Integration of PEG-conjugated gadolinium complex and superparamagnetic iron oxide nanoparticles as T1-T2 dual-mode magnetic resonance imaging probes

The T1−T2 dual-mode probes for magnetic resonance imaging (MRI) can noninvasively acquire comprehensive information of different tissues or generate self-complementary information of the same tissue at the same time, making MRI a more flexible imaging modality for complicated applications. In this work, three Gd-DTPA complex conjugated superparamagnetic iron oxide (SPIO) nanoparticles with different Gd/Fe molar ratio (0.94, 1.28 and 1.67) were prepared as T1-T 2 dual-mode MRI probes, named as [email protected], [email protected] and [email protected], respectively. All SPIO@PEG-GdDTPA nanocomposites with 8 nm spherical SPIO nanocrystals showed good Gd3+ chelate stability. [email protected] nanocomposites with lowest Gd/Fe molar ratio shows no cytotoxicity to Raw 264.7 cells as compared to [email protected] and [email protected]. [email protected] nanocomposites with r1 (8.4 mM−1s−1), r2 (83.2 mM−1s−1) and relatively ideal r2/r1 ratio (9.9) were selected for T 1-T2 dual-mode MRI of blood vessels and liver tissue in vivo. Good contrast images were obtained for both cardiovascular system and liver in animal studies under a clinical 3 T scanner. Importantly, one can get high quality contrast-enhanced blood vessel images within the first 2 hours after contrast agent administration and acquire liver tissue anatomy information up to 24 hours. Overall, the strategy of one shot of the dual mode MRI agent could bring numerous benefits not only for patients but also to the radiologists and clinicians, e.g., saving time, lowering side effects, and collecting data of different organs sequentially.