PhDNanotechnology is concerned with the study of processes and applications at the
nanoscale (10-9 m), with objects that are generally smaller than 100 nm. Within the
biomedical field, the use of metal nanoparticles and their oxides as antimicrobial
agents is gaining attention. In this study, the potential antimicrobial activity of thirteen
different nanoparticulate metals, oxides, carbides and nitrides was examined. These
were generated by thermal plasma technology. Initially, ten different bacterial
species/strains of clinical significance were subjected to in-depth antimicrobial
screening, which included the determination of minimum inhibitory and minimum
bacteriocidal concentrations. The nanoparticles that demonstrated the greatest
potential as novel antibacterial agents were, in descending order of activity: Ag >
CuO > Cu2O > Cu > ZnO with effective concentrations from 100 to 2500 μg/ml.
Ag and CuO nanoparticles, alone and blended, along with the salts of both elements
were further examined in time-kill assays. Nanoparticulate Ag (100 μg/ml) was able
to reduce microbial populations to zero within 2h. While, nanoparticulate CuO
required higher concentrations (> 1000 μg/ml) and longer times (up to 4h) than silver
to reduce microbial populations to zero. Blends of Ag and CuO nanoparticles were
shown to be superior than when used alone, with reduced concentrations and time
required (approx. 50%). Nanoparticles alone were not shown to be superior to that of
their corresponding salts. Antimicrobial activity in the presence of serum was not
reduced. Nanoparticulate TiO2, which lacked antimicrobial activity in the absence of
UV light, was shown to possess significant antimicrobial properties when irradiated
with short wave radiation. Environmental Scanning Electron Microscopy (ESEM) and
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Scanning Ion Conductance Microscopy (SICM) were used to examine toxic effects of
nanoparticles on bacteria. These revealed CuO nanoparticles to cause a greater
physical change to bacteria when compared to Ag. Following nanoparticle
incorporation into epoxy resin and polyurethane, the antimicrobial activity of the
resulting polymer-nanocomposites were examined. Both polymers were shown to
exhibit antimicrobial properties. Ion release was shown to be more marked from
materials containing CuO nanoparticles. Nanoparticle biocompatibility using skin,
respiratory and gastrointestinal cell lines was also investigated. CuO was shown to be
generally more toxic than Ag to eukaryotic cells