Quantitative intracellular magnetic nanoparticle uptake measured by live cell magnetophoresis

Abstract

Superparamagnetic iron oxide (SPIO) particles have been used successfully as an intracellular contrast agent for nuclear MRI cell tracking in vivo. We present a method of detecting intracellular SPIO colloid uptake in live cells using cell magnetophoresis, with potential applications in measuring intracellular MRI contrast uptake. The method was evaluated by measuring shifts in mean and distribution of the cell magnetophoretic mobility, and the concomitant changes in population frequency of the magnetically positive cells when compared to the unmanipulated negative control. Seven different transfection agent (TA) -SPIO complexes based on dendrimer, lipid, and polyethylenimine compounds were used as test standards, in combination with 3 different cell types: mesenchymal stem cells, cardiac fibroblasts, and cultured KG-1a hematopoietic stem cells. Transfectol (TRA) -SPIO incubation resulted in the highest frequency of magnetically positive cells (>90%), and Fugene 6 (FUG) -SPIO incubation the lowest, below that when using SPIO alone. A highly regular process of cell magnetophoresis was amenable to intracellular iron mass calculations. The results were consistent in all the cell types studied and with other reports. The cell magnetophoresis depends on the presence of high-spin iron species and is therefore expected to be directly related to the cell MRI contrast level.

Differences in Magnetic Particle Uptake by CNS Neuroglial Subclasses: Implications for Neural Tissue Engineering

“…However, there are critical gaps in our knowledge of fundamental parameters governing the utility of this emergent technology for CNS applications, especially the factors that determine MP uptake and intracellular processing in neural cells. The influence of parameters such as MP size, coating and charge on particle uptake have been studied in non-neural cell types [17][18][19][20] but the influence of neural cell subtype on particle uptake has never been assessed. This is especially pertinent when considering MP applications for CNS tissue; the latter is uniquely complex and contains several, specialist, interacting cell types meaning that data obtained from other physiological systems cannot be extrapolated to the CNS.…”

Tailoring the surface charge of dextran-based polymer coated SPIONs for modulated stem cell uptake and MRI contrast

“…Fixed cells are exposed to a magnetic field gradient and their migration towards the area with the highest magnetic field strength is imaged, from which their magnetic velocity can be obtained. 36,47 Fig. 5A shows how the magnetic velocity increases when MSCs are labelled with the SPIONs containing an increasing amount of DEAE within the shell.…”

Magnetically Responsive Bone Marrow Mesenchymal Stem Cell-Derived Smooth Muscle Cells Maintain Their Benefits to Augmenting Elastic Matrix Neoassembly

“…One way to achieve this is by guiding intra-aortally infused, magnetically responsive BM-SMCs into the AAA wall using an externally applied magnetic field. The BM-SMCs are rendered paramagnetic by SPION-labeling, [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]33 a strategy that has been applied to cell delivery to other tissue locations and facilitates their tracking using MRI. [34][35][36] In the context of our proposed use of BM-SMCs, in this study, we sought to ascertain how SPION-labeling influences phenotype and functionality of the BM-SMCs, including their proelastogenesis and antiproteolytic properties.…”

“…The responsiveness of SPION-BM-SMCs to a constant magnetic field gradient, applied orthogonal to gravity, 19 was estimated using cell tracking velocimetry (CTV) as per Zborowski and colleagues. 20 SPION-BM-SMCs (0.2, 0.5 and 1.0 mg/mL) were washed with sterile phosphate-buffered saline (PBS; Sigma-Aldrich) and resuspended at 2 · 10 6 cells/ mL of culture medium.…”

“…The magnetophoretic mobility of cells was calculated as cell velocity divided by the magnitude of the applied magnetic field gradient. 19 Impact of magnetic targeting on BM-SMC uptake into vessel wall Improved BM-SMC uptake into the vessel wall upon magnetic targeting was assessed ex vivo within matrixdisrupted porcine carotids (Lampire Biological Labs). The arteries were de-endothelialized using a guide wire, intraluminally infused with 20 U/mL porcine pancreatic elastase (Sigma-Aldrich) using a Scimed 5F catheter (SCIMED Life System) for 20 min at 37°C to disrupt the aortal elastic matrix, and then rinsed with sterile PBS.…”