Characterisation of exosomes derived from human cells by nanoparticle tracking analysis and scanning electron microscopy

[Display omitted] ► Exosomes from three different cell lines had a diameter of 110 nm. ► Ultracentrifugation does not change size or shape of exosomes. ► Multiple shock-freezing and thawing does not affect the exosomes. ► Storage at 4 °C and 37 °C in dispersion leads to slow degradation of exosomes. ► Nanoparticle tracking analysis is well suited to study exosomes. Exosomes from three different cell types (HEK 293T, ECFC, MSC) were characterised by scanning electron microscopy (SEM), dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA). The diameter was around 110 nm for the three cell types. The stability of exosomes was examined during storage at −20 °C, 4 °C, and 37 °C. The size of the exosomes decreased at 4 °C and 37 °C, indicating a structural change or degradation. Multiple freezing to −20 °C and thawing did not affect the exosome size. Multiple ultracentrifugation also did not change the exosome size.