Dissertation
Non-thermal dielectric barrier discharge (DBD) treated phosphate buffered saline (PBS): mechanisms of bacterial inactivation and cellular toxicity
Doctor of Philosophy (Ph.D.), Drexel University
Aug 2014
DOI:
https://doi.org/10.17918/etd-7011
Abstract
The recent results by our group have shown that non-thermal dielectric-barrier discharge plasma (DBD)-activated liquids acquire strong antimicrobial properties and have the potential to control bacterial pathogens. However, the underlying bacterial cell responses to these activated liquids are yet to be fully understood. In this study, we demonstrated that plasma-activated phosphate buffered saline (PBS) solution induced severe oxidative stress in Escherichia coli cells, and that this solution generated strong oxidants. We further explored the free radical species and chemical products generated in this solution that lead to stable topical disinfectant. This novel antibacterial solution has been studied in vitro and in vivo for cellular toxicity, demonstrating potential as a wound disinfectant. Analysis further showed that the reactive oxygen species (ROS) scavengers, [alpha]-tocopherol and catalase, were able to protect and rescue E. coli from cell death. The transcription factors, oxyR and soxRS were activated in E. coli cells during exposure to this antimicrobial solution. Results indicated that the management of this oxidative stress was regulated by oxyR and soxyRS regulons and mediated predominantly through the gene transcription of katG and sodA (up-regulated) that deactivate the generated oxidants. The inactivation involved loss of E. coli membrane potential and membrane integrity, lipid peroxidation, accumulation of 8-hydroxy-deoxyguinosine (8OHdG), and severe DNA damage. In parallel experiments, the species contained in this novel solution were analyzed using electron spin resonance and ultraviolet-visible spectroscopy. Reactive oxygen species (hydroxyl radicals, superoxide, and singlet oxygen) and reactive nitrogen species (nitric oxide, nitrate, and nitrite) were detected and work synergistically to create a robust antimicrobial agent. Application of this plasma-activated solution on animal models provided minimal injury site toxicity while reducing the infected wound by [greater than or equal to] 3 logs. This study provides a greater understand of the mechanism of bacterial inactivation, the pathways activated when exposed to plasma-activated PBS, the specific species generated and contained within the solution, and its potential as a topical wound disinfectant. Thus contributions to the fields of plasma disinfection, plasma medicine, and infection control were made.
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Details
- Title
- Non-thermal dielectric barrier discharge (DBD) treated phosphate buffered saline (PBS)
- Creators
- Adam D. Yost - DU
- Contributors
- Suresh G. Joshi (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xvi, 146 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- School of Biomedical Engineering, Science, and Health Systems (1997-2026); Drexel University
- Other Identifier
- 7011; 991014632346904721