Incorporation of different antimicrobial agents into a poly (ethylene-co-vinyl alcohol) matrix

Dyayiya, Nelisa Assistance (2018-03)

Thesis (MSc)--Stellenbosch University, 2018.

Thesis

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.

AFRIKAANSE OPSOMMING: Met die toename in mikrobiese weerstand teen bestaande antibakteriële behandeling, het daar ʼn aanvraag ontwikkel vir nuwe en meer effektiewe maniere om bakterieë te beveg. Hierdie toename in weerstandigheid is ʼn probleem in baie velde, insluitend voedselverpakking, watersuiwering en die farmaseutiese industrieë. Hierdie navorsing behels die kombinasie en karakterisering van verskeie antimikrobiese stowwe in ʼn polimeer matriks met die doel om die antimikrobiese aktiwiteit van die matriks te verhoog. Drie verskillende organiese en anorganiese antimikrobiese middels is geproduseer en geïsoleer tydens hierdie studie, naamlik chitosan-gebaseerde silwer nanopartikels, silwer geïmpregneerde mikrokristallyne sellulose en chitien nanovesels. Ultraviolet-sigbare spektroskopie en Fourier transform infrarooi spektroskopie het die suksesvolle vorming van hierdie antimikrobiese agente bevestig. Transmissie elektron mikroskopie en konfokale mikroskopie het getoon dat chitien-gebaseerde silwer nanopartikels met ʼn gemiddelde deursnit van 10 nm en wisselende vorms gevorm het terwyl die gevormde chitien nanovesels klein staafagtige vesels met ʼn gemiddelde lengte van 250 nm en breedte van 6 nm opgelewer het. Die progressiewe vorming van silwer nanopartikels op die oppervlakte van die mikrokristallyne sellulose is gemonitor deur gebruik te maak van ultraviolet-sigbare spektroskopie en transmissie elektron mikroskopie het aangedui dat hierdie nanopartikels se deursnit kleiner as 10 nm was en uit wisselende vorms bestaan het. Die drie individueel geproduseerde antimikrobiese middels sowel as verskillende kombinasies en konsentrasies daarvan was in ʼn poli(etileen-ko-viniel alkohol) (EVOH) matriks geïnkorporeer deur middel van elektrospin en oplosmiddel gieting om nanosaamgestelde nanovesel matte en nanosaamgestelde films respektiewelik, te vorm. Die verspreiding van hierdie antimikrobiese middels in die EVOH matriks was geanaliseer deur middel van korrelatiewe lig elektron mikroskopie (KLEM). Hierdie tegniek het ʼn in-diepte analise van die rangskikking en verspreiding van verskeie middels, wat gelaai is in dieselfde polimeer matriks, gegee. Die nanosaamgestelde films en vesels was gedoop in ʼn oplossing van Gramisidien S en die suksesvolle hegting van die peptied aan die oppervlak van die films en matte was bevestig deur middel van veld emissie skandering elektron mikroskopie (FESEM). Die peptied het ʼn neiging getoon om meer aan nanosaamgestelde films en vesels te bind wat hoër ladings van antimikrobiese middels bevat, maar ʼn algehele ontwrigting van die nanovesel morfologie was waargeneem teen 10 massa% lading. Die antimikrobiese toets het getoon dat hierdie nanosamestellings hoë antimikrobiese aktiwiteit toon teen Gram-positiewe bakterieë naamlik Micrococcus Luteus. In beide die films en vesels wou dit voorkom asof die konsentrasie van die antimikrobiese middel in die nanosaamgestelde monster geen effek gehad het op aktiwiteit nie, en dit was gevind dat die aktiwiteit effens hoër was vir die onbehandelde samestellings in vergelyking met die nanosamestellings waaraan die peptiede geheg was.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103628
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