Magnetic resonance imaging/fluorescence dual modality protocol using designed phosphonate ligands coupled to superparamagnetic iron oxide nanoparticles

A simple and versatile methodology to tailor the surface of superparamagnetic iron oxide nanoparticles (SPIONs), and render additional fluorescence capability to these contrast agents, is reported. The dual modality imaging protocol was developed by designing multi-functional scaffolds with a combination of orthogonal moieties for aqueous dispersion and stealth, to covalently link them to SPIONs, and carry out post-functionalization of nanoparticles. SPIONs stabilized with ligands incorporating surface-anchoring phosphonate groups, ethylene glycol backbone for aqueous dispersion, and free surface exposed OH moieties were coupled to near-infrared dye Cy5.5A. Our results demonstrate that design of multi-tasking ligands with desired combination and spatial distribution of functions provides an ideal platform to construct highly efficient dual imaging probes with balanced magnetic, optical and cell viability properties.