Effect of wetting agent on the dye filtration performance of ultrafiltration membrane

In this study, the wet phase inversion method was used for fabrication of the flat sheet ultrafiltration (UF) membranes. Three different polymer types and two different wetting agents were used for the fabrication. The effect of polymer types and wetting agents were investigated on the structural and dye performance of casted membranes. Two different synthetic dyes, 100 ppm Setazol Red and 100 ppm Setazol Blue, were used for the performance test. Viscosity, contact angle, and molecular weight cut off (MWCO) of casted membranes were measured and an electro kinetic analyzer, dynamic mechanical analyzer (DMA) and scanning electron microscope (SEM) were used to determine the structural properties. While the highest water and dye permeability were obtained with PES-PEG membrane, PSf-plain membrane gave the highest removal efficiency for Setazol Red and Setazol Blue dyes, which was found to be 78.33% and 82.52%, respectively, in the conditions of neutral pH and ambient temperature. Addition of PVP and PEG wetting agents improved the structural properties and permeability of membranes, but the dye removal was decreased as against plain ones. As the retention of PEG and PVP-based PSf and PES membrane was calculated at an average of 50%, they could be used for dye retention separately or could be a candidate as a pretreatment membrane prior to nanofiltration or reverse osmosis to make their lifetime longer.

THE STUDY OF BOUNDARY PERMEABILITY OF MATERIALS USED FOR FISSURE SEALING

Introduction. Dental caries is a widespread dental disease with high intensity and has an impact on the dental health of the population. After teething fissures are the most susceptible to the development of caries in them, due to the peculiarities of their anatomical structure. One of the main directions of primary prevention of caries is the use of sealants for sealing fissures. As sealants are used modern materials from the group of glass ionomer cements, monomernye sealants and composite sealants. Due to the lack of currently clear indications and algorithms for minimally invasive interventions using filling materials in different clinical situations, a study of various materials for invasive fissure sealing in the laboratory. Purpose ― in vitro assess various materials for invasive fissure sealing. Methodology.The procedure of invasive sealing with the use of various filling materials was carried out on the removed intact teeth. Subsequently, the boundary adhesion of sealants was evaluated according to the criteria for direct restoration, as well as the dye permeability along the adhesion boundary. Results. On the basis of the obtained data, the optimal choice of filling materials during the methods of invasive sealing and preventive sealing is justified. Studies show the high potential of polymer composite sealants as a material for sealing fissures both imported and domestic production.

Microshear Bond Strength of High-viscosity Glass-ionomer to Normal and Caries-affected Dentin Under Simulated Intrapulpal Pressure

SUMMARY Objectives: The use of high-viscosity glass-ionomer cements (HVGICs) for atraumatic restorative treatment (ART) restorations is widely practiced with the advent of various HVGICs. However, the bonding of the latter to caries-affected dentin (CAD) should be validated, especially because it is the common substrate left after conservative caries removal following the ART approach. Hence, this study was carried out to evaluate the microshear bond strength (μSBS) of three HVGICs to normal dentin (ND) and CAD under intrapulpal pressure (IPP) simulation. Methods and Materials: The occlusal enamel of 90 molars with mid-coronal caries was cut to expose flat dentin surfaces containing both ND and CAD. Dentin substrates (ND and CAD) were differentiated using visual, tactile, caries-detecting dye, and dye-permeability methods. Prepared crown segments were equally divided (n=30) according to the tested HVGICs into GC Fuji IX GP Fast, Fuji IX GP containing chlorhexidine, and zinc-reinforced ChemFil Rock HVGIC. Microcylinders of tested HVGICs were built up on both dentin substrates (n=30 for each tested HVGIC per each substrate) using starch tubes while the specimens were subjected to simulated IPP of 15 mm Hg. The μSBS test was conducted using a universal testing machine, and failure modes were determined using a scanning electron microscope. Data were statistically analyzed using two-way analysis of variance (ANOVA) with repeated measures, one-way ANOVA, and Bonferroni post hoc tests (α=0.05). Results: For both dentin substrates (ND and CAD), the μSBS values of ChemFil Rock were significantly higher than those recorded for the other HVGICs. The μSBS values of each tested HVGIC to ND and CAD were not statistically different. Failure modes were mainly mixed. Conclusions: Zinc-reinforced HVGIC ChemFil Rock showed superior bonding to ND and CAD compared to the GC Fuji IX GP Fast and Fuji IX with chlorhexidine. However, each of the tested HVGICs showed comparable bonding to both dentin substrates (ND and CAD).

Simulation-based characterization of electrolyte and small molecule diffusion in oriented mesoporous silica thin films

We developed a new workflow for simulating ion reaction-adsorption-diffusion in nanoporous silica-based materials that are resolved through electron microscopy. Firstly, we propose a matched filtering procedure to identify and segment unique porous regions of the material that will be subject to PDE simulation. Secondly, we perform reaction-adsorption-diffusion PDE simulations on representative material regions that are then applied to characterize the entire microscopy-resolved film surface. Using this model, we examine the capacity of a recently synthesized mesoporous film to tune small molecule permeation through modulating the material permeability, surface chemistry<br>including buffering and adsorption, as well as electrolyte composition. Specifically, we find that our proposed matched filtering approach reliably discriminates hexagonal close packed (HCP) porous regions (bulk) from characterized defect regions in transmission electron microscopy (EM) data for nanoporous silica films. Further, based on our implementation of a pH-/surface-chemistry dependent Poisson-Nernst-Planck (PNP) model that is consistent with existing experimental measurements of KCl and CaCl2 conductance, we characterize ion and 5(6)-Carboxyfluorescein (CF) dye permeability in silica-based nanoporous materials over a broad range of ionic strengths, pHs, and surface chemistries. Using this protocol, we probe conditions for selectively tuning small molecule permeability based on mesoporous film pore size, surface charge, ionic strength and surface reactions in the rapid-equilibrium limit. <br><br>

Simulation-based characterization of electrolyte and small molecule diffusion in oriented mesoporous silica thin films

We developed a new workflow for simulating ion reaction-adsorption-diffusion in nanoporous silica-based materials that are resolved through electron microscopy. Firstly, we propose a matched filtering procedure to identify and segment unique porous regions of the material that will be subject to PDE simulation. Secondly, we perform reaction-adsorption-diffusion PDE simulations on representative material regions that are then applied to characterize the entire microscopy-resolved film surface. Using this model, we examine the capacity of a recently synthesized mesoporous film to tune small molecule permeation through modulating the material permeability, surface chemistry<br>including buffering and adsorption, as well as electrolyte composition. Specifically, we find that our proposed matched filtering approach reliably discriminates hexagonal close packed (HCP) porous regions (bulk) from characterized defect regions in transmission electron microscopy (EM) data for nanoporous silica films. Further, based on our implementation of a pH-/surface-chemistry dependent Poisson-Nernst-Planck (PNP) model that is consistent with existing experimental measurements of KCl and CaCl2 conductance, we characterize ion and 5(6)-Carboxyfluorescein (CF) dye permeability in silica-based nanoporous materials over a broad range of ionic strengths, pHs, and surface chemistries. Using this protocol, we probe conditions for selectively tuning small molecule permeability based on mesoporous film pore size, surface charge, ionic strength and surface reactions in the rapid-equilibrium limit. <br><br>

Transport of Cryptosporidium parvum Oocysts in Soil Columns following Applications of Raw and Separated Liquid Slurries

ABSTRACTThe potential for the transport of viableCryptosporidium parvumoocysts through soil to land drains and groundwater was studied using simulated rainfall and intact soil columns which were applied raw slurry or separated liquid slurry. Following irrigation and weekly samplings over a 4-week period,C. parvumoocysts were detected from all soil columns regardless of slurry type and application method, although recovery rates were low (<1%). Soil columns with injected liquid slurry leached 73 and 90% more oocysts compared to columns with injected and surface-applied raw slurries, respectively. Among leachate samples containing oocysts, 44/72 samples yielded viable oocysts as determined by a dye permeability assay (DAPI [4′,6′-diamidino-2-phenylindole]/propidium iodide) with the majority (41%) of viable oocysts found in leachate from soil columns with added liquid slurry. The number of viable oocysts was positively correlated (r= 0.63) with the total number of oocysts found. Destructively sampling of the soil columns showed that type of slurry and irrigation played a role in the vertical distribution of oocysts, with more oocysts recovered from soil columns added liquid slurry irrespective of the irrigation status. Further studies are needed to determine the effectiveness of different slurry separation technologies to remove oocysts and other pathogens, as well as whether the application of separated liquid slurry to agricultural land may represent higher risks for groundwater contamination compared to application of raw slurry.

Development and Validation of a High-Throughput Screening Assay for the Hepatitis C Virus p7 Viroporin

The HCV p7 protein is not involved in viral RNA replication but is essential for production of infectious virus. Based on its putative ion channel activity, p7 belongs to a family of viral proteins known as viroporins that oligomerize after insertion into a lipid membrane. To screen for compounds capable of interfering with p7 channel function, a low-throughput liposome-based fluorescent dye permeability assay was modified and converted to a robust high-throughput screening assay. Escherichia coli expressing recombinant p7 were grown in high-density fed-batch fermentation followed by a detergent-free purification using a combination of affinity and reversed-phase chromatography. The phospholipid composition of the liposomes was optimized for both p7 recognition and long-term stability. A counterscreen was developed using the melittin channel-forming peptide to eliminate nonspecific screening hits. The p7 liposome-based assay displayed robust statistics (Z′ > 0.75), and sensitivity to inhibition was confirmed using known inhibitors.

Regulation of gap junctional charge selectivity in cells coexpressing connexin 40 and connexin 43

Expression of connexin 40 (Cx40) and Cx43 in cardiovascular tissues varies as a function of age, injury, and development with unknown consequences on the selectivity of junctional communication and its acute regulation. We investigated the PKC-dependent regulation of charge selectivity in junctions composed of Cx43, Cx40, or both by simultaneous assessment of junctional permeance rate constants (Bdye) for dyes of similar size but opposite charge, N, N, N-trimethyl-2-[methyl-(7-nitro-2,1,3-benzoxadiol-4-yl)amino]ethanaminium (NBD-M-TMA; +1) and Alexa 350 (−1). The ratio of dye rate constants (BNBD-M-TMA/BAlexa 350) indicated that Cx40 junctions are cation selective (10.7 ± 0.5), whereas Cx43 junction are nonselective (1.22 ± 0.14). In coexpressing cells, a broad range of junctional selectivities was observed with mean cation selectivity increasing as the Cx40 to Cx43 expression ratio increased. PKC activation reduced or eliminated dye permeability of Cx43 junctions without altering their charge selectivity, had no effect on either permeability or charge selectivity of Cx40 junctions, and significantly increased the cation selectivity of junctions formed by coexpressing cells (approaching charge selectivity of Cx40 junctions). Junctions composed of Cx43 truncated at residue 257 (Cx43tr) were also not charge selective, but when Cx43tr was coexpressed with Cx40, a broad range of junctional selectivities that was unaffected by PKC activation was observed. Thus, whereas the charge selectivities of homomeric/homotypic Cx43 and Cx40 junctions appear invariant, the selectivities of junctions formed by cells coexpressing Cx40 and Cx43 vary considerably, reflecting both their relative expression levels and phosphorylation-dependent regulation. Such regulation could represent a mechanism by which coexpressing cells such as vascular endothelium and atrial cells regulate acutely the selective intercellular communication mediated by their gap junctions.

Modulation of Cx46 hemichannels by nitric oxide

Gap-junction hemichannels are composed of six protein subunits (connexins). Undocked hemichannels contribute to physiological autocrine/paracrine cell signaling, including release of signaling molecules, cell-volume regulation, and glucose uptake. In addition, hemichannels may be pathologically activated by dephosphorylation and cell-membrane depolarization. Such hemichannel opening may induce and/or accelerate cell death. It has been suggested that connexin43 (Cx43) hemichannels are sensitive to redox potential changes and that one or more intracellular cysteines is/are important for this process. Cx46 is expressed in the lens, and its dysfunction induces cataract formation. It contains six cysteines in the extracellular loops, one in the fourth transmembrane helix, and two in the COOH-terminal domain. The latter may be susceptible to oxidation by nitric oxide (NO), which could be involved in cataract formation through cysteine S-nitrosylation. Here we report studies of the effects of the NO donor S-nitrosoglutathione (GSNO) on the electrical properties and fluorescent-dye permeability of wild-type Cx46 and mutant hemichannels expressed in Xenopus laevis oocytes. GSNO enhanced hemichannel voltage sensitivity, increased tail-current amplitude, and changed activation and closing kinetics in Cx46 and Cx46-CT43 (Cx46 mutant in which the COOH terminus was replaced with that of Cx43), but not in Cx46-C3A (Cx46 in which the intracellular and transmembrane helix 4 cysteines were mutated to alanine). We conclude that Cx46 hemichannels are sensitive to NO and that the NO effects are mediated by modification of one or more intracellular cysteines. However, it is unlikely that NO induces cataract formation due to the hemichannel activation, because at normal resting potential, NO had no major effects on Cx46 hemichannel permeability.

Gliotactin, a novel marker of tricellular junctions, is necessary for septate junction development in Drosophila

Septate junctions (SJs), similar to tight junctions, function as transepithelial permeability barriers. Gliotactin (Gli) is a cholinesterase-like molecule that is necessary for blood–nerve barrier integrity, and may, therefore, contribute to SJ development or function. To address this hypothesis, we analyzed Gli expression and the Gli mutant phenotype in Drosophila epithelia. In Gli mutants, localization of SJ markers neurexin-IV, discs large, and coracle are disrupted. Furthermore, SJ barrier function is lost as determined by dye permeability assays. These data suggest that Gli is necessary for SJ formation. Surprisingly, Gli distribution only colocalizes with other SJ markers at tricellular junctions, suggesting that Gli has a unique function in SJ development. Ultrastructural analysis of Gli mutants supports this notion. In contrast to other SJ mutants in which septa are missing, septa are present in Gli mutants, but the junction has an immature morphology. We propose a model, whereby Gli acts at tricellular junctions to bind, anchor, or compact SJ strands apically during SJ development.