Objective:To prepare the nanodrug paclitaxel dimer(PTX2)-loaded nanoparticles(NPs)using the block copolymer 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-polyethylene glycol 2000,(DSPE-PEG2000),and to explore the killing effect of PTX2 NPs on the human lung cancer A549 cells and its influence on apop to tis.Methods:The PTX2 NPs were prepared using nanoprecipitation method.Dynamic light scattering(DLS)was employed to determine the particle size distribution,and transmission electron microscope(TEM)was used to observe the ultrastructure of the nanoparticles.After treatment of 0 and 10 mmol·L-1 dithiothreitol(DTT),dialysis method was used to evaluate the in vitro drug release profile of PTX2 NPs.The cell counting kit-8(CCK-8)method was used to assess the survival rates of the A549 cells after treated with PTX2 and PTX2 NPs with different concentrations(0.000 1,0.001 0,0.010 0,0.100 0,and 1.000 0 μmol·L-1).The A549 cells were divided into control group,PTX2 group,and PTX2 NPs group.Live/dead staining method was used to detect the survival of the A549 cells in various groups,and flow cytometry was used to detect the apoptotic rates of the A549 cells in various groups.Results:The mean hydrodynamic diameter of PTX2 NPs was determined to be 144.7nmbyDLS.TheTEM imaging confirmed uniform spherical morphology of PTX2 NPs.In a reductive environment,the PTX2 NPs exhibited continuous drug release with total paclitaxel(PTX)release of 84％within 72 h.The results of CCK-8 method showed that both PTX2 and PTX2 NPs inhibited the proliferation of A549 cells in a dose-dependent manner.When the concentrations of PTX＜0.01 μmol·L-1,compared with PTX2 group,the survival rates of A549 cells in PTX2 NPs group were significantly decreased(P＜0.01 or P＜0.001).The live/dead staining results showed that compared with PTX2 group,the number of red fluorescence-labeled dead cells in PTX2 NPs group was increased.The flow cytometry results demonstrated that compared with control group and PTX2 group,the apoptotic rates of the A549 cells in PTX2 NPs group were significantly increased(P＜0.05 orP＜0.01).Conclusion:The PTX2-loaded nanoparticles PTX2 NPs are successfully prepared which exhibits responsive drug release and demonstrates a more significant killing effect on the human lung cancer A549 cells compared to PTX2.

Objective:To prepare the bacterial outer membrane vesicles(OMV)that can express programmed death ligand 1(PD-L1)nanobody on surface,and to discuss its structural characteristics,cell compatibility,intracellular distribution,and its blocking effect on the programmed cell death protein-1(PD-1)/PD-L1 signaling axis.Methods:The pET28a-ClyA-PD-L1nb prokaryotic expression vector was constructed and transformed into Escherichia coli BL21(DE3)competent cells;the OMV was isolated from the BL21(DE3)monoclonal colonies transformed with the PD-L1nb expression vector by ultracentrifugation;the protein purification was performed using the histidine(His)tag;transmission electron microscope and nanoparticle size analyzer were used to analyze and identify the OMV;the OMV isolated from the BL21(DE3)monoclonal colonies transformed with the PD-L1nb expression vector was used as experimental group;the OMV isolated from the untransformed BL21(DE3)monoclonal colonies was used as control group;Western blotting method was used to detect the expression levels of ClyA-PD-L1nb fusion protein in the OMV in two groups;cell counting kit-8(CCK-8)assay was used to detect the activities of mouse macrophage RAW 264.7 cells,mouse triple-negative breast cancer 4T1 cells,and human embryonic kidney HEK293T cells after treated with OMV;fluorescence imaging technology was used to observe the tumor cell endocytosis of OMV;flow cytometry was used to detect the binding effect of OMV to the PD-L1 on surface of the tumor cells in PBS group,OMV-PD-L1nb group,and aPD-L1+OMV-PD-L1nb group.Results:The sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE)results showed that after induction of Escherichia coli,significantly thickened protein bands appeared near the predicted relative molecular mass(about 49 000),and after purification,no obvious impurity proteins existed in the lanes;the OMV-PD-L1nb with a size of about 120 nm was isolated by ultracentrifugation,and it presented a uniform spherical structure under transmission electron microscope;the Western blotting results showed that the specific band of ClyA-PD-L1nb was detected in the OMV in experimental group;the CCK-8 assay results showed that after treated with different concentrations of OMV,the viabilities of the RAW 264.7 cells,4T1 cells,and HEK293T cells were all close to 100％;the fluorescence imaging results showed that OMV-PD-L1nb was endocytosed by 4T1 cells and dispersed in the cytoplasm;compared with OMV-PD-L1nb group,the average fluorescence intensity in the cells in aPD-L1+OMV-PD-L1nb group was significantly decreased(P＜0.001).Conclusion:The OMV surface-displaying PD-L1nb,OMV-PD-L1nb,is successfully prepared and isolated;OMV-PD-L1nb shows good compatibility on mouse macrophage cells,tumor cells,and human embryonic kidney cells,can be endocytosed by tumor cells,and successfully blocks the PD-1/PD-L1 signaling pathway.