urine testing for extracellular vesicle isolation using a bilayer microfluidic device

Microfluidic Device for Continuous Extracellular Vesicle Isolation from Human Urine

Extracellular vesicles (EVs) are cell-derived membrane-bound particles comprising two main types: exosomes (30-200 nm) and microvesicles (200-1000 nm)1. Exosomes form through inward budding of the endosomal membrane within a multivesicular body (MVB), releasing intraluminal vesicles (ILVs) into the extracellular space upon fusion with the plasma membrane1. In contrast, microvesicles are generated by outward budding and fission of the cell membrane2. EVs play a crucial role in intercellular communication by transporting proteins, nucleic acids, lipids, and metabolites, reflecting the physiological state of the cell, including growth, angiogenesis, metastasis, proliferation, and therapy resistance3. As a result, they have emerged as promising biomarkers and therapeutic targets for diseases, including cancer, highlighting their potential in diagnostics and drug delivery systems4.
To fully utilize EVs in disease diagnostics and therapeutics, efficient isolation from various biofluids is crucial5.&#160;Common methods include ultracentrifugation (UC), density gradient centrifugation, size exclusion chromatography (SEC), filtration, and immunoisolation6. UC is a widely used technique but may yield particles of similar density that are not EVs and can generate EV aggregates7. SEC has gained popularity due to its ability to provide higher purity samples by excluding particles based on size rather than density8. However, careful selection of the appropriate pore size for the SEC column and optimization of chromatography conditions are essential to minimize co-isolation of unwanted particles like chylomicrons and low-density lipoproteins8. Despite their effectiveness, both methods are time-consuming and challenging to automate, especially for larger volume samples like cell media or urine, limiting their scalability for industrial applications9.
In recent years, asymmetric field flow field fractionation (A4F) has evolved as a powerful separation technique for size and buoyancy-based micro- and nanometer-sized particle separation10. The operational principle of A4F relies on a microfluidic channel endowed with a porous membrane at its base, generating a force exerted towards the membrane called cross-flow10. When combined with Brownian motion and Poiseuille flow inherent to the system, cross-flow facilitates efficient particle separation due to varying particle position within the flow dynamics11. Despite the benefits, this method is limited to sample volumes within the microliter range12 and requires an additional focusing step, extending the duration of the process10.
Over the last decade, microfluidics has gained prominence as a tool for rapid, efficient, and clinically reliable EV separation13. However, most microfluidic methods designed for EV separation are optimized for small-volume, high-concentration EV samples or depend on complex separation procedures14. Furthermore, within the field of microfluidics, polydimethylsiloxane (PDMS) is recognized as the golden standard material owing to its optical transparency, biocompatibility, and ease of use15. Nevertheless, its known propensity to absorb small lipophilic molecules, including EVs, can be problematic for its application in the EV field13.
Cyclic olefin copolymer (COC) is a frequently used material in microfluidics due to biocompatibility, small absorption of molecules, and high chemical resistance15. However, the fabrication of COC devices often involves complex processes or specialized equipment16. Alternatively, off-stoichiometry thiol-ene (OSTE) is a promising alternative to PDMS due to decreased absorption of small molecules, superior chemical stability, ease of fabrication, and scalable fabrication process17,18. However, due to complex connections to tubing, devices can be prone to leaking19.
The aim of this study was to engineer and fabricate a microfluidic device combining OSTE and COC and bifurcated A4F principle for EV separation from large-volume samples such as urine or cell media.

Author Spotlight: Asymmetric Field Flow Fractionation for Bioreactor Integration

Single Step Isolation of Extracellular Vesicles from Large-Volume Samples with a Bifurcated A4F Microfluidic Device

We see the potential of extracellular vesicles, but also recognize the difficulty in their isolation, especially from large sample biofluids such as bioreactor media. In this research we tested if we can use asymmetrical flow field-flow fractionation to isolate extracellular vesicles. As of now, isolating extracellular vesicles directly from biofluids in a continuous flow for integration into bioreactors is impossible.Instead, biofluids must be first collected and processed, adding variability and labor. Our device designed for extracellular vesicle isolation from large volume biofluids enables integration with bioreactors for continuous flow and automation. We found liquid viscosity might impact extracellular vesicles isolation using asymmetric field flow fractionation.We're exploring if adapting biofluid and buffer flows to viscosity can enhance isolation.

Urine Testing for Extracellular Vesicle Isolation Using a Bilayer Microfluidic Device

urine-testing-for-extracellular-vesicle-isolation-using-bilayer

Research

JoVE Journal

Bioengineering

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