To realize precise diagnosis of early-stage cancer for effective treatment and better prognosis, high-resolution magnetic resonance imaging (MRI) is indispensable with the help of contrast agents. Iron-oxide-based T₂ MR contrast agent (IOCA) is facing severe question of strong ferromagnetism and thereby weak T₂ contrast ability. Although numerous efforts have been devoted to enhance the contrast ability of IOCAs, such as gadolinium ions (Gd³⁺) doping, the specific role that Gd³⁺ played in this process remained unclear.

Researchers led by Prof. WU Zhengyan from the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences (CAS), the Institute of Health and Medical Technology and the Binzhou Medical University fabricated a series of Gd-doped iron oxide nanoclusters to systemically study the inherent mechanism through which Gd doping tune the T₂ contrast ability of the nanoclusters.

The researchers found that, with the doping content increased, GdxFe₃-xO₄ nanocluster featuring ferromagnetism turned into a superparamagnetic one, and the specific surface area of the nanocluster significantly increased, collectively leading to stronger T₂ contrast.

"We obtained the highest r₂ value, four times higher than that for pristine Fe₃O₄," said GAN Yuehao, first author of the study, "the contrast of Gd_0.018Fe_2.982O₄ nanocluster offers possible method to diagnose early orthotopic cancer in mice."

This work opens a new avenue for the development of atomically precise Gd-doped MMIONs as efficient T₂-weighted MRI contrast agents.

This research has been published in Chemical Engineering Journal and it was supported by the National Natural Science Foundation of China, the Natural Science Foundation of Anhui Province, and the Shandong Provincial Natural Science Foundation.

Schematic illustration of the mechanism of Gd doping-enhanced T₂ relaxation rate of Fe₃O₄ nanocluster. (Image by GAN Yuehao)