoglycans compared to complexes formed with the amine-based copolymer. Therefore, polyplexes formed from the amine-based copolymer may be more resistant to destabilization by the heparan sulfate proteoglycans present in the stem cell niches of the brain.     

In-situ resistance measurements of Nafion® 117 membranes in polymer electrolyte fuel cells

The resistance of the Nafion® 117 membrane in $\text{H}{}_2\text{O}{}_2$ and $\text{H}{}_2\text{air}$ polymer electrolyte fuel cells (PEFCs) has been measured in situ using fast current pulses. The dependence of the membrane resistance on current density, temperature, pressure and flow-field design was investigated. It was found that, independent of other variations, the resistance increases with increasing current density. When the current density in the cell is increased from 0.2 to 0.7 A cm^?2, the membrane resistance increases by up to 22%. Even on open circuit the resistance at 60°C is 15%–35% higher than that measured ex situ, indicating that the membrane is not fully hydrated under the fuel cell operating conditions. The resistance on open circuit also depends on the design of the flow field. In a design with forced gas convection the resistance at 60°C is substantially higher (210 mΩ cm²) than in a design without forced convection (186 mΩ cm²).     

Nitrite reduction in acidic solution at a GC/Eastman-AQ-Os(bpy)32+-PVP composite modified electrode

The negatively charged polymer polyester sulfonic acid (Eastman-AQ, abbreviated to AQ), positively charged polymer polyvinyl pyridine (PVP) and mediator Os(bpy)₃²⁺ were used to construct composite modified glassy carbon (GC) electrodes (abbreviated to GC/AQ-Os(bpy)₃²⁺-PVP). The reduction of NO₂^? in acidic solution was taken as a model reaction to explore the properties of the modified electrode. On the steady state polarization curve of NO₂^? reduction there were two well-developed waves with much enhanced plateau current densities and positively shifted half-wave potentials compared with bare GC electrodes. In 0.05 mol/l H₂SO₄ + 5 mmol/l NO₂^? the modified electrode exhibited plateau current densities of 723 and 1153 μA cm^?2 and half-wave potential shifts of 0.29 and 0.56 V for the first and second current wave, respectively, showing promising potential for nitrite detection. The catalytic activity for NO₂^? reduction did not decrease appreciably over 4 months. A number of relevant kinetic and thermodynamic parameters are estimated experimentally. NO₂^? reduction at the composite modified electrodes is suggested to follow the SR mechanism (pure kinetic conditions involving mutual compensation between a catalytic reaction and substrate diffusion in the film in addition to diffusion in the solution phase) according to the Savéant–Andrieux theory.     

Compact poly-pyrrole layers formed at a liquid|liquid interface

Polymerization of surface active derivatives of pyrrole at the water|1,2-dichloroethane interface leads to the formation of a compact layer. New monomers have been synthesized with two pyrrole units in the molecule. Polymerization of these monomers proceeds at a lower potential and the density of the polymer layer is higher compared with monomers with one pyrrole unit in the molecule. Formation of the polymer layer has been monitored by cyclic voltammetry in the presence of transferable ions of different size and charge. Permeability of the polymer layer can be affected by the presence of a surface active derivative of cyclodextrin in the polymerization process.     

Comparison of incidence of complications and aesthetic performance for posterior metal-free polymer crowns and metal–ceramic crowns: Results from a randomized clinical trial

Objectives

The purpose of this randomized clinical study was to evaluate the clinical performance of posterior, metal-free polymer crowns after follow-up for up to six years, and to compare it with the performance of metal–ceramic crowns.

Methods

Eighty single crowns, manufactured from a polymer composite resin, were set on posterior teeth. Half of these received a glass–fibre framework (group 1) whereas half were prepared without framework stabilization (group 2). As the control group, 40 conventional metal–ceramic crowns were inserted. Primary endpoints were incidence of complications, investigated on a time-to-event basis, plaque status, and aesthetic performance.

Results

Thirty clinically relevant complications occurred after a median time of 2.3 years. Median follow-up time was four years. The most frequent complications were delamination (n = 24) and root-canal treatment (n = 4) of the crowns; the incidence of complications was not significantly different among crown materials (p = 0.60). Twenty crowns had to be replaced (six polymer crowns in group 1, nine polymer crowns in group 2, four crowns in the control group, and one tooth (in group 1) had to be extracted). Mean plaque and gingival indexes for the test groups did not differ from those for the control group.

Conclusions

Within a median follow-up period of four years, the clinical performance of posterior polymer crowns with and without a glass–fibre framework was not significantly different from that of metal–ceramic crowns, although the number of catastrophic failures of composite crowns was higher than that of the metal–ceramic crowns.

Clinical significance

On the basis of the study results, posterior polymer crowns may be an alternative to metal–ceramic crowns, although additional research is needed before they can be recommended, without reservation, as permanent restorations.     

Microtopography and Soft Tissue Response

Implants placed in soft tissue evoke a foreign body reaction. Polymeric implants having smooth surfaces, such as silicone rubber implants, develop a nonadherent fibrogranulous tissue capsule which contracts over time and stiffens. Conventional porous implants, such as those made from textiles, usually have pores larger than 20 μm and they become infiltrated with inflammatory tissue. The in vivo cell reaction to polymeric surfaces having pores smaller than 10 μm has not been investigated systematically. In this study the histocompatibility of materials having mean pore diameters from 0.4 to 10 μm was assessed. A material available with several different defined pore sizes Versapor filter material) was tested in vivo to determine relation between pore size and qualitative tissue response. Silicone-coated samples were also tested to determine the dependence of the observed tissue response on the implant surface chemistry. Results showed nonadherent, contracting capsules around implants having pore diameters smaller than 0.5 μm. Implants with pores ranging from 1.4 to 1.9 μm evoked thin, tightly adherent fibrous capsules without inflammatory cells. Porosities of 3.3 μm and larger became infiltrated with inflammatory tissue. Results indicate that the obsexrved tissue response is predominantly dependent on implant surface topography and that variation in implant material may have little effect. It is concluded that a defined surface topography of 1 to 2 pm appears to allow direct fibroblast attachment to the surface independent of its chemical or electrochemical nature. Attached fibro-blasts then produce a minimal connective tissue response to the implant and prevent or diminish the presence of inflammatory cells at the implant/tissue interface.     

Physicochemical properties of tadalafil solid dispersions – Impact of polymer on the apparent solubility and dissolution rate of tadalafil

To improve solubility of tadalafil (Td), a poorly soluble drug substance (3 μg/ml) belonging to the II class of the Biopharmaceutical Classification System, its six different solid dispersions (1:1, w/w) in the following polymers: HPMC, MC, PVP, PVP-VA, Kollicoat IR and Soluplus were successfully produced by freeze-drying. Scanning electron microscopy showed a morphological structure of solid dispersions typical of lyophilisates. Apparent solubility and intrinsic dissolution rate studies revealed the greatest, a 16-fold, increase in drug solubility (50 μg/ml) and a significant, 20-fold, dissolution rate enhancement for the Td/PVP-VA solid dispersion in comparison with crystalline Td. However, the longest duration of the supersaturation state in water (27 μg/ml) over 24 h was observed for the Td solid dispersion in HPMC. The improved dissolution of Td from Td/PVP-VA was confirmed in the standard dissolution test of capsules filled with solid dispersions. Powder X-ray diffraction and thermal analysis showed the amorphous nature of these binary systems and indicated the existence of dispersion at the molecular level and its supersaturated character, respectively. Nevertheless, as evidenced by film casting, the greatest ability to dissolve Td in polymer was determined for PVP-VA. The crystallization tendency of Td dispersed in Kollicoat IR could be explained by the low T_g (113 °C) of the solid dispersion and the highest difference in Hansen solubility parameters (6.8 MPa^0.5) between Td and the polymer, although this relationship was not satisfied for the partially crystalline dispersion in PVP. Similarly, no correlation was found between the strength of hydrogen bonds investigated using infrared spectroscopy and the physical stability of solid dispersions or the level of supersaturation in aqueous solution.     

水中邻苯二甲酸酯吸附材料的研究进展

邻苯二甲酸酯(PAEs)被广泛应用于食品包装、玩具和医疗产品,以改善其塑性和弹性。PAEs易于向水体中迁移,并因其具有内分泌干扰特性而成为目前最受公众关注的污染物之一。笔者总结了目前吸附法处理PAEs的最新研究和发展趋势,重点综述了各类吸附材料如活性炭、壳聚糖、人工合成树脂、粘土矿物材料对PAEs的吸附效能和机制,并在此基础上对吸附法处理PAEs的发展方向进行展望。     

Directing cell migration using micropatterned and dynamically adhesive polymer brushes

Micropatterning techniques, such as photolithography and microcontact printing, provide robust tools for controlling the adhesive interactions between cells and their extracellular environment. However, the ability to modify these interactions in real time and examine dynamic cellular responses remains a significant challenge. Here we describe a novel strategy to create dynamically adhesive, micropatterned substrates, which afford precise control of cell adhesion and migration over both space and time. Specific functionalization of micropatterned poly(ethylene glycol methacrylate) (POEGMA) brushes with synthetic peptides, containing the integrin-binding arginine–glycine–aspartic acid (RGD) motif, was achieved using thiol–yne coupling reactions. RGD activation of POEGMA brushes promoted fibroblast adhesion, spreading and migration into previously non-adhesive areas, and migration speed could be tuned by adjusting the surface ligand density. We propose that this technique is a robust strategy for creating dynamically adhesive biomaterial surfaces and a useful assay for studying cell migration.