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Malignant melanoma is a type of highly aggressive tumor, which has a strong ability to metastasize to brain, and 60-70% of patients die from the spread of the tumor into the central nervous system. Exosomes are a type of nano-sized vesicle secreted by most living cells, and accumulated studies have reported that they play crucial roles in brain tumor metastasis, such as breast cancer and lung cancer. However, it is unclear whether exosomes also participate in the brain metastasis of malignant melanoma. Here, we established a human blood-brain barrier (BBB) model by co-culturing human brain microvascular endothelial cells, astrocytes and microglial cells under a biomimetic condition, and used this model to explore the potential roles of exosomes derived from malignant melanoma in modulating BBB integrity. Our findings showed that malignant melanoma-derived exosomes disrupted BBB integrity and induced glial activation on the BBB chip. Transcriptome analyses revealed dys-regulation of autophagy and immune responses following tumor exosome treatment. These studies indicated malignant melanoma cells might modulate BBB integrity via exosomes, and verified the feasibility of a BBB chip as an ideal platform for studies of brain metastasis of tumors in vitro.

Exosomes are membrane-bound nanovesicles that are secreted by most types of cells and contain a range of biologically important molecules, including lipids, proteins, ribonucleic acids, etc. Emerging evidences show that exosomes can affect cells' physiological status by transmitting molecular messages among cells. As such, exosomes are involved in various pathological processes. Studying exosomes is of great importance for understanding their biological functions and relevance to disease diagnosis. However, it is difficult to separate and analyze exosomes due to their small size, and because their density is similar to that of bodily fluids. Traditional methods, including ultracentrifugation and ultrafiltration are time-consuming and require expensive equipment. Other methods for exosome separation, including immunoaffinity-based methods, are expensive and rely heavily on specific antibodies. Precipitation-based methods do not yield acceptable purity for downstream analysis, due to polymer contamination. Thus, urgent demand exists for a portable, simple, affordable method for exosome separation. Microfluidic chip technology offers a potential platform for separation and detection of exosomes, with several remarkable characteristics, including low sample consumption, high throughput, and easy integration. This paper provides an overview of current microfluidic strategies for separation and analysis of circulating exosomes. In our introduction to exosome separation, we divide existing separation methods into two categories. Category one is based on exosome physical properties, and includes membrane filtration, nano-column array sorting, and physical isolation. The other is immune capture, which is based on biochemical characteristics of exosomes, and includes fixed base immune capture and unfixed base immune capture. In our introduction to exosome analyses, some commonly used methods, including western blotting, scanning electron microscopy, and flow cytometry are briefly described. Some new systems, which combine microfluidic technology with fluorescence, electrochemical sensing, surface plasmon resonance, or other multimodal analysis methods for integrated detection of exosomes are then described in detail. Finally, the challenges faced by microfluidic technology in improving exosome purity and making systems more portable are analyzed. Prospects for application of microfluidic chips in this area are also discussed. With the rapid development of micro/nano-manufacturing, new materials, and information technology, microfluidic exosome separation and analysis systems will become smaller, more integrated, and more automated. Microfluidic chip technology will play important roles in exosome separation, biochemical detection, and mechanism analysis.

Tumor-derived exosomes have been recognized as promising biomarkers for early-stage cancer diagnosis, tumor prognosis monitoring and individual medical treatment. However, it is a huge challenge to separate exosomes from trace biological samples in clinics for disease diagnosis. Herein, we propose a simple, quick, and label-free method for isolating circulating exosomes from serum of patients. The strategy synergistically integrates chitosan electrostatic-adsorption, micro-patterned substrates, and microfluidic shuttle flow control to enable the capture/release of circulating exosomes in a simple manner. Using this microchip, we can isolate exosomes from trace samples (10 μl) with relative purity over 90% and high RNA recovery ratio over 84% within 15 minutes, which is impossible for traditional ultracentrifugation methods. We then validate the application of the microchip using 24 serum samples from clinical breast cancer and breast fibroma patients. The isolated exosomes are subjected to miRNA sequencing and RT-PCR, followed by pathway prediction analysis. The results showed that exosomes were relevant to the invasion and metastasis of breast cancer cells and hsa-miR-18a-3p might have the potential to become a new biomarker for distinguishing breast cancer from breast fibroma (AUC = 0.83, P value = 0.019). This established method is simple, quick and easy to operate with integration. And it may pave a new way for clinical research on exosomes and tumor relevant diagnosis.

Tumor-derived circulating exosomes have been recognized as a promising biomarker source for cancer diagnosis via a less invasive procedure. The integration of isolation and detection of exosomes in routine clinical settings is still challenging. In this study, we developed a new microfluidic device for immunomagnetic separation and detection of blood exosomes in situ. The microfluidic device may empower the integration of target exosome analysis via high surface to volume ratios of immunomagnetic beads and highly precise fluid control with the aid of microvalves. The obtained microfluidic device was capable of on-chip isolation and detection of circulating exosomes within 1.5 h. The captured exosomes could be directly visualized with an inverted fluorescence microscope in situ by tetramethylbenzidine-based colorimetric sensing. It was revealed that a statistically significant increase (p < 0.01) in EpCAM-positive exosomes was captured for cancer patients (n = 10) on the device when compared to healthy individuals (n = 10). The device also demonstrated high predicting accuracy for tumor exosomal markers with a sensitivity of 90% and a specificity of >95% using receiver operating characteristic curves. The microfluidic device might provide a new platform to assist cancer diagnosis and molecular classification in an automated and simple fashion. [ABSTRACT FROM AUTHOR]

Arthritis is caused by inflammation, infection, degeneration, trauma, or other factors that affect approximately 250 million people all over the world. Early diagnosis and prediction are essential for treatment. Exosomes are nanoscale vesicles that participate in the process of joint disease. Serum is the mainly used sources in the study of arthritis-related exosomes, while whether serum exosomes can reflect the contents of synovial fluid exosomes is still unknown. In this work, we separated exosomes from serum and the synovial fluid of osteoarthritis patients and compared their miRNA expression utilizing miRNA sequencing. The results revealed that 31 upregulated and 33 downregulated miRNAs were found in synovial fluid compared to serum. Transcriptome analysis showed that these differentially expressed miRNAs were mainly associated with intercellular processes and metabolic pathways. Our results show that serum-derived exosomes cannot fully represent the exosomes of synovial fluid, which may be helpful for the study of joint diseases and the discovery of early diagnostic biomarkers of arthritis. [ABSTRACT FROM AUTHOR]

Breast cancer is one of the most commonly diagnosed malignancies and the leading cause of cancer death in women worldwide. Although many factors associated with breast cancer have been identified, the definite etiology of breast cancer is still unclear. In addition, early diagnosis of breast cancer remains challenging. Exosomes are membrane-bound nanovesicles secreted by most types of cells and contain a series of biologically important molecules, such as lipids, proteins, and miRNAs, etc. Emerging evidence shows that exosomes can affect the status of cells by transmitting substances and messages among cells and are involved in various physiological and pathological processes. In breast cancer, exosomes play a significant role in breast tumorigenesis and progression through transfer miRNAs which can be potential biomarkers for early diagnosis of breast cancer. This review discusses the potential utility of exosomal miRNAs in breast cancer progression such as tumorigenesis, metastasis, immune regulation and drug resistance, and further in breast cancer diagnosis. [ABSTRACT FROM AUTHOR]

Exosomes are membrane-bound nanovesicles secreted by most types of cells, which contain a series of biologically important molecules, such as miRNAs, proteins, and lipids, etc. Emerging evidence show that exosomes can affect the physiological status of cells and are involved in various pathological processes. However, due to their small size and density close to body fluids, it is challenging to separate exosomes from a small volume of biological samples in a simple manner. Herein, we propose a new strategy for isolating circulating exosomes from biological samples in a portable device. This method synergistically integrates chitosan electrostatic-adsorption, scaffold substrates, and shuttle flow to enable the highly effective capture of circulating exosomes with a recovery rate of over 80% within 20 min, which is much better than the performance of traditional ultracentrifugation (5–25%, 3 h). Besides, the isolated exosomes from samples could be lysed in situ and further subjected to RNA concentration detection and protein analysis. In particular, all the necessary procedures for exosome separation could be integrated into a single device without the need for bulky equipment. This established device is portable and easy to operate, which provides a promising platform for the study of exosome biology and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Exosomes are nanoscale membrane vesicles (∼30–150 nm) actively released by most types of cells, which has great potential for non-invasive disease diagnostics. Current isolation techniques such as ultracentrifugation face a number of drawbacks including low integrity, low purity and long processing times. This represents an interesting challenge for microfluidic technologies, from integrity perspective as well as for enhanced purity capabilities, point-of-care acquisition and diagnosis. In this review, we highlight the label-free microfluidic advances for isolation and analysis of exosomes based on their size, deformability and electrical characteristics. These new capabilities are expected to advance fundamental research while paving the way for routine exosome-based personalized medicine. • Microfluidic strategies for label-free exosome isolation and analysis are elucidated. • Integrating exosomes detection on the microfluidic platforms are introduced. • Current challenges to practical concerns for exosome-based fundamental research and disease diagnostics are discussed. [ABSTRACT FROM AUTHOR]