The effect of nano-TiO photocatalysis on the antioxidant activities of Cu, Zn-SOD at physiological pH.

Security issues of nanoparticles on biological toxicity and potential environmental risk have attracted more and more attention with the rapid development and wide applications of nanotechnology. In this work, we explored the effect and probable mechanism of nano-TiO on antioxidant activity of copper, zinc superoxide dismutase (Cu, Zn-SOD) under natural light and mixed light at physiological pH. Nano-TiO was prepared by sol-hydrothermal method, and then characterized by X-ray Diffraction (XRD) and Transmission electron micrographs (TEM). The Cu, Zn-SOD was purified by sephadex G75 chromatography and qualitatively analyzed by sodium dodecyl sulfate polypropylene amide gel electrophoresis (SDS-PAGE). The effect and mechanism were elucidated base on Fourier Transform Infrared Spectrometer (FT-IR), Circular Dichroism (CD), zeta potential, and electron spin resonance (ESR) methods. Accompanying the results of FT-IR, CD and zeta potential, it could be concluded that nano-TiO had no effect on the antioxidant activity of Cu, Zn-SOD by comparing the relative activity under natural light at physiological pH. But the relative activity of Cu, Zn-SOD significantly decreased along with the increase of nano-TiO concentration under the mixed light. The results of ESR showed the cause of this phenomenon was the Cu(II) in the active site of Cu, Zn-SOD was reduced to Cu(I) by HO and decreased the content of active Cu, Zn-SOD. The reduction can be inhibited by catalase. Excess O produced by nano-TiO photocatalysis under mixed light accumulated a mass of HO through disproportionation reaction in this experimental condition. The results show that nano-TiO cannot affect the antioxidant activity of Cu, Zn-SOD in daily life. The study on the effect of nano-TiO on Cu, Zn-SOD will provide a valid theory support for biological safety and the toxicological effect mechanism of nanomaterials on enzyme.