Photo-Responsive Self-Assembled Polymeric Nanoparticle Probes for 19 F MRI Theranostics.

19 F magnetic resonance imaging (MRI)-assisted drug delivery provides the possibility to monitor and track drug transportation details in situ. A series of photo-responsive amphiphilic block copolymers consisting of hydrophilic poly(ethylene glycol) and 19 F-containing hydrophobic segments, poly(2,2,2-trifluoroethyl acrylate) (PTFEA), with different chain lengths were synthesized by reversible addition-fragmentation chain-transfer polymerization. In particular, the photo-sensitive functional group of o -nitrobenzyl oxygen was introduced to control the photolysis behavior of the copolymers under ultraviolet irradiation. With the extension of the hydrophobic chain length, the drug loading capacity and photoresponsivity were both enhanced, while the chain mobility of PTFEA was suppressed, and the 19 F MRI signal was attenuated. When the polymerization degree of PTFEA was about 10, the nanoparticles exhibit detectable 19 F MRI signals and sufficient drug loading capacity (loading efficiency = 10%, cumulative release = 49%). These results offer a promising "smart" theranostic platform for 19 F MRI.