Interest in extracellular vesicles and in particular microvesicles and exosomes, which are constitutively produced by cells, is on the rise for their huge potential as biomarkers in a high number of disorders and pathologies as they are considered as carriers of information among cells, as well as being responsible for the spreading of diseases. Current methods of analysis of microvesicles and exosomes do not fulfill the requirements for their in-depth investigation and the complete exploitation of their diagnostic and prognostic value. Lab-on-chip methods have the potential and capabilities to bridge this gap and the technology is mature enough to provide all the necessary steps for a completely automated analysis of extracellular vesicles in body fluids. In this paper researchers from the CNR NANOTEC Institute of Nanotechnology provide an overview of the biological role of extracellular vesicles, standard biochemical methods of analysis and their limits, and a survey of lab-on-chip methods that are able to meet the needs of a deeper exploitation of these biological entities to drive their use in common clinical practice.
Flow-induced methods for exosomes separation based on Deterministic Lateral Displacement (DLD), Pinched Flow Fractionation (PFF), and viscoelastic microfluidics
(A) Hydrodynamically focused jet in a nano-DLD array first tested to separate polystyrene beads and the corresponding false-colour fluorescence images illustrating the separation process. Scale bar: 10 μm. Application of the chip to real samples (human urine) with a fluorescence-detection scheme. (B) Biological vesicles from cell culture are collected after centrifugation and injected from one inlet of the chip, while the buffer is introduced from the other inlet channel. After separation, exosomes and apoptotic bodies are collected from the outlets and analyzed by immunoblotting assay and TEM. (C) Scheme of the microfluidic chip in which sample and sheath fluids containing low concentration of poly(oxyethylene) (PEO) are introduced from inlet I and inlet II, respectively. Large vesicles are collected at the middle outlet and exosomes at the side outlets because of the elastic forces (Felastic) acting during the flow, as shown in the scheme below.