Membranes

15 pages, 13477 KiB

Open AccessArticle

Regeneration of Exhausted Palladium-Based Membranes: Recycling Process and Economics

by Luigi Toro, Emanuela Moscardini, Ludovica M. Baldassari, Flavia Forte, Jacopo Coletta, Emma Palo, Vittoria Cosentino, Fabio Angelini, Alba Arratibel Plazaola, Francesca Pagnanelli and Pietro Altimari

Membranes 2022, 12(7), 723; https://doi.org/10.3390/membranes12070723 - 21 Jul 2022

Cited by 3 | Viewed by 1455

Abstract

The aim of the present work is the recycling treatment of tubular α-Al₂O₃-supported ceramic membranes with a Pd/Ag selective layer, employed in hydrogen production with integrated CO₂ capture. A nitric acid leaching treatment was investigated, and recovered ceramic [...] Read more.

The aim of the present work is the recycling treatment of tubular α-Al₂O₃-supported ceramic membranes with a Pd/Ag selective layer, employed in hydrogen production with integrated CO₂ capture. A nitric acid leaching treatment was investigated, and recovered ceramic supports were characterized, demonstrating their suitability for the production of novel efficient membranes. The main objective was the metal dissolution that preserved the support integrity in order to allow the recovered membrane to be suitable for a new deposition of the selective layer. The conditions that obtained a satisfactory dissolution rate of the Pd/Ag layer while avoiding the support to be damaged are as follows: nitric acid 3 M, 60 °C and 3.5 h of reaction time. The efficiency of the recovered supports was determined by nitrogen permeance and surface roughness analysis, and the economic figures were analysed to evaluate the convenience of the regeneration process and the advantage of a recycled membrane over a new membrane. The experimentation carried out demonstrates the proposed process feasibility both in terms of recycling and economic results. Full article

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16 pages, 8333 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

New Sustainable Multilayered Membranes Based on ZrVTi for Hydrogen Purification

by Stefano Fasolin, Simona Barison, Filippo Agresti, Simone Battiston, Stefania Fiameni, Jacopo Isopi and Lidia Armelao

Membranes 2022, 12(7), 722; https://doi.org/10.3390/membranes12070722 - 21 Jul 2022

Cited by 5 | Viewed by 1858

Abstract

Some metals belonging to groups IV and V show a high permeability to hydrogen and have been studied as possible alternatives to palladium in membranes for hydrogen purification/separation in order to increase their sustainability and decrease their costs. However, to date, very few [...] Read more.

Some metals belonging to groups IV and V show a high permeability to hydrogen and have been studied as possible alternatives to palladium in membranes for hydrogen purification/separation in order to increase their sustainability and decrease their costs. However, to date, very few alloys among those metals have been investigated, and no membrane studies based on 4–5 element alloys with low or zero Pd content and quasi-amorphous structure have been reported so far. In this work, new membranes based on ZrVTi- and ZrVTiPd alloys were tested for the first time for this application. The unprecedented deposition of micrometric-based multilayers was performed via high-power impulse magnetron sputtering onto porous alumina substrates. Dense Pd/Zr_xV_yTi_zPd_w/Pd multilayers were obtained. The composition of the alloys, morphology and structure, hydrogen permeance, selectivity, and resistance to embrittlement were tested and analyzed depending on the deposition conditions, and the membrane with the enhanced performance was tuned. The environmental impact of these membranes was also investigated to ascertain the sustainability of these alloys relative to more common Pd₇₇Ag₂₃ and V₉₃Pd₇ thin-film membranes using a life cycle assessment analysis. The results showed that the partial substitution of Pd can efficiently lead to a decrease in the environmental impacts of the membranes. Full article

(This article belongs to the Section Inorganic Membranes)

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21 pages, 20559 KiB

Open AccessArticle

Effect of Temperature and Humidity on the Water and Dioxygen Transport Properties of Polybutylene Succinate/Graphene Nanoplatelets Nanocomposite Films

by Raphaël Cosquer, Sébastien Pruvost and Fabrice Gouanvé

Membranes 2022, 12(7), 721; https://doi.org/10.3390/membranes12070721 - 20 Jul 2022

Cited by 1 | Viewed by 1440

Abstract

Nanocomposite films of polybutylene succinate (PBS)/graphene nanoplatelets (GnP) with a GnP content ranging from 0 to 1.35 wt.% were prepared by melt processing. The morphology of both the neat PBS and PBS/GnP nanocomposites were investigated and revealed no significant impact of GnP on [...] Read more.

Nanocomposite films of polybutylene succinate (PBS)/graphene nanoplatelets (GnP) with a GnP content ranging from 0 to 1.35 wt.% were prepared by melt processing. The morphology of both the neat PBS and PBS/GnP nanocomposites were investigated and revealed no significant impact of GnP on the crystalline microstructure. Moisture sorption at 10 °C, 25 °C, and 40 °C were analyzed and modeled using the Guggenheim, Andersen, and De Boer (GAB) equation and Zimm-Lundberg theory, allowing for a phenomenological analysis at the molecular scale. An understanding of the transport sorption properties was proposed by the determination of the molar heat of sorption (ΔH_s), and the activation energy of the diffusion (E_d) of water in the matrix since both solubility and diffusion are thermo-activable properties. Both ΔH_s and E_d showed a good correlation with the water clustering theory at high water activity. Water and dioxygen permeabilities ( and ) were determined as a function of temperature and water activity. and decreased with the addition of a small amount of GnP, regardless of the studied temperature. Moreover, the evolution of as a function of water activity was driven by the solubility process, whereas at a given water activity, was driven by the diffusion process. Activation energies of the permeability (E_p) of water and dioxygen showed a dependency on the nature of the permeant molecule. Finally, from the ΔH_s, E_d, and E_p obtained values, the reduction in water permeability with the addition of a low content of GnP was attributed mainly to a tortuosity effect without diffusive interfaces rather than a significant change in the transport property mechanism. Full article

(This article belongs to the Collection Polymeric Membranes: Science, Materials and Applications)

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12 pages, 5911 KiB

Open AccessArticle

Application of Double Piping Theory to Parallel-Arrayed Low-Pressure Membrane Module Header Pipe and Experimental Verification of Flow Distribution Evenness

by No-Suk Park, Sukmin Yoon, Woochang Jeong and Yong-Wook Jeong

Membranes 2022, 12(7), 720; https://doi.org/10.3390/membranes12070720 - 20 Jul 2022

Viewed by 1452

Abstract

In this study, the improvement effect of flow distribution evenness is evaluated quantitatively by applying the double piping theory to a parallel-arrayed low-pressure membrane module header pipe structure, and its feasibility is discussed. Orifice inner pipes to be inserted into a full-scale membrane [...] Read more.

In this study, the improvement effect of flow distribution evenness is evaluated quantitatively by applying the double piping theory to a parallel-arrayed low-pressure membrane module header pipe structure, and its feasibility is discussed. Orifice inner pipes to be inserted into a full-scale membrane module header pipe are designed via the computational fluid dynamics (CFD) technique, and the flow rates into 10 membrane modules are measured in real time using a portable ultrasonic flowmeter during operation to verify the effect. Results of CFD simulation and actual measurements show that the outflow rate from the branch pipe located at the end of the existing header pipe is three times higher than the flow rate from the branch pipe near the inlet. By inserting two inner pipes (with an open end and a closed end into the existing header pipe) and applying the double pipe theory, the flow distribution evenness is improved. The CFD simulation and experimental results show that the flow uniformity can be improved by more than 70% and 50%, respectively. Full article

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13 pages, 3656 KiB

Open AccessArticle

Small Intestinal Submucosa Biomimetic Periosteum Promotes Bone Regeneration

by Yanlin Su, Bing Ye, Lian Zeng, Zekang Xiong, Tingfang Sun, Kaifang Chen, Qiuyue Ding, Weijie Su, Xirui Jing, Qing Gao, Guixiong Huang, Yizhou Wan, Xu Yang and Xiaodong Guo

Membranes 2022, 12(7), 719; https://doi.org/10.3390/membranes12070719 - 20 Jul 2022

Cited by 4 | Viewed by 1897

Abstract

Background: Critical bone defects are a significant problem in clinics. The periosteum plays a vital role in bone regeneration. A tissue-engineered periosteum (TEP) has received increasing attention as a novel strategy for bone defect repairs. Methods: In this experiment, a biomimetic periosteum was [...] Read more.

Background: Critical bone defects are a significant problem in clinics. The periosteum plays a vital role in bone regeneration. A tissue-engineered periosteum (TEP) has received increasing attention as a novel strategy for bone defect repairs. Methods: In this experiment, a biomimetic periosteum was fabricated by using coaxial electrospinning technology with decellularized porcine small intestinal submucosa (SIS) as the shell and polycaprolactone (PCL) as the core. In vitro, the effects of the biomimetic periosteum on Schwann cells, vascular endothelial cells, and bone marrow mesenchymal stem cells were detected by a scratch test, an EdU, a tube-forming test, and an osteogenesis test. In vivo, we used HE staining to evaluate the effect of the biomimetic periosteum on bone regeneration. Results: In vitro experiments showed that the biomimetic periosteum could significantly promote the formation of angiogenesis, osteogenesis, and repaired Schwann cells (SCs). In vivo experiments showed that the biomimetic periosteum could promote the repair of bone defects. Conclusions: The biomimetic periosteum could simulate the structural function of the periosteum and promote bone repair. This strategy may provide a promising method for the clinical treatment of skull bone defects. Full article

(This article belongs to the Special Issue Biocompatible Membranes for Bone Regeneration)

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12 pages, 2723 KiB

Open AccessArticle

Protons in Gating the Kv1.2 Channel: A Calculated Set of Protonation States in Response to Polarization/Depolarization of the Channel, with the Complete Proposed Proton Path from Voltage Sensing Domain to Gate

by Alisher M. Kariev and Michael E. Green

Membranes 2022, 12(7), 718; https://doi.org/10.3390/membranes12070718 - 20 Jul 2022

Cited by 2 | Viewed by 1583

Abstract

We have in the past proposed that proton motion constitutes the gating current in the potassium channel K_v1.2 and is responsible for the gating mechanism. For this to happen, there must be a proton path between the voltage-sensing domain (VSD) and [...] Read more.

We have in the past proposed that proton motion constitutes the gating current in the potassium channel K_v1.2 and is responsible for the gating mechanism. For this to happen, there must be a proton path between the voltage-sensing domain (VSD) and the channel gate, and here we present quantum calculations that lead to a specific pair of proton paths, defined at the molecular level, with well-defined water molecule linkages, and with hydrogen bonding between residues; there is also at least one interpath crossover, where protons can switch paths. Quantum calculations on the entire 563-atom system give the complete geometry, the energy, and atomic charges. Calculations show that three specific residues (in the pdb 3Lut numbering, H418, E327, R326), and the T1 intracellular moiety, all of which have been shown experimentally to be involved in gating, would necessarily be protonated or deprotonated in the path between the VSD and the gate. Hydroxyl reorientation of serine and threonine residues are shown to provide a means of adjusting proton directions of motion. In the deprotonated state for K312, a low energy state, our calculations come close to reproducing the X-ray structure. The demonstration of the existence of a double proton path between VSD and gate supports the proposed proton gating mechanism; when combined with our earlier demonstration of proton generation in the VSD, and comparison with other systems that are known to move protons, we are close to achieving the definition of a complete gating mechanism in molecular detail. The coupling of the paths to the VSD, and to the PVPV section that essentially forms the gate, can be easily seen from the results of the calculation. The gate itself remains for further computations. Full article

(This article belongs to the Collection Membrane Protein Structure and Functions)

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12 pages, 3328 KiB

Open AccessArticle

Desalination Using the Capacitive Deionization Technology with Graphite/AC Electrodes: Effect of the Flow Rate and Electrode Thickness

by Jhonatan Martinez, Martín Colán, Ronald Catillón, Jesús Huamán, Robert Paria, Luis Sánchez and Juan M. Rodríguez

Membranes 2022, 12(7), 717; https://doi.org/10.3390/membranes12070717 - 20 Jul 2022

Cited by 5 | Viewed by 2167

Abstract

Capacitive deionization (CDI) is an emerging water desalination technology whose principle lies in ion electrosorption at the surface of a pair of electrically charged electrodes. The aim of this study was to obtain the best performance of a CDI cell made of activated [...] Read more.

Capacitive deionization (CDI) is an emerging water desalination technology whose principle lies in ion electrosorption at the surface of a pair of electrically charged electrodes. The aim of this study was to obtain the best performance of a CDI cell made of activated carbon as the active material for water desalination. In this work, electrodes of different active layer thicknesses were fabricated from a slurry of activated carbon deposited on graphite sheets. The as-prepared electrodes were characterized by cyclic voltammetry, and their physical properties were also studied using SEM and DRX. A CDI cell was fabricated with nine pairs of electrodes with the highest specific capacitance. The effect of the flow rate on the electrochemical performance of the CDI cell operating in charge–discharge electrochemical cycling was analyzed. We obtained a specific absorption capacity (SAC) of 10.2 mg/g and a specific energetic consumption (SEC) of 217.8 Wh/m³ at a flow rate of 55 mL/min. These results were contrasted with those available in the literature; in addition, other parameters such as Neff and SAR, which are necessary for the characterization and optimal operating conditions of the CDI cell, were analyzed. The findings from this study lay the groundwork for future research and increase the existing knowledge on CDI based on activated carbon electrodes. Full article

(This article belongs to the Section Membrane Applications)

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28 pages, 1612 KiB

Open AccessReview

Mesenchymal Stem Cell-Derived Extracellular Vesicles for Bone Defect Repair

by Dongxue Wang, Hong Cao, Weizhong Hua, Lu Gao, Yu Yuan, Xuchang Zhou and Zhipeng Zeng

Membranes 2022, 12(7), 716; https://doi.org/10.3390/membranes12070716 - 19 Jul 2022

Cited by 12 | Viewed by 3587

Abstract

The repair of critical bone defects is a hotspot of orthopedic research. With the development of bone tissue engineering (BTE), there is increasing evidence showing that the combined application of extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) (MSC-EVs), especially exosomes, with [...] Read more.

The repair of critical bone defects is a hotspot of orthopedic research. With the development of bone tissue engineering (BTE), there is increasing evidence showing that the combined application of extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) (MSC-EVs), especially exosomes, with hydrogels, scaffolds, and other bioactive materials has made great progress, exhibiting a good potential for bone regeneration. Recent studies have found that miRNAs, proteins, and other cargo loaded in EVs are key factors in promoting osteogenesis and angiogenesis. In BTE, the expression profile of the intrinsic cargo of EVs can be changed by modifying the gene expression of MSCs to obtain EVs with enhanced osteogenic activity and ultimately enhance the osteoinductive ability of bone graft materials. However, the current research on MSC-EVs for repairing bone defects is still in its infancy, and the underlying mechanism remains unclear. Therefore, in this review, the effect of bioactive materials such as hydrogels and scaffolds combined with MSC-EVs in repairing bone defects is summarized, and the mechanism of MSC-EVs promoting bone defect repair by delivering active molecules such as internal miRNAs is further elucidated, which provides a theoretical basis and reference for the clinical application of MSC-EVs in repairing bone defects. Full article

(This article belongs to the Special Issue Biocompatible Membranes for Bone Regeneration)

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21 pages, 2452 KiB

Open AccessReview

Host–Bacterial Interactions: Outcomes of Antimicrobial Peptide Applications

by Asma Hussain Alkatheri, Polly Soo-Xi Yap, Aisha Abushelaibi, Kok-Song Lai, Wan-Hee Cheng and Swee-Hua Erin Lim

Membranes 2022, 12(7), 715; https://doi.org/10.3390/membranes12070715 - 19 Jul 2022

Cited by 2 | Viewed by 2611

Abstract

The bacterial membrane is part of a secretion system which plays an integral role to secrete proteins responsible for cell viability and pathogenicity; pathogenic bacteria, for example, secrete virulence factors and other membrane-associated proteins to invade the host cells through various types of [...] Read more.

The bacterial membrane is part of a secretion system which plays an integral role to secrete proteins responsible for cell viability and pathogenicity; pathogenic bacteria, for example, secrete virulence factors and other membrane-associated proteins to invade the host cells through various types of secretion systems (Type I to Type IX). The bacterial membrane can also mediate microbial communities’ communication through quorum sensing (QS), by secreting auto-stimulants to coordinate gene expression. QS plays an important role in regulating various physiological processes, including bacterial biofilm formation while providing increased virulence, subsequently leading to antimicrobial resistance. Multi-drug resistant (MDR) bacteria have emerged as a threat to global health, and various strategies targeting QS and biofilm formation have been explored by researchers worldwide. Since the bacterial secretion systems play such a crucial role in host–bacterial interactions, this review intends to outline current understanding of bacterial membrane systems, which may provide new insights for designing approaches aimed at antimicrobials discovery. Various mechanisms pertaining interaction of the bacterial membrane with host cells and antimicrobial agents will be highlighted, as well as the evolution of bacterial membranes in evasion of antimicrobial agents. Finally, the use of antimicrobial peptides (AMPs) as a cellular device for bacterial secretion systems will be discussed as emerging potential candidates for the treatment of multidrug resistance infections. Full article

(This article belongs to the Collection Feature Papers in Membranes in Life Sciences)

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15 pages, 3786 KiB

Open AccessArticle

Electrospun Hydrophobic Interaction Chromatography (HIC) Membranes for Protein Purification

by Shu-Ting Chen, Sumith Ranil Wickramasinghe and Xianghong Qian

Membranes 2022, 12(7), 714; https://doi.org/10.3390/membranes12070714 - 18 Jul 2022

Cited by 1 | Viewed by 1813

Abstract

Responsive membranes for hydrophobic interaction chromatography have been fabricated by functionalizing poly(N-vinylcaprolactam) (PVCL) ligands on the substrate of electrospun regenerated cellulose nanofibers. Both static and dynamic binding capacities and product recovery were investigated using bovine serum albumin (BSA) and Immunoglobulin G (IgG) as [...] Read more.

Responsive membranes for hydrophobic interaction chromatography have been fabricated by functionalizing poly(N-vinylcaprolactam) (PVCL) ligands on the substrate of electrospun regenerated cellulose nanofibers. Both static and dynamic binding capacities and product recovery were investigated using bovine serum albumin (BSA) and Immunoglobulin G (IgG) as model proteins. The effects of ligand chain length and chain density on static binding capacity were also studied. A static binding capacity of ~25 mg/mL of membrane volume (MV) can be achieved in optimal ligand grafting conditions. For dynamic binding studies, protein binding capacity increased with protein concentration from 0.1 to 1.0 g/L. Dynamic binding capacity increased from ~8 mg/mL MV at 0.1 g/L BSA to over 30 mg/mL at 1.0 g/L BSA. However, BSA recovery decreased as protein concentration increased from ~98% at 0.1 g/L BSA to 51% at 1 g/L BSA loading concentration. There is a clear trade-off between binding capacity and recovery rate. The electrospun substrate with thicker fibers and more open pore structures is superior to thinner fibrous membrane substrates. Full article

(This article belongs to the Special Issue Nanofibrous Membrane for Biomedical Application)

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12 pages, 2210 KiB

Open AccessArticle

Intravenous Nanocarrier for Improved Efficacy of Quercetin and Curcumin against Breast Cancer Cells: Development and Comparison of Single and Dual Drug–Loaded Formulations Using Hemolysis, Cytotoxicity and Cellular Uptake Studies

by Mohammad Akhlaquer Rahman, Vineet Mittal, Shadma Wahab, Abdulrhman Alsayari, Abdullatif Bin Muhsinah and Dalia Almaghaslah

Membranes 2022, 12(7), 713; https://doi.org/10.3390/membranes12070713 - 15 Jul 2022

Cited by 10 | Viewed by 1825

Abstract

The present work highlights the suitability of an oil-based nanocarrier to deliver quercetin (Q) and curcumin (C) through the intravenous route for treatment of breast cancer. The nanoemulsion prepared by the modified emulsification-solvent evaporation method resulted in particle size (<30 nm), polydispersity index [...] Read more.

The present work highlights the suitability of an oil-based nanocarrier to deliver quercetin (Q) and curcumin (C) through the intravenous route for treatment of breast cancer. The nanoemulsion prepared by the modified emulsification-solvent evaporation method resulted in particle size (<30 nm), polydispersity index (<0.2), zeta potential (<10 mV), optimum viscosity, high encapsulation efficiency and drug loading for both drugs. The pH and osmolarity of the nanoemulsion were about 7.0 and 280 mOsm, respectively, demonstrated its suitability for intravenous administration. In-vitro release of drugs from all the formulations demonstrated initial fast release followed by sustained release for a period of 48 h. The fabricated single and dual drug–loaded nanoemulsion (QNE, CNE, QC-NE) exhibited moderate hemolysis at a concentration of 50 μg/mL. The % hemolysis caused by all the formulations was similar to their individual components (p ˃ 0.05) and demonstrated the biocompatibility of the nanoemulsion with human blood. In vitro cytotoxic potential of single and dual drug–loaded nanoemulsions were determined against breast cancer cells (MF-7). The IC₅₀ value for QNE and CNE were found to be 40.2 ± 2.34 µM and 28.12 ± 2.07 µM, respectively. The IC₅₀ value for QC-NE was 21.23 ± 2.16 µM and demonstrated the synergistic effect of both the drugs. The internalization of the drug inside MF-7 cells was detected by cellular uptake study. The cellular uptake of QNE and CNE was approximately 3.9-fold higher than free quercetin and curcumin (p < 0.0001). This strategically designed nanoemulsion appears to be a promising drug delivery system for the proficient primary preclinical development of quercetin and curcumin as therapeutic modalities for the treatment of breast cancer. Full article

(This article belongs to the Special Issue Nanotechnologies and Nanoparticles Interaction with Bio-Membranes)

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16 pages, 1750 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Partial Removal of Sugar from Apple Juice by Nanofiltration and Discontinuous Diafiltration

by Martina Gaglianò, Carmela Conidi, Giuseppina De Luca and Alfredo Cassano

Membranes 2022, 12(7), 712; https://doi.org/10.3390/membranes12070712 - 15 Jul 2022

Cited by 6 | Viewed by 2812

Abstract

Partial removal of sugars in fruit juices without compromising their biofunctional properties represents a significant technological challenge. The current study was aimed at evaluating the separation of sugars from phenolic compounds in apple juice by using three different spiral-wound nanofiltration (NF) membranes with [...] Read more.

Partial removal of sugars in fruit juices without compromising their biofunctional properties represents a significant technological challenge. The current study was aimed at evaluating the separation of sugars from phenolic compounds in apple juice by using three different spiral-wound nanofiltration (NF) membranes with a molecular weight cut-off (MWCO) in the range of 200–500 Da. A combination of diafiltration and batch concentration processes was investigated to produce apple juice with reduced sugar content and improved health properties thanks to the preservation and concentration of phenolic compounds. For all selected membranes, permeate flux and recovery rate of glucose, fructose, and phenolic compounds, in both diafiltration and concentration processes, were evaluated. The concentration factor of target compounds as a function of the volume reduction factor (VRF) as well as the amount of adsorbed compound on the membrane surface from mass balance analysis were also evaluated. Among the investigated membranes a thin-film composite membrane with an MWCO of 200–300 Da provided the best results in terms of the preservation of phenolic compounds in the selected operating conditions. More than 70% of phenolic compounds were recovered in the retentate stream while the content of sugars was reduced by about 60%. Full article

(This article belongs to the Special Issue Membrane Technologies for Sustainability)

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18 pages, 13968 KiB

Open AccessArticle

In Vivo Evaluation of Permeable and Impermeable Membranes for Guided Bone Regeneration

by Suelen Cristina Sartoretto, Natalia de Freitas Gens, Rodrigo Figueiredo de Brito Resende, Adriana Terezinha Neves Novellino Alves, Rafael Cury Cecato, Marcelo José Uzeda, Jose Mauro Granjeiro, Monica Diuana Calasans-Maia and Jose Albuquerque Calasans-Maia

Membranes 2022, 12(7), 711; https://doi.org/10.3390/membranes12070711 - 15 Jul 2022

Viewed by 2381

Abstract

Background: The degree of biodegradation and the inflammatory response of membranes employed for guided bone regeneration directly impact the outcome of this technique. This study aimed to evaluate four different experimental versions of Poly (L-lactate-co-Trimethylene Carbonate) (PTMC) + Poly (L-lactate-co-glycolate) (PLGA) membranes, implanted [...] Read more.

Background: The degree of biodegradation and the inflammatory response of membranes employed for guided bone regeneration directly impact the outcome of this technique. This study aimed to evaluate four different experimental versions of Poly (L-lactate-co-Trimethylene Carbonate) (PTMC) + Poly (L-lactate-co-glycolate) (PLGA) membranes, implanted in mouse subcutaneous tissue, compared to a commercially available membrane and a Sham group. Methods: Sixty Balb-C mice were randomly divided into six experimental groups and subdivided into 1, 3, 6 and 12 weeks (n = 5 groups/period). The membranes (1 cm²) were implanted in the subcutaneous back tissue of the animals. The samples were obtained for descriptive and semiquantitative histological evaluation (ISO 10993-6). Results: G1 and G4 allowed tissue adhesion and the permeation of inflammatory cells over time and showed greater phagocytic activity and permeability. G2 and G3 detached from the tissue in one and three weeks; however, in the more extended periods, they presented a rectilinear and homogeneous aspect and were not absorbed. G2 had a major inflammatory reaction. G5 was almost completely absorbed after 12 weeks. Conclusions: The membranes are considered biocompatible. G5 showed a higher degree of biosorption, followed by G1 and G4. G2 and G3 are considered non-absorbable in the studied periods. Full article

(This article belongs to the Special Issue Recent Developments in Membrane Biology)

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23 pages, 9584 KiB

Open AccessArticle

Investigating the Dialysis Treatment Using Hollow Fiber Membrane: A New Approach by CFD

by Hortência L. F. Magalhães, Ricardo S. Gomez, Boniek E. Leite, Jéssica B. S. Nascimento, Mirenia K. T. Brito, Morgana V. Araújo, Daniel C. M. Cavalcante, Elisiane S. Lima, Antonio G. B. Lima and Severino R. Farias Neto

Membranes 2022, 12(7), 710; https://doi.org/10.3390/membranes12070710 - 15 Jul 2022

Cited by 2 | Viewed by 2329

Abstract

Due to the increase in the number of people affected by chronic renal failure, the demand for hemodialysis treatment has increased considerably over the years. In this sense, theoretical and experimental studies to improve the equipment (hemodialyzer) are extremely important, due to their [...] Read more.

Due to the increase in the number of people affected by chronic renal failure, the demand for hemodialysis treatment has increased considerably over the years. In this sense, theoretical and experimental studies to improve the equipment (hemodialyzer) are extremely important, due to their potential impact on the patient’s life quality undergoing treatment. To contribute to this research line, this work aims to study the fluid behavior inside a hollow fiber dialyzer using computational fluid dynamics. In that new approach, the blood is considered as multiphase fluid and the membrane as an extra flow resistance in the porous region (momentum sink). The numerical study of the hemodialysis process was based on the development of a mathematical model that allowed analyzing the performance of the system using Ansys^® Fluent software. The predicted results were compared with results reported in the literature and a good concordance was obtained. The simulation results showed that the proposed model can predict the fluid behavior inside the hollow fiber membrane adequately. In addition, it was found that the clearance decreases with increasing radial viscous resistance, with greater permeations in the vicinity of the lumen inlet region, as well as the emergence of the retrofiltration phenomenon, characteristic of this type of process. Herein, velocity, pressure, and volumetric fraction fields are presented and analyzed. Full article

(This article belongs to the Special Issue Advances in Porous and Dense Membranes: Fabrication and Applications)

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12 pages, 2788 KiB

Open AccessArticle

Computational Studies on Holey TMC₆ (TM = Mo and W) Membranes for H₂ Purification

by Juan Xie, Cai Ning, Qinqin Liu, Zhongti Sun, Juan Yang and Huilong Dong

Membranes 2022, 12(7), 709; https://doi.org/10.3390/membranes12070709 - 14 Jul 2022

Viewed by 1269

Abstract

The purification of hydrogen (H₂) has been a vital step in H₂ production processes such as steam–methane reforming. By first-principle calculations, we revealed the potential applications of holey TMC₆ (TM = Mo and W) membranes in H₂ purification. [...] Read more.

The purification of hydrogen (H₂) has been a vital step in H₂ production processes such as steam–methane reforming. By first-principle calculations, we revealed the potential applications of holey TMC₆ (TM = Mo and W) membranes in H₂ purification. The adsorption and diffusion behaviors of five gas molecules (including H₂, N₂, CO, CO₂, and CH₄) were compared on TMC₆ membranes with different phases. Though the studied gas molecules show weak physisorption on the TMC₆ membranes, the smaller pore size makes the gas molecules much more difficult to permeate into h-TMC₆ rather than into s-TMC₆. With suitable pore sizes, the s-TMC₆ structures not only show an extremely low diffusion barrier (around 0.1 eV) and acceptable permeance capability for the H₂ but also exhibit considerably high selectivity for both H₂/CH₄ and H₂/CO₂ (>10¹⁵), especially under relatively low temperature (150–250 K). Moreover, classical molecular dynamics simulations on the permeation process of a H₂, CO₂, and CH₄ mixture also validated that s-TMC₆ could effectively separate H₂ from the gas mixture. Hence, the s-MoC₆ and s-WC₆ are predicted to be qualified H₂ purification membranes, especially below room temperature. Full article

(This article belongs to the Special Issue Functional Porous Membranes for Energy, Environmental and Biomedical Applications)

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27 pages, 33404 KiB

Open AccessArticle

Rational Discovery of Antimicrobial Peptides by Means of Artificial Intelligence

by Paola Ruiz Puentes, Maria C. Henao, Javier Cifuentes, Carolina Muñoz-Camargo, Luis H. Reyes, Juan C. Cruz and Pablo Arbeláez

Membranes 2022, 12(7), 708; https://doi.org/10.3390/membranes12070708 - 14 Jul 2022

Cited by 7 | Viewed by 4022

Abstract

Antibiotic resistance is a worldwide public health problem due to the costs and mortality rates it generates. However, the large pharmaceutical industries have stopped searching for new antibiotics because of their low profitability, given the rapid replacement rates imposed by the increasingly observed [...] Read more.

Antibiotic resistance is a worldwide public health problem due to the costs and mortality rates it generates. However, the large pharmaceutical industries have stopped searching for new antibiotics because of their low profitability, given the rapid replacement rates imposed by the increasingly observed resistance acquired by microorganisms. Alternatively, antimicrobial peptides (AMPs) have emerged as potent molecules with a much lower rate of resistance generation. The discovery of these peptides is carried out through extensive in vitro screenings of either rational or non-rational libraries. These processes are tedious and expensive and generate only a few AMP candidates, most of which fail to show the required activity and physicochemical properties for practical applications. This work proposes implementing an artificial intelligence algorithm to reduce the required experimentation and increase the efficiency of high-activity AMP discovery. Our deep learning (DL) model, called AMPs-Net, outperforms the state-of-the-art method by 8.8% in average precision. Furthermore, it is highly accurate to predict the antibacterial and antiviral capacity of a large number of AMPs. Our search led to identifying two unreported antimicrobial motifs and two novel antimicrobial peptides related to them. Moreover, by coupling DL with molecular dynamics (MD) simulations, we were able to find a multifunctional peptide with promising therapeutic effects. Our work validates our previously proposed pipeline for a more efficient rational discovery of novel AMPs. Full article

(This article belongs to the Special Issue The Structure, Dynamics and Function of Membrane Proteins)

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17 pages, 4122 KiB

Open AccessArticle

Roles of Sodium Hydrogen Exchanger (NHE1) and Anion Exchanger (AE2) across Chondrocytes Plasma Membrane during Longitudinal Bone Growth

by Adamu Abdul Abubakar, Ahmed Khalaf Ali, Sahar Mohammed Ibrahim, Kareem Obayes Handool, Mohammad Shuaib Khan, Noordin Mohamed Mustapha, Tengku Azmi Tengku Ibrahim, Ubedullah Kaka and Loqman Mohamad Yusof

Membranes 2022, 12(7), 707; https://doi.org/10.3390/membranes12070707 - 14 Jul 2022

Viewed by 1615

Abstract

Mammalian long bone growth occurs through endochondral ossification, majorly regulated by the controlled enlargement of chondrocytes at the growth plate (GP). This study aimed to investigate the roles of Na⁺/H⁺ (sodium hydrogen exchanger (NHE1)) and HCO₃⁻ (anion exchanger [...] Read more.

Mammalian long bone growth occurs through endochondral ossification, majorly regulated by the controlled enlargement of chondrocytes at the growth plate (GP). This study aimed to investigate the roles of Na⁺/H⁺ (sodium hydrogen exchanger (NHE1)) and HCO₃⁻ (anion exchanger [AE2]) during longitudinal bone growth in mammals. Bones from P10 SpragueDawley rat pups were cultured exvivo in the presence or absence of NHE1 and AE2 inhibitors to determine their effect on long bone growth. Gross morphometry, histomorphometry, and immunohistochemistry were used to assess the bone growth. The results revealed that the culture of the bones in the presence of NHE1 and AE2 inhibitors reduces bone growth significantly (p < 0.05) by approximately 11%. The inhibitor significantly (p < 0.05) reduces bone growth velocity and the length of the hypertrophic chondrocyte zone without any effect on the total GP length. The total GP chondrocyte density was significantly (p < 0.05) reduced, but hypertrophic chondrocyte densities remained constant. NHE1 fluorescence signaling across the GP length was higher than AE2, and their localization was significantly (p < 0.05) inhibited at the hypertrophic chondrocytes zone. The GP lengthening was majorly driven by an increase in the overall GP chondrocyte and hypertrophic chondrocyte densities apart from the regulatory volume phenomenon. This may suggest that NHE1 and AE2 could have a regulatory role in long bone growth. Full article

(This article belongs to the Section Biological Membrane Functions)

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20 pages, 4888 KiB

Open AccessArticle

Substantial Proton Ion Conduction in Methylcellulose/Pectin/Ammonium Chloride Based Solid Nanocomposite Polymer Electrolytes: Effect of ZnO Nanofiller

by John Ojur Dennis, Abdullahi Abbas Adam, M. K. M. Ali, Hassan Soleimani, Muhammad Fadhlullah Bin Abd. Shukur, K. H. Ibnaouf, O. Aldaghri, M. H. Eisa, M. A. Ibrahem, Abubakar Bashir Abdulkadir and Vipin Cyriac

Membranes 2022, 12(7), 706; https://doi.org/10.3390/membranes12070706 - 13 Jul 2022

Cited by 18 | Viewed by 1823

Abstract

In this research, nanocomposite solid polymer electrolytes (NCSPEs) comprising methylcellulose/pectin (MC/PC) blend as host polymer, ammonium chloride (NH₄Cl) as an ion source, and zinc oxide nanoparticles (ZnO NPs) as nanofillers were synthesized via a solution cast methodology. Techniques such as Fourier [...] Read more.

In this research, nanocomposite solid polymer electrolytes (NCSPEs) comprising methylcellulose/pectin (MC/PC) blend as host polymer, ammonium chloride (NH₄Cl) as an ion source, and zinc oxide nanoparticles (ZnO NPs) as nanofillers were synthesized via a solution cast methodology. Techniques such as Fourier transform infrared (FTIR), electrical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) were employed to characterize the electrolyte. FTIR confirmed that the polymers, NH₄Cl salt, and ZnO nanofiller interact with one another appreciably. EIS demonstrated the feasibility of achieving a conductivity of 3.13 × 10⁻⁴ Scm⁻¹ for the optimum electrolyte at room temperature. Using the dielectric formalism technique, the dielectric properties, energy modulus, and relaxation time of NH₄Cl in MC/PC/NH₄Cl and MC/PC/NH₄Cl/ZnO systems were determined. The contribution of chain dynamics and ion mobility was acknowledged by the presence of a peak in the imaginary portion of the modulus study. The LSV measurement yielded 4.55 V for the comparatively highest conductivity NCSPE. Full article

(This article belongs to the Special Issue Composite Conducting Membranes: Preparation, Properties, and Applications-Volume 2)

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16 pages, 3752 KiB

Open AccessArticle

Dry Glass Reference Perturbation Theory Predictions of the Temperature and Pressure Dependent Separations of Complex Liquid Mixtures Using SBAD-1 Glassy Polymer Membranes

by Bennett D. Marshall, Wenjun Li and Ryan P. Lively

Membranes 2022, 12(7), 705; https://doi.org/10.3390/membranes12070705 - 12 Jul 2022

Cited by 5 | Viewed by 1381

Abstract

In this work we apply dry glass reference perturbation theory (DGRPT) within the context of fully mutualized diffusion theory to predict the temperature and pressure dependent separations of complex liquid mixtures using SBAD-1 glassy polymer membranes. We demonstrate that the approach allows for [...] Read more.

In this work we apply dry glass reference perturbation theory (DGRPT) within the context of fully mutualized diffusion theory to predict the temperature and pressure dependent separations of complex liquid mixtures using SBAD-1 glassy polymer membranes. We demonstrate that the approach allows for the prediction of the membrane-based separation of complex liquid mixtures over a wide range of temperature and pressure, using only single-component vapor sorption isotherms measured at 25 °C to parameterize the model. The model was then applied to predict the membrane separation of a light shale crude using a structure oriented lumping (SOL) based compositional model of petroleum. It was shown that when DGRPT is applied based on SOL compositions, the combined model allows for the accurate prediction of separation performance based on the trend of both molecular weight and molecular class. Full article

(This article belongs to the Special Issue Fundamentals of Transport in Polymers and Membranes—Honorary Issue for Professor Giulio C. Sarti)

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13 pages, 4984 KiB

Open AccessArticle

Chemical Cleaning and Membrane Aging in MBR for Textile Wastewater Treatment

by Huarong Yu, Siyuan Shangguan, Chenyu Xie, Haiyang Yang, Chunhai Wei, Hongwei Rong and Fangshu Qu

Membranes 2022, 12(7), 704; https://doi.org/10.3390/membranes12070704 - 12 Jul 2022

Cited by 6 | Viewed by 1961

Abstract

Membrane bioreactors have been widely used in textile wastewater treatment. Intensive chemical cleaning is indispensable in the MBR for textile wastewater treatment due to the severe membrane fouling implied. This work investigated the aging of three different membranes, polyvinylidene fluoride (PVDF), polyether sulfone [...] Read more.

Membrane bioreactors have been widely used in textile wastewater treatment. Intensive chemical cleaning is indispensable in the MBR for textile wastewater treatment due to the severe membrane fouling implied. This work investigated the aging of three different membranes, polyvinylidene fluoride (PVDF), polyether sulfone (PES), and polytetrafluoroethylene (PTFE), in the MBRs for textile wastewater treatment. Pilot-scale MBRs were operated and the used membrane was characterized. Batch chemical soaking tests were conducted to elucidate the aging properties of the membranes. The results indicated that the PVDF membrane was most liable to the chemical cleaning, and the PES and PTFE membranes were rather stable. The surface hydrophobicity of the PVDF increased in the acid aging test, and the pore size and pure water flux decreased due to the elevated hydrophobic effect; alkaline oxide aging destructed the structure of the PVDF membrane, enlarged pore size, and increased pure water flux. Chemical cleaning only altered the interfacial properties (hydrophobicity and surface zeta potential) of the PES and PTFE membranes. The fluoro-substitution and the dehydrofluorination of the PVDF, chain scission of the PES molecules, and dehydrofluorination of the PTFE were observed in aging. A chemically stable and anti-aging membrane would be of great importance in the MBR for textile wastewater treatment due to the intensive chemical cleaning applied. Full article

(This article belongs to the Special Issue Electroconductive Membranes for Wastewater Treatment and Energy Applications)

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18 pages, 3069 KiB

Open AccessArticle

Membrane Fouling Mitigation in MBR via the Feast–Famine Strategy to Enhance PHA Production by Activated Sludge

by Santo Fabio Corsino, Gaetano Di Bella, Francesco Traina, Lucia Argiz Montes, Angeles Val del Rio, Anuska Mosquera Corral, Michele Torregrossa and Gaspare Viviani

Membranes 2022, 12(7), 703; https://doi.org/10.3390/membranes12070703 - 12 Jul 2022

Cited by 3 | Viewed by 2140

Abstract

Fouling is considered one of the main drawbacks of membrane bioreactor (MBR) technology. Among the main fouling agents, extracellular polymeric substances (EPS) are considered one of the most impactful since they cause the decrease of sludge filterability and decline of membrane flux in [...] Read more.

Fouling is considered one of the main drawbacks of membrane bioreactor (MBR) technology. Among the main fouling agents, extracellular polymeric substances (EPS) are considered one of the most impactful since they cause the decrease of sludge filterability and decline of membrane flux in the long term. The present study investigated a biological strategy to reduce the membrane-fouling tendency in MBR systems. This consisted of seeding the reactor with activated sludge enriched in microorganisms with polyhydroxyalkanoate (PHA) storage ability and by imposing proper operating conditions to drive the carbon toward intracellular (PHA) rather than extracellular (EPS) accumulation. For that purpose, an MBR lab-scale plant was operated for 175 days, divided into four periods (1–4) according to different food to microorganisms’ ratios (F/M) (0.80 kg COD kg TSS⁻¹ d⁻¹ (Period 1), 0.13 kg COD kg TSS⁻¹ d⁻¹ (Period 2), 0.28 kg COD kg TSS⁻¹ d⁻¹ (Period 3), and 0.38 kg COD kg TSS⁻¹ d⁻¹ (Period 4)). The application of the feast/famine strategy favored the accumulation of intracellular polymers by bacteria. The increase of the PHA accumulation inside the cells corresponded to the decrease of EPS and an F/M of 0.40–0.50 kg COD kg TSS⁻¹ d⁻¹ was found as optimum to maximize the PHA production, while minimizing EPS. The lowest EPS content in the sludge (18% of total suspended solids) that corresponded to the maximum content of PHA (9.3%) was found in Period 4 and determined significant mitigation of the fouling rate, whose value was close to 0.10 × 10¹¹ m⁻¹ h⁻¹. Thus, by imposing proper operating conditions, it was possible to drive the organic matter toward PHA accumulation. Moreover, a lower EPS content corresponded to a decrease in the irreversible fouling mechanism, which would imply a lower frequency of the extraordinary cleaning operations. This study highlighted the possibility of obtaining a double benefit by applying an MBR system in the frame of wastewater valorization: minimizing the fouling tendency of the membrane and recovery precursors of bioplastics from wastewater in line with the circular economy model. Full article

(This article belongs to the Collection Feature Papers in Membrane Bio-Reactor Valorisation)

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13 pages, 3285 KiB

Open AccessArticle

In Silico Assessment of the Lipid Fingerprint Signature of ATP2, the Essential P4-ATPase of Malaria Parasites

by Mario López-Martín, Pedro Renault, Jesus Giraldo, José Luis Vázquez-Ibar and Alex Perálvarez-Marín

Membranes 2022, 12(7), 702; https://doi.org/10.3390/membranes12070702 - 12 Jul 2022

Cited by 1 | Viewed by 1723

Abstract

ATP2, a putative type 4 P-type ATPase, is a phosphatidylinositol-4-phosphate (PI4P)-regulated phospholipid transporter with an interesting potential as an antimalarial drug target due to its conservation across Plasmodium species and its essential role in the life cycle of Plasmodium falciparum. Despite its [...] Read more.

ATP2, a putative type 4 P-type ATPase, is a phosphatidylinositol-4-phosphate (PI4P)-regulated phospholipid transporter with an interesting potential as an antimalarial drug target due to its conservation across Plasmodium species and its essential role in the life cycle of Plasmodium falciparum. Despite its importance, the exact mechanism of its action and regulation is still not fully understood. In this study we used coarse-grained molecular dynamics (CG-MD) to elucidate the lipid–protein interactions between a heterogeneous lipid membrane containing phosphatidylinositol and Plasmodium chabaudi ATP2 (PcATP2), an ortholog of P. falciparum ATP2. Our study reveals structural information of the lipid fingerprint of ATP2, and provides structural information on the potential phosphatidylinositol allosteric binding site. Moreover, we identified a set of evolutionary conserved residues that may play a key role in the binding and stabilization of lipids in the binding pocket. Full article

(This article belongs to the Special Issue Experimental and Computational Methods for Membrane Protein Design)

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14 pages, 2105 KiB

Open AccessArticle

Sustainable and Eco-Friendly Packaging Films Based on Poly (Vinyl Alcohol) and Glass Flakes

by Iftikhar Ahmed Channa, Jaweria Ashfaq, Sadaf Jamal Gilani, Ali Dad Chandio, Sumra Yousuf, Muhammad Atif Makhdoom and May Nasser bin Jumah

Membranes 2022, 12(7), 701; https://doi.org/10.3390/membranes12070701 - 11 Jul 2022

Cited by 12 | Viewed by 3045

Abstract

The majority of food packaging materials are petroleum-based polymers, which are neither easily recyclable nor ecologically friendly. Packaging films should preferably be transparent, light in weight, and easy to process, as well as mechanically flexible, and they should meet the criteria for food [...] Read more.

The majority of food packaging materials are petroleum-based polymers, which are neither easily recyclable nor ecologically friendly. Packaging films should preferably be transparent, light in weight, and easy to process, as well as mechanically flexible, and they should meet the criteria for food encapsulation. In this study, poly (vinyl alcohol) (PVA)-based films were developed by incorporating glass flakes into the films. The selection of PVA was based on its well-known biodegradability, whereas the selection of glass flakes was based on their natural impermeability to oxygen and moisture. The films were processed using the blade coating method and were characterized in terms of transparency, oxygen transmission rate, mechanical strength, and flexibility. We observed that the incorporation of glass flakes into the PVA matrix did not significantly change the transparency of the PVA films, and they exhibited a total transmittance of around 87% (at 550 nm). When the glass flakes were added to the PVA, a significant reduction in moisture permeation was observed. This reduction was also supported and proven by Bhardwaj’s permeability model. In addition, even after the addition of glass flakes to the PVA, the films remained flexible and showed no degradation in terms of the water vapor transmission rate (WVTR), even after bending cycles of 23,000. The PVA film with glass flakes had decent tensile characteristics, i.e., around >50 MPa. Increasing the concentration of glass flakes also increased the hardness of the films. Finally, a piece of bread was packaged in a well-characterized composite film. We observed that the bread packaged in the PVA film with glass flakes did not show any degradation at all, even after 10 days, whereas the bread piece packaged in a commercial polyethylene bag degraded completely. Based on these results, the developed packaging films are the perfect solution to replace commercial non-biodegradable films. Full article

(This article belongs to the Special Issue Advanced Polymeric Membranes for Energy & Environment)

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12 pages, 3167 KiB

Open AccessArticle

Large-Scale Screening and Machine Learning for Metal–Organic Framework Membranes to Capture CO₂ from Flue Gas

by Yizhen Situ, Xueying Yuan, Xiangning Bai, Shuhua Li, Hong Liang, Xin Zhu, Bangfen Wang and Zhiwei Qiao

Membranes 2022, 12(7), 700; https://doi.org/10.3390/membranes12070700 - 11 Jul 2022

Cited by 5 | Viewed by 2428

Abstract

To combat global warming, as an energy-saving technology, membrane separation can be applied to capture CO₂ from flue gas. Metal–organic frameworks (MOFs) with characteristics like high porosity have great potential as membrane materials for gas mixture separation. In this work, through a [...] Read more.

To combat global warming, as an energy-saving technology, membrane separation can be applied to capture CO₂ from flue gas. Metal–organic frameworks (MOFs) with characteristics like high porosity have great potential as membrane materials for gas mixture separation. In this work, through a combination of grand canonical Monte Carlo and molecular dynamics simulations, the permeability of three gases (CO₂, N₂, and O₂) was calculated and estimated in 6013 computation–ready experimental MOF membranes (CoRE–MOFMs). Then, the relationship between structural descriptors and permeance performance, and the importance of available permeance area to permeance performance of gas molecules with smaller kinetic diameters were found by univariate analysis. Furthermore, comparing the prediction accuracy of seven classification machine learning algorithms, XGBoost was selected to analyze the order of importance of six structural descriptors to permeance performance, through which the conclusion of the univariate analysis was demonstrated one more time. Finally, seven promising CoRE-MOFMs were selected, and their structural characteristics were analyzed. This work provides explicit directions and powerful guidelines to experimenters to accelerate the research on membrane separation for the purification of flue gas. Full article

(This article belongs to the Special Issue Preparation of Organic-Inorganic Hybrid Membranes and Their Membrane Performance)

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20 pages, 5574 KiB

Open AccessArticle

Cobalt-Based Cathode Catalysts for Oxygen-Reduction Reaction in an Anion Exchange Membrane Fuel Cell

by Tar-Hwa Hsieh, Yen-Zen Wang and Ko-Shan Ho

Membranes 2022, 12(7), 699; https://doi.org/10.3390/membranes12070699 - 11 Jul 2022

Cited by 8 | Viewed by 1784

Abstract

A novel cobalt-chelating polyimine (Co-PIM) containing an additional amine group is prepared from the condensation polymerization of diethylene triamine (DETA) and terephthalalehyde (PTAl) by the Schiff reaction. A Co, N-co-doped carbon material (Co-N-C), obtained from two-stage calcination in different gas atmospheres is used [...] Read more.

A novel cobalt-chelating polyimine (Co-PIM) containing an additional amine group is prepared from the condensation polymerization of diethylene triamine (DETA) and terephthalalehyde (PTAl) by the Schiff reaction. A Co, N-co-doped carbon material (Co-N-C), obtained from two-stage calcination in different gas atmospheres is used as the cathode catalyst of an anion exchange membrane fuel cell (AEMFC). The Co-N-C catalyst demonstrates a CoNx-type single-atom structure seen under high-resolution transmission electron microscopy (HRTEM). The Co-N-C catalysts are characterized by FTIR, XRD, and Raman spectroscopy as well. Their morphologies are also illustrated by SEM and TEM micrographs, respectively. Surface area and pore size distribution are found by BET analysis. Co-N-C catalysts exhibit a remarkable oxygen reduction reaction (ORR) at 0.8 V in the KOH(aq). From the LSV (linear-sweeping voltammetry) curves, the onset potential relative to RHE is 1.19–1.37 V, the half wave potential is 0.73–0.78 V, the Tafel slopes are 76.9–93.6 mV dec⁻¹, and the average number of exchange electrons is 3.81. The limiting reduction current of CoNC-1000A-900 is almost the same as that of commercial 20 wt% Pt-deposited carbon particles (Pt/C), and the max power density (P_max) of the single cell using CoNC-1000A-900 as the cathode catalyst reaches 361 mW cm⁻², which is higher than Pt/C (284 mW cm⁻²). Full article

(This article belongs to the Special Issue Advances in Porous and Dense Membranes: Fabrication and Applications)

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17 pages, 4471 KiB

Open AccessArticle

Seaweed and Dendritic Growth in Unsaturated Fatty Acid Monolayers

by Florian Gellert, Heiko Ahrens, Harm Wulff and Christiane A. Helm

Membranes 2022, 12(7), 698; https://doi.org/10.3390/membranes12070698 - 08 Jul 2022

Cited by 3 | Viewed by 2430

Abstract

The lateral movement in lipid membranes depends on their diffusion constant within the membrane. However, when the flux of the subphase is high, the convective flow beneath the membrane also influences lipid movement. Lipid monolayers of an unsaturated fatty acid at the water–air [...] Read more.

The lateral movement in lipid membranes depends on their diffusion constant within the membrane. However, when the flux of the subphase is high, the convective flow beneath the membrane also influences lipid movement. Lipid monolayers of an unsaturated fatty acid at the water–air interface serve as model membranes. The formation of domains in the liquid/condensed coexistence region is investigated. The dimension of the domains is fractal, and they grow with a constant growth velocity. Increasing the compression speed of the monolayer induces a transition from seaweed growth to dendritic growth. Seaweed domains have broad tips and wide and variable side branch spacing. In contrast, dendritic domains have a higher fractal dimension, narrower tips, and small, well-defined side branch spacing. Additionally, the growth velocity is markedly larger for dendritic than seaweed growth. The domains’ growth velocity increases and the tip radius decreases with increasing supersaturation in the liquid/condensed coexistence region. Implications for membranes are discussed. Full article

(This article belongs to the Special Issue Model Lipid Membrane)

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15 pages, 4452 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Study on Biofouling and Cleaning of Anion Exchange Membranes for Reverse Electrodialysis

by Gonçalo Tiago, Maria Beatriz Cristóvão, Ana Paula Marques, Rosa Huertas, Ivan Merino-Garcia, Vanessa Jorge Pereira, João Goulão Crespo and Svetlozar Velizarov

Membranes 2022, 12(7), 697; https://doi.org/10.3390/membranes12070697 - 08 Jul 2022

Cited by 7 | Viewed by 2486

Abstract

This study covers the modification, (bio)fouling characterization, use, and cleaning of commercial heterogeneous anion exchange membranes (AEMs) to evaluate their feasibility for reverse electrodialysis (RED) applications. A surface modification with poly (acrylic) acid resulted in an improved monovalent perm-selectivity (decreased sulfate membrane transport [...] Read more.

This study covers the modification, (bio)fouling characterization, use, and cleaning of commercial heterogeneous anion exchange membranes (AEMs) to evaluate their feasibility for reverse electrodialysis (RED) applications. A surface modification with poly (acrylic) acid resulted in an improved monovalent perm-selectivity (decreased sulfate membrane transport rate). Moreover, we evaluated the (bio)fouling potential of the membrane using sodium dodecyl sulfate (SDS), sodium dodecyl benzenesulfonate (SDBS), and Aeromonas hydrophila as model organic foulants and a biofoulant, respectively. A detailed characterization of the AEMs (water contact angle, ion exchange capacity (IEC), scanning electron microscopy (SEM), cyclic voltammetry (CV), and Fourier Transform Infrared (FTIR) spectra) was carried out, verifying that the presence of such foulants reduces IEC and the maximum current obtained by CV. However, only SDS and SDBS affected the contact angle values. Cleaning of the biofouled membranes using a sodium hypochlorite aqueous solution allows for (partially) recovering their initial properties. Furthermore, this work includes a fouling characterization using real surface and sea water matrixes, confirming the presence of several types of fouling microorganisms in natural streams. A lower adhesion of microorganisms (measured in terms of total bacteria counts) was observed for the modified membranes compared to the unmodified ones. Finally, we propose a cleaning strategy to mitigate biofouling in AEMs that could be easily applied in RED systems for an enhanced long-term process performance. Full article

(This article belongs to the Special Issue Electrochemical Membranes: Materials, Characterization, Testing, and Cleaning)

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24 pages, 3006 KiB

Open AccessArticle

The PH Domain and C-Terminal polyD Motif of Phafin2 Exhibit a Unique Concurrence in Animals

by Mahmudul Hasan and Daniel G. S. Capelluto

Membranes 2022, 12(7), 696; https://doi.org/10.3390/membranes12070696 - 07 Jul 2022

Cited by 1 | Viewed by 2654

Abstract

Phafin2, a member of the Phafin family of proteins, contributes to a plethora of cellular activities including autophagy, endosomal cargo transportation, and macropinocytosis. The PH and FYVE domains of Phafin2 play key roles in membrane binding, whereas the C-terminal poly aspartic acid (polyD) [...] Read more.

Phafin2, a member of the Phafin family of proteins, contributes to a plethora of cellular activities including autophagy, endosomal cargo transportation, and macropinocytosis. The PH and FYVE domains of Phafin2 play key roles in membrane binding, whereas the C-terminal poly aspartic acid (polyD) motif specifically autoinhibits the PH domain binding to the membrane phosphatidylinositol 3-phosphate (PtdIns3P). Since the Phafin2 FYVE domain also binds PtdIns3P, the role of the polyD motif remains unclear. In this study, bioinformatics tools and resources were employed to determine the concurrence of the PH-FYVE module with the polyD motif among Phafin2 and PH-, FYVE-, or polyD-containing proteins from bacteria to humans. FYVE was found to be an ancient domain of Phafin2 and is related to proteins that are present in both prokaryotes and eukaryotes. Interestingly, the polyD motif only evolved in Phafin2 and PH- or both PH-FYVE-containing proteins in animals. PolyD motifs are absent in PH domain-free FYVE-containing proteins, which usually display cellular trafficking or autophagic functions. Moreover, the prediction of the Phafin2-interacting network indicates that Phafin2 primarily cross-talks with proteins involved in autophagy, protein trafficking, and neuronal function. Taken together, the concurrence of the polyD motif with the PH domain may be associated with complex cellular functions that evolved specifically in animals. Full article

(This article belongs to the Section Biological Membrane Composition and Structures)

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14 pages, 5079 KiB

Open AccessArticle

High Methoxyl Pectin and Sodium Caseinate Film Matrix Reinforced with Green Carbon Quantum Dots: Rheological and Mechanical Studies

by Clarissa Murru, Mohammad Amin Mohammadifar, Jakob Birkedal Wagner, Rosana Badía Laiño and Marta Elena Díaz García

Membranes 2022, 12(7), 695; https://doi.org/10.3390/membranes12070695 - 07 Jul 2022

Cited by 5 | Viewed by 1778

Abstract

Nowadays, proteins and polysaccharides play a fundamental role in the manufacturing of biocompatible materials applied in food packaging. The resulting films have, however, limits associated with the resistance to mechanical stress; therefore, it is important to reinforce the initial mixture with additives that [...] Read more.

Nowadays, proteins and polysaccharides play a fundamental role in the manufacturing of biocompatible materials applied in food packaging. The resulting films have, however, limits associated with the resistance to mechanical stress; therefore, it is important to reinforce the initial mixture with additives that promote the development of stronger molecular links. Carbon dots (CDs) are excellent candidates for this purpose due to the presence of surface functional groups that determine the formation of numerous intramolecular bonds between the charged biopolymers. The present research aims to evaluate the effect of CDs on the mechanical properties of biopolymer films obtained from sodium caseinate (CAS), high methoxyl pectin (HMP) and glycerol used as plasticizers. Green carbon dots (gCDs) were obtained from natural organic sources by green synthesis. The effects of gCDs on the flow behavior and viscoelastic properties of mixed biopolymer dispersions and the thermophysical properties of the corresponded films were evaluated by steady and unsteady shear rheological measurements and differential scanning calorimetry (DSC) tests, respectively. The dynamic mechanical measurements were realized taking into account the parameters of temperature and relative humidity. The results indicate a significant change in the viscosity of the protein–polysaccharide dispersions and the thermomechanical properties of the corresponding film samples reinforced with higher amounts of gCDs. Full article

(This article belongs to the Special Issue Advanced Nanomembranes for Food and Food-Packaging Applications)

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16 pages, 2974 KiB

Open AccessArticle

Mechanism Study of Proteins under Membrane Environment

by Yue Zhang, Xiaohong Zhu, Honghui Zhang, Junfang Yan, Peiyi Xu, Peng Wu, Song Wu and Chen Bai

Membranes 2022, 12(7), 694; https://doi.org/10.3390/membranes12070694 - 07 Jul 2022

Viewed by 1882

Abstract

Membrane proteins play crucial roles in various physiological processes, including molecule transport across membranes, cell communication, and signal transduction. Approximately 60% of known drug targets are membrane proteins. There is a significant need to deeply understand the working mechanism of membrane proteins in [...] Read more.

Membrane proteins play crucial roles in various physiological processes, including molecule transport across membranes, cell communication, and signal transduction. Approximately 60% of known drug targets are membrane proteins. There is a significant need to deeply understand the working mechanism of membrane proteins in detail, which is a challenging work due to the lack of available membrane structures and their large spatial scale. Membrane proteins carry out vital physiological functions through conformational changes. In the current study, we utilized a coarse-grained (CG) model to investigate three representative membrane protein systems: the TMEM16A channel, the family C GPCRs mGlu2 receptor, and the P4-ATPase phospholipid transporter. We constructed the reaction pathway of conformational changes between the two-end structures. Energy profiles and energy barriers were calculated. These data could provide reasonable explanations for TMEM16A activation, the mGlu2 receptor activation process, and P4-ATPase phospholipid transport. Although they all belong to the members of membrane proteins, they behave differently in terms of energy. Our work investigated the working mechanism of membrane proteins and could give novel insights into other membrane protein systems of interest. Full article

(This article belongs to the Special Issue Membrane Process Systems and Techniques)

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