Prussian Blue Analogue Islands on BiOCl-Se Nanosheets for MR/CT Imaging-Guided Photothermal/Photodynamic Cancer Therapy

Precision therapy combines the advantages of multimodal imaging and a synergistic treatment, which can provide higher therapeutic efficacy and a more rigorous diagnosis than solitary imaging or ordinary therapy. In this research, we synthesized innovative Se-doped BiOCl nanosheets (Se-BiOCl) via a solvothermal method. Then, islands of Prussian blue analogues (PBA) Bi₄[Fe(CN)₆]₃ were loaded on the Se-BiOCl nanosheets via surface ion-exchange reactions to obtain the Se-BiOCl/PBA composite nanosheets. The successful integration of PBA made progressive T₁- and T₂-weighted magnetic resonance imaging (MRI) possible. In addition, the advanced computed tomography (CT) capabilities matched the high X-ray attenuation coefficient of Bi, thereby realizing multimodal imaging for accurate diagnoses. The strong absorbance in the near-infrared range provided by PBA offers high antitumor efficacy for photothermal therapy (PTT). In addition, with the doping of Se, the band gap of Se-BiOCl was adjusted from 387 nm (BiOCl) to 540 nm, thus resulting in effective photodynamic therapy (PDT) by visible light. The favorable trimodal imaging and synergistic therapy were further confirmed to have significant positive effectiveness both in vitro and in vivo. These biocompatible theranostic nanoagents produced by surface ion-exchanges, highly integrated multimodal imaging, and combined treatments may have high potential for clinical antitumor applications.