Multifunctional Fe5C2 nanoparticles: A platform for magnetic resonance imaging, photoacoustic tomography and photothermal therapy

Summary form only given. Hagg iron carbide nanoparticles (Fe₅C₂ NPs) encapsulated by carbon, which preserving high magnetic properties, can be good candidates for magnetic resonance imaging (MRI). With carbon coating, high near-infrared (NIR) optical absorbance can be pursued for potential biological applications, including photoacoustic tomography (PAT) and photothermal therapy (PTT). Here, we present Fe₅C₂-based NPs, Fe₅C₂-PEG-Z_HER2:342 as a novel probe for bimodal tumor imaging and therapy. The probe exhibits high saturation magnetization (102 emu/g), r₂ relaxivity (142.13 mM^-1s^-1) and temperature increasing after exposure to NIR, and the conjugation of Z_HER2:342 enabled the targeting to HER2-overexpressed cells (SK-OV-3 cells). After incubation with Fe₅C₂-PEG-Z_HER2:342 in vitro, SK-OV-3 cells showed much lower MRI T₂ signal compared with cells incubated with Fe₅C₂-PEG or without treatment, and no noticeable in vitro toxicity has been observed. Determined by using a uorescent viability stain, cells incubated with Fe₅C₂-PEG-Z_HER2:342 and exposed to NIR light (808 nm) were found to have undergone photothermally induced morbidity. The in vivo experiments were carried out on nude mice with ovarian cancer modal. After injection of Fe₅C₂-PEG-Z_HER2:342 through the tail vein, it showed long-lasting negative-contrast enhancement MRI as well as high PAT signal at the tumor site. We further use Fe₅C₂-PEG-Z_HER2:342 for PTT, and achieved effective tumor ablation after NIR irritation. From the loss of body weight, morphological and pathological examinations, almost no systematic toxicity has been observed. Our results highlight the great potential of Fe₅C₂-PEG-Z_HER2:34- as a multifunctional probe for cancer theranostic applications.