Novel carbon nanohybrids as highly efficient magnetic resonance imaging contrast agents

Novel carbon nanohybrids based on unmodified metallofullerenes have been successfully fabricated for use as a new magnetic resonance imaging （MRI） contrast agent. The nanohybrids showed higher R1 relaxivity and better brightening effect than Gd@C82（OH）x, in Tl-weighted MR images in vivo. This is a result of the proton relaxivity from the original gadofullerenes, which retained a perfect carbon cage structure and so might completely avoid the release of Gd^3＋ ions. A ＂secondary spin-electron transfer＂ relaxation mechanism was proposed to explain how the encaged Gd^3＋ ions of carbon nanohybrids interact with the surrounding water molecules. This approach opens new opportunities for developing highly efficient and low toxicity MRI contrast agents.