Dye Flux Research Articles

Effects of hyperglycemia on airway epithelial barrier function in WT and CF 16HBE cells

Cystic fibrosis related diabetes (CFRD), the main co-morbidity in cystic fibrosis (CF), is associated with higher rates of lung function decline. We hypothesize that airway epithelial barrier function is impaired in CF and is further exacerbated under hyperglycemia, worsening pulmonary outcomes. Using 16HBE cells, we studied the effects of hyperglycemia in airway epithelial barrier function. Results show increased paracellular dye flux in CF cells in response to insulin under hyperglycemia. Gene expression experiments identified claudin-4 (CLDN4) as a key tight junction protein dysregulated in CF cells. CLDN4 protein localization by confocal microscopy showed that CLDN4 was tightly localized at tight junctions in WT cells, which did not change under hyperglycemia. ln contrast, CLDN4 was less well-localized in CF cells at normal glucose and localization was worsened under hyperglycemia. Treatment with highly effective modulator compounds (ETI) reversed this trend, and CFTR rescue was not affected by insulin or hyperglycemia. Bulk RNA sequencing showed differences in transcriptional responses in CF compared to WT cells under normal or high glucose, highlighting promising targets for future investigation. One of these targets is protein tyrosine phosphatase receptor type G (PTPRG), which has been previously found to play a role in defective Akt signaling and insulin resistance.

Consumption of honey ameliorates lipopolysaccharide-induced intestinal barrier dysfunction via upregulation of tight junction proteins.

The leaky gut barrier is an important factor leading to various inflammatory gastrointestinal disorders. The nutritional value of honey and variety of its health benefits have long been recognized. This study was undertaken to assess the role of Indian mustard honey in preventing lipopolysaccharide (LPS)-induced intestinal barrier dysfunction using a combination of in vitro and in vivo experimental model systems. LPS was used to induce intestinal barrier damage in a trans-well model of Caco-2 cells (1µg/ml) and in Swiss albino mice (5mg/kg body weight). Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) were used to analyse sugar and phenolic components in honey samples. The Caco-2 cell monolayer integrity was evaluated by transepithelial electrical resistance (TEER) and paracellular permeability assays. The histopathology of intestinal tissue was analysed by haematoxylin and eosin dual staining. The quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to quantify the transcription of genes. The protein expression was analysed by immunofluorescence, western blot and ELISA-based techniques. The in vitro data showed that honey prevented LPS-induced intestinal barrier dysfunction dose dependently as was measured by TEER and paracellular flux of FITC-dextran dye. Further, the in vivo data showed a prophylactic effect of orally administered honey as it prevented the loss of intestinal barrier integrity and villus structure. The cellular localization and expression of tight junction (TJ) proteins were upregulated along with downregulation of pro-inflammatory cytokines in response to the administration of honey with LPS. The findings of this study suggest a propitious role of honey in the maintenance of TJ protein integrity, thereby preventing LPS-induced intestinal barrier disintegration.

Cross-section and pore size regulation of hydroxyurea-modified polyacrylonitrile membrane by NH2-CNT and Si(OEt)4 filler and heat treatment for dye removal application at medium temperature

The preparation of ultrafiltration (UF) membranes for dye removal at higher temperature is a challenging task. In this study, hydroxyurea-modified polyacrylonitrile (PAN-Hu) was used to prepare hydrophilic UF membrane. The further addition of NH2-grafted carbon nanotube (CNT) and tetraethoxysilane(TEOS) resulted in a change of the cross-section morphology of the membrane from half-sponge to an asymmetrical one, with an increased pore size due to the hydrophobic nature of the fillers. The resulting PHT/Si membrane showed a higher pure water flux (130 L/m2 h at 1 bar) than PAN-Hu, with a 98% rejection rate of Congo red (CR) from a 0.1% NaCl aqueous solution. The dye rejection mechanism was explained based on the molecular size and surface charge density of dyes, as well as force analysis inside the spongy skin layer. Subsequently, two heating methods were adopted to stabilize the structure of membrane, and improve its thermal stability for filtration at medium temperature (60 °C). After heating in water at 60 °C for 5 days, the rejection rate of Methyl blue (MB) in a 0.1% NaCl solution increased by 80%, but the flux of membrane decreased by more than 50%. On the other hand, heating at 100 °C in glycerol for 10 hrs led to a similar increase in dye rejection but a lower decrease in flux. Specifically, the heated PHT/Si membrane showed a dye flux of 64 L/m2 h, and an MB rejection rate of 94% from water, 80% from a 0.1% NaCl solution at 20 °C. Additionally, all membranes showed a higher flux and slightly lower rejection at 60 °C compared with that at 20 °C. Instrumental characterization revealed that morphology change of membrane was caused by the shrinkage effect through chain rearrangement as a result of heat treatment. But PAN-Hu showed a greater decrease in pore size than PHT/Si membrane. The reason lies in that CNT or SiO2 in PHT/Si membrane acts as physical crosslinking point. Their dimension stabilization effect limits the free movement of polymer chains and affects the pore size change of membrane. Overall, this study can help to tailor the porous structure of UF membranes for dye removal under different temperatures.

Removal of heavy metals and dye from water and wastewater using nanofiltration membranes of polyethersulfone modified with functionalized iron-silica nanoparticles

ABSTRACT In this study, the performance of polyethersulfone (PES) membranes, fabricated by modifying the iron nano-particles (M-Fe3O4), was investigated to remove heavy metals (HM) and Direct red 16 (DR16) dye from water. In this new research work, amine groups were first fixed on nano-particles by modifying iron nano-particles using TEOS and APTES methods. In the next step, M-Fe3O4 was used in the structure of membranes, and their effect on surface properties, hydrophilicity (HD), pure water (PW) flux, roughness (Ra), water permeability and removal rate of copper ion (CI) and DR16 dye were investigated. Also, characterization methods such as X-ray powder diffraction (XRD), scanning force microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and antifouling properties have been used to evaluate the synthetic membranes. Thus, the performance of composite membranes showed that the pure water (PW) flux of the membrane M-Fe3O4 increased 1.9 times compared to the pure membrane. Moreover, the anti-fouling tests showed that the mixed matrix membranes (MMM) with 0.1 wt% of M-Fe3O4 showed the best anti-fouling properties with a 90% recovery rate and 55.98% fouling resistance. On the other hand, results showed that 0.1 wt% composite membrane resulted in the removal of CIs 92% and dye 99%.

Different roles of P2X4- and P2Y1-receptors in the atrial pathogenesis during prolonged pressure overload.

Pressure overload (PO) involve increase in interstitial fluid shear in cardiac muscle during cardiac cycles due to detachment of myocytes from the extracellular matrix and myocyte slippage. However, the effects of shear stress on cardiac muscle and their pathophysiological roles are poorly understood. We have recently discovered that shear stress induces global Ca2+ waves via activation of P2 purinergic receptors in atrial myocytes by ATP released from the cells, and that this ATP release is mediated by connexin 43 (Cx43) gap junction hemichannels. In this study, we investigated role of shear stress signaling in PO-induced atrial remodeling and failure. We used a transverse aortic constriction (TAC) rat model to increase afterload and examined shear stress responses and remodeling of their signaling molecules during the development of pathological phenotypes by progressive TAC. After 5-week TAC, atrial dimension was enlarged with ventricular hypertrophy, which was followed by severe atrial dilation as well as ventricular failure at long-term (>20-week) TAC. Atrial myocytes were enlarged following 5-week TAC, which was maintained during more prolonged TAC. In the 5-week-TAC left atrial (LA) cells, ATP release was increased with no changes in Cx43 expression and in Cx43 hemichannel-mediated dye (calcein) flux. At this stage, however, function (cation current) of P2X4 receptor (P2X4R) and their protein expressions were largely enhanced. In failed LA cells, reduction in the Cx43 expression and smaller Cx43 hemichannel-mediated dye flux were observed. In failed LA myocytes, shear-induced longitudinal Ca2+ waves that were mediated by P2Y1 receptor (P2Y1R), were enhanced with higher P2Y1R expression. The opposite changes in the shear-induced responses mediated by P2X4R and P2Y1R and in their expressions suggest that P2X4R and P2Y1R may play beneficial and harmful role, respectively, in the PO-dependent atrial pathogenesis.

High-performing PVDF membranes modified by Na+ MMT/ionic liquids (ILs) with different chain lengths: dye adsorption and separation from O/W emulsion

At present, the continuous deterioration of water environment is a serious threat to the sustainable society. Therefore, there is an urgent need for an antifouling film which can remove both dyes and oil/water. Herein, a series of ionic liquids (ILs) with different chain length was prepared to modified Na-montmorillonite (Na+ MMT) and mixed with polyvinylidene fluoride (PVDF) by blending technology. The obtained ILs–Na+ MMT film exhibited excellent hydrophilic performance and separation performance in the separation of dye and emulsion wastewater by phase transformation method. Specifically, we inspected ILs–Na+ MMT film with different chain lengths (C4, C8, C12, C16). Interestingly, the ionic liquid chain length(C12) of modified film showed good antifouling performance, the flux recovery rate for anionic (99.67%) and cationic dyes (98.72%) and bovine serum albumin (BSA) (98.1 %) at a high level as well as high rejection efficiency for oil–water emulsions, the modified films have excellent sustainability after 6 cycles of use (over 89%). In addition, dye flux was increased by 671% compared with pure PVDF membranes, and the waste rate reached 99.99% by dye filtration, indicating that PVDF/ILs-Na+ MMT has potential applications in oily and aqueous dye adsorption fields.

Graphene Oxide-Chitosan Network on a Dialysis Cellulose Membrane for Efficient Removal of Organic Dyes.

Currently, water pollution is a significant health problem for both humans and animals due to large amounts of dye-containing wastewater. Thus, polymer composite membranes (PCMs) are considered as efficient adsorption/filtration membranes that can be utilized for removing organic dyes from contaminated water/wastewater. In this study, the goal is to explore the modification of the interfacial dialysis cellulose (DC) surface through molecular interactions of an active graphene oxide-chitosan (GO-CTS) composite hydrogel (GCCH) network without the use of an external cross-linker toward an effective dye removal ability using a simple casting process and a low-cost adsorption technique, resulting in the formation of a PCM, i.e., GO/CTS/DC membrane (GCD-mems). Concomitantly, the incorporation of the GCCH network (as an active hybrid network) and DC (as a supporting material) is considered as a promising approach toward a dye-removing PCM. As a result, the GCD-mems showed that cellulose robustly interacted via the chemical bonds of the GCCH network by maintaining the three-dimensional (3D) porous layer structures, and the functional surface of the membrane was enhanced toward specific groups for an effective dye removal approach. In addition, there is a significant improvement in dye removal performance after modification of the interfacial DC surface through molecular interactions of GCCH, i.e., high adsorption capacities of cationic and anionic dye molecules on the GCD-mems, compared to the relevant GO-based adsorbents. Also, the dye flux and rejection of the GCD-mems can simultaneously remove both methylene blue and Congo red. In the adsorption, it is appropriate with the pseudo-second-order and Langmuir models corresponding to chemical adsorption and monolayer approaches, as well as physical sieving through the 3D layers of porous channels of GCD-mems during the filtration process. Moreover, the structural stability and sustainability of the PCMs are enhanced during the recycling process, and the use of ethanol in the recycling process further simplifies the process and reduces the cost of the PCMs. Thus, the GCD-mems are encouraged as potential candidates that can be applied directly in the removal of dyes from the wastewater of textile industries or selective dialysis applications.

Real-time monitoring the interfacial dynamic processes at model cell membranes: Taking cell penetrating peptide TAT as an example

A real-time and molecule-level monitoring of the interfacial dynamic interactions between molecules and a cell membrane is of vital importance. Herein, taking TAT, one of the most representative cell penetrating peptides, as an example, a photo-voltage transient technique and a dynamic giant bistratal vesicle (GBV) leakage method were combined with the traditional giant unilamellar vesicle (GUV) leakage assays, to provide a molecule-level understanding of the dynamic membrane interaction process performed in a low ionic strength and neutral pH condition. The photo-voltage test based on supported phospholipid bilayers showed a quick disturbance (<1 min) followed by a continuous reconstruction of the membrane by peptides, leading to a slight destruction (at TAT concentrations lower than 1 μg mL−1, i.e., 0.64 μM) or strong damage (e.g. at 10 μg mL−1, i.e., 6.4 μM) of the bilayer structure. The GUV/GBV leakage assays further demonstrated the TAT-induced membrane deformation and transmembrane diffusion of dyes, which occurred in an immediate, linear, and TAT-concentration dependent manner. Moreover, the flux of dye across the substrate-immobilized membranes was approximately three times of that across the substrate-free ones. This work gives information on time and molecular mechanism of the TAT-membrane interactions, demonstrates the different permeabilizing effects of TAT on immobilized and free membranes. Overall, it provides useful strategies to investigate the nano-bio interfacial interactions in a simple, global and real-time way.

Multifunctional PAN UF membrane modified with 3D-MXene/O-MWCNT nanostructures for the removal of complex oil and dyes from industrial wastewater

• Fusiform 3D MXene/O-MWCNT nanostructure was successfully synthesized. • Multifunctional MXene/O-MWCNT@PAN UF membrane was fabricated via phase inversion. • The synergy of MXene/O-MWCNT enhance the flux and rejection of oil and soluble dye. • Outstanding antifouling and recyclable properties were achieved by the membranes. • The membranes exhibited excellent chemical stability in harsh condition. Despite advances in membrane technology, the separation of complex oily wastewater using membrane filtration remains a daunting challenge for the industry. Recent approaches including membrane modification with two-dimensional (2D) nanosheets, showed susceptibility to swelling, fouling, and instability during operation. As a game-changer approach, a polyacrylonitrile (PAN) UF membrane modified with 3D nanostructured composite of MXene and O-MWCNT was introduced for the first time to treat complex oily wastewater. The composite membrane showed high separation performance of soluble dye-oil-water emulsion while maintaining high water permeability. Moreover, during the operational period, the composite membrane exhibits excellent antifouling and anti-swelling properties due to the synergetic effects conferred by the 3D nanostructures. Furthermore, the composite membrane possesses remarkable chemical stability evidenced by its high corrosion resistance when exposed to a strong acid (3 M HCl) and oxidant (NaOCl) solution for a long-time period. Overall, the operational stability was maintained in terms of flux and high rejection of oil and dye over a 45 h long-term operation. Consequently, this work provides an innovative, stable, and highly facile process for fabricating scalable UF composite membrane for the treatment of complex oily wastewater in a harsh chemical environment.

Peroxopolyoxometalate nanoparticles blended PES membrane with improved hydrophilicity, anti‐fouling, permeability, and dye separation properties

AbstractPoly(ethersulfone) (PES) is one of the polymers most widely used for the fabrication of ultrafiltration or nanofiltration membranes in various applications, but its membrane suffers from fouling. In this study, preparation, characterization, and performance of PES nanocomposite membrane comprising peroxopolyoxometalate nanoparticles was studied to provide improved permeability and anti‐fouling properties. The high oxygen ratio of the PW4 nanoparticles could enhance the hydrophilicity of the membranes. The PW4 nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), energy dispersive X‐ray (EDX), and X‐ray diffraction analyses. The mixed matrix membranes were fabricated using a non‐solvent induced phase‐separation method. The fabricated membranes were characterized using atomic force microscopy, attenuated total reflection, SEM, EDX mapping, total average porosity, thermogravimetric analyze, and water contact angle experiments. The dye flux and rejection, pure water permeability and anti‐fouling properties of the membranes were investigated. All of the membranes blended by different contents of the PW4 nanoparticles presented better performance compared to the unmodified membrane. The filtration performance of the membranes in reactive green 19 (RG19) and reactive yellow 160 (RY160) dye separation showed that all of the PW4 blended membranes possessed dye rejection greater than 86% and 96% for RY160 and RG19, respectively. The reusability test using bovine serum albumin (BSA) protein and RG19 dye solutions in five cycle experiments presented good reproductivity of the PW4 blended membranes. The PES membrane containing 1 wt% of PW4 nanoparticles showed the highest flux recovery ratio (75%) as well as reduced irreversible fouling ratio (8%) through BSA protein filtration.

Non-Selective Cation Currents Mediated by Cx43 Hemichannel-P2X4 Receptor Signaling Pathway in Rat Atrial Myocytes under Shear Stress

Cardiac myocytes are exposed to shear stress under physiological conditions and hemodynamic disturbances. Shear stress has been thought to trigger two distinct global Ca2+ waves in atrial myocytes through autocrine activation of P2X4 receptor (P2X4R) and P2Y1-receptor (P2Y1R) via connexin 43 (Cx43)-mediated ATP release. In this study, we examined whether such shear stress-triggered Cx43-ATP-P2 receptor signaling generates depolarizing currents in atrial myocytes. Whole-cell patch clamp and dye-flux assays were used with genetic and pharmacological interventions in rat atrial myocytes and HL-1 cells. We found that shear stress activated a non-selective inward cation (Cs+) current (IS,Cs) at resting potential which was eliminated by Cx43 blockade using siRNA, antibodies, carbenoxolone or La3+. IS,Cs was enhanced by removal of external Ca2+, whereas internal Ca2+ buffering suppressed IS,Cs. Hemichannel-mediated dye (calcein red-orange) flux was induced by shear stress. This response was augmented by removing external Ca2+ but was not affected by pannexin blocker (probenecid). The shear-activated current was significantly reduced when Cs+ was replaced with NMDG+, and this was enhanced by quinine and suppressed by La3+. P2X4R antagonists (5-BDBD and PSB-12054), P2XR-blocker (iso-PPADS) and anti-P2X4R antibodies each blocked IS,Cs by approximately 50%. About 25% of IS,Cs was suppressed by P2Y1R inhibitor (MRS2179) and/or transient receptor potential melastatin 4 blocker (9-phenanthrol). P2X4R, but not P2X5R, was co-localized with Cx43 at the cell ends. P2X4R-dependent IS,Cs was augmented in atrial myocytes from hypertrophied rat hearts by short-term aortic constriction. Our data suggest that shear stress triggers Cx43 hemichannels to gate P2X4Rs in their vicinity. This shear stress signaling may play an important role in membrane depolarization at negative potentials and in atrial remodeling under increased afterload.

Design, assembly, and characterization of membrane-spanning DNA nanopores.

DNA nanopores are bio-inspired nanostructures that control molecular transport across lipid bilayer membranes. Researchers can readily engineer the structure and function of DNA nanopores to synergistically combine the strengths of DNA nanotechnology and nanopores. The pores can be harnessed in a wide range of areas, including biosensing, single-molecule chemistry, and single-molecule biophysics, as well as in cell biology and synthetic biology. Here, we provide a protocol for the rational design of nanobarrel-like DNA pores and larger DNA origami nanopores for targeted applications. We discuss strategies for the pores' chemical modification with lipid anchors to enable them to be inserted into membranes such as small unilamellar vesicles (SUVs) and planar lipid bilayers. The procedure covers the self-assembly of DNA nanopores via thermal annealing, their characterization using gel electrophoresis, purification, and direct visualization with transmission electron microscopy and atomic force microscopy. We also describe a gel assay to determine pore-membrane binding and discuss how to use single-channel current recordings and dye flux assays to confirm transport through the pores. We expect this protocol to take approximately 1 week to complete for DNA nanobarrel pores and 2-3 weeks for DNA origami pores.

Halloysite nanotube blended nanocomposite ultrafiltration membranes for reactive dye removal.

In this paper, ultrafiltration (UF) flat sheet membranes were manufactured by introducing two diverse halloysite nanotubes (HNT) size (5 μm and 63 μm) and five different (0, 0.63, 1.88, 3.13, 6.30 wt %) ratios by wet phase inversion. Some characterization methods which are contact angle, zeta potential, viscosity, scanning electron microscopy (SEM) and Young's modulus measurements were used for ultrafiltration membranes. Synthetic dye waters which were Setazol Red and Reactive Orange were used for filtration performance tests. These dye solutions were filtered in three different pH conditions and three different temperature conditions for pH and temperature resistance to understand how flux and removal efficiency change. The best water permeability results were obtained as 190.5 LMH and 192 LMH, for halloysite nanotubes (HNT) sizes of 5 μm and 63 μm respectively. The best water and dye performance of UF membrane contains 1.88% w/w ratio of HNT, which showed increased water flux and dye flux of membranes according to different HNT concentrations including ultrafiltration membranes.

Revaprazan prevented indomethacin-induced intestinal damages by enhancing tight junction related mechanisms

Non-steroidal anti-inflammatory drugs (NSAIDs) are the most commonly prescribed medications for alleviating pain and inflammation but may cause gastrointestinal tract damage. Proton pump inhibitors (PPI) prevent NSAID-induced gastric damage but may aggravate intestinal damage via dysbiosis and intestinal permeability alteration. Currently, there is growing interest regarding the influence of potassium competitive acid blockers (PCAB) on NSAID-induced enteropathy. Here, we investigated the relative changes in indomethacin-induced enteropathy by combining indomethacin with pantoprazole (as PPI) or revaprazan (as PCAB). We examined intestinal permeability-related molecular changes in in vitro Caco-2 cell models and in an in vivo indomethacin-induced enteropathy rat model. Indomethacin alone or in combination with pantoprazole significantly increased relative lucifer yellow dye flux and decreased relative trans-epithelial electrical resistance and tight junction protein (TJP) expression compare to normal cells. In contrast, indomethacin combined with revaprazan significantly preserved TJPs compare to indomethacin-treated cells. MLC phosphorylation, Rho activation, and ERK activation responsible for TJP were significantly increased by indomethacin alone or a combination of indomethacin and pantoprazole but not by a combination of indomethacin and revaprazan. Intestinal damage scores significantly increased with indomethacin and pantoprazole combination but not with indomethacin and revaprazan combination. Indomethacin and pantoprazole combination significantly activated Rho-GTPase, p-MLC, and p-ERK but significantly decreased TJP expression. However, indomethacin and revaprazan combination significantly preserved TJPs and inactivated Rho-GTPase, MLC, and ERK. Hence, revaprazan rather than PPIs should be co-administered with NSAIDs to mitigate NSAID-induced intestinal damage.

Super hydrophilic composite membrane with photocatalytic degradation and self-cleaning ability based on LDH and g-C3N4

In this work, the layered double hydroxide @ graphitic nitrogen carbide (LDH@g-C3N4@PDA) composite photocatalysts were fabricated by dopamine modification method. Then, the LDH@g-C3N4@PDA and graphene oxide (GO) composites were assembled on PVDF membrane to construct the photocatalytic self-cleaning composite membrane. The prepared PVDF/LDH@g-C3N4@PDA/GO composite membrane has excellent performance in contaminant separation and photocatalytic degradation. The rejection rates of methylene blue (MB), rhodamine b (RhB), gasoline, diesel, and petroleum ether were 100%, 94.61%, 96.74%, 93.22%, and 92.35%,respectively. More importantly, under visible-light irradiation, the membrane could achieve continuous and simultaneous flow-through separation and degradation of dye in short time. The rejection rate and the flux of organic dye were 99.28% and 397.14 L•m−2h−1bar−1. The photocatalytic cycle experiment, which has been repeated 10 times, have also revealed the stability and high efficiency of PVDF/LDH@g-C3N4@PDA/GO membrane on account of its superior photocatalytic self-cleaning function. Therefore, this self-cleaning composite membrane would have a range of applications in wastewater treatment.

Pannexin 1 activation and inhibition is permeant-selective.

The large-pore channel pannexin 1 (Panx1) is expressed in many cell types and can open upon different, yet not fully established, stimuli. Panx1 permeability is often inferred from channel permeability to fluorescent dyes, but it is currently unknown whether dye permeability translates to permeability to other molecules. Cell shrinkage and C-terminal cleavage led to a Panx1 open-state with increased permeability to atomic ions (current), but did not alter ethidium uptake. Panx1 inhibitors affected Panx1-mediated ion conduction differently from ethidium permeability, and inhibitor efficiency towards a given molecule therefore cannot be extrapolated to its effects on the permeability of another. We conclude that ethidium permeability does not reflect equal permeation of other molecules and thus is no measure of general Panx1 activity. Pannexin 1 (Panx1) is a large-pore membrane channel connecting the extracellular milieu with the cell interior. While several activation regimes activate Panx1 in a variety of cell types, the selective permeability of an open Panx1 channel remains unresolved: does a given activation paradigm increase Panx1's permeability towards all permeants equally and does fluorescent dye flux serve as a proxy for biological permeation through an open channel? To explore permeant-selectivity of Panx1 activation and inhibition, we employed Panx1-expressing Xenopus laevis oocytes and HEK293T cells. We report that different mechanisms of activation of Panx1 differentially affected ethidium and atomic ion permeation. Most notably, C-terminal truncation or cell shrinkage elevated Panx1-mediated ion conductance, but had no effect on ethidium permeability. In contrast, extracellular pH changes predominantly affected ethidium permeability but not ionic conductance. High [K+ ]o did not increase the flux of either of the two permeants. Once open, Panx1 demonstrated preference for anionic permeants, such as Cl- , lactate and glutamate, while not supporting osmotic water flow. Panx1 inhibitors displayed enhanced potency towards Panx1-mediated currents compared to that of ethidium uptake. We conclude that activation or inhibition of Panx1 display permeant-selectivity and that permeation of ethidium does not necessarily reflect an equal permeation of smaller biological molecules and atomic ions.

Microarray-based screening system identifies temperature-controlled activity of Connexin 26 that is distorted by mutations

Here, we show that human Connexin 26 (hCx26 or Cx26WT) hemichannel opening rapidly enables the transport of small molecules when triggered by temperature and by compensation of the Ca2+ blockade with EDTA. Point mutations within Cx26 were analysed by a novel optical microarray-based Lucifer Yellow uptake assay or by two electrode voltage clamp (TEVC) on frog oocytes to monitor simultaneous activities of channel proteins. Point mutations L90P, F161S, R184P or K188N influenced the temperature-dependent activity drastically. Since several mutations blocked trafficking, the temperature-dependent activity of the recombinant synthesized and purified wild-type Cx26WT and Cx26K188N hemichannel was tested by liposome flux assay (LFA) and on a microarray-based Lucifer Yellow uptake assay under warm conditions (>30 °C). The data from TEVC measurements and dye flux experiments showed that the mutations gave no or only a weak activity at increased temperature (>30 °C). We conclude that the position K188 in the Cx26WT forms a temperature-sensitive salt bridge with E47 whereas the exchange to K188N destabilizes the network loop- gating filter, which was recently identified as a part of the flexible Ca2+ binding site. We assume that the temperature sensitivity of Cx26 is required to protect cells from uncontrolled release or uptake activities through Cx26 hemichannels.

Incorporation of Electrochemically Exfoliated Graphene Oxide and TiO2 into Polyvinylidene Fluoride-Based Nanofiltration Membrane for Dye Rejection

In this work, the novel direct synthesis method of dimethylacetamide-based graphene oxide (GO) was performed through electrochemical exfoliation assisted by commercially available single-tail sodium dodecyl sulphate (SDS) surfactant. Then, the synthesised GO (SDS–GO) was incorporated into polyvinylidene fluoride (PVDF) solution to produce a nanofiltration (NF) membrane through the phase immersion method. The addition of GO into the preparation of membrane solution alters the membrane morphology and improves the hydrophilicity. TiO2 was also used as an additive for the NF membrane fabrication to further increase the membrane hydrophilicity. The fabricated PVDF/SDS–GO/TiO2 and PVDF/SDS–GO NF membranes were compared with pure PVDF membrane. Then, the fabricated NF membranes were tested for methylene blue (MB) rejection with 10 ppm MB concentration. On the basis of the dead-end cell measurement operated at the pressure of 2 bar, the PVDF/SDS–GO/TiO2 presents high MB rejection (92.76%) and the highest dye flux (7.770 L/m2 h). This dye flux value was sevenfold higher than that of pure PVDF membrane (1.146 L/m2 h) which was due to the utilisation of both GO and TiO2 that improved the membrane hydrophilicity as indicated by the lowest contact angle (64.0 ± 0.11°). High porosity (57.46%) also resulted in the highest water permeability (4.187 L/m2 h bar) of the PVDF/SDS–GO/TiO2 NF membrane.

Hybrid treatment of coagulation/flocculation process followed by ultrafiltration in TIO2-modified membranes to improve the removal of reactive black 5 dye

Many efforts have been made to minimize the polluting effect of wastewater containing dyes that are potentially toxic to the environment. The association of the coagulation/flocculation (CF) process, using saline extract of Moringa oleifera Lam (MO) seeds and subsequently ultrafiltration (UF) in TiO2-modified membranes was performed to remove reactive black 5 dye (10 ppm, RB5) from aqueous solution. The efficiency of the hybrid process was measured by the removal of the dye concentration, apparent color and fouling parameters. The membranes were successfully modified as supported by characterization methods of SEM, FTIR-ATR and WCA. The efficiency of the processes, when applied separately was low. However, after CF and subsequently the filtration in a TiO2-modified membrane both parameters assessed (dye concentration, apparent color) reached 100% of the removal rate. The modified membranes substantially improved permeate fluxes, for instance, after CF the dye flux for modified membrane enhanced around 49% compared with the flux in the pristine membrane. According to these results, the combination of methods was able to effectively remove RB5 dye, in addition to improving permeate fluxes and keeping fouling at low levels.

A novel photocatalytic membrane decorated with RGO‐Ag‐TiO2 for dye degradation and oil–water emulsion separation

AbstractBACKGROUNDMembrane separation is a promising process for treatment of dye and oily wastewater if the antifouling capacity and recyclability can be improved. In recent years, the development of photocatalytic materials has provided new methods for research into membrane technology.RESULTSIn this study, a novel photocatalytic membrane decorated with RGO‐Ag‐TiO2 nanomaterial was fabricated by simple vacuum filtration for degradation of dye and separation of oil–water. First, TiO2 nanowires were prepared for more effective photocatalysis, reduced graphene oxide (RGO)‐Ag‐TiO2 was fabricated by a facile hydrothermal reaction, then it was directly decorated on cellulose acetate (CA) membrane using polyethylene glycol and glutaraldehyde.CONCLUSIONThe as‐prepared photocatalytic membrane can simultaneously degrade dye and separate oil–water emulsions under visible‐light irradiation in a short time. The membrane has extremely high water flux (191 L m‐2 h‐1) and rejection rates (almost 100%) of dye–oil–water emulsion. More importantly, the photocatalytic membrane shows excellent antifouling capacity and recyclability, and retains relatively stable dye–oil–water permeation flux (about 27.5 L m‐2 h‐1) and high rejection rates (up to 99%) after six cycles of experiments under visible‐light irradiation. Overall, the photocatalytic membrane opens up new avenues for the treatment of wastewater. © 2017 Society of Chemical Industry