Physiochemical characteristics contributing to the cytotoxicity of transition metal oxides

In the past ten years nanotechnology has not only evolved to play a prominent role in our economy but also increased the concern over potential adverse effects caused by nanomaterials to human health and the environment. Nanotoxicity is to understand the nature and origin of the toxicity imposed by nanomaterials. Studies from our laboratory have shown that nanoparticle induces oxidative stress, perturbs calcium homeostasis, alter gene expression, and produces pro-inflammatory responses. We also identified a trend of toxicity: TiO₂ \u3c Cr₂O₃ \u3c Fe₂O₃ \u3c Mn₂O₃ \u3c NiO \u3c ZnO \u3c CuO. We then asked a question: what are physiochemical factors of transition metal nanoparticles that contributed to this increasing cytotoxicity. In this thesis I investigated the correlation between physicochemical properties and toxicity of the transition metal oxides in the 4th Period of the Periodic Table of Elements. Particle size, BET surface area, point of zero charge, metal dissolution, and degree of surface adsorption of transition metal oxide nanoparticles were measured. There were no increasing trends in both particle size and specific surface area. The point of zero charge showed an increasing trend as TiO₂ \u3c Cr₂O₃ \u3c Fe₂O₃ \u3c NiO \u3c CuO = ZnO \u3c Mn₂O₃. The number of available binding sites of nanoparticle showed an increasing trend as Cr₂O₃ \u3e ZnO \u3e CuO \u3e NiO \u3e Fe₂O₃ \u3e Mn₂O₃ \u3e TiO₂. The degree of adsorption on the surface of nanoparticles showed an increasing trend with atomic number, with the exception of Cr₂O₃. The degree of dissolution of transition metal oxides increases with atomic number. In summary, the factors that contribute to cytotoxicity of transition metal oxides were a combination of point of zero charge, number of available binding sites on the surface of nanoparticles, and metal dissolution. This study advances our understanding in mechanisms of nanotoxicity, which may lead to safer design of nanomaterials --Abstract, page iii