Functionalized Gold Nanoparticles as Contrast Agents for Proton and Dual Proton/Fluorine MRI

Gold nanoparticles carrying fluorinated ligands in their monolayer are, by themselves, contrast agents for (19)F magnetic resonance imaging displaying high sensitivity because of the high density of fluorine nuclei achievable by grafting suitable ligands on the gold core surface. Functionalization of these nanoparticles with Gd(III) chelates allows adding a further functional activity to these systems, developing materials also acting as contrast agents for proton magnetic resonance imaging. These dual mode contrast agents may allow capitalizing on the benefits of (1)H and (19)F magnetic resonance imaging in a single diagnostic session. In this work, we describe a proof of principle of this approach by studying these nanoparticles in a high field preclinical scanner. The Gd(III) centers within the nanoparticles monolayer shorten considerably the (19)F T1 of the ligands but, nevertheless, these systems display strong and sharp NMR signals which allow recording good quality (19)F MRI phantom images at nanoparticle concentration of 20 mg/mL after proper adjustment of the imaging sequence. The Gd(III) centers also influence the T1 relaxation time of the water protons and high quality (1)H MRI images could be obtained. Gold nanoparticles protected by hydrogenated ligands and decorated with Gd(III) chelates are reported for comparison as (1)H MRI contrast agents.