Boron Nitride Nanotubes as T-2-Weighted MRI Contrast Agents

Boron nitride nanotubes (BNNTs) showing superparamagnetic properties due to the presence of Fe nanoparticles attached to one end as residues of the solid-state preparation procedure were tested as potential T-2 contrast agents for proton MRI. Measurements of longitudinal and transverse relaxation times of water protons in homogeneous aqueous dispersions of BNNTs wrapped with poly(L-lysine) at different concentrations allowed longitudinal (r(1)) and transverse (r(2)) relaxivities to be determined at magnetic field strengths of 1.5 and 7.05 T. The r(2) value was higher than those of commercial superparamagnetic iron oxide nanoparticles at 1.5 T and considerably increased at the higher magnetic field investigated. On the basis of the obtained results, Fe containing BNNTs have the potential to be more powerful T-2 contrast-enhancement agents than the currently used ones.