Self-assembled Membranes Research Articles

Low Fouling Polyelectrolyte Layer-by-Layer Self-Assembled Membrane for High Performance Dye/Salt Fractionation: Sequence Effect of Self-Assembly.

Layer-by-layer (LbL) self-assembly of oppositely charged polyelectrolytes (PEs) is usually performed on a conventional ultrafiltration base substrate (negative zeta potential) by depositing a cationic PE as a first layer. Herein, we report the facile and fast formation of high performance molecular selective membrane by the nonelectrostatic adsorption of anionic PE on the polyvinylidene fluoride (PVDF, zeta potential -17 mV) substrate followed by the electrostatic LbL assembly. Loose nanofiltration membranes have been prepared via both concentration-polarization (CP-LbL, under applied pressure) driven and conventional (C-LbL, dipping) LbL self-assembly. When the first layer is poly(styrene sodium) sulfonic acid, the LbL assembled membrane contains free -SO3- groups and exhibits higher rejection of Na2SO4 and lower rejection of MgCl2. The reversal of salt rejection occurs when the first layer is quaternized polyvinyl imidazole (PVIm-Me). The membrane (five layers) prepared by first depositing PStSO3Na shows higher rejection of several dyes (97.9 to >99.9%), higher NaCl to dye separation factor (52-1800), and higher dye antifouling performance as compared to the membrane prepared by first depositing PVIm-Me (97.5-99.5% dye rejection, separation factor ∼40-200). However, the C-LbL membrane requires a longer time of self-assembly or higher PE concentration to reach a performance close to the CP-LbL membranes. The membranes exhibit excellent pressure, pH (3-12), and salt (60 g L-1) stability. This work provides an insight for the construction of low fouling and high-performance membranes for the fractionation of dye and salt based on the LbL self-assembly sequence.

Large-area, self-healing block copolymer membranes for energy conversion

Membranes are widely used for separation processes in applications such as water desalination, batteries and dialysis, and are crucial in key sectors of our economy and society1. The majority of technologically exploited membranes are based on solid polymers and function as passive barriers, whose transport characteristics are governed by their chemical composition and nanostructure. Although such membranes are ubiquitous, it has proved challenging to maximize selectivity and permeability independently, leading to trade-offs between these pertinent characteristics2. Self-assembled biological membranes, in which barrier and transport functions are decoupled3,4, provide the inspiration to address this problem5,6. Here we introduce a self-assembly strategy that uses the interface of an aqueous two-phase system to template and stabilize molecularly thin (approximately 35 nm) biomimetic block copolymer bilayers of scalable area that can exceed 10 cm2 without defects. These membranes are self-healing, and their barrier function against the passage of ions (specific resistance of approximately 1 MΩ cm2) approaches that of phospholipid membranes. The fluidity of these membranes enables straightforward functionalization with molecular carriers that shuttle potassium ions down a concentration gradient with exquisite selectivity over sodium ions. This ion selectivity enables the generation of electric power from equimolar solutions of NaCl and KCl in devices that mimic the electric organ of electric rays.

Self-assembled network polymer electrolyte membranes for application in fuel cells at 250 °C

Self-assembled network polymer electrolyte membranes for application in fuel cells at 250 °C

Completely recyclable and reusable automatic phase-separable catalytic system for the reductive debromination of polybrominated diphenyl ethers

An automatic phase-separable catalytic system was developed for the reductive debromination of polybrominated diphenyl ethers (PBDEs) using thiol-modified Pd nanoparticles (thiol-Pd NPs) as the catalyst, H2 as the reducing agent, and n-butanol (oil phase) and water (water phase) as solvents. This system achieved efficient and complete debromination of various PBDEs with 1–10 bromine atoms and other bromo-organic pollutants at concentrations ranging from 15 to 1500 mg L−1. Typically, this system achieved a debromination efficiency of 100 % within 15 min for all the tested bromo-organic pollutants. Importantly, the debromination reaction was conducted in a microemulsion state under stirring; upon stopping the stirring, the microemulsion automatically separated into an upper oil phase, a down water phase, and a thiol-Pd NP self-assembled membrane phase at the oil/water interface. These three phases could be easily separated from each other, allowing for their reuse across multiple debromination cycles with good reusability. The thiol modifier enhanced the stability and reusability of Pd NPs and improved the adsorption of PBDEs, facilitating their reaction with atomic hydrogen (the dominant reactive species). This method successfully eliminated PBDEs in soils by integrating with a pre-extraction process.

Self-Assembled Hydrogel Membranes with Structurally Tunable Mechanical and Biological Properties.

Using supramolecular self-assembled nanocomposite materials made from protein and polysaccharide components is becoming more popular because of their unique properties, such as biodegradability, hierarchical structures, and tunable multifunctionality. However, the fabrication of these materials in a reproducible way remains a challenge. This study presents a new evaporation-induced self-assembly method producing layered hydrogel membranes (LHMs) using tropocollagen grafted by partially deacetylated chitin nanocrystals (CO-g-ChNCs). ChNCs help stabilize tropocollagen's helical conformation and fibrillar structure by forming a hierarchical microstructure through chemical and physical interactions. The LHMs show improved mechanical properties, cytocompatibility, and the ability to control drug release using octenidine dihydrochloride (OCT) as a drug model. Because of the high synergetic performance between CO and ChNCs, the modulus, strength, and toughness increased significantly compared to native CO. The biocompatibility of LHM was tested using the normal human dermal fibroblast (NHDF) and the human osteosarcoma cell line (Saos-2). Cytocompatibility and cell adhesion improved with the introduction of ChNCs. The extracted ChNCs are used as a reinforcing nanofiller to enhance the performance properties of tropocollagen hydrogel membranes and provide new insights into the design of novel LHMs that could be used for various medical applications, such as control of drug release in the skin and bone tissue regeneration.

Self-Assembled Nanofiltration Membranes with Thermo- and pH-Responsive Behavior

Self-Assembled Nanofiltration Membranes with Thermo- and pH-Responsive Behavior

Scaling the Functional Nanopore (FuN) Screen: Systematic Evaluation of Self-Assembling Membrane Peptides and Extension with a K+-Responsive Fluorescent Protein Sensor.

The functional analysis of protein nanopores is typically conducted in planar lipid bilayers or liposomes exploiting high-resolution but low-throughput electrical and optical read-outs. Yet, the reconstitution of protein nanopores in vitro still constitutes an empiric and low-throughput process. Addressing these limitations, nanopores can now be analyzed using the functional nanopore (FuN) screen exploiting genetically encoded fluorescent protein sensors that resolve distinct nanopore-dependent Ca2+ in- and efflux patterns across the inner membrane of Escherichia coli. With a primary proof-of-concept established for the S2168 holin, and thereof based recombinant nanopore assemblies, the question arises to what extent alternative nanopores can be analyzed with the FuN screen and to what extent alternative fluorescent protein sensors can be adapted. Focusing on self-assembling membrane peptides, three sets of 13 different nanopores are assessed for their capacity to form nanopores in the context of the FuN screen. Nanopores tested comprise both natural and computationally designed nanopores. Further, the FuN screen is extended to K+-specific fluorescent protein sensors and now provides a capacity to assess the specificity of a nanopore or ion channel. Finally, a comparison to high-resolution biophysical and electrophysiological studies in planar lipid bilayers provides an experimental benchmark for future studies.

Interface self-assembly of plasmonic nanolayer for sensitive detection of heavy metals in water using NELIBS

Nowadays, high-stable and ultrasensitive heavy metal detection is of utmost importance in water quality monitoring. Nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) shows high potential in hazardous metal detection, however, encounters unstable and weak signals due to nonuniform distribution of analytes. Herein, we developed an interface self-assembly (ISA) method to create a uniformly distributed gold nanolayer at a liquid-liquid interface for positive heavy metal ions capture and NELIBS analysis. The electrostatically self-assembled Au nanoparticles (NPs)-analytes membrane was prepared at the oil-water interface by injecting ethanol into the mixture of cyclohexane and Au NPs-analytes water solution. Then, the interface self-assembled Au NPs-analytes membrane was transformed onto a laser-processed superhydrophilic Si slide for detection. Three heavy metals (cadmium (Cd), barium (Ba), and chromium (Cr)) were analyzed to evaluate the stability and sensitivity of the ISA method for NELIBS. The results (Cd: RSD ​= ​3.6 ​%, LoD ​= ​0.654 ​mg/L; Ba: RSD ​= ​3.4 ​%, LoD ​= ​0.236 ​mg/L; Cr: RSD ​= ​7.7 ​%, LoD ​= ​1.367 ​mg/L) demonstrated signal enhancement and high-stable and ultrasensitive detection. The actual sample detection (Cd: RE ​= ​7.71 ​%, Ba: RE ​= ​6.78 ​%) illustrated great reliability. The ISA method, creating a uniform distribution of NP-analytes at the interface, has promising prospects in NELIBS.

Abstract 1069: Interrogating the role of the cGAS/STING pathway fallopian tube transformation

Abstract Ovarian Cancer is the deadliest gynecologic malignancy. Despite recent advances in cancer diagnostics, it is a cancer that is often detected late and the vast majority of patients are diagnosed at Stage III and Stage IV. After treatment with debulking surgery and chemotherapy, 80% of patients have tumor relapse with increasing resistance. Early detection efforts have been largely unsuccessful and the only effective prevention strategy in high risk patients is surgical removal of the fallopian tube and ovaries. Careful pathologic studies of prophylactic risk reducing bilateral salpingo-oophorectomy (RRSO) has demonstrated that HGSC originates in the fallopian tube. Within the fallopian tube, secretory cells within the fimbriae are believed to be the origin of HGSC based on numerous lines of correlative evidence including the identification of histologically and molecularly abnormal regions in the fallopian tube called serous tubal intraepithelial cancer (STIC) in 3-5% of patients undergoing RRSO, and the presence of STIC in approximately half of patients undergoing debulking surgeries for HGSC. Finally, p53 mutations have been found to be identical in STIC and in the concurrent invasive disease indicating that HGSC and the STIC likely arise from the same clone. TCGA analysis has demonstrated that HCSC is a disease characterized by genomic and chromosomal instability harboring copy number alteration, including amplifications, deletions and more complex chromosomal rearrangements which impact multiple genes and pathways. Aberrantly segregating chromosomes that lag behind the spindle apparatus fail to become part of the primary nucleus (PN) and are instead enclosed by a self-assembled nuclear membrane, creating a structure called the micronucleus (MN). Spontaneous breakdown of the MN causes cytoplasmic DNA sensing and activation of the cGAS-STING pathway, an important innate cellular defense mechanism to foreign cytoplasmic DNA. To better understand the early genomic and signaling events in the development of HGSC, we are interrogating tissue from our archives from MSKCC patients who have undergone RRSO, hormone ablation surgeries or surgical debulking and were found to have benign fallopian tube, STIC lesions or invasive HGSC with STIC. We have performed a pilot experiment of 20 patient samples of different germline genetic backgrounds. Intriguingly, cGAS signaling was observed only rarely in the STICs indicating low rates of CIN in STICs we have evaluated, however we note that even in early invasive disease, we observe cGAS positivity. Taken together, these data are consistent with a model where CIN and subsequent cGAS/STING pathway activation drives the transition from pre-invasive to invasive disease. Citation Format: Duaa Hassan Al-Rawi, Danguole Norkunaite, Samuel Bakhoum, Sohrab Shah. Interrogating the role of the cGAS/STING pathway fallopian tube transformation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1069.

Piezocatalytic property of PVDF/Graphene self-assembling piezoelectric membrane for environmental remediation

In recent years, industrial pollution has become an inescapable global issue. The catalytic degradation processes driven by environmental sources, such as photocatalysis and piezocatalysis, are among the effective solutions. However, the difficulty in recycling catalysts leads to secondary pollution, limiting their practical application. This study develops a graphene-based self-assembled piezocatalytic membrane. Through Non-solvent Induced Phase Separation (NIPS), polyvinylidene fluoride (PVDF)/graphene asymmetrical membrane was prepared. The addition of graphene induced the self-assembly of PVDF crystalline phases into piezoelectric β phase. The membrane generates the ROS species to degrade the pollutant by the screen charge from material surface under a piezoelectric field. The optimal membrane exhibits the highest Vpp value of 4.26 V, and significant degradation efficiency of 80.2 % and 85.6 % for methylene blue (MnB) and crystal violet (CV), respectively, which are positively charged dyes. Meanwhile, the degradation efficiency within 2 h reached 73.8 % for negatively charged methyl orange (MO) and 96.1 % for toxic rhodamine B (RhB). This study successfully developed a crystalline self-assembled piezocatalytic membrane, providing fundamental insights into its piezoelectric response and various pollutant degradation. It introduces new directions and possibilities for the future development of membrane-based piezocatalysis.

Self-assembled ultrathick MoS2 conductive hydrogel membrane via ionic gelation for superior capacitive energy storage

Conductive hydrogel membranes with nanofluids channels represent one of the most promising capacitive electrodes due to their rapid kinetics of ion transport. The construction of these unique structures always requires new self-assembly behaviors with different building blocks, intriguing phenomena of colloidal chemistry. In this work, by delicately balancing the electrostatic repulsions between 2D inorganic nanosheets and the electrostatic adsorption with cations, we develop a general strategy to fabricate stable free-standing 1T molybdenum disulphide (MoS2) hydrogel membranes with abundant fluidic channels. Given the interpenetrating ionic transport network, the MoS2 hydrogel membranes exhibit a high-level capacitive performance 1.34 F/cm2 at an ultrahigh mass loading of 11.2 mg/cm2. Furthermore, the interlayer spacing of MoS2 in the hydrogel membranes can be controlled with ångström-scale precision using different cations, which can promote further fundamental studies and potential applications of the transition-metal dichalcogenides hydrogel membranes.

ACEK Biosensor for the Minute-Scale Quantification of Breast Cancer ctDNA.

Circulating tumor DNA (ctDNA) appears as a valuable liquid biopsy biomarker in the early diagnosis, treatment, and prognosis of cancer. Here, a biosensing method derived from the AC electrokinetics (ACEK) effect was constructed in this study for the simple, efficient, and rapid method of detection of ctDNA. In the proof-of-concept experiment, ctDNA from the PIK3CA E542K mutant in breast cancer was quantified by detecting a normalized capacitance change rate using a forked-finger gold electrode as the sensing electrode in combination with the ACEK effect. We compared two formats for the construction of the approach by employing varied immobilization strategies; one is to immobilize the DNA capture probe on the electrode surface by Au-S bonding, while the other immobilizes the probe on a self-assembled membrane on the electrode surface by amide bonding. Both formats demonstrated ultrafast detection speed by completing the ctDNA quantification within 1 min and a linear range of 10 fM-10 pM was observed. Meanwhile, the immobilization via the self-assembled membrane yielded improved stability, sensitivity, and specificity than its Au-S bonding counterpart. A detection limit of 1.94 fM was eventually achieved using the optimized approach. This research provides a label-free and minute-scale universal method for the detection of various malignant tumors. The ctDNA biosensors based on the ACEK effect improved according to the probe type or electrode structure and have potential applications in tumor drug efficacy prediction, drug resistance monitoring, screening of high-risk groups, differential diagnosis, monitoring of tiny residual lesions, and prognosis determination.

Self-assembled dendrimer polyamide nanofilms with enhanced effective pore area for ion separation

Membrane technology using well-defined pore structure can achieve high ion purity and recovery. However, fine-tuning the inner pore structure of the separation nanofilm to be uniform and enhance the effective pore area is still challenging. Here, we report dendrimers with different peripheral groups that preferentially self-assemble in aqueous-phase amine solution to facilitate the formation of polyamide nanofilms with a well-defined effective pore range and uniform pore structure. The high permeabilities are maintained by forming asymmetric hollow nanostripe nanofilms, and their well-designed ion effective separation pore ranges show an enhancement, rationalized by molecular simulation. The self-assembled dendrimer polyamide membrane provides Cl–/SO42– selectivity more than 17 times that of its pristine polyamide counterparts, increasing from 167.9 to 2883.0. Furthermore, the designed membranes achieve higher Li purity and Li recovery compared to current state-of-the-art membranes. Such an approach provides a scalable strategy to fine-tune subnanometre structures in ion separation nanofilms.

Smart membranes for separation and sensing.

Self-assembled membranes are extensively applied across various fields due to their non-thermal and low-carbon footprint characteristics. Recently, smart membranes with stimuli responsiveness have garnered significant attention for their ability to alter physical and chemical properties in response to different stimuli, leading to enhanced performance and a wider range of applications compared to traditional membranes. This review highlights the recent advancements in self-assembled smart membranes, beginning with widely used membrane preparation strategies such as interfacial polymerization and blending. Then it delves into the primary types of stimuli-responses, including light, pH, and temperature, illustrated in detail with relevant examples. Additionally, the review explores the latest progress in the use of smart membranes for separation and sensing, addressing the challenges and opportunities in both fields. This review offers new insights into the design of novel smart membrane platforms for sustainable development and provides a broader perspective on their commercial potential.

Structure and transport properties of self-assembled nanofiltration membranes based on sustainably derived materials

The development of functional polymers using sustainable resources is an increasingly important pursuit. Unsaturated fatty acids represent a potentially interesting class of renewable materials for this purpose. Their unsaturated carbon bonds permit crosslinking to form solid polymers. Additionally, their carboxylic acid functional groups provide for the display of specific surface chemistry within the resulting polymers, and also enable chemical derivatization. Here, we explore the fabrication of nanometer-scale size-selective membranes using conjugated linoleic acid derived monomers. Potassium salt conjugated linoleic acid surfactants (KCLA) self-assembled to form hexagonally packed cylinders (HI) in an aqueous medium containing glycerol. This structure provides a highly ordered medium with aqueous-continuous channels for nanofiltration. The HI mesophase was crosslinked with the addition of bifunctional comonomers and the ordered structure was retained with good fidelity in the resulting thin polymer films (< 400 nm thick). These film function effectively as nanofiltration membranes, with a size cut-off of approximately 1.2 nm for charged solutes, while maintaining a high permeance of ∼ 9 LMH/bar. This performance is on par with several commercial nanofiltration membranes and these materials are therefore of potential interest for advancing sustainability concerns in practical nanofiltration applications.

A versatile route for the fabrication of micro-patterned polylactic-acid (PLA)-based membranes with tailored morphology via breath figure imprinting.

Breath figure imprinting, based on surface instabilities combined with fast polymer evaporation in a humid environment, enables the creation of micro-patterned membranes with tailored pore sizes. Despite being a simple procedure, it is still challenging to fully understand the dynamics behind the formation of hierarchical structuring. In this work, we used the breath figure technique to prepare porous PLA-based (polylactic acid) membranes with two distinctive additives, polyvinylidene fluoride (PVDF) and zinc oxide nanoparticles (ZnO NPs). The selection of these additives was governed by their unique properties and the potential synergistic effects; when blended with PLA, the addition of NPs leads to more uniform structures with tunable characteristics and potential multifunctionality. This article sheds light on the multifaced interactions that intricate the interplays between PLA, PVDF, and ZnO, thus governing their assembly. Through a comprehensive investigation, we scrutinize the impact of blending PVDF and different concentrations of ZnO NPs on the morphology and chemical properties of the final self-assembled PLA membranes while presenting an advanced understanding of the potential applications of PLA-self-assembly porous membranes in various industrial sectors.

Molecular dynamics simulations reliably identify vibrational modes in far-IR spectra of phospholipids.

The properties of self-assembled phospholipid membranes are of essential importance in biochemistry and physical chemistry, providing a platform for many cellular life functions. Far-infrared (far-IR) vibrational spectroscopy, on the other hand, is a highly information-rich method to characterize intermolecular interactions and collective behaviour of lipids that can help explain, e.g., chain packing, thermodynamic phase behaviour, and sequestration. However, reliable interpretation of the far-IR spectra is still lacking. Here we present a molecular dynamics (MD) based approach to simulate vibrational modes of individual lipids and in an ensemble. The results are a good match to synchrotron far-IR measurements and enable identification of the molecular motions corresponding to each vibrational mode, thus allowing the correct interpretation of membrane spectra with high accuracy and resolving the longstanding ambiguities in the literature in this regard. Our results demonstrate the feasibility of using MD simulations for interpreting far-IR spectra broadly, opening new avenues for practical use of this powerful method.

Self-assembled nanostructured membranes with tunable pore size and shape from plant-derived materials.

Nanostructured materials derived from sustainable sources are of interest as viable alternatives to traditional petroleum-derived sources in membrane applications due to environmental concerns. Here, we present the development of pore size-tunable nanostructured polymer membranes based on a plant-derived material. The membranes were fabricated using a tri-functional amine as the templating core species and a cross-linkable ligand synthesized from rose oil-derived citronellol. The self-assembly of a supramolecular complex between the template core and the ligand forms a hexagonally packed columnar (Colh) mesophase, the dimensions of which can be precisely controlled by changing the stoichiometric ratio between these constituents. Within the hexagonal mesophase stoichiometric range, the pore size of the nanostructured membranes can be tuned from 1.0 to 1.3 nm, with a step size of approximately 0.1 nm. The membranes exhibited a clear distinction in molecular size selectivity, as demonstrated by dye adsorption experiments. The membrane fabricated with a ligand-to-core ratio of 3 to 1 demonstrated shape-based selectivity, exhibiting a higher permeability for propeller-shaped penetrants and highlighting its potential for shape-selective transport. We anticipate that this straightforward approach, using plant-derived materials, can contribute to important sustainability aspects while enhancing the performance of current state-of-the-art nanostructured membranes by enabling precise control over pore size.

Classification of binding property of amyloid β to lipid membranes: Membranomic research using quartz crystal microbalance combined with the immobilization of lipid planar membranes

A biomembrane-related fibrillogenesis of Amyloid β from Alzheimer’ disease (Aβ) is closely related to its accumulation behavior. A binding property of Aβ peptides from Alzheimer’ disease to lipid membranes was then classified by a quartz crystal microbalance (QCM) method combined with an immobilization technique using thiol self-assembled membrane. The accumulated amounts of Aβ, Δfmax, was determined from the measurement of the maximal frequency reduction using QCM. The plots of Δfmax to Aβ concentration gave the slope and saturated value of Δfmax, (Δfmax)sat that are the parameters for binding property of Aβ to lipid membranes. Therefore, the Aβ-binding property on lipid membranes was classified by the slope and (Δfmax)sat. The plural lipid system was described as X + Y where X = L1, L1/L2, and L1/L2/L3. The slope and (Δfmax)sat values plotted as a function of mixing ratio of Y to X was classified on a basis of the lever principle (LP). The LP violation observed in both parameters resulted from the formation of the crevice or pothole, as Aβ-specific binding site, generated at the boundary between ld and lo phases. The LP violation observed only in the slope resulted from glycolipid-rich domain acting as Aβ-specific binding site. Furthermore, lipid planar membranes indicating strong LP violation favored strong fibrillogenesis. Especially, lipid planar membranes indicating the LP violation only in the slope induced lateral aggregated and spherulitic fibrillar aggregates. Thus, the classification of Aβ binding property on lipid membranes appeared to be related to the fibrillogenesis with a certain morphology.

Effect of substrate morphology on characteristics of layer-by-layer self-assembly nanofiltration membrane for micropollutants removal

Layer-by-layer (LBL) hollow fiber nanofiltration (NF) membranes have emerged as a promising technology for the removal of micropollutants (MPs). Previous research has been largely focused on polyelectrolyte pairs and coating parameters. This paper studied the substrate morphology, a critical factor often being overlooked. Poly (allylamine hydrochloride) /poly (styrene sulfonic acid) sodium salt (PAH/PSS) coating was utilized to evaluate the impact of the substrate morphology. Two polyethersulfone substrates were selected: Substrate 1# with dense skins at both lumen/shell and Substrate 2# with skin at the lumen and an open shell surface. All LBL NF membranes showed molecular weight cut-off ranging from 180 to 223 Da and MgCl2 rejection around 94 %. For LBL membrane 1#, with coatings on both shell/lumen sides, the outer coating was defective due to scratches. For LBL membrane 2# with a coating at the lumen, significant PAH overcompensation was observed, because of the open inner and outer surfaces comparing to LBL membrane 1#. Higher rejection to positively charged MPs was resulted from Donnan effect, outperforming steric exclusion. The backwash stability of both membranes was excellent and independent of the substrate structure. This work provides a basis for substrate selection for fabricating LBL NF membranes.