FeCo/graphitic-shell nanocrystals as advanced magnetic-resonance-imaging and near-infrared agents.
Nanocrystals with advanced magnetic or optical properties have been actively pursued for potential biological applications, including integrated imaging, diagnosis and therapy. Among various magnetic nanocrystals, FeCo has superior magnetic properties, but it has yet to be explored owing to the problems of easy oxidation and potential toxicity. Previously, FeCo nanocrystals with multilayered graphitic carbon, pyrolytic carbon or inert metals have been obtained, 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.
Seo
Won Seok
WS
Department of Chemistry and Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA.
Lee
Jin Hyung
JH
Sun
Xiaoming
X
Suzuki
Yoriyasu
Y
Mann
David
D
Liu
Zhuang
Z
Terashima
Masahiro
M
Yang
Philip C
PC
McConnell
Michael V
MV
Nishimura
Dwight G
DG
Dai
Hongjie
H
D000818:Animals; D003035:Cobalt / Q000737:chemistry*; D003287:Contrast Media / Q000737:chemistry*; D003460:Crystallization / Q000379:methods; D005296:Ferrous Compounds / Q000737:chemistry*; D006108:Graphite / Q000737:chemistry*; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008422:Materials Testing; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D011817:Rabbits; D013055:Spectrophotometry, Infrared / Q000379:methods*
D003287:Contrast Media; D005296:Ferrous Compounds; C007717:ferrocobalt; D003035:Cobalt; D006108:Graphite