On-off regulation of 19F magnetic resonance signals based on pH-Sensitive PEGylated nanogels for potential tumor-specific smart 19F MRI probes

The pH-sensitive PEGylated nanogels constructed from tethered PEG chains and a polyamine gel core containing F-19 compounds showed remarkable on-off regulation of F-19 MR (magnetic resonance) signals in response to the extracellular pH (6.5) of the tumor environment, even in the presence of 90% fetal bovine serum, due to the increase in the molecular motion of the F-19 compounds through the hydrophilic-hydrophobic (volume-phase) transition of the polyamine gel core. Eventually, an appreciably enhanced F-19 MR signal at an extremely low F-19 compound concentration (similar to 55 mu M) was achieved, demonstrating the utility of these nanogels as solid tumor-specific smart F-19 MRI probes.