MRI relaxation properties of water-soluble apoferritin-encapsulated gadolinium oxide-hydroxide nanoparticles

We have prepared water-soluble gadolinium oxide nanoparticles that show potential as MRI contrast
agents. The particles were built into the apoferritin cavity and have an average size of 5 nm. After
seven days a loss of 5% of Gd was detected compared with the as-prepared samples; after that the Gd
remained constant and stabilized inside the apoferritin, indicating that the apoferritin capsid acts as a
Gd store, avoiding metal delivery and consequent toxicity. The NMR longitudinal and transverse
relaxivities resulted about 10 and 70 times higher than the ones of clinically approved paramagnetic
Gd-chelates, thus indicating the possible route for synthesizing a novel class of MRI contrast agents.