| In this dissertation, Ag nanoparticle(Ag NPs) and Zn O/Ag core/shell nanoparticle(Zn O@Ag NPs) were synthesized, which would be used for study on antibacterial behavior. In addition, the toxicity against Physarum polyoephalum of three kinds of nanoparticle was researched. The main contents of this dissertation are as follows.1. Ag NPs was synthesized in water phase, and Na BH4, Ag NO3,and PVP or C- chitosan acted as reductant, silver source, and dispersant, respectively. In this synthesizing process, Na OH was added to participate in the chemical reaction. Some parameters in the synthesizing process were adjusted. In the end, two kinds of Ag NPs were prepared, whose dispersant was PVP and C- chitosan, respectively. The morphology of these Ag NPs was ball. The crystalline structure was FCC. Their diameter distributions were 14.4-36.7 nm and 8-38.4 nm, respectively. And their aqueous solutions were both homogeneous and no sedimentation was found in the bottom. The disc diffusion method and the continous LB culture medium dilution method were used to evaluate the antibacterial behavior of these Ag NPs. It was shown that Ag NPs exhibited outstanding antibacterial property and certain inhibit effect against yeast. In addition, this paper had researched the antibacterial mechanism of Ag NPs through SEM and confocal laser scanning microscope(CLSM). It was shown that Ag NPs induced microorganism cell produced a large number of reactive oxygen species(ROS). The excessive ROS would result in oxidative damage and kill microorganism.2. Zn O NPs, Ag(TEA)2+ and formaldehyde(or hydrazine hydrate) acted as core, silver source, and dispersant, respectively, and a three-step method was used to synthesize Zn O@Ag NPs. It was shown that the crystalline structure and morphology of Ag NPs on the surface of Zn O@Ag NPs was FCC and ball or spheroidicity, respectively. The size range of Ag NPs varied from 10 nm to 42 nm as the efficiency of Ag NPs coating Zn O NPs also exhibit a positive dependence on the size of Ag NPs. The disc diffusion method and the continous LB culture medium dilution method were used to evaluate the antibacterial behavior of Zn O@Ag NPs with different coating efficiency. It was shown that Zn O@Ag NPs has outstanding antibacterial property, and certain inhibit effect against yeast. The antibacterial results of Zn O@Ag NPs against S. aureus corresponded to Ag NPs, and the MIC value of Zn O@Ag NPs against Yeast was 1.5 times of PVP-Ag NPs, and 3 times of C- chitosan- Ag NPs, while its Ag content was just 25% of Ag NPs. In addition, this paper had researched the antibacterial mechanism of Zn O@Ag NPs through CLSM. It was shown that Zn O@Ag NPs induce microorganism cell producing a large number of reactive oxygen species(ROS). The excessive ROS would result in oxidative damage and kill microorganism.3. This dissertation evaluated the toxicity of two kinds of commercialized nanoparticles, Zn O NPs and Ti O2 NPs, and Ag NPs in the second chapter in Physarum polyoephalum. The remarkable inhibiting concentration against Physarum polyoephalum of Zn O NPs, Ti O2 NPs and Ag NPs was 1750 μg/m L, 15000μg/m L and 300μg/m L, respectively. The toxicity of Ag NPs exhibited the strongest toxicity, Zn O NPs followed it, and Ti O2 NPs had a weakest one. Physarum polyoephalum perform a escaping appearance under a high concentration of Zn O NPs, but Ti O2 NPs and Ag NPs had no a similar characteristic. Under interacting of those three kinds of nanoparticle, the MDA levels of Physarum polyoephalum all exhibited dependence on the concentration of nanoparticle. It increased at first and then decreased as their concentrations increased, which reveal a rule of oxidative damage against Physarum polyoephalum. The level of oxidative damage increased as increasing concentrations of those three kinds of nanoparticle. When the level reached a threshold, Physarum polyoephalum died, which leaded to a decreasing law of MDA. The discovery provided a very impartant evidence for the ROS mechanism of nanoparticle toxicity. |
PDF Full Text Request