NaGdF4Nanoparticles Coated with Functionalised Ethylenediaminetetraacetic Acid as Versatile Probes for Dual Optical and Magnetic Resonance Imaging

NaGdF4 nanoparticles (NPs) coated with organic ligands are known to provide efficient positive contrast in magnetic resonance imaging (MRI). Strongly chelating ligands, such as ethylenediaminetetraacetic acid (EDTA) and d,l-1,2-diaminopropionic-N,N,N,N-tetraacetic acid (EDTACOOH), which is an EDTA derivative with a functionalisable carboxylic group, were used to coat NaGdF4. The carboxylic group was used to insert a polyethylene glycol (PEG) functionality (to give EDTAPEG) to favour better suspension and stealth and/or a fluorescent dye to obtain dual optical/MRI probes. The relaxometric behaviour of these NPs was investigated as a function of the magnetic field strength, and a significant contribution from water molecules hydrogen bonded to the organic coating was evidenced. The chemical stability of the NPs was evaluated both in a physiological medium and in the presence of a strong chelating agent. Finally, the dye-functionalised NPs were tested in ovarian carcinoma cells as dual optical and MRI probes.