Synthesis and Biological Effects of Silver Nanoparticles on the Bacteria Staphylococcus aureus and Escherichia coli

Silver nanoparticles (Ag-NPs) have strong antimicrobial potential, which has been exploited in many biomedical applications. However, the interaction between these unique nanomaterials and microorganisms has not been well elucidated. It is necessary to understand the mechanisms of interaction betwee...

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Main Author:	Anes Abdulhadi, Mohammed Jawad
Format:	Thesis
Language:	English English
Published:	2018
Subjects:	QR Microbiology
Online Access:	http://ir.unimas.my/id/eprint/30306/2/Anes%20Abdulhadi%20Mohammed%20Jawad%2024pgs.pdf http://ir.unimas.my/id/eprint/30306/3/Anes%20Abdulhadi%20Mohammed%20Jawad%20ft.pdf
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id	my-unimas-ir.30306
record_format	uketd_dc
institution	Universiti Malaysia Sarawak
collection	UNIMAS Institutional Repository
language	English English
topic	QR Microbiology
spellingShingle	QR Microbiology Anes Abdulhadi, Mohammed Jawad Synthesis and Biological Effects of Silver Nanoparticles on the Bacteria Staphylococcus aureus and Escherichia coli
description	Silver nanoparticles (Ag-NPs) have strong antimicrobial potential, which has been exploited in many biomedical applications. However, the interaction between these unique nanomaterials and microorganisms has not been well elucidated. It is necessary to understand the mechanisms of interaction between nanomaterials and microorganisms. Therefore, this study investigates the interaction that occurs between Ag-NPs and the bacteria Staphylococcus aureus (s. aureus) and Escherichia coli (E. coli), with a focus on analysing the influence of size and surface functionalisation of Ag-NPs towards their antibacterial applications. To perform the study, various Ag-NPs were synthesised, characterised and tested for their antibacterial activity; the synergy between laser light and Ag-NPs towards enhanced antibacterial activity was also examined. Three sizes were synthesised via the chemical reduction method, using tri-sodium citrate (TSC) and sodium borohydride (NaBH4) as the reducing and capping agents. These different sizes (5, 10, 20 nm) Ag-NPs were tested for toxicity and antibacterial activity against the Gram-negative bacterium, E. coli and Gram-positive bacterium, S. aureus. The different-sized Ag-NPs all exhibited antibacterial activity against both E. coli and S. aureus strains. However, Ag-NPs with 5 nm displayed the highest antibacterial activity when compared with 10 and 20 nm particles sizes. The 20 nm size particle showed the lowest antibacterial efficiency against both bacterial strains and has therefore been selected for further studies. The photoactivation of 20 nm Ag-NPs using 410 nm laser light demonstrated that photoactivated Ag-NPs at 50 ~glml exposed for 10 min reduced E. coli and S. aureus . populations to 13% and 28%, respectively. S. aureus exhibited lower sensitivity after photoactivation compared to E. coli. Photo activation of 20 nm Ag-NPs by laser revealed that production of reactive oxygen species (ROS) due to oxidative stress, the mode of action against bacteria, causing cell wall cleavage and cell lysis, as shown by the scanning iv electron microscope (SEM). An additional experiment to examine the effect of Ag-NPs functionalised with antibodies was conducted using a 20 om size particle as the antibody carriers for inducing selective bacterial activity. This study utilised Ag-NPs functionalised with antibodies specific to one of the bacterial cell wall components against S. aureus to investigate the Ag-NPs' antibacterial ability to bind and destroy their target bacteria when excited using 410 om irradiation. The conjugation of 20 om Ag-NPs to antibody after photoactivation by laser irradiation led to 100% dead cells after 10 min exposure time. Physical damage to bacterial cells was observed via fluorescence assay, leading to loss of membrane integrity in treated bacterial cells. The proposed mechanism of killing is that, the irradiation of Ag-NPs' surfaces causes oxidative stress, which induces ROS, such as 'OH, 02'- and H202 generation, that attack cell components resulting in loss of membrane permeability and DNA damage, as seen via the SEM and fluorescence assay. This study demonstrates that several factors can influence the microbial effectiveness of Ag-NPs, including the size of particles, photo activation and surface functionalisation. The antibacterial activity of 20 om Ag-NPs can be enhanced using several methodologies outlined within this thesis. The research shows that functionalised Ag-NPs appropriately recognize and bind to their target bacteria, and that the Ag-NPs successfully complete the energy transfer from a visible laser to the target bacteria.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Anes Abdulhadi, Mohammed Jawad
author_facet	Anes Abdulhadi, Mohammed Jawad
author_sort	Anes Abdulhadi, Mohammed Jawad
title	Synthesis and Biological Effects of Silver Nanoparticles on the Bacteria Staphylococcus aureus and Escherichia coli
title_short	Synthesis and Biological Effects of Silver Nanoparticles on the Bacteria Staphylococcus aureus and Escherichia coli
title_full	Synthesis and Biological Effects of Silver Nanoparticles on the Bacteria Staphylococcus aureus and Escherichia coli
title_fullStr	Synthesis and Biological Effects of Silver Nanoparticles on the Bacteria Staphylococcus aureus and Escherichia coli
title_full_unstemmed	Synthesis and Biological Effects of Silver Nanoparticles on the Bacteria Staphylococcus aureus and Escherichia coli
title_sort	synthesis and biological effects of silver nanoparticles on the bacteria staphylococcus aureus and escherichia coli
granting_institution	Universiti Malaysia Sarawak (UNIMAS)
granting_department	Faculty of Resource Science and Technology
publishDate	2018
url	http://ir.unimas.my/id/eprint/30306/2/Anes%20Abdulhadi%20Mohammed%20Jawad%2024pgs.pdf http://ir.unimas.my/id/eprint/30306/3/Anes%20Abdulhadi%20Mohammed%20Jawad%20ft.pdf
_version_	1783728381314990080
spelling	my-unimas-ir.303062023-03-08T03:22:01Z Synthesis and Biological Effects of Silver Nanoparticles on the Bacteria Staphylococcus aureus and Escherichia coli 2018 Anes Abdulhadi, Mohammed Jawad QR Microbiology Silver nanoparticles (Ag-NPs) have strong antimicrobial potential, which has been exploited in many biomedical applications. However, the interaction between these unique nanomaterials and microorganisms has not been well elucidated. It is necessary to understand the mechanisms of interaction between nanomaterials and microorganisms. Therefore, this study investigates the interaction that occurs between Ag-NPs and the bacteria Staphylococcus aureus (s. aureus) and Escherichia coli (E. coli), with a focus on analysing the influence of size and surface functionalisation of Ag-NPs towards their antibacterial applications. To perform the study, various Ag-NPs were synthesised, characterised and tested for their antibacterial activity; the synergy between laser light and Ag-NPs towards enhanced antibacterial activity was also examined. Three sizes were synthesised via the chemical reduction method, using tri-sodium citrate (TSC) and sodium borohydride (NaBH4) as the reducing and capping agents. These different sizes (5, 10, 20 nm) Ag-NPs were tested for toxicity and antibacterial activity against the Gram-negative bacterium, E. coli and Gram-positive bacterium, S. aureus. The different-sized Ag-NPs all exhibited antibacterial activity against both E. coli and S. aureus strains. However, Ag-NPs with 5 nm displayed the highest antibacterial activity when compared with 10 and 20 nm particles sizes. The 20 nm size particle showed the lowest antibacterial efficiency against both bacterial strains and has therefore been selected for further studies. The photoactivation of 20 nm Ag-NPs using 410 nm laser light demonstrated that photoactivated Ag-NPs at 50 ~glml exposed for 10 min reduced E. coli and S. aureus . populations to 13% and 28%, respectively. S. aureus exhibited lower sensitivity after photoactivation compared to E. coli. Photo activation of 20 nm Ag-NPs by laser revealed that production of reactive oxygen species (ROS) due to oxidative stress, the mode of action against bacteria, causing cell wall cleavage and cell lysis, as shown by the scanning iv electron microscope (SEM). An additional experiment to examine the effect of Ag-NPs functionalised with antibodies was conducted using a 20 om size particle as the antibody carriers for inducing selective bacterial activity. This study utilised Ag-NPs functionalised with antibodies specific to one of the bacterial cell wall components against S. aureus to investigate the Ag-NPs' antibacterial ability to bind and destroy their target bacteria when excited using 410 om irradiation. The conjugation of 20 om Ag-NPs to antibody after photoactivation by laser irradiation led to 100% dead cells after 10 min exposure time. Physical damage to bacterial cells was observed via fluorescence assay, leading to loss of membrane integrity in treated bacterial cells. The proposed mechanism of killing is that, the irradiation of Ag-NPs' surfaces causes oxidative stress, which induces ROS, such as 'OH, 02'- and H202 generation, that attack cell components resulting in loss of membrane permeability and DNA damage, as seen via the SEM and fluorescence assay. This study demonstrates that several factors can influence the microbial effectiveness of Ag-NPs, including the size of particles, photo activation and surface functionalisation. The antibacterial activity of 20 om Ag-NPs can be enhanced using several methodologies outlined within this thesis. The research shows that functionalised Ag-NPs appropriately recognize and bind to their target bacteria, and that the Ag-NPs successfully complete the energy transfer from a visible laser to the target bacteria. Universiti Malaysia Sarawak (UNIMAS) 2018 Thesis http://ir.unimas.my/id/eprint/30306/ http://ir.unimas.my/id/eprint/30306/2/Anes%20Abdulhadi%20Mohammed%20Jawad%2024pgs.pdf text en public http://ir.unimas.my/id/eprint/30306/3/Anes%20Abdulhadi%20Mohammed%20Jawad%20ft.pdf text en validuser phd doctoral Universiti Malaysia Sarawak (UNIMAS) Faculty of Resource Science and Technology

Synthesis and Biological Effects of Silver Nanoparticles on the Bacteria Staphylococcus aureus and Escherichia coli

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