Fig. 4.

Characteristics of exosomes isolated from human plasma. (a) A representative Western blot of exosomes isolated from plasma of a normal control (NC) and floated on a continuous sucrose gradient following ultracentrifugation. Individual 1-ml fractions were collected and loaded on gels for electrophoresis. Exosomes expressing CD81 are located in fractions 6 and 7. (b) Transmission electron microscopy of exosomes collected from the sucrose gradient shown in (a) as fraction 6. Negative stain with uranyl acetate. (c) Exosomes in fraction 6 were examined in a NanoSight instrument to determine their size and particle concentration.