CLDN5 and central nervous system cancer: To evaluate the uptake mechanism of GENs into C6 glioma cells through the BBB, BCECs seeded on a transwell membrane were treated for 6 h with a series of inhibitors including chlorpromazine (an inhibitor of clathrin-mediated endocytosis), cytochalasin D (a phagocytosis inhibitor), methyl-β-cyclodextrin (lipid raft disruptor), colchicine (pinocytosis and phagocytosis inhibitor), and antibodies for occludin and claudin-5 (paracellular transport inhibitors) (Additional file 1: Fig. S4).