Enhanced Sonodynamic Therapy via Au Nanoclusters Deposited on TiO2 Nanosheets.

Purpose: This study aimed to enhance the efficacy of sonodynamic therapy (SDT) for breast cancer by engineering TiO₂ nanosheets modified with Au nanoclusters (TiO₂-Au), thereby improving reactive oxygen species (ROS) generation under ultrasound (US) irradiation.

Methods: TiO₂-Au sonosensitizers were synthesized via a deposition-precipitation with urea (DPU) method and characterized by TEM, XRD, and XPS. ROS generation efficiency was quantified using DPBF, TMB, and NBT probes, along with electron spin resonance (ESR). In vitro therapeutic performance was assessed in 4T1 breast cancer cells via flow cytometry, Calcein-AM/PI staining, and cell counting kit-8 (CCK-8) assay. In vivo efficacy and biosafety were validated in 4T1 tumor-bearing BALB/c mice through tumor growth monitoring, histological analysis, blood biochemistry, and hemolysis assays.

Results: TiO₂-Au_10.5 exhibited enhanced electron-hole separation, reduced bandgap (from 3.2 to 2.8 eV), and significantly boosted ROS generation under US irradiation. In vitro, TiO₂-Au_10.5 combined with US induced a 4.25-fold increase in intracellular ROS and a 4.7-fold higher apoptosis rate compared to TiO₂ + US. In vivo, TiO₂-Au_10.5 + US achieved a tumor growth inhibition index of 76.9% without significant toxicity, as evidenced by normal blood markers, no hemolysis, and no damage to major organs.

Conclusion: Au nanocluster modification effectively tunes the sonodynamic performance of TiO₂ nanosheets by modulating electron-hole separation and ROS production. Notably, varying the Au content enabled precise regulation of SDT efficacy, with TiO₂-Au_10.5 achieving optimal therapeutic outcomes. These findings highlight TiO₂-Au as a safe, potent, and composition-tunable sonosensitizer platform for precise and effective cancer therapy.