Membrane Permeability Coefficients Research Articles

Effect of pH in Coagulation Bath on Polysulfone-based Membrane Formation and Its Performance Characteristics

One of the factors that determine the formation of the membrane is the solution in the coagulation bath (non-solvent). In this study, the effect of pH treatment on the coagulation bath solution on membrane formation and its effect on membrane performance will be studied. The pH of the coagulation bath used was pH 1, 6.8 and 12. As the results, physically the three pH treatments produced the same white (opaque) membrane. Through morphological analysis, it appears that the three pH treatments produced an asymmetric membrane consisting of a top layer and a sublayer. The surface of the membrane with pH 1 treatment showed a denser surface than the pH 6.8 and pH 12 treatments. The results of the membrane performance characterization showed that the membrane permeability coefficient of the membrane with pH treatment was in the following order pH 1 < pH 12 < pH 6.8. While the value of the rejection coefficient showed that the membrane treated at pH 1 did not detect rejection because there was no permeate coming out, while at the treatment at pH 6.8 and 12, the rejection coefficient values were 74% and 76%, respectively.

Optimization of an in Silico Protocol Using Probe Permeabilities to Identify Membrane Pan-Assay Interference Compounds.

Membrane pan-assay interference compounds (PAINS) are a class of molecules that interact nonspecifically with lipid bilayers and alter their physicochemical properties. An early identification of these compounds avoids chasing false leads and the needless waste of time and resources in drug discovery campaigns. In this work, we optimized an in silico protocol on the basis of umbrella sampling (US)/molecular dynamics (MD) simulations to discriminate between compounds with different membrane PAINS behavior. We showed that the method is quite sensitive to membrane thickness fluctuations, which was mitigated by changing the US reference position to the phosphate atoms of the closest interacting monolayer. The computational efficiency was improved further by decreasing the number of umbrellas and adjusting their strength and position in our US scheme. The inhomogeneous solubility-diffusion model (ISDM) used to calculate the membrane permeability coefficients confirmed that resveratrol and curcumin have distinct membrane PAINS characteristics and indicated a misclassification of nothofagin in a previous work. Overall, we have presented here a promising in silico protocol that can be adopted as a future reference method to identify membrane PAINS.

Effect of a Membrane on Diffusion-Driven Turing Instability

Biological, physical, medical, and numerical applications involving membrane problems on different scales are numerous. We propose an extension of the standard Turing theory to the case of two domains separated by a permeable membrane. To this aim, we study a reaction–diffusion system with zero-flux boundary conditions on the external boundary and Kedem-Katchalsky membrane conditions on the inner membrane. We use the same approach as in the classical Turing analysis but applied to membrane operators. The introduction of a diagonalization theory for compact and self-adjoint membrane operators is needed. Here, Turing instability is proven with the addition of new constraints, due to the presence of membrane permeability coefficients. We perform an explicit one-dimensional analysis of the eigenvalue problem, combined with numerical simulations, to validate the theoretical results. Finally, we observe the formation of discontinuous patterns in a system which combines diffusion and dissipative membrane conditions, varying both diffusion and membrane permeability coefficients.

Preparation of Butadiene-Bridged Polymethylsiloxane/Ethylcellulose/1-Carboxymethyl-3-methylimidazolium Chloride Ternary Composite Membranes for Gas Separation.

Excessive CO2 emissions have resulted in global warming and are a serious threat to the life of people, various strategies have been implemented to cut carbon emissions, and one of them is the use of a gas separation membrane to capture CO2 effectively. In this experiment, the butadiene-bridged polymethylsiloxane (BBPMS)/ethyl cellulose (EC)/ionic liquid (IL) ternary composite membranes were prepared by EC as a substrate, BBPMS, and IL as additives in tetrahydrofuran under high-speed stirring and coated on the membrane. The membrane structure was characterized by a Fourier transform infrared spectrometer and scanning electron microscope, and the membrane properties were tested by a membrane tensile strength tester, thermal weight loss analyzer, and gas permeability meter. The results show that the surface of the ternary composite membrane is dense and flat with a uniform distribution, and the membrane formation, heat resistance, and mechanical properties are good. The permeability coefficient of the ternary composite membrane for CO2 reached 1806.03 Barrer, which is 20.00 times higher than that of the EC/IL hybrid matrix membrane. The permeability coefficient of O2 reached 321.01 Barrer, which is 19.21 times higher than that of the EC/IL membrane. When the doping amount of BBPMS is 70–80%, the O2/N2 gas permeation separation of the BBPMS/EC/IL ternary composite membrane is close to the Robertson 2008 curve. It is always known that in the gas separation process the membrane material is the most crucial factor. The success of this experiment points to a new direction for the preparation of new membrane materials.

Rational design of high power density “Blue Energy Harvester” pressure retarded osmosis (PRO) membranes using artificial intelligence-based modeling and optimization

The challenge in harvesting Salinity Gradient Power (SGP) through pressure retarded osmosis (PRO) requires design of high power density (PD) membranes and optimized process for operation. Recent studies show that for a feasible PRO operation the minimum net PD should be around 50 W/m2. In this study, a data-driven approach has been adopted for designing optimum membranes as well as operating conditions. 200 papers, from last decade, were extensively reviewed and 34 experimental research articles were shortlisted for possible data mining, to predict water flux (WF) and PD. Comprehensive screened/pre-processed data related to both membrane and process (16 inputs) was obtained from 18 articles amounting to 339 data points. Two artificial neural network (ANN) models were explored (i) Levenberg-Marquardt (ANN-LM), and (ii) Bayesian Regularization (ANN-BR) along with a combination of three different activation functions i.e., hyperbolic tangent sigmoid transfer function (Tan-Sigmoid), logarithmic sigmoid transfer function (Log-Sigmoid) in the input and output layers. Out of the six resulting combinations, the best performing combination was found to be Tan-Sigmoid activation function in both layers with ANN-BR model having an R2 value of 0.97 for WF and 0.98 for PD. Membrane properties like the type of membrane, thickness, and water permeability coefficient were found to be the major contributing factors for the prediction of WF while for PD, operating conditions such as applied pressure were found to play the major contributing factor (10–16 %). Optimization results yield a maximum WF of 147 LMH and PD of 87 W/m2. These results were compared with the solution diffusion (S-D) model.

Research on preparation and characterization of Ti-Ti5Si3 gradient composite porous material via in-situ reactive process

Gradient composite porous material can reach a high filtering accuracy with larger filtration flux, and the filter elements applied in separation equipment can enhance the filtration efficiency and reduce the energy consumption. Ti-Ti5Si3 gradient composite porous material was successfully prepared by in-situ reaction process with the raw materials of Ti powder and high purity quartz tablets. Microstructures and filtration properties prepared under different synthesized conditions have been studied, including the parameters of pressure sintering (additional loads and temperatures) and powder particle sizes. The synthesized granules on the membrane are well distributed with the size of ∼1.0 µm, and the thickness of the membrane is 3.0∼6.3 µm. The relative air permeability coefficient of porous membrane reduces raptly compared to the sample matrix due to the decrease of pore size. The all synthesized membranes show the presence of Ti and Ti5Si3 phases. There are two distinct layers observed in the membrane layers prepared by fine powder due to in-situ over-reaction.

The permeability of human red blood cell membranes to hydrogen peroxide is independent of aquaporins

Hydrogen peroxide (H2O2) not only is an oxidant but also is an important signaling molecule in vascular biology, mediating several physiological functions. Red blood cells (RBCs) have been proposed to be the primary sink of H2O2 in the vasculature because they are the main cellular component of blood with a robust antioxidant defense and a high membrane permeability. However, the exact permeability of human RBC to H2O2 is neither known nor is it known if the mechanism of permeation involves the lipid fraction or protein channels. To gain insight into the permeability process, we measured the partition constant of H2O2 between water and octanol or hexadecane using a novel double-partition method. Our results indicated that there is a large thermodynamic barrier to H2O2 permeation. The permeability coefficient of H2O2 through phospholipid membranes containing cholesterol with saturated or unsaturated acyl chains was determined to be 4 × 10−4 and 5 × 10−3 cm s−1, respectively, at 37 °C. The permeability coefficient of human RBC membranes to H2O2 at 37 °C, on the other hand, was 1.6 × 10−3 cm s−1. Different aquaporin-1 and aquaporin-3 inhibitors proved to have no effect on the permeation of H2O2. Moreover, human RBCs devoid of either aquaporin-1 or aquaporin-3 were equally permeable to H2O2 as normal human RBCs. Therefore, these results indicate that H2O2 does not diffuse into RBCs through aquaporins but rather through the lipid fraction or a still unidentified membrane protein.

Preparation and Gas Separation Performance of Polysulfone Mixed Matrix Membrane

As an economical, environmentally friendly, and highly efficient separation technology, membrane separation is a popular research topic in the field of separation. Organic polymer materials have attracted considerable attention in membrane separation because of their controllable preparation processes, simple modification method, and high toughness. Taking polysulfone (PSF) as the substrate of gas separation membrane, we prepared the mixed matrix membrane jointly by using the solution casting method and by adding graphene oxide (GO) and carbon nanotubes (CNTs). On this basis, the permeability of the membrane for CO2 and N2 and the permeability coefficient of the mixed gas were studied. With the addition of CNTs and GO, the permeability of gas was significantly improved. At 0.2 MPa, permeability of CO2 increased from 553 Barrer to 975 Barrer, and permeability of N2 increased from 536 Barrer to 745 Barrer. The max ideal separation coefficient of CO2 and N2 is 1.94 at 0.1 MPa. Increasing of the content of carbon nanotubes can significantly improve the permeability coefficient of CO2, while the change of inlet side pressure has a great impact on the permeability coefficient of N2. At 0.1 MPa, when the ratio of CNTs to GO was 5 : 1, the ideal permeability coefficient of CO2/N2 was 1.94, whereas the ideal permeability coefficient of PSF membrane was 1.46. The above results of PSF/GO/CNT mixed matrix membrane lay a theoretical foundation for industrial application.

Emerging Designs of Aggregation-Induced Emission Agents for Enhanced Phototherapy Applications

Emerging Designs of Aggregation-Induced Emission Agents for Enhanced Phototherapy Applications

Diffusion and Osmotic Permeability of Ion Exchange Membrane MK-40 Using Sodium Chloride Solution

Cation exchange membrane (MK-40) is a commercial membrane with a fixed group that is an important part of the electrodialysis (ED) process. Sodium chloride (NaCl) diffusion and osmotic permeability for MK-40 was studied. A cell containing two compartments was used to analyse the properties of the MK-40 membrane fixed between them. Furthermore, the influence of temperature, NaCl concentration, and operating time on MK-40 properties was investigated. The results showed that the highest diffusion permeability coefficient of NaCl was 7.37×10-9 (m2/s), and the maximum osmotic permeability coefficient of distilled water was 43.8×10-9 (m2/s) at NaCl solution concentration of 0.1 M and 50oC. Generally, the permeability was constant beyond 60 min of operational time. Additionally, the minimum diffusion permeability coefficients of the MK-40 membrane fell by about 22% over time when the concentration of NaCl solution was 1 M at 25oC. To conclude, membrane properties in the ED process depend on the two electrodes (a cathode and an anode), without the diffusion of salts particles. Meanwhile, the most important properties of cation exchange membranes (CEMs) used in electrodialysis are increased membrane efficiency when water and salts transport decrease through CEMs, which leads to a decrease in energy consumption. Thus, the MK-40 membrane showed a good properties due to its low diffusion permeability for concentrated NaCl solution at elevated temperatures and minimum reduction in diffusion permeability of concentrated NaCl solution over time.

Prediction of permeability across intestinal cell monolayers for 219 disparate chemicals using in vitro experimental coefficients in a pH gradient system and in silico analyses by trivariate linear regressions and machine learning

For medicines, the apparent membrane permeability coefficients (Papp) across human colorectal carcinoma cell line (Caco-2) monolayers under a pH gradient generally correlate with the fraction absorbed after oral intake. Furthermore, the in vitro Papp values of 29 industrial chemicals were found to have an inverse association with their reported no-observed effect levels for hepatotoxicity in rats. In the current study, we expanded our influx permeability predictions for the 90 previously investigated chemicals to both influx and efflux permeability predictions for 207 diverse primary compounds, along with those for 23 secondary compounds. Trivariate linear regression analysis found that the observed influx and efflux logPapp values determined by in vitro experiments significantly correlated with molecular weights and the octanol–water distribution coefficients at apical and basal pH levels (pH 6.0 and 7.4, respectively) (apical to basal, r = 0.76, n = 198; and basal to apical, r = 0.77, n = 202); the distribution coefficients were estimated in silico. Further, prediction accuracy was enhanced by applying a light gradient boosting machine learning system (LightGBM) to estimate influx and efflux logPapp values that incorporated 17 and 19 in silico chemical descriptors (r = 0.83–0.84, p < 0.001). The determination in vitro and/or prediction in silico of permeability coefficients across intestinal cell monolayers of a diverse range of industrial chemicals/food components/medicines could contribute to the safety evaluations of oral intakes of general chemicals in humans. Such new alternative methods could also reduce the need for animal testing during toxicity assessment.

Data-driven equation for drug-membrane permeability across drugs and membranes.

Drug efficacy depends on its capacity to permeate across the cell membrane. We consider the prediction of passive drug-membrane permeability coefficients. Beyond the widely recognized correlation with hydrophobicity, we additionally consider the functional relationship between passive permeation and acidity. To discover easily interpretable equations that explain the data well, we use the recently proposed sure-independence screening and sparsifying operator (SISSO), an artificial-intelligence technique that combines symbolic regression with compressed sensing. Our study is based on a large in silico dataset of 0.4 × 106 small molecules extracted from coarse-grained simulations. We rationalize the equation suggested by SISSO via an analysis of the inhomogeneous solubility-diffusion model in several asymptotic acidity regimes. We further extend our analysis to the dependence on lipid-membrane composition. Lipid-tail unsaturation plays a key role but surprisingly contributes stepwise rather than proportionally. Our results are in line with previously observed changes in permeability, suggesting the distinction between liquid-disordered and liquid-ordered permeation. Together, compressed sensing with analytically derived asymptotes establish and validate an accurate, broadly applicable, and interpretable equation for passive permeability across both drug and lipid-tail chemistry.

Nanoporous Membranes Prepared from Homogeneous Lamellar Structure Developed via Biaxial Melt‐Drawing of Ultra‐High Molecular Weight Polyethylene/Normal Molecular Weight Polyethylene Blend Films

AbstractBiaxial melt‐drawing of blend films composed of ultra‐high molecular weight polyethylene and normal molecular weight polyethylene produced a unique network structure consisting of 30‐nm thick homogeneous folded chain crystals. Subsequent biaxial solid‐drawing produced a nanoporous structure covering a large area of the membrane surface (120 mm × 120 mm). Effects of preparation parameters, including annealing and subsequent solid‐drawing, on resultant nanoporous morphology are also testified to achieve the desirable membrane. The higher gas permeability coefficients of the nanoporous membranes indicate that these nanopores are interconnected along the thickness direction. Despite such excellent porosity, the tensile strength reached 30 MPa, which is similar to that for the initial non‐porous film. Consistence of membrane porousness and robustness is highly desirable for various separation applications, including filtration, water purification, dialysis, and lithium‐ion batteries.

Physicochemical profile of new antifungal compound: pH-dependent solubility, distribution, permeability and ionization assay

Novel potential antifungal compound of 1,2,4-triazole class − 3,3‘-(piperazine-1,4-diyl)bis(2-(2,4-difluorophenyl)-1-(1H-1,2,4-triazol-1-yl)propan-2-ol) (S-119) - has been synthesized and characterized. Solubility in buffer solutions (pH 2.0 and 7.4), 1-octanol, n-hexane, and ethanol was measured by the isothermal saturation method in the temperature range (293.15–313.15 K). The following order of the solubility was revealed: ethanol > buffer pH 2.0 > 1-octanol > buffer pH 7.4 > n-hexane. The solubility was correlated by the Van’t Hoff and Apelblat equations. The Hansen solubility parameters were applied to solubility evaluation and demonstrated the consistency with the experimental data. The thermodynamic parameters of solubility and transfer processes were calculated and discussed in view of solute–solvent interactions. The temperature dependences of the distribution coefficients of S-119 in 1-octanol/buffer and n-hexane/buffer (pH 2.0 and 7.4) two-phase systems were obtained and considered from the thermodynamic point. The ΔlogD parameter determined from the distribution experiment clearly demonstrated the preference of lipophilic delivery pathways for S-119 in the biologic media and unfavorable transition to the non-polar regions. Membrane permeability coefficient of S-119 was determined and evaluated with the assistance of the respective parameter for the structurally related drug fluconazole.

Graphene tube shaped photothermal layer for efficient solar-driven interfacial evaporation

In this paper, RGO and GTube membranes are prepared to be used as absorbers in solar-driven interfacial evaporation. The GTube membrane could gain evaporation rate of 1.44 kg·m−2·h−1 under 1200 W·m−2, which is 20% larger than the RGO membrane. To explore the mechanism, the SEM and TEM images, water contact angles are tested. It is revealing that the GTube membrane forms much more pores for steam diffusion. The GTube membrane shows 97% of optical absorption within wavelength ranges from 250 to 2200 nm, while the RGO membrane is lower than 80%, revealing the GTube membrane could gather most of the solar radiation. Last, the permeability coefficient of RGO and GTube membranes are calculated by CFD model. The permeability coefficient of GTube membrane is 2-fold larger than the RGO membrane. This work provides a sight to construct the hollow carbon materials for improving optical absorption and permeability coefficient in solar-driven interfacial evaporation.

Amino acid-functionalized metal organic framework with excellent proton conductivity for proton exchange membranes

Proton conduction is a ubiquitous fundamental phenomenon in biological systems. Biology has solved the problem of energy-related proton conduction, in which the exposed amino acids in the protein ordered channels play a key role in proton conduction. In this contribution, amino acids (glutamate, lysine, and threonine) were attached to metal organic framework (MOF) nanoparticles, which were incorporated into sulfonated polysulfone matrix forming bio-proton channels for the nanocomposite membranes. It is shown in the results that the amino acid-functionalized MOF can help to enhance the proton conductivity and the proton exchange membrane with glutamate-functionalized MOF demonstrate excellent proton conductivity of 0.212 S cm−1 at 80 °C and 100% relative humidity. Meanwhile, the methanol permeability coefficient of the nanocomposite membrane is reduced to 5.8 × 10−7 cm2 s−1. The nanocomposite membranes demonstrate excellent proton conductivity, dimensional stabilities, water absorption, and resistance to methanol performance. Therefore, this material is promising for fuel cells.

Detection of material-derived differences in the stiffness of egg yolk phosphatidylcholine-containing liposomes using atomic force microscopy

Naturally sourced phospholipids are used in many liposomal pharmaceuticals. The present report describes a method to detect the effects of different egg yolk phosphatidylcholines (EPCs) on liposomal physicochemical properties. Five EPC-containing liposomes were prepared using five different EPCs obtained from different suppliers. There was no significant difference in purity between each EPC. The stiffness of the liposomes was examined via atomic force microscopy (AFM) in relation to the liposomal membrane permeability coefficient of encapsulated calcein after gel filtration, which is indicative of liposomal stability including the release of a hydrophilic drug from a liposome. Although the size of the liposome and the encapsulation efficiency of calcein did not significantly change with the type of EPC used, the liposome stiffness was found to vary depending on the EPC used, and liposomes with a similar stiffness were found to show a similar membrane permeability to calcein. Our results indicate the usefulness of stiffness measurement, using AFM as the analytical method, to detect material-derived differences in EPC-containing liposomes that affect drug release from the liposomes. Because drug release is one of the most important liposomal functions, combining this method with other analytical methods could be useful in selecting material for the development and quality control of EPC-containing liposomes.

Synthesis and characterization of a crosslinked membrane based on sulfonated poly(aryl ether sulfone) and sulfonated polyvinyl alcohol applied in direct methanol fuel cells

Vinyl-terminated sulfonated poly (arylene ether sulfone) (VSPAES) and sulfonated polyvinyl alcohol containing vinyl group (VSPVA) have been prepared. The VSPVA and VSPAES were crosslinked by adding AIBN as initiator. The results of FT-IR and 1H-NMR indicated the existence of sulfonic acid groups and crosslinked structure in these crosslinked membranes. The microphase structures of the membranes are analyzed by SEM. The proton conductivities of membranes were above 10 mS cm−1, which indicated that it basically meet the needs of fuel cells. The methanol permeability coefficients of CSPAES membrane is 2.8 × 10–7 cm2 s−1, remarkably lower than neat SPAES (8.5 × 10–7 cm2 s−1) and Nafion117 (14.1 × 10–7 cm2 s−1). Moreover, the proton selecticity of CSPAES membrane is close to 2 times higher than that of Nafion 117 membrane. The crosslinked membrane showed better stability than the linear SPAES membrane.

Pilot-scale investigation of flowrate and temperature influence on the performance of hollow fiber forward osmosis membrane in osmotic concentration process

Forward osmosis (FO) relying on the osmotic pressure difference across semi-permeable membrane draws permeate by the effect of saline draw solution (DS) turning diluted and leaving the feed solution (FS) concentrated. However, the energy intensive step of DS recovery makes FO a challenging process. The energy benefit of FO emerges when recovery step is obviated and FO is applied as an osmotic concentration (OC) process. OC implementations for volume reduction are still at bench-scale and the investigation at larger scale is among the breakthroughs. In this paper, the performance of hollow fiber (HF) membrane in pilot-scale OC process for reducing volume of feed was investigated. The impact of operating conditions such as flowrates and temperature was evaluated. FS and DS flowrates of 1.35 and 0.35 L.min-1 respectively are optimum conditions with 75% feed recovery and 1.90 LMH water flux. Reverse solute flux increased at higher flowrates. Results indicated the role of high DS flowrate and temperature in improving the performance. DS flowrate of 0.35 L.min-1 at constant FS flow of 1.10 L.min-1 and 27 °C was most suitable for achieving 84.5% feed recovery and 1.82 LMH water flux. Above all, the long-term performance of OC pilot-plant was demonstrated through 48 h of continuous operation where stable flux trend at an average water flux of 1.66 LMH was successfully achieved. Lastly, the permeability coefficients of HF membrane were enhanced at higher temperature.

Experimental evidence and physiological significance of the ascorbate passive diffusion through the lipid bilayer

The diverse range of functions performed by ascorbate in many metabolic processes requires its effective redistribution between various aqueous body compartments. It is believed that this hydrophilic molecule needs protein transporters for crossing the biological membrane barriers. Any effective model reflecting the ascorbate distribution within the body requires bi-directional fluxes, but only the ascorbate transporters facilitating its intake by cells have been identified to date. The cellular efflux of this molecule still lacks proper mechanistic explanation, nevertheless data suggesting possible passive ascorbate transport recently appeared. In the paper, we provide experimental evidences that ascorbate associates efficiently with the lipid bilayer interface and slowly crosses its hydrophobic core. The measured logPmembrane/water and membrane permeability coefficient equal to 3 and 10−7 – 10−8 cm/s, respectively. The ascorbate passive diffusion across the lipid bilayer provides the missing element needed for the construction of a consistent physiological model describing the ascorbate local homeostasis. The model was effectively used for the construction of the mechanistic description of the processes, which facilitate the ascorbate homeostasis in the brain.