Fig. 2

Cationic polymers affect the biophysical properties of EV suspensions and result in precipitation of the nanoparticles. Metastatic melanoma derived EVs obtained by ultracentrifugation were incubated with or without 4 μg/ml or 8 μg/ml Polybrene (PB) or 4 μg/ml or 8 μg/ml Poly-l-lysine (PL). A Zeta Potential and Hydrodynamic diameter by Dynamic Ligh Scattering (DLS). EVs were incubated either 5 min or 18 h with the polymers and analysed using a DLS instrument. Data on Zeta Potential and Intensity Mean (average diameter in nm.) are depicted. Mean and Standard Deviation from three independent experiments is shown. Statistical analysis was performed by a one-way ANOVA Fisher’s LSD test (p < 0.05). *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001). B Analytical ultracentrifugation. The sedimentation coefficient of EVs was analysed either directly after ultracentrifugation (ultra) or after further purification by size exclusion chromatography (SEC). The graph represents data on the weight (signal) average sedimentation coefficient obtained after a 18 h-incubation with polymers of EVs obtained under these two methods. C Transmission Electron Microscopy. The left column shows the general aspect of the grid, followed by sequential magnifications [Bar: 2 µm (2nd column), 0.5 µm (3rd and 4th columns)]. Polymers caused precipitation of EV samples, affecting the integrity of the resin upon electron beam incidence. Thus, pictures from Poly-l-Lysine treated samples could not be obtained at high magnification. Electron dense areas correspond to EV aggregates