Glucose coating tunes the catalytic reactivity of FeO@Fe 3 O 4 for biomedical applications: safety assessment using a 3D hepatic in vitro model

Iron-oxide magnetic nanoparticles (MNPs) have been extensively investigated as magnetically actuable nanocatalysts for diagnostic and therapeutic applications. However, because wüstite/magnetite/maghemite phases can interconvert, coexisting Fe ²⁺ /Fe ³⁺ species may redirect Fenton-like chemistry and generate reactive oxygen species (ROS) profiles that differ from the intended biocatalytic pathway. Here we investigate monodisperse biphasic FeO@Fe ₃ O ₄ core-shell MNPs with average particle size ⟨d⟩ = 9.6(5) nm, and their glucose-coated analogue, combining EPR radical analysis with toxicity testing in a 3D HepG2 hepatic spheroid model. Naked particles exhibited conventional Fenton-like behavior dominated by hydroxyl radicals (•OH), whereas glucose coating markedly suppressed •OH while increasing hydroperoxyl radicals (•OOH; ≈55 pM at 60 min), demonstrating ligand-controlled rerouting of the radical pathway. TEM mapping across spheroid cross sections showed preferential MNP accumulation in the outer layer, with most MNPs remaining within the outer ∼10–15 µm, which defines a one-cell rim; sparse events were detected deeper, up to ∼30 µm. Exposure of the HepG2 cells to the MNPs produced a dose- and time-dependent cytotoxicity with IC₅₀ values of 29.3 (24 h) and 10.8 (96 h) µg·cm⁻², but without measurable oxidative stress or genotoxicity: MDA levels were unchanged, comet assay signals did not increase significantly, and gH2AX and phospho-H3 (p-H3) remained at baseline. Therefore, glucose functionalization provides a simple route to modulate radical pathways and define operational windows for redox-active FeO@Fe ₃ O ₄ nano-reactors in oxidative nanomedicine.