Silica‐Coated Manganese Oxide Nanoparticles as a Platform for Targeted Magnetic Resonance and Fluorescence Imaging of Cancer Cells

Abstract

Monodisperse silica‐coated manganese oxide nanoparticles (NPs) with a diameter of ∼35 nm are synthesized and are aminated through silanization. The amine‐functionalized core–shell NPs enable the covalent conjugation of a fluorescent dye, Rhodamine B isothiocyanate (RBITC), and folate (FA) onto their surface. The formed Mn 3 O 4@SiO 2(RBITC)–FA core–shell nanocomposites are water‐dispersible, stable, and biocompatible when the Mn concentration is below 50 µg mL−1 as confirmed by a cytotoxicity assay. Relaxivity measurements show that the core–shell NPs have a T1 relaxivity (r1) of 0.50 m M−1 s−1 on the 0.5 T scanner and 0.47 m M−1 s−1 on the 3.0 T scanner, suggesting the possibility of using the particles as a T1 contrast agent. Combined flow cytometry, confocal microscopy, and magnetic resonance imaging studies show that the Mn 3 O 4@SiO 2(RBITC)–FA nanocomposites can specifically target cancer cells overexpressing FA receptors (FARs). Findings from this study suggest that the silica‐coated Mn 3 O 4 core–shell NPs could be used as a platform for bimodal imaging (both magnetic resonance and fluorescence) in various biological systems.