Fig. 3

Transwell polyester membrane filters containing 400 nm-sized pores form a physical barrier that significantly reduces transfer of exosomes in the transwell assay. a Cryo-transmission electron microscopic (TEM) examination of exosomal transfer across a transwell assay membrane filter. TEM was performed on exosomes isolated in open culture wells (positive control, left) and the bottom transwell chamber (right) after 48 h of culture in serum-free media using the modifications described. b Quantification of exosomes transmitted to the bottom well of transwell chamber experiments, compared to exosomes in the open culture control. Exosomes were counted from 3 representative images per experiment and averaged. The relative reduction of exosomal trafficking using this transwell filter was ~ 80%, when assessed by using this method. c Nanoparticle tracking analysis of exosomes from above mentioned transwell and open culture experiments, quantifying the relative reduction at 66%. For statistical analysis, Student’s t-test was conducted, with a p-value of ≤0.05