Magnetic Nanoparticles in Macrophages and Cancer Cells Exhibit Different Signal Behavior on Magnetic Particle Imaging

Area of Science:

• Biomedical Engineering
• Nanotechnology
• Cell Biology

Background:

• Cell labeling with magnetic nanoparticles (MNPs) is crucial for cell tracking.
• Magnetic Particle Imaging (MPI) offers quantitative cell counting for predicting clinical outcomes.
• Biological factors influencing MPI signals during cell labeling require further investigation.

Purpose of the Study:

• To investigate the impact of extracellular and intracellular conditions on MPI signals of MNPs.
• To understand how cell labeling processes and cellular uptake affect MPI signal quantification.
• To explore cell-type-specific differences in MPI signals of intracellular MNPs.

Main Methods:

• Dynamic light scattering and magnetic particle spectroscopy analyzed MNPs with and without transfection agents.
• RAW264 macrophages and Colon26 carcinoma cells were labeled with MNPs.
• MPI, transmission electron microscopy, and thiocyanate colorimetry assessed intracellular iron and MNP distribution.
• Cell lysis effects on MPI signals were evaluated.

Main Results:

• Protamine increased MNP hydrodynamic diameter and reduced MPI signals; heparin had no significant effect.
• Cellular uptake markedly decreased normalized MPI pixel values, especially in colon cancer cells.
• MNP aggregation was greater in colon cancer cells than in macrophages.
• Cell lysis partially restored MPI signals.

Conclusions:

• MPI signal quantification is influenced by MNP labeling procedures and cellular uptake mechanisms.
• Cell type heterogeneity affects MPI signal detection from intracellular MNPs.
• Further research is needed to optimize MNP labeling for accurate cell tracking via MPI.