Letter abstract
Nature Materials 5, 971 - 976 (2006)
Published online: 19 November 2006 | doi:10.1038/nmat1775
Subject Categories: Nanoscale materials | Biomedical materials | Mechanical properties | Optical, photonic and optoelectronic materials
FeCo/graphitic-shell nanocrystals as advanced magnetic-resonance-imaging and near-infrared agents
Won Seok Seo1, Jin Hyung Lee2, Xiaoming Sun1, Yoriyasu Suzuki3, David Mann1, Zhuang Liu1, Masahiro Terashima3, Philip C. Yang3, Michael V. McConnell3, Dwight G. Nishimura2 & Hongjie Dai1
Nanocrystals with advanced magnetic or optical properties have been actively pursued for potential biological applications, including integrated imaging, diagnosis and therapy1, 2, 3, 4, 5, 6, 7, 8, 9. Among various magnetic nanocrystals10, 11, 12, 13, 14, 15, FeCo has superior magnetic properties, but it has yet to be explored owing to the problems of easy oxidation and potential toxicity10, 16, 17. Previously, FeCo nanocrystals with multilayered graphitic carbon, pyrolytic carbon or inert metals have been obtained15, 18, 19, but not in the single-shelled, discrete, chemically functionalized and water-soluble forms desired for biological applications. Here, we present a scalable chemical vapour deposition method to synthesize FeCo/single-graphitic-shell nanocrystals that are soluble and stable in water solutions. We explore the multiple functionalities of these core–shell materials by characterizing the magnetic properties of the FeCo core and near-infrared optical absorbance of the single-layered graphitic shell. The nanocrystals exhibit ultra-high saturation magnetization, r1 and r2 relaxivities and high optical absorbance in the near-infrared region. Mesenchymal stem cells are able to internalize these nanoparticles, showing high negative-contrast enhancement in magnetic-resonance imaging (MRI). Preliminary in vivo experiments achieve long-lasting positive-contrast enhancement for vascular MRI in rabbits. These results point to the potential of using these nanocrystals for integrated diagnosis and therapeutic (photothermal-ablation) applications.
- Department of Chemistry and Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA
- Division of Cardiovascular Medicine, Stanford University, Stanford, California 94305, USA
Correspondence to: Hongjie Dai1 e-mail: hdai@stanford.edu
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