The increased applications of nanoparticles in a wide range of industrial fields raise the concern about their potential toxicity to human. The aim of this study was to assess and compare the toxicity of four different oxide nanoparticles (Al2O3, CeO2, TiO2 and ZnO) to human lung epithelial cells, A549 carcinoma cells and L-132 normal cells, in vitro. We focused on the toxicological effects of the present nanoparticles on cell proliferation, cell viability, membrane integrity and oxidative stress. The long-term cytotoxicity of nanoparticles was also evaluated by employing the clonogenic assay. Among four nanoparticles tested, ZnO exhibited the highest cytotoxicity in terms of cell proliferation, cell viability, membrane integrity and colony formation in both cell lines. Al2O3, CeO2 and TiO2 showed little adverse effects on cell proliferation and cell viability. However, TiO2 induced oxidative stress in a concentration- and time-dependent manner. CeO2 caused membrane damage and inhibited colony formation in long-term, but with different degree depending on cell lines. Al2O3 seems to be less toxic than the other nanoparticles even after long time exposure. These results highlight the need for caution during manufacturing process of nanomaterials as well as further investigation on the toxicity mechanism.
Anionic nanoclays, so-called layered double hydroxide (LDH) nanoparticles, have been extensively applied as drug delivery systems, since they efficiently enter cells via endocytosis pathway and possess controlled release property. However, the stability of LDHs varies, depending on the type of interlayer anions, which can also affect their toxicity. In this study, we investigated the effects of two different forms of LDH, carbonate form (MgAl-LDH-CO3) and chloride form (MgAl-LDH-Cl), on cytotoxicity in human lung epithelial cells. The result showed that MgAl-LDH-Cl was more easily dissolved into metal ions under simulated lysosomal (pH 4.5) and body fluid (pH 7.4) conditions than did MgAl-LDH-CO3. According to cytotoxicity evaluation, MgAl-LDH-CO3 exhibited high toxicity compared with MgAl-LDH-Cl in terms of induction of oxidative stress, apoptosis and membrane damage. These results suggest that easily dissoluble MgAl-LDH-Cl has low cytotoxicity, while high stability of MgAl-LDH-CO3 is correlated to elevated cytotoxicity.
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