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.

Sphincter of Oddi dysfunction (SOD) refers to the abnormal physiological function of sphincter of Oddi, which causes a series of syndromes in biliary tract, pancreas and liver. At present, the related research of SOD is becoming a hot spot, but its pathogenesis is not clear. This article will review the domestic and international literatures on SOD, review the advantages and disadvantages of experimental animals such as rabbits, dogs and guinea pigs, and analyze the characteristics of drugs and surgical modeling, so as to provide references for future related model establishment.