Effect of the Functionalization Process on the Colloidal, Magnetic Resonance Imaging, and Bioelimination Properties of Mono- or Bisphosphonate-Anchored Dendronized Iron Oxide Nanoparticles.

The functionalization process of iron oxide nanoparticles (NPs) is a major step and has to ensure a small particle size distribution (below 100 nm) and to preserve good magnetic properties suitable for in vivo applications. Two functionalization processes are here compared to coat iron oxide NPs, synthesized by thermal decomposition, with dendron molecules bearing either a mono- or a bisphosphonate anchoring group. The two processes are direct ligand exchange and the simultaneous ligand exchange and phase transfer process. The latter process led to a larger size distribution than the former. The phosphonate group is confirmed to be a strong anchoring agent from X-ray photoelectron spectroscopy (XPS) and IR characterizations whatever the grafting process and the number of phosphonate groups, it also confirms the preservation of the NPs' magnetic properties. All dendronized NPs display good in vitro MRI properties and those obtained by direct exchange showed no cell internalization, an efficient in vivo MRI contrast enhancement, and elimination by both urinary and hepato-biliary ways.