Electrospinning is a technique, which can be used to produce nanofibrous materials by introducing electrostatic fields into the polymer solution. Due to their intrinsic properties, such as small fiber diameter, small pore size and large surface area, nanofibres are suitable for use in a variety of applications including wound dressing, filtration, composites and tissue engineering. The study demonstrates the successful and optimised production of Poly(ethylene oxide) (PEO) and chitosan nanofibres by electrospinning. The biocidal effects of chitosan, chitosan-silver nanofibres and silver nanoparticles were successfully investigated. To set up a functional electrospinning apparatus, the PEO solution parameters (concentration, molecular weight, solvent, and addition of polyelectrolyte) and applied potential voltage on the structural morphology and diameter of PEO nanofibres were studied. At lower PEO concentrations, the fibres had morphology with a large variation in fibre diameter, whereas at the higher concentrations, the nanofibres exhibited ordinary morphology with uniform but larger fibre diameters. Higher molecular weight showed larger average diameters when compared to that obtained with the same polymer but of a lower molecular weight. The addition of polyelectrolyte to the polymer solution had an influence on the structural morphology of the PEO. Flow simulation studies of an electrically charged polymer solution showed that an increase in the flow rate was associated with an increase in poly(allylamine hydrochloride) (PAH) concentration for the low molecular weight polymer, the shape and size of the Taylor cone increasing with an increase in PAH concentration for the low molecular weight polymer. During optimization of the PEO nanofibres, based on statistical modelling and using the Box and Behnken factorial design, the interaction effect between PAH concentration and the tip-to-collector distance played the most significant role in obtaining uniform diameter of nanofibres, followed by the interaction between the tip-to-collector distance and the applied voltage and lastly by the applied voltage. The production and optimization of chitosan nanofibres indicated that the interactions between electric field strength and the ratio of trifluoroacetic acid (TFA) and dichloromethane (DCM), TFA/DCM solvents as well as between electric field strength and chitosan concentration had the most significant effect, followed by the concentration of chitosan in terms of producing nanofibres with uniform diameters. Chitosan and chitosan-silver nanofibres could be successfully electrospun by controlling the solution properties, such as surface tension and electrical conductivity with the silver nanoparticles in the chitosan solutions affecting the electrospinnability. The silver nanoparticles in the chitosan solution modified the morphological characteristics of the electrospun nanofibres, while the conductivity and the surface tension were elevated. The fibre diameter of the chitosan and chitosan-silver nanoparticles decreased with an increase in the silver content. The electrospun chitosan nanofibres had a smooth surface and round shape as compared to the silver-chitosan nanofibres with a distorted morphology. The chitosan and chitosan-silver nanofibres as well as the silver nanoparticles exhibited antimicrobial or inhibition activity against S. aureus than against E. coli. S. aureus bacterial culture showed good cell adhesion and spreading inwards into the chitosan nanofibrous membrane. The chitosan-silver nanofibres exhibited a greater minimum inhibitory concentration (MIC), followed by silver nanoparticles and then chitosan nanofibres; suggesting a synergistic effect between the chitosan and silver nanoparticles.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nmmu/vital:10449 |
| Date | January 2012 |
| Creators | Jacobs, Nokwindla Valencia |
| Publisher | Nelson Mandela Metropolitan University, Faculty of Science |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis, Doctoral, DPhil |
| Format | x, 209 leaves, pdf |
| Rights | Nelson Mandela Metropolitan University |
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