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

Abstract

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 ¹⁹F 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 ¹⁹F spin–lattice (T₁) and spin–spin (T₂) relaxation times and ¹⁹F image intensities of solutions of the polymers were measured and related to polymer structure and aqueous conformation. The ¹⁹F NMR T₂ relaxation times were found to be highly indicative of the ¹⁹F imaging performance. Maintaining sufficient mobility of the ¹⁹F nuclei was important for obtaining images of high intensity. ¹⁹F mobility could be increased by preventing their aggregation in water by exploiting electrostatic repulsion between monomer units.