Objective To explore the effects of polyethylene glycol-2-methoxyestradiol(PEG-2ME2/2ME2)nanoparticles on cerebral vascular endothelial RBE4 cells after oxygen glucose deprivation/reperfusion(OGD/R).Methods To construct the PEG-2ME2/2ME2 nanoparticles by solvent evaporation method,and the characterization of nanoparticles was detected by transmission electron microscope(TEM)and laser particle size analyzer;the cellular cytotoxicity of PEG-2ME2/2ME2 nanoparticles was detected by CCK-8.Using OGD/R to simulate the process of ischemia-reperfusion in vitro,to detect the cell activity by CCK-8;Western blot and immu-nofluorescence were used to detect the expression of tight junction proteins,and the barrier function of cerebrovascular endothelial cells was comprehensively evaluated by establishing blood-brain barrier(BBB)model in vitro and measuring fluorescence probe leakage;re-active oxygen species(ROS)probe was used to detect the ROS level of RBE4 cells,and Western blot was used to detect superoxide dis-mutase to identify the redox status of RBE4 cells.Results The results of TEM showed that the spherical morphology of PEG-2ME2/2ME2 nanoparticles was stable,and the results of laser particle size analyzer showed that the size of PEG-2ME2/2ME2 nanoparticles was uniform;the results of CCK-8 assay showed that the PEG-2ME2/2ME2 nanoparticles had no significant cytotoxicity to RBE4 cells with-in 5μmol/L of 2ME2;the results of CCK-8 assay showed that PEG-2ME2/2ME2 nanoparticles rescued the cellular activity of RBE4 cells after OGD/R compared to the 2ME2 alone,inhibited the downregulation of tight junction protein expression,and effectively restored the barrier function of cerebral vascular endothelial cells;the detection results of ROS probe and Western blot showed that PEG-2ME2/2ME2 nanoparticles reduced intracellular ROS levels,restored the expression of superoxide dismutase compared to the 2ME2 alone.Conclusion PEG-2ME2/2ME2 nanoparticles have uniform size and stable morphology,which can protect RBE4 cells against OGD/R,effectively restore the integrity and barrier function of the blood-brain barrier.The PEG-2ME2/2ME2 nanoparticles are expected to be-come potential drugs for the treatment of cerebrovascular endothelial barrier injury after OGD/R.

Blocking the programmed death-ligand 1 (PD-L1) on tumor cells with monoclonal antibody therapy has emerged as powerful weapon in cancer immunotherapy. However, only a minority of patients presented immune responses in clinical trials. To develop an alternative treatment method based on immune checkpoint blockade, we designed a novel and efficient CRISPR-Cas9 genome editing system delivered by cationic copolymer aPBAE to downregulate PD-L1 expression on tumor cells specifically knocking out Cyclin-dependent kinase 5 () gene . The expression of PD-L1 on tumor cells was significantly attenuated by knocking out , leading to effective tumor growth inhibition in murine melanoma and lung metastasis suppression in triple-negative breast cancer. Importantly, we demonstrated that aPBAE/Cas9-Cdk5 treatment elicited strong T cell-mediated immune responses in tumor microenvironment that the population of CD8 T cells was significantly increased while regulatory T cells (Tregs) was decreased. It may be the first case to exhibit direct PD-L1 downregulation CRISPR-Cas9 genome editing technology for cancer therapy. It will provide promising strategy for preclinical antitumor treatment through the combination of nanotechnology and genome engineering.