Magnetic microspheres can be used for magnetic particle imaging of cancer cells arrested in the mouse brain

Cell labeling with magnetic nanoparticles (MNPs) is a promising method of cell tracking. In particular, a novel quantitative tomography method called magnetic particle imaging (MPI) has the potential to estimate the number of successfully transplanted MNP-labeled cells, thereby helping predict clinical outcomes. However, the biological factors that shape the MPI signals of MNPs during cell labeling are not well understood. To better understand these factors, the MPI signals of MNPs in various extracellular and intracellular conditions were assessed. Firstly, carboxydextran-coated MNPs (Resovist®) in the presence or absence of the transfection agents heparin and/or protamine were subjected to dynamic light scattering analysis and magnetic particle spectroscopy. Secondly, RAW264 macrophages and Colon26 carcinoma cells were labeled with Resovist® by using their intrinsic phagocytic activity or with the assistance of the transfection agents, respectively, after which the cells were visualized by our MPI scanner and transmission electron microscopy, and their absolute amounts of intracellular iron were measured by thiocyanate colorimetry. The MPI pixel values were normalized to intracellular iron concentrations. Finally, the effect of cell lysis on the MPI signal was assessed with magnetic particle spectroscopy. The presence of protamine, but not heparin, increased the hydrodynamic diameter of the MNPs and inhibited their MPI signals. Cell uptake drastically decreased the normalized MPI pixel values. This was particularly marked in the colon cancer cells. The transfection agents did not further alter the MPI signal of the MNP-labeled colon cancer cells. Transmission electron microscopy showed that there was much more MNP aggregation in colon cancer cells than in macrophages. After the MNP-labeled cells were lysed, the MPI signal recovered partially. In conclusion, MPI pixel values can be influenced by the cell-labeling process and cellular uptake. The MPI signals from intracellular magnetic nanoparticles may also differ depending on the cell type.

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Design of a head coil for high resolution mouse brain perfusion imaging using magnetic particle imaging

Physics in Medicine and Biology ◽

10.1088/1361-6560/abc09e ◽

2020 ◽

Vol 65 (23) ◽

pp. 235007

Author(s):

Matthias Graeser ◽

Peter Ludewig ◽

Patryk Szwargulski ◽

Fynn Foerger ◽

Tom Liebing ◽

...

Keyword(s):

High Resolution ◽

Mouse Brain ◽

Perfusion Imaging ◽

Magnetic Particle ◽

Brain Perfusion ◽

Magnetic Particle Imaging ◽

Brain Perfusion Imaging ◽

Particle Imaging ◽

Head Coil

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The sensitivity of magnetic particle imaging and fluorine-19 magnetic resonance imaging for cell tracking

Scientific Reports ◽

10.1038/s41598-021-01642-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Olivia C. Sehl ◽

Paula J. Foster

Keyword(s):

Breast Cancer ◽

Cancer Cells ◽

Breast Cancer Cells ◽

Cell Tracking ◽

Magnetic Particle ◽

Ex Vivo ◽

Cell Detection ◽

Magnetic Particle Imaging ◽

Particle Imaging

AbstractMagnetic particle imaging (MPI) and fluorine-19 (19F) MRI produce images which allow for quantification of labeled cells. MPI is an emerging instrument for cell tracking, which is expected to have superior sensitivity compared to 19F MRI. Our objective is to assess the cellular sensitivity of MPI and 19F MRI for detection of mesenchymal stem cells (MSC) and breast cancer cells. Cells were labeled with ferucarbotran or perfluoropolyether, for imaging on a preclinical MPI system or 3 Tesla clinical MRI, respectively. Using the same imaging time, as few as 4000 MSC (76 ng iron) and 8000 breast cancer cells (74 ng iron) were reliably detected with MPI, and 256,000 MSC (9.01 × 1016 19F atoms) were detected with 19F MRI, with SNR > 5. MPI has the potential to be more sensitive than 19F MRI for cell tracking. In vivo sensitivity with MPI and 19F MRI was evaluated by imaging MSC that were administered by different routes. In vivo imaging revealed reduced sensitivity compared to ex vivo cell pellets of the same cell number. We attribute reduced MPI and 19F MRI cell detection in vivo to the effect of cell dispersion among other factors, which are described.

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The sensitivity of magnetic particle imaging and fluorine-19 magnetic resonance imaging for cell tracking

10.1101/2021.08.31.458286 ◽

2021 ◽

Author(s):

Olivia C. Sehl ◽

Paula J. Foster

Keyword(s):

Breast Cancer ◽

Cancer Cells ◽

Breast Cancer Cells ◽

Cell Tracking ◽

Magnetic Particle ◽

Ex Vivo ◽

Cell Detection ◽

Magnetic Particle Imaging ◽

Particle Imaging

AbstractPurposeMagnetic particle imaging (MPI) and fluorine-19 (19F) MRI produce images which allow for quantification of labeled cells. MPI is an emerging instrument for cell tracking, which is expected to have superior sensitivity compared to 19F MRI. Our objective is to assess the cellular sensitivity of MPI and 19F MRI for detection of mesenchymal stem cells (MSC) and breast cancer cells.MethodsCells were labeled with ferucarbotran or perfluoropolyether, for imaging on a preclinical MPI system or 3 Tesla clinical MRI, respectively. In vivo sensitivity with MPI and 19F MRI was evaluated by imaging MSC that were administered by different routes.ResultsUsing the same imaging time, as few as 4000 MSC (76 ng iron) and 8000 breast cancer cells (74 ng iron) were reliably detected with MPI, and 256,000 MSC (9.01 × 101619F atoms) were detected with 19F MRI, with SNR > 5. In vivo imaging revealed reduced sensitivity compared to ex vivo cell pellets of the same cell number.ConclusionMPI has the potential to be more sensitive than 19F MRI for cell tracking. We attribute reduced MPI and 19F MRI cell detection in vivo to the effect of cell dispersion among other factors, which are described.

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