Purification and Characterization of Exosomes

ISOLATION OF EXOSOMES

1. Preparing Exosome Collection Media

• Preparing exosome collection media requires careful attention to ensure that the medium is suitable for the isolation and collection of exosomes.
• To prepare exosome collection media, use a standard cell culture medium supplemented with 10% exosome-depleted FBS, which can be obtained by ultracentrifugation and filtration. Ensure sterility by filtering the media through a 0.22 µm filter, and store it at 4°C.

2. Pre-Centrifugation

• Purpose: To remove cell debris, dead cells, and larger vesicles.
• Procedure: Centrifuge the sample at low speed (300-2,000 × g) for 10-20 minutes at 4°C. This step is followed by another centrifugation at a higher speed (10,000-20,000 × g) for 20-30 minutes to remove larger vesicles like apoptotic bodies.

3. Ultracentrifugation (or Alternative Methods)

• Purpose: To pellet the exosomes.
• Procedure:
  Ultracentrifugation: Centrifuge the sample at 100,000-120,000 × g for 70-120 minutes at 4°C. This step is repeated to wash the pellet, typically using PBS.
  Alternative Methods
  Size Exclusion Chromatography (SEC): Separates exosomes based on size.
  Ion Exchange Chromatography membranes: Separates exosomes based on surface charge.
  Ultrafiltration: Uses membranes with specific pore sizes to filter out exosomes.
  Immunoaffinity EV capture: Latex or magnetic Immunobeads (EV-IBeads) and ELISA immunoplates (EV-IPlates) for total or specific EV immunocapture.