"One-for-All"-Type, Biodegradable Prussian Blue/Manganese Dioxide Hybrid Nanocrystal for Trimodal Imaging-Guided Photothermal Therapy and Oxygen Regulation of Breast Cancer.

Multimodal imaging-guided diagnosis and therapy has been highlighted in the area of theranostic nanomaterials. To provide more suitable theranostic candidates, Prussian blue (PB)/manganese dioxide (MnO2) hybrid nanoparticles (PBMn) smaller than 50 nm are prepared by a one-pot method. MnO2, which is reduced from KMnO4, not only controls the particle size, the optical properties, and the transverse relaxation rate (r2) of PB but also enhances the catalysis efficacy of PB to H2O2 for oxygen generation. PBMn can serve as a photoacoustic imaging (PAI) and longitudinal relaxation (T1) mode magnetic resonance imaging contrast agent (14 times and 1.8 times of the saline-treated group, respectively). Injection of PBMn can regulate the oxygen partial pressure of the tumor tissue from 2.1 ± 0.2 to 9.3 ± 0.4 kPa and rearrange the ratio of oxygenated hemoglobin and deoxygenate hemoglobin inside the tumor, which favor the enhancement of the diamagnetic T2-weighted imaging (T2WI) signal intensity (two times that of the saline-treated group). Furthermore, PBMn-mediated PTT can efficiently inhibit the growth of the MCF-7 tumor in vitro and in vivo. PBMn can serve as a PAI/T1/T2 trimodal contrast agent and in imaging-guided PTT, as well as in the oxygen regulation of the exografted breast cancer.