title: Electron paramagnetic resonance as a sensitive tool to assess the iron oxide content in cells for MRI cell labeling studies.
abstract: MRI cell tracking is a promising technique to track various cell types (stem cells, tumor cells, etc.) in living animals. Usually, cells are incubated with iron oxides (T(2) contrast agent) in order to take up the particles before being injected in vivo. Iron oxide quantification is important in such studies for validating the labeling protocols and assessing the dilution of the particles with cell proliferation. We here propose to implement electron paramagnetic resonance (EPR) as a very sensitive method to quantify iron oxide concentration in cells. Iron oxide particles exhibit a unique EPR spectrum, which directly reflects the number of particles in a sample. In order to compare EPR with existing methods (Perls's Prussian blue reaction, ICP-MS and fluorimetry), we labeled tumor cells (melanoma and renal adenocarcinoma cell lines) and fibroblasts with fluorescent iron oxide particles, and determined the limits of detection of the different techniques. We show that EPR is a very sensitive technique and is specific for iron oxide quantification as measurements are not affected by endogenous iron. As a consequence, EPR is well adapted to perform ex vivo analysis of tissues after cell tracking experiments in order to confirm MRI results.
authors.affiliation: Louvain Drug Research Institute, Biomedical Magnetic Resonance Research Group, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Danhier
authors.forename: G
authors.initials: G
authors.lastname: De Preter
authors.forename: S
authors.initials: S
authors.lastname: Boutry
authors.forename: I
authors.initials: I
authors.lastname: Mahieu
authors.forename: P
authors.initials: P
authors.lastname: Leveque
authors.forename: J
authors.initials: J
authors.lastname: Magat
authors.forename: V
authors.initials: V
authors.lastname: Haufroid
authors.forename: P
authors.initials: P
authors.lastname: Sonveaux
authors.forename: C
authors.initials: C
authors.lastname: Bouzin
authors.forename: O
authors.initials: O
authors.lastname: Feron
authors.forename: R N
authors.initials: RN
authors.lastname: Muller
authors.forename: B F
authors.initials: BF
authors.lastname: Jordan
authors.forename: B
authors.initials: B
authors.lastname: Gallez
mesh_terms: D000230:Adenocarcinoma / Q000737:chemistry* / Q000473:pathology; D000818:Animals; D002478:Cells, Cultured; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000032:analysis* / Q000378:metabolism; D005347:Fibroblasts / Q000737:chemistry* / Q000166:cytology; D007680:Kidney Neoplasms / Q000737:chemistry* / Q000473:pathology; D007700:Kinetics; D057230:Limit of Detection; D008156:Luciferases / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D013058:Mass Spectrometry; D008546:Melanoma, Experimental / Q000737:chemistry* / Q000473:pathology; D051379:Mice; D008856:Microscopy, Fluorescence
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide; D008156:Luciferases