Validation of a dendron concept to tune colloidal stability, MRI relaxivity and bioelimination of functional nanoparticles

The functionalization of spherical superparamagnetic iron oxide nanoparticles (SPION) of 10 nm with a linear monophosphonate (L1) and also PEGylated mono-phosphonated dendrons of growing generation (D2-G1, -G2 and -G3) yielded dendritic nano-objects of 15 to 30 nm in size, stable in physiological media and showing both renal and hepatobiliary elimination. The grafting of the different molecules has been confirmed by IR spectroscopy and elemental analysis. The colloidal stability of functionalized NS10 has been evaluated in water and in different physiological media. All functionalized NS10 were stable over a long period of time and displayed a mean hydrodynamic diameter smaller than 50 nm whatever the molecule architecture or dendron generation. Only the NS10@L1 showed less stability in biological media at high ionic concentration. NMRDprofiles and relaxivity measurements highlighted the influence of the molecule architecture on the water diffusion close to the magnetic core thus influencing the relaxation properties at low magnetic field. Coupling of a fluorescent dye on the functionalized NS10 allowed investigating their biodistribution and highlighting urinary and hepato-biliary eliminations.