Ultrasound-activated piezoelectric BZT Nanocubes mediate direct Piezocatalytic killing and reverse immunosuppressive tumor microenvironment for effective hepatocellular carcinoma therapy

Background: The pursuit of novel non-invasive strategies for Cancer therapy, particularly those capable of modulating the immunosuppressive tumor microenvironment (TME), is a significant focus in oncology research. Piezoelectric Materials, which can generate electrical signals and Reactive Oxygen Species (ROS) under mechanical stimulation, represent a promising platform for biomedical applications.

Objective: This study aimed to synthesize and evaluate the antitumor efficacy of piezoelectric Ba(Zr₀.₂₅Ti₀.₇₅)O₃ (BZT) nanocubes activated by ultrasound (US) both in vitro and in vivo, and to elucidate the underlying immunomodulatory mechanisms.

Methods: BZT nanocubes with a pure perovskite structure were synthesized via a hydrothermal route method and characterized by XRD, SEM, TEM, and XPS. The piezoelectric catalytic activity for ROS generation was confirmed by methylene blue degradation. The antitumor effects were assessed on hepatocellular carcinoma (HCC) organoids, cell lines (Huh7, Hepa1-6), and an orthotopic mouse model. Cellular proliferation, Apoptosis, migration, and viability were evaluated using Ki-67/PCNA staining, TUNEL, EdU, scratch, and CCK-8 assays. Immune cell infiltration and polarization in the TME were analyzed by immunofluorescence and flow cytometry. The mechanistic role of calcium-NF-κB signaling in macrophage polarization was investigated using RNA Sequencing, western blotting, and specific inhibitors.

Key results: US-activated BZT generated a significant piezoelectric current (7.5 nA) and ROS, leading to Apoptosis in HCC cells. In the orthotopic mouse model, US+BZT treatment markedly inhibited tumor growth. Crucially, it reprogrammed the immunosuppressive TME by increasing the infiltration and cytotoxicity of CD8⁺ T cells and driving the repolarization of macrophages from the M2 to the M1 phenotype. In vitro experiments confirmed that the US+BZT-induced M1 polarization enhanced macrophage phagocytosis and CD8⁺ T cell activation. Mechanistically, the effect was mediated by US-induced piezoelectric activation of BZT, which triggered calcium influx via TRP channels, subsequently activating the PKC-IKK-NF-κB signaling axis.

Conclusion: Our findings demonstrate that US-activated piezoelectric BZT nanocubes exert potent antitumor effects through direct piezoelectric catalysis and, more importantly, through the remodeling of the TME via the calcium/NF-κB pathway. This study highlights the great potential of piezoelectric nanomaterials as a multifaceted and immunomodulatory strategy for Cancer therapy.

BZT; Hepatocellular carcinoma; Immunotherapy; Macrophage polarization; Piezoelectric nanomaterial; Tumor microenvironment.