Characterisation of exosome from maternal circulation. Exosome were isolated from women uncomplicated pregnancies during first trimester by differential and buoyant density centrifugation (see Methods). (A) Flow chart for the exosome purification procedure based on differential ultracentrifugation. (B) Representative particles size distribution of microsomal fraction. (C) Flow chart for the exosome purification procedure based on sucrose continuous gradient (exosome enriched fractions in yellow 4–7). (D) Representative particles size distribution of enriched exosomal fractions (fraction 4–7 were mixed). Insert: Representative electron micrograph exosome fractions (pooled enriched exosome population from fractions 4 to 7), Scale bar 200 nm.