The analysis revealed a weak GFP signal (mean fluorescence per particle is 3.78 ± 1.67 (n = 52) and 8.49 ± 2.17 (n = 43) relative fluorescence units (RFU) for VSV-G-pseudotyped and “bald” viruses, respectively), especially compared with CD9-GFP+ EVs (45.59 ± 4.11 RFU, n = 30) produced by engineered melanoma cells (Supplementary Fig. 1a, c, respectively). Here, CD9 is linked to melanoma.