title: Dual-modal nanoprobes for imaging of mesenchymal stem cell transplant by MRI and fluorescence imaging.
abstract: OBJECTIVE
  To determine the feasibility of labeling human mesenchymal stem cells (hMSCs) with bifunctional nanoparticles and assessing their potential as imaging probes in the monitoring of hMSC transplantation.
  
  
  METHODS
  The T1 and T2 relaxivities of the nanoparticles (MNP@SiO(2)[RITC]-PEG) were measured at 1.5T and 3T magnetic resonance scanner. Using hMSCs and the nanoparticles, labeling efficiency, toxicity, and proliferation were assessed. Confocal laser scanning microscopy and transmission electron microscopy were used to specify the intracellular localization of the endocytosed iron nanoparticles. We also observed in vitro and in vivo visualization of the labeled hMSCs with a 3T MR scanner and optical imaging.
  
  
  RESULTS
  MNP@SiO(2)(RITC)-PEG showed both superparamagnetic and fluorescent properties. The r(1) and r(2) relaxivity values of the MNP@SiO(2)(RITC)-PEG were 0.33 and 398 mM(-1) s(-1) at 1.5T, respectively, and 0.29 and 453 mM(-1) s(-1) at 3T, respectively. The effective internalization of MNP@SiO(2)(RITC)-PEG into hMSCs was observed by confocal laser scanning fluorescence microscopy. The transmission electron microscopy images showed that MNP@SiO(2)(RITC)-PEG was internalized into the cells and mainly resided in the cytoplasm. The viability and proliferation of MNP@SiO(2)(RITC)-PEG-labeled hMSCs were not significantly different from the control cells. MNP@SiO(2)(RITC)-PEG-labeled hMSCs were observed in vitro and in vivo with optical and MR imaging.
  
  
  CONCLUSIONS
  MNP@SiO(2)(RITC)-PEG can be a useful contrast agent for stem cell imaging, which is suitable for a bimodal detection by MRI and optical imaging.
authors.affiliation: Department of Radiology, Seoul Metropolitan Boramae Medical Center, Seoul National University College of Medicine, Seoul 156-707, Korea. sckmd@hanmail.net
authors.forename: Chang Kyu
authors.initials: CK
authors.lastname: Sung
authors.forename: Kyung Ah
authors.initials: KA
authors.lastname: Hong
authors.forename: Shunmei
authors.initials: S
authors.lastname: Lin
authors.forename: Yuwon
authors.initials: Y
authors.lastname: Lee
authors.forename: Jinmyung
authors.initials: J
authors.lastname: Cha
authors.forename: Jin-Kyu
authors.initials: JK
authors.lastname: Lee
authors.forename: Cheol Pyo
authors.initials: CP
authors.lastname: Hong
authors.forename: Bong Soo
authors.initials: BS
authors.lastname: Han
authors.forename: Sung Il
authors.initials: SI
authors.lastname: Jung
authors.forename: Seung Hyup
authors.initials: SH
authors.lastname: Kim
authors.forename: Kang Sup
authors.initials: KS
authors.lastname: Yoon
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D002478:Cells, Cultured; D003035:Cobalt; D005240:Feasibility Studies; D005290:Ferric Compounds; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D059630:Mesenchymal Stem Cells; D051379:Mice; D008819:Mice, Nude; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D053758:Nanoparticles / Q000737:chemistry*; D019047:Phantoms, Imaging; D011092:Polyethylene Glycols; D051381:Rats; D012235:Rhodamines; D012822:Silicon Dioxide; D013194:Staining and Labeling / Q000379:methods
chemical_list: D001672:Biocompatible Materials; D005290:Ferric Compounds; D012235:Rhodamines; C000499:ferric oxide; D003035:Cobalt; D011092:Polyethylene Glycols; D012822:Silicon Dioxide; C029773:rhodamine B