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Updated: Jun 20, 2026
Using Magnetometry to Monitor Cellular Incorporation and Subsequent Biodegradation of Chemically Synthetized Iron Oxide Nanoparticles
Published on: February 27, 2021
Quantitative effects of cell internalization of two types of ultrasmall superparamagnetic iron oxide nanoparticles at
J-C Brisset1, V Desestret, S Marcellino
1Université de Lyon, Lyon 1, Lyon 69003, France.
Purpose:
MRI coupled with the intravenous injection of ultrasmall superparamagnetic particles of iron oxides (USPIOs) is a promising tool for the study of neuroinflammation. Quantification of the approximate number of magnetically labelled macrophages may provide an effective and efficient method for monitoring inflammatory cells. The purpose of the present study was to characterise the relaxation properties of macrophages labelled with two types of USPIOs, at 4.7 T and 7 T.
Methods:
USPIO-labelled bone-marrow-derived macrophage phantoms were compared with phantoms of free dispersed USPIOs with the same global iron concentration, using multi-parametric (T1, T2 and T2) quantitative MRI. The same protocol was then evaluated in living mice after intracerebral injection of iron-labelled macrophages vs free iron oxide.
Results:
A linear relationship was observed among R1, R2 and R2 values and iron concentration in vitro at 4.7 T and at 7 T. At a given field, T1 and T2 relaxivities of both types of USPIOs decreased following internalisation into macrophages, while T2 relaxivities increased.
Conclusion:
There was fair overall agreement between the theoretical number of injected cells and the number estimated from T2 quantification and in vitro calibration curves, supporting the validity of the present in vitro calibration curves for in vivo investigation.
Insights
Quantifying magnetically labeled macrophages using ultrasmall superparamagnetic particles of iron oxides (USPIOs) can monitor neuroinflammation. In vitro calibration curves for T2 quantification show promise for in vivo studies.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Neuroinflammation Research
- Cellular Imaging
Background:
- Ultrasmall superparamagnetic particles of iron oxides (USPIOs) enable MRI visualization of neuroinflammation.
- Quantifying magnetically labeled macrophages is crucial for monitoring inflammatory cells.
- Understanding USPIO relaxation properties in macrophages is key for accurate quantification.
Purpose of the Study:
- Characterize relaxation properties of macrophages labeled with two USPIO types.
- Evaluate USPIOs at 4.7 T and 7 T magnetic field strengths.
- Assess the accuracy of USPIO-based cell quantification for in vivo applications.
Main Methods:
- Compared USPIO-labeled macrophage phantoms with free USPIO phantoms using multi-parametric quantitative MRI (T1, T2, T2*).
- Evaluated the protocol in living mice after intracerebral injection of labeled macrophages versus free iron oxide.
- Determined relaxivity (R1, R2, R2*) changes upon macrophage internalization.
Main Results:
- Established a linear relationship between R1, R2, R2* values and iron concentration in vitro at both 4.7 T and 7 T.
- Observed decreased T1 and T2 relaxivities but increased T2 relaxivities after USPIO internalization into macrophages.
- Demonstrated fair agreement between theoretical and estimated cell numbers using T2 quantification.
Conclusions:
- In vitro calibration curves using T2 quantification are valid for in vivo studies of USPIO-labeled macrophages.
- This method provides a reliable approach for estimating the number of inflammatory cells in vivo.
- USPIO-based MRI offers an efficient tool for monitoring neuroinflammation.
