Microfluidic manipulation of extracellular vesicles for mechanical property estimation

Recent discoveries have shown that dilute suspensions of colloidal particles with diameters ranging from 100 nm – 1 µm can be manipulated within microchannels (100 – 300 µm wide x 25-50 µm deep x 2-4 cm long) for a variety of applications. Our group has reported on migration and assembly of polystryrene colloidal particles previously.

Recently, extending our expertise in microfluidics and colloidal particle manipulation, we have evaluated the flow of extracellular vesicles (EVs) from cancer patients and associated tumor cell lines. We have shown that these vesicles can be separated and captured for further analysis from a complex, multi-component fluid. The separation and capture method was implemented on the same hybrid micro-nanofluidic device. The separation occurs through a nanochannel network, often implemented as a membrane bridging two microchannels. Similar to other results, the separation is a mechanical filtration process. As the extracellular vesicles are soft, lipid-covered structures that protect valuable cargo, the mechanical deformation analysis of these vesicles subject to a flow-based filtration was found to be deficient.

In this work we report on a methodology that uses flow through nanochannel membrane networks (diameter of filtration pores is ~ 200 nm) for EVs, classified to two size regimes as small EVs (< 150 nm diameter) and large EVs (> 150 nm) and combines the flow data with high resolution transmission electron microscopy. This combination approach allows quantification of mechanical deformation without damaging EVs or the EV-cargo for estimation of EV mechanical properties. We find that the EV properties estimated with a whole-EV deformation analysis yields results with the estimated modulus of elasticity being < 1 MPa for the specific Sarcoma-relevant EVs evaluated as a model system.