Chen Wenwen, Gan Zhongqiao, Qin Jianhua
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Liaoning, 116023, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Se Pu. 2021 Sep;39(9):968-980. doi: 10.3724/SP.J.1123.2021.07005.
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.
外泌体是一种膜结合纳米囊泡，由大多数类型的细胞分泌，包含一系列具有重要生物学意义的分子，如脂质、蛋白质、核糖核酸等。越来越多的证据表明，外泌体可通过在细胞间传递分子信息来影响细胞的生理状态。因此，外泌体参与了各种病理过程。研究外泌体对于理解其生物学功能以及与疾病诊断的相关性具有重要意义。然而，由于外泌体尺寸小且密度与体液相似，难以对其进行分离和分析。传统方法，如超速离心和超滤，耗时且需要昂贵的设备。其他外泌体分离方法，如基于免疫亲和的方法，成本高昂且严重依赖特异性抗体。基于沉淀的方法由于聚合物污染，无法为下游分析提供可接受的纯度。因此，迫切需要一种便携式、简单且经济实惠的外泌体分离方法。微流控芯片技术为外泌体的分离和检测提供了一个潜在平台，具有几个显著特点，包括低样品消耗、高通量和易于集成。本文概述了当前用于循环外泌体分离和分析的微流控策略。在介绍外泌体分离时，我们将现有的分离方法分为两类。第一类基于外泌体的物理性质，包括膜过滤、纳米柱阵列分选和物理分离。另一类是免疫捕获，基于外泌体的生化特性，包括固定基底免疫捕获和非固定基底免疫捕获。在介绍外泌体分析时，简要描述了一些常用方法，如蛋白质印迹法、扫描电子显微镜和流式细胞术。然后详细描述了一些将微流控技术与荧光、电化学传感、表面等离子体共振或其他多模态分析方法相结合用于外泌体综合检测的新系统。最后，分析了微流控技术在提高外泌体纯度和使系统更便携方面面临的挑战。还讨论了微流控芯片在该领域的应用前景。随着微纳制造、新材料和信息技术的快速发展，微流控外泌体分离和分析系统将变得更小巧、更集成、更自动化。微流控芯片技术将在外泌体分离、生化检测和机制分析中发挥重要作用。
