Enhanced magnetic delivery of superparamagnetic iron oxide nanoparticles to the lung monitored using noninvasive MR

This study aimed to improve the targeting of superparamagnetic iron oxide nanoparticles (SPI-ONs) to the lung after intravenous administration. In order to achieve a higher pulmonary delivery, high-energy flexible magnets were optimized and externally applied to a specific region of mouse lung. SPIONs and magnets were first characterized, and a free-breathing magnetic resonance imaging (MRI) protocol was then optimized to allow noninvasive monitoring and for their sensitive detection to the target site in the lung, using an ultrashort time of echo radial MR pulse sequence. In addition, histological analysis using Perls' staining and iron quantification using inductive couple plasma-mass spectroscopy (ICP-MS) were performed to confirm MRI readouts. A flexible magnet with inverse multiple polarities was found to enhance the magnetic targeting of SPIONs to the lung. MRI readouts enabled successful detection of enhanced SPION migration to the lower right lobe, where the magnet was positioned. Attracted by the magnet, SPIONs were found to accumulate in the lung tissue within 2 h post-injection as seen in histological images and through ICP-MS, where a notable increase in iron concentrations were observed in the magnet group compared to control mice. In conclusion, the external application of an optimized high-energy magnet with multiple polarities over specific regions of the lung enhanced the magnetic targeting of SPIONs to the site of interest within the lung after intravenous injection.