Polyol-Made Luminescent and Superparamagnetic β-NaYEuF@γ-FeO Core-Satellites Nanoparticles for Dual Magnetic Resonance and Optical Imaging.

Red luminescent and superparamagnetic β-NaYEuF@γ-FeO nanoparticles, made of a 70 nm-sized β-NaYEuF single crystal core decorated by a 10 nm-thick polycrystalline and discontinuous γ-FeO shell, have been synthesized by the polyol process. Functionalized with citrate ligands they show a good colloidal stability in water making them valuable for dual magnetic resonance and optical imaging or image-guided therapy. They exhibit a relatively high transverse relaxivity r = 42.3 mM·s in water at 37 °C, for an applied static magnetic field of 1.41 T, close to the field of 1.5 T applied in clinics, as they exhibit a red emission by two-photon excited fluorescence microscopy. Finally, when brought into contact with healthy human foreskin fibroblast cells (BJH), for doses as high as 50 µg·mL and incubation time as long as 72 h, they do not show evidence of any accurate cytotoxicity, highlighting their biomedical applicative potential.