Optimizing Size Exclusion Chromatography for Extracellular Vesicle Enrichment and Proteomic Analysis from Clinically Relevant Samples

Defining the relationship between cellular and extracellular vesicle (EV) content in breast cancer via an integrative multi-omic analysis

Much recent research has been dedicated to exploring the utility of extracellular vesicles (EVs) as circulating disease biomarkers. Underpinning this work is the assumption that the molecular cargo of EVs directly reflects the originating cell. Few attempts have been made, however, to empirically validate this on the -omic level. To this end, we have performed an integrative multi-omic analysis of a panel of breast cancer cell lines and corresponding EVs. Whole transcriptome analysis validated that the cellular transcriptome remained stable when cultured cells are transitioned to low serum or serum-free medium for EV collection. Transcriptomic profiling of the isolated EVs indicated a positive correlation between transcript levels in cells and EVs, including disease-associated transcripts. Analysis of the EV proteome verified that HER2 protein is present in EVs, however neither the estrogen (ER) nor progesterone (PR) receptor proteins are detected regardless of cellular expression. Using multivariate analysis, we derived an EV protein signature to infer cellular patterns of ER and HER2 expression, though the ER protein could not be directly detected. Integrative analyses affirmed that the EV proteome and transcriptome captured key phenotypic hallmarks of the originating cells, supporting the potential of EVs for non-invasive monitoring of breast cancers.

The Landscape of Exosomes Biogenesis to Clinical Applications

Exosomes are extracellular vesicles that originate from various cells and mediate intercellular communication, altering the behavior or fate of recipient cells. They carry diverse macromolecules, such as lipids, proteins, carbohydrates, and nucleic acids. Environmental stressors can change the exosomal contents of many cells, making them useful for diagnosing many chronic disorders, especially neurodegenerative, cardiovascular, cancerous, and diabetic diseases. Moreover, exosomes can be engineered as therapeutic agents to modulate disease processes. State-of-art techniques are employed to separate exosomes including ultracentrifugation, size-exclusion chromatography and immunoaffinity. However, modern technologies such as aqueous two-phase system as well as microfluidics are gaining attention in the recent years. The article highlighted the composition, biogenesis, and implications of exosomes, as well as the standard and novel methods for isolating them and applying them as biomarkers and therapeutic cargo carriers.

Exploitation of elasto-inertial fluid flow for the separation of nano-sized particles: Simulating the isolation of extracellular vesicles

High throughput and efficient separation/isolation of nanoparticles such as exosomes remain a challenge owing to their small size. Elasto-inertial approaches have a new potential to be leveraged because of the ability to achieve fine control over the forces that act on extremely small particles. That is, the viscoelasticity of fluid that helps carry biological particles such as extracellular vesicles (EVs) and cells through microfluidic channels can be tailored to optimize how different-sized particles move within the chip. In this contribution, we demonstrate through computational fluid dynamics (CFD) simulations the ability to separate nanoparticles with a size comparable to exosomes from larger spheres with physical properties comparable to cells and larger EVs. Our current design makes use of an efficient flow-focusing geometry at the inlet of the device in which two side channels deliver the sample, while the inner channel injects the sheath flow. Such flow configuration results in an efficient focusing of all the particles near the sidewalls of the channel at the inlet. By dissolving a minute amount of polymer in the sample and sheath fluid, the elastic lift force arises and the initially focused particle adjacent to the wall will gradually migrate toward the center of the channel. This results in larger particles experiencing larger elastic forces, thereby migrating faster toward the center of the channel. By adjusting the size and location of the outlets, nanoparticles comparable to the size of exosomes (30-100 nm) will be effectively separated from other particles. Furthermore, the influence of different parameters such as channel geometry, flow rate, and fluid rheology on the separation process is evaluated by computational analysis.

Comparative study of size exclusion chromatography for isolation of small extracellular vesicle from cell-conditioned media, plasma, urine, and saliva

Introduction: Extracellular vesicles (EVs) are secreted from all types of cells and are involved in the trafficking of proteins, metabolites, and genetic material from cell to cell. According to their biogenesis and physical properties, EVs are often classified as small EVs (including exosomes) or large EVs, and large oncosomes. A variety of methods are used for isolated EVs; however, they have several limitations, including vesicle deformation, reduced particle yield, and co-isolate protein contaminants. Here we present an optimized fast and low-cost methodology to isolate small EVs (30–150 nm) from biological fluids comparing two SEC stationary phases, G200/120 and G200/140 columns.

Methods: The optimization parameters considered were a) the selection of the stationary phase, b) the eluate volume per fraction, and c) the selection of the enriched 30–150 nm EVs-fractions. The efficiency and separation profile of each UF/SEC fraction was evaluated by Nanoparticle tracking analysis (NTA), flow cytometry, total protein quantification, and Western blot.

Results: Both columns can isolate predominantly small EVs with low protein contaminants from plasma, urine, saliva, and HEK293-derived EV from collection medium. Column G200/ 40 offers a more homogeneous enrichment of vesicles between 30 and 150 nm than G200/120 [76.1 ± 4.4% with an average size of 85.9 ± 3.6 nm (Mode: 72.8 nm)] in the EV collection medium. The enrichment, estimated as the vesicle-to-protein ratio, was 1.3 × 1010 particles/mg protein for G200/40, obtaining a more significant EVs enrichment compared to G200/120. The optimized method delivers 0.8 ml of an EVs-enriched-outcome, taking only 30 min per sample. Using plasma, the enrichment of small EVs from the optimized method was 70.5 ± 0.18%, with an average size of 119.4 ± 6.9 nm (Mode: 120.3 nm), and the enrichment of the vesicle isolation was 4.8 × 1011 particles/mg protein. The average size of urine and saliva -EVs samples was 147.5 ± 3.4 and 111.9 ± 2.5 nm, respectively. All the small EVs isolated from the samples exhibit the characteristic cup-shaped morphology observed by Transmission electron microscopy (TEM).

Discussion: This study suggests that the combination of methods is a robust, fast, and improved strategy for isolating small EVs.

Biochemistry of exosomes and their theranostic potential in human diseases

Exosomes are classified as special extracellular vesicles in the eukaryotic system having diameters ranging from 30 to 120 nm. These vesicles carry various endogenous molecules including DNA, mRNA, microRNA, circular RNA, and proteins, crucial for numerous metabolic reactions and can be proposed as therapeutic or diagnostic targets for several disorders. The donor exosomes release their content to recipient cells and further establish the significant intercellular communication showing biological effects by triggering environmental alterations. Exosomes derived from mesenchymal and dendritic cells have demonstrated their therapeutic potential against organ injury. Yet, various intricacies are involved in exosomal transport and its inclusion in cancer and other disease pathogenesis needs to be explored. The exosomes represent profound potential as diagnostic biomarkers and therapeutic carriers in various pathophysiological conditions such as neurodegenerative diseases, chronic cancers, infectious diseases, female reproductive diseases and cardiovascular diseases. In the current study, we demonstrate the advancements in the implication of exosomes as one of the irrefutable prognostic biological targets in human health and diseases.

The Proteome of Large or Small Extracellular Vesicles in Pig Seminal Plasma Differs, Defining Sources and Biological Functions

Seminal plasma contains many morphologically heterogeneous extracellular vesicles (sEVs). These are sequentially released by cells of the testis, epididymis, and accessory sex glands and involved in male and female reproductive processes. This study aimed to define in depth sEV subsets isolated by ultrafiltration and size exclusion chromatography, decode their proteomic profiles using liquid chromatography-tandem mass spectrometry, and quantify identified proteins using sequential window acquisition of all theoretical mass spectra. The sEV subsets were defined as large (L-EVs) or small (S-EVs) by their protein concentration, morphology, size distribution, and EV-specific protein markers and purity. Liquid chromatography-tandem mass spectrometry identified a total of 1034 proteins, 737 of them quantified by SWATH in S-EVs, L-EVs, and non-EVs-enriched samples (18-20 size exclusion chromatography-eluted fractions). The differential expression analysis revealed 197 differentially abundant proteins between both EV subsets, S-EVs and L-EVs, and 37 and 199 between S-EVs and L-EVs versus non-EVs-enriched samples, respectively. The gene ontology enrichment analysis of differentially abundant proteins suggested, based on the type of protein detected, that S-EVs could be mainly released through an apocrine blebbing pathway and be involved in modulating the immune environment of the female reproductive tract as well as during sperm-oocyte interaction. In contrast, L-EVs could be released by fusion of multivesicular bodies with the plasma membrane becoming involved in sperm physiological processes, such as capacitation and avoidance of oxidative stress. In conclusion, this study provides a procedure capable of isolating subsets of EVs from pig seminal plasma with a high degree of purity and shows differences in the proteomic profile between EV subsets, indicating different sources and biological functions for the sEVs.

Extracellular Vesicles: New Players in the Mechanisms of Sepsis- and COVID-19-Related Thromboinflammation

Sepsis and COVID-19 patients often manifest an imbalance in inflammation and coagulation, a complex pathological mechanism also named thromboinflammation, which strongly affects patient prognosis. Extracellular vesicles (EVs) are nanoparticles released by cells into extracellular space that have a relevant role in cell-to-cell communication. Recently, EVs have been shown to act as important players in a variety of pathologies, including cancer and cardiovascular disease. The biological properties of EVs in the mechanisms of thromboinflammation during sepsis and COVID-19 are still only partially known. Herein, we summarize the current experimental evidence on the role of EVs in thromboinflammation, both in bacterial sepsis and in COVID-19. A better understanding of EV involvement in these processes could be useful in describing novel diagnostic and therapeutic applications of EVs in these diseases.

Exosomes-Based Nanomedicine for Neurodegenerative Diseases: Current Insights and Future Challenges

Neurodegenerative diseases constitute a group of pathologies whose etiology remains unknown in many cases, and there are no treatments that stop the progression of such diseases. Moreover, the existence of the blood-brain barrier is an impediment to the penetration of exogenous molecules, including those found in many drugs. Exosomes are extracellular vesicles secreted by a wide variety of cells, and their primary functions include intercellular communication, immune responses, human reproduction, and synaptic plasticity. Due to their natural origin and molecular similarities with most cell types, exosomes have emerged as promising therapeutic tools for numerous diseases. Specifically, neurodegenerative diseases have shown to be a potential target for this nanomedicine strategy due to the difficult access to the brain and the strategy's pathophysiological complexity. In this regard, this review explores the most important biological-origin drug delivery systems, innovative isolation methods of exosomes, their physicochemical characterization, drug loading, cutting-edge functionalization strategies to target them within the brain, the latest research studies in neurodegenerative diseases, and the future challenges of exosomes as nanomedicine-based therapeutic tools.

A survey to evaluate parameters governing the selection and application of extracellular vesicle isolation methods

Extracellular vesicles (EVs) continue to gain interest across the scientific community for diagnostic and therapeutic applications. As EV applications diversify, it is essential that researchers are aware of challenges, in particular the compatibility of EV isolation methods with downstream applications and their clinical translation. We report outcomes of the first cross-comparison study looking to determine parameters (EV source, starting volume, operator experience, application and implementation parameters such as cost and scalability) governing the selection of popular EV isolation methods across disciplines. Our findings highlighted an increased clinical focus, with 36% of respondents applying EVs in therapeutics and diagnostics. Data indicated preferential selection of ultracentrifugation for therapeutic applications, precipitation reagents in clinical settings and size exclusion chromatography for diagnostic applications utilising biofluids. Method selection was influenced by operator experience, with increased method diversity when EV research was not the respondents primary focus. Application and implementation criteria were indicated to be major influencers in method selection, with UC and SEC chosen for their abilities to process large and small volumes, respectively. Overall, we identified parameters influencing method selection across the breadth of EV science, providing a valuable overview of practical considerations for the effective translation of research outcomes.

Extracellular vesicles in Alzheimer’s disease: from pathology to therapeutic approaches

Alzheimer’s disease is a progressive and fatal neurodegenerative disorder that starts many years before the onset of cognitive symptoms. Identifying novel biomarkers for Alzheimer’s disease has the potential for patient risk stratification, early diagnosis, and disease monitoring in response to therapy. A novel class of biomarkers is extracellular vesicles given their sensitivity and specificity to specific diseases. In addition, extracellular vesicles can be used as novel biological therapeutics given their ability to efficiently and functionally deliver therapeutic cargo. This is critical given the huge unmet need for novel treatment strategies for Alzheimer’s disease. This review summarizes and discusses the most recent findings in this field.

Nickel-Doped Microfluidic Chip for Rapid and Efficient Immunomagnetic Separation and Detection of Breast Cancer Cell-Derived Exosomes

Breast cancer cell-derived exosomes have high potential as biomarkers for continuous biopsies and longitudinal monitoring in breast cancer. However, it is extremely difficult to separate exosomes with high recovery and high purity from complex media, such as urine, plasma, saliva and cell culture supernatants. Here, we designed a flexible and simple microfluidic chip for exosome separation. The capture zone of the chip is a three-dimensional structure of interlaced cylinders doped with nickel powder. Exosomes were separated from cell culture supernatant by the immunomagnetic separation method in continuous flow mode and were detected by fluorescence imaging with high sensitivity. The chip achieved a high exosome recovery rate (> 74%) and purity (> 67%) at an injection rate of 3.6 mL/h. Thus, this chip was demonstrated to be a cutting-edge platform for the separation and detection of exosomes. It could also be applied to separate and detect other types of exosomes, microbubbles and cells.

Characterisation of Extracellular Vesicles from Equine Mesenchymal Stem Cells

Extracellular vesicles (EVs) are nanosized lipid bilayer-encapsulated particles secreted by virtually all cell types. EVs play an essential role in cellular crosstalk in health and disease. The cellular origin of EVs determines their composition and potential therapeutic effect. Mesenchymal stem/stromal cell (MSC)-derived EVs have shown a comparable therapeutic potential to their donor cells, making them a promising tool for regenerative medicine. The therapeutic application of EVs circumvents some safety concerns associated with the transplantation of viable, replicating cells and facilitates the quality-controlled production as a ready-to-go, off-the-shelf biological therapy. Recently, the International Society for Extracellular Vesicles (ISEV) suggested a set of minimal biochemical, biophysical and functional standards to define extracellular vesicles and their functions to improve standardisation in EV research. However, nonstandardised EV isolation methods and the limited availability of cross-reacting markers for most animal species restrict the application of these standards in the veterinary field and, therefore, the species comparability and standardisation of animal experiments. In this study, EVs were isolated from equine bone-marrow-derived MSCs using two different isolation methods, stepwise ultracentrifugation and size exclusion chromatography, and minimal experimental requirements for equine EVs were established and validated. Equine EVs were characterised using a nanotracking analysis, fluorescence-triggered flow cytometry, Western blot and transelectron microscopy. Based on the ISEV standards, minimal criteria for defining equine EVs are suggested as a baseline to allow the comparison of EV preparations obtained by different laboratories.

PLB-985 Neutrophil-Like Cells as a Model To Study Aspergillus fumigatus Pathogenesis

Fungal infections remain a major global concern. Emerging fungal pathogens and increasing rates of resistance mean that additional research efforts and resources must be allocated to advancing our understanding of fungal pathogenesis and developing new therapeutic interventions. Neutrophilic granulocytes are a major cell type involved in protection against the important fungal pathogen Aspergillus fumigatus, where they employ numerous defense mechanisms, including production of antimicrobial extracellular vesicles. A major drawback to work with neutrophils is the lack of a suitable cell line system for the study of fungal pathogenesis. To address this problem, we assessed the feasibility of using differentiated PLB-985 neutrophil-like cells as an in vitro model to study A. fumigatus infection. We find that dimethylformamide-differentiated PLB-985 cells provide a useful recapitulation of many aspects of A. fumigatus interactions with primary human polymorphonuclear leukocytes. We show that differentiated PLB-985 cells phagocytose fungal conidia and acidify conidia-containing phagolysosomes similar to primary neutrophils, release neutrophil extracellular traps, and also produce antifungal extracellular vesicles in response to infection. In addition, we provide an improved method for the isolation of extracellular vesicles produced during infection by employing a size exclusion chromatography-based approach. Advanced liquid chromatography-tandem mass spectrometry (LC-MS/MS) proteomics revealed an enrichment of extracellular vesicle marker proteins and a decrease of cytoplasmic proteins in extracellular vesicles isolated using this improved method. Ultimately, we find that differentiated PLB-985 cells can serve as a genetically tractable model to study many aspects of A. fumigatus pathogenesis. IMPORTANCE Polymorphonuclear leukocytes are an important defense against human fungal pathogens, yet our model systems to study this group of cells remain very limited in scope. In this study, we established that differentiated PLB-985 cells can serve as a model to recapitulate several important aspects of human polymorphonuclear leukocyte interactions with the important human fungal pathogen Aspergillus fumigatus. The proposed addition of a cultured neutrophil-like cell line to the experimental toolbox to study fungal pathogenesis will allow for a more mechanistic description of neutrophil antifungal biology. In addition, the easier handling of the cell line compared to primary human neutrophils allowed us to use PLB-985 cells to provide an improved method for isolation of neutrophil-derived extracellular vesicles using size exclusion chromatography. Together, these results provide significant tools and a baseline knowledge for the future study of neutrophil-derived extracellular vesicles in the laboratory.

Quantitative proteomic analysis of serum-purified exosomes identifies putative pre-eclampsia-associated biomarkers

BACKGROUND

The high incidence of pre-eclampsia, which affects 2-7% of all pregnancies, remains a major health concern. Detection of pre-eclampsia before the appearance of clinical symptoms is essential to allow early intervention, and would benefit from identification of plasma/serum biomarkers to help guide diagnosis and treatment. Liquid biopsy has emerged as a promising source of protein biomarkers that circumvents some of the inherent challenges of proteome-wide analysis of plasma/serum. In this respect, purified exosomes have the added benefit of being carriers of intercellular communication both in physiological and pathological conditions.

METHODS

We compared the protein complement of purified exosomes from three different collections of control and pre-eclamptic serum samples, obtained at the end of the second trimester of pregnancy and at delivery. We employed shotgun label-free proteomics to investigate differential protein expression, which was then validated by targeted proteomics.

RESULTS

We developed a purification method that yielded highly enriched exosome preparations. The presence of specific pregnancy protein markers suggested that a significant proportion of purified exosomes derived from tissues related to pregnancy. Quantitative proteomic analyses allowed us to identify 10, 114 and 98 differentially-regulated proteins in the three sample collections, with a high degree of concordance. Functional analysis suggested that these proteins participate in biological processes related to pre-eclampsia, including angiogenesis, inflammation and cell migration. The differential abundance of 66 proteins was validated by targeted proteomics. Finally, we studied the impact of the pre-eclampsia-associated exosomes in the proteome using an in vitro cellular model.

CONCLUSIONS

We have identified and validated differential exosomal proteins in liquid biopsy of pregnant women that open new possibilities for early detection of pre-eclampsia. Additionally, the functional impact of the proteome composition of purified pre-eclamptic exosomes in target cells provides new information to better understand changes in embryo-maternal interactions and, consequently, the pathogenesis of this disease.

Microfluidic Size Exclusion Chromatography (μSEC) for Extracellular Vesicles and Plasma Protein Separation

Extracellular vesicles (EVs) are recognized as next generation diagnostic biomarkers due to their disease-specific biomolecular cargoes and importance in cell-cell communications. A major bottleneck in EV sample preparation is the inefficient and laborious isolation of nanoscale EVs (≈50-200 nm) from endogenous proteins in biological samples. Herein, a unique microfluidic platform is reported for EV-protein fractionation based on the principle of size exclusion chromatography (SEC). Using a novel rapid (≈20 min) replica molding technique, a fritless microfluidic SEC device (μSEC) is fabricated using thiol-ene polymer (UV glue NOA81, Young's modulus ≈1 GPa) for high pressure (up to 6 bar) sample processing. Controlled on-chip nanoliter sample plug injection (600 nL) using a modified T-junction injector is first demonstrated with rapid flow switching response time (<1.5 s). Device performance is validated using fluorescent nanoparticles (50 nm), albumin, and breast cancer cells (MCF-7)-derived EVs. As a proof-of-concept for clinical applications, EVs are directly isolated from undiluted human platelet-poor plasma using μSEC and show distinct elution profiles between EVs and proteins based on nanoparticle particle analysis (NTA), Western blot and flow cytometry analysis. Overall, the optically transparent μSEC can be readily automated and integrated with EV detection assays for EVs manufacturing and clinical diagnostics.

Nanomaterials-Based Urinary Extracellular Vesicles Isolation and Detection for Non-invasive Auxiliary Diagnosis of Prostate Cancer

Extracellular vesicles (EVs) are natural nanoparticles secreted by cells in the body and released into the extracellular environment. They are associated with various physiological or pathological processes, and considered as carriers in intercellular information transmission, so that EVs can be used as an important marker of liquid biopsy for disease diagnosis and prognosis. EVs are widely present in various body fluids, among which, urine is easy to obtain in large amount through non-invasive methods and has a small dynamic range of proteins, so it is a good object for studying EVs. However, most of the current isolation and detection of EVs still use traditional methods, which are of low purity, time consuming, and poor efficiency; therefore, more efficient and highly selective techniques are urgently needed. Recently, inspired by the nanoscale of EVs, platforms based on nanomaterials have been innovatively explored for isolation and detection of EVs from body fluids. These newly developed nanotechnologies, with higher selectivity and sensitivity, greatly improve the precision of isolation target EVs from urine. This review focuses on the nanomaterials used in isolation and detection of urinary EVs, discusses the advantages and disadvantages between traditional methods and nanomaterials-based platforms, and presents urinary EV-derived biomarkers for prostate cancer (PCa) diagnosis. We aim to provide a reference for researchers who want to carry out studies about nanomaterial-based platforms to identify urinary EVs, and we hope to summarize the biomarkers in downstream analysis of urinary EVs for auxiliary diagnosis of PCa disease in detail.

Tumor-Derived Extracellular Vesicles Regulate Cancer Progression in the Tumor Microenvironment

Extracellular vesicles (EVs) are nanosized particles released by numerous kinds of cells, which are now increasingly considered as essential vehicles of cell-to-cell communication and biomarkers in disease diagnosis and treatment. They contain a variety of biomolecular components, including lipids, proteins and nucleic acids. These functional molecules can be transmitted between tumor cells and other stromal cells such as endothelial cells, fibroblasts and immune cells utilizing EVs. As a result, tumor-derived EVs can deliver molecules to remodel the tumor microenvironment, thereby influencing cancer progression. On the one hand, tumor-derived EVs reprogram functions of endothelial cells, promote cancer-associated fibroblasts transformation, induce resistance to therapy and inhibit the immune response to form a pro-tumorigenic environment. On the other hand, tumor-derived EVs stimulate the immune response to create an anti-tumoral environment. This article focuses on presenting a comprehensive and critical overview of the potential role of tumor-derived EVs-mediated communication in the tumor microenvironment.

Targeted Delivery of Exosomes Armed with Anti-Cancer Therapeutics

Among extracellular vesicles, exosomes have gained great attention for their role as therapeutic vehicles for delivering various active pharmaceutical ingredients (APIs). Exosomes “armed” with anti-cancer therapeutics possess great potential for an efficient intracellular delivery of anti-cancer APIs and enhanced targetability to tumor cells. Various technologies are being developed to efficiently incorporate anti-cancer APIs such as genetic materials (miRNA, siRNA, mRNA), chemotherapeutics, and proteins into exosomes and to induce targeted delivery to tumor burden by exosomal surface modification. Exosomes can incorporate the desired therapeutic molecules via direct exogenous methods (e.g., electroporation and sonication) or indirect methods by modifying cells to produce “armed” exosomes. The targeted delivery of “armed” exosomes to tumor burden could be accomplished either by “passive” targeting using the natural tropism of exosomes or by “active” targeting via the surface engineering of exosomal membranes. Although anti-cancer exosome therapeutics demonstrated promising results in preclinical studies, success in clinical trials requires thorough validation in terms of chemistry, manufacturing, and control techniques. While exosomes possess multiple advantages over synthetic nanoparticles, challenges remain in increasing the loading efficiency of anti-cancer agents into exosomes, as well as establishing quantitative and qualitative analytical methods for monitoring the delivery of in vivo administered exosomes and exosome-incorporated anti-cancer agents to the tumor parenchyma.

Recent Advances in Device Engineering and Computational Analysis for Characterization of Cell-Released Cancer Biomarkers

During cancer progression, tumors shed different biomarkers into the bloodstream, including circulating tumor cells (CTCs), extracellular vesicles (EVs), circulating cell-free DNA (cfDNA), and circulating tumor DNA (ctDNA). The analysis of these biomarkers in the blood, known as 'liquid biopsy' (LB), is a promising approach for early cancer detection and treatment monitoring, and more recently, as a means for cancer therapy. Previous reviews have discussed the role of CTCs and ctDNA in cancer progression; however, ctDNA and EVs are rapidly evolving with technological advancements and computational analysis and are the subject of enormous recent studies in cancer biomarkers. In this review, first, we introduce these cell-released cancer biomarkers and briefly discuss their clinical significance in cancer diagnosis and treatment monitoring. Second, we present conventional and novel approaches for the isolation, profiling, and characterization of these markers. We then investigate the mathematical and in silico models that are developed to investigate the function of ctDNA and EVs in cancer progression. We convey our views on what is needed to pave the way to translate the emerging technologies and models into the clinic and make the case that optimized next-generation techniques and models are needed to precisely evaluate the clinical relevance of these LB markers.

Extracellular vesicles and their role in peripheral nerve regeneration

Peripheral nerve injuries often result in sensory and motor dysfunction in respective parts of the body. Regeneration after peripheral nerve injuries is a complex process including the differentiation of Schwann cells, recruiting of macrophages, blood vessel growth and axonal regrowth. Extracellular vesicles (EVs) are considered to play a pivotal role in intercellular communication and transfer of biological information. Specifically, their bioactivity and ability to deliver cargos of various types of nucleic acids and proteins have made them a potential vehicle for neurotherapeutics. However, production, characterization, dosage and targeted delivery of EVs still pose challenges for the clinical translation of EV therapeutics. This review summarizes the current knowledge of EVs in the context of the healthy and injured peripheral nerve and addresses novel concepts for modification of EVs as therapeutic agents for peripheral nerve regeneration.

Technological Approaches in the Analysis of Extracellular Vesicle Nucleotide Sequences

Together with metabolites, proteins, and lipid components, the EV cargo consists of DNA and RNA nucleotide sequence species, which are part of the intracellular communication network regulating specific cellular processes and provoking distinct target cell responses. The extracellular vesicle (EV) nucleotide sequence cargo molecules are often investigated in association with a particular pathology and may provide an insight into the physiological and pathological processes in hard-to-access organs and tissues. The diversity and biological function of EV nucleotide sequences are distinct regarding EV subgroups and differ in tissue- and cell-released EVs. EV DNA is present mainly in apoptotic bodies, while there are different species of EV RNAs in all subgroups of EVs. A limited sample volume of unique human liquid biopsy provides a small amount of EVs with limited isolated DNA and RNA, which can be a challenging factor for EV nucleotide sequence analysis, while the additional difficulty is technical variability of molecular nucleotide detection. Every EV study is challenged with its first step of the EV isolation procedure, which determines the EV's purity, yield, and diameter range and has an impact on the EV's downstream analysis with a significant impact on the final result. The gold standard EV isolation procedure with ultracentrifugation provides a low output and not highly pure isolated EVs, while modern techniques increase EV's yield and purity. Different EV DNA and RNA detection techniques include the PCR procedure for nucleotide sequence replication of the molecules of interest, which can undergo a small-input EV DNA or RNA material. The nucleotide sequence detection approaches with their advantages and disadvantages should be considered to appropriately address the study problem and to extract specific EV nucleotide sequence information with the detection using qPCR or next-generation sequencing. Advanced next-generation sequencing techniques allow the detection of total EV genomic or transcriptomic data even at the single-molecule resolution and thus, offering a sensitive and accurate EV DNA or RNA biomarker detection. Additionally, with the processes where the EV genomic or transcriptomic data profiles are compared to identify characteristic EV differences in specific conditions, novel biomarkers could be discovered. Therefore, a suitable differential expression analysis is crucial to define the EV DNA or RNA differences between conditions under investigation. Further bioinformatics analysis can predict molecular cell targets and identify targeted and affected cellular pathways. The prediction target tools with functional studies are essential to help specify the role of the investigated EV-targeted nucleotide sequences in health and disease and support further development of EV-related therapeutics. This review will discuss the biological diversity of human liquid biopsy-obtained EV nucleotide sequences DNA and RNA species reported as potential biomarkers in health and disease and methodological principles of their detection, from human liquid biopsy EV isolation, EV nucleotide sequence extraction, techniques for their detection, and their cell target prediction.

ExoSD chips for high-purity immunomagnetic separation and high-sensitivity detection of gastric cancer cell-derived exosomes

Gastric cancer cell-derived exosomes as biomarkers have a very high application potential to the non-invasive detection of early-stage gastric cancer. However, the small size of exosomes (30-150 nm) results in huge challenges in separating and detecting them from complex media (e.g., plasma, urine, saliva, and cell culture supernatant). Here we proposed a highly integrated exosome separation and detection (ExoSD) chip to immunomagnetic separate exosomes from cell culture supernatant in a manner of continuous flow, and to immunofluorescence detect gastric cancer cell-derived exosomes with high sensitivity. The ExoSD chip has achieved a high exosome recovery (>80%) and purity (>83%) at the injection rate of 4.8 mL/h. Furthermore, experimental results based on clinical serum samples of patients with gastric cancer (stages I and II) show that the detection rate of the ExoSD chip is as high as 70%. The proposed ExoSD chip has been successfully demonstrated as a cutting-edge platform for exosomes separation and detection. It can be served as a versatile platform to extend to the applications of separation and detection of the other cell-derived exosomes or cells.

Small extracellular vesicles in cancer

Extracellular vesicles (EV) are lipid-bilayer enclosed vesicles in submicron size that are released from cells. A variety of molecules, including proteins, DNA fragments, RNAs, lipids, and metabolites can be selectively encapsulated into EVs and delivered to nearby and distant recipient cells. In tumors, through such intercellular communication, EVs can regulate initiation, growth, metastasis and invasion of tumors. Recent studies have found that EVs exhibit specific expression patterns which mimic the parental cell, providing a fingerprint for early cancer diagnosis and prognosis as well as monitoring responses to treatment. Accordingly, various EV isolation and detection technologies have been developed for research and diagnostic purposes. Moreover, natural and engineered EVs have also been used as drug delivery nanocarriers, cancer vaccines, cell surface modulators, therapeutic agents and therapeutic targets. Overall, EVs are under intense investigation as they hold promise for pathophysiological and translational discoveries. This comprehensive review examines the latest EV research trends over the last five years, encompassing their roles in cancer pathophysiology, diagnostics and therapeutics. This review aims to examine the full spectrum of tumor-EV studies and provide a comprehensive foundation to enhance the field. The topics which are discussed and scrutinized in this review encompass isolation techniques and how these issues need to be overcome for EV-based diagnostics, EVs and their roles in cancer biology, biomarkers for diagnosis and monitoring, EVs as vaccines, therapeutic targets, and EVs as drug delivery systems. We will also examine the challenges involved in EV research and promote a framework for catalyzing scientific discovery and innovation for tumor-EV-focused research.

Characterizing the Heterogeneity of Small Extracellular Vesicle Populations in Multiple Cancer Types via an Ultrasensitive Chip

Identifying small extracellular vesicle (sEV) subpopulations based on their different molecular signatures could potentially reveal the functional roles in physiology and pathology. However, it is a challenge to achieve this aim due to the nano-sized dimensions of sEVs, low quantities of biological cargo each sEV carries, and our incomplete knowledge of identifying features capable of separating heterogeneous sEV subpopulations. Here, a sensitive, multiplexed, and nano-mixing-enhanced sEV subpopulation characterization platform (ESCP) is proposed to precisely determine the sEV phenotypic heterogeneity and understand the role of sEV heterogeneity in cancer progression and metastasis. The ESCP utilizes spatially patterned anti-tetraspanin-functionalized micro-arrays for sEV subpopulation sorting and nanobarcode-based surface-enhanced Raman spectroscopy for multiplexed read-outs. An ESCP has been used for investigating sEV phenotypic heterogeneity in terms of canonical sEV tetraspanin molecules and cancer-associated protein biomarkers in both cancer cell line models and cancer patient samples. Our data explicitly demonstrate the selective enrichment of tetraspanins and cancer-associated protein biomarkers, in particular sEV subpopulations. Therefore, it is believed that the ESCP could enable the evaluation and broader application of sEV subpopulations as potential diagnostic disease biomarkers.

Establishment of a simplified dichotomic size-exclusion chromatography for isolating extracellular vesicles toward clinical applications

Size-exclusion chromatography (SEC) is a widely adopted method for the isolation of extracellular vesicles (EVs) from complex samples. SEC can efficiently remove high-abundant proteins, while often requires multiple fractionation operation using diversified column settings. In this study, we aim to establish a simplified SEC method to acquire high quality EVs. In comparison of all three cross-linked Sepharose resins with the sample types of FBS and human serum (HS), CL-6B and CL-4B showed superior performance in regular SEC to CL-2B in terms of significantly narrower EV and protein peaks, higher resolutions and EV purity. By increasing their bed volumes to 20 ml, the resolutions of CL-6B and CL-4B columns could be significantly improved, while the CL-6B column had the best performance with higher particle yields and tighter EV peaks. With the CL-6B 20 ml column, we further established a simplified dichotomic SEC method that only requires two bulk elutions to acquire EVs in the Eluate 1 and proteins in the Eluate 2. We further justified that such CL-6B columns were reusable for at least 10 consecutive times, and the dichotomic SEC was applicable to EV isolations from HS and FBS-free supernatants of fluorescently labelled and unlabelled SW620 cells. The proteomics analysis implicated that although the two methods had dissimilar abilities in removing different co-isolating contaminant proteins from EVs, the dichotomic SEC and ultracentrifugation could isolate EVs from human plasma with comparable purity. This dichotomic SEC has its intriguing potential to be used for EV preparation toward clinical testing and/or basic research.

Quantitative proteomic analysis of extracellular vesicle subgroups isolated by an optimized method combining polymer-based precipitation and size exclusion chromatography

The molecular characterization of extracellular vesicles (EVs) has revealed a great heterogeneity in their composition at a cellular and tissue level. Current isolation methods fail to efficiently separate EV subtypes for proteomic and functional analysis. The aim of this study was to develop a reproducible and scalable isolation workflow to increase the yield and purity of EV preparations. Through a combination of polymer‐based precipitation and size exclusion chromatography (Pre‐SEC), we analyzed two subsets of EVs based on their CD9, CD63 and CD81 content and elution time. EVs were characterized using transmission electron microscopy, nanoparticle tracking analysis, and Western blot assays. To evaluate differences in protein composition between the early‐ and late‐eluting EV fractions, we performed a quantitative proteomic analysis of MDA‐MB‐468‐derived EVs. We identified 286 exclusive proteins in early‐eluting fractions and 148 proteins with a differential concentration between early‐ and late‐eluting fractions. A density gradient analysis further revealed EV heterogeneity within each analyzed subgroup. Through a systems biology approach, we found significant interactions among proteins contained in the EVs which suggest the existence of functional clusters related to specific biological processes. The workflow presented here allows the study of EV subtypes within a single cell type and contributes to standardizing the EV isolation for functional studies.

Size-exclusion chromatography allows the isolation of EVs from the filamentous fungal plant pathogen Fusarium oxysporum f. sp. vasinfectum (Fov)

Extracellular vesicles (EVs) are nano-sized compartments involved in cell communication and macromolecule transport that are well characterized in mammalian organisms. Fungal EVs transport virulence-related cargo and modulate the host immune response, but most work has been focused on human yeast pathogens. Additionally, the study of EVs from filamentous fungi has been hindered by the lack of protein markers and efficient isolation methods. In this study we performed the isolation and proteomic characterization of EVs from the filamentous cotton pathogen Fusarium oxysporum f. sp. vasinfectum (Fov). EVs were recovered from two different growth media, Czapek Dox and Saboraud's dextrose broth, and purified by size-exclusion chromatography. Our results show that the EV proteome changes depending on the growth medium but EV production remains constant. EVs contained proteins involved in polyketide synthesis, cell wall modifications, proteases and potential effectors. These results support a role in modulation of host-pathogen interactions for Fov EVs.

Microproteomic sample preparation

Multiple applications of proteomics in life and health science, pathology and pharmacology, require handling size-limited cell and tissue samples. During proteomic sample preparation, analyte loss in these samples arises when standard procedures are used. Thus, specific considerations have to be taken into account for processing, that are summarised under the term microproteomics (μPs). Microproteomic workflows include: sampling (e.g., flow cytometry, laser capture microdissection), sample preparation (possible disruption of cells or tissue pieces via lysis, protein extraction, digestion in bottom-up approaches, and sample clean-up) and analysis (chromatographic or electrophoretic separation, mass spectrometric measurements and statistical/bioinformatic evaluation). All these steps must be optimised to reach wide protein dynamic ranges and high numbers of identifications. Under optimal conditions, sampling is adapted to the studied sample types and nature, sample preparation isolates and enriches the whole protein content, clean-up removes salts and other interferences such as detergents or chaotropes, and analysis identifies as many analytes as the instrumental throughput and sensitivity allow. In the suggested review, we present and discuss the current state in μP applications for processing of small number of cells (cell μPs) and microscopic tissue regions (tissue μPs).

Modern isolation and separation techniques for extracellular vesicles

Extracellular vesicles (EVs) are heterogenous membrane-bound vesicles released from various origins. EVs play a crucial role in cellular communication and mediate several physiological and pathological processes, highlighting their potential therapeutic and diagnostic applications. Due to the rapid increase in interests and needs to elucidate EV properties and functions, numerous isolation and separation approaches for EVs have been developed to overcome limitations of conventional techniques, such as ultracentrifugation. This review focuses on recently emerging and modern EV isolation and separation techniques, including size-, charge-, and affinity-based techniques while excluding ultracentrifugation and precipitation-based techniques due to their multiple limitations. The advantages and drawbacks of each technique are discussed together with insights into their applications. Emerging approaches all share similar features in terms of being time-effective, easy-to-operate, and capable of providing EVs with suitable and desirable purity and integrity for applications of interest. Combination and hyphenation of techniques have been used for EV isolation and separation to yield EVs with the best quality. The most recent development using an automated on-line system including selective affinity-based trapping unit and asymmetrical flow field-flow fractionation allows reliable isolation and fractionation of EV subpopulations from human plasma.

Exosomes in disease and regeneration: biological functions, diagnostics, and beneficial effects

Exosomes are a subtype of extracellular vesicles. They range from 30 to 150 nm in diameter and originate from intraluminal vesicles. Exosomes were first identified as the mechanism for releasing unnecessary molecules from reticulocytes as they matured to red blood cells. Since then, exosomes have been shown to be secreted by a broad spectrum of cells and play an important role in the cardiovascular system. Different stimuli are associated with increased exosome release and result in different exosome content. The release of harmful DNA and other molecules via exosomes has been proposed as a mechanism to maintain cellular homeostasis. Because exosomes contain parent cell-specific proteins on the membrane and in the cargo that is delivered to recipient cells, exosomes are potential diagnostic biomarkers of various types of diseases, including cardiovascular disease. As exosomes are readily taken up by other cells, stem cell-derived exosomes have been recognized as a potential cell-free regenerative therapy to repair not only the injured heart but other tissues as well. The objective of this review is to provide an overview of the biological functions of exosomes in heart disease and tissue regeneration. Therefore, state-of-the-art methods for exosome isolation and characterization, as well as approaches to assess exosome functional properties, are reviewed. Investigation of exosomes provides a new approach to the study of disease and biological processes. Exosomes provide a potential "liquid biopsy," as they are present in most, if not all, biological fluids that are released by a wide range of cell types.

Experimental and Biological Insights from Proteomic Analyses of Extracellular Vesicle Cargos in Normalcy and Disease

Extracellular vesicles (EVs) offer a vehicle for diagnostic and therapeutic utility. EVs carry bioactive cargo and an accrued interest in their characterization has emerged. Efforts at identifying EV-enriched protein or RNA led to a surprising realization that EVs are excessively heterogeneous in nature. This diversity is originally attributed to vesicle sizes but it is becoming evident that different classes of EVs vehiculate distinct molecular cargos. Therefore, one of the current challenges in EV research is their selective isolation in quantities sufficient for efficient downstream analyses. Many protocols have been developed; however, reproducibility between research groups can be difficult to reach and inter-studies analyses of data from different isolation protocols are unmanageable. Therefore, there is an unmet need to optimize and standardize methods and protocols for the isolation and purification of EVs. This review focuses on the diverse techniques and protocols used over the years to isolate and purify EVs with a special emphasis on their adequacy for proteomics applications. By combining recent advances in specific isolation methods that yield superior quality of EV preparations and mass spectrometry techniques, the field is now prepared for transformative advancements in establishing distinct categorization and cargo identification of subpopulations based on EV surface markers.

Integrated Dual-Mode Chromatography to Enrich Extracellular Vesicles from Plasma

Purifying extracellular vesicles (EVs) from complex biological fluids is a critical step in analyzing EVs molecularly. Plasma lipoprotein particles (LPPs) are a significant confounding factor as they outnumber EVs >104 -fold. Given their overlap in size, LPPs cannot be completely removed using standard size-exclusion chromatography. Density-based separation of LPPs can be applied but is impractical for routine use in clinical research and practice. Here a new separation approach, known as dual-mode chromatography (DMC), capable of enriching plasma EVs, and depleting LPPs is reported. DMC conveniently integrates two orthogonal separation steps in a single column device: i) size exclusion to remove high-density lipoproteins (HDLs) that are smaller than EVs; and ii) cation exchange to clear positively charged ApoB100-containing LPPs, mostly (very) low-density lipoproteins (V)LDLs, from negatively charged EVs. The strategy enables DMC to deplete most LPPs (>97% of HDLs and >99% of (V)LDLs) from human plasma, while retaining EVs (>30% of input). Furthermore, the two-in-one operation is fast (15 min per sample) and equipment-free. With abundant LPPs removed, DMC-prepared samples facilitate EV identification in imaging analyses and improve the accuracy for EV protein analysis.

Size-Exclusion Chromatography as a Technique for the Investigation of Novel Extracellular Vesicles in Cancer

Simple Summary

Extracellular vesicles (EVs) are small particles that are released by cancer cells, and they may hold vital information for researchers looking for early markers for diagnosis. Size-exclusion chromatography (SEC) is a classical technique that has become increasingly popular and can be used for rapid isolation and investigation of both their cargo and functionality. This systematic review highlights its main technical aspects, the type of materials involved and by covering the findings of the identified papers hopes to demonstrate the utility of this method in cancer research to date.

Abstract

Cancer cells release extracellular vesicles, which are a rich target for biomarker discovery and provide a promising mechanism for liquid biopsy. Size-exclusion chromatography (SEC) is an increasingly popular technique, which has been rediscovered for the purposes of extracellular vesicle (EV) isolation and purification from diverse biofluids. A systematic review was undertaken to identify all papers that described size exclusion as their primary EV isolation method in cancer research. In all, 37 papers were identified and discussed, which showcases the breadth of applications in which EVs can be utilised, from proteomics, to RNA, and through to functionality. A range of different methods are highlighted, with Sepharose-based techniques predominating. EVs isolated using SEC are able to identify cancer cells, highlight active pathways in tumourigenesis, clinically distinguish cohorts, and remain functionally active for further experiments.

Proteomic Analysis of Exosomes for Discovery of Protein Biomarkers for Prostate and Bladder Cancer

Extracellular vesicles (EVs) are released by nearly all cell types as part of normal cell physiology, transporting biological cargo, including nucleic acids and proteins, across the cell membrane. In pathological states such as cancer, EV-derived cargo may mirror the altered state of the cell of origin. Exosomes are the smaller, 50–150 nanometer-sized EVs released from fusion of multivesicular endosomes with the plasma membrane. Exosomes play important roles in cell-cell communication and participate in multiple cancer processes, including invasion and metastasis. Therefore, proteomic analysis of exosomes is a promising approach to discover potential cancer biomarkers, even though it is still at an early stage. Herein, we critically review the advances in exosome isolation methods and their compatibility with mass spectrometry (MS)-based proteomic analysis, as well as studies of exosomes in pathogenesis and progression of prostate and bladder cancer, two common urologic cancers whose incidence rates continue to rise annually. As urological tumors, both urine and blood samples are feasible for noninvasive or minimally invasive analysis. A better understanding of the biological cargo and functions of exosomes via high-throughput proteomics will help provide new insights into complex alterations in cancer and provide potential therapeutic targets and personalized treatment for patients.

Progress in Microfluidics-Based Exosome Separation and Detection Technologies for Diagnostic Applications

Exosomes are secreted by most cell types and circulate in body fluids. Recent studies have revealed that exosomes play a significant role in intercellular communication and are closely associated with the pathogenesis of disease. Therefore, exosomes are considered promising biomarkers for disease diagnosis. However, exosomes are always mixed with other components of body fluids. Consequently, separation methods for exosomes that allow high-purity and high-throughput separation with a high recovery rate and detection techniques for exosomes that are rapid, highly sensitive, highly specific, and have a low detection limit are indispensable for diagnostic applications. For decades, many exosome separation and detection techniques have been developed to achieve the aforementioned goals. However, in most cases, these two techniques are performed separately, which increases operation complexity, time consumption, and cost. The emergence of microfluidics offers a promising way to integrate exosome separation and detection functions into a single chip. Herein, an overview of conventional and microfluidics-based techniques for exosome separation and detection is presented. Moreover, the advantages and drawbacks of these techniques are compared.

Applications of Mass Spectrometry for Clinical Diagnostics: The Influence of Turnaround Time

This critical review discusses how the need for reduced clinical turnaround times has influenced chemical instrumentation. We focus on the development of modern mass spectrometry (MS) and its application in clinical diagnosis. With increased functionality that takes advantage of novel front-end modifications and computational capabilities, MS can now be used for non-traditional clinical analyses, including applications in clinical microbiology for bacteria differentiation and in surgical operation rooms. We summarize here recent developments in the field that have enabled such capabilities, which include miniaturization for point-of-care testing, direct complex mixture analysis via ambient ionization, chemical imaging and profiling, and systems integration.

Purity and yield of melanoma exosomes are dependent on isolation method

Both exosomes and soluble factors have been implicated in the generation of an immunosuppressive tumour microenvironment. Determining the contribution of each requires stringent control of purity of the isolated analytes. The present study compares several conventional exosome isolation methods for the presence of co-enriched soluble factors while isolating exosomes from human melanoma-derived cell lines. The resultant preparations were analysed by multiplex bead array analysis for cytokine profiles, and by electron microscopy and nanotracking analysis for exosome size distribution and concentration. It is demonstrated that the amount and repertoire of soluble factors in exosome preparations is dependent upon the isolation method used. A combination of ultrafiltration and size exclusion chromatography yielded up to 58-fold more exosomes than ultracentrifugation, up to 836-fold lower concentrations of co-purified soluble factors when adjusted for exosome yield, and a greater than two-fold increase in PD-L1 expressing exosomes. Mechanistically, in context of the immunomodulatory effects of exosomes, the exosome isolation method should be carefully considered in order to limit any effects due instead to co-eluted soluble factors.

Considerations and Implications in the Purification of Extracellular Vesicles - A Cautionary Tale

Extracellular vesicles (EVs) are nano-sized particles constitutively released from cells into all biological fluids. Interestingly, these vesicles contain genetic cargoes including proteins, RNA and bioactive lipids that can be functionally delivered and affect recipient cells. As a result, there is growing interest in studying EVs in pathological conditions, including central nervous system (CNS)-related diseases, as EVs may be used for diagnostic purposes or as therapeutic agents. However, one major bottleneck is the need for better EV purification strategies when considering complex biological sources such as serum/protein-rich media or plasma. In this study, we have performed a systematic comparison study between the current gold-standard method: ultracentrifugation, to an alternative: size-exclusion chromatography (LC), using induced pluripotent stem cell (iPSC) derived complex media as a model system. We demonstrate that LC allows for derivation of purer EVs from iPSCs, which was previously impossible with the original UC method. Importantly, our study further highlights the various drawbacks when using the conventional UC approach that lead to misinterpretation of EV data. Lastly, we describe novel data on our iPSC-EVs; how they could relate to stem cell biology and discuss their potential use as EV therapeutics for CNS diseases.

Recent advances in microfluidic methods in cancer liquid biopsy

Early cancer detection, its monitoring, and therapeutical prediction are highly valuable, though extremely challenging targets in oncology. Significant progress has been made recently, resulting in a group of devices and techniques that are now capable of successfully detecting, interpreting, and monitoring cancer biomarkers in body fluids. Precise information about malignancies can be obtained from liquid biopsies by isolating and analyzing circulating tumor cells (CTCs) or nucleic acids, tumor-derived vesicles or proteins, and metabolites. The current work provides a general overview of the latest on-chip technological developments for cancer liquid biopsy. Current challenges for their translation and their application in various clinical settings are discussed. Microfluidic solutions for each set of biomarkers are compared, and a global overview of the major trends and ongoing research challenges is given. A detailed analysis of the microfluidic isolation of CTCs with recent efforts that aimed at increasing purity and capture efficiency is provided as well. Although CTCs have been the focus of a vast microfluidic research effort as the key element for obtaining relevant information, important clinical insights can also be achieved from alternative biomarkers, such as classical protein biomarkers, exosomes, or circulating-free nucleic acids. Finally, while most work has been devoted to the analysis of blood-based biomarkers, we highlight the less explored potential of urine as an ideal source of molecular cancer biomarkers for point-of-care lab-on-chip devices.

Extracellular vesicle isolation methods: rising impact of size-exclusion chromatography

Extracellular vesicles (EVs) include a variety of nanosized vesicles released to the extracellular microenvironment by the vast majority of cells transferring bioactive lipids, proteins, mRNA, miRNA or non-coding RNA, as means of intercellular communication. Remarkably, among other fields of research, their use has become promising for immunomodulation, tissue repair and as source for novel disease-specific molecular signatures or biomarkers. However, a major challenge is to define accurate, reliable and easily implemented techniques for EV isolation due to their nanoscale size and high heterogeneity. In this context, differential ultracentrifugation (dUC) has been the most widely used laboratory methodology, but alternative procedures have emerged to allow purer EV preparations with easy implementation. Here, we present and discuss the most used of the different EV isolation methods, focusing on the increasing impact of size exclusion chromatography (SEC) on the resulting EV preparations from in vitro cultured cells-conditioned medium and biological fluids. Comparatively, low protein content and cryo-electron microscopy analysis show that SEC removes most of the overabundant soluble plasma proteins, which are not discarded using dUC or precipitating agents, while being more user friendly and less time-consuming than gradient-based EV isolation. Also, SEC highly maintains the major EVs' characteristics, including vesicular structure and content, which guarantee forthcoming applications. In sum, together with scaling-up possibilities to increase EV recovery and manufacturing following high-quality standards, SEC could be easily adapted to most laboratories to assist EV-associated biomarker discovery and to deliver innovative cell-free immunomodulatory and pro-regenerative therapies.