2.9. In Vivo Exo and Selu-Exo Targeting to the Parental Tumor

To observe the in vivo targeting effect of exosomes on tumor tissue, DiI-labeled exosomes (DiI-U87 exo, DiI-A549 exo, DiI-U87-Selu exo and DiI-A549-Selu exo; 8–9 µg/µL exosome) were injected intravenously into U87 xenograft mice tail vein with 50 mg exosome/kg dose (n = 5 for each group) (Figure 3). A total of 24 h after injection, the mice were sacrificed by exsanguination from the vena cava for tumor harvesting. The harvested tumors were embedded in optical cutting temperature (OCT) compound. The OCT compound sections were then cut into thicknesses of 8 µm. After the specimens were washed 3 times with TBS (100 mL), the slides were covered with VECTASHIELD mounting medium with DAPI (Vector Laboratories; Catalog No. H-1200). Images of the slide sections were captured using a Nikon fluorescence microscope with the software NIS-Elements BR 5.11 (Nikon). The relative fluorescence intensity was analyzed by ImageJ software (Version 1.50i; US National Institutes of Health, Bethesda, MD, USA).

Overview of the DiI-labelled exosomes (DiI-U87 exo, DiI-U87-Selu exo, DiI-A549 exo and DiI-A549-Selu exo) in vivo targeting experiments.