Browsing by Author "Dyayiya, Nelisa Assistance"
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- ItemIncorporation of different antimicrobial agents into a poly (ethylene-co-vinyl alcohol) matrix(2018-03) Dyayiya, Nelisa Assistance; Lutz, Marietjie; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.ENGLISH ABSTRACT: With the increase in microbial resistance to existing antimicrobial therapies, there is a need for the development of new and more effective ways to fight against microbes. This increase in resistance is a problem in many fields, which include the food packaging, water treatment and pharmaceutical industries. This research investigates the combination and characterization of different antimicrobial agents within a certain matrix in order to maximize the antimicrobial efficacy of the matrix. Three different organic and inorganic antimicrobial agents were produced and isolated during this study, namely chitosan-reduced silver nanoparticles, silver impregnated microcrystalline cellulose and chitin nanowhiskers. Ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy confirmed the successful formation of these antimicrobial agents. Transmission electron microscopy and confocal fluorescence microscopy confirmed the formation of chitosan-reduced silver nanoparticles with an average diameter of 10 nm and variable shapes while chitin nanowhiskers were produced as small rod-like whiskers with an average length of 250 nm and 6 nm in width. The progressive formation of silver nanoparticles on the surface of the microcrystalline cellulose was monitored using ultraviolet-visible spectroscopy and transmission electron microscopy showed these nanoparticles were less than 10 nm in diameter and had variable shapes. The three individual antimicrobial agents as well as different combinations and concentrations thereof were incorporated into a poly (ethylene-co-vinyl alcohol) (EVOH) matrix via two different methods, namely, electrospinning and solvent casting to obtain nanocomposite nanofibre mats and nanocomposite films, respectively. The distribution of these antimicrobial agents within the EVOH matrix was investigated using correlative light electron microscopy (CLEM). This technique gave an in-depth analysis of the arrangement and dispersion of multiple agents loaded simultaneously into the same polymer matrix. The nanocomposite films and fibres were dip-coated in a Gramicidin S solution and the successful attachment of the peptide to the surface of the films and fibre mats was shown by field emission scanning electron microscopy (FESEM). The peptide indicated a tendency to attach more to nanocomposite films and fibres containing higher loadings of antimicrobial agents but a complete disruption in the nanofibre morphology was observed with the 10 wt% loading. The antimicrobial tests showed that these nanocomposites have high antimicrobial activity against the Gram-positive bacteria, Micrococcus Luteus. For both films and fibres, the concentration of the antimicrobial agent in the nanocomposite sample seem to have no effect on the activity and the antimicrobial activity was found to be slightly higher for neat composites compared to the peptide attached nanocomposites.