ABSTRACT
The growing demand for the use of nanoparticles in daily consumer products has greatly influenced the research being carried out on them to determine their properties and effects in different fields of life. Their versatility has enhanced their incorporation into over a thousand consumer products used on a daily basis, and this has led to the discovery of their antimicrobial abilities through different mechanisms such as the formation of Reactive Oxygen Species (ROS). Findings from this study showed that at certain concentrations, the ions produced by nanoparticles suspended in deionized water were capable of inhibiting the growth of E. coli and S.aureus. Results obtained revealed that when ZnO ion in solution of varying concentrations (1ml, 2ml, 3ml) was mixed with 1ml of E. coli, it yielded a bacterial count of 2.73 X 10₂cfu/ml, 6.8 X 10₁cfu/ml and 4.2 X 10₁cfu/ml respectively. The same procedure was carried out for TiO2 with the same varying concentrations and it yielded E. coli bacterial counts of 1.73 X 10₂cfu/ml, 5.5 X 10₁cfu/ml and 3.8 X 10₁cfu/ml. when the same procedures were carried out for S.aureuswith the same varying conditions of both nanoparticle ions the results obtained were 1.08 X 10₂cfu/ml, total inhibition and 6.2 X 10₁cfu/ml respectively for ZnO, and 9.8 X 10₁cfu/ml, 6.2 X 10₁cfu/ml and 4.0 X 10₁cfu/ml respectively for TiO2. Since the ions produced by nanoparticles have not been known to pose any threat to the environment, it is therefore safe to suggest that they be used in production of consumer products instead of the nanoparticles themselves in order to retain the antimicrobial properties of the nanoparticles without their adverse effects.
CHAPTER ONE
INTRODUCTION
Inhibiting the deleterious effects of microorganisms has been the main purpose of their study since they were first discovered by Anton van Leeuwenhoek between 1665-1683 (Gest et al; 2009).This has proven to be impossible as these microorganisms have adapted to most of the techniques developed to curb their harmful capabilities. However, with the growing rise of the novel nonpareil called “nanoparticles”, and their exceptional versatility which promotes their use in innumerable fields; the world is on the verge of an evolutionary breakthrough, especially in the field of microbiology. The incorporation of these particles into consumer products for daily use has revealed that nanoparticles exert antimicrobial abilities through different mechanisms such as the formation of Reactive Oxygen Species (ROS), disruption of physiological and metabolic processes (Eduok et al; 2013).
Nanoparticles however, can be defined as particulate matter with dimensions under 100 nanometers (nm) (Christian et al; 2008). They could be tabular, spherical or irregularly shaped; and can occur as fused, aggregated or agglomerated (Nowack et al; 2007).Although they are relatively very minute, their characteristics differ extensively from that of smaller molecules; and their synthesis and chemical makeup goes on to insinuate that nanoparticles be regarded more as complex mixtures rather than small molecules (Christian et al; 2008). Nanoparticles are considered as unique, xenobiotic and ubiquitous in the environment, occurring from both natural and anthropogenic processes like flocculation of metal oxide nanoparticles in acid-mine drainages (Lowry et al; 2012).
Although nanoparticles in general are considered a discovery of modern science, they actually have a very long history. Nanoparticles were used by artisans as far back as the 9th century in Mesopotamia to generate a shiny effect on the surface of pots (Khan; 2012). Research on the antibacterial properties of ZnO nanoparticles goes back to the early 1950s (Li et al; 2009), and further research on how the surface area and concentration of ZnO nanoparticles play a key role in deactivating microorganisms has been ongoing since the 1930s (Yamamoto et al; 1998). Despite recent discoveries on the side effects of these particles on microorganisms and the environment, there is difficulty in the full understanding of the behavioral patterns of these particles (Pan et al., 2010; Woodrow Wilson Database., 2011).
Nanoparticles such as TiO2 are cytotoxic and can induce apoptosis and/or necrosis in human monoblastoid cells. More research on the biochemical and molecular toxicity of TiO2 particles yielded results that indicated oxidative damages, toxicant metabolism alterations and DNA damages (Pan et al,. 2009; Vamanu et al., 2008; Ueng et al., 1997; Sayes et al., 2005; Guo et al., 2007). Furthermore, the surface of ZnO can synthesize hydrogen peroxide, which penetrates cells through the cell membrane, disrupts cellular processes, thereby inhibiting the growth of cells and ultimately leading to cell lysis (Wang et al., 2012; Sawai et al., 1996).
The use of Engineered Nanoparticles as a broad spectrum antimicrobial agent in consumer products is increasing rapidly and these particles are readily released into the environment with potential negative implications for key microbial mediated processes (Beddow et al., 2014). There is,
However, an abysmal need to develop a deeper understanding of the fate, behavior and nature of nanoparticles in the environment. This need is motivated by the increased use of engineered nanoparticles and the high demand to commercialize this growing technology (Christian et al., 2008).
The aim of this study is to fully examine and understand the inhibitory effects of ZnO and TiO2 ions on model organisms, using Escherichia coli and Staphylococcus aureus as test subjects.
AIMS AND OBJECTIVES
- To isolate, characterize and identify Escherichia coli and Staphylococcus aureus as model organisms for this study.
- To assess the effect of ions produced by engineered nanoparticles on the growth of the test isolates.
- To corelate the effects of thr isolates and the ecological significance on microbial mediated processes.
To examine the risks, if any, posed by nanoparticles in the environment