High-Performance T₁-T₂ Dual-Modal MRI Contrast Agents through Interface Engineering

Iron oxide nanoparticles (IONPs) have been developed as contrast agents for T₁- or T₂-weighted magnetic resonance imaging (MRI) on account of their excellent physicochemical and biological properties. However, general strategies to improve longitudinal relaxivity (r₁) often decrease transverse relaxivity (r₂), thus synchronously strengthening the T₁ and T₂ enhancement effect of IONPs remains a challenge. Here, we report interface regulation and size tailoring of a group of FePt@Fe₃O₄ core-shell nanoparticles (NPs), which possess high r₁ and r₂ relaxivities. The increase of r₁ and r₂ 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@Fe₃O₄ NPs can serve as a favorable T₁-T₂ dual-modal contrast agent. We envision that the core-shell NPs, through interface engineering, have great potential in preclinical and clinical MRI applications.