Browsing by Author "Whiting, Nicole"

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    Double-layered wound dressing based on electrospun antimicrobial Polymer
    (Stellenbosch : Stellenbosch University, 2017-03) Whiting, Nicole; Klumperman, Bert; Pfukwa, Rueben; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.
    ENGLISH ABSTRACT: The design and production of novel wound dressings that address resistance of microorganisms to antimicrobial agents, has attracted considerable attention. The ability to produce polymers with specific characteristics for specific applications offers a wide variety of options for application in the biomedical field, especially polymers that exhibit antimicrobial behaviour. This thesis is thus committed to the design, synthesis and characterisation of a bi-layered wound dressing, as well as antimicrobial evaluation of the final product. The bi-layered wound dressing consists of a component that maintains a favourable moist wound environment and a second component that addresses microbial infection. For the component that maintains the favourable moist wound environment two hydrogels will be created and electrospun. For this study the hydrogels were chosen to be sodium alginate, a hydrogel already in use for wound dressings, as well as a hydrogel from poly(styrene-alt-maleic anhydride) (SMA). For the antimicrobial component, quaternary ammonium salts were synthesised, as these are known to have antimicrobial properties. SMA is a biocompatible and commercially available copolymer that can easily undergo chemical modification through the highly reactive maleic anhydride residues and therefore is an attractive polymer for the production of hydrogels and antimicrobial polymers. SMA was synthesised by conventional free radical chemistry, followed by modification to yield a hydrogel as well as modification of SMA to yield two quaternary ammonium salts, exhibiting antimicrobial activity. SMA was electrospun and treated with a heat-activated crosslinking agent, namely diethylene glycol, to yield a nanofibrous hydrogel. A second nanofibrous hydrogel was also created from a natural polymer, namely sodium alginate. SMA was also treated with 3-(N,N-dimethylamino)propyl-1-amine (DMAPA), a compound with both a primary and tertiary amine, to yield poly(styrene maleimide) (SMI). SMI was then treated with two alkyl halides (1-bromooctane and 1-bromododecane) to yield quaternary ammonium compounds (qSMI) that shows antimicrobial activity. The quarternised SMI is then also electrospun to yield an antimicrobial nanofibrous layer and heat treated to render the fibres insoluble in water and organic solvents. The bi-layered wound dressing is produced by electrospinning one layer on top of the other in the case of the SMA hydrogel, followed by heat treatment to render the fibres insoluble. In the case of the alginate hydrogel, qSMI is electrospun and heat treated, followed by electrospinning of alginate on top of the qSMI layer. The individual electrospun fibre mats as well as the bi-layered system are subjected to antimicrobial evaluation by means of confocal fluorescence microscopy as well as zone inhibition on agar plates. The organisms used for the antimicrobial evaluation were Staphylococcus aureus, a Gram-positive bacterium, and Pseudomonas aeruginosa, a Gram-negative bacterium. Confocal imaging and zone inhibition revealed that qSMI containing the C12 aliphatic side chain showed a greater antimicrobial activity towards S. aureus as compared to C8. In the case of P. aeruginosa it was not clear which of the C8 or C12 containing qSMI fibres showed greater antimicrobial activity, however confocal imaging and zone inhibition revealed that both showed antimicrobial activity towards P. aeruginosa.