Microfluidics‐based on‐a‐chip systems for isolating and analysing extracellular vesicles

Abstract

Extracellular vesicles (EVs), which can be found in almost all body fluids, consist of a lipid bilayer enclosing proteins and nucleic acids from their cells of origin. EVs can transport their cargo to target cells and have therefore emerged as key players in intercellular communication. Their potential as either diagnostic and prognostic biomarkers or therapeutic drug delivery systems (DDSs) has generated considerable interest in recent years. However, conventional methods used to study EVs still have significant limitations including the time-consuming and low throughput techniques required, while at the same time the demand for better research tools is getting stronger and stronger. In the past few years, microfluidics-based technologies have gradually emerged and have come to play an essential role in the isolation, detection and analysis of EVs. Such technologies have several advantages, including low cost, low sample volumes, high throughput and precision. This review summarizes recent advances in microfluidics-based technologies, compares conventional and microfluidics-based technologies, and includes a brief survey of recent progress towards integrated “on-a-chip” systems. In addition, this review also discusses the potential clinical applications of “on-a-chip” systems, including both “liquid biopsies” for personalized medicine and DDS devices for precision medicine, and then anticipates the possible future participation of cloud-based portable disease diagnosis and monitoring systems, possibly with the participation of artificial intelligence (AI).

Engineering of Exosomes to Target Cancer Metastasis

“…However, exosomes may partly become deformed or broken when they are forced through nanoscale filters. 61 Microfluidic separation Various properties incorporated into microfluidic channels Fast, easy integration with other techniques Limited to small sample volume, requires in-house made microfluidic devices 16,19,32,45,83,99 Size exclusion chromatography (SEC) is a promising method for exosome isolation because of its capability to separate nanoscale particles based on their hydrodynamic size. 57 The SEC column is packed with porous beads so that components with a smaller size have to go through many small pores before being eluted out of the column while larger components can pass the beads faster by avoiding entering the pores.…”

“…45 Microfluidics-based technologies for exosome isolation are typically used for diagnostic purposes due to their high sensitivity but limitation in processed sample volume. 32 Techniques that have been incorporated in microdevices for exosome isolation include immunoaffinity, sieving, and trapping exosomes on porous structures. 19 Similar to the macroscale immunoaffinity-based method for exosome isolation, antibodies can also be immobilized to the surface of the channels in microfluidic devices for microscale isolation of exosomes.…”

Population Analysis of Extracellular Vesicles in Microvolumes of Biofluids

“…by PCR, DNA and RNA sequencing) content. [10][11][12] Despite enabling the characterization of a group of vesicles, these methods lack information on subpopulations and molecular heterogeneity of EVs at a singlevesicle level.…”

“…Technologies based on immunoaffinity capture surfaces and beads, such as ELISA and conventional flow cytometry, have enabled the analysis of populations of EVs expressing specific antigens. 2,11 However, by capturing heterogeneous groups of EVs containing a common molecule of interest or due to resolution limitations, these methods do not allow for single-vesicle analysis of small EVs. [13][14][15] Nanoparticle Tracking Analysis, such as Nanosight, has been used to perform studies of single EVs.…”

Use of Nanosphere Self-Assembly to Pattern Nanoporous Membranes for the Study of Extracellular Vesicles

“…1,19 The preferred methodology for the isolation of small EVs is ultracentrifugation although many others continue to emerge such as membrane based isolation. 4,[20][21][22][23][24][25][26][27][28][29] Additionally, the most commonly used methodology for the study of small EVs in cellular co-culture is the use of commercially available track etched membranes. These membranes are thick rendering them low in permeability and often contain merged pores.…”