Synthesis and evaluation of partly fluorinated polyelectrolytes as components in 19F MRI-detectable nanoparticles

A series of partly fluorinated polyelectrolytes were synthesized by transition metal mediated living radical polymerization and evaluated for their applicability as corona-forming components in F-19 MRI-detectable nanoparticles in aqueous solutions. The polymers were statistical and block copolymers of trifluoroethyl methacrylate (TFEMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA). The polymers were either directly dissolved in water (statistical copolymers), or assembled into aqueous nanoparticles with PTFEMA cores and P(TFEMA-co-DMAEMA) coronas (block copolymers). The polymer composition, polymer charge density, solution ionic strength and solution pH were varied. The F-19 spin-lattice (T-1) and spin-spin (T-2) relaxation times and F-19 image intensities of solutions of the polymers were measured and related to polymer structure and aqueous conformation. The F-19 NMR T-2 relaxation times were found to be highly indicative of the F-19 imaging performance. Maintaining sufficient mobility of the F-19 nuclei was important for obtaining images of high intensity. F-19 mobility could be increased by preventing their aggregation in water by exploiting electrostatic repulsion between monomer units.