Biotoxicity Of TiO₂Nanoparticles/Nanotubes And Their Antibacterial Actions In PP Composite Materials

TiO₂nanomaterials were applied widely in various fields nowadays. TiO₂nanomaterials wouldbring more and more healthy and ecological damages to the society owing to the extensive andinevitable contact with biological systems and environment. In this study, we systematicallyinvestigated the TiO₂nanoparticles and nanotubes in vivo and in vitro biological toxicity as well as onprokaryotic microbial resistance and their mechanisms, and a further research on the antibacterialproperties and antibacterial mechanism of TiO₂nanoparticles as photocatalytic antibacterial agents inPP composite materials was carried out.The research work mainly includes the following aspects:（1） TiO₂nanoparticles and TiO₂nanotube samples were prepared by hydrothermal reaction andcharacterized by means of transmission electron microscope （TEM）, X ray diffraction （XRD）, Fouriertransformed infrared spectrum （FT-IR） and Raman spectrum （Raman）, respectively. The resultsshowed that the diameters of as-prepared nanoparticles and nanotubes were about50nm and10nmwith about200nm in length. The crystal form of TiO₂nanoparticles were homogeneous anatase andTiO₂nanotube was mixed crystal with anatase and rutile. And the other modification groups were notfound on the surface of nano TiO₂.（2） The biological toxicity of TiO₂nanoparticles and TiO₂nanotubes in vivo was studied. Micewere exposed to TiO₂nanomaterials through intratracheal instillation, and then at different time themurine bronchoalveolar lavage fluid and serum indexes in blood were detected and the pathologicalmorphology of lung tissue were observed. The results showed that lung tissue damages were led bytwo different shape TiO₂nanomaterials. From the alveolar structure integrity of lung as well as thedegree of the abnormal tissue thickening, the responds to the same dose nanoparticles group weremore serious than to the nanotube group. And the lung tissue cell membrane damage and lipidperoxidation increased, but the barrier effect of lung capillary wasn’t affected. There were differentdegrees damage to liver, kidney and myocardium.（3） The cytotoxicity on mouse peritoneal macrophages of TiO₂nanoparticles and nanotubes invitro was studied at different contacted time. The morphology of macrophages was observed, the cellsurvival and the activity of enzyme in cell supernatants were detected. The results showed that TiO₂nanoparticles could be engulfed by macrophage and have obvious effects on the morphology ofmacrophages. The degrees of acute and injury effects on macrophages were concentration dependentin different contamination time. The TiO₂nanotubes could not be engulfed by macrophage and the effects on macrophage morphology was not apparent. The enzyme activity in TiO₂nanoparticles andTiO₂nanotube contacted cultured cell supernatants changed with contamination time andnanomaterials concentration, which led to cellular oxidative stress to produce toxic injury, inducedfree radical and enhanced oxidative stress ability.（4） The antibacterial property of TiO₂nanoparticles and nanotubes was investigated in theabsence of light. It was found that TiO₂nanoparticles have higher antibacterial activity than nanotubeson Escherichia coli and Staphylococcus aureus at the same dose and contacted time, but theantibacterial ratio was low. In order to get more high antibacterial activity and respond to visible light,nitrogen doped TiO₂particles were prepared by the sol-gel method. The average diameter ofnanoparticle was about30nm. Comparing the antibacterial activity of undoped titanium dioxidenanoparticles with nitrogen doped titanium dioxide nanoparticles in the dark and visible lightirradiation conditions on Staphylococcus aureus and Escherichia coli, the survival rates of the bacteriacontacted with nanoparticles for2hours in the dark conditions were higher than that underillumination conditions, but the survival rate value drop rate for not doped titanium dioxidenanoparticles from the dark to illumination conditions was far less than that for nitrogen doped titaniananoparticles at the same contacted time. This illustrated that the visible light irradiation enhanced theantibacterial activity of nitrogen-doped nano titanium dioxide.（5） TiO₂/PP composite materials with different contents of nitrogen doped titanium dioxidenanoparticles were manufacted by melt blending method. The mechanical properties, antibacterialperformance and microstructure of TiO₂/PP composite materials were performaced.The resultsshowed that TiO₂nanoparticles aggregated into microparticles in TiO₂/PP composite materials. Themechanical properties and antibacterial performance of the composites were better as the TiO₂contentis2wt%.Through this research, the biological toxicity and photocatalytic bactericidal performance ofnano TiO₂were explained further, and the experimental and theoretical foundation were laid for a newenvironment purification composite materials research. And this research had very importantsignificance for evaluating nanomaterials potential environment risks and ensuring thenanotechnology industry sustainable development.