In this study, an in-house built atmospheric. pressure non-thermal plasma jet has been investigated for its potential utilisation as a new alternative antimicrobial tool for a variety of medical applications. Anti - biofilm activity of this plasma jet has been evaluated against biofilms of a selected panel of bacterial species, grown on different abiotic surfaces, where complete eradication of all tested bacterial biofilms was achieved after relatively short plasma exposures of up to 10 minutes. Multiple approaches of cell viability evaluation were adopted to show the nature, extent and distribution of the remarkable anti-biofilm activity of the plasma jet including colony counting, XTT metabolic assay, scanning electron microscopy examination and differential Live/Dead fluorescent staining followed by confocal laser scanning microscopy examination. Antibacterial efficacy of the plasma jet has also been evaluated against similar bacterial species in their planktonic mode of growth where plasma exposures even shorter than those required for biofilm eradication were sufficient to cause complete inactivation of these planktonic bacteria. Such excellent bactericidal activity resulted from the ability of plasma exposure to mediate an oxidative damage to multiple cellular targets including cellular membrane, DNA and proteins of bacterial cells. However, damage of cellular membrane and the resultant disruption of its integrity and permeability were shown to be the primary rate-determining step in the plasma mediated bacterial cell death. Furthermore, in depth investigation of the plasma- mediated bacterial destruction mechanism has been carried out to identify the plasma-produced reactive species that were responsible for mediating its bactericidal activity. Based on the findings of this study, a hypothesis was formulated to describe the mechanism of bacterial cell destruction after plasma exposure. This hypothesis assumed a two-part mechanism; one part was a rapid H20 2-dependent mechanism associated with Fenton's or Fenton's-like reaction that was catalysed by metal ions released from the bacterial cells initially damaged by another proposed H20 2 - independent mechanism.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:602409 |
| Date | January 2013 |
| Creators | Alkawareek, Mahmoud Yousef |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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