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Capacity of human monocytes to phagocytose approved iron oxide MR contrast agents in vitro
Stephan Metz1, Gabriel Bonaterra, Martina Rudelius
1Department of Diagnostic Radiology, Technical University Munich, Munich, Germany. smetz@roe.med.tu-muenchen.de
Abstract:
To evaluate the capacity of human monocytes to phagocytose various approved iron oxide based magnetic resonance (MR) contrast agents and to optimize in vitro labeling of these cells. Human monocytes were incubated with two superparamagnetic iron oxide particles (SPIO) as well as two ultrasmall SPIO (USPIO) at varying iron oxide concentrations and incubation times. Iron uptake in monocytes was proven by histology, quantified by atomic emission absorption spectrometry and depicted with T2* weighted fast field echo (FFE) MR images at 1.5 T. Additionally, induction of apoptosis in iron oxide labeled monocytes was determined by YO-PRO-1 staining. Cellular iron uptake was significantly (P<0.01) higher after incubation with SPIO compared with USPIO. For SPIO, the iron oxide uptake was significantly (P<0.01) higher after incubation with the ionic Ferucarbotran as compared with the non-ionic Ferumoxides. Efficient cell labeling was achieved after incubation with Ferucarbotran at concentrations > or = 500 microg Fe/ml and incubation times > or = 1 h, resulting in a maximal iron oxide uptake of up to 50 pg Fe/cell without impairment of cell viability. In vitro labeling of human monocytes for MR imaging is most effectively obtained with the approved SPIO Ferucarbotran. Potential subsequent in vivo cell tracking applications comprise, e.g. specific targeting of inflammatory processes.
Insights
Superparamagnetic iron oxide nanoparticles (SPIO) effectively label human monocytes for MRI. Ferucarbotran, an SPIO, shows superior iron uptake without harming cell viability, enabling potential in vivo cell tracking.
Area of Science:
- Biomedical Engineering
- Nanotechnology
- Cell Biology
Background:
- Magnetic resonance (MR) imaging requires effective contrast agents for cellular labeling.
- Iron oxide nanoparticles offer potential for MR contrast enhancement and cell tracking.
- Human monocytes play a crucial role in inflammatory processes and immune responses.
Purpose of the Study:
- To assess the phagocytic capacity of human monocytes for various iron oxide-based MR contrast agents.
- To optimize in vitro labeling protocols for human monocytes using these agents.
- To determine the most effective SPIO for monocyte labeling for subsequent MR imaging applications.
Main Methods:
- Human monocytes were incubated with superparamagnetic iron oxide particles (SPIO) and ultrasmall SPIO (USPIO) at varying concentrations and durations.
- Iron uptake was quantified using atomic emission absorption spectrometry and visualized with T2*-weighted MR imaging.
- Cell viability was assessed via YO-PRO-1 staining to detect apoptosis.
Main Results:
- Monocytes exhibited significantly higher iron uptake with SPIO compared to USPIO (P<0.01).
- Ionic Ferucarbotran (SPIO) resulted in greater iron uptake than non-ionic Ferumoxides (SPIO) (P<0.01).
- Optimal labeling with Ferucarbotran was achieved at >= 500 microg Fe/ml and >= 1 h incubation, yielding up to 50 pg Fe/cell without impairing viability.
Conclusions:
- In vitro labeling of human monocytes for MR imaging is most effectively achieved using the SPIO Ferucarbotran.
- Ferucarbotran labeling enhances monocyte visibility in MR imaging.
- This optimized labeling technique holds promise for in vivo cell tracking, particularly for inflammatory processes.
