Self-assembled Membranes Research Articles

Cofactors-like peptide self-assembly exhibiting the enhanced catalytic activity in the peptide-metal nanocatalysts

The peptide self-assembly would be expected to be as the assistance of metallic nanocatalysts to promote the catalytic reaction, attracting limited attention, but being highly anticipated. Herein, we proposed and verified an alternative strategy for enhancing the catalytic activity of the 4-nitrophenol reduction as a model reaction, by optimizing and constructing “cofactors” inspired amyloid peptide self-assembly applied in the peptide-metal nanocatalysts as the template due to the potential superiority of substrate binding. Amyloid peptide self-assembled membrane exhibited better enhanced catalytic activity, compared to peptide nanofibers as the template in the peptide-gold nanocatalysts. The optimized amyloid peptide was designated by molecular dynamic simulation to display the relative strongest interaction with specific substrate and the relative good template effect on the enhanced catalytic activity was also proved accordingly. This work may shed light on the future design and construction of novel enzyme mimics with dramatic enhanced catalytic activity by peptide assembly-metal nanocatalysts.

Rapidly SO2-responsive vesicles with intrinsic fluorescent indicators for membrane structure evolution

Stimuli-responsive vesicles (SRVs) have been widely exploited as smart nanocarriers for biomedical applications. Herein, high-performance SO2-responsive nanovesicles were reported to exemplify a new mode of SRVs. Structurally, the sensory vesicles were based on amphiphilic hydrogen-bonded (HB) polymers which can be facilely fabricated via modular self-assembly. The HB polymers are designed to consist of a melamine-barbituric acid HB skeleton with pendant anthracene fluorophores and amphiphilic side chains. Upon stimulation with increasing amount of SO2, the vesicles in aqueous solution undergo an unusual morphology evolution including rapid fission into small ones, swelling and final collapse of the offspring vesicles. During this process, the intrinsic fluorescence response of the vesicles allows intuitive tracking of the hierarchical structural evolution of the self-assembled membranes and straightforward quantitation of the stimuli. This work exemplifies a rational design of auto-recording stimuli-responsive nanovesicles.

Composition and sorting of polarized cell plasma membrane compartments

Epithelial cell polarization is an essential biological process, serving many physiological roles including tissue morphogenesis and wound healing. A defining feature of polarization is the separation of cell plasma membrane lipids and proteins into apical and basolateral compartments between which molecular exchange is restricted. Decades ago, the apical membrane was found to be enriched in saturated lipids, glycolipids, and cholesterol. Mechanistic hypotheses to explain the biogenesis and unique composition of the apical membrane include self-assembling membrane domains (i.e., lipid rafts), specific protein sorting motifs, and post-translational modifications mediating protein sorting.

Constructing the basal nanofibers suit of layer-by-layer self-assembly membranes as anion exchange membranes

Anion exchange membranes (AEMs) with layered structures were constructed through the combination of layer-by-layer (LBL) self-assembly membranes and a couple of electrospun nanofibers membranes by the cold pressing method. The LBL self-assembly membranes were formed through alternate depositing positively charged polyurethane (PU), quaternized chitosan (QCS) and negatively charged phosphotungstic acid (HPW). The electrostatic interaction and intermolecular hydrogen bonds drove the LBL self-assembly process. The layered structure facilitated the hydroxide ions conduction owing to the reduced conduction resistance. As a result, (PU/HPW/QCS/HPW)200 membranes exhibited a hydroxide conductivity of 49.1 mS/cm at 80 °C. However, the sustained attack from hydroxyl groups could cause the degradation of polymer skeleton and even the breakdown of membranes. The electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers membranes were combined with the LBL self-assembly membrane, expecting to enhance the chemical stability of AEMs. The external PVDF-HFP nanofibers membranes regulated the hydroxide ions permeation and protected the internal LBL self-assembly membranes from hydroxide ions attracting reminiscent of a breathable and warm sweater. The prepared (PU/HPW/QCS/HPW)200 membranes exhibited the fine stability on the basis of the long-term hydroxide conductivity. Specifically, the hydroxide conductivity of the AEMs was 12.3 mS/cm at 80 °C and it reached 14.3 mS/cm while immersing into 1M KOH at 80 °C for 888 h. Furthermore, the prepared AEMs exhibited fine dimensional stability and mechanical property owing to the compact and well-ordered structure.

Multifactorial engineering of biomimetic membranes for batteries with multiple high-performance parameters

Lithium–sulfur (Li–S) batteries have a high specific capacity, but lithium polysulfide (LPS) diffusion and lithium dendrite growth drastically reduce their cycle life. High discharge rates also necessitate their resilience to high temperature. Here we show that biomimetic self-assembled membranes from aramid nanofibers (ANFs) address these challenges. Replicating the fibrous structure of cartilage, multifactorial engineering of ion-selective mechanical, and thermal properties becomes possible. LPS adsorption on ANF surface creates a layer of negative charge on nanoscale pores blocking LPS transport. The batteries using cartilage-like bioinspired ANF membranes exhibited a close-to-theoretical-maximum capacity of 1268 mAh g−1, up to 3500+ cycle life, and up to 3C discharge rates. Essential for safety, the high thermal resilience of ANFs enables operation at temperatures up to 80 °C. The simplicity of synthesis and recyclability of ANFs open the door for engineering high-performance materials for numerous energy technologies.

Tannic Acid-Mediated Interfacial Layer-by-Layer Self-Assembly of Nanofiltration Membranes for High-Efficient Dye Separation

Tannic Acid-Mediated Interfacial Layer-by-Layer Self-Assembly of Nanofiltration Membranes for High-Efficient Dye Separation

A graphdiyne oxide composite membrane for active electrolyte enhanced supercapacitors with super long self-discharge time

GDYO/PVA self-assembled composite membrane as a separator effectively inhibited the self-discharge of AEESCs. The ultra-long self-discharge time is 37 160 s, and the capacitance retention rate is 95.1% after 8000 cycles.

Expression of concern: Self-assembled membrane manufactured by metal-organic framework (UiO-66) coated γ-Al2O3 for cleaning oily seawater.

Expression of concern for ‘Self-assembled membrane manufactured by metal–organic framework (UiO-66) coated γ-Al2O3 for cleaning oily seawater’ by Cunlong Li et al., RSC Adv., 2019, 9, 10702–10714, DOI: 10.1039/C9RA00521H.

Update to expression of concern: Self-assembled membrane manufactured by metal-organic framework (UiO-66) coated γ-Al2O3 for cleaning oily seawater.

Update to expression of concern for 'Self-assembled membrane manufactured by metal-organic framework (UiO-66) coated γ-Al2O3 for cleaning oily seawater' by Cunlong Li et al., RSC Adv., 2019, 9, 10702-10714, https://doi.org/10.1039/C9RA00521H.

Ionic strength directed self-assembled polyelectrolyte single-bilayer membrane for low-pressure nanofiltration

Ionic strength directed self-assembled polyelectrolyte single-bilayer membrane for low-pressure nanofiltration

Metal-supported self-assembled bilayer lipid membrane incorporated with peroxidase for the detection of peroxide

This work presents a simple, low-cost and ready-to-use peroxide biosensor based on a metal-supported, self-assembled lipid membrane incorporated with horseradish peroxidase. The peroxide sensor showed good analytical and operational characteristics: the detection limit (as S/N = 3) was 0.083 μM and the sensitivity was 1.4071 nA per μM of analyte concentration. The sensor was stable (<5% drift) for 9 h of continuous operation. The validation in real water samples showed that the sensor could reliably detect 0.95 mM of hydrogen peroxide in tap, river and lake water. The reliability of the sensor has been also proven on commercial peroxide formulations, assayed without pretreatment. The prospects and applicability of the proposed biosensor and the underlying technology are also discussed.

A Flexible Plasmonic-Membrane-Enhanced Broadband Tin-Based Perovskite Photodetector.

Lead-free perovskite quantum dots (QDs) have been widely investigated for optoelectronic devices because of their excellent electrical and optical properties. However, optoelectronic devices based on such lead-free perovskites still have much lower performance than those made of Pb-based counterparts. Herein, we developed a lead-free photodetector with an enhanced broadband spectral response ranging from 300 to 630 nm. By balancing plasmonic near-field enhancement and surface energy quenching through precisely controlling the thickness of Al2O3 spacer between the CsSnBr3 QDs and silver nanoparticle membrane, the photodetector with 5 nm thick Al2O3 experiences a maximum photocurrent enhancement of 6.5-fold at 410 nm, with a responsivity of 62.3 mA/W and detectivity of 4.27 × 1011 Jones. Moreover, its photocurrent shows a negligible decrease after 100 cycles of bending, which is ascribed to the tension-offset induced by the self-assembled nanoparticle membrane. The proposed plasmonic membrane enhancement provides a great potential for high-performance perovskite optoelectronic devices.

Combined Effects of Zeta-potential and Temperature of Nanopores on Diffusioosmotic Ion Transport.

Diffusioosmosis (DO) results from ion transport near charged surfaces in the presence of electrolyte gradients and is critical in nanofluidic systems. However, DO has not yet been comprehensively studied because nanofabrication materials have limitations of low throughput and difficult quantification. Herein, we describe a self-assembled particle membrane (SAPM)-integrated microfluidic platform that can modulate the material properties (e.g., zeta-potential) and transport flux of nanopores. We quantify the effect of the zeta-potential on DO by measuring the electrical signals across three different nanopores/nanochannels of the SAPM. We then empirically quantify the effects of the temperature and ionic strength of the electrolytes on DO and reveal a nonlinear relationship with DO-driven ion transport; the ionic strengths govern the DO- or diffusion-effective ion transport phenomena. Finally, we demonstrate DO-driven electric power generation with enhanced performance as a potential application under optimized experimental conditions.

Self-assembled block copolymer electrolyte membranes with silica network-derived nanochannels for all-solid-state supercapacitors

Amphiphilic Block copolymer (BC) membranes, where the BC hydrophilic domain offers a continuous pathway for fast ion transport, while the BC hydrophobic domain provides a scaffold for high mechanical strength, are being widely studied as promising materials for energy storage applications due to their unique morphology with 3-dimensionally continuous macropores. We design silica network-derived poly(styrene)-b-poly(2-vinylpyridine) BC-based hierarchically porous membranes containing high-conducting ionic liquids (ILs) as solid-state electrolytes via nonsolvent-induced phase separation and nonhydrolytic sol–gel process. The introduction of a silica nanoparticle network within the self-assembled BC leads to micro- and nano-scale porous structures. This provides the functionalized BC/IL-based electrolytes (BCEs) with high IL uptake (87 wt%), high dielectric constant (123), low activation energy for ion conduction (6.8 kJ/mol), and high room temperature ionic conductivity (∼10-3 S/cm, comparable to pure IL). The optimized BCE is assembled with activated carbon electrodes, allowing us to fabricate an all-solid-state supercapacitor. The device delivers a broad voltage window (2.5 V), high specific capacitance (∼90 F/g at 0.2 A/g), large energy (E) and power (P) densities (a maximum of E=19 Wh/kg, observed at P=224 W/kg, and a maximum of P=1.3 kW/kg, observed at E=4 Wh/kg), and remarkable electrochemical stability (capacitance retention = 90% for 600 cycles and 76% for 1000 cycles and coulombic efficiency = 100% for 1000 cycles at 0.2 A/g). Therefore, the combination of self-assembly, phase inversion, and in-situ hybridization-derived hierarchical dual-pore construction, providing rapid ion migration, could be a new approach to powering next-generation energy storage devices.

Interaction-based ion selectivity exhibited by self-assembled, cross-linked zwitterionic copolymer membranes

Water filtration membranes with advanced ion selectivity are urgently needed for resource recovery and the production of clean drinking water. This work investigates the separation capabilities of cross-linked zwitterionic copolymer membranes, a self-assembled membrane system featuring subnanometer zwitterionic nanochannels. We demonstrate that selective zwitterion-anion interactions simultaneously control salt partitioning and diffusivity, with the permeabilities of NaClO4, NaI, NaBr, NaCl, NaF, and Na2SO4 spanning roughly three orders of magnitude over a wide range of feed concentrations. We model salt flux using a one-dimensional transport model based on the Maxwell-Stefan equations and show that diffusion is the dominant mode of transport for 1:1 sodium salts. Differences in zwitterion-Cl- and zwitterion-F- interactions granted these membranes with the ultrahigh Cl-/F- permselectivity (PCl-/PF- = 24), enabling high fluoride retention and high chloride passage even from saline mixtures of NaCl and NaF.

Covalent-driven Layer-by-layer Self-assembly of Clindamycin-loaded PPLA Nanoparticles/chitosan Membrane on Titanium Sheet for Longacting Anti-infection

Background: Post-arthroplasty implant-related infection is one of the most feared complications with adverse consequences for patients and public health systems, especially in terms of the huge financial cost of treatment. This is compounded by the potential risks of continuous metamorphosis and emergence of new resistant bacterial strains. Constructing an antibacterial surface, therefore, on the implant represents an approach to reduce the incidence of implant-related infections. Methods: In this study, a covalent-driven layer-by-layer self-assembly of clindamycin-loaded polyethylene glycol grafted polylactic acid nanoparticles/chitosan membrane has been successfully fabricated on the titanium sheet and evaluated for drug releasing potential and antibiotic activity. Results: Attenuated total reflectance spectrum of the layer-by-layer self-assembly membrane showed three absorption peaks around 1680, 1520 and 1240 cm-1, which are the characteristic absorption peaks of secondary amines. The results indicated the formation of an amide bond between the carboxyl groups of clindamycin-loaded polyethylene glycol grafted polylactic acid nanoparticles and the amino groups of chitosan. The covalent bond stabilized the membrane construct. The membrane exhibited a sustained drug release behavior whereby less than 50% of clindamycin was released after 160 hr. The membrane persistently inhibited the growth of Staphylococcus aureus with the inhibition ratio exceeding 60%. Conclusion: The membrane construct holds a great potential for managing anti-implant-related infections.

Interfacial hydration determines orientational and functional dimorphism of sterol-derived Raman tags in lipid-coated nanoparticles

Lipid-coated noble metal nanoparticles (L-NPs) combine the biomimetic surface properties of a self-assembled lipid membrane with the plasmonic properties of a nanoparticle (NP) core. In this work, we investigate derivatives of cholesterol, which can be found in high concentrations in biological membranes, and other terpenoids, as tunable, synthetic platforms to functionalize L-NPs. Side chains of different length and polarity, with a terminal alkyne group as Raman label, are introduced into cholesterol and betulin frameworks. The synthesized tags are shown to coexist in two conformations in the lipid layer of the L-NPs, identified as "head-out" and "head-in" orientations, whose relative ratio is determined by their interactions with the lipid-water hydrogen-bonding network. The orientational dimorphism of the tags introduces orthogonal functionalities into the NP surface for selective targeting and plasmon-enhanced Raman sensing, which is utilized for the identification and Raman imaging of epidermal growth factor receptor-overexpressing cancer cells.

Front Cover: Influence of Wet–Dry Cycling on the Self‐Assembly and Physicochemical Properties of Model Protocellular Membrane Systems (ChemSystemsChem 5/2021)

The Front Cover illustrates the self-assembly of model protocell membranes under prebiotically pertinent wet-dry cycles. Multiple wet-dry cycles were shown to increase membrane encapsulation efficiency, while also altering the membrane composition of the protocells, thereby affecting its properties. This study underscores the potential role of wet-dry cycles as an early Earth environmental selection pressure, which could have had an effect on the molecular evolution of protocell membranes. Cover design by Shraddha Bhurkunde. More information can be found in the Article by Susovan Sarkar, Shikha Dagar, and Sudha Rajamani.

A nanoselenium-coating biomimetic cytomembrane nanoplatform for mitochondrial targeted chemotherapy- and chemodynamic therapy through manganese and doxorubicin codelivery

The cell membrane is widely considered as a promising delivery nanocarrier due to its excellent properties. In this study, self-assembled Pseudomonas geniculate cell membranes were prepared with high yield as drug nanocarriers, and named BMMPs. BMMPs showed excellent biosafety, and could be more efficiently internalized by cancer cells than traditional red cell membrane nanocarriers, indicating that BMMPs could deliver more drug into cancer cells. Subsequently, the BMMPs were coated with nanoselenium (Se), and subsequently loaded with Mn2+ ions and doxorubicin (DOX) to fabricate a functional nanoplatform (BMMP-Mn2+/Se/DOX). Notably, in this nanoplatform, Se nanoparticles activated superoxide dismutase-1 (SOD-1) expression and subsequently up-regulated downstream H2O2 levels. Next, the released Mn2+ ions catalyzed H2O2 to highly toxic hydroxyl radicals (·OH), inducing mitochondrial damage. In addition, the BMMP-Mn2+/Se nanoplatform inhibited glutathione peroxidase 4 (GPX4) expression and further accelerated intracellular reactive oxygen species (ROS) generation. Notably, the BMMP-Mn2+/Se/DOX nanoplatform exhibited increased effectiveness in inducing cancer cell death through mitochondrial and nuclear targeting dual-mode therapeutic pathways and showed negligible toxicity to normal organs. Therefore, this nanoplatform may represent a promising drug delivery system for achieving a safe, effective, and accurate cancer therapeutic plan.

Spatial arrangements of spherical nanoparticles on lipid vesicles.

We report results of a numerical investigation of the modes of adhesion of two spherical nanoparticles (NPs) on lipid vesicles based on molecular dynamics simulations, in conjunction with the weighted histogram analysis method, of an implicit-solvent model of self-assembled membranes. Our investigation shows that the NPs exhibit a sequence of three modes of adhesion. For low adhesive interactions, the adhering NPs are apart from each other. As the adhesive interaction is increased, the NPs dimerize into in-plane dimers. As the adhesive interaction is further increased for relatively large vesicles, the NPs dimerize into tubular dimers. However, for small vesicles, the tubular dimer state is not observed. For higher values of the adhesive interaction, four endocytosis modes are observed, depending on the initial locations of the NPs on the vesicle and the relative size of the NPs with respect to that of the vesicle. For relatively large vesicles, the NPs are endocytosed individually or as a dimer. For relatively small vesicles, only one NP is endocytosed if the initial distance between the NPs is large, while the second NP remains adhered to the outer leaflet of the vesicle. However, if the initial distance between the NPs is small, one NP is endocytosed, while the other is internalized in the vesicle through a pore.