Tunable T1 and T2 contrast abilities of manganese-engineered iron oxide nanoparticles through size control

In this paper, we demonstrate the tunable T-1 and T-2 contrast abilities of engineered iron oxide nanoparticles with high performance for liver contrast-enhanced magnetic resonance imaging (MRI) in mice. To enhance the diagnostic accuracy of MRI, large numbers of contrast agents with T-1 or T-2 contrast ability have been widely explored. The comprehensive investigation of high-performance MRI contrast agents with controllable T-1 and T-2 contrast abilities is of high importance in the field of molecular imaging. In this study, we synthesized uniform manganese-doped iron oxide (MnIO) nanoparticles with controllable size from 5 to 12 nm and comprehensively investigated their MRI contrast abilities. We revealed that the MRI contrast effects of MnIO nanoparticles are highly size-dependent. By controlling the size of MnIO nanoparticles, we can achieve T-1-dominated, T-2-dominated, and T-1-T-2 dual-mode MRI contrast agents with much higher contrast enhancement than the corresponding conventional iron oxide nanoparticles.