Kidney-targeted therapies often present poor pharmacokinetic profiles, with low delivery and retention. However, magnetic nanoparticles (MNP) have been successfully used in various fields to localize therapies to a target organ. In this study we aimed to investigate the renal retention of iron oxide fluorescent MNP in the presence of a magnetic field gradient localized to the kidneys.

 

MNP were administered to C57BL/6 mice intravenously (IV; 6.5 µg MNP/g body weight) via the retro-orbital vein, or locally to the left kidney (1.3 µg MNP/g body weight) via the renal vein or the ureter. Mice were randomly assigned to non-magnetic control conditions or placed for 1 hour with an external Neodymium-N42 magnet localized to both kidneys or the injected kidney, respectively. After 1 hour, mice were sacrificed and the fluorescence in various organs, including brain, lungs, heart, liver, kidneys, spleen and bladder, was measured using the Photonimager Optima system (Biospace Lab).

 

The results showed that MNP accumulation in the kidneys significantly increased 1 hour after intravenous administration with the application of an external magnetic field. Additionally, MNP accumulation in the injected kidney was significantly higher than in other organs after ureteral administration and after renal vein administration, except for the lungs. However, no differences were observed between magnetic and non-magnetic conditions.

 

These findings demonstrate that an external magnetic field can significantly increase renal MNP accumulation after IV administration. The results imply that MNP could be a promising approach for delivering therapies to the kidneys, but further research is required to optimize this therapy.