Increased Ion Transport Research Articles

#2909 Molecular mechanisms of early vascular damage in children with chronic renal failure

Abstract Background and Aims The risk of developing cardiovascular disease is exceedingly high in patients with chronic kidney disease (CKD), therapeutic options are limited. In order to develop specific therapies, a comprehensive molecular understanding of the underlying pathomechanisms is essential. Method Transcriptome and proteome analyses followed by pathway analyses (GO, GSEA) were performed from microdissected omental arterioles of 6 children with normal renal function and 8 children with CKD5 (median age 9.2 years), respective microproteomics were performed from laser microdissected endothelial layers. Key findings were validated independently by immunohistochemistry. Human endothelial umbilical vein cells (HUVEC) were exposed to plasma from children with normal renal function and children with CKD5. Tight junction (TJ) abundance was quantified in Transwells, ionic conductance by transendothelial resistance measurements and chromatin topology by Single Molecule Localization Microscopy (SMLM) followed by cluster/persistent homology analyses. The latter was compared to ion radiation induced chromatin re-organisation. Results Arteriolar lumen narrowing was already pronounced in children with CKD5 (lumen/vessel ratio; 0.58 vs. 0.76 in healthy individuals, p < 0.001), arteriolar intima and media thickness significantly increased. Biofunctions significantly regulated in CKD compared to controls at both transcriptome and proteome levels were immune response, chromatin organisation, actin cytoskeleton and TJ organization (FDR<0.25, p < 0.05). In independent cohorts of children with CKD5 (n = 20), the subendothelial space was infiltrated by CD68+ macrophages and endothelial histone2A abundance was reduced compared to children with normal renal function (n = 16). Repair foci at the places of DNA double strand breaks (DSB) visualized by yH2A.X were similar in both groups. HUVEC exposed to plasma from CKD5 children showed marked relaxation of H3K9 labeled heterochromatin compared to HUVEC exposed to plasma from children with normal renal function, and persistent homology analysis revealed CKD specific chromatin pattern. The CKD induced chromatin re-organisation differed from ion radiation induced DSB repair. Polarized endothelial cells exposed to plasma from CKD5 children had increased ion transport compared to cells exposed to plasma from healthy donors. Endothelial cell membrane abundance of the sealing TJ protein claudin-5 and of zonula occlundens-1, which links TJ to the actin cytoskeleton, was reduced by uremic plasma, TNFα and carbonyl stress. Co-incubation with histidine dipeptides and AlaGln ameliorated the loss of endothelial barrier function. Conclusion CKD5 leads to complex molecular pathomechanisms and functional alterations particularly including the immune response, chromatin re-organization and endothelial barrier dysfunction already in young children. Dipeptides represent potential therapeutic agents to protect the endothelial barrier function.

Deletion of Kcnj16 altered transcriptomic and metabolomic profiles of Dahl salt-sensitive rats

The essential role of inwardly rectifying K+ Channel Kir5.1 (encoded by the Kcnj16 gene) in renal salt handling and blood pressure control has been demonstrated in both human and animal models. However, the underlying mechanisms are still not fully understood. Here, we aimed to integrate transcriptomics and metabolomics to profile the comprehensive changes of genes and metabolites under the deletion of Kcnj16 in the Dahl salt-sensitive (SS) rat background to identify novel mechanisms. For the transcriptomics profiling, we performed RNA-sequencing on kidney cortex tissue of Kcnj16 knockout (KO) and wild-type (WT) SS rats (N=5 per group). For the metabolomics profiling, we performed untargeted metabolomics of kidney cortex tissue, plasma, and urine of KO (N=6) and WT (N=5) rats. Transcriptomics analysis revealed over 6,000 differentially expressed genes in KO rats compared to WT rats, with renin Ren (the gene encoding renin) being the most upregulated gene. Consistent with the phenotype observed in the KO rats, ingenuity pathway analysis (IPA) based on the transcriptomic profile predicted reduced blood pressure and kidney damage and increased ion transport. Canonical pathway analysis suggested activation of metabolic-related pathways [e.g., xenobiotic metabolism, tricarboxylic acid (TCA) cycle, phenylalanine degradation, etc.] and suppression of immune responses-related pathways [e.g., pathogen-induced cytokine storm signaling pathway, macrophage classical activation signaling pathway, nuclear factor of activated T cells (NFAT) pathway, etc.] in KO rats. Untargeted metabolomic analysis suggested distinct metabolic profiles of plasma, urine, and kidneys between WT and KO rats, with 219, 790, and 31 differentially expressed metabolites identified in plasma, urine, and kidney in KO rats compared to WT rats. Canonical pathway analysis identified spermine and spermidine degradation pathways in both plasma and urine and taurine biosynthesis pathways in both urine and kidney. Integration analysis based on transcriptomic and metabolomic profiles suggested an altered TCA cycle, amino acid, and reactive oxygen species metabolism. In conclusion, besides significantly altered ion transport, our transcriptomics and metabolomics data suggest significant suppressed immune responses-related and altered metabolic-related pathways in SS rats lacking Kir5.1, which provides new insights into the underlying mechanisms of the regulation of blood pressure and renal function by Kir5.1. This work is supported by National Institutes of Health Grants R35 HL135749 and R01 DK135644 (to A.S.), Department of Veteran Affairs grant I01 BX004024 (to A.S.), the American Physiological Society Postdoctoral Fellowship (to B.X.) and the American Society of Nephrology Dimitrios G. Oreopoulos Research Fellowship Award (to L.V.D.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Molecular-scale interaction between sub-1 nm cluster chains and polymer for high-performance solid electrolyte

Organic-inorganic interface in composite solid electrolyte could lead to increased ion transport for solid-state lithium batteries; however, most inorganic fillers have much larger size than polymer chains, which results in severe aggregation of inorganic fillers and poor ionic conductivity. Herein, functional sub-1 nm inorganic cluster chains were integrated with polymer chains to fabricate composite solid electrolyte with enhanced ionic conductivity. Different from all other inorganic fillers, the sub-1 nm inorganic cluster chains with diameter <1 nm have similar size and geometry compared with polymer chains, exhibiting polymer-like solution properties. A transparent sub-1 nm inorganic filler/polymer mixed solution was generated to realize monodispersion of cluster chains as functional fillers in polymer matrix. Meanwhile, abundant oxygen vacancies on cluster chains interact with polymer chains and lithium salts at molecular-scale, which decreases the complexation of polymer segments with Li+ and promote the dissociation of lithium salts, thereby improving Li+ transport. As a result, the composite solid electrolyte exhibits high ionic conductivity (0.4 mS cm−1) and large mobile Li+ distribution (50.8 %). This work pushes the size of nanofillers down to <1 nm, which is a unique approach to the molecular-scale interaction between nanofillers and polymers to boost ion transport in solid electrolytes.

Ultrathin H-MXM as An "Ion Freeway" for High-Performance Osmotic Energy Conversion.

Nanofluidic membranes are currently being explored as potential candidates for osmotic energy harvesting. However, the development of high-performance nanofluidic membranes remains a challenge. In this study, the ultrathin MXene membrane (H-MXM) is prepared by ultrathin slicing and realize the ion horizontal transportation. The H-MXM membrane, with a thickness of only 3 µm and straight subnanometer channels, exhibits ultrafast ion transport capabilities resembling an "ion freeway". By mixing artificial seawater and river water, a power output of 93.6 Wm-2 is obtained. Just as cell membranes have an ultrathin thickness that allows for excellent penetration, this straight nanofluidic membrane also possesses an ultrathin structure. This unique feature helps to shorten the ion transport path, leading to an increased ion transport rate and improveS performance in osmotic energy conversion.

Temperature-responsive bioactive glass/polymer hybrids allow for tailoring of ion release.

Intelligent biomaterials react to their surrounding conditions, and hybrid materials are acknowledged for their remarkable customizability, achieved through the meticulous control of nanoscale interactions between organic and inorganic phases. Bioactive glasses (BG) are used clinically to regenerate bone due to their degradability, ion release, and capacity to stimulate the formation of new body tissue. In our study, we developed a core-shell hybrid system using sol-gel derived BG nano particles as the core and poly (N-isopropyl acrylamide) (PNIPAM) as the shell. This approach aims to combine the therapeutic ion release of BG with the temperature-responsive properties of PNIPAM. Our size analysis by dynamic light scattering at varying temperatures shows the formation of BG aggregates driven by the coil-to-globule transition of PNIPAM on the BG surface. This transition also affected the ion release from the core-shell system through an increase in ion transport through the porous hybrid network. Our study therefore illustrates the ability to adjust the dissolution properties of the core-shell system via surrounding temperature and, thus, control the release of Ca ions from the BG.

Engineering Block Copolymer-Derived Porous Carbon Nanofibers as Anodes for Sodium Ion Batteries

For decades, lithium-ion batteries have seen widespread usage in a variety of applications from consumer electronics such as smartphones to the more recent developments of electric vehicles. As the usage of lithium for batteries increases, one growing concern is the finite amount that could be found within the Earth’s crust. An alternative that is being considered is sodium-ion batteries due to how plentiful sodium is in the Earth’s crust and similar chemical properties to lithium. One of the main challenges of sodium-ion batteries is the development of anode materials because sodium does not intercalate well with graphite, which is one of the most used materials in lithium-ion batteries. One promising development for anode materials is the use of hard carbon derived from the pyrolysis of polymers such as polyacrylonitrile (PAN) which can have various morphologies and potential for doping. Our work will focus on carbon nanofibers which show high 1-dimensional transport capabilities. With the addition of a sacrificial material such as polymethylmethacrylate (PMMA) that will be removed entirely during the pyrolysis step, PAN/PMMA can be made into porous carbon nanofibers to further increase ion transport. When a PAN/PMMA blend is used, the pores are very random with a high degree of variation of pore characteristics, however studies have shown that the creation of a PAN-b-PMMA block copolymer would allow for more uniform pore structures. Our work intends to study the effects of pore structures on the electrochemical characteristics of porous carbon nanofiber anodes for sodium-ion batteries. The cycling stability data of coin cells made using hard carbon nanofibers derived from electrospun PAN (Nonporous), PAN/PMMA (Random Porous), and PAN-b-PMMA (Uniform Porous), shows their respective discharging specific capacities (mAh/g) at 0.1 A/g average at about 80, 116, and 175. A slight increase can be seen with the addition of random, nonuniform pores to the PAN hard carbon, however, with the highly uniform and controlled pores resulting from the pyrolysis of the PAN-b-PMMA block copolymer, a very significant increase in the discharging specific capacity can be seen.

Multiscale carbon - Based ion channel fiber membrane for efficient osmotic energy capture

The green energy generated by salinity gradient at the river-sea junction can be captured by Reverse Electrodialysis (RED) technology. The ion migration in the energy conversion process occurs in the narrow ion channel inside the permeable membrane of the core component. In practical applications, membrane used for osmotic energy conversion needs to meet the necessary conditions such as effective nano-channels, sufficient surface charges, large-scale preparation and stable energy output. It is challenging to achieve all of these requirement at the same time and calls for an exquisite design of the permeable membrane. Herein, we demonstrate an ion channel membrane regulated by a carbon-based membrane with hierarchical channels for efficient osmotic energy conversion. Porous carbon (PC) nanosheets with high porosity and high modulus are filled into carbon nanofibers (CNFS)/graphene oxide (GO) composite membrane, increasing ion transport channels and providing additional space charge to improve ion selectivity. The power output from PC@GO/CNFs membranes modified with nano-porous carbon reaches 4.3 W·m−2. In addition, the ion-selective membrane obtained by this strategy has the advantages of simple process, adjustable area and good stability. This simple strategy is one of the feasible paths for infiltration to be collected effectively. Ion-selective membrane is the key component for osmotic energy conversion.

Strategies of NaCl Tolerance in Saline-Alkali-Tolerant Green Microalga Monoraphidium dybowskii LB50.

Studying how freshwater cells modify metabolism and membrane lipids in response to salt stress is important for understanding how freshwater organisms adapt to salt stress and investigating new osmoregulatory ways. Physiological, biochemical, metabolic, and proteomic analyses were applied in a novel saline-alkali-tolerant microalga Monoraphidium dybowskii LB50 under different NaCl concentrations. Cells adopt a variety of strategies to adapt to salt stress, including increasing ion transport and osmolytes, regulating cell cycle and life history, and accumulating triacylglycerol (TAG). A large number of metabolic activities point to TAG accumulation. With increasing NaCl concentration, the C resource for TAG accumulation went from photosynthetically fixed C and a small amount of lipid remodeling to macromolecule degradation and a mass of lipid remodeling, respectively. The energy for TAG accumulation went from linear electron transfer and oxidative phosphate pentose pathway to cyclic electron flow, substrate phosphorylation, oxidation phosphorylation, and FA oxidation. Additionally, digalacturonic acid and amino acids of the N-acetyl group, which usually were the osmotica for marine organisms, were important for M. dybowskii LB50. Freshwater organisms evolved many biological ways to adapt to salt stress. This insight enriches our understanding of the adaptation mechanisms underlying abiotic stress.

Effects of bipolar plate flow channel configuration on thermal-electric performance of direct ammonia solid oxide fuel cell: Part I - Numerical study of channel section geometry

Direct ammonia SOFCs (DA-SOFCs) are numerical studied to investigate the effects of bipolar plate flow channel configuration on thermal-electric performance. This study establishes a planar DA-SOFC model and investigates triangular, quadrangular, and oval flow channel configurations’ impact using numerical simulations. Results reveal oval cross-section channels outperform trapezoidal and triangular ones, achieving power density increases of 15.6%, 16.1%, and 18.6%, respectively, compared to rectangular channels at 0.6V. The oval channel displays superior velocity and vorticity, enhancing mass transfer between the main flow and reaction zone. Increasing channel width reduces rib width, promoting O2 distribution, temperature improvement via exothermic reactions, NH3 decomposition into H2, and improved cell performance. Rib width increase shortens diffusion and reduces concentration polarization, but increases ion transport and ohmic polarization. A theoretical formula for optimal rib width (Wrib0) to minimize polarization loss is provided. These findings offer a comprehensive reference for optimizing DA-SOFC design.

Stray current induced chloride ion transport and corrosion characteristics of cracked ultra-high performance concrete

Ultra-high-performance concrete (UHPC) is a strong, durable, and corrosion-resistant material that is poised to revolutionize construction in complex environments, such as the deep sea and underground. However, the formation of cracks of UHPC during service and the occurrence of stray currents in underground stations and tunnels greatly accelerate the transport of chloride ions, posing a threat to the safety of underground construction. Here, we used the rapid chloride migration (RCM) method to study the effect of stray current in cracked UHPC. Essentially, electric field accelerates chloride ion transport in cracks by increasing ion transport in the uncracked zone. The wider the crack, the more severe the corrosion of steel fibers, which affects the pore structure of UHPC and leads to an increase in the diffusion coefficient in the uncracked area. In addition, area normalization was employed to precisely monitor the chloride ion concentration in the cracks, which was validated by numerical simulations. Finally, microscopy and atomic force microscopy (AFM) showed that larger crack widths led to deeper corrosion and more severe steel fiber corrosion in UHPC. These results have important implications for the durability design of UHPC structures in stray current environments.

The ClC-2 Chloride Channel Activator, Lubiprostone, Improves Intestinal Barrier Function in Biopsies from Crohn's Disease but Not Ulcerative Colitis Patients.

The prostone analog, lubiprostone, is approved to manage constipation-predominant irritable bowel syndrome. Lubiprostone also protects intestinal mucosal barrier function in animal models of colitis. The aim of this study was to determine if lubiprostone improves barrier properties in isolated colonic biopsies from Crohn's disease (CD) and ulcerative colitis (UC) patients. Sigmoid colon biopsies from healthy subjects, CD and UC patients in remission, and CD patients with active disease were mounted in Ussing chambers. Tissues were treated with lubiprostone or vehicle to determine the effects on transepithelial electrical resistance (TER), FITC-dextran 4kD (FD4) permeability, and electrogenic ion transport responses to forskolin and carbachol. Localization of the tight junction protein, occludin, was determined by immunofluorescence. Lubiprostone significantly increased ion transport across control, CD and UC remission biopsies but not active CD. Lubiprostone selectively improved TER in both CD remission and active disease biopsies but not in control or UC biopsies. The improved TER was associated with increased membrane localization of occludin. Lubiprostone selectively improved barrier properties of biopsies from CD patients vs. UC and independent of an ion transport response. These data indicate that lubiprostone has potential efficacy in improving mucosal integrity in Crohn's disease.

Structural supercapacitor electrolytes based on cementitious composites containing recycled steel slag and waste glass powders

Incorporating solid wastes into cement-based materials is beneficial for the waste disposal and the conservation of natural resources. In this study, cement-based electrolyte incorporated with recycled steel slag powder (SSP) and waste glass powder (GP) was proposed as a potential candidate for assembling structural supercapacitor cells (SSCs) with multi-functionality. Compared with pure cement devices, the 28-day conductivity and areal capacitance of the SSCs containing SSP and GP increased by up to 112% and 84%, respectively, at a current density of 0.1 mA cm−2. On the one hand, the addition of SSP and GP increased the pore volume in the cement-based electrolyte, which in turn resulted in more paths for ion transport. On the other hand, the presence of SSP and GP increased the concentration of major ions, such as Na+ and OH−, in pore solution. Both the increased ion transport paths and the improved ion concentration contributed substantially to the enhancement of the energy storage performances of the SSCs. At 28 days, an additional incorporation of 10% GP made up for the strength loss caused by SSP as an appropriate amount of GP with high pozzolanic activity resulted in an increased amount of C-S-H product, a reduction of porosity, and a denser microstructure. The proposed SSCs containing the cement-based electrolyte with cement partially replaced by 20% SSP and 10% GP is competitive for the development of green building energy storage devices.

Electrochemical Double-Layer Capacitor based on Carbon@ Covalent Organic Framework Aerogels.

High energy demand results in comprehensive research of novel materials for energy sources and storage applications. Covalent organic frameworks (COFs) possess appropriate features such as long-range order, permanent porosity, tunable pore size, and ion diffusion pathways to be competitive electrode materials. Herein, we present a deep electrochemical study of two COF-aerogels shaped into flexible COF-electrodes (ECOFs) by a simple compression method to fabricate an electrochemical double-layer capacitor (EDLC). This energy storage system has considerable interest owing to its high-power density and long cycle life compared with batteries. Our result confirmed the outstanding behavior of ECOFs as EDLC devices with a capacity retention of almost 100 % after 10 000 charge/discharge cycles and, to our knowledge, the highest areal capacitance (9.55 mF cm-2 ) in aqueous electrolytes at higher scan rates (1000 mV s-1 ) for COFs. More importantly, the hierarchical porosity observed in the ECOFs increases ion transport, which permits a fast interface polarization (low τ0 values). The complete sheds light on using ECOFs as novel electrode material to fabricate EDLC devices.

Electrochemical Double‐Layer Capacitor based on Carbon@ Covalent Organic Framework Aerogels

AbstractHigh energy demand results in comprehensive research of novel materials for energy sources and storage applications. Covalent organic frameworks (COFs) possess appropriate features such as long‐range order, permanent porosity, tunable pore size, and ion diffusion pathways to be competitive electrode materials. Herein, we present a deep electrochemical study of two COF‐aerogels shaped into flexible COF‐electrodes (ECOFs) by a simple compression method to fabricate an electrochemical double‐layer capacitor (EDLC). This energy storage system has considerable interest owing to its high‐power density and long cycle life compared with batteries. Our result confirmed the outstanding behavior of ECOFs as EDLC devices with a capacity retention of almost 100 % after 10 000 charge/discharge cycles and, to our knowledge, the highest areal capacitance (9.55 mF cm−2) in aqueous electrolytes at higher scan rates (1000 mV s−1) for COFs. More importantly, the hierarchical porosity observed in the ECOFs increases ion transport, which permits a fast interface polarization (low τ0 values). The complete sheds light on using ECOFs as novel electrode material to fabricate EDLC devices.

Osteopontin (OPN)/Secreted Phosphoprotein 1 (SPP1) Binds Integrins to Activate Transport of Ions Across the Porcine Placenta.

Fetal-placental development depends on a continuous and efficient supply of nutrients from maternal blood that are acquired by exchange through the placenta. However, the placenta is a low permeability barrier, and effective transport of substances depends on specific transport mechanisms. Active transport requires that ions or nutrients be moved against an electrical and/or concentration gradient. In pigs, active transport of ions occurs across the chorioallantois placenta to produce an electrochemical gradient that changes throughout gestation. The aim of this study was to utilize Ussing chambers to detect regulation of ion transport across the porcine chorioallantois by a factor(s) within the uterine-placental environment of pigs. For the measurement of transchorioallantoic voltage potential as an index of ion transport across the placenta, pieces of chorioallantoic tissue from Day 60 of gestation were mounted into the cassettes of Ussing chambers, and treatments were added to the mucasal side of the tissue. Treatments included: (1) media incubated with Day 60 chorioallantois (placenta-conditioned media); (2) osteopontin/secreted phosphoprotein 1 (OPN/SPP1) purified from cow's milk; (3) placenta-conditioned media from which OPN/SPP1 was removed; and (4) recombinant rat OPN with an intact RGD integrin binding sequence or a mutated RAD sequence. Ouabain was added to both sides of the chamber. Immunofluorescence was utilized to localize beta 3 integrin, aquaporin 8 and OPN/SPP1 in porcine placental tissues, and OPN/SPP1 within porcine lung, kidney and small intestine. Day 60 chorioallantoic membranes had greater transepithelial voltage in the presence of porcine placenta-conditioned media, indicating that a molecule(s) released from the placenta increased ion transport across the placenta. OPN/SPP1 purified from cow's milk increased ion transport across the placenta. When OPN/SPP1 was removed from placenta-conditioned media, ion transport across the placenta did not increase. Recombinant rat OPN/SPP1 with a mutated RGD sequence that does not bind integrins (RAD) did not increase ion transport across the placenta. Ouabain, an inhibiter of the sodium-potassium ion pump, ablated ion transport across the placenta. The present study documents a novel pericellular matrix role for OPN/SPP1 to bind integrins and increase ion transport across the porcine chorioallantoic placenta.

Increased ion transport and high-efficient osmotic energy conversion through aqueous stable graphitic carbon nitride/cellulose nanofiber composite membrane

Increased attention has evoked on the utilization of renewable energy, particularly osmotic power as a potential solution to the energy crisis and environmental pollution. Herein, we fabricate graphitic carbon nitride (g-C3N4)/cellulose nanofiber (CNF) composite membranes with tailored lamellar nanochannels for capturing osmotic energy from salinity gradients. Composite membranes exhibiting charge-governed ion conductivity were prepared via co-homogenization of g-C3N4 with CNF and vacuum filtration. Ion conductivity was efficiently modulated by fine-tuning the charge density through controlling the weight content of CNF in the composite membranes. Higher ion conductivity of 0.014 S cm−1 at low concentrations (<10−2 M KCl) was achieved due to the increased charge density of the lamellar nanochannels and the excellent aqueous stability of the membranes. We demonstrate the potential of the composite membranes in nanofluidic osmotic energy conversion, displaying thermo-enhanced power output performance. This work could inspire new designs of cellulose-based nanofluidic devices for improved osmotic energy conversion.

Features of feed concentration and temperature effects on membranes operation in electrodialysis systems – a review

Electrodialysis (ED) is a significant method in saline water desalination and industrial wastewater treatment. Ion exchange membranes (IEMs) are an important part of the electrodialysis process. An ion-exchange membrane is a semipermeable membrane that transports ions through an oppositely charged membrane and blocks the passage of a co-ion under an electric field. This review describes the effects of feed concentration and its operating temperature on different sides of IEMs in an electrodialysis system. The influence of feed solutions and temperature gradients on diffusion and osmatic membrane permeability was clarified. The distribution of feed concentration under thermostatic and thermodynamic conditions are also discussed. Temperature changes in ED systems may increase ion transport selectivity and charge separation efficiency. The rate of ions transport depends on the number of ions diffusion toward the membrane. To date, there are very few studies reporting diffusion and osmatic permeability of IEMs at high temperature.

Instilling Monovalent Selectivity in Cation Exchange Membranes By Molecular Layer Deposition

Desalination is becoming a vital part of the solution to water scarcity with a current worldwide desalination capacity of approx. 100 million m3/day, which is expected to grow by 40% by 2030. In 2019, 29% of the global desalination capacity was of brackish and river water (500-20000 ppm TDS). Most (98%) of the brackish water nowadays is desalinated by reverse osmosis (RO) which completely deprives the permeate of Mg2+ and Ca2+. Both are critical nutrients needed to sustain human health and agriculture. Replenishing these divalent ions to the desalinated water increases the cost and complexity of the overall process and decreases its sustainability and economic attractiveness. Electrodialysis is energetically more efficient than RO for desalination of brackish water, and using monovalent selective membranes—membranes that enable monovalent ions passage, but retains divalent ions—offer a potential solution to preserve the nutrients in the permeate. However, current methods for instilling ion selectivity uses large macromolecular building blocks to form the selective layer, which increases ion transport resistance and hence the energy demand and cost of selective electrodialysis. To disrupt the resistance-selectivity trade-off, a method for uniformly depositing an ultrathin and highly charged selective layer is needed.While low-temperature atomic layer deposition is a suitable method for depositing ultrathin metal oxides on membranes, the elastic mismatch between metal oxides and polymers hinders the stability of the selective layer. Instead, we used molecular layer deposition of alucones to resolve the elastic mismatch. We show that the electrostatic charge of alucone surface leads to monovalent selectivity values on par with commercial membranes, but with only a marginal increase in resistivity.

Epigenome editing of the CFTR-locus for treatment of cystic fibrosis

BackgroundMechanisms governing the diversity of CFTR gene expression throughout the body are complex. Multiple intronic and distal regulatory elements are responsible for regulating differential CFTR expression across tissues. MethodsDrawing on published data, 18 high-priority genomic regions were identified and interrogated for CFTR-enhancer function using CRISPR/dCas9-based epigenome editing tools. Each region was evaluated by dCas9p300 and dCas9KRAB for its ability to enhance or repress CFTR expression, respectively. ResultsMultiple genomic regions were tested for enhancer activity using CRISPR/dCas9 epigenome editing. dCas9p300 mediates a significant increase in CFTR mRNA levels when targeted to the promoter and a region 44 kb upstream of the transcriptional start site in a CFTR-low expressing cell line. Multiple gRNAs targeting the promoter induced a robust increase in CFTR protein levels. In contrast, dCas9KRAB-mediated repression is much more robust with 10 of the 18 evaluated genomic regions inducing CFTR protein knockdown. To evaluate the therapeutic efficacy of modulating CFTR gene regulation, dCas9p300 was used to induce elevated levels of CFTR from the endogenous locus in ΔF508/ΔF508 human bronchial epithelial cells. Ussing chamber studies demonstrated a synergistic increase in ion transport in response to CRISPR-induced expression of ΔF508 CFTR mRNA along with VX809 treatment. ConclusionsCRISPR/dCas9-based epigenome-editing provides a previously unexplored tool for interrogating CFTR enhancer function. Here, we demonstrate that therapeutic interventions that increase the expression of CFTR may improve the efficacy of CFTR modulators. A better understanding CFTR regulatory mechanisms could uncover novel therapeutic interventions for the development of cystic fibrosis therapies.

Mechanisms of Ion Transport Across the Mouse Retinal Pigment Epithelium Measured In Vitro.

PurposeTo examine ion transport across the mouse retinal pigment epithelium (RPE), measured by the short-circuit current (ISC) and transepithelial resistance (TER).MethodsSheets of RPE from mice (C57BL6/J) with retina, choroid, and sclera attached were mounted in Ussing chambers (0.031-cm2 aperture) and Krebs solution. The ISC and TER were recorded with voltage clamps. Receptors implicated in ion transport were blocked or stimulated by ligands applied to both sides.ResultsThe mean initial ISC was −12.0 ± 3.9 µA/cm2 (basolateral negative), and mean TER was 67.1 ± 8.0 ohm·cm2. RPE preparations remained stable for 3 hours, with ISC decreasing by 0.078 ± 0,033 µA/cm2/hr. Adenosine triphosphate (100 µM) increased ISC by 2.22 ± 0.41 µA/cm2 (P = 0.003). Epinephrine (100 µM) increased ISC by 1.14 ± 0.19 µA/cm2 (P = 0.011). Bumetanide (100 µM) reduced ISC by 1.72 ± 0.73 µA/cm2 (P = 0.027). Ouabain (1 mM) induced a biphasic response: an ISC increase from −7.9 ± 2.4 to −15.49 ± 2.12 µA/cm2 and then a decrease to −3.7 ± 2.2 µA/cm2. Ouabain increased TER by 15.3 ± 4.8 ohm·cm2. These compounds were added sequentially. Apical [K+]o at zero mM transiently increased ISC by 3.36 ± 1.06 µA/cm2. Ba++ decreased ISC from −10.4 ± 3.1 to −6.6 ± 1.8 µA/cm2 (P = 0.01). Ba++ reversed the K+-free response, with Isc decreasing further from −5.65 ± 1.24 to −3.37 ± 0.79 µA/cm2 (P = 0.029).ConclusionsThe ISC and TER can be recorded from the mouse RPE for 3 hours. Adrenergic and purinergic receptors affect murine RPE ion transport. Sodium–potassium adenosine triphosphatase plays a role in net ion transport across mouse RPE, and Na-K-2Cl cotransporter activity partly accounts for transepithelial ion transport. Mimicking light-induced changes, low subretinal [K+]o increases ion transport transiently, dependent on K+ channels.