Gold nanoparticles protected by fluorinated ligands for 19F MRI

One of the tremendous areas of growth on the research side involves using nanomaterials both as imaging agents and as drug delivery vehicles. Nuclear magnetic resonance imaging (MRI) is a particular attractive imagin modality: it provides high-resolution, detailed structural images, three-dimensional spatial reconstruction, and no ionizing radiation.[1] Moreover, MRI is superior to optical bio-imaging in living systems for the visualization of deep tissues. 1H and 19F are the most sensitive nucleai for MRI, with the 1H signal suited for collecting information about the body for diagnostic purposes due to its high sensitivity. However, 1H MRI often suffers from a low contrast-to-noise ratio because of the large background signals from water protons. Therefore, for specific imaging both in vivo and ex vivo, there is still an obvious need to develop new methodologies. In particular, 19F holds great promise as an alternative nuclide for MRI as it is highly sensitive in nuclear magnetic resonance (NMR) spectroscopy (83% relative to 1H) and has 100% natural abundance. A more important advantage of 19F is that in animal bodies essentially no endogenous 19F is detectable by MRI, which therefore eliminates interference from background signals. Moreover, unlike other prototypical metal-based contrast agents, 19F MRI also enables image quantification.[2] As 19F imaging agents, a variety of fluorinated small molecule compounds have been proposed, perfluoro-15-crown-5-ether (PFCE) or perfluorobenzene (PFB) being the most commonly used perfluorocarbons (PFCs) in 19F-MRI research. These PFC molecules have poor solubility in water and, as such, are typically emulsified into lipid micro/NP formulations for biological applications. Moreover, such lipid-based formulations sometimes have drawbacks, which limit imaging capabilities to the vasculature with intravenous administration. In the last years we have reported examples of water soluble gold nanoparticles (NPs) protected by homoligand and heteroligand fluorinated-/hydrogenated ligands.[3] We will reported in this communication the design, synthesis, and characterization of gold nanoparticles (NPs) protected by fluorinated ligands which are endowed with 19F NMR properties suitable for applications in diagnostic imaging. Considering that gold NPs are excellent scaffold for medical uses and that they can be easily modified introducing pro(drugs) and specific recognition elements, our fluorinated NPs may behave both as imaging and therapeutic agents.