▎ 摘　　要

Magnetic resonance contrast agent employs the use of gadolinium chelates, which has many limitations for clinical use including a low contrast effect, a short diagnostic window, and a brief blood circulation time. On this basis, we designed a gadolinium-labeled dendrimer nanocluster (GdDN) loaded graphene oxide nanosheet (GO-GdDN) to boost T-1 contrast ability for imaging in vivo and improve blood circulation time. GO-GdDN presented an ultrahigh r(1) relaxivity up to 19.07 mM(-1) s(-1) in a 9.4 T MR scanner, and a bright contrast image in vitro experiment. In addition, GO-GdDN could be internalized by HepG2 cells and presented strong cell contrast enhancement and reduction of the T-1 value in HepG2 cells. In vivo, the retention time of GO-GdDN was significantly improved, so that the accumulation of GO-GdDN in liver was enhanced. Moreover, compared to Gd-DTPA, systemic delivery of GO-GdDN dramatically enhanced the signal-to-noise ratio of liver images, which was helpful for accurate imaging of liver and detection of liver lesions in vivo. Thus, this study demonstrates the utility of a powerful diagnosis tool for liver tumor or lesions.