[Magnetosomes as biological model for iron binding: relaxivity determination with MRI].

PURPOSE

In vitro characterization of iron-containing bacterial particles (magnetosomes) as superparamagnetic contrast agents for MRI.

MATERIAL AND METHODS

Different concentrations of magnetosomes were examined with a 1.5 T clinical whole-body MR system at 21 degrees C using the transit/receive extremity coil. Both longitudinal and transversal relaxivities (R1 and R2) of the magnetosomes were determined by an inversion recovery snapshot gradient recall echo (IR FLASH) with various inversion times and a multi echo spin echo sequence. Atomic absorption spectrometry (AAS) and electron microscopy were used as reference standard.

RESULTS

Longitudinal and transverse relaxivities of the magnetosomes were calculated to be R1 = 7.688 mmol -1 s -1 and R2 = 147.67 mmol -1 s -1, respectively. The corresponding iron concentrations were determined in all dilutions using AAS, while the magnetosomes were morphologically delineated by electron microscopy.

CONCLUSION

Magnetosomes represent a new and interesting class of iron-containing contrast agents warranting further evaluation in cellular cultures and animal models. Magnetosomes may be suited for displaying the vector distribution and gene expression of new molecular therapies.