Following meticulous characterization of Cur CeO
2-NZs, a comprehensive set of cellular and animal experiments was conducted to evaluate their biocompatibility, therapeutic efficacy, and safety profiles. The cellular uptake of these Cur CeO
2-NZs was first assessed using fluorescence microscopy after treating A549 lung epithelial cells and RAW264.7 macrophages with FITC-labeled Cur CeO
2-NZs at various culturing intervals. A time-dependent increase in cellular uptake was observed, affirming efficient internalization of the Cur CeO
2-NZs and potential for intracellular therapeutic action (
Fig. 2A and Fig. S5 in Supporting information). To extend these observations
in vivo, mice were administered Cy5.5-labeled Cur CeO
2-NZs
via tracheal nebulization. All animal procedures performed in this study were in accordance with the ethical guidelines approved by the Animal Care and Use Committee of Naval Medical University (approval No. 20210310013). Subsequent organ harvesting and imaging demonstrated pronounced fluorescence in lung tissues immediately after administration, with detectable fluorescence persisting for up to 48 h. This indicates the sustained bioavailability and effectiveness of Cur CeO
2-NZs when administered through nebulization, showing prolonged engagement with the lung tissue (
Fig. 2B and Fig. S6 in Supporting information). The biocompatibility of Cur CeO
2-NZs was further explored by evaluating their cytotoxicity in A549 cells at varying concentrations over a 24 h period using a cell counting kit-8 (CCK-8) assay. Results indicated negligible cytotoxicity, even at concentrations as high as 100 µg/mL, with cell viabilities exceeding 80%. Similar non-toxic profiles were observed in RAW264.7 cells, suggesting that Cur CeO
2-NZs do not interfere with cellular growth (Fig. S7 in Supporting information). Animal studies were conducted to assess the
in vivo safety of Cur CeO
2-NZs administered
via tracheal nebulization. Subsequent pathological analyses of vital organs at 48 h and 14 d post-administration revealed no abnormal histopathological changes, confirming the safety profile of Cur CeO
2-NZs (Figs. S8 and S9 in Supporting information). In the cell, the site of ROS generation is the mitochondria, and the nanoenzymes enter the cell; according to the nature of CeO
2, they can be targeted toward the mitochondria to scavenge ROS (Fig. S10 in Supporting information). The protective efficacy of the Cur CeO
2-NZs against oxidative stress was investigated using a
t-BHP-induced oxidative damage model in A549 cells. The half maximal inhibitory concentration (IC
50) value of
t-BHP was used as the concentration (Fig. S11 in Supporting information). Treatment with Cur CeO
2-NZs significantly mitigated intracellular ROS levels, outperforming Cur and CeO
2-NZs alone, indicating their superior antioxidant properties (
Fig. 2C and Fig. S12 in Supporting information). Additionally, Cur CeO
2-NZs effectively preserved the mitochondrial membrane potential under oxidative stress, demonstrating enhanced protective effects on mitochondrial integrity compared with those of the control treatments (
Fig. 2D and Fig. S13 in Supporting information). Furthermore, Cur CeO
2-NZs significantly reduced
t-BHP-induced apoptosis, demonstrating their potential to prevent cell death (
Fig. 2E and Fig. S14 in Supporting information). In an
in vitro inflammation model using lipopolysaccharides (LPS)-stimulated RAW264.7 cells, Cur CeO
2-NZs markedly downregulated pro-inflammatory cytokines (tumor necrosis factor-alpha (TNF-
α), interleukin-6 (IL-6), IL-1
β) and upregulated anti-inflammatory cytokines IL-10 compared with controls, highlighting their anti-inflammatory capabilities (
Fig. 2F). Collectively, these findings suggest that Cur CeO
2-NZs not only exhibit promising biocompatibility and safety both
in vitro and
in vivo but also demonstrate significant protective effects against oxidative stress and inflammation, positioning them as potent therapeutic agents for lung epithelial protection and inflammation mitigation.