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Preliminary Study on the Antibacterial Activity and Mechanism of Ag Nanoparticles Against Escherichia Coli

Author: QuFeng
Tutor: WeiHua；XuHengYi
School: Nanchang University
Course: Microbiology
Keywords: Silver nanoparticles Antibacterial activity Reactive oxygen species Antibacterial mechanism Antimicrobial packaging
CLC: Q93
Type: Master's thesis
Year: 2011
Downloads: 155
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Abstract

Antibacterial properties of silver as early as in the 16th century was discovered and widely used in the pharmaceutical industry. With the development of nanotechnology in the 20th century, the physical and chemical properties of silver nanoparticles, especially biological applications into the spotlight. The unique structural properties of nanoparticles to enhance the performance of the silver nanoparticles, a small amount of literature and its broad spectrum antimicrobial, antibacterial and does not produce drug resistance, has antibacterial antibiotics can not match advantage. As a new class of antibacterial materials, the silver nanoparticles is still a lack of systematic, basic research is lagging behind. The antibacterial activity of existing literature in different ways, the lack of uniform measurement method, the results can not be compared; the silver nanoparticles antibacterial mechanism has not been completely elucidated. Most of the literature in the description of the phenomenon of anti-bacterial stagnation, lack of a mechanism to explore. Although some antimicrobial mechanism of conjecture, but still needs more experimental data support. In this study, based on the characterization of the nature of the silver nanoparticles, the establishment of a rapid determination of the antibacterial activity of silver nanoparticles. The results show: the silver nano-particle diameter of about 3 nm, the hydrodynamic diameter of approximately 17 nm, the surface zeta potential of approximately -35 mV. Antibacterial silver nanoparticles sensitive time for 5 h, 5 mg / L, the median lethal concentration of E. coli. Gold Nanoparticles as a control, no antimicrobial activity, prompted the antibacterial activity of silver nanoparticles and their surface-coated polymer layer is irrelevant. In E. coli as a model in microorganisms, the antibacterial activity of silver nanoparticles was determined on Escherichia coli. A concentration of 5 mg / L of silver nanoparticles on the death rate of Escherichia coli was approximately 50%; the antibacterial activity of silver nanoparticles with temperature, pH, oxygen supply and bacterial proliferation. The results showed that: 5 mg / L of silver nanoparticles on Escherichia coli mortality rate decreased to 23 ° C conditions 35%; environment of pH 2.0 to 3%; decreased to 20% in the oxygen-free environment; in physiological saline rose to 99%. Explore the antibacterial mechanism of the silver nanoparticles, the two aspects begin from the cell morphology and reactive oxygen species, a detailed analysis of the silver nano-particles on the morphology and structure of the E. coli bacterial cells using an atomic force microscope; Determination of the concentration of active oxygen and antioxidants The antibacterial activity of silver nanoparticles. The results showed that: with the role of silver nanoparticles, irregular morphology of the E. coli bacterial cells, surface cracks; antibacterial activity of silver nanoparticles with the active oxygen concentration is positively correlated; antioxidant acetylcysteine ??(10 mM) significantly reduced the silver antibacterial activity of nanoparticles, the silver nanoparticles (10 mg / L) for lethality of E. coli from 90% down to 40%. The actual bactericidal effect of silver nanoparticles in food is an important foundation of its application, this paper conducted a preliminary study of silver nanoparticles used in the preservation of milk, juice, soy milk and broth. The results showed that: the silver nanoparticles saline, apple juice and LB culture of E. coli in liquid fatality rate was 99.5%, 99.9% and 92.6%, respectively; E. coli broth, milk and soy milk in the mortality rate were 29.0% , 15.1% and 21.8%, prompted silver nanoparticles have strong antibacterial activity of E. coli in the low-protein foods, high-protein food in E. coli weak antibacterial activity.

Preliminary Study on the Antibacterial Activity and Mechanism of Ag Nanoparticles Against Escherichia Coli

Abstract

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