Single-phase Dy₂O₃:Tb³⁺ nanocrystals as dual-modal contrast agent for high field magnetic resonance and optical imaging

Ultrasmall terbium ions (Tb³⁺) doped dysprosium oxide (Dy ₂O₃) nanocrystals (NCs) of ∼3 nm diameter have been synthesized and applied as a single-phase dual modality contrast agent for high field magnetic resonance imaging (MRI) and optical imaging. The NCs show excellent positive contrast at 7.0 T MRI in phantom and in vivo imaging in a mouse breast tumor model (MCF-7 cells) injected with NCs. In vitro confocal fluorescence microscopy images show the staining of cultured human bronchial epithelial cells (BEAS-2B) with green fluorescent NCs. In vitro cytotoxicity studies in BEAS-2B and L929 cells indicate that the bifunctional NCs have no appreciable toxicity at a concentration of up to 1000 μg/mL. These results suggest the potential application of these NCs as dual modality contrast agents in a combined high field MRI and fluorescence imaging.