Magnetic Bead-based Exosome Extraction: A Technique to Isolate Specific Exosomes from Biofluids

Resuspend a stock solution containing 10 micrograms per milliliter of streptavidin-coated magnetic microparticles, and add 5 microliters of the solution to a microcentrifuge tube containing 495 microliters of PBS. To wash the beads, first, set the tube on a magnetic rack for 1 minute and carefully remove the buffer without disturbing the beads.

Then, transfer the tube to a non-magnetic rack. Add 500 microliters of PBS and pipette to wash the beads. Do this a total of three times. After the final wash, resuspend the beads in 490 microliters of PBS and then add 5 microliters of biotinylated mouse anti-human CD63 antibody from a 1 milligram per milliliter stock solution.

Mix the solution by pipetting. Program a sample rotator for reciprocal rotation at 90 degrees for 5 seconds and vibration at 5 degrees for 1 second. Place the tubes in the rotator and run the program for 30 minutes at room temperature.

Next, transfer the tubes to the magnetic rack for 5 minutes. Wash the beads three times with 500 microliters of PBS and then resuspend them in 490 microliters of PBS containing casein. Label a tube with the sample identification and then add 10 microliters of the sample.

Pipette several times to mix the sample with the antibody-conjugated beads. Next, transfer the tubes to the sample rotator and run the same program for 2 hours at room temperature. Then, wash the beads three times with 500 microlitres of a 1M Tris-Hydrochloride buffer using the magnetized rack. The exosomes are now bound to the magnetized beads.