Near-Infrared Upconversion Mesoporous Tin Oxide Bio-Photocatalyst for H 2 O 2 -Activatable O 2 -Generating Magnetic Targeting Synergetic Treatment.

Tumor hypoxia compromises the therapeutic efficacy of oxygen (O ₂ )-dependent treatment methods as the endogenous O ₂ levels have an important influence on the production of reaction oxygen species. Herein, a synergistic multifunctional mesoporous Fe@Sn-UCNPs bio-photocatalytic nanoplatform is provided to comprehensively realize endogenous hydrogen peroxide (H ₂ O ₂ )-activatable, self-supplied O ₂ , photothermal performance, and near-infrared-mediated magnetic targeting PDT/PTT simultaneously for relieving tumor hypoxia. Such a nanoplatform is constructed by encapsulating magnetic Fe ₃ O ₄ with lanthanide-ion-doped mesoporous tin oxide upconversion nanoparticles and further modified with phosphorylated serine and poly(ethylene glycol) for enhancing the biocompatibility and solubility. The nanoparticles can be activated by endogenous H ₂ O ₂ and in situ generated O ₂ to relieve hypoxia through catalytic reaction. Therefore, H ₂ O ₂ -responsive/O ₂ -evolving nanoparticles can elevate the O ₂ level in the tumor site for an apparently enhanced PDT effect in vitro and in vivo. What is more, Fe@Sn-UCNPs demonstrate enhanced photothermal conversion efficiency based on the special nanostructure and much more circuit loops for electron transitions between Fe ₃ O ₄ and Sn-UCNPs, and the electronic structure of Fe@Sn-UCNPs was calculated. In addition, such Fe@Sn-UCNPs also exhibit multimodality imaging performance (including photothermal, magnetic resonance, and computed tomography imaging) for monitoring and tracking the in vivo tumor therapeutic process. This work provides novel insight into the smart Fe@Sn-UCNPs as an "all-in-one" theranostic nanosystem for cancer therapy.