Simultaneous isolation and preconcentration of exosomes by ion concentration polarization

Abstract

Exosomes carry microRNA biomarkers, occur in higher abundance in cancerous patients than in healthy ones, and because they are present in most biofluids, including blood and urine, these can be obtained noninvasively. Standard laboratory techniques to isolate exosomes are expensive, time consuming, provide poor purity, and recover on the order of 25% of the available exosomes. We present a new microfluidic technique to simultaneously isolate exosomes and preconcentrate them by electrophoresis using a high transverse local electric field generated by ion-depleting ion-selective membrane. We use pressure-driven flow to deliver an exosome sample to a microfluidic chip such that the transverse electric field forces them out of the cross flow and into an agarose gel which filters out unwanted cellular debris while the ion-selective membrane concentrates the exosomes through an enrichment effect. We efficiently isolated exosomes from 1× PBS buffer, cell culture media, and blood serum. Using flow rates from 150 to 200 μL/h and field strengths of 100 V/cm, we consistently captured between 60 and 80% of exosomes from buffer, cell culture media, and blood serum as confirmed by both fluorescence spectroscopy and nanoparticle tracking analysis. Our microfluidic chip maintained this recovery rate for more than 20 min with a concentration factor of 15 for 10 min of isolation.

A review: applications of ion transport in micro‐nanofluidic systems based on ion concentration polarization

“…Marczak et al . demonstrated a novel microfluidic technique that uses ion consumption to simultaneously separate exosomes and preconcentrate them by electrophoresis . By fluorescence spectroscopy and nanoparticle tracking analysis, they efficiently captured 60–80% of exosomes from 1× PBS buffer, cell culture media and serum.…”

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016–2018)

“…Marczak et al. fabricated an ICP preconcentrator for simultaneous isolation and preconcentration of exosomes in biological samples. The microcchannels were fabricated in polycarbonate sheets, and a cation‐exchange membrane was integrated for the ICP.…”

Current‐Induced Ion Concentration Polarization at a Perfect Ion‐Exchange Patch in an Infinite Insulating Wall

“…After the initial Crooks paper, many groups developed ion preconcentration using ion‐ exchange media, including nanopores, between channels in a T‐junction configuration (Figure ) . These devices also exploit the combination of flow with depletion and accumulation regions that exist near the surfaces of ion‐exchange media during current flow . Typically, flow brings ions toward the junction, and they accumulate near regions where their electrophoretic flux component offsets their convective flux component.…”

“…[7] These devices also exploit the combination of flow with depletion and accumulation regions that exist near the surfaces of ion-exchange media during current flow. [8][9][10] Typically, flow brings ions toward the junction, and they accumulate near regions where their electrophoretic flux component offsets their convective flux component. Wang and coworkers reported as much as a million-fold preconcentration factor for proteins.…”