Physical and biological optimization of core-shell nanoparticle tracers for in vivo MPI

In this study, in vivo particokinetics of biocompatible MNTs that show optimal MPI performance in the biological environment has been presented. In our previous work, the particokinetics - biodistribution and blood circulation time - of poly(ethylene glycol) (PEG)-coated 17 nm core and ~80nm hydrodynamic diameter MNTs in female CD-1 mice was studied. Specifically, the blood-circulation time was characterized by measuring the particle response function (PRF) of MNTs circulating in blood using our 25 kHz magnetic particle spectrometer (MPS). In comparison to Resovist, monodisperse 17 nm MNTs showed 2x greater signal that was sustained for ~15 minutes of circulation in this rodent model. Current modeling and experimental results indicate that ~22-25 nm is the optimal core size at 25 kHz AC-field, thus we present in vivo circulation characteristics of MNT cores in this optimal size range.