Citrate-mediated differential modulation of cytotoxicity induced by nano-zero-valent iron and ferrous ions in human lung epithelial cells (A549)

Studies on the cytotoxicity of nZVI remain limited, and even fewer have examined how chelating agents modulate nZVI cytotoxicity. Here, we compared the cytotoxic mechanisms of nZVI and Fe²⁺ in mammalian A549 cells in the presence of sodium citrate (SC), a model chelating agent. nZVI mainly activated autophagy and necroptosis, possibly through direct contact with cells and intracellular internalization, leading to reduced ATP levels and S-phase arrest. By contrast, Fe²⁺ overload triggered a burst of reactive oxygen species (ROS), driving ferroptosis and G2-phase arrest. These processes caused cell membrane damage and ATP depletion, ultimately impairing cell proliferation. The expression of signature proteins associated with autophagy, necroptosis, and ferroptosis was markedly altered in the nZVI- and Fe²⁺-treated groups, confirming the activation of multiple cell death programs. SC exerted dual effects: it exacerbated nZVI cytotoxicity by increasing the zeta potential and thereby reducing electrostatic repulsion, whereas it mitigated Fe²⁺ toxicity by forming stable complexes that suppressed pro-oxidative stress and ferroptotic effects. This study provides comprehensive insights into the mechanistic differences between nZVI- and Fe²⁺-induced cytotoxicity and the modulatory role of chelators, offering guidance for the safe application of nZVI. Download: Download high-res image (174KB) Download: Download full-size image