Transmission electron microscopy
For transmission electron microscopy (TEM), exosomes were isolated as described and directly fixed in 200 μl of 2% paraformaldehyde. Exosome preparations (20 μl) were allowed to adsorb in a 75 mesh Formvar/carbon coated grid for 30 min at room temperature. Grids were then washed with PBS (membrane side facing down) and dried using a filter paper. TEM was performed using a Hitachi H-9000 transmission electron microscope at 300 kV, and images were captured using a slow-scan CCD camera.