Dysprosium-Modified Gold Nanoparticles as T_2ex Contrast Agents for Magnetic Resonance Imaging

With the development of high magnetic field strength in magnetic resonance imaging (MRI), there is a demand to develop MRI contrast agents to attain high relaxation effects. Compared to typical T1 agents, the transverse relaxation rate of T2-based contrast agents increases with increasing magnetic field strength. However, better contrast agents are needed to improve the signal-to-noise issue. Here, a series of T2ex contrast agents composed of an Au nanoparticle (NP) and a dysprosium complex (AuNP-DyDOTA(amide)x) were designed. The transverse relaxivity of three molecules bearing different side arm chains were investigated. After screening by NMR signals, the transverse relaxivity of AuNP-DyDOTA(amide)2 achieved 22.9 mM–1 s–1 at 9.4 T, which is higher than dysprosium-based small molecules. The in vivo results demonstrate that the AuNP-DyDOTA(amide)2 is very efficient for specific accumulation in tumor regions and rapid metabolization was realized, making them promising for ultrahigh field strength imaging and clinical diagnosis in the future.