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Athena Metaxas, Nikolas Wilkinson, Ellie Raethke, Cari S Dutcher
Flocculation of small particulates suspended in solution is a key process in many industries, including drinking water treatment. The particles are aggregated during mixing to form larger aggregates, known as flocs, through use of a polyelectrolyte flocculant. The flocculation of these particulates in water treatment, however, are subject to a wide spatial variation of hydrodynamic flow states, which has consequences for floc size, growth rate, and microstructure. Floc assembly dynamics are explored here using a commercially available cationic polyacrylamide, commonly used in water treatment, and anisotropic Na-bentonite clay particles under a variety of hydrodynamic mixing conditions...
October 17, 2018: Soft Matter
Sophia M Orbach, Andrew J Ford, Scott-Eugene Saverot, Padmavathy Rajagopalan
Hepatic fibrosis is the result of wound healing and inflammation resulting in organ dysfunction. Hepatocytes, liver sinusoidal endothelial cells (LSECs), Kupffer cells (KCs), and hepatic stellate cells (HSCs) play critical roles in fibrogenesis. As the liver undergoes fibrosis, there are populations of cells that are healthy, fibrotic as well as those undergoing fibrosis. We investigated how a varying mechanical environment could induce changes in hepatic cells. In this study, a gradient in the mechanical properties of the microenvironment resulted in transitioning phenotypes in hepatic cells...
October 10, 2018: Acta Biomaterialia
Nikita A Navolokin, Sergei V German, Alla B Bucharskaya, Olga S Godage, Viktor V Zuev, Galina N Maslyakova, Nikolaiy A Pyataev, Pavel S Zamyshliaev, Mikhail N Zharkov, Georgy S Terentyuk, Dmitry A Gorin, Gleb B Sukhorukov
Multilayer capsules of 4 microns in size made of biodegradable polymers and iron oxide magnetite nanoparticles have been injected intravenously into rats. The time-dependent microcapsule distribution in organs was investigated in vivo by magnetic resonance imaging (MRI) and ex vivo by histological examination (HE), atomic absorption spectroscopy (AAS) and electron spin resonance (ESR), as these methods provide information at different stages of microcapsule degradation. The following organs were collected: Kidney, liver, lung, and spleen through 15 min, 1 h, 4 h, 24 h, 14 days, and 30 days after intravenous injections (IVIs) of microcapsules in a saline buffer at a dosage of 2...
October 10, 2018: Nanomaterials
Qing-Hai Hao, Gang Xia, Hong-Ge Tan, Er-Qiang Chen, Shuang Yang
The surface morphologies of spherical polyelectrolyte brushes in salt solutions with opposite trivalent ions are studied using molecular dynamics (MD) simulations. The impact of salt concentration, grafting density, and charge fraction on brush morphologies is investigated systematically. A variety of surface patterns are predicted and the phase diagrams are presented. Both lateral and radial microphase separated structures in the brushes are observed upon varying the salt concentration. With low grafting density the spherical brush is separated into several patches, the number of which decreases with the addition of salt...
October 11, 2018: Physical Chemistry Chemical Physics: PCCP
Siu On Tung, Sydney L Fisher, Nicholas A Kotov, Levi T Thompson
Redox flow batteries are attractive for large-scale energy storage due to a combination of high theoretical efficiencies and decoupled power and energy storage capacities. Efforts to significantly increase energy densities by using nonaqueous electrolytes have been impeded by separators with low selectivities. Here, we report nanoporous separators based on aramid nanofibres, which are assembled using a scalable, low cost, spin-assisted layer-by-layer technique. The multilayer structure yields 5 ± 0.5 nm pores, enabling nanofiltration with high selectivity...
October 10, 2018: Nature Communications
Simona Giarra, Silvia Zappavigna, Virginia Campani, Marianna Abate, Alessia Maria Cossu, Carlo Leonetti, Manuela Porru, Laura Mayol, Michele Caraglia, Giuseppe De Rosa
This study aimed to develop nanovectors co-encapsulating doxorubicin (Doxo) and zoledronic acid (Zol) for a combined therapy against Doxo-resistant tumors. Chitosan (CHI)-based polyelectrolyte complexes (PECs) prepared by ionotropic gelation technique were proposed. The influence of some experimental parameters was evaluated in order to optimize the PECs in terms of size and polydispersity index (PI). PEC stability was studied by monitoring size and zeta potential over time. In vitro studies were carried out on wild-type and Doxo-resistant cell lines, to assess both the synergism between Doxo and Zol, as well as the restoring of Doxo sensitivity...
October 9, 2018: Pharmaceutics
Jingheng Ning, Xin Luo, Min Wang, Jiaojiao Li, Donglin Liu, Hou Rong, Donger Chen, Jianhui Wang
To ensure food quality and safety, developing cost-effective, rapid and precision analytical techniques for quantitative detection of nitrite is highly desirable. Herein, a novel electrochemical sensor based on the sodium cellulose sulfate/poly (dimethyl diallyl ammonium chloride) (NaCS/PDMDAAC) composite film modified glass carbon electrode (NaCS/PDMDAAC/GCE) was proposed toward the detection of nitrite at sub-micromolar level, aiming to make full use of the inherent properties of individual component (biocompatible, low cost, good electrical conductivity for PDMDAAC; non-toxic, abundant raw materials, good film forming ability for NaCS) and synergistic enhancement effect...
October 9, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Andrei Lipchinsky
One of the most challenging questions in cell and developmental biology is how molecular signals are translated into mechanical forces that ultimately drive cell growth and motility. Despite an impressive body of literature demonstrating the importance of cytoskeletal and motor proteins as well as osmotic stresses for cell developmental mechanics, a host of dissenting evidence strongly suggests that these factors per se cannot explain growth mechanics even at the level of a single tip-growing cell. The present study addresses this issue by exploring fundamental interrelations between electrical and mechanical fields operating in cells...
October 6, 2018: Bio Systems
Fumiyasu Seino, Yuichi Konosu, Minoru Ashizawa, Yuriko Kakihana, Mitsuru Higa, Hidetoshi Matsumoto
Poly(vinyl alcohol) (PVA)-based ion-exchange nanofibers (IEX-NFs) and their composite polyelectrolyte membranes were prepared and characterized. The PVA-based NFs are well dispersed and form a three-dimensional network structure in the polymer matrix, Nafion. All of the prepared membranes show a similar ion-exchange capacity of ∼1.0 mmol g-1 . The ionic conductivities through the PVA- b-PSS-NF/Nafion composite membranes are superior to that of the Nafion membranes, but the conductivity through the PVA-NF/Nafion composite membrane is half that of the Nafion membrane...
October 17, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Lukasz Poltorak, Mark L Verheijden, Duco Bosma, Pascal Jonkheijm, Louis C P M de Smet, Ernst J R Sudhölter
Silicon semiconductors with a thin surface layer of silica were first modified with polyelectrolytes (polyethyleneimine, polystyrene sulfonate and poly(allylamine)) via a facile layer-by-layer deposition approach. Subsequently, lipid vesicles were added to the preformed polymeric cushion, resulting in the adsorption of intact vesicles or fusion and lipid bilayer formation. To study involved interactions we employed optical reflectometry, electrochemical impedance spectroscopy and fluorescent recovery after photobleaching...
October 3, 2018: Biochimica et biophysica acta. Biomembranes
Roza Szweda, Michel Tschopp, Olivier Felix, Gero Decher, Jean-Francois Lutz
A library of 16 digitally-encoded polyanions was used in a layer-by-layer (LbL) polyelectrolyte assembly to nanofabricate thin-films containing digitally-coded strata. The polyanions were digital polyphosphodiesters (d-PPDE) prepared via an automated phosphoramidite process. Each component of the library contained 10 bytes of ASCII-encoded text (i.e. 80 coded monomers); thus the entire library allows the writing of a full sentence, which can be stored in a multilayer film as a sequence of sequences. The LbL assembly was performed on a polyethyleneimine-modified silicon wafer using poly(allylamine hydrochloride) (PAH) as a counter-polycation...
October 5, 2018: Angewandte Chemie
Ya Ching Chiu, Huan Jang Keh
The quasisteady diffusiophoresis of a charged porous sphere situated at the center of a charged spherical cavity filled with a liquid solution of a symmetric electrolyte is analyzed. The porous particle can represent a solvent-permeable and ion-penetrable polyelectrolyte molecule or floc of nanoparticles, in which fixed charges and frictional segments are uniformly distributed, while the spherical cavity can denote a charged pore involved in microfluidic or drug-delivery systems. The linearized electrokinetic differential equations governing the ionic concentration, electric potential, and fluid velocity distributions in the system are solved by using a perturbation method with the fixed charge density of the particle and the zeta potential of the cavity wall as the small perturbation parameters...
October 3, 2018: Journal of Physical Chemistry. B
Zhanwei Zhou, Qingyan Zhang, Minghua Zhang, Huipeng Li, Gang Chen, Chenggen Qian, David Oupicky, Minjie Sun
Stimuli-responsive polycations have been developed for improved nucleic acid transfection and enhanced therapeutic efficacy. The most reported mechanisms for controlled release of siRNA are based on polyelectrolyte exchange reactions in the cytoplasm and the degradation of polycations initiated by specific triggers. However, the degradation strategy has not always been sufficient due to unsatisfactory kinetics and binding of cationic fragments to siRNA, which limits the gene silencing effect. In this study, a new strategy that combines degradation and charge reversal is proposed...
2018: Theranostics
Md Shamim Iqbal, Wei Zhan
An electrochemical approach to surface deposition of polyelectrolytes on self-assembled monolayers is presented. This deposition process can be triggered facilely by a potential bias, which oxidizes ferrocene moieties included in the self-assembled monolayer to ferrocenium, whose charge compensation is fulfilled by polyelectrolytes and associated counterions. This approach is quite general, affording quantitative deposition of both polyanions and polycations with a wide range of chemical identities (synthetic polymers, peptides and DNA) and molecular weights (103 to 107 Da as tested)...
October 2, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Saumyak Mukherjee, Sayantan Mondal, Subhajit Acharya, Biman Bagchi
Experiments have revealed that DNA solvation dynamics is characterized by multiple time scales ranging from a few ps to a few hundred ns and in some cases even up to several microseconds. The last part of decay is not only slow but can also be described by a power law (PL). The microscopic origin of this PL is yet to be clearly established. Here we present a theoretical study employing multiple approaches from time dependent statistical mechanics and computer simulations. The present study shows that water dynamics may not account for the slow PL decay because the longest timescales describing water dynamics could be at most of the order of 100 ps...
October 2, 2018: Journal of Physical Chemistry. B
Michael L Davidson, Lynn M Walker
The transport, equilibrium properties and mechanics of stable, rod-like surfactant-polyelectrolyte aggregates, poly(vinyl benzoate)-cetyltrimethylammonium or pCTVB, are characterized at air/water interfaces for bulk concentrations near and below the critical aggregation concentration. The surfactant drives the transport to air/water interfaces, while the polyelectrolyte provides elasticity to the coated interfaces and appears to remain adsorbed after the bulk solution is exchanged with water. Processing of interfaces is shown to allow the interfacial tension of the interface to be changed significantly while maintaining a high dilatational elasticity...
October 1, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Cecilia Zorzi Bueno, Ângela Maria Moraes
This work is a continuation of a previous study which described the development of dense and porous chitosan-alginate polyelectrolyte complexes through the addition of different amounts of Pluronic F68 to the polymeric mixture. The present study consisted in the incorporation of an antimicrobial agent, polyhexamethylene biguanide (PHMB), to the previously developed system. PHMB was incorporated at 1 and 10% (w/w) with high incorporation efficiencies, varying from 72 to 86%. Release profiles in phosphate buffered saline were evaluated using the Korsmeyer-Peppas equation, which suggested a quasi-Fickian diffusion mechanism for all obtained formulations...
December 1, 2018: Materials Science & Engineering. C, Materials for Biological Applications
Ana Luiza R Pires, Liana de Azevedo Motta, Ana M A Dias, Hermínio C de Sousa, Ângela M Moraes, Mara E M Braga
This study aimed to evaluate the effect of poly(dimethylsiloxane) on the mechanical properties of chitosan-alginate (CA) polyelectrolyte complexes (PECs) with potential application as wound dressing biomaterials. For that purpose, different amounts of poly(dimethylsiloxane) were incorporated during the formulation of the PECs. Results showed that the highest tensile strength was observed when using 0.1 g of poly(dimethylsiloxane) per gram of PEC (CAS10). This formulation was also non-hemolytic, capable of inducing thrombus formation to potentially reduce bleeding, and additionally presented high stability when exposed to physiological fluids and/or conditions simulating patient bathing...
December 1, 2018: Materials Science & Engineering. C, Materials for Biological Applications
Hélène Labie, Adeline Perro, Véronique Lapeyre, Bertrand Goudeau, Bogdan Catargi, Rachel Auzély, Valérie Ravaine
A simple route to deliver on demand hydrosoluble molecules such as peptides, packaged in biocompatible and biodegradable microgels, is presented. Hyaluronic acid hydrogel particles with a controlled structure are prepared using a microfluidic approach. Their porosity and their rigidity can be tuned by changing the crosslinking density. These negatively-charged polyelectrolytes interact strongly with positively-charged linear peptides such as poly-l-lysine (PLL). Their interactions induce microgel deswelling and inhibit microgel enzymatic degradability by hyaluronidase...
September 15, 2018: Journal of Colloid and Interface Science
Seung-Woo Lee, Tae-Hyung Kang, Sung Ku Lee, Ki-Young Lee, Hyunjung Yi
Realizing high-performance electrochemical biosensors in a simple contact-printing-based approach significantly increases the applicability of integrated flexible biosensors. Herein, an enzyme-sticker-based approach that enables flexible and multi electrochemical sensors via simple contact-transfer-printing is reported. The enzyme sticker consists of an enzymatic conductive network film and a polymeric support. The enzyme-incorporated nanostructured conductive network showing efficient electrical coupling was assembled via hydrodynamic layer-by-layer assembly of redox enzymes, polyelectrolytes, single-walled carbon nanotubes and biological glue material, M13 phage...
September 27, 2018: ACS Applied Materials & Interfaces
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