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The science behind Demeter EVPrep

Demeter EVPrep leverages dielectrophoresis and the unique dipole moment of EVs to selectively isolate them from particles of the same size and density in biofluids. No more trading purity for yield.

EVs have fundamentally different structures and composition

Biofluids and culture media are rich in proteins and lipoproteins that can share physical properties with EVs. Common techniques such as ultracentrifugation and size-exclusion chromatography use only density or size to separate EVs, leading to the co-isolation of contaminating material.

While EVs, proteins, and lipoproteins can overlap in size and density, these three groups have fundamentally distinct structures and compositions. EVs are particles with a protein-containing lipid bilayer membrane and an aqueous lumen containing cargo of nucleic acids, proteins and more. Our approach is to isolate EVs based on the electrical properties coming from their unique structure and composition.

Side-by-side comparison of a lipoprotein (about 70–120 nm: lipid core, phospholipid monolayer, apolipoproteins on the surface), a protein (about 100 nm: amino acids, one or more subunits) and an extracellular vesicle (about 50–150 nm: aqueous lumen with cargo, lipid bilayer membrane, proteins on the surface).

EV polarization under dielectrophoresis (DEP)

The lipid bilayer of EVs acts as an insulator to the conductive aqueous lumen. When an electric field is applied, the lipid bilayer causes the unbound charge to redistribute along the surface of the EV, polarizing it and creating a large dipole moment. Under the same conditions, proteins and lipoproteins do not experience the same charge redistribution and thus do not create a strong dipole moment. Therefore, the overall structure and composition, rather than the abundance of specific proteins in EVs, determines the dipole moment.

In a non-uniform electric field, ions travel the surface of an extracellular vesicle around its insulating lipid bilayer, creating a dipole moment. A protein in the same field has no dipole moment.

Polarized EVs are selectively captured

As the sample flows across the electrode array, polarized EVs are drawn to the electrode edges and held in place and other non-polarized proteins are washed away.

Sample flows left to right across an electrode array. Polarized EVs are drawn to the edges of the alternating negative and positive electrodes and held in place, while non-polarized proteins flow past.

Fully automated DEP isolation of EVs in 3 steps

1 ·

Polarize

EV-specific electric settings induce a large dipole moment in EVs.

2 ·

Capture & Wash

EVs are held at the electrodes while non-polarized proteins are washed away.

3 ·

Elute

Field off. EVs released into a small volume, concentrated and label-free.

Demeter EVPrep instrument with touchscreen and barcode scanner

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