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Enveloped viruses pose a significant threat to human health, as evidenced by the recent COVID-19 pandemic. Although current vaccine strategies have proven effective in preventing viral infections, the development of innovative vaccine technologies is crucial to fortify our defences against future pandemics. In this study, we introduce a novel platform called cell-engineered virus-mimetic nanovesicles (VNVs) and demonstrate their potential as a vaccine for targeting enveloped viruses. VNVs are generated by extruding plasma membrane-derived blebs through nanoscale membrane filters. These VNVs closely resemble enveloped viruses and extracellular vesicles (EVs) in size and morphology, being densely packed with plasma membrane contents and devoid of materials from other membranous organelles. Due to these properties, VNVs express viral membrane antigens more extensively and homogeneously than EVs expressing the same antigen. In this study, we produced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) VNVs expressing the SARS-CoV-2 Spike glycoprotein (S) on their surfaces and assessed their preclinical efficacy as a COVID-19 vaccine in experimental animals. The administration of VNVs successfully stimulated the production of S-specific antibodies both systemically and locally, and immune cells isolated from vaccinated mice displayed cytokine responses to S stimulation.

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To investigate the proliferation cycle of a virus, virus-host interaction, and pathogenesis of a virus, virion particles must be concentrated from the media of virus cell culture or the sera of virus-infected patients. Ultracentrifugation of the culture media is a standard method for concentrating virion particles. However, this method is time-consuming and requires special equipment (ultracentrifuge). Moreover, a large number of infectious viruses are lost during enrichment. We developed a new method of hepatitis C virus (HCV) concentration to overcome the issues associated with traditional methods of virus concentration. We used an aqueous two-phase system (ATPS) to concentrate the virus. HCV, which causes various liver diseases, such as liver fibrosis, cirrhosis, and hepatocellular carcinoma, was used as a model virus to test the efficacy and reliability of the ATPS. The efficiency of HCV concentration by the ATPS was approximately three times higher than that by ultracentrifugation. Moreover, the infectivity of the concentrated HCV, which is a labile virus, remained the same after concentration of the virus by the ATPS. Considering the simplicity and effectiveness of the ATPS, it is the method of choice for concentrating viruses.

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We demonstrate a fluorescence-based nanoparticle tracking analysis (NTA) system for the characterization of both the size and membrane protein expression of individual extracellular vesicles (EVs). A sheet of lasers with four different wavelengths was sequentially shone onto extracellular vesicles according to a preprogrammed schedule, providing scattering images intercalated by three fluorescent images. The presence of extracellular vesicles was tracked frame by frame from scattering images. Fluorescence-labeled membrane proteins on EVs were detected by comparing scattering and fluorescent images. The tetraspanins (CD9, CD63, and CD81) of individual HEK293 EVs analyzed by both NTA and total internal reflection fluorescence microscopy showed that the proposed NTA system can contribute to the understanding of individual extracellular vesicles.

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Extracellular vesicles (EVs) are secreted nano-sized vesicles that contain cellular proteins, lipids, and nucleic acids. Although EVs are expected to be biologically diverse, current analyses cannot adequately characterize this diversity because most are ensemble methods that inevitably average out information from diverse EVs. Here we describe a single vesicle analysis, which directly visualizes marker expressions of individual EVs using a total internal-reflection microscopy and analyzes their co-localization to investigate EV subpopulations. The single-vesicle imaging and co-localization analysis successfully illustrated the diversity of EVs and revealed distinct patterns of tetraspanin expressions. Application of the analysis demonstrated similarities and dissimilarities between the EV fractions that had been acquired from different conventional EV isolation methods. The analysis method developed in this study will provide a new and reliable tool for investigating characteristics of single EVs, and the findings of the analysis might increase understanding of the characteristics of EVs.

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We report a robust and continuous oil/water separation with nanostructured glass microfiber (GMF) membranes modified by oxygen plasma treatment and self-assembled monolayer coating with vertical polymerization. The modified GMF membrane had a nanostructured surface and showed excellent superhydrophobicity. With an appropriate membrane thickness, a high water intrusion pressure (< 62.7 kPa) was achieved for continuous pressure-driven separation of oil/water mixtures with high flux (< 4418 L h-1 m-2) and high oil purity (> 99%). Under simulated industrial conditions, the modified GMF membrane exhibited robust chemical stability against strong acidic/alkaline solutions and corrosive environments. The proposed superhydrophobic composite coating technique is simple, low cost, environmentally friendly, and suitable for the mass production of scalable three-dimensional surfaces. Moreover, its stability and customizable functionality offers considerable potential for a wide range of novel applications.

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Cell-engineered nanovesicles (CNVs) are considered as an alternative to exosomes, because they can be produced efficiently on a large scale and have been successfully reported in several applied research studies. However, CNVs may originate from various organelles, i.e., some of them may cause adverse effects on recipient cells, and their origin has not yet been identified. In this study, we air-sprayed human embryonic kidney 293 (HEK293) cells into lipid-bilayer CNVs. To identify the subcellular origin of the CNVs, we prepared nine different HEK293 cell lines by transfection with organelle-specific fluorescent protein plasmids that target the plasma membrane, peroxisome, lysosome, early endosome, late endosome, nucleus, mitochondrion, Golgi apparatus, and endoplasmic reticulum. The origin of CNVs were identified by measuring fluorescence expressions for organelle-specific markers using fluorescence nanoparticle tracking analysis (NTA). In the results, we found that CNVs derived from the plasma membrane constituted the largest portion, but CNVs derived from the other organelles comprised a non-negligible portion as well. This information will be useful to guide advanced research on outer membrane vesicles and exosome-mimetic nanovesicles engineered from cells.

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We report spatial separation of extracellular vesicle (EVs) populations based on particle size by using an approach that exploits Marangoni flow and the coffee-ring effect in microdroplets. Sequential transfer of a drying droplet progressively increases the mean size of EVs in the sample by repeated subsampling of a droplet during coffee-ring formation. This method allows size-based sorting, separation, and eventual retrieval of EVs for RNA and protein analysis. To demonstrate the biomedical relevance of this method, EVs from prostate cancer patients were analyzed; results revealed that the expression of cancer-associated genes and proteins was higher in small EVs than in large EVs. This ability to sort EVs using a combination of coffee ring with Marangoni flow and sequential droplet-transfer allows analysis of subpopulations of EVs, and will facilitate further studies of EVs.

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