Magnetic Prussian Blue Nanoparticles for Targeted Photothermal Therapy under Magnetic Resonance Imaging Guidance

This paper reported a core–shell nanotheranostic agent by growing Prussian blue (PB) nanoshells of 3–6 nm around superparamagnetic Fe₃O₄ nanocores for targeted photothermal therapy of cancer under magnetic resonance imaging (MRI) guidance. Both <i>in vitro</i> and <i>in vivo</i> experiments proved that the Fe₃O₄@PB core–shell nanoparticles showed significant contrast enhancement for T₂-weighted MRI with the relaxivity value of 58.9 mM^–1·s^–1. Simultaneously, the composite nanoparticles exhibited a high photothermal effect under irradiation of a near-infrared laser due to the strong absorption of PB nanoshells, which led to more than 80% death of HeLa cells with only 0.016 mg·mL^–1 of the nanoparticles with the aid of the magnetic targeting effect. Using tumor-bearing nude mice as the model, the near-infrared laser light ablated the tumor effectively in the presence of the Fe₃O₄@PB nanoparticles and the tumor growth inhibition was evaluated to be 87.2%. Capabilities of MRI, magnetic targeting, and photothermal therapy were thus integrated into a single agent to allow efficient MRI-guided targeted photothermal therapy. Most importantly, both PB and Fe₃O₄ nanoparticles were already clinically approved drugs, so the Fe₃O₄@PB nanoparticles as a theranostic nanomedicine would be particularly promising for clinical applications in the human body due to the reliable biosafety