Effect of the operating temperature on hydrodynamics and membrane parameters in pressure retarded osmosis

Producción CientíficaThe osmotic energy recovered by pressure-retarded osmosis from flows of different salinities is affected by the temperature, so its effect on hydrodynamic and membrane parameters is studied here. It is shown by models and experimental results that raising the temperature of the solutions leads to a variation in the mass transfer coefficient, the boundary layer, the diffusion coefficient, the solute resistivity, and the permeability, therefore, affecting the water flux. Consequently, the expected power density is improved at high temperatures, although, the salt flux diffusion increases. Laboratory results are presented using solutions at different concentrations and temperatures to validate the analysis.Funded by Mineco Project DPI2014-54530-R and FEDER fund

Endocytosis of dextran and silan-coated magnetite nanoparticles and the effect of intracellular hyperthermia on human mammary carcinoma cells in vitro

To obtain more evidence for intracellular magnetic fluid hyperthermia (MFH), endocytosis and hyperthermia efficacy of silan and dextran magnetite was investigated. Differential endocytosis was observed in dependence of nanoparticle and cell type. Clonogenic survival was 3-fold lower after MFH versus waterbath hyperthermia. The selective \u27remote inactivation\u27 of cancer cells by an AC magnetic field has been demonstrated in vitro

Endocytosis of dextran and silan-coated magnetite nanoparticles and the effect of intracellular hyperthermia on human mammary carcinoma cells in vitro

To obtain more evidence for intracellular magnetic fluid hyperthermia (MFH), endocytosis and hyperthermia efficacy of silan and dextran magnetite was investigated. Differential endocytosis was observed in dependence of nanoparticle and cell type. Clonogenic survival was 3-fold lower after MFH versus waterbath hyperthermia. The selective 'remote inactivation' of cancer cells by an AC magnetic field has been demonstrated in vitro

Acid catalyzed cross‐linking of polyvinyl alcohol for humidifier membranes

Polyvinyl alcohol (PVA) is a hydrophilic polymer well known for good film forming properties, high water vapor permeance JW, and low nitrogen permeance. However, depending on molar mass and temperature, PVA swells strongly in water until complete dissolution. This behavior affects the usability of PVA in aqueous environments and makes cross‐linking necessary if higher structural integrity is envisaged. In this work, PVA networks are formed by thermal cross‐linking in the presence of p‐toluenesulfonic acid (TSA) and investigated in a design of experiments approach. Experimental parameters are the cross‐linking period tc, temperature ϑ and the TSA mass fraction wTSA. Cross‐linking is found to proceed via ether bond formation at all reaction conditions. Degradation is promoted especially by a combination of high wTSA, tc and ϑ. Thermal stability of the networks after preparation is strongly improved by neutralizing residual TSA. Humidification membranes with a JW of 6423 ± 63.0 gas permeation units (GPU) are fabricated by coating PVA on polyvinyliden fluoride hollow fibers and cross‐linking with TSA. Summarizing, the present study contributes to a clearer insight into the cross‐linking of PVA in presence of TSA, the thermal stability of the resulting networks and the applicability as selective membrane layers for water vapor transfer.Bundesministerium für Wirtschaft und EnergieProjekt DEA

A nonviral DNA delivery system based on surface modified silica-nanoparticles can efficiently transfect cells in vitro

Diverse polycationic polymers have been used as nonviral transfection agents. Here we report the ability of colloidal silica particles with covalently attached cationic surface modifications to transfect plasmid DNA in vitro and make an attempt to describe the structure of the resulting transfection complexes. In analogy to the terms lipoplex and polyplex, we propose to describe the nanoparticle-DNA complexes by the term 'nanoplex'. Three batches, Si10E, Si100E, and Si26H, sized between 10 and 100 nm and with ζ potentials ranging from +7 to +31 mV at pH 7.4 were evaluated. The galactosidase expression plasmid DNA pCMVβ was immobilized on the particle surface and efficiently transfected Cos-1 cells. The transfection activity was accompanied by very low cytotoxicity, with LD50 values in the milligrams per milliliter range. The most active batch, Si26H, was produced by modification of commercially available silica particles with N-(6-aminohexyl)-3-aminopropyltrimethoxysilane, yielding spherical nanoparticles with a mean diameter of 26 nm and a ζ potential of +31 mV at pH 7.4. Complexes of Si26H and pCMVβ plasmid DNA formed at w/w ratios of 10 were most effective in promoting transfection of Cos-1 cells in the absence of serum. At this ratio, >90% of the DNA was associated with the particles, yielding nanoplexes with a net negative surface charge. When the transfection medium was supplemented with 10% serum, maximum gene expression was observed at a w/w ratio of 30, at which the resulting particle-DNA complexes possessed a positive surface charge. Transfection was strongly increased in the presence of 100 µM chloroquine in the incubation medium and reached approximately 30% of the efficiency of a 60 kDa polyethylenimine. In contrast to polyethylenimine, no toxicity was observed at the concentrations required. Atomic force microscopy of Si26H-DNA complexes revealed a spaghetti-meatball-like structure. The surface of complexes prepared at a w/w ratio of 30 was dominated by particles half-spheres. Complex sizes correlated well with those determined previously by dynamic light scattering

Reconstitution of the membrane protein OmpF into biomimetic block copolymer-phospholipid hybrid membranes

Structure and function of many transmembrane proteins are affected by their environment. In this respect, reconstitution of a membrane protein into a biomimetic polymer membrane can alter its function. To overcome this problem we used membranes formed by poly(1,4-isoprene-block-ethylene oxide) block copolymers blended with 1,2-diphytanoyl-sn-glycero-3-phosphocholine. By reconstituting the outer membrane protein OmpF from Escherichia coli into these membranes, we demonstrate functionality of this protein in biomimetic lipopolymer membranes, independent of the molecular weight of the block copolymers. At low voltages, the channel conductance of OmpF in 1 M KCl was around 2.3 nS. In line with these experiments, integration of OmpF was also revealed by impedance spectroscopy. Our results indicate that blending synthetic polymer membranes with phospholipids allows for the reconstitution of transmembrane proteins under preservation of protein function, independent of the membrane thickness