Biosafety of micron-sized Fe₃O₄ magnetic fluid for pulmonary injection: a preclinical study toward lung nodule...

Fe₃O₄ magnetic fluid has shown great potential in various biomedical applications, including lesion localization, targeted therapy, and drug delivery, owing to its favorable biocompatibility and magnetic responsiveness. However, its safety for pulmonary nodule localization remains poorly understood, which limits its clinical translation.

This study evaluated the safety of micron-sized Fe₃O₄ magnetic fluid as a lung nodule marker in New Zealand rabbits. The fluid was encapsulated with sodium alginate into a porous structure. Rabbits were divided into an experimental group (injected with magnetic fluid, n=15) and a control group (injected with saline, n=15). Blood tests and serum biochemical indicators were used to assess cardiac, hepatic, and renal function. Tissue distribution was examined via hematoxylin-eosin (HE) and Prussian blue staining.

All blood parameters in the experimental group remained within physiological reference ranges, with no significant differences compared with the control group at any time point (P>0.05). Prussian blue staining confirmed that the magnetic fluid was strictly confined to the injection site in the lung and was not detected in the heart, liver, spleen, or kidneys. No obvious inflammatory infiltration, necrosis, or structural damage was observed in any major organs of the experimental group by HE staining.

The study concludes that micron-sized Fe₃O₄ magnetic fluid is safe for lung nodule localization in rabbits, causing no damage to the lungs or other organs.