Multifunctional uniform core-shell Fe₃O₄@mSiO ₂ mesoporous nanoparticles for bimodal imaging and photothermal therapy

Multimodal imaging and simultaneous therapy is highly desirable because it can provide complementary information from each imaging modality for accurate diagnosis and, at the same time, afford an imaging-guided focused tumor therapy. In this study, indocyanine green (ICG), a near-infrared (NIR) imaging agent and perfect NIR light absorber for laser-mediated photothermal therapy, was successfully incorporated into superparamagnetic Fe₃O ₄@mSiO₂ core-shell nanoparticles to combine the merit of NIR/magnetic resonance (MR) bimodal imaging properties with NIR photothermal therapy. The resultant nanoparticles were homogenously coated with poly(allylamine hydrochloride) (PAH) to make the surface of the composite nanoparticles positively charged, which would enhance cellular uptake driven by electrostatic interactions between the positive surface of the nanoparticles and the negative surface of the cancer cell. A high biocompatibility of the achieved nanoparticles was demonstrated by using a cell cytotoxicity assay. Moreover, confocal laser scanning microscopy (CLSM) observations indicated excellent NIR fluorescent imaging properties of the ICG-loaded nanoparticles. The relatively high r₂ value (171.6 mM^-1 s^-1) of the nanoparticles implies its excellent capability as a contrast agent for MRI. More importantly, the ICG-loaded nanoparticles showed perfect NIR photothermal therapy properties, thus indicating their potential for simultaneous cancer diagnosis as highly effective NIR/MR bimodal imaging probes and for NIR photothermal therapy of cancerous cells.