CD81 and glioblastoma: The purified EV was confirmed with Western blotting by analyzing the biomarkers of surface tetraspanins (CD63 and CD81), heat shock protein 70 (HSP70), and glyceraldehyde 3-phosphate dehydrogenase (GAPDH), as presented in Figure 2D. The constructed mAb-EV-drug was further evaluated by testing the GBM targeting, toxicity, and anti-tumor cytotoxicity or efficacy in the following studies.