Magnetic labeling of non‐phagocytic adherent cells with iron oxide nanoparticles: a comprehensive study

Abstract

Small particles of iron oxide (SPIO) and ultrasmall particles of iron oxide (USPIO), inducing a strong negative contrast on T(2) and T(2)*-weighted MR images, are the most commonly used systems for the magnetic labeling of cultured cells and their subsequent detection by magnetic resonance imaging (MRI). The purpose of this work is to study the influence of iron incubation concentration, nanoparticle size and nanoparticle coating on the magnetic labeling and the viability of non-phagocytic adherent cells in culture. The magnetic labeling of 3T6 fibroblasts was studied by T(2)-weighted MRI at 4.7 T and by dosing-or cytochemical revealing-of iron through methods based on Perl's Prussian blue staining. Cells were incubated for 48 h with increasing iron concentrations of SPIO (25-1000 microg Fe/ml Endorem. Sinerem, a USPIO (20-40 nm) coated with neutral dextran, and Resovist (65 nm), a SPIO bearing an anionic carboxydextran coating, were compared with Endorem (dextran-coated, 80-150 nm) as magnetic tags. The iron loading of marrow stromal cell primary cultures (MSCs) isolated from rat femurs was compared with that of 3T6 fibroblasts. The SPIO-labeling of cells with Endorem was found to be dependent on the iron incubation concentration. MSCs, more sparsely distributed in the culture, exhibited higher iron contents than more densely populated 3T6 fibroblast cultures. A larger iron loading was achieved with Resovist than with Endorem, which in turn was more efficient than Sinerem as a magnetic tag. The magnetic labeling of cultured non-phagocytic adherent cells with iron oxide nanoparticles was thus found to be dependent on the relative concentration of the magnetic tag and of the cells in culture, on the nanoparticle size, and on the coating type. The viability of cells, estimated by methods assessing cell membrane permeability, was not affected by magnetic labeling in the conditions used in this work.

Labeling of Luciferase/eGFP-Expressing Bone Marrow-Derived Stromal Cells with Fluorescent Micron-Sized Iron Oxide Particles Improves Quantitative and Qualitative Multimodal Imaging of Cellular Grafts In Vivo

“…1a), which is in accordance with previous cell labeling studies using other MPIOs [18][19][20]. The particle size (1.63 μm) in combination with the anionic surface (carboxyl substitutes) is suggested to facilitate the endocytotic uptake of these particles by non-phagocytic cells as compared to smaller dextran-coated particles [21][22][23], which mostly need the addition of a transfection agent to achieve a high labeling efficiency. Although these MPIOs are endocytosed very fast (0.5-1 h) by phagocytic cells (e.g., macrophages, dendritic cells; data not shown), BMSC cultures need overnight incubation with MPIO particles for efficient cell labeling.…”

In vivo visualization of transplanted pancreatic islets by MRI: comparison between in vivo, histological and electron microscopy findings

“…In the present study we used 72 h labeling time because it did not affect islet viability (see Fig. 1 is probably attributable to its higher concentration in our culture medium, as well as to its higher relaxivity and its coating, which should enable the particles to establish stronger electrostatic interactions with the cell membranes (32). On the other hand, we have no definite explanation for the higher toxicity of Endorem 1 .…”

Assessing cytotoxicity of (iron oxide‐based) nanoparticles: an overview of different methods exemplified with cationic magnetoliposomes

“…, which vary in size and nature of the dextran molecules (3)(4)(5). To establish an efficient cellular uptake, these types of particles do present some important drawbacks, such as the need for cationic transfection agents, leading to complexes with non-controllable physico-chemical characteristics (6,7).…”