High-Performance T 1 - T 2 Dual-Modal MRI Contrast Agents through Interface Engineering.

Iron oxide nanoparticles (IONPs) have been developed as contrast agents for T 1 - or T 2 -weighted magnetic resonance imaging (MRI) on account of their excellent physicochemical and biological properties. However, general strategies to improve longitudinal relaxivity ( r 1 ) often decrease transverse relaxivity ( r 2 ), thus synchronously strengthening the T 1 and T 2 enhancement effect of IONPs remains a challenge. Here, we report interface regulation and size tailoring of a group of FePt@Fe 3 O 4 core-shell nanoparticles (NPs), which possess high r 1 and r 2 relaxivities. The increase of r 1 and r 2 is due to the enhancement of the saturation magnetization ( M s ), which is a result of the strengthened exchange coupling across the core-shell interface. In vivo subcutaneous tumor study and brain glioma imaging revealed that FePt@Fe 3 O 4 NPs can serve as a favorable T 1 - T 2 dual-modal contrast agent. We envision that the core-shell NPs, through interface engineering, have great potential in preclinical and clinical MRI applications.