title: Enhanced magnetic resonance imaging and staining of cancer cells using ferrimagnetic H-ferritin nanoparticles with increasing core size.
abstract: OBJECTIVE
  This study is to demonstrate the nanoscale size effect of ferrimagnetic H-ferritin (M-HFn) nanoparticles on magnetic properties, relaxivity, enzyme mimetic activities, and application in magnetic resonance imaging (MRI) and immunohistochemical staining of cancer cells.
  
  
  METHODS
  M-HFn nanoparticles with different sizes of magnetite cores in the range of 2.7-5.3 nm were synthesized through loading different amounts of iron into recombinant human H chain ferritin (HFn) shells. Core size, crystallinity, and magnetic properties of those M-HFn nanoparticles were analyzed by transmission electron microscope and low-temperature magnetic measurements. The MDA-MB-231 cancer cells were incubated with synthesized M-HFn nanoparticles for 24 hours in Dulbecco's Modified Eagle's Medium. In vitro MRI of cell pellets after M-HFn labeling was performed at 7 T. Iron uptake of cells was analyzed by Prussian blue staining and inductively coupled plasma mass spectrometry. Immunohistochemical staining by using the peroxidase-like activity of M-HFn nanoparticles was carried out on MDA-MB-231 tumor tissue paraffin sections.
  
  
  RESULTS
  The saturation magnetization (M(s)), relaxivity, and peroxidase-like activity of synthesized M-HFn nanoparticles were monotonously increased with the size of ferrimagnetic cores. The M-HFn nanoparticles with the largest core size of 5.3 nm exhibit the strongest saturation magnetization, the highest peroxidase activity in immunohistochemical staining, and the highest r2 of 321 mM(-1) s(-1), allowing to detect MDA-MB-231 breast cancer cells as low as 10(4) cells mL(-1).
  
  
  CONCLUSIONS
  The magnetic properties, relaxivity, and peroxidase-like activity of M-HFn nanoparticles are size dependent, which indicates that M-HFn nanoparticles with larger magnetite core can significantly enhance performance in MRI and staining of cancer cells.
authors: France-China Bio-Mineralization and Nano-Structures Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China ; Paleomagnetism and Geochronology Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China ; University of Chinese Academy of Sciences, Beijing, People's Republic of China.
authors: Yao
authors: Y
authors: Cai
authors: France-China Bio-Mineralization and Nano-Structures Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China ; Paleomagnetism and Geochronology Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China.
authors: Changqian
authors: C
authors: Cao
authors: France-China Bio-Mineralization and Nano-Structures Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China.
authors: Xiaoqing
authors: X
authors: He
authors: France-China Bio-Mineralization and Nano-Structures Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China ; Paleomagnetism and Geochronology Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China ; University of Chinese Academy of Sciences, Beijing, People's Republic of China.
authors: Caiyun
authors: C
authors: Yang
authors: France-China Bio-Mineralization and Nano-Structures Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China ; Paleomagnetism and Geochronology Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China.
authors: Lanxiang
authors: L
authors: Tian
authors: Paleomagnetism and Geochronology Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China.
authors: Rixiang
authors: R
authors: Zhu
authors: France-China Bio-Mineralization and Nano-Structures Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China ; Paleomagnetism and Geochronology Laboratory, Key Laboratory of the Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, People's Republic of China.
authors: Yongxin
authors: Y
authors: Pan
mesh_terms: D045744:Cell Line, Tumor; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D009369:Neoplasms / Q000737:chemistry / Q000378:metabolism; D010316:Particle Size; D013194:Staining and Labeling / Q000379:methods*
chemical_list: D058185:Magnetite Nanoparticles
keywords: cancer cells; magnetic nanoparticles; magnetic resonance imaging; magnetoferritin; peroxidase-like activity