CLDN5 and glioblastoma: Expression levels of ZO-1 and claudin-5 in hCMEC/D3 monolayers after treatment with HM-NPs and CM-NPs for 48 h were markedly lower than that mediated by MM-NPs, naked NPs or PBS (Fig. 4i), indicating that GBM cell membrane may reduce the tightness of tight junction.