Targeted Nanobubbles of PD-L1 mAb Combined with Doxorubicin as a Synergistic Tumor Repressor in Hepatocarcinoma

In summary, ultrasound-mediated PD-L1 mAb/DOX-NBs showed significant synergistic antitumor effects, providing a potential combined immunotherapy strategy for HCC.

The PD-L1 mAb/DOX NBs, using bridging affinity biotin (BRAB) technology as a bridge, were prepared by thin-film hydration and mechanical oscillation for the targeted delivery of biotinylated PD-L1 mAb and DOX. Characterization and pharmacokinetic studies of PD-L1 mAb/DOX NBs were performed in vitro and in vivo. The antitumor effect of ultrasound-mediated PD-L1 mAb/DOX-NBs was studied in the subcutaneously transplanted tumor of the H22 hepatoma model, and the mechanism of synergistic tumor repression was investigated.

Ultrasound nanobubbles (NBs) can kill tumor cells, mediated by their effects of cavitation and acoustic perforation through ultrasound, while as novel drug carriers, biomaterial-modified NBs release drugs at a target region. In this work, the ultrasound NBs bridged by biotin-streptavidin were prepared simultaneously to be loaded with both programmed death ligand 1 monoclonal antibody (PD-L1 mAb) and doxorubicin (DOX), which are immune checkpoint inhibitors (ICIs) and chemotherapeutic agents, to synergize immunotherapy and chemotherapy combined with sonodynamic therapy (SDT).

The data of in vitro targeting experiments, contrast-enhanced ultrasound imaging (CEUS), in vivo imaging of the small animals imaging system (IVIS), and frozen sections showed that PD-L1 mAb/DOX-NBs have well-targeted aggregation in the tumor. By observing tumor inhibition rate, tissue cell apoptosis, and apoptosis-related gene and protein expression, the PD-L1 mAb/DOX-NBs group showed the best immunotherapy effects, and its tumor volume and mass inhibition rates were about 69.64% and 75.97%, respectively (P < 0.01). Therefore, blocking the PD-1/PD-L1 pathway could improve immune cells' tumor-killing ability. Antitumor immune cytokines were further enhanced when combined with DOX-induced tumor cell apoptosis and immunogenic cell death (ICD).