Ultrasound-Activated Nanoplatform Counteracts Triple-Negative Breast Cancer via Remodeling Intratumoral Microbiota–Metabolism and Inducing Ferroptosis

Triple-negative breast cancer (TNBC) remains therapeutically challenging owing to the paucity of broadly effective molecular targets. Piezoelectric nanomaterials that generate localized electric fields and reactive oxygen species under ultrasound (US) stimulation have emerged as a promising strategy for TNBC therapy. Here, we developed a US-activatable nanoplatform (HN-T/BT@Lip) in which toyocamycin-loaded CaCO₃-carboxymethyl chitosan hybrid nanoparticles (HNs) and barium titanate (BaTiO₃, BT) are co-encapsulated in folate-modified liposomes. US-activated HN-T/BT@Lip suppressed tumor growth and induced ferroptosis. Integrated transcriptomic, metabolomic, and microbiota profiling further revealed that this treatment disrupts glutathione metabolism, enhances susceptibility to lipid peroxidation, and perturbs iron homeostasis. These effects were closely associated with shifts in microbial community composition and altered levels of microbiota-derived metabolites. In vitro assays further demonstrated that the microbiota-associated metabolite trimethylamine <i>N</i>-oxide synergistically amplified lipid peroxidation under HN-T/BT@Lip + US treatment. Collectively, our findings demonstrate that US-activated HN-T/BT@Lip elicits potent ferroptosis in TNBC while concomitantly reshaping the intratumoral microbiota-metabolism landscape, and they highlight microbiota-derived metabolites such as trimethylamine <i>N</i>-oxide as potential modulators and biomarkers of nanotherapeutic ferroptosis.