Toxicity of ZnO nanoparticles (NPs) with or without hydrophobic surface coating to THP-1 macrophages: interactions with BSA or oleate-BSA.

It is recently shown that biological macromolecules in food could interact with nanoparticles (NPs) and consequently change the biological effects of NPs. In this study, the interactions between ZnO NPs with or without hydrophobic surface coating and bovine serum albumin (BSA) or oleate (OA) complexed to BSA (OA-BSA) were assessed. Atomic force microscope (AFM) showed topographic changes of both types of NPs by BSA or OA-BSA, which could indicate the formation of protein corona. ZnO NPs showed negative Zeta potential, which was slightly decreased by BSA or OA-BSA, with OA-BSA being more effective. The UV-Vis was increased, whereas the fluorescence and synchronous fluorescence was decreased by the presence of ZnO NPs. Exposure to both types of ZnO NPs was associated with cytotoxicity to THP-1 macrophages, which was equally mitigated by BSA or OA-BSA associated with decreased cellular Zn elements. Exposure to ZnO NPs was associated with decreased release of cytokines, which was not affected by BSA or OA-BSA. In combination, the results from this study suggested that both BSA and OA-BSA could be adsorbed to ZnO NPs regardless of hydrophobic surface coating, which reduced the cytotoxicity of NPs to macrophages probably due to reduced association between NPs and cells. BSA and OA-BSA equally protected THP-1 macrophages from ZnO NP exposure, which might indicate that complexation to OA did not compromise the cytoprotective effects of BSA. These data might also indicate the complex interaction between NPs and biological macromolecules as food components, which should be considered for future nanotoxicological studies.

The presence of oleate stabilized ZnO nanoparticles (NPs) and reduced the toxicity of aged NPs to Caco-2 and HepG2 cells.

The presence of food components may alter the colloidal aspects and toxicity of nanoparticles (NPs). In this study, the toxicity of ZnO NPs to Caco-2 and HepG2 cells was assessed, with the emphasis on the interactions between ZnO NPs and oleate (OA). The presence of OA increased UV-Vis spectra and hydrodynamic sizes, decreased Zeta potential, and markedly reduced the release of Zn ions from the dissolution of ZnO NPs, which combined indicated that OA could coat ZnO NPs and stabilize ZnO NPs. Exposure to ZnO NPs significantly induced cytotoxicity to Caco-2 and HepG2 cells, associated with increased intracellular Zn ions but not superoxide. When OA was added to the freshly prepared ZnO NP suspensions, the cytotoxicity, intracellular Zn ions and superoxide induced by ZnO NPs were not significantly affected. However, when ZnO NPs were aged for 24 h with the presence of OA, the cytotoxicity of ZnO NPs to Caco-2 and HepG2 cells was significantly reduced, associated with a reduction of intracellular Zn ions. The results from this study suggested that the presence of OA could increase colloidal stability of ZnO NPs and consequently reduce the toxicity of ZnO NPs after aging associated with reduced accumulation of intracellular Zn ions.