Multifunctional Bi₂WO₆ Nanoparticles for CT-Guided Photothermal and Oxygen-free Photodynamic Therapy

The consumption of oxygen in photodynamic therapy (PDT) significantly exacerbates the degree of hypoxia in tumors, which not only impedes the therapeutic effect of PDT, but also drives local tumor recurrence. To relieve the PDT-induced hypoxia and improve the therapeutic outcome of PDT in cancer treatment, herein we reported a class of Bi₂WO₆ nanoparticles (NPs) as a robust multifunctional platform, which integrates the abilities for contrast-enhanced computed tomography (CT) imaging, photothermal therapy, and PDT in an oxygen-free manner. The as-obtained Bi₂WO₆ NPs with a mean diameter of 5.2 nm are stable in phosphate-buffered saline and an in vivo microenvironment-mimicking buffer. The location of the solid tumor could be accurately positioned using Bi₂WO₆-enhanced CT with higher spatial resolution. After being irradiated with an 808 nm laser, these Bi₂WO₆ NPs could realize CT-guided local photothermal ablation of the tumor. Meanwhile, ^•OH radicals were generated simultaneously from the treatment without consuming an oxygen molecule, which enabled these Bi₂WO₆ NPs to exert photodynamic killing effect in an oxygen-free manner during cancer therapy. Remarkable tumor suppression was observed in mice bearing the HeLa xenograft, supporting the promising application of these multifunctional Bi₂WO₆ NPs in the combat against cancers through synergistic photothermal and oxygen-free PDT treatment.