| Summary: | 碩士 === 國立中興大學 === 生命科學系所 === 96 === Silver or silver compound can inhibit bacteria growth. Silver nanoparticle also has the bactericidal effect but the antibacterial mechanism is still unknown. AgNP/NSP and AgNP/SWN, the materials used in this article, are synthesized by using nano silicate platelet clays and artificial organic clays as dispersing to stabilize and immobilize silver nanoparticles and consequently used to study the antibacterial mechanism of silver nanoparticles. Firstly, the growth inhibition capability of AgNP/NSP and AgNP/SWN to multidrug-resistant Acinetobacter baumannii and silver ion-resistant E. coli strain J53 pMG101 were analyzed and compared with silver nitrate. The result showed that among these three silver compound AgNP/NSP has the best bactericidal effect under the same silver concentration.Observation by using Scanning Electron Microscope(SEM) revealed that AgNP/NSP encapsulated the bacteria and form multiple clay-cells aggregates. Absorbed bacteria on AgNP/NSP repelled the entry of propiodium iodide(PI) indicating that bacteria cell membrane was not ruptured. But whether the mild lesion of cell membrane leads the growth retardation is still unknown. By using E. coli strain ML-35p, we found that Ag nanoparticles clay indeed could increase the membrane permeability.Therefore we speculate that Ag nanoparticles clay has bactericidal effect through interfering intracellular homeostasis. We also find only higher than 0.1wt% Ag nanoparticles clay can obviously decrease β-galactosidase activity and this result demonstrated the oxidization of functional proteins by Ag nanoparticles was not strong. Besides bacteria , AgNP/NSP and AgNP/SWN also could inhibit the growth of infectious fungi, including Trichophyton rubrum、Trichophyton fluviomuniense、Trichophyton mentagrophytes、Microsporum canis and Microsporum gypseum , the common pathogens of Tinea pedis. For the substitution of antibiotics, Ag nanoparticles clay was applied to cure fowl diarrhea after infection with salmonella. After eighteen hours, AgNP/NSP via oral route retarded bacteria spread to other organ. The Ag nanoparticles- resistant bacteria was not found, showing the safety of clinical application. We further demonstrated that geno-safety of AgNP/NSP by Ames test, showing lower than 0.5mg/plate dose have no genetic mutation. In the future , we will further explore the mechanism of bactericidal effect of AgNP/NSP and apply Ag nanoparticles clay to clinical treatment of bacterial infection.
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