Use Of Porous Membranes Research Articles

Different types of explants and natural ventilation systems influence the accumulation of dry weight and of total phenolic compounds in Aloysia gratissima (Verbenaceae)

The objective of this study was to evaluate the effect of the use of different natural ventilation systems on the growth and accumulation of total phenolic compounds in Aloysia gratissima. Nodal and apical segments with 1 pair of leaves were inoculated in flasks containing ½ MS culture medium without sucrose and supplemented with 0.1 mg L-1 indole-butyric acid. The cultivation systems included a conventional system (NMS) and alternative membrane systems with 1 (AMS1), 2 (AMS2) and 4 (AMS4) low-cost membranes. After 30 days, the in vitro growth, leaf area, dry weight and accumulation of phenolic compounds were evaluated. Plantlets from apical segments showed superior results in all variables analyzed. The use of the NMS compromised plantlet growth. However, improved results were obtained with the use of porous membranes, with the best growth observed in AMS4. The leaf area of plantlets originating from apical segments was 3.03 times greater than that of plantlets from nodal segments. Plantlets in the NMS had the lowest values of leaf area, root length, number of leaves and dry weight. However, the use of membranes allowed higher growth. The AMS4 treatment increased the leaf dry weight accumulation by 6.13-fold compared to that obtained with the NMS treatment. The accumulation of total phenolic compounds increased with the use of greater numbers of porous membranes. The use of apical segments and lids with 4 porous membranes is recommended for micropropagation of the species. The use of an alternative membrane system positively influences the accumulation of total phenolic compounds.

Adsorption and swelling studies of 2-hydroxyethyl methacrylate- and N,N-dimethylacrylamide-based porous copolymers and their possible applications for QCM-sensors

An efficient one-vial method is described for the synthesis of porous frameworks from copolymers of 2-hydroxyethyl methacrylate with N,N-dimethylacrylamide in various monomers ratios. Characterization, swelling and sorption studies were performed for the materials obtained. A proof of concept for the use of porous membranes on QCM-type biosensors design was performed. Copolymerization between HEMA and DMAa was confirmed through ATR-FTIR and 1H NMR, while thermal analyses performed by TGA featured a dependence between the decomposition temperature and monomers ratio. Copolymers without cross-linker were unstable in water immersions, compromising their applicability. Thus, copolymer morphology was studied by adding a cross-linker agent (EGDMA). Swelling and sorption kinetics were evaluated by using two model molecules: methylene blue and lead (II) ions from aqueous solutions. We observed that swelling capacity is directly related to the cross-linking agent ratio, and DMAa content of the copolymer also. Finally, a copolymer with 50/50 mol%:HEMA/DMAa and 5 mol%:EGDMA (S4 copolymer) was selected as a covering membrane on the gold surface of a quartz crystal microbalance (QCM) to explore its potential as a material for the development of QCM-sensors. In conclusion, the copolymeric porous frameworks, based on N,N-dimethylacrylamide- and 2-hydroxyethyl methacrylate, are suitable for remediation and adsorption applications, including the support recognition probes in biosensors.

Light quality and sealing type affect in vitro growth and development of Capsicum frutescens cultivars

Abstract The aim of this work was to evaluate the effect of five light qualities [fluorescent lamps (FL); white (WL), red (RL), blue (BL), or red/blue LEDs (RBL)] and two types of flask sealing (with or without porous membranes) in the in vitro germination and growth of two Capsicum frutescens cultivars (Espaguetinho and Cayenne). For this, two seeds were inoculated per flask (350 mL) containing 50 mL of MS medium with 100 mg L-1 myo-inositol, 30 g L-1 sucrose, 6.0 g L-1 agar, and pH 5.8 ± 0.1. The plants were kept under culture room conditions (16-h photoperiod, 25 ± 2°C and irradiance of 40 μmol m-2 s-1). The experiment was arranged in CRD, 2x5x2 factorial scheme (Cultivar X Light qualities X Sealing type). At 42 days, the following traits were evaluated: percentage of germination; root and shoot length; number of green leaves, senescent leaves and nodal segments; and fresh and dry weight. Plants grown under RL and BRL, showed greater number of green leaves, and longer shoots and roots. The use of porous membranes remarkably reduced the number of senescent leaves. Thus, the use of porous membranes, RL and BRL are recommended since they improve growth and development of pepper in vitro.

Use of porous membranes in tissue barrier and co-culture models.

Porous membranes enable the partitioning of cellular microenvironments in vitro, while still allowing physical and biochemical crosstalk between cells, a feature that is often necessary for recapitulating physiological functions. This article provides an overview of the different membranes used in tissue barrier and cellular co-culture models with a focus on experimental design and control of these systems. Specifically, we discuss how the structural, mechanical, chemical, and even the optical and transport properties of different membranes bestow specific advantages and disadvantages through the context of physiological relevance. This review also explores how membrane pore properties affect perfusion and solute permeability by developing an analytical framework to guide the design and use of tissue barrier or co-culture models. Ultimately, this review offers insight into the important aspects one must consider when using porous membranes in tissue barrier and lab-on-a-chip applications.

RED WINE EXTRACT OBTAINED BY MEMBRANE-BASED SUPERCRITICAL FLUID EXTRACTION: PRELIMINARY CHARACTERIZATION OF CHEMICAL PROPERTIES.

Abstract – This study aims to obtain an extract from red wine by using membrane-based supercritical fluid extraction. This technique involves the use of porous membranes as contactors during the dense gas extraction process from liquid matrices. In this work, a Cabernet Sauvignon wine extract was obtained from supercritical fluid extraction using pressurized carbon dioxide as solvent and a hollow fiber contactor as extraction setup. The process was continuously conducted at pressures between 12 and 18 MPa and temperatures ranged from 30 to 50oC. Meanwhile, flow rates of feed wine and supercritical CO 2 varied from 0.1 to 0.5 mL min -1 and from 60 to 80 mL min -1 (NCPT), respectively. From extraction assays, the highest extraction percentage value obtained from the total amount of phenolic compounds was 14% in only one extraction step at 18MPa and 35oC. A summarized chemical characterization of the obtained extract is reported in this work; one of the main compounds in this extract could be a low molecular weight organic acid with aromatic structure and methyl and carboxyl groups. Finally, this preliminary characterization of this extract shows a remarkable ORAC value equal to 101737 ± 5324 µmol Trolox equivalents (TE) per 100 g of extract.

Towards improved separation performance using porous FO membranes: The critical roles of membrane separation properties and draw solution

The use of porous membranes for forward osmosis (FO) applications has been recently reported in the literature. In the current study, a series of porous-FO membranes were fabricated to systematically study the role of membrane separation properties on the FO performance of porous membranes. In addition, two types of draw solutes, a polyelectrolye poly(sodium 4-styrene-sulfonate) (PSS) and a neutral linear polymer polyethylene glycols (PEGs), were evaluated as the draw solutes. The effect of draw solution properties (type of draw solutes, their molecular weight, and concentration) on the FO performance was investigated. Membrane post-treatment at higher annealing temperature was found to increase solute rejection and decrease water permeability. As a result, reverse solute diffusion (RDS) became less severe at higher annealing temperature. The FO water flux of the porous membranes was affected by RDS in addition to the water permeability of the porous FO membranes, both of which had a strong dependence on the annealing temperature. Compared to neutral PEG, the polyelectrolyte PSS was a much better choice for draw solutes with higher FO water flux and lower RDS. The better performance of PSS can be attributed to its higher rejection by the porous FO membranes and its high osmotic pressure compared to PEG at same weight concentration. Implications for the design of porous FO membranes and draw solution are discussed.

The Establishment of in Vivo -Like Tissue Culture Conditions in ThinCert™ Tissue Culture Products

BioTechniquesVol. 43, No. 6 Application Forum - Sponsored PaperOpen AccessThe establishment of in vivo-like tissue culture conditions in ThinCert™ tissue culture productsSven Mühlfriedel & Günther KnebelSven MühlfriedelGreiner Bio-One GmbH, Frickenhausen, GermanySearch for more papers by this author & Günther KnebelGreiner Bio-One GmbH, Frickenhausen, GermanySearch for more papers by this authorPublished Online:16 May 2018https://doi.org/10.2144/000112701AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinkedInReddit IntroductionFor many years animal experimentation provided the singular means to access intact and living tissue for biological and pharmaceutical research. This situation changed with the introduction of cell culture methods that allowed tissue reconstruction from individual cells in vitro. Such approaches typically involve the use of porous membrane supports and/or three-dimensional collagen gels to re-create in vivo-like growth in cell culture environments1,2. Today, reconstructed intestinal and oral epithelia, airway epithelium, skin and cornea models are frequently used to assess corrosive and irritant effects of substances and to study drug delivery and pathology.Tissue Reconstruction Using Thincert™ Cell Culture ProductsOne of the main challenges in tissue reconstruction is to restore specific tissue functions in vitro. Depending on the particular tissue type and scientific question such critical features may comprise the barrier function, the capability of substance transport and the potential to express certain marker genes and signaling molecules. Optimal cell culture conditions must be well-established to re-create native function and maintain such features in vitro.For instance, it has been determined that cultivated epidermal keratinocytes differentiate and form a coherent stratum corneum only if they are exposed to air3,4. Specific cell culture labware, such as ThinCert™ cell culture inserts with porous membrane supports, allows cultivation of epidermal cells at the air-liquid-interface (air-lift-culture) to ensure the formation of a stratum corneum.Fig. 1 illustrates the two major steps of the formation of a skin equivalent in vitro, including the submersed cultivation of the dermis equivalent and the air-lift-culture of the epidermal layer. For improved nutrient supply the air-lift-culture can be performed in the novel ThinCert™Plate. This plate permits air-lift-cultivations with larger volumes of culture medium. The outcome is an improved nutrient supply to the cultivated tissue with reduced frequency of medium exchange, resulting in an improved quality of the generated tissue (Fig. 2).Figure 1. Reconstruction of a full thickness skin model.A collagen gel containing primary dermal fibroblasts is cultivated under submersed conditions on the porous membrane of a ThinCert™ cell culture insert (A). Subsequently, primary epidermal keratinocytes are seeded on top of the dermis equivalent. At this stage cell culture medium is filled only to the level of the insert membrane to allow cultivation at the air-liquid-interface and formation of a stratum corneum (B). HE-staining of a reconstructed full thickness skin (C).Figure 2. Improved nutrient supply with the ThinCert™Plate.A gingival epithelium was reconstructed from oral squamous cells using ThinCert™ cell culture inserts in combination with either conventional well plates or the novel ThinCert™Plate. The enlarged culture medium reservoir of the ThinCert™Plate enabled medium exchanges to be reduced from every day, as required by the conventional plate, to every 4th day. In addition to reducing the frequency of medium exchange, a significantly higher glucose concentration was maintained in the ThinCert™Plate as compared to the standard condition (A, glucose measurements were performed prior to medium changes). Moreover, tissue generated in the ThinCert™Plate appeared thicker and had more cell layers (B, HE-staining of the gingival epithelium after 29 days in culture).ConclusionsThinCert™ cell culture inserts enable the reconstruction of functional, multi-layered tissues from individual cells in vitro. Tissues may be cultivated at the air-liquid-interface with improved cellular oxygen supply, providing differentiation stimuli for development of air-exposed terminal structures such as the epidermal stratum corneum.LinksFor Further Information Contact:www.gbo.com/bioscience/thincert

Use of Porous Membranes Modified with Polyelectrolyte Multilayers as Substrates for Protein Arrays with Low Nonspecific Adsorption

Coating of substrates with polyelectrolyte multilayers terminated with poly(acrylic acid) (PAA) followed by activation of the free -COOH groups of PAA provides a surface that readily reacts with amine groups to allow covalent immobilization of antibodies. The use of this procedure to prepare arrays of antibodies in porous alumina supports facilitates construction of a flow-through system for analysis of fluorescently labeled antigens. Detection limits in the analysis of Cy5-labeled IgG are 0.02 ng/mL because of the high surface area of the alumina membrane, and the minimal diameter of the substrate pores results in binding limited by kinetics, not mass transport. Moreover, PAA-terminated films resist nonspecific protein adsorption, so blocking of antibody arrays with bovine serum albumin is not necessary. These microarrays are capable of effective analysis in 10% fetal bovine serum.

Solid state aspects of oxidation catalysis

The main subject of this review is the consideration of catalytic oxidation reactions, which are greatly influenced by solid state effects in the catalyst material. Emphasis is laid upon the correlation between the presence of mobile ionic defects, together with the associated ionic conductivity, and the catalytic performance. Both total and selective oxidation reactions and oxidative conversion reactions are considered. Well-known examples of such behaviour include oxidative methane conversion with lanthanide oxides, carbon monoxide oxidation on fluorite type catalysts, selective olefin oxidation using vanadia based catalysts, etc. Furthermore, because oxygen exchange between gas and solid is always part of the oxidation process, this is considered too. The discussion of the application of the solid oxides under consideration to practically important oxidation processes, together with the influence thereon of their solid state properties, forms a major part of this review. Computational modelling and simulation of catalyst structure and behaviour is also considered. Special attention is given to the potentialities offered by using ionic and mixed conducting oxides either as the electrode material in a solid electrolyte fuel cell (SOFC) or as a separating, dense membrane in a ceramic membrane reactor. The use of porous membranes in such reactors is also taken into consideration. On the one hand these may be used to study the above relationship between catalytic behaviour and solid state properties, on the other hand to obtain a reactor configuration allowing better use of reactants and/or catalysts. Besides the controlled supply of (or removal) of oxygen to (or from) the side where the catalyst and the reactants are located, a promising feature of both experimental approaches is that the oxygen flux may alter the relative presence of different oxygen species (O 2,O,O 2 −,O 2 2−,O 3 −,O −, etc.) on the catalyst surface. In this way species are provided having a strong influence on the selectivity for partial oxidation reactions and oxidative conversion reactions.

A percutaneous device to study glucose kinetics in subcutaneous tissue fluid.

In the current study subcutaneous glucose kinetics were investigated in tissue fluid collected with a percutaneous device (PD). PDs containing a subcutaneous tissue chamber were implanted subcutaneously in New Zealand white rabbits. Sintered titanium fiber mesh sheets were used for subcutaneous anchorage of the PD. The bottom of the subcutaneous tissue chamber was either covered with a titanium fiber mesh sheet, a cellulose acetate membrane, or left uncovered. Subcutaneous glucose kinetics were determined after injection of octreotide and glucagon. The tissue reaction to the implants was evaluated histologically. No dynamic relationship was observed between glycaemia and subcutaneous tissue fluid glucose for all membrane covered devices. Histological evaluation showed that the presence of a seroma cavity in combination with obstruction of the membrane prevented adjustment of the subcutaneous glucose concentration in response to changes in glycaemia. In the uncovered devices, on the other hand, changes in glycaemia were reflected in subcutaneous tissue fluid. Our results prove that it is possible to measure changes in the glucose concentration in subcutaneous tissue fluid collected with a percutaneous device. Therefore, we conclude that a percutaneous device has an application as model to study the in vivo performance of implantable glucose sensors. The use of porous membranes in such devices has to be avoided.

Critical Fluids in Porous Media

The behavior of fluids confined in porous materials has been of interest to engineers and scientists for many decades. Among the applications driving this research are the use of porous membranes to achieve liquid-liquid separations and to deionize water, the use of porous materials as beds for catalysis, and the need to extract liquids (especially oil and water) from such media. Many of these applications depend on transport, which is governed by flow or diffusion in the imbibed fluids. Both the flow and diffusion of multiphase fluids in porous media, however, strongly depend on the morphology of phase-separated domains, and on the kinetics of domain growth. Thus, it is worthwhile to study the behavior of multiphase fluids in porous media in the absence of flow. Recently, much attention has focused on even simpler systems that still capture these essential features, namely, near-critical binary liquid mixtures and vapor-liquid systems in model porous media, such as Vycor and dilute silica gels. Although near-critical fluids may seem rather artificial as models for multiphase liquids, there are several advantages associated with them. In general, domain morphology and growth kinetics are governed primarily by competition between interfacial tension and the preferential attraction of one phase to the surface of the medium. In near-critical fluids, the relative strength of these two energy scales is sensitive to temperature, and can therefore be altered in a controlled fashion. In addition, the kinetics of domain growth are sensitive to the temperature quench depth, and can be controlled.

Multiparameter analysis of primary epithelial cultures grown on cyclopore membranes.

The use of porous membranes as culture support for epithelial cells has previously been shown to cause functional differentiation of these cells mimicking an in vivo condition, in contrast to culture on plastic. The different materials of which the membranes are made also have different properties, such as transparency, rigidity, and retention of molecules. Cyclopore membranes (polyethylene terephtalate) are permeable, transparent, rigid, and have low protein retention. In this study we examined the applicability of assessing multiple parameters on a single culture of primary epithelial cells on a Cyclopore membrane. Cultures of transitional epithelial cells on these membranes differentiate into an organoid-like epithelium. We were able to perform morphometric analysis during and after cell culture and to quantitate proliferation and differentiation by double immunoenzymatic staining. On these cultures, quantitative radiochemical analysis could also be achieved, retaining the morphology and the immunohistochemical staining. Cross-sections of paraffin-embedded and plastic-embedded cultures were analyzed qualitatively by light and transmission electron microscopy, respectively. Finally, cytokeratins in these cultures could also be visualized by immunofluorescence analysis. This suitability for simultaneous assessment of both qualitative and quantitative parameters on a single cell culture grown on a Cyclopore membrane reduces the need of biological materials and may lead to better insight into physiological processes.

An Evaluation of the Use of Porous Membranes for the Dewatering of Wellhead Bitumen/Water/Mineral Emulsions

Abstract In-situ bitumen and heavy oil recovery by steam stimulation can produce large volumes of oil-in-water emulsions. Several difficulties facing recovery operations are the limited water supply in relation to the volumes required for steam injection and the processing of water-rich emulsions to low-water content bitumen. In current practice these emulsions require substantial amounts of chemical additives with large settling tanks and elevated temperatures. An evaluation of the use of porous membranes for the treatment of these emulsions has been made which has led to the development of a process that will produce single pass (80%) steam quality water as membrane permeate and a bitumen-rich stream which can be processed by existing dewatering methods. Details of the performance of several membranes of various pore sizes are given and a comparison is made with existing single-pass steam boiler requirements. Of those tested, cellulose membranes resisted fouling by the bitumen, and thus are the most pro...