Active-target T1-weighted MR Imaging of Tiny Hepatic Tumor via RGD Modified Ultra-small Fe3O4 Nanoprobes

Developing ultrasensitive contrast agents for the early detection of malignant tumors in liver is highly demanded. Constructing hepatic tumors specific targeting probes could provide more sensitive imaging information but still faces great challenges. Here we report a novel approach for the synthesis of ultra-small Fe 3 O 4 nanoparticles conjugated with c(RGDyK) and their applications as active-target T 1 -weighted magnetic resonance imaging (MRI) contrast agent (T 1 -Fe 3 O 4 ) for imaging tiny hepatic tumors in vivo . RGD-modified T 1 -Fe 3 O 4 nanoprobes exhibited high r 1 of 7.74 mM -1 s -1 and ultralow r 2 /r 1 of 2.8 at 3 T, reflecting their excellent T 1 contrast effect at clinically relevant magnetic field. High targeting specificity together with favorable biocompatibility and strong ability to resist against non-specific uptake were evaluated through in vitro studies. Owing to the outstanding properties of tumor angiogenesis targeting with little phagocytosis in liver parenchyma, hepatic tumor as small as 2.2 mm was successfully detected via the T 1 contrast enhancement of RGD-modified T 1 -Fe 3 O 4 . It is emphasized that this is the first report on active-target T 1 imaging of hepatic tumors, which could not only significantly improve diagnostic sensitivity, but also provide post therapeutic assessments for patients with liver cancer.