We present the MR properties of a novel bio-responsive phosphorus probe doped with iron for dual proton and phosphorus magnetic resonance imaging (1H/31P-MRI), which provide simultaneously complementary information. The probes consist of non-toxic biodegradable calcium phytate (CaIP6) nanoparticles doped with different amounts of cleavable paramagnetic Fe3+ ions. Phosphorus atoms in the phytate structure delivered an efficient 31P-MR signal, with iron ions altering MR contrast for both 1H and 31P-MR. The coordinated paramagnetic Fe3+ ions broadened the 31P-MR signal spectral line due to the short T2 relaxation time, resulting in more hypointense signal. However, when Fe3+ was decomplexed from the probe, relaxation times were prolonged. As a result of iron release, intensity of 1H-MR, as well as the 31P-MR signal increase. These 1H and 31P-MR dual signals triggered by iron decomplexation may have been attributable to biochemical changes in the environment with strong iron chelators, such as bacterial siderophore (deferoxamine). Analysing MR signal alternations as a proof-of-principle on a phantom at a 4.7 T magnetic field, we found that iron presence influenced 1H and 31P signals and signal recovery via iron chelation using deferoxamine.

Department of Diagnostic and Interventional Radiology MR unit Institute for Clinical and Experimental Medicine Prague Czech Republic

Faculty of Mechatronics Informatics and Interdisciplinary Studies Technical University of Liberec Liberec Czech Republic

Institute of Biophysics and Informatics 1st Faculty of Medicine Charles University Prague Czech Republic

Institute of Macromolecular Chemistry Czech Academy of Sciences Prague Czech Republic

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