Silver nanoparticles : on the synthesis of silver nanoparticles, their antimicrobial properties and longevity

Abstract

Silver nanoparticles have become common place today due to their antimicrobial properties however they have become particularly popular due to their potential to kill multi-resistant (MR) bacteria. Silver nanoparticles have shown promising results as a solution to the problem of antibiotic resistance. However, little is known about their spectrum of antimicrobial activity, their mode of action and their most effective size and morphology. Furthermore, there has been limited research into the effectiveness of silver nanoparticles over time, their leakage into the environment, their effect on natural ecosystems and their potential persistence in the environment. The aim of this project was to develop a silver nanoparticle with proven antimicrobial properties, and to gain understanding of the aging process and possible persistence. This was conducted by synthesising and characterising silver nanoparticles using different synthetic methods, determining their antimicrobial properties and evaluating changes in size, morphology and antimicrobial effects after aging. Particle morphology and size was determined via Ultraviolet""visible spectroscopy (UV-vis) and Scanning Electron Microscopy (SEM). Minimum Inhibitory Concentrations (MIC) and Minimum Bactericidal/Fungicidal Concentration (MBC/MFC) assays were performed to determine the extent of antimicrobial properties. The silver nanoparticle samples were then aged for a week under ambient conditions and again characterised by UV-vis, SEM, and MICs were determined. Nanoparticles synthesised by the heat reduction method produced a highly effective bactericidal and antifungal effect but showed stability making them potentially harmful to the environment. Alternatively, the chemical reduction method produced particles which showed antimicrobial properties against Gram-negative bacteria, were short lived and therefore providing a lower environmental impact. The results of this study have demonstrated the importance of understanding and considering the synthetic method and how it affects the associated silver nanoparticle aging process.

Date of Award	2018
Original language	English