Gold nanoparticles protected by fluorinated ligands: properties and applications

Gold nanoparticles (NPs) protected by self-assembled monolayers of organic thiolates (MPCs) are key nanomaterials for a variety of applications because of their intriguing chemical, optical and electronic properties. The capping monolayer is responsible for the solubility properties of the MPCs and, more importantly, is governing the interfacial interactions with biological systems. Despite the impressive number of publications in the field very few examples of gold nanoparticles coated by fluorinated ligands have been reported so far. The interest stems from the exploitation of the properties of (per)fluoro-compounds which have been used in different structures – like dendrimers, micelles or polymers – and used in a variety of formulations for drug delivery and for imaging or to end up with new materials. Our aim is to exploit the combination of the chemistry of MPCs, enabling the preparation of NPs having desired size and shape, with the features of ligands forming a monolayer composed of a fluorinated region. MPCs soluble in organic solvents and/or in water have been obtained using two different strategies: the design of suitable amphiphilic fluorinated ligands and the use of mixtures of fluorinated and hydrogenated thiolates of appropriate length. Moreover, specific fluorinated thiolates have been designed to obtain MPCs endowed with 19F NMR properties suitable for applications in diagnostic imaging. Considering that gold NPs are excellent scaffolds 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.