Label-Free Isolation of Exosomes Using Microfluidic Technologies

Utilizing engineered extracellular vesicles as delivery vectors in the management of ischemic stroke: a special outlook on mitochondrial delivery

Ischemic stroke is a secondary cause of mortality worldwide, imposing considerable medical and economic burdens on society. Extracellular vesicles, serving as natural nano-carriers for drug delivery, exhibit excellent biocompatibility in vivo and have significant advantages in the management of ischemic stroke. However, the uncertain distribution and rapid clearance of extracellular vesicles impede their delivery efficiency. By utilizing membrane decoration or by encapsulating therapeutic cargo within extracellular vesicles, their delivery efficacy may be greatly improved. Furthermore, previous studies have indicated that microvesicles, a subset of large-sized extracellular vesicles, can transport mitochondria to neighboring cells, thereby aiding in the restoration of mitochondrial function post-ischemic stroke. Small extracellular vesicles have also demonstrated the capability to transfer mitochondrial components, such as proteins or deoxyribonucleic acid, or their sub-components, for extracellular vesicle-based ischemic stroke therapy. In this review, we undertake a comparative analysis of the isolation techniques employed for extracellular vesicles and present an overview of the current dominant extracellular vesicle modification methodologies. Given the complex facets of treating ischemic stroke, we also delineate various extracellular vesicle modification approaches which are suited to different facets of the treatment process. Moreover, given the burgeoning interest in mitochondrial delivery, we delved into the feasibility and existing research findings on the transportation of mitochondrial fractions or intact mitochondria through small extracellular vesicles and microvesicles to offer a fresh perspective on ischemic stroke therapy.

Multi-omics analysis identified extracellular vesicles as biomarkers for cardiovascular diseases

Cell-derived extracellular vesicles (EVs) have emerged as a promising non-invasive liquid biopsy technique due to their accessibility and their ability to encapsulate and transport diverse biomolecules. EVs have garnered substantial research interest, notably in cardiovascular diseases (CVDs), where their roles in pathophysiology and as diagnostic and prognostic biomarkers are increasingly recognized. This review provides a comprehensive overview of EVs, starting with their origins, followed by the techniques used for their isolation and characterization. We explore the diverse cargo of EVs, including nucleic acids, proteins, lipids, and metabolites, highlighting their roles in intercellular communication and as potential biomarkers. We then delve into the application of genomics, transcriptomics, proteomics, and metabolomics in the analysis of EVs, particularly within the context of CVDs. Finally, we discuss how integrated multi-omics approaches are unveiling novel biomarkers, offering fresh insights into the diagnosis and prognosis of CVDs. This review underscores the growing importance of EVs in clinical diagnostics and the potential of multi-omics to propel future advancements in CVD biomarker discovery.

A stepwise multi-stage continuous dielectrophoresis separation microfluidic chip with microfilter structures

The separation of target microparticles using microfluidic systems owns extensive applications in biomedical, chemical, and materials science fields. Integration of microfluidic sorting systems employing dielectrophoresis (DEP) technology has been widely investigated. However, enhancing separation efficiency, purity, stability, and integration remains a pressing issue. This study proposes a stepwise multi-stage continuous DEP separation microfluidic chip with a microfilter structure. By leveraging a stepwise electrode configuration, a gradient electric field is generated to drive target microparticles along the electric field gradient, thereby enhancing separation efficiency. Innovative integration of a microfilter structure facilitates simultaneous filtration and improves flow field distribution, thus enhancing system stability. Through the synergistic effect of stepwise electrodes and the microfilter structure, superior coupling of electric and flow fields is achieved, consequently improving the sorting purity, separation efficiency, and system stability of the DEP-based microfluidic sorting system. Validation through simulation and separation of polystyrene microspheres demonstrates the excellent particle separation performance of the proposed system. It evidently shows potential for seamless extension to various biological microparticle sorting applications, harboring significant prospects in the biomedical domain field.

Enhancing Extracellular Vesicle Detection via Cotargeting Tetraspanin Biomarkers

Extracellular vesicles (EVs) are emerging as key diagnostic biomarkers due to their widespread presence in body fluids and the proteins on their surfaces, which reflect the identity and condition of their parent cells. Research has focused on detecting EVs with biosensors that target individual transmembrane proteins (TMPs) like tetraspanins. However, due to TMP heterogeneity and the formation of tetraspanin-enriched microdomains (TEMs), cotargeting multiple TMPs is a promising strategy for enhancing EV detection. In this work, we introduce a dual-antibody surface functionalization approach using surface plasmon resonance (SPR) biosensors to cotarget tetraspanins on EVs derived from mouse macrophages. The expression of EV tetraspanin markers followed the trend of CD9 > CD63 > CD81, which was consistent with the EV detection targeting their nontetraspanin partners, exhibiting LFA-1 > ICAM-1 > VCAM-1, and suggesting a differential role of tetraspanins with their associated TMPs. Cotargeting EV tetraspanins via CD81/CD63, CD81/CD9, and CD63/CD9 dual monoclonal antibody surfaces resulted in higher EV detection compared to predictions based on binding with two monoclonal antibodies against tetraspanins without cotargeting. Furthermore, the optimization of dual monoclonal antibody surface ratios to improve cotargeting effect yielded a statistically significant enhancement in the sensitivity of EV detection. These findings underscore the importance of TEMs in designing EV-based biosensing platforms to achieve optimized sensitivity in EV detection.

The impact of exosomes on bone health: A focus on osteoporosis

Osteoporosis is a widespread chronic condition. Although standard treatments are generally effective, they are frequently constrained by side effects and the risk of developing drug resistance. A promising area of research is the investigation of extracellular vesicles (EVs), including exosomes, microvesicles, and apoptotic bodies, which play a crucial role in bone metabolism. Exosomes, in particular, have shown significant potential in both the diagnosis and treatment of osteoporosis. EVs derived from osteoclasts, osteoblasts, mesenchymal stem cells, and other sources can influence bone metabolism, while exosomes from inflammatory and tumor cells may exacerbate bone loss, highlighting their dual role in osteoporosis pathology. This review offers a comprehensive overview of EV biogenesis, composition, and function in osteoporosis, focusing on their diagnostic and therapeutic potential. We examine the roles of various types of EVs and their cargo-proteins, RNAs, and lipids-in bone metabolism. Additionally, we explore the emerging applications of EVs as biomarkers and therapeutic agents, emphasizing the need for further research to address current challenges and enhance EV-based strategies for managing osteoporosis.

Advances in Extracellular-Vesicles-Based Diagnostic and Therapeutic Approaches for Ocular Diseases

Extracellular vesicles (EVs) are nanoscale membrane vesicles of various sizes that can be secreted by most cells. EVs contain a diverse array of cargo, including RNAs, lipids, proteins, and other molecules with functions of intercellular communication, immune modulation, and regulation of physiological and pathological processes. The biofluids in the eye, including tears, aqueous humor, and vitreous humor, are important sources for EV-based diagnosis of ocular disease. Because the molecular cargos may reflect the biology of their parental cells, EVs in these biofluids, as well as in the blood, have been recognized as promising candidates as biomarkers for early diagnosis of ocular disease. Moreover, EVs have also been used as therapeutics and targeted drug delivery nanocarriers in many ocular disorders because of their low immunogenicity and superior biocompatibility in nature. In this review, we provide an overview of the recent advances in the field of EV-based studies on the diagnosis and therapeutics of ocular disease. We summarized the origins of EVs applied in ocular disease, assessed different methods for EV isolation from ocular biofluid samples, highlighted bioengineering strategies of EVs as drug delivery systems, introduced the latest applications in the diagnosis and treatment of ocular disease, and presented their potential in the current clinical trials. Finally, we briefly discussed the challenges of EV-based studies in ocular disease and some issues of concern for better focusing on clinical translational studies of EVs in the future.

Hydrogel-exosome system in tissue engineering: A promising therapeutic strategy

Characterized by their pivotal roles in cell-to-cell communication, cell proliferation, and immune regulation during tissue repair, exosomes have emerged as a promising avenue for "cell-free therapy" in clinical applications. Hydrogels, possessing commendable biocompatibility, degradability, adjustability, and physical properties akin to biological tissues, have also found extensive utility in tissue engineering and regenerative repair. The synergistic combination of exosomes and hydrogels holds the potential not only to enhance the efficiency of exosomes but also to collaboratively advance the tissue repair process. This review has summarized the advancements made over the past decade in the research of hydrogel-exosome systems for regenerating various tissues including skin, bone, cartilage, nerves and tendons, with a focus on the methods for encapsulating and releasing exosomes within the hydrogels. It has also critically examined the gaps and limitations in current research, whilst proposed future directions and potential applications of this innovative approach.

Ultrasensitive Electrochemiluminescence Biosensor Based on DNA-Bio-Bar-Code and Hybridization Chain Reaction Dual Signal Amplification for Exosomes Detection

Exosomes have received considerable attention as potent reference markers for the diagnosis of various neoplasms due to their close and direct relationship with the proliferation, adhesion, and migration of tumor. The ultrasensitive detection of cancer-derived low-abundance exosomes is imperative, but still a great challenge. Herein, we report an electrochemiluminescence (ECL) biosensor based on the DNA-bio-bar-code and hybridization chain reaction (HCR)-mediated dual signal amplification for the ultrasensitive detection of cancer-derived exosomes. In this system, two types of aptamers were modified on the magnetic nanoprobe (MNPs) and gold nanoparticles (AuNPs) with numerous bio-bar-code DNA, respectively, which formed "sandwich" structures in the presence of specific target exosomes. The "sandwich" structures were separated under magnetic field, and the numerous bio-bar-code DNA were released by dissolving AuNPs. The released bio-bar-code DNA triggered the HCR procedure to produce a good deal of long DNA duplex structure for embedding in hemin, which generated strong ECL signal in the presence of coreactors for ultrasensitive detection of exosomes. Under the optimal conditions, it exhibited a good linearly of exosomes ranging from 10 to 104 exosomes particle μL-1 with limit of detection down to 5.01 exosome particle μL-1. Furthermore, the high ratio of ECL signal and minor change of ECL intensity indicated the good specificity, stability, and repeatability of this ECL biosensor. Given the good performance for exosome analysis, this ultrasensitive ECL biosensor has a promising application in the clinical diagnosis of early cancers.

Flow-electricity coupling fields enhance microfluidic platforms for efficient exosome isolation

Recently, exosomes have emerged as important biomarkers for cancer diagnosis, playing a significant role in disease diagnosis. Consequently, efficient isolation of exosomes from complex body fluids is now a critical focus in clinical research. We have designed and fabricated an exosome separation chip, leveraging the synergies of flow and electric fields through 3D printing technology. This approach harnesses the combined strengths of both fields, substantially enhancing separation efficiency and purity. This also effectively reduced the voltage required to form an electric field (from 120 V down to 10 V), minimizing the risk of Joule heating, thereby preserving the structural integrity and biological activity of the exosomes. Compared with the standard exosome separation method of ultracentrifugation (UC), our chip offers numerous benefits: it is cost-effective (under 50 RMB), boasts a high recovery rate (64.8%) and high purity (almost 100%), achieves remarkable separation efficiency (within 30 minutes), and is straightforward to operate. Moreover, since an unmarked separation method is used, the separated exosomes can be directly used for downstream detection and analysis, which has certain practicality for future clinical research and application.

Immunoassays for Extracellular Vesicle Detection via Transmembrane Proteins Using Surface Plasmon Resonance Biosensors

Extracellular vesicles (EVs) are preeminent carriers of biomarkers and have become the subject of intense biomedical research for medical diagnostics using biosensors. To create effective EV-based immunoassays, it is imperative to develop surface chemistry approaches with optimal EV detection targeting transmembrane protein biomarkers that are not affected by cell-to-cell variability. Here, we developed a series of immunoassays for the detection of EVs derived from mouse monocyte cells using surface plasmon resonance (SPR) biosensors. We chemically immobilized antibodies onto mixed self-assembled monolayers of oligo ethylene glycol (OEG) alkanethiolates with carboxylic and hydroxylic terminal groups. The effects of antibody clonality (monoclonal vs polyclonal) and antibody surface coverage in targeting EVs via CD81 tetraspanins were investigated. We determined binding kinetic parameters, establishing trends from steric hindrance effects and epitope recognition properties of antibodies. Our results indicate that a 40% surface coverage of polyclonal antibodies covalently linked onto a mixed SAM with 10% of terminated -COOH groups yields a promising approach for EV detection with a linear range of 1.9 × 108-1.9 × 109 EVs/mL and a limit of detection of 5.9 × 106 EVs/mL. This optimal immunoassay exhibits a 1.92 nM equilibrium dissociation constant for bound EVs, suggesting a high binding affinity when CD81 is targeted. Our study provides important insights into surface chemistry development for EV detection targeted via transmembrane protein biomarkers using antibodies, which has promising applications for disease diagnostics.

Therapeutic Potential of Mesenchymal Stem Cell-Derived Exosomes as Nanomedicine for Peripheral Nerve Injury

Peripheral nerve injury (PNI) is a complex and protracted process, and existing therapeutic approaches struggle to achieve effective nerve regeneration. Recent studies have shown that mesenchymal stem cells (MSCs) may be a pivotal choice for treating peripheral nerve injury. MSCs possess robust paracrine capabilities, and exosomes, as the primary secretome of MSCs, are considered crucial regulatory mediators involved in peripheral nerve regeneration. Exosomes, as nanocarriers, can transport various endogenous or exogenous bioactive substances to recipient cells, thereby promoting vascular and axonal regeneration while suppressing inflammation and pain. In this review, we summarize the mechanistic roles of exosomes derived from MSCs in peripheral nerve regeneration, discuss the engineering strategies for MSC-derived exosomes to improve therapeutic potential, and explore the combined effects of MSC-derived exosomes with biomaterials (nerve conduits, hydrogels) in peripheral nerve regeneration.

Mesenchymal Stem Cell-Derived Exosomes as Drug Delivery Vehicles in Disease Therapy

Exosomes are small vesicles containing proteins, nucleic acids, and biological lipids, which are responsible for intercellular communication. Studies have shown that exosomes can be utilized as effective drug delivery vehicles to accurately deliver therapeutic substances to target tissues, enhancing therapeutic effects and reducing side effects. Mesenchymal stem cells (MSCs) are a class of stem cells widely used for tissue engineering, regenerative medicine, and immunotherapy. Exosomes derived from MSCs have special immunomodulatory functions, low immunogenicity, the ability to penetrate tumor tissues, and high yield, which are expected to be engineered into efficient drug delivery systems. Despite the promising promise of MSC-derived exosomes, exploring their optimal preparation methods, drug-loading modalities, and therapeutic potential remains challenging. Therefore, this article reviews the related characteristics, preparation methods, application, and potential risks of MSC-derived exosomes as drug delivery systems in order to find potential therapeutic breakthroughs.

Emerging role of exosomal microRNA in liver cancer in the era of precision medicine; potential and challenges

Exosomal microRNAs (miRNAs) have great potential in the fight against hepatocellular carcinoma (HCC), the fourth most common cause of cancer-related death worldwide. In this study, we explored the various applications of these small molecules while analyzing their complex roles in tumor development, metastasis, and changes in the tumor microenvironment. We also discussed the complex interactions that exist between exosomal miRNAs and other non-coding RNAs such as circular RNAs, and show how these interactions coordinate important biochemical pathways that propel the development of HCC. The possibility of targeting exosomal miRNAs for therapeutic intervention is paramount, even beyond their mechanistic significance. We also highlighted their growing potential as cutting-edge biomarkers that could lead to tailored treatment plans by enabling early identification, precise prognosis, and real-time treatment response monitoring. This thorough analysis revealed an intricate network of exosomal miRNAs lead to HCC progression. Finally, strategies for purification and isolation of exosomes and advanced biosensing techniques for detection of exosomal miRNAs are also discussed. Overall, this comprehensive review sheds light on the complex web of exosomal miRNAs in HCC, offering valuable insights for future advancements in diagnosis, prognosis, and ultimately, improved outcomes for patients battling this deadly disease.

Extracellular Vesicle-Inspired Therapeutic Strategies for the COVID-19

Emerging infectious diseases like coronavirus pneumonia (COVID-19) present significant challenges to global health, extensively affecting both human society and the economy. Extracellular vesicles (EVs) have demonstrated remarkable potential as crucial biomedical tools for COVID-19 diagnosis and treatment. However, due to limitations in the performance and titer of natural vesicles, their clinical use remains limited. Nonetheless, EV-inspired strategies are gaining increasing attention. Notably, biomimetic vesicles, inspired by EVs, possess specific receptors that can act as "Trojan horses," preventing the virus from infecting host cells. Genetic engineering can enhance these vesicles by enabling them to carry more receptors, significantly increasing their specificity for absorbing the novel coronavirus. Additionally, biomimetic vesicles inherit numerous cytokine receptors from parent cells, allowing them to effectively mitigate the "cytokine storm" by adsorbing pro-inflammatory cytokines. Overall, this EV-inspired strategy offers new avenues for the treatment of emerging infectious diseases. Herein, this review systematically summarizes the current applications of EV-inspired strategies in the diagnosis and treatment of COVID-19. The current status and challenges associated with the clinical implementation of EV-inspired strategies are also discussed. The goal of this review is to provide new insights into the design of EV-inspired strategies and expand their application in combating emerging infectious diseases.

A self-cleaning micro-fluidic chip biospired by the filtering system of manta rays

Size-based particle filtration has become indispensable in numerous biomedical and environmental applications. In this study, bioinspired by the filter-feeding mechanism (lobe filtration) of manta rays, we designed a U-shaped biomimetic gill rake filter that combined lobe filtration and Dean flow to filter monodisperse suspensions, bi-disperse suspensions and yeast cells. Compared with other equipment using the inertial focusing technology, our equipment can perform high-throughput (up to 8 mL min-1) and high-efficiency filtration of particles (maximum filtration efficiencies of 96.08% and 97.14% for 10 and 15 μm monodisperse suspensions at the optimum flow rate of 6 mL min-1). The complex velocity field of the micro-fluidic flow within the filter is numerically simulated, and in combination with experiments, a threshold for the flow rate is identified. When the inlet flow rate exceeds the threshold value, the efficiency of particle filtration is increased rapidly. Afterwards, by analysing the filtration mechanism, we develop three novel filtration processes. The equilibrium positions of the particles and yeast cells in the main channel are close to the outer wall at high flow rate, which diminishes the likelihood of particles and yeast cells entering the side channel. This configuration establishes a self-cleaning mechanism, ensuring prolonged and efficient operation of the filter with high-throughput processing. Furthermore, the influence of the filter lobe angle and channel width on the filtration efficiency and outlet flow rate ratio are explored, and an optimisation plan is prepared.

Bifunctional immunoaffinity magnetic nanoparticles for high-efficiency separation of exosomes based on host-guest interaction

The investigation of exosomes holds substantial importance in the field of disease diagnosis and prognosis, where in the rapid and low-loss isolation of exosomes emerges as a crucial step owing to their exceedingly low concentration in bodily fluids. Herein, bifunctional immunoaffinity magnetic nanoparticles (BI-NPs) were successfully constructed by binding Ti4+ and antibody to magnetic nanoparticles through host-guest interaction. Exosomes in the cell culture supernatant could be effectively captured by the BI-NPs and then gently eluted with α-CD and 10% ammonia solution. Following the elution process, the content of captured exosome protein was determined to be up to 97 μg/mL. A total of 2822 protein groups were identified in the exosomes isolated by BI-NPs, 1060 protein groups were derived from exosomes. At the same time, the mass of exosome protein obtained by BI-NPs was more than 2 times that of UC isolation, and the above results indicated that BI-NPs had high purity enrichment performance. This is attributed to the fact that BI-NPs combine the dual affinity of Ti4+ and antibody to achieve efficient enrichment of exosomes, in addition to the mild elution property of BI-NPs due to the presence of the host-guest system. BI-NPs offer a novel approach for the isolation of exosomes, in order to further promote the application of exosomes in the required fields.

A novel viscoelastic microfluidic platform for nanoparticle/small extracellular vesicle separation through viscosity gradient-induced migration

Small extracellular vesicles (sEVs) are extracellular vesicles with diameters ranging from 30 to 150 nm, harboring proteins and nucleic acids that reflect their source cells and act as vital mediators of intercellular communication. The comprehensive analysis of sEVs is hindered by the complex composition of biofluids that contain various extracellular vesicles. Conventional separation methods, such as ultracentrifugation and immunoaffinity capture, face routine challenges in operation complexity, cost, and compromised recovery rates. Microfluidic technologies, particularly viscoelastic microfluidics, offer a promising alternative for sEV separation due to its field-free nature, fast and simple operation procedure, and minimal sample consumption. In this context, we here introduce an innovative viscoelastic approach designed to exploit the viscosity gradient-induced force with size-dependent characteristics, thereby enabling the efficient separation of nano-sized particles and sEVs from larger impurities. We first seek to illustrate the underlying mechanism of the viscosity gradient-induced force, followed by experimental validation with fluorescent nanoparticles demonstrating separation results consistent with qualitative analysis. We believe that this work is the first to report such viscosity gradient-induced phenomenon in the microfluidic context. The presented approach achieves ∼80% for both target purity and recovery rate. We further demonstrate effective sEV separation using our device to showcase its efficacy in the real biological context, highlighting its potential as a versatile, label-free platform for sEV analysis in both fundamental biological research and clinical applications.

Exosomes in the pathogenesis and treatment of cancer-related cachexia

Cancer-related cachexia is a metabolic syndrome characterized by weight loss, adipose tissue decomposition, and progressive skeletal muscle atrophy. It is a major complication of many advanced cancers and seriously affects the quality of life and survival of cancer patients. However, the specific molecules that mediate cancer-related cachexia remain elusive, and the fundamental cellular and molecular mechanisms associated with muscle atrophy and lipidolysis in cancer patients still need to be investigated. Exosomes, a newly discovered class of small extracellular vesicles that facilitate intercellular communication, have a significant role in the onset and development of various cancers. Studies have shown that exosomes play a role in the onset and progression of cancer-related cachexia by transporting active molecules such as nucleic acids and proteins. This review aimed to provide an overview of exosome developments in cancer-induced skeletal muscle atrophy and adipose tissue degradation. More importantly, exosomes were shown to have potential as diagnostic markers or therapeutic strategies for cachexia and were prospected, providing novel strategies for the diagnosis and treatment of cancer-related cachexia.

Exosomal noncoding RNAs in gynecological cancers: implications for therapy resistance and biomarkers

Gynecologic cancers, including ovarian cancer (OC), cervical cancer (CC), and endometrial cancer (EC), pose a serious threat to women's health and quality of life due to their high incidence and lethality. Therapeutic resistance in tumors refers to reduced sensitivity of tumor cells to therapeutic drugs or radiation, which compromises the efficacy of treatment or renders it ineffective. Therapeutic resistance significantly contributes to treatment failure in gynecologic tumors, although the specific molecular mechanisms remain unclear. Exosomes are nanoscale vesicles released and received by distinct kinds of cells. Exosomes contain proteins, lipids, and RNAs closely linked to their origins and functions. Recent studies have demonstrated that exosomal ncRNAs may be involved in intercellular communication and can modulate the progression of tumorigenesis, aggravation and metastasis, tumor microenvironment (TME), and drug resistance. Besides, exosomal ncRNAs also have the potential to become significant diagnostic and prognostic biomarkers in various of diseases. In this paper, we reviewed the biological roles and mechanisms of exosomal ncRNAs in the drug resistance of gynecologic tumors, as well as explored the potential of exosomal ncRNAs acting as the liquid biopsy molecular markers in gynecologic cancers.

High-Performance Gel-Free and Label-Free Size Fractionation of Extracellular Vesicles with Two-Dimensional Electrophoresis in a Microfluidic Artificial Sieve

Extracellular vesicles (EVs) are cell-derived particles that exhibit diverse sizes, molecular contents, and clinical implications for various diseases depending on their specific subpopulations. However, fractionation of EV subpopulations with high resolution, efficiency, purity, and yield remains an elusive goal due to their diminutive sizes. In this study, we introduce a novel strategy that effectively separates EV subpopulations in a gel-free and label-free manner, using two-dimensional (2D) electrophoresis in a microfluidic artificial sieve. The microfabricated artificial sieve consists of periodically arranged micro-slit-well structures in a 2D array and generates an anisotropic electric field pattern to size fractionate EVs into discrete streams and steer the subpopulations into designated outlets for collection within a minute. Along with fractionating EV subpopulations, contaminants such as free proteins and short nucleic acids can be simultaneously directed to waste outlets, thus accomplishing both size fractionation and purification of EVs with high performance. Our platform offers a simple, rapid, and versatile solution for EV subpopulation isolation, which can potentially facilitate the discovery of biomarkers for specific EV subtypes and the development of EV-based therapeutics.

Intercellular crosstalk between cancer cells and cancer-associated fibroblasts via exosomes in gastrointestinal tumors

Gastrointestinal (GI) tumors are a significant global health threat, with high rates of morbidity and mortality. Exosomes contain various biologically active molecules like nucleic acids, proteins, and lipids and can serve as messengers for intercellular communication. They play critical roles in the exchange of information between tumor cells and the tumor microenvironment (TME). The TME consists of mesenchymal cells and components of the extracellular matrix (ECM), with fibroblasts being the most abundant cell type in the tumor mesenchyme. Cancer-associated fibroblasts (CAFs) are derived from normal fibroblasts and mesenchymal stem cells that are activated in the TME. CAFs can secrete exosomes to modulate cell proliferation, invasion, migration, drug resistance, and other biological processes in tumors. Additionally, tumor cells can manipulate the function and behavior of fibroblasts through direct cell-cell interactions. This review provides a summary of the intercellular crosstalk between GI tumor cells and CAFs through exosomes, along with potential underlying mechanisms.

Engineered Extracellular Vesicles in Wound Healing: Design, Paradigms, and Clinical Application

The severe quality of life and economic burden imposed by non-healing skin wounds, infection risks, and treatment costs are affecting millions of patients worldwide. To mitigate these challenges, scientists are relentlessly seeking effective treatment measures. In recent years, extracellular vesicles (EVs) have emerged as a promising cell-free therapy strategy, attracting extensive attention from researchers. EVs mediate intercellular communication, possessing excellent biocompatibility and stability. These features make EVs a potential tool for treating a plethora of diseases, including those related to wound repair. However, there is a growing focus on the engineering of EVs to overcome inherent limitations such as low production, relatively fixed content, and targeting capabilities of natural EVs. This engineering could improve both the effectiveness and specificity of EVs in wound repair treatments. In light of this, the present review will introduce the latest progress in the design methods and experimental paradigms of engineered EVs applied in wound repair. Furthermore, it will comprehensively analyze the current clinical research status and prospects of engineered EVs within this field.

Microfluidic Platforms for Real-Time In Situ Monitoring of Biomarkers for Cellular Processes

Cellular processes are mechanisms carried out at the cellular level that are aimed at guaranteeing the stability of the organism they comprise. The investigation of cellular processes is key to understanding cell fate, understanding pathogenic mechanisms, and developing new therapeutic technologies. Microfluidic platforms are thought to be the most powerful tools among all methodologies for investigating cellular processes because they can integrate almost all types of the existing intracellular and extracellular biomarker-sensing methods and observation approaches for cell behavior, combined with precisely controlled cell culture, manipulation, stimulation, and analysis. Most importantly, microfluidic platforms can realize real-time in situ detection of secreted proteins, exosomes, and other biomarkers produced during cell physiological processes, thereby providing the possibility to draw the whole picture for a cellular process. Owing to their advantages of high throughput, low sample consumption, and precise cell control, microfluidic platforms with real-time in situ monitoring characteristics are widely being used in cell analysis, disease diagnosis, pharmaceutical research, and biological production. This review focuses on the basic concepts, recent progress, and application prospects of microfluidic platforms for real-time in situ monitoring of biomarkers in cellular processes.

The role and applications of extracellular vesicles in osteoporosis

Osteoporosis is a widely observed condition characterized by the systemic deterioration of bone mass and microarchitecture, which increases patient susceptibility to fragile fractures. The intricate mechanisms governing bone homeostasis are substantially impacted by extracellular vesicles (EVs), which play crucial roles in both pathological and physiological contexts. EVs derived from various sources exert distinct effects on osteoporosis. Specifically, EVs released by osteoblasts, endothelial cells, myocytes, and mesenchymal stem cells contribute to bone formation due to their unique cargo of proteins, miRNAs, and cytokines. Conversely, EVs secreted by osteoclasts and immune cells promote bone resorption and inhibit bone formation. Furthermore, the use of EVs as therapeutic modalities or biomaterials for diagnosing and managing osteoporosis is promising. Here, we review the current understanding of the impact of EVs on bone homeostasis, including the classification and biogenesis of EVs and the intricate regulatory mechanisms of EVs in osteoporosis. Furthermore, we present an overview of the latest research progress on diagnosing and treating osteoporosis by using EVs. Finally, we discuss the challenges and prospects of translational research on the use of EVs in osteoporosis.

Recent Progress in Prompt Molecular Detection of Exosomes Using CRISPR/Cas and Microfluidic-Assisted Approaches Toward Smart Cancer Diagnosis and Analysis

Exosomes are essential indicators of molecular mechanisms involved in interacting with cancer cells and the tumor environment. As nanostructures based on lipids and nucleic acids, exosomes provide a communication pathway for information transfer by transporting biomolecules from the target cell to other cells. Importantly, these extracellular vesicles are released into the bloodstream by the most invasive cells, i. e., cancer cells; in this way, they could be considered a promising specific biomarker for cancer diagnosis. In this matter, CRISPR-Cas systems and microfluidic approaches could be considered practical tools for cancer diagnosis and understanding cancer biology. CRISPR-Cas systems, as a genome editing approach, provide a way to inactivate or even remove a target gene from the cell without affecting intracellular mechanisms. These practical systems provide vital information about the factors involved in cancer development that could lead to more effective cancer treatment. Meanwhile, microfluidic approaches can also significantly benefit cancer research due to their proper sensitivity, high throughput, low material consumption, low cost, and advanced spatial and temporal control. Thereby, employing CRISPR-Cas- and microfluidics-based approaches toward exosome monitoring could be considered a valuable source of information for cancer therapy and diagnosis. This review assesses the recent progress in these promising diagnosis approaches toward accurate cancer therapy and in-depth study of cancer cell behavior.

The Current Status and Future Direction of Extracellular Nano-vesicles in the Alleviation of Skin Disorders

Exosomes are extracellular vesicles (EVs) that originate from endocytic membranes. The transfer of biomolecules and biological compounds such as enzymes, proteins, RNA, lipids, and cellular waste disposal through exosomes plays an essential function in cell-cell communication and regulation of pathological and physiological processes in skin disease. The skin is one of the vital organs that makes up about 8% of the total body mass. This organ consists of three layers, epidermis, dermis, and hypodermis that cover the outer surface of the body. Heterogeneity and endogeneity of exosomes is an advantage that distinguishes them from nanoparticles and liposomes and leads to their widespread usage in the remedy of dermal diseases. The biocompatible nature of these extracellular vesicles has attracted the attention of many health researchers. In this review article, we will first discuss the biogenesis of exosomes, their contents, separation methods, and the advantages and disadvantages of exosomes. Then we will highlight recent developments related to the therapeutic applications of exosomes in the treatment of common skin disorders like atopic dermatitis, alopecia, epidermolysis bullosa, keloid, melanoma, psoriasis, and systemic sclerosis.

Measuring the electrophoretic mobility and size of single particles using microfluidic transverse AC electrophoresis (TrACE)

The ability to measure the charge and size of single particles is essential to understanding particle adhesion and interaction with their environment. Characterizing the physical properties of biological particles, like cells, can be a powerful tool in studying the association between the changes in physical properties and disease development. Currently, measuring charge via the electrophoretic mobility (μep) of individual particles remains challenging, and there is only one prior report of simultaneously measuring μep and size. We introduce microfluidic transverse AC electrophoresis (TrACE), a novel technique that combines particle tracking velocimetry (PTV) and AC electrophoresis. In TrACE, electric waves with 0.75 to 1.5 V amplitude are applied transversely to the bulk flow and cause the particles to oscillate. PTV records the particles' oscillating trajectories as pressure drives bulk flow through the microchannel. A simple quasi-equilibrium model agrees well with experimental measurements of frequency, amplitude, and phase, indicating that particle motion is largely described by DC electrophoresis. The measured μep of polystyrene particles (0.53, 0.84, 1, and 2 μm diameter) are consistent with ELS measurements, and precision is enhanced by averaging ∼100 measurements per particle. Particle size is simultaneously measured from Brownian motion quantified from the trajectory for particles <2 μm or image analysis for particles ≥2 μm. Lastly, the ability to analyze intact mammalian cells is demonstrated with B cells. TrACE systems are expected to be highly suitable as fieldable tools to measure the μep and size of a broad range of individual particles.

Application of microfluidic technology based on surface-enhanced Raman scattering in cancer biomarker detection: A review

With the continuous discovery and research of predictive cancer-related biomarkers, liquid biopsy shows great potential in cancer diagnosis. Surface-enhanced Raman scattering (SERS) and microfluidic technology have received much attention among the various cancer biomarker detection methods. The former has ultrahigh detection sensitivity and can provide a unique fingerprint. In contrast, the latter has the characteristics of miniaturization and integration, which can realize accurate control of the detection samples and high-throughput detection through design. Both have the potential for point-of-care testing (POCT), and their combination (lab-on-a-chip SERS (LoC-SERS)) shows good compatibility. In this paper, the basic situation of circulating proteins, circulating tumor cells, exosomes, circulating tumor DNA (ctDNA), and microRNA (miRNA) in the diagnosis of various cancers is reviewed, and the detection research of these biomarkers by the LoC-SERS platform in recent years is described in detail. At the same time, the challenges and future development of the platform are discussed at the end of the review. Summarizing the current technology is expected to provide a reference for scholars engaged in related work and interested in this field.

Emerging Microfluidic Tools for Simultaneous Exosomes and Cargo Biosensing in Liquid Biopsy: New Integrated Miniaturized FFF-Assisted Approach for Colon Cancer Diagnosis

The early-stage diagnosis of cancer is a crucial clinical need. The inadequacies of surgery tissue biopsy have prompted a transition to a less invasive profiling of molecular biomarkers from biofluids, known as liquid biopsy. Exosomes are phospholipid bilayer vesicles present in many biofluids with a biologically active cargo, being responsible for cell-to-cell communication in biological systems. An increase in their excretion and changes in their cargo are potential diagnostic biomarkers for an array of diseases, including cancer, and they constitute a promising analyte for liquid biopsy. The number of exosomes released, the morphological properties, the membrane composition, and their content are highly related to the physiological and pathological states. The main analytical challenge to establishing liquid biopsy in clinical practice is the development of biosensors able to detect intact exosomes concentration and simultaneously analyze specific membrane biomarkers and those contained in their cargo. Before analysis, exosomes also need to be isolated from biological fluids. Microfluidic systems can address several issues present in conventional methods (i.e., ultracentrifugation, size-exclusion chromatography, ultrafiltration, and immunoaffinity capture), which are time-consuming and require a relatively high amount of sample; in addition, they can be easily integrated with biosensing systems. A critical review of emerging microfluidic-based devices for integrated biosensing approaches and following the major analytical need for accurate diagnostics is presented here. The design of a new miniaturized biosensing system is also reported. A device based on hollow-fiber flow field-flow fractionation followed by luminescence-based immunoassay is applied to isolate intact exosomes and characterize their cargo as a proof of concept for colon cancer diagnosis.

An immuno-magnetophoresis-based microfluidic chip to isolate and detect HER2-Positive cancer-derived exosomes via multiple separation

Exosomes are useful for cancer diagnosis and monitoring. However, clinical samples contain impurities that complicate direct analyses of cancer-derived exosomes. Therefore, a microfluidic chip-based magnetically labeled exosome isolation system (MEIS-chip) was developed as a lab-on-a-chip platform for human epidermal growth factor receptor 2 (HER2)-positive cancer diagnosis and monitoring. Various magnetic nanoclusters (MNCs) were synthesized with different degrees of magnetization, and antibodies were introduced to capture HER2-overexpressing and common exosomes using immunoaffinity. MNC-bonded exosomes were separated into different exits according to their magnetization degrees. The MEIS-chip efficiently separated HER2-overexpressing exosomes from common exosomes that did not contain disease-related information. The simultaneous separation of HER2-and non-HER2-overexpressing exosomes provided a means of analyzing high-purity HER2-overexpressing exosomes while minimizing the contribution of non-target exosomes, reducing misdiagnosis risk. Notably, common exosomes served as a negative control for monitoring real-time changes in HER2 expression. These findings support the application of MEIS-chip for cancer diagnosis and treatment monitoring via effective exosome isolation.

A review of the zone broadening contributions in free-flow electrophoresis

The broadening of analyte streams, as they migrate through a free-flow electrophoresis (FFE) channel, often limits the resolving power of FFE separations. Under laminar flow conditions, such zonal spreading occurs due to analyte diffusion perpendicular to the direction of streamflow and variations in the lateral distance electrokinetically migrated by the analyte molecules. Although some of the factors that give rise to these contributions are inherent to the FFE method, others originate from non-idealities in the system, such as Joule heating, pressure-driven crossflows, and a difference between the electrical conductivities of the sample stream and background electrolyte. The injection process can further increase the stream width in FFE separations but normally influencing all analyte zones to an equal extent. Recently, several experimental and theoretical works have been reported that thoroughly investigate the various contributions to stream variance in an FFE device for better understanding, and potentially minimizing their magnitudes. In this review article, we carefully examine the findings from these studies and discuss areas in which more work is needed to advance our comprehension of the zone broadening contributions in FFE assays.

In Situ Capturing and Counting Device for the Specific Depletion and Purification of Cancer-Derived Exosomes

From metabolic waste to biological mediators, exosomes have emerged as the key player in a variety of pathological processes, particularly in oncogenesis. The exosome-mediated communication network involves nearly every step of cancer progression, promoting the proliferation and immune escape of cancer cells. Therefore, the removal of cancer-derived exosomes has profound clinical significance. Current methods for exosome separation and enrichment are either for large-scale samples or require complex pretreatment processes, lacking effective methods for trace-volume exosome capture in situ. Herein, we have developed an in situ exosome capturing and counting device based on the antibody-functionalized capillary. Specific antibodies targeting exosome biomarkers were immobilized to the inner wall of the capillary via biotin-streptavidin interaction for direct cancer exosome capturing. Subsequent exosome staining enabled imaging and enumeration. Acceptable linearity and reproducibility were achieved with our device, with the capturing and detective range between 3.3 × 104 and 3.3 × 108 particles, surpassing the nanoparticle tracking analysis by 2 orders of magnitude while requiring merely 30 μL sample. We demonstrated that MCF-7-derived exosomes induced epithelial-mesenchymal transition of epithelial cells MCF-10A, and our method was able to completely or partially reverse the transition by complete depletion or specific depletion of cancer exosomes without any preprocessing. Moreover, both whole exosomes and cancer-specific exosomes alone from mimic blood samples were successfully captured and counted, without obvious non-specific adsorption. In all, our approach realized the in situ depletion and number-counting of cancer-derived exosomes directly from the complex humoral environment, having the potential to provide a comprehensive tumor therapeutic and prognosis evaluation tool by targeted hemodialysis and counting of tumor-derived exosomes.

Critical considerations in determining the surface charge of small extracellular vesicles

Small extracellular vesicles (EVs) have emerged as a focal point of EV research due to their significant role in a wide range of physiological and pathological processes within living systems. However, uncertainties about the nature of these vesicles have added considerable complexity to the already difficult task of developing EV-based diagnostics and therapeutics. Whereas small EVs have been shown to be negatively charged, their surface charge has not yet been properly quantified. This gap in knowledge has made it challenging to fully understand the nature of these particles and the way they interact with one another, and with other biological structures like cells. Most published studies have evaluated EV charge by focusing on zeta potential calculated using classical theoretical approaches. However, these approaches tend to underestimate zeta potential at the nanoscale. Moreover, zeta potential alone cannot provide a complete picture of the electrical properties of small EVs since it ignores the effect of ions that bind tightly to the surface of these particles. The absence of validated methods to accurately estimate the actual surface charge (electrical valence) and determine the zeta potential of EVs is a significant knowledge gap, as it limits the development of effective label-free methods for EV isolation and detection. In this study, for the first time, we show how the electrical charge of small EVs can be more accurately determined by accounting for the impact of tightly bound ions. This was accomplished by measuring the electrophoretic mobility of EVs, and then analytically correlating the measured values to their charge in the form of zeta potential and electrical valence. In contrast to the currently used theoretical expressions, the employed analytical method in this study enabled a more accurate estimation of EV surface charge, which will facilitate the development of EV-based diagnostic and therapeutic applications.

Advances in extracellular vesicle functionalization strategies for tissue regeneration

Extracellular vesicles (EVs) are nano-scale vesicles derived by cell secretion with unique advantages such as promoting cell proliferation, anti-inflammation, promoting blood vessels and regulating cell differentiation, which benefit their wide applications in regenerative medicine. However, the in vivo therapeutic effect of EVs still greatly restricted by several obstacles, including the off-targetability, rapid blood clearance, and undesired release. To address these issues, biomedical engineering techniques are vastly explored. This review summarizes different strategies to enhance EV functions from the perspective of drug loading, modification, and combination of biomaterials, and emphatically introduces the latest developments of functionalized EV-loaded biomaterials in different diseases, including cardio-vascular system diseases, osteochondral disorders, wound healing, nerve injuries. Challenges and future directions of EVs are also discussed.

Recent advances in isolation and detection of exosomal microRNAs related to Alzheimer's disease

Alzheimer's disease, a progressive neurological condition, is associated with various internal and external risk factors in the disease's early stages. Early diagnosis of Alzheimer's disease is essential for treatment management. Circulating exosomal microRNAs could be a new class of valuable biomarkers for early Alzheimer's disease diagnosis. Different kinds of biosensors have been introduced in recent years for the detection of these valuable biomarkers. Isolation of the exosomes is a crucial step in the detection process which is traditionally carried out by multi-step ultrafiltration. Microfluidics has improved the efficiency and costs of exosome isolation by implementing various effects and forces on the nano and microparticles in the microchannels. This paper reviews recent advancements in detecting Alzheimer's disease related exosomal microRNAs based on methods such as electrochemical, fluorescent, and SPR. The presented devices' pros and cons and their efficiencies compared with the gold standard methods are reported. Moreover, the application of microfluidic devices to detect Alzheimer's disease related biomarkers is summarized and presented. Finally, some challenges with the performance of novel technologies for isolating and detecting exosomal microRNAs are addressed.

Extracellular vesicles and their indispensable roles in pathogenesis and treatment of inflammatory bowel disease: A comprehensive review

Inflammatory bowel disease (IBD) is a global disease with rising incidence worldwide, and its debilitating symptoms and dissatisfactory therapies have brought heavy burdens for patients. Extracellular vesicles (EVs), a heterogeneous population of lipid bilayer membranes containing abundant bioactive molecules, have been indicated to play important roles in the pathogenesis and treatment of many diseases. However, to our knowledge, comprehensive reviews summarizing the various roles of diverse source-derived EVs in the pathogenesis and treatment of IBD are still lacking. This review, not only summarizes the EV characteristics, but also focuses on the multiple roles of diverse EVs in IBD pathogenesis and their treatment potential. In addition, hoping to push forward the research frontiers, we point out several challenges that the researchers are faced, about EVs in current IBD research and future therapeutic applications. We also put forward our prospects on future exploration regarding EVs in IBD treatment, including developing IBD vaccines and paying more attention on apoptotic vesicles. This review is aimed to enrich the knowledge on the indispensable roles of EVs in IBD pathogenesis and treatment, providing ideas and reference for future therapeutic strategy for IBD treatment.

Continuous-flow label-free size fractionation of extracellular vesicles through electrothermal fluid rolls and dielectrophoresis synergistically integrated in a microfluidic device

Extracellular vesicles (EVs) are cell-derived bioparticles that play significant roles in various biological processes including cell-to-cell communication and intercellular delivery. Additionally, they hold great potential as liquid biopsy biomarkers for pre-diagnostic applications. However, the isolation of EV subpopulations, especially exosomes from a biological fluid remains a challenge due to their submicron range. Here, we demonstrate continuous-flow label-free size fractionation of EVs for the first time through a synergistic combination of electrothermal fluid rolls and dielectrophoresis in a microfluidic device. The device features three dimensional microelectrodes with unique sidewall contours that give rise to effective electrothermal fluid rolls in cooperation with dielectrophoretic forces for the electrokinetic manipulation and size separation of submicron particles. We first validate the device functionality by separating submicron polystyrene particles from binary mixtures with a cut-off size of ∼200 nm and then isolate intact exosomes from cell culture medium or blood serum with a high recovery rate and purity (∼80%). The device operation in a high-conductivity medium renders the method ideal for the purification of target bioparticles directly from physiological fluids, and may offer a robust and versatile platform for EV related diagnostic applications.

A double tangential flow filtration-based microfluidic device for highly efficient separation and enrichment of exosomes

Recently, exosomes have been recognized as important disease biomarkers due to the essential roles they played in disease development. Nevertheless, the highly efficient isolation and enrichment of exosomes from complex body fluids continues to hinder the research and application of exosomes for clinical use. In this work, we developed a double tangential flow filtration-based microfluidic device for exosome isolation from cell supernatants and human serum. The microfluidic device contained two modules. Each module included two polymethylmethacrylate (PMMA) plates with symmetrical serpentine channels and a nanoporous membrane with 200 nm or 30 nm pore diameter and was used to separate larger vesicles, exosomes and free biomolecules. The design of double tangential flow filtration in symmetrical serpentine channels largely increased the contact area between the filtrate and the nanoporous membranes, thus improved the separation efficiency and prevented the clogging of the membrane. Compared with standard separation method, i.e. ultracentrifugation (UC), the microfluidic chip-based separation (Chip) of exosomes showed the advantages of much lower instrumental cost, lower consumable cost, shorter time (<120 min), higher purity (82.8%) and significantly higher recovery rate (77.8%). In addition, due to the label-free separation, the microfluidic device-collected exosomes could be directly used for downstream analysis such as proteomics analysis. The proteomics analysis results of exosomes isolated from the sera of clinical patients with different diseases by the chip revealed richer disease-related information comparing with those exosomes isolated by UC, demonstrating the good practicability of this chip for future clinical research and applications.

Recent microfluidic advances in submicron to nanoparticle manipulation and separation

Manipulation and separation of submicron and nanoparticles are indispensable in many chemical, biological, medical, and environmental applications. Conventional technologies such as ultracentrifugation, ultrafiltration, size exclusion chromatography, precipitation and immunoaffinity capture are limited by high cost, low resolution, low purity or the risk of damage to biological particles. Microfluidics can accurately control fluid flow in channels with dimensions of tens of micrometres. Rapid microfluidics advancement has enabled precise sorting and isolating of nanoparticles with better resolution and efficiency than conventional technologies. This paper comprehensively studies the latest progress in microfluidic technology for submicron and nanoparticle manipulation. We first summarise the principles of the traditional techniques for manipulating nanoparticles. Following the classification of microfluidic techniques as active, passive, and hybrid approaches, we elaborate on the physics, device design, working mechanism and applications of each technique. We also compare the merits and demerits of different microfluidic techniques and benchmark them with conventional technologies. Concurrently, we summarise seven standard post-separation detection techniques for nanoparticles. Finally, we discuss current challenges and future perspectives on microfluidic technology for nanoparticle manipulation and separation.

Mesenchymal stem cell-derived extracellular vesicles/exosome: A promising therapeutic strategy for intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is the second largest type of stroke with high mortality and morbidity. The vast majority of survivors suffer from serious neurological defects. Despite the well-established etiology and diagnose, there is still some controversy over the ideal treatment strategy. MSC-based therapy has become an attractive and promising strategy for the treatment of ICH through immune regulation and tissue regeneration. However, accumulating studies have revealed that MSC-based therapeutic effects are mainly attributed to the paracrine properties of MSC, especially small extracellular vesicles/exosome (EVs/exo) which are considered to be the key mediators of the protective efficacy from MSCs. Moreover, some papers reported that MSC-EVs/exo have better therapeutic effects than MSCs. Therefore, EVs/exo has become a new choice for the treatment of ICH stroke in recent years. In this review, we mainly concentrate on the current research progress on the use of MSC-EVs/exo in the treatment of ICH and the existing challenges in their transplation from lab to clinical practice.

Micro-structure and tensile properties of microfluidic spinning konjac glucomannan and sodium alginate composite bio-fibers regulated by shear and elongational flow: experiment and multi-scale simulation

Microfluidic spinning has been widely used to produce bio-fibers with excellent tensile performances by regulating the conformation of biological macromolecules. However, the effect of channel shapes on fiber tensile performances is unclear. In this study, bio-fibers were prepared using konjac glucomannan and sodium alginate by five channels. The micro-morphology and tensile performance of fibers were characterized and measured. Then, the dynamical behaviours of macromolecule clusters in flow fields were simulated by multi-scale numerical methods. The results show that the elongational flow with increasing extension rates produced fibers with a tensile strength of 32.34 MPa and a tensile strain of 18.72 %, which were 1.37 and 1.55 times that for a shear flow, respectively. The difference in tensile performances was attributed to the micro-morphology regulated by flow fields. The continuously increasing extension rate of flow was more effective than the shear rate or the maximum extension rate for the stretching of macromolecule clusters. We conclude that the channel shapes significantly influence flow fields, dynamical behaviours of molecule clusters, the morphology of fibers, and tensile performances. This study provides a novel numerical method and understanding of microfluidic spinning, which will promote the optimization and applications of bio-fibers.

Research Development on Exosome Separation Technology

Exosomes are special extracellular vesicles secreted by cells, which are of great significance in the basic research of life science and clinical application and has become a hot research field with rapid development in recent 10 years. Therefore, the isolation and separation of exosomes is particularly important for the research and application of exosomes. This paper aims to review the research progress of exosome isolation and separation methods in recent years, including ultracentrifugation, ultrafiltration, size‑exclusion chromatography, precipitation, immunomagnetic bead capture method, aptamer-based isolation, and isolation methods based on microfluidic technology. It is generally accepted that most of the existing methods have limitations, for example, ultracentrifugation is time-consuming and laborious, and immunomagnetic bead capture method and aptamer-based separation method have small sample processing capacity and high cost. As a result, we also introduce some common situations in which two or more methods are combined for use. Finally, the separation and isolation methods including all those presented in this review were compared and summarized.

Microfluidic Separation and Enrichment of Escherichia coli by Size Using Viscoelastic Flows

Here, we achieve the separation and enrichment of Escherichia coli clusters from its singlets in a viscoelastic microfluidic device. E. coli, an important prokaryotic model organism and a widely used microbial factory, can aggregate in clusters, leading to biofilm development that can be detrimental to human health and industrial processes. The ability to obtain high-purity populations of E. coli clusters is of significance for biological, biomedical, and industrial applications. In this study, polystyrene particles of two different sizes, 1 and 4.8 μm, are used to mimic E. coli singlets and clusters, respectively. Experimental results show that particles migrate toward the channel center in a size-dependent manner, due to the combined effects of inertial and elastic forces; 4.8 and 1 μm particles are found to have lateral equilibrium positions closer to the channel centerline and sidewalls, respectively. The size-dependent separation performance of the microdevice is demonstrated to be affected by three main factors: channel length, the ratio of sheath to sample flow rate, and poly(ethylene oxide) (PEO) concentration. Further, the separation of E. coli singlets and clusters is achieved at the outlets, and the separation efficiency is evaluated in terms of purity and enrichment factor.

Exosomes: The Role in Tumor Tolerance and the Potential Strategy for Tumor Therapy

Drug and radiotherapy resistance is the primary cause of treatment failure and poor prognosis in patients with tumors. Exosomes are extracellular vesicles loaded with substances such as nucleic acids, lipids, and proteins that transmit information between cells. Studies have found that exosomes are involved in tumor therapy resistance through drug efflux, promotion of drug resistance phenotypes, delivery of drug-resistance-related molecules, and regulation of anti-tumor immune responses. Based on their low immunogenicity and high biocompatibility, exosomes have been shown to reduce tumor therapy resistance by loading nucleic acids, proteins, and drugs inside xosomes or expressing tumor-specific antigens, target peptides, and monoclonal antibodies on their phospholipid bimolecular membranes. Consequently, future research on genetically engineered exosomes is expected to eliminate resistance to tumor treatment, improving the overall prognosis of patients with tumors.

Exosome-mediated regulatory mechanisms in skeletal muscle: a narrative review

Skeletal muscle plays a paramount role in physical activity, metabolism, and energy balance, while its homeostasis is being challenged by multiple unfavorable factors such as injury, aging, or obesity. Exosomes, a subset of extracellular vesicles, are now recognized as essential mediators of intercellular communication, holding great clinical potential in the treatment of skeletal muscle diseases. Herein, we outline the recent research progress in exosomal isolation, characterization, and mechanism of action, and emphatically discuss current advances in exosomes derived from multiple organs and tissues, and engineered exosomes regarding the regulation of physiological and pathological development of skeletal muscle. These remarkable advances expand our understanding of myogenesis and muscle diseases. Meanwhile, the engineered exosome, as an endogenous nanocarrier combined with advanced design methodologies of biomolecules, will help to open up innovative therapeutic perspectives for the treatment of muscle diseases.

Recent developments in isolating methods for exosomes

Exosomes are the smallest extracellular vesicles that can be released by practically all cell types, and range in size from 30 nm to 150 nm. As the major marker of liquid biopsies, exosomes have great potential for disease diagnosis, therapy, and prognosis. However, their inherent heterogeneity, the complexity of biological fluids, and the presence of nanoscale contaminants make the isolation of exosomes a great challenge. Traditional isolation methods of exosomes are cumbersome and challenging with complex and time-consuming operations. In recent years, the emergence of microfluidic chips, nanolithography, electro-deposition, and other technologies has promoted the combination and innovation of the isolation methods. The application of these methods has brought very considerable benefits to the isolation of exosomes such as ultra-fast, portable integration, and low loss. There are significant functional improvements in isolation yield, isolation purity, and clinical applications. In this review, a series of methods for the isolation of exosomes are summarized, with emphasis on the emerging methods, and in-depth comparison and analysis of each method are provided, including their principles, merits, and demerits.

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.

Rapid separation of bacteria from primary nasal samples using inertial microfluidics

Microbial populations play a crucial role in human health and the development of many diseases. These diseases often arise from the explosive proliferation of opportunistic bacteria, such as those in the nasal cavity. Recently, there have been increases in the prevalence of these opportunistic pathogens displaying antibiotic resistance. Thus, the study of the nasal microbiota and its bacterial diversity is critical in understanding pathogenesis and developing microbial-based therapies for well-known and emerging diseases. However, the isolation and analysis of these populations for clinical study complicates the already challenging task of identifying and profiling potentially harmful bacteria. Existing methods are limited by low sample throughput, expensive labeling, and low recovery of bacteria with ineffective removal of cells and debris. In this study, we propose a novel microfluidic channel with a zigzag configuration for enhanced isolation and detection of bacteria from human clinical nasal swabs. This microfluidic zigzag channel separates the bacteria from epithelial cells and debris by size differential focusing. As such, pure bacterial cell fractions devoid of large contaminating debris or epithelial cells are obtained. DNA sequencing performed on the separated bacteria defines the diversity and species present. This novel method of bacterial separation is simple, robust, rapid, and cost-effective and has the potential to be used for the rapid identification of bacterial cell populations from clinical samples.