Zirconia-Platinum Nanohybrids for Ultrasound-Activated Sonodynamic-Thermodynamic Bimodal Therapy by Inducing Intense Intracellular Oxidative Stress.

The therapeutic exploration of nano-zirconia semiconductor largely remains untouched in the field of fundamental science to date. Here, a robust nano-sonosensitizer of ZrO 2- x @Pt is strategically formulated by in situ growth of Pt nanocrystal onto the surface of oxygen-deficient ZrO 2- x . Compared to 3.09 eV of nano-ZrO 2- x , the bandgap of ZrO 2- x @Pt Schottky junction is narrowed down to 2.74 eV. The band bending and bandgap narrowing enables an enhanced e - /h + separation in the presence of aPt electron sink, which facilitates a high yield of singlet oxygen ( 1 O 2 ) and hydroxyl radicals (·OH) under ultrasound (US) irradiation. Moreover, nanozyme Pt with catalase-mimic activity can promote 1 O 2  generation by relieving the hypoxic tumor microenvironment. Upon further modification of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIPH), US-stimulated local thermal shock can disintegrate AIPH to create cytotoxic alkyl radicals ( • R). US-triggered reactive oxygen species generation and hyperthermia-induced alkyl radical production lead to severe and irreversible tumor cell death. Such combinatorial sonodynamic-thermodynamic therapy benefits the tumor eradication and metastasis inhibition at the animal level, with the aid of immunogenetic cell death and immune checkpoint blockade. Taken together, this proof-of-concept paradigm expands the medical use of nano-zirconia and provides useful insights for its therapeutic perspectives.