title: A new nano-sized iron oxide particle with high sensitivity for cellular magnetic resonance imaging.
abstract: OBJECTIVE
  In this study, we investigated the labeling efficiency and magnetic resonance imaging (MRI) signal sensitivity of a newly synthesized, nano-sized iron oxide particle (IOP) coated with polyethylene glycol (PEG), designed by Industrial Technology Research Institute (ITRI).
  
  
  METHODS
  Macrophages, bone-marrow-derived dendritic cells, and mesenchymal stem cells (MSCs) were isolated from rats and labeled by incubating with ITRI-IOP, along with three other iron oxide particles in different sizes and coatings as reference. These labeled cells were characterized with transmission electron microscopy (TEM), light and fluorescence microscopy, phantom MRI, and finally in vivo MRI and ex vivo magnetic resonance microscopy (MRM) of transplanted hearts in rats infused with labeled macrophages.
  
  
  RESULTS
  The longitudinal (r (1)) and transverse (r (2)) relaxivities of ITRI-IOP are 22.71 and 319.2 s(-1) mM(-1), respectively. TEM and microscopic images indicate the uptake of multiple ITRI-IOP particles per cell for all cell types. ITRI-IOP provides sensitivity comparable or higher than the other three particles shown in phantom MRI. In vivo MRI and ex vivo MRM detect punctate spots of hypointensity in rejecting hearts, most likely caused by the accumulation of macrophages labeled by ITRI-IOP.
  
  
  CONCLUSIONS
  ITRI-IOP, the nano-sized iron oxide particle, shows high efficiency in cell labeling, including both phagocytic and non-phagocytic cells. Furthermore, it provides excellent sensitivity in T(2)*-weighted MRI, and thus can serve as a promising contrast agent for in vivo cellular MRI.
authors.affiliation: Biomedical Engineering Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan.
authors.forename: Chih-Lung
authors.initials: CL
authors.lastname: Chen
authors.forename: Haosen
authors.initials: H
authors.lastname: Zhang
authors.forename: Qing
authors.initials: Q
authors.lastname: Ye
authors.forename: Wen-Yuan
authors.initials: WY
authors.lastname: Hsieh
authors.forename: T Kevin
authors.initials: TK
authors.lastname: Hitchens
authors.forename: Hsin-Hsin
authors.initials: HH
authors.lastname: Shen
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Yi-Jen
authors.initials: YJ
authors.lastname: Wu
authors.forename: Lesley M
authors.initials: LM
authors.lastname: Foley
authors.forename: Shian-Jy
authors.initials: SJ
authors.lastname: Wang
authors.forename: Chien
authors.initials: C
authors.lastname: Ho
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005290:Ferric Compounds / Q000737:chemistry*; D005434:Flow Cytometry; D008279:Magnetic Resonance Imaging / Q000379:methods*; D053768:Metal Nanoparticles; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D010316:Particle Size; D051381:Rats
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide