Study On Antimicrobial Activity And Biosafety Of Silver Nanoparticles

Modified chemical reduction and photochemical reduction methods were used to prepare the silver nanoparticles(Ag NPs). The optimum size of Ag NPs was characterized by SEM, TEM, EDX three instruments. Then, the anti-microbico mechanism was speculated by testing and characterization of anti-microbico of Ag NPs with different concentration and partical size. Finally, the safety of Ag NPs was discussed by acute toxicity and hemolysis experiments. The main contents of the thesis are as follows:(1) The modified chemical reduction method and the modified photochemical reduction method were used to prepare the Ag NPs solution concentrations between 2.02 × 10-5 mol/L and 16.16 × 10-5 mol/L and the Ag NPs particle sizes in the range of 10 ~ 40 nm. The results of SEM and TEM characterizations showed that Ag NPs particles prepared by the modified chemical reduction method were spherical and dendrimers, Ag NPs particles prepared by the modified photochemical reduction method were spherical silver nanoparticles and showed a single inter-particle dispersion layer with well dispersion.(2) The experiment culture was chosen E. coli, S. aureus and Vibrio vulnificus. The anti-microbico property was tested and characterized of Ag NPs with different concentration and partical size. Inhibition zone method and agar antibacterial experiments showed all of Ag NPs solution prepared in this experiment have good antibacterial properties. The optimum inhibitory concentration of E. coli and Vibrio vulnificus was 12.12 × 10-5 mol/L, and the optimum particle size of E. coli and Vibrio vulnificus was 20 ~ 25 nm. The optimum inhibitory concentration of S. aureus was 8.08 × 10-5 mol/L and the optimum particle size of S. aureus was 10 ~ 15 nm. The antibacterial effect of Ag NPs against S. aureus was superior to E. coli and Vibrio vulnificus. The results of the morphology and the structure of the cell by SEM showed the cell membrane may be corrupted.(3) It was found that the presence of Ag NPs in concentrations of 2.02 × 10-5 mol/L and 16.16 × 10-5 mol/L significantly decreased the growth of strains Af293 and Gra04. Especially, the antibacterial rate was 100% for Af293 and Gra04 at the 4.03 × 10-5 mol/L and 8.08 × 10-5 mol/L concentration of Ag NPs compared to other concentrations. The mechanism of antifungal activity of Ag NPs was presumably that the Ag NPs destructed the cell protein by the deletion of glucan and chitin.(4) Toxic effects were assessed via general behavior. There were no influence for liver, lungs and kidneys of mice for the injection volume at 100 μL of Ag NPs solution. All of the biochemical criterions returned to normal for the injection volume at 0.1 μL of Ag NPs solution. The results showed that the high dose of Ag NPs solution had some effect for the biochemical criterions. How to decrease the influence of Ag NPs solution is one of key work at the future. In addition, the homolysis was not occurred at the injection volume at 2.77 μL of Ag NPs solution. This would be foundation for the contact the products of Ag NPs with the blood of persons.