CD63 is a transmembrane protein of the tetraspanin family commonly found in the membrane of extracellular vesicles, particularly exosomes. It is widely used as a biomarker for EV identification and isolation.

• Four transmembrane domains
• Localized in late endosomes, lysosomes, and exosomes
• Involved in:
  • Vesicle formation and trafficking
  • Protein sorting
  • Cell adhesion and immune modulation

CD63 is often used as a molecular scaffold for displaying functional tags or facilitating selective cargo loading in synthetic or engineered EVs, such as in the E-NoMi system.