Figure 4. Angiopep-2 polypeptide-modified and doxorubicin-loaded graphene oxide (ANG-Dox-GO) induces cell apoptosis in U87 MG cells. (A) Cell apoptosis rate of U87 MG cells treated with PBS (control), GO, Dox (30 μg/mL), Dox-GO (containing 30 μg/mL of Dox), and ANG-Dox-GO (containing 30 μg/mL of Dox), respectively, for 24 h by flow cytometry analysis. (B) The expression of apoptosis-related proteins, including Bax, Bid, Bim, cleaved caspase-3, and cleaved caspase-9, in U87 MG cells treated with PBS (control), GO, Dox (30 μg/mL), Dox-GO (containing 30 μg/mL of Dox), and ANG-Dox-GO (containing 30 μg/mL of Dox), respectively, for 24 h by western blotting. *P < 0.05 vs control cells; #P < 0.05 vs Dox; &P < 0.05 vs. Dox-GO.