Several monoclonal antibodies targeting the programmed cell death-1/programmed cell death-ligand 1 (PD-1/PD-L1) pathway have been used successfully in anticancer immunotherapy. Inherent limitations of antibody-based therapies remain, however, and alternative small-molecule inhibitors that can block the PD-1/PD-L1 axis are urgent needed. Herein, we report the discovery of compound 17 as a bifunctional inhibitor of PD-1/PD-L1 interactions. 17 inhibits PD-1/PD-L1 interactions and promotes dimerization, internalization, and degradation of PD-L1. 17 promotes cell-surface PD-L1 internalized into the cytosol and induces the degradation of PD-L1 in tumor cells through a lysosome-dependent pathway. Furthermore, 17 suppresses tumor growth in vivo by activating antitumor immunity. These results demonstrate that 17 targets the PD-1/PD-L1 axis and induces PD-L1 degradation.

Micro/nanostructured TiO2, ion-doped TiO2, and heterojunction TiO2 composite photocatalysts have low toxicity, high biocompatibility, and high photocatalytic and antibacterial activities and have broad applications in the fields of photocatalytic, antibacterial, and orthopedic implants. The photocatalytic and antibacterial activities of TiO2 and TiO2-based photocatalysts depend on their preparation methods. In this review, the preparation methods of TiO2, ion-doped TiO2, and heterojunction TiO2 composite photocatalysts and their effects on photocatalytic and antibacterial activities were reviewed. Based on the excellent physical and chemical properties of TiO2, ion-doped TiO2, and heterojunction TiO2-based photocatalysts, their applications in the field of orthopedic implants were reviewed. Meanwhile, the development trend of the photocatalyst in the fields of photocatalysis, bacteriostasis, and medicine was prospected. The purpose of this review was to point out the direction for further study on photocatalytic and antibacterial activities and related applications of TiO2 and TiO2-based photocatalysts.

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