Plant Membrane-On-A-Chip: A Platform for Studying Plant Membrane Proteins and Lipids.

The cell plasma membrane is a two-dimensional, fluid mosaic material composed of lipids and proteins that create a semipermeable barrier defining the cell from its environment. Compared with soluble proteins, the methodologies for the structural and functional characterization of membrane proteins are challenging. An emerging tool for studies of membrane proteins in mammalian systems is a "plasma membrane on a chip," also known as a supported lipid bilayer. Here, we create the "plant-membrane-on-a-chip,″ a supported bilayer made from the plant plasma membranes of Arabidopsis thaliana, Nicotiana benthamiana, or Zea mays. Membrane vesicles from protoplasts containing transgenic membrane proteins and their native lipids were incorporated into supported membranes in a defined orientation. Membrane vesicles fuse and orient systematically, where the cytoplasmic side of the membrane proteins faces the chip surface and constituents maintain mobility within the membrane plane. We use plant-membrane-on-a-chip to perform fluorescent imaging to examine protein-protein interactions and determine the protein subunit stoichiometry of FLOTILLINs. We report here that like the mammalian FLOTILLINs, FLOTILLINs expressed in Arabidopsis form a tetrameric complex in the plasma membrane. This plant-membrane-on-a-chip approach opens avenues to studies of membrane properties of plants, transport phenomena, biophysical processes, and protein-protein and protein-lipid interactions in a convenient, cell-free platform.

An Impedance-Based Approach for Sensing Cyclodextrin-Mediated Modulation of Membrane Cholesterol.

Cyclodextrin molecules are increasingly being used in biological research and as therapeutic agents to alter membrane cholesterol content, yet there is much to learn about their interactions with cell membranes. We present a biomembrane-based organic electronic platform capable of detecting interactions of cell membrane constituents with methyl-ß-cyclodextrin (MßCD). This approach enables label-free sensing and quantification of changes in membrane integrity resulting from such interactions. In this work, we employ cholesterol-containing supported lipid bilayers (SLBs) formed on conducting polymer-coated electrodes to investigate how MßCD impacts membrane resistance. By examining the outcomes of MßCD interactions with SLBs of varying cholesterol content, we demonstrate that changes in membrane permeability or resistance can be used as a functional measure for predicting cyclodextrin-mediated cholesterol extraction from cellular membranes. Furthermore, we use the SLB platforms to electronically monitor cholesterol delivery to membranes following exposure to MßCD pre-loaded with cholesterol, observing that cholesterol enrichment is commensurate with an increase in resistance. This biomembrane-based bioelectronic sensing system offers a tool to quantify the modulation of membrane cholesterol content using membrane resistance and provides information regarding MßCD-mediated changes in membrane integrity. Given the importance of membrane integrity for barrier function in cells, such knowledge is essential for our fundamental understanding of MßCD as a membrane cholesterol modulator and therapeutic delivery vehicle.

Targeting NAD metabolism regulates extracellular adenosine levels to improve the cytotoxicity of CD8+ effector T cells in the tumor microenvironment of gastric cancer.

PURPOSE: Nicotinamide adenine dinucleotide (NAD+) is closely related to the pathogenesis of tumors. However, the effect of NAD+ metabolism of gastric cancer (GC) cells on immune cells remains unexplained. We targeted nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme in the NAD+ synthesis salvage pathway, to observe its effect in the immune microenvironment. METHODS: NAMPT of GC cell lines was inhibited by using the small molecule inhibitor (FK866) and short hairpin RNA (shRNA). CCK-8 test and flow cytometry were performed to detect cell viability and apoptosis. Immunofluorescence was used to observe changes in mitochondrial membrane potential (MMP).The transfected GC cells (AGS) and patient-derived organoids (PDOs) were cocultured with activated PBMCs, followed by flow cytometric analysis (FCA) for cytokines and inhibitory marker. The level of NAD and ATP of GC cells (AGS & MKN45) was tested combined with NMN and CD39 inhibitor. RESULTS: Targeting NAD+ by FK866 obviously reduced MMP, which ultimately inhibited proliferation and increased the apoptosis of GC cells. NAMPT silencing reduced intracellular NAD and ATP，further decreased extracellular adenosine. Meawhile, the cytokines of CD8+T cells were significantly increased after cocultured with transfected AGS, and the expression of PD-1 was distinctly decreased. NMN reversed the effect of shNAMPT and enhanced the immunosuppression. Consistent results were obtained by coculturing PBMCs with PDOs. CONCLUSION: Restraining the function of NAMPT resulted in the functional improvement of effector CD8+ T cells by decreasing extracellular adenosine levels and inducing apoptosis of GC cells simultaneously. Therefore, this study demonstrates that NAMPT can be an effective target for gastric cancer immunotherapy.

The Prognostic Effect of Multidisciplinary Team Intervention in Patients with Advanced Gastric Cancer.

BACKGROUND: The effect of multidisciplinary team intervention (MDT) on the prognosis of advanced gastric cancer (GC) is still controversial. This study aims to analyze the effect of MDTs on the overall survival time of advanced gastric cancer patients. METHODS: Patients with advanced GC who underwent surgical treatment between 2007 and 2014 were included in the study. They were divided into two groups; the MDT group received MDT treatment and the non-MDT group received conventional treatment. The Kaplan-Meier method was used to compare the overall survival (OS) of the two groups. The prognostic factors of advanced GC were evaluated by multivariate Cox regression analysis. RESULTS: 394 patients were included in our study. Kaplan-Meier survival analysis showed that the prognosis of advanced GC patients with who underwent MDT intervention was better than those without (3-year OS of 55.6% vs. 46.1%, p = 0.005), Multivariate analysis indicated that MDT intervention could reduce mortality (HR = 0.493, p < 0.001). CONCLUSIONS: MDT intervention is an effective measure that improves the survival of patients with advanced GC.

Functional Infectious Nanoparticle Detector: Finding Viruses by Detecting Their Host Entry Functions Using Organic Bioelectronic Devices.

Emerging viruses will continue to be a threat to human health and wellbeing into the foreseeable future. The COVID-19 pandemic revealed the necessity for rapid viral sensing and inhibitor screening in mitigating viral spread and impact. Here, we present a platform that uses a label-free electronic readout as well as a dual capability of optical (fluorescence) readout to sense the ability of a virus to bind and fuse with a host cell membrane, thereby sensing viral entry. This approach introduces a hitherto unseen level of specificity by distinguishing fusion-competent viruses from fusion-incompetent viruses. The ability to discern between competent and incompetent viruses means that this device could also be used for applications beyond detection, such as screening antiviral compounds for their ability to block virus entry mechanisms. Using optical means, we first demonstrate the ability to recapitulate the entry processes of influenza virus using a biomembrane containing the viral receptor that has been functionalized on a transparent organic bioelectronic device. Next, we detect virus membrane fusion, using the same, label-free devices. Using both reconstituted and native cell membranes as materials to functionalize organic bioelectronic devices, configured as electrodes and transistors, we measure changes in membrane properties when virus fusion is triggered by a pH drop, inducing hemagglutinin to undergo a conformational change that leads to membrane fusion.

Small-Molecule Inhibition of Viral Fusion Glycoproteins.

Viral fusion glycoproteins catalyze membrane fusion during viral entry. Unlike most enzymes, however, they lack a conventional active site in which formation or scission of a specific covalent bond is catalyzed. Instead, they drive the membrane fusion reaction by cojoining highly regulated changes in conformation to membrane deformation. Despite the challenges in applying inhibitor design approaches to these proteins, recent advances in knowledge of the structures and mechanisms of viral fusogens have enabled the development of small-molecule inhibitors of both class I and class II viral fusion proteins. Here, we review well-validated inhibitors, including their discovery, targets, and mechanism(s) of action, while highlighting mechanistic similarities and differences. Together, these examples make a compelling case for small-molecule inhibitors as tools for probing the mechanisms of viral glycoprotein-mediated fusion and for viral glycoproteins as druggable targets.

Using Si/MoS2 Core-Shell Nanopillar Arrays Enhances SERS Signal.

Two-dimensional layered material Molybdenum disulfide (MoS2) exhibits a flat surface without dangling bonds and is expected to be a suitable surface-enhanced Raman scattering (SERS) substrate for the detection of organic molecules. However, further fabrication of nanostructures for enhancement of SERS is necessary because of the low detection efficiency of MoS2. In this paper, period-distribution Si/MoS2 core/shell nanopillar (NP) arrays were fabricated for SERS. The MoS2 thin films were formed on the surface of Si NPs by sulfurizing the MoO3 thin films coated on the Si NP arrays. Scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were performed to characterize Si/MoS2 core-shell nanostructure. In comparison with a bare Si substrate and MoS2 thin film, the use of Si/MoS2 core-shell NP arrays as SERS substrates enhances the intensity of each SERS signal peak for Rhodamine 6G (R6G) molecules, and especially exhibits about 75-fold and 7-fold enhancements in the 1361 cm-1 peak signal, respectively. We suggest that the Si/MoS2 core-shell NP arrays with larger area could absorb more R6G molecules and provide larger interfaces between MoS2 and R6G molecules, leading to higher opportunity of charge transfer process and exciton transitions. Therefore, the Si/MoS2 core/shell NP arrays could effectively enhance SERS signal and serve as excellent SERS substrates in biomedical detection.

Detection of Ganglioside-Specific Toxin Binding with Biomembrane-Based Bioelectronic Sensors.

Gangliosides, glycolipids that are abundant in the plasma membrane outer leaflet, play an integral role in cellular recognition, adhesion, and infection by interacting with different endogenous molecules, viruses, and toxins. Model membrane systems, such as ganglioside-enriched supported lipid bilayers (SLBs), present a useful tool for sensing, characterizing, and quantifying such interactions. In this work, we report the formation of ganglioside GM1-rich SLBs on conducting polymer electrodes using a solvent-assisted lipid bilayer assembly method to investigate changes in membrane electrical properties upon binding of the B subunit of cholera toxin. The sensing capabilities of our platform were investigated by varying both the receptor and the toxin concentrations in the system as well as using a complex sample (milk contaminated with the toxin) and monitoring the changes in the electrical properties of the membrane. Our work highlights the potential of such conducting polymer-supported biomembrane-based platforms for detecting the toxins within a complex environment, studying ganglioside-specific biomolecular interactions with toxins and screening inhibitory molecules to prevent these interactions.

Optical and Electronic Ion Channel Monitoring from Native Human Membranes.

Transmembrane proteins represent a major target for modulating cell activity, both in terms of therapeutics drugs and for pathogen interactions. Work on screening such therapeutics or identifying toxins has been severely limited by the lack of available methods that would give high content information on functionality (ideally multimodal) and that are suitable for high-throughput. Here, we have demonstrated a platform that is capable of multimodal (optical and electronic) screening of ligand gated ion-channel activity in human-derived membranes. The TREK-1 ion-channel was expressed within supported lipid bilayers, formed via vesicle fusion of blebs obtained from the HEK cell line overexpressing TREK-1. The resulting reconstituted native membranes were confirmed via fluorescence recovery after photobleaching to form mobile bilayers on top of films of the polymeric electroactive transducer poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS). PEDOT:PSS electrodes were then used for quantitative electrochemical impedance spectroscopy measurements of ligand-mediated TREK-1 interactions with two compounds, spadin and arachidonic acid, known to suppress and activate TREK-1 channels, respectively. PEDOT:PSS-based organic electrochemical transistors were then used for combined optical and electronic measurements of TREK-1 functionality. The technology demonstrated here is highly promising for future high-throughput screening of transmembrane protein modulators owing to the robust nature of the membrane integrated device and the highly quantitative electrical signals obtained. This is in contrast with live-cell-based electrophysiology assays (e.g., patch clamp) which compare poorly in terms of cost, usability, and compatibility with optical transduction.

Self-Assembly of Mammalian-Cell Membranes on Bioelectronic Devices with Functional Transmembrane Proteins.

Transmembrane proteins (TMPs) regulate processes occurring at the cell surface and are essential gatekeepers of information flow across the membrane. TMPs are difficult to study, given the complex environment of the membrane and its influence on protein conformation, mobility, biomolecule interaction, and activity. For the first time, we create mammalian biomembranes supported on a transparent, electrically conducting polymer surface, which enables dual electrical and optical monitoring of TMP function in its native membrane environment. Mammalian plasma membrane vesicles containing ATP-gated P2X2 ion channels self-assemble on a biocompatible polymer cushion that transduces the changes in ion flux during ATP exposure. This platform maintains the complexity of the native plasma membrane, the fluidity of its constituents, and protein orientation critical to ion channel function. We demonstrate the dual-modality readout using microscopy to characterize protein mobility by single-particle tracking and sensing of ATP gating of P2X2 using electrical impedance spectroscopy. This measurement of TMP activity important for pain sensing, neurological activity, and sensory activity raises new possibilities for drug screening and biosensing applications.

Biomembrane-based organic electronic devices for ligand-receptor binding studies.

We present a simple, rapid method for forming supported lipid bilayers on organic electronic devices composed of conducting polymer electrodes using a solvent-assisted lipid bilayer formation method. These supported bilayers present protein recognition elements that are mobile, critical for multivalent binding interactions. Because these polymers are transparent and conducting, we demonstrate, by optical and electrical detection, the specific interactions of proteins with these biomembrane-based bioelectronic devices. This work paves the way for easy formation of biomembrane mimetics for sensing and detection of binding events in a label-free manner on organic electronic devices of more sophisticated architectures. Graphical abstract.

Supported Membrane Platform to Assess Surface Interactions between Extracellular Vesicles and Stromal Cells.

Extracellular vesicles (EVs) are membrane-encapsulated particles secreted by eukaryotic cells that stimulate cell communication and horizontal cargo exchange. EV interactions with stromal cells can result in molecular changes in the recipient cell and, in some cases, lead to disease progression. However, mechanisms leading to these changes are poorly understood. A few model systems are available for studying the outcomes of surface interactions between EV membranes with stromal cells. Here, we created a hybrid supported bilayer incorporating EVs membrane material, called an extracellular vesicle supported bilayer, EVSB. Using EVSBs, we investigated the surface interactions between breast cancer EVs and adipose-derived stem cells (ADSCs) by culturing ADSCs on EVSBs and analyzing cell adhesion, spreading, viability, vascular endothelial growth factor (VEGF) secretion, and myofibroblast differentiation. Results show that cell viability, adhesion, spreading, and proangiogenic activity were enhanced, conditions that promote oncogenic activity, but cell differentiation was not. This model system could be used to develop therapeutic strategies to limit EV-ADSC interactions and proangiogenic conditions. Finally, this model system is not limited to the study of cancer but can be used to study surface interactions between EVs from any origin and any target cell to investigate EV mechanisms leading to cellular changes in other diseases.

Facile Generation of Biomimetic-Supported Lipid Bilayers on Conducting Polymer Surfaces for Membrane Biosensing.

Membrane biosensors that can rapidly sense pathogen interaction and disrupting agents are needed to identify and screen new drugs to combat antibiotic resistance. Bioelectronic devices have the capability to read out both ionic and electrical signals, but their compatibility with biological membranes is somewhat limited. Supported lipid bilayers (SLBs) have served as useful biomimetics for a myriad of research topics involving biological membranes. However, SLBs are traditionally made on inert, rigid, inorganic surfaces. Here, we demonstrate a versatile and facile method for generating SLBs on a conducting polymer device using a solvent-assisted lipid bilayer (SALB) technique. We use this bioelectronic device to form both mammalian and bacterial membrane mimetics to sense the membrane interactions with a bacterial toxin (α-hemolysin) and an antibiotic compound (polymyxin B), respectively. Our results show that we can form high quality bilayers of both types and sense these particular interactions with them, discriminating between pore formation, in the case of α-hemolysin, and disruption of the bilayer, in the case of polymyxin B. The SALB formation method is compatible with many membrane compositions that will not form via common vesicle fusion methods and works well in microfluidic devices. This, combined with the massive parallelization possible for the fabrication of electronic devices, can lead to miniaturized multiplexed devices for rapid data acquisition necessary to identify antibiotic targets that specifically disrupt bacterial, but not mammalian membranes, or identify bacterial toxins that strongly interact with mammalian membranes.

Low-risk gestational trophoblastic neoplasia outcome after treatment with VMP regimen from 2005 to 2017.

OBJECTIVE: To evaluate the efficacy and toxicity of VMP regimen applied to the patients with low-risk gestational trophoblastic neoplasia (LR-GTN) treated in Anhui provincial hospital. MATERIALS AND METHODS: Between 2005 and 2017, 87 patients with low-risk gestational trophoblastic neoplasia received VMP regimen, consisted of vincristine (VCR), methotrexate (MTX) and platinum (cisplatin, carboplatin or nedaplatin), 68 of whom received VMP as their first-line chemotherapy, and 19 methotrexate-failed patients received VMP regimen as their second-line chemotherapy. The staging and scoring system was based on International Federation of Gynecology and Obstetrics (FIGO 2000) criteria. We describe and analyze their baseline characteristics, remission/resistance/recurrence rates, adverse reactions and prognosis. RESULTS: The first-line VMP protocol can achieve an 83.8% remission rate and it tended to develop resistance when the pretreatment ß-hCG reaches 7503.5 IU/L, and can achieve complete remission with FAV and EMA-CO as the salvage regimen. Among the 19 methotrexate-failed patients, 2 of whom were yet resistant to VMP regimen, followed by several courses of salvage chemotherapy such as FAV and EMP, and achieved 89.5% remission rate in second-line VMP group. Resistance to this regimen was obviously related with higher pre-treatment HCG whether used as primary or salvage treatment. Severe myelosuppression (grade 3 or 4) was shown in 4 (5.9%) of 68 cases, of which none was grade 4. CONCLUSION: For patients diagnosed with LR-GTN VMP regimen was a safe and effective treatment with a high rate of remission.

Biologically Complex Planar Cell Plasma Membranes Supported on Polyelectrolyte Cushions Enhance Transmembrane Protein Mobility and Retain Native Orientation.

Reconstituted supported lipid bilayers (SLB) are widely used as in vitro cell-surface models because they are compatible with a variety of surface-based analytical techniques. However, one of the challenges of using SLBs as a model of the cell surface is the limited complexity in membrane composition, including the incorporation of transmembrane proteins and lipid diversity that may impact the activity of those proteins. Additionally, it is challenging to preserve the transmembrane protein native orientation, function, and mobility in SLBs. Here, we leverage the interaction between cell plasma membrane vesicles and polyelectrolyte brushes to create planar bilayers from cell plasma membrane vesicles that have budded from the cell surface. This approach promotes the direct incorporation of membrane proteins and other species into the planar bilayer without using detergent or reconstitution and preserves membrane constituents. Furthermore, the structure of the polyelectrolyte brush serves as a cushion between the planar bilayer and rigid supporting surface, limiting the interaction of the cytosolic domains of membrane proteins with this surface. Single particle tracking was used to analyze the motion of GPI-linked yellow fluorescent proteins (GPI-YFP) and neon-green fused transmembrane P2X2 receptors (P2X2-neon) and shows that this platform retains over 75% mobility of multipass transmembrane proteins in its native membrane environment. An enzyme accessibility assay confirmed that the protein orientation is preserved and results in the extracellular domain facing toward the bulk phase and the cytosolic side facing the support. Because the platform presented here retains the complexity of the cell plasma membrane and preserves protein orientation and mobility, it is a better representative mimic of native cell surfaces, which may find many applications in biological assays aimed at understanding cell membrane phenomena.

Supported Planar Mammalian Membranes as Models of in Vivo Cell Surface Architectures.

Emerging technologies use cell plasma membrane vesicles or "blebs" as an intermediate to form molecularly complete, planar cell surface mimetics that are compatible with a variety of characterization tools and microscopy methods. This approach enables direct incorporation of membrane proteins into supported lipid bilayers without using detergents and reconstitution and preserves native lipids and membrane species. Such a system can be advantageous as in vitro models of in vivo cell surfaces for study of the roles of membrane proteins as drug targets in drug delivery, host-pathogen interactions, tissue engineering, and many other bioanalytical and sensing applications. However, the impact of methods used to induce cell blebbing (vesiculation) on protein and membrane properties is still unknown. This study focuses on characterization of cell blebs created under various bleb-inducing conditions and the result on protein properties (orientation, mobility, activity, etc.) and lipid scrambling in this platform. The orientation of proteins in the cell blebs and planar bilayers is revealed using a protease cleavage assay. Lipid scrambling in both cell blebs and planar bilayers is indicated through an annexin V binding assay. To quantify protein confinement, immobility, etc., incorporation of GPI-linked yellow fluorescent protein (GPI-YFP) was used in conjunction with single-molecule tracking (SMT) microscopy. Finally, to investigate the impact of the bleb induction method on protein activity and expression level, cell blebs expressing human aminopeptidase N (hAPN) were analyzed by an enzyme activity assay and immunoblotting. This work enriches our understanding of cell plasma membrane bleb bilayers as a biomimetic platform, reveals conditions under which specific properties are met, and represents one of the few ways to make molecularly complete supported bilayers directly from cell plasma membranes.

Breast cancer-derived extracellular vesicles stimulate myofibroblast differentiation and pro-angiogenic behavior of adipose stem cells.

Adipose-derived stem cells (ASCs) are abundantly present in the mammary microenvironment and can promote breast cancer malignancy by differentiating into myofibroblasts. However, it remains largely unclear which role tumor-derived extracellular vesicles (TEVs) play in this process. Here, we used microfabricated, type I collagen-based 3-D tissue culture platforms to investigate the effect of breast cancer cell-derived TEVs on ASCs myofibroblast differentiation and consequential changes in extracellular matrix remodeling and vascular sprouting. TEVs collected from MDA MB-231 human metastatic breast cancer cells (MDAs) promoted ASC myofibroblast differentiation in both 2-D and 3-D cultures as indicated by increased alpha smooth muscle actin (α-SMA) and fibronectin (Fn) levels. Correspondingly, TEV-treated ASCs were more contractile, secreted more vascular endothelial growth factor (VEGF), and promoted angiogenic sprouting of human umbilical vein endothelial cells (HUVECs). These changes were dependent on transforming growth factor beta (TGF-ß)-related signaling and tumor cell glutaminase activity as their inhibition decreased TEV-related myofibroblastic differentiation of ASCs and related functional consequences. In summary, our data suggest that TEVs are important signaling factors that contribute to ASC desmoplastic reprogramming in the tumor microenvironment, and suggest that tumor cell glutamine metabolism may be used as a therapeutic target to interfere with this process.