NaGdF₄ Nanoparticles Coated with Functionalised Ethylenediaminetetraacetic Acid as Versatile Probes for Dual Optical...

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.