How are exosomes visualized and characterized?

While visualization is not a common requirement when studying exosomes, they may be observed using electron microscopy. Since exosomes are composed of a phospholipid bilayer with membrane proteins, exosomes can be characterized by immunostaining them with anti-membrane protein antibodies, including CD-63, CD-81, CD-9, HSP70, HSP90, MHC Class II, Alix, FlotI, ICAM1, EpCam, ANXA5. Exosomes may be further characterized with markers for specific cells of origin.