Native Membrane Research Articles

Biomimetic liposomes hybrid with erythrocyte membrane modulate dendritic cells to ameliorate systemic lupus erythematosus.

Dendritic cells (DCs)-based immunotherapy has shown immense promise in systemic lupus erythematosus (SLE) treatment. However, existing carrier strategies such as polymers, liposomes, and polypeptides, are difficult to achieve active targeting to DCs due to their intricate interaction with biological systems. Since DCs represent a class of phagocytes responsible for the removal of senescent or damaged erythrocytes, we hypothesize that hybrid vesicles containing erythrocytes membrane components could be presented to be potent drug carriers to target DCs specifically. Herein, inspired by the cell membrane fusion technique, we develop hybrid biomimetic liposomes (R-Lipo) by fusing natural erythrocyte membrane vesicles and artificial liposomes for DCs-targeted SLE therapy. The resultant R-Lipo exhibited excellent biocompatibility and was shown to be effectively internalized by DCs both in vitro and in vivo. Using an immunosuppressant, mycophenolic acid (MPA), as the model drug, MPA-loaded R-Lipo powerfully suppressed DCs maturation and efficiently controlled the duration of lupus nephritis without apparent side effects. Our findings provide a safe, effective, and easy-to-prepare biomimetic vesicle platform for the treatment of SLE and other DC-associated diseases.

Osmotically Activated Anion Current of Phycomyces Blakesleeanus-Filamentous Fungi Counterpart to Vertebrate Volume Regulated Anion Current.

Studies of ion currents in filamentous fungi are a prerequisite for forming a complete understanding of their physiology. Cytoplasmic droplets (CDs), obtained from sporangiophores of Phycomyces blakesleeanus, are a model system that enables the characterization of ion currents in the native membrane, including the currents mediated by the channels not yet molecularly identified. Osmotically activated anionic current with outward rectification (ORIC) is a dominant current in the membrane of cytoplasmic droplets under the conditions of hypoosmotic stimulation. We have previously reported remarkable functional similarities of ORIC with the vertebrate volume regulated anionic current (VRAC), such as dose-dependent activation by osmotic difference, ion selectivity sequence, and time and voltage dependent profile of the current. Using the patch clamp method on the CD membrane, we further resolve VRAC-like ORIC characteristics in this paper. We examine the inhibition by extracellular ATP and carbenoxolone, the permeation of glutamate in presence of chloride, selectivity for nitrates, and activation by GTP, and we show its single channel behavior in excised membrane. We propose that ORIC is a functional counterpart of vertebrate VRAC in filamentous fungi, possibly with a similar essential role in anion efflux during cell volume regulation.

Encapsulated papillary carcinoma of the breast: does it have a native basement membrane?

Encapsulated papillary carcinoma (EPC) is surrounded by a thick fibrous capsule-like structure, which is interpreted as a thickened basement membrane (BM). This study aimed to describe the geometric characteristics of the EPC capsule and to refine whether it is an expansion of the BM or a stromal reactive process. In all, 100 cases were divided into four groups: EPC, ductal carcinoma in situ (DCIS), normal breast tissue and invasive tumours, with an additional encapsulated papillary thyroid carcinoma (EPTC) control group. Representative slides from each case were stained with picrosirius red (PSR) stain and examined using polarised microscopy. Images were analysed using ImageJ, CT-FIRE, and Curve align image analysis programmes. Compared to the normal and DCIS BM, the EPC group showed a significant increase of collagen fibre width, straightness, and density, and a decrease of fibre length. The EPC capsule showed less alignment of fibres with a more perpendicular arrangement, and it was enriched with disorganised collagen type I (stromal collagen) fibres. Compared to other groups, the EPC capsule showed significant variation in the thickness, evenness, distribution of collagen fibres, and significant intracapsular heterogeneity. Compared to BM-like material in the invasive group, the EPC capsule showed a higher density of collagen fibres with longer, straighter, and more aligned fibres, but there was no difference in the distribution of both collagen types I and III. Conversely, compared to EPTC, there were no differences between both EPC and EPTC capsules except that the fibres in the EPC capsule were straighter. Although differences between normal ducts and lobules and DCIS BM collagen fibre density, straightness, orientation, and alignment were detected, both were significantly different from EPC capsule. This study provided evidence that the EPC capsule is a reactive process rather than a thickened native BM characteristic of normal and in situ lesions, which provides further evidence that EPC is an indolent invasive carcinoma based on capsule characteristics.

Bioinspired Matrix Vesicles Based on Platelet Membrane for Biomineralization of Dentin Tubules

Matrix vesicles (MVs), a kind of extracellular vesicles secreted by cells, play an important role in the initial stage of hard tissue mineralization. Acidic phospholipids and functional membrane proteins which are embedded into the membrane surface of MVs provide mineral nucleation sites and regulate mineral ions for facilitating biomineralization. Here, we report the MVs-mimic nanovesicles prepared from natural platelet membrane fragments. The bioinspired nanovesicles can penetrate into the deep dentinal tubule due to their stable nanostructure, and provide nucleation sites and templates for nascent mineral crystals. Meanwhile, the acidic phospholipids on the nanovesicle surface can recruit mineral ions from the environment to effectively promote biomineralization in situ. On the other hand, proteins on the surface of the nanovesicles can promote collagen cross-linking to inhibit the enzymatic hydrolysis of collagen, and further protect this mineralization template. The newly formed minerals can effectively seal the dentinal tubules, and even the sealing depth can reach 60 μm. This strategy uses “artificial MVs” derived from platelet membranes for the biomineralization of dentin, bringing new prospects for hard tissue repair in clinical practice.

Nanoarchitectonic approaches for measuring the catalytic behavior of a membrane anchored enzyme. From Langmuir-Blodgett to a novel Langmuir-Schaefer based nanofilm building device

Self-organized lipid monolayers at the air-water interface (Langmuir films, LF) are commonly used for measuring the catalytic properties of membrane-bound enzymes. This methodology allows to provide a consistent flat topography molecular density, packing defects and thickness. The aim of the present work was to show the methodological advantages of using the horizontal transfer method (Langmuir-Schaefer) with respect to the vertical transfer method (Langmuir-Blodgett) when mounting a device to measure catalytic activity of membrane enzymes. Based on the results obtained we can conclude that it is possible to prepare stable Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) films from Bovine Erythrocyte Membranes (BEM) preserving the catalytic activity of its native Acetylcholinesterase (BEA). In comparison, the LS films showed Vmax values more similar to the enzyme present in the vesicles of natural membranes. In addition, it was much easier to produce large amounts of transferred areas with the horizontal transfer methodology. It was possible to decrease the time required to mount an assay with numerous activity points, such as building activity curves as a function of substrate concentration. The present results show that LSBEM provides a proof of concept for the development of biosensors based on transferred purified membrane for the screening of new products acting on an enzyme embedded on its natural milieu. In the case of BEA, the application of these enzymatic sensors could have medical interest, providing drug screening tools for the treatment of Alzheimer's disease.

Electromechanical performance of dielectric elastomer composites: Modeling and experimental characterization

Dielectric Elastomer (DE) devices have gained widespread attention in recent years for their ability to generate large, reversible strains in response to electric actuation. However, some DE materials exhibit a viscoelastic nature that detracts from their electromechanical performance in applications requiring precise time-dependent actuation. This study presents an investigation into the feasibility of using multilayered DE composites, comprising commercially available acrylic-based VHB 4905 and natural rubber membranes, to overcome the viscoelastic effects. A comparison of the electromechanical performance of bi-layer and tri-layer DE composites with that of a mono-layer VHB 4910 membrane is carried out through numerical and experimental methods. We present a theoretical model of the DE composite-based bulging actuator, using an energy-based approach and the assumption of homogeneous deformations. The model predicts the time-dependent deflection of the inflated/deflated multilayered DE composites, taking into account the effect of the intervening air column. The predictive capabilities of the model are validated through experiments under both DC and AC operating conditions, and the electromechanical performance of the DE composites is examined for various actuation responses such as resonance, creep, and hysteresis. The bi-layer DE composite is found to be superior in terms of actuation levels, reduced hysteresis, and reduced creep response. The findings of this study hold promise for the development of DE materials with improved actuation capabilities while maintaining dielectric breakdown strength.

Engineered molecular sensors for quantifying cell surface crowding

Cells mediate interactions with the extracellular environment through a crowded assembly of transmembrane proteins, glycoproteins and glycolipids on their plasma membrane. The extent to which surface crowding modulates the biophysical interactions of ligands, receptors, and other macromolecules is poorly understood due to the lack of methods to quantify surface crowding on native cell membranes. In this work, we demonstrate that physical crowding on reconstituted membranes and live cell surfaces attenuates the effective binding affinity of macromolecules such as IgG antibodies in a surface crowding-dependent manner. We combine experiment and simulation to design a crowding sensor based on this principle that provides a quantitative readout of cell surface crowding. Our measurements reveal that surface crowding decreases IgG antibody binding by 2 to 20 fold in live cells compared to a bare membrane surface. Our sensors show that sialic acid, a negatively charged monosaccharide, contributes disproportionately to red blood cell surface crowding via electrostatic repulsion, despite occupying only ~1% of the total cell membrane by mass. We also observe significant differences in surface crowding for different cell types and find that expression of single oncogenes can both increase and decrease crowding, suggesting that surface crowding may be an indicator of both cell type and state. Our high-throughput, single-cell measurement of cell surface crowding may be combined with functional assays to enable further biophysical dissection of the cell surfaceome.

Exploitation of platelets for antitumor drug delivery and modulation of the tumor immune microenvironment

Platelets are blood components traditionally believed to have fundamental roles in vascular hemostasis and thrombosis. In recent years, platelets have received new attention for their roles in tumorigenesis and progression. On the one hand, platelets are actively recruited by various tumors and comprise a crucial part of the tumor microenvironment (TME), thus inspiring the use of platelets for tumor-targeted drug delivery. To this end, various platelet-based devices have been proposed, such as natural platelets, engineered platelets, platelet membranes, and platelet-derived microparticles. On the other hand, platelets are involved in tumor immunosuppression mechanisms, by directing and/or assisting various tumor-associated immune cells. However, in the context of inflammation and autoimmune diseases, platelets can amplify immune responses by promoting immune cell mobilization and activation, thereby exacerbating tissue damage. Thus, interest is growing in the use of tumor-associated platelets as targets for therapeutic modulation of the TME and augmenting anti-tumor immune responses. In this review, we summarize current advances in exploiting platelets for both antitumor drug delivery and immune modulation of the TME.

RO6807936 as a Novel PET Radiotracer for in Vitro and in Vivo Visualization and Quantification of BACE1 in the Rodent and Baboon Brain.

The beta-site amyloid precursor protein cleaving enzyme (BACE1) is responsible for initiating the generation of beta-amyloid, the major constituent of amyloid plaques in Alzheimer's disease (AD). The purpose of this study was to develop a specific BACE1 radioligand for visualization of the distribution pattern and quantification of the BACE1 protein in the rodent and monkey brain both in vitro by autoradiography and in vivo by positron emission tomography (PET). The BACE1 inhibitor RO6807936 originating from an in-house chemical drug optimization program was selected based on its PET tracer like physicochemical properties and a favorable pharmacokinetic profile. Saturation binding analysis of [3 H]RO6807936 revealed specific and high affinity binding (KD = 2.9 nM) and a low Bmax value (4.3 nM) of the BACE1 protein in native rat brain membranes. [3 H]RO6807936 binding showed a ubiquitous distribution on rat brain slices in vitro with higher levels in the CA3 8 cell layer and the granule cell layer of the hippocampus. In a next step, RO6807936 was successfully radiolabelled with carbon-11 and showed acceptable uptake in the baboon brain as well as a widespread and rather homogeneous distribution consistent with rodent data. In vivo blockade studies with a specific BACE1 inhibitor reduced uptake of the tracer to homogenous levels across brain regions and demonstrated specificity of the signal. Our data warrant further profiling of this PET tracer candidate in humans to investigate BACE1 expression in normal individuals and those with AD and as an imaging biomarker for target occupancy studies in clinical drug trials.

Fluidic Spatial-Confinement Scaffold Affords a Multicomponent DNA Reaction with Improved Efficiency and Accelerated Kinetics.

Enzyme-free nucleic acid amplification reactions with the capability of signal catalytic amplification have been widely used in biosensors. However, these multicomponent, multistep nucleic acid amplification systems often suffer from low reaction efficiency and kinetics. Herein, inspired by the natural cell membrane system, we utilized the red blood cell membrane as a fluidic spatial-confinement scaffold to construct a novel accelerated reaction platform. By simply modifying with cholesterol, DNA components can be efficiently integrated into the red blood cell membrane through hydrophobic interactions, which greatly increases the local concentration of DNA strands. Moreover, the fluidity of the erythrocyte membrane improves the collision efficiency of DNA components in the amplification system. Based on the increased local concentration and improved collision efficiency, the fluidic spatial-confinement scaffold significantly improved the reaction efficiency and kinetics. Taking catalytic hairpin assembly (CHA) as a model reaction, an RBC-CHA probe based on the erythrocyte membrane platform enables a more sensitive detection of miR-21 with a sensitivity that is 2 orders of magnitude higher than the free CHA probe and a fast reaction rate (about 3.3-fold). The proposed strategy provides a new idea for the construction of a novel spatial-confinement accelerated DNA reaction platform.

Frontispiece: Synthesis of Erythrocyte Nanodiscs for Bacterial Toxin Neutralization

Drug Delivery. In their Communication (e202301566), Weiwei Gao, Liangfang Zhang et al. report a nanodisc formulation made with natural human red blood cell membrane and demonstrate its robust application for bacterial toxin neutralization.

Frontispiz: Synthesis of Erythrocyte Nanodiscs for Bacterial Toxin Neutralization

Drug Delivery. In their Communication (e202301566), Weiwei Gao, Liangfang Zhang et al. report a nanodisc formulation made with natural human red blood cell membrane and demonstrate its robust application for bacterial toxin neutralization.

Periodontal Guided Tissue Regeneration Membranes: Limitations and Possible Solutions for the Bottleneck Analysis.

Guided tissue regeneration (GTR) is an important surgical method for periodontal regeneration. By placing barrier membrane on the root surface of the tooth to guide the adhesion and proliferation of periodontal ligament cells, periodontal tissue regeneration can be achieved. This review intends to analyze the current limitations of GTR membranes and to propose possible solutions for developing new ones. Limitations of current GTR membranes include nonabsorbable membranes and absorbable synthetic polymer membranes exhibit weak biocompatibility; when applying to a large defect wound, the natural collagen membrane with fast degradation rate have limited mechanical strength, and the barrier function may not be maintained well. Although the degradation time can be prolonged after cross-linking, it may cause foreign body reaction and affect tissue integration; The clinical operation of current barrier membranes is inconvenient. In addition, most of the barrier membranes lack bioactivity and will not actively promote periodontal tissue regeneration. Possible solutions include using electrospinning (ELS) techniques, nanofiber scaffolds, or developing functional gradient membranes to improve their biocompatibility; adding Mg, Zn, and/or other metal alloys, or using 3D printing technology to improve their mechanical strength; increasing the concentration of nanoparticles or using directional arrangement of membrane fibers to control the fiber diameter and porosity of the membrane, which can improve their barrier function; mixing natural and synthetic polymers as well as other biomaterials with different degradation rates in proportion to change the degradation rate and maintain barrier function; to improve the convenience of clinical operation, barrier membranes that meets personalized adhesion to the wound defect can be manufactured; developing local controlled release drug delivery systems to improve their bioactivity. Impact statement This review provides an up-to-date summary of commonly commercial periodontal guided tissue regeneration membranes, and analyze their limitations in clinical use. Using studies published recently to explore possible solutions from several perspectives and to raise possible strategies in the future. Several strategies have tested in vivo/in vitro, which will guide the way to propel clinical translation, meeting clinical needs.

Natural hematite-based self-poled piezo-responsive membrane for harvesting energy from water flow and catalytic removal of organic dye

The energy crisis and environmental pollution have been increasing day by day due to the high consumption of nonrenewable energy which insists researchers discover alternative methods to harvest energy from waste materials and resources. This work reports the construction of the energy harvesting device using a purely natural α-hematite incorporated PVDF membrane. Doping of purely natural α-hematite led to the growth of polarisation forming the β-phase high which has been confirmed by FTIR and other theoretical methods (DFT). The structure morphology has been characterized by using basic characterization tools i.e XRD, SEM, EDAX, and TEM. The augmentation of the polarization has been established by the increased value of the dielectric constant. Herein, we have fabricated the device using PVF5 membrane that can develop voltage 42V, power 1328 μW/cm3 by finger tapping, and the device can also harvest energy even from the water flow from several sources and falling from different heights. Water pollution is another big concern in today's world along with the energy crisis. Piezocatalysis is one of the best-emerging technologies for the treatment of water pollution and this method has been employed in our study by using PVF5 membrane to degrade organic dye i.e RhB dye. 86% degradation of the dye in 40 minutes has been achieved due to the formation of several oxidative spices (ROS) like as •O−, •OH, e−, h+, etc. Using ultrasound-assisted piezocatalysis method, and even after repetitive use of it the efficiency does not reduce significantly. Henceforth this article reports the multifunctional purely natural α-hematite mediated membrane that can concomitantly harvest energy from mechanical as well as decontaminate water by degradation of organic pollutants from water.

In Vivo Stable Allogenic Cartilage Regeneration in a Goat Model Based on Immunoisolation Strategy Using Electrospun Semipermeable Membranes (Adv. Healthcare Mater. 13/2023)

Allogenic Cartilage Regeneration A novel immunoisolation strategy based on a hybrid synthetic–natural electrospun semipermeable membrane is reported in article 2203084 by Yujie Hua, Yixin Zhang, Guangdong Zhou, Xiaoyun Wang, and co-workers. The immunoisolation mechanism is dependent on preventing immune cell attack by the physical barrier and blocking the negative regulatory effect mediated by destructive inflammatory factors, and thus successfully achieving stable allogenic cartilage regeneration in a goat model.

Engineering white blood cell membrane-camouflaged nanocarriers for inflammation-related therapeutics.

White blood cells (WBCs) play essential roles against inflammatory disorders, bacterial infections, and cancers. Inspired by nature, WBC membrane-camouflaged nanocarriers (WBC-NCs) have been developed to mimic the "dynamic" functions of WBCs, such as transendothelial migration, adhesion to injured blood vessels, etc, which make them promising for diverse medical applications. WBC-NCs inherit the cell membrane antigens of WBCs, while still exhibiting the robust inflammation-related therapeutic potential of synthetic nanocarriers with excellent (bio)physicochemical performance. This review summarizes the proposed concept of cell membrane engineering, which utilizes physical engineering, chemical modification, and biological functionalization technologies to endow the natural cell membrane with abundant functionalities. In addition, it highlights the recent progress and applications of WBC-NCs for inflammation targeting, biological neutralization, and immune modulation. Finally, the challenges and opportunities in realizing the full potential of WBC-NCs for the manipulation of inflammation-related therapeutics are discussed.

Erythrocytes Nanoparticle Delivery: A Boon for Targeting Tumor.

Although nanoparticles (NPs) have many advantages as drug delivery systems, their poor stability in circulation, premature drug release, and nonspecific uptake in non-target organs have prompted biomimetic approaches to camouflage nano vehicles using natural cell membranes. Among them, which are extensively studied in erythrocytes, are the most abundant circulating blood cells. They are specially used for biomimetic coating on artificial NPs due to their excellent properties of good biocompatibility, biodegradability, non-immunogenicity, and long-term blood circulation. Erythrocyte-mimicking nanoparticles (EM-NPs) are prepared by combining nanoparticle cores with naturally derived erythrocyte (red blood cell or RBC) membranes. Compared with conventional nanosystems, EM-NPs hold the preferable characteristics of prolonged blood circulation time and immune evasion. In this review, the biomimetic platform of erythrocyte membrane-coated NPs is described in various aspects, with particular focus placed on the coating mechanism, preparation methods, characterization method, and recent advances in the biomedical applications of EM-NPs concerning cancer and targeted delivery.

Bioorthogonal Tethering Enhances Drug Fragment Affinity for G Protein-Coupled Receptors in Live Cells.

G protein-coupled receptors (GPCRs) modulate diverse cellular signaling pathways and are important drug targets. Despite the availability of high-resolution structures, the discovery of allosteric modulators remains challenging due to the dynamic nature of GPCRs in native membranes. We developed a strategy to covalently tether drug fragments adjacent to allosteric sites in GPCRs to enhance their potency and enable fragment-based drug screening in cell-based systems. We employed genetic code expansion to site-specifically introduce noncanonical amino acids with reactive groups in C-C chemokine receptor 5 (CCR5) near an allosteric binding site for the drug maraviroc. We then used molecular dynamics simulations to design heterobifunctional maraviroc analogues consisting of a drug fragment connected by a flexible linker to a reactive moiety capable of undergoing a bioorthogonal coupling reaction. We synthesized a library of these analogues and employed the bioorthogonal inverse electron demand Diels-Alder reaction to couple the analogues to the engineered CCR5 in live cells, which were then assayed using cell-based signaling assays. Tetherable low-affinity maraviroc fragments displayed an increase in potency for CCR5 engineered with reactive unnatural amino acids that were adjacent to the maraviroc binding site. The strategy we describe to tether novel drug fragments to GPCRs should prove useful to probe allosteric or cryptic binding site functionality in fragment-based GPCR-targeted drug discovery.

Mid-IR quantum cascade laser spectroscopy to resolve lipid dynamics during the photocycle of bacteriorhodopsin.

Membranes are crucial for the functionality of membrane proteins in several cellular processes. Time-resolved infrared (IR) spectroscopy enables the investigation of interaction-induced dynamics of the protein and the lipid membrane. The photoreceptor and proton pump bacteriorhodopsin (BR) was reconstituted into liposomes, mimicking the native purple membrane. By utilization of deuterated lipid alkyl chains, corresponding vibrational modes are frequency-shifted into a spectrally silent window that allows us to monitor lipid dynamics during the photoreaction of BR. Our home-built quantum cascade laser (QCL)-based IR spectrometer covers all relevant spectral regions to detect both lipid and protein vibrational modes. QCL-probed transients at single wavenumbers are compared with the previously performed step-scan Fourier-transform IR measurements. The absorbance changes of the lipids could be resolved by QCL-measurements with a much better signal-to-noise ratio and with nanosecond time resolution. We found a correlation of the lipid dynamics with the protonation dynamics in the M intermediate. QCL spectroscopy extends the study of the protein's photocycle toward dynamics of the interacting membrane.

Interdigitated immunoglobulin arrays form the hyperstable surface layer of the extremophilic bacterium Deinococcus radiodurans

Deinococcus radiodurans is an atypical diderm bacterium with a remarkable ability to tolerate various environmental stresses, due in part to its complex cell envelope encapsulated within a hyperstable surface layer (S-layer). Despite decades of research on this cell envelope, atomic structural details of the S-layer have remained obscure. In this study, we report the electron cryomicroscopy structure of the D. radiodurans S-layer, showing how it is formed by the Hexagonally Packed Intermediate-layer (HPI) protein arranged in a planar hexagonal lattice. The HPI protein forms an array of immunoglobulin-like folds within the S-layer, with each monomer extending into the adjacent hexamer, resulting in a highly interconnected, stable, sheet-like arrangement. Using electron cryotomography and subtomogram averaging from focused ion beam-milled D. radiodurans cells, we have obtained a structure of the cellular S-layer, showing how this HPI S-layer coats native membranes on the surface of cells. Our S-layer structure from the diderm bacterium D. radiodurans shows similarities to immunoglobulin-like domain-containing S-layers from monoderm bacteria and archaea, highlighting common features in cell surface organization across different domains of life, with connotations on the evolution of immunoglobulin-based molecular recognition systems in eukaryotes.