A new nano-sized iron oxide particle with high sensitivity for cellular magnetic resonance imaging.
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.
Chen
Chih-Lung
CL
Biomedical Engineering Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan.
Zhang
Haosen
H
Ye
Qing
Q
Hsieh
Wen-Yuan
WY
Hitchens
T Kevin
TK
Shen
Hsin-Hsin
HH
Liu
Li
L
Wu
Yi-Jen
YJ
Foley
Lesley M
LM
Wang
Shian-Jy
SJ
Ho
Chien
C
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
D005290:Ferric Compounds; C000499:ferric oxide