Direct isolation of small extracellular vesicles from human blood using viscoelastic microfluidics

Small extracellular vesicles (sEVs; <200 nm) that contain lipids, nucleic acids, and proteins are considered promising biomarkers for a wide variety of diseases. Conventional methods for sEV isolation from blood are incompatible with routine clinical workflows, significantly hampering the utilization of blood-derived sEVs in clinical settings. Researchers at ETH Zürich have developed a simple, viscoelastic-based microfluidic platform for label-free isolation of sEVs from human blood. The separation performance of the device is assessed by isolating fluorescent sEVs from whole blood, demonstrating purities and recovery rates of over 97 and 87%, respectively. Significantly, this viscoelastic-based microfluidic method also provides for a remarkable increase in sEV yield compared to gold-standard ultracentrifugation, with proteomic profiles of blood-derived sEVs purified by both methods showing similar protein compositions. To demonstrate the clinical utility of the approach, the researchers isolate sEVs from blood samples of 20 patients with cancer and 20 healthy donors, demonstrating that elevated sEV concentrations can be observed in blood derived from patients with cancer.

Schematic illustration of the viscoelastic microfluidic system
for sEV separation from whole blood

(A) The microfluidic device consists of two sequential modules: a cell-depletion module and an sEV-isolation module. Blood components larger than 1 μm, including WBCs, RBCs, and PLTs, are first removed from outlet O1 in the cell-depletion module, and, subsequently, the cell-free blood sample flows downstream into the sEV-isolation module, where lEVs and mEVs are collected from outlet O2, while sEVs are collected from outlet O3. (B) Images of size-based particle separations in each isolation module. The bright-field image shows the separation of 1 μm from 3-, 7-, and 12-μm particles in the cell-depletion module. The 3-, 7-, and 12-μm particles are focused along the centerline and exit through the waste outlet O1, whereas 1-μm particles are located near the sidewalls, flowing downstream into the sEV-isolation module. The fluorescence image is a composite image of 1-μm (red)–, 500-nm (yellow)–, and 100-nm (blue)–sized particle trajectories in the sEV-isolation module. The 1-μm and 500-nm particles are collected at outlet O2, while the 100-nm particles are collected at the outlet O3. Scale bars, 100 μm.
Meng Y, Zhang Y, Bühler M, Wang S, Asghari M, Stürchler A, Mateescu B, Weiss T, Stavrakis S, deMello AJ. (2023) Direct isolation of small extracellular vesicles from human blood using viscoelastic microfluidics. Sci Adv 9(40):eadi5296. [article]

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