Photoacoustic Imaging‐Guided Synergistic Photothermal/Radiotherapy Using Plasmonic Bi/Bi2O3−x Nanoparticles

Abstract The integration of photothermal agents and radiosensitizers has been widely implemented in synergistic antitumor treatment because it maintains the advantages of the single model; however, they result in unsatisfactory treatment effects due to their multi‐component, unstable, and non‐degradable nature. Herein, plasmonic Bi/Bi 2 O 3−x is synthesized by in situ fabrication of Bi 2 O 3−x on elemental Bi through a facile hydrothermal method. After encapsulation with DSPE‐PEG2000‐folate, the Bi/Bi 2 O 3−x nanoparticles (NPs) effectively accumulate in tumor sites to serve as a multifunctional therapeutic agent that can damage tumor sections by absorbing near‐infrared light and X‐rays. As demonstrated in penetration depth experiments, the NPs exhibit excellent photoacoustic imaging capabilities for deep tissues. Both blood biochemistry tests and histological assays demonstrate the biosafety of Bi/Bi 2 O 3−x NPs in vivo due to their acceptable toxicity and biological clearance properties. Consequently, the prepared NPs are a desirable candidate for effective second near‐infrared photothermal/radiotherapy.