Anti-PD-L1 biomimetic nanobubbles for ultrasound-triggered reprogramming of cold hepatocellular carcinoma for immunotherapy.

Hepatocellular carcinoma exhibits profound resistance to immune checkpoint blockade due to its dense stromal architecture and immunosuppressive tumor microenvironment with an immune-excluded phenotype. To overcome this therapeutic challenge, we developed PD-1-displaying biomimetic nanobubbles (NB@CM-H-PD-1) that orchestrate a trimodal strategy combining PD-L1-targeted checkpoint blockade, sonodynamic therapy, and acoustic cavitation-mediated stromal remodeling to transform immunologically "cold" HCC into an immune-responsive state. These engineered nanobubbles comprise a perfluorocarbon core, a lipid-bilayer shell embedded with hematoporphyrin monomethyl ether, and an outer coating of cell membranes derived from PD-1-overexpressing cells. The platform executes a synchronized cascade: membrane-displayed PD-1 mediates tumor-specific targeting while providing checkpoint inhibition; sonosensitizer activation generates reactive oxygen species (ROS) triggering immunogenic cell death; and ultrasound-targeted nanobubble destruction enhances intratumoral penetration through cavitation-induced stromal disruption. In vitro characterization demonstrated that NB@CM-H-PD-1 maintained excellent biocompatibility under physiological conditions while exhibiting potent ultrasound-triggered ROS production and cytotoxic activity. In both subcutaneous and metastatic HCC models, this approach achieved near-complete tumor eradication without systemic toxicity. Comprehensive immunological analyses revealed robust immunogenic cell death induction, dendritic cells (DCs) maturation, enhanced T-cell infiltration with increased IFN-γ secretion, and tumor microenvironment reprogramming that initiated systemic antitumor immunity controlling both primary and metastatic lesions. Thus, our findings establish this biomimetic platform as an effective mechano-chemical-immune synergistic actuator for sensitizing refractory HCC to immunotherapy.