Hollow Pd Nanospheres Conjugated with Ce6 To Simultaneously Realize Photodynamic and Photothermal Therapy

Photothermal therapy (PTT) is successfully integrated with photodynamic therapy (PDT) to effectively improve the curative effect of cancer. The therapy nanoplatform is based on hollow Pd (H-Pd) nanospheres conjugated with Ce6 (Pd@Ce6). H-Pd nanospheres and Ce6 work as PTT and PDT agents, respectively. The H-Pd nanospheres with tunable surface plasmon resonance (SPR) properties effectively absorb light with near-infrared (NIR) emission and then convert the light to heat, selectively killing tumor cells. The experimental results show that H-Pd nanospheres with a size of 90 nm have the strongest absorbance and exhibit a high photothermal conversion efficiency (η) of 70%. Moreover, the absorption intensity and photothermal properties of H-Pd nanospheres do not show any decrease after 6 months of storage at room temperature, showing their excellent stability. Furthermore, after Ce6 is conjugated onto the surface of H-Pd nanospheres using polyethylenimine (PEI) as a linker, Pd@Ce6 not only exhibits the capabilities of photothermal conversion but also generates singlet oxygen (¹O₂), realizing the integration of PDT and PTT. In cell experiments, 86% of HeLa cells are killed after Pd@Ce6 is simultaneously irradiated with 660 and 808 nm lasers for 5 min with a power of 0.5 and 2 W cm^-2, respectively. This successful combination of PTT with PDT to eradicate cancer provides a noninvasive and harmless way for cancer therapy.