Polarization Engineering and Chemical Bond Reconstruction in Rare-Earth Hexagonal Manganite via Fe ³⁺ -Occupied B-Site Doping for Piezocatalytic Therapy and Ferroptosis

Piezocatalytic therapy has emerged as a noninvasive therapeutic strategy. However, its therapeutic effect is limited by the low separation efficiency of carriers (electrons and holes) in piezoelectric materials. Rare-earth hexagonal manganite materials might be good candidates for efficient piezocatalytic therapy because of their high piezoelectric response, Curie temperature, and relatively narrow optical bandgaps. Herein, we report the design of a rare-earth hexagonal manganite material [iron (Fe)-doped yttrium manganite (YMnO 3 ) nanoparticles (YMnO 3:Fe NPs)] for piezocatalytic therapy. The introduction of Fe dopants through polarization engineering increased the tilt angle in the manganese oxide (MnO 5 ) triangular bipyramidal structure in the YMnO 3:Fe lattice, enhancing the crystal asymmetry, spontaneous polarization, and piezoelectric performance. Concurrently, density functional theory calculation revealed that Mn–O covalency increased and Fe–O–Mn bond angle distortion reduced energy barriers synergistically, enabling directional electron migration for minimizing efficiency loss. Under ultrasound irradiation, YMnO 3:Fe NPs exhibited a dual enzymatic–piezocatalytic catalytic amplification effect to trigger tumor-cell apoptosis. This cascade effect increased the generation of intracellular reactive oxygen species triggered apoptosis and ferroptosis via glutathione peroxidase 4 suppression and acyl–CoA synthetase long-chain family member 4 upregulation, which inhibited in vivo tumor growth. These findings highlighted the significant potential of rare-earth hexagonal manganite materials for the advancement of cancer therapeutic strategies.