NaGdF₄ nanoparticles 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. Caught on camera: NaGdF₄ nanoparticles coated with ethylenediaminetetraacetic acid (EDTA) chelators functionalized with organic moieties and luminescent dyes were prepared and characterized, and their potential as dual probes for optical/magnetic resonance imaging (MRI) imaging was investigated (see figure).