Single W₁₈O₄₉ nanowires: A multifunctional nanoplatform for computed tomography imaging and photothermal/photodynamic/radiation synergistic cancer therapy

Combination therapy is a promising cancer treatment strategy that is usually based on the utilization of complicated nanostructures with multiple components functioning as photo-thermal energy transducers, photo-sensitizers, or dose intensifiers for photothermal therapy (PTT), photodynamic therapy (PDT), or radiation therapy (RT). In this study, ultrathin tungsten oxide nanowires (W₁₈O₄₉) were synthesized using a solvothermal approach and examined as a multifunctional theranostic nanoplatform. In vitro and in vivo analyses demonstrated that these nanowires could induce extensive heat- and singlet oxygen-mediated damage to cancer cells under 980 nm near infrared (NIR)-laser excitation. They were also shown to function as radiation dose intensifying agents that enhance irradiative energy deposition locally and selectively during radiation therapy. Compared to NIR-induced PTT/PDT and RT alone, W₁₈O₄₉-based synergistic tri-modal therapy eradicated xenograft tumors and no recurrence was observed within a 9-month follow up. Moreover, the strong X-ray attenuation ability of the tungsten element (Z = 74, 4.438 cm²·g^-1, 100 KeV) qualified these nanowires as excellent contrast agents in X-ray-based imaging, such as diagnostic computed tomography (CT) and cone-beam CT for image-guided radiation therapy. Toxicity studies demonstrated minimal adverse effects on the hematologic system and major organs of mice within one month. In conclusion, these nanowires have shown significant potential for cancer therapy with inherent image guidance and synergistic effects from phototherapy and radiation therapy, which warrants further investigation.