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Title: Processing novel electrospun polymer scaffolds for biomedical applications
Author: Robb, Brendan
ISNI:       0000 0004 7971 0872
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2014
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Electrospinning has proven to be a viable method of producing nano to micro scale fibres from a variety of materials. These fibres typically form non-woven mats displaying significantly large surface to volume ratios and networks of interconnected pores. Increasing interest in the utilisation of these fibre mats for medical research has been a trend over the last decade, but, despite significant progress, major technological hurdles still exist to routine production and utilization. Potential applications for electrospun fibres in medicine include tissue engineering and regenerative medicine, drug delivery and semi-permeable wound dressings. The aims of this study were to investigate the process parameters governing electrospun fibre morphology and then apply this to the fabrication of novel biomaterial scaffolds capable of eliciting applicable and reproducible biological responses. A highly configurable electrospinning rig was assembled with the capability of consistently producing specific fibre morphologies, whilst at the same time recording the process parameters via an electronic computer interface. Temperature and humidity control facilitated the establishment of controlled environments for a variety of electrospinning experiments. Scaffolds produced were rigorously characterised using techniques such as scanning electron and confocal microscopy and surface tension (water contact angle) analysis. The biocompatibility of scaffold design was assessed using in vitro cell culture experiments that included analytical assays and imaging. An empirical model for predicting changes to electrospun poly-ε-caprolactone (PCL) fibre diameter based on induced changes to the electrospinning process was developed. The accuracy of the model was tested by predicting the mean fibre diameters produced under several conditions on our industrial partner's multi-nozzle electrospinning rig. Subsequent testing of these conditions on the multi-nozzle apparatus showed a correlation regression of 0.956 between predicted values and experimentally measured results. Aligned fibres electrospun from PCL-chitosan blends were produced for a range of volume ratio blends of the two materials. The blended fibre scaffolds showed improved mechanical properties over pure chitosan scaffolds. Investigation into the inflammatory cytokine expression of murine macrophage cells in the presence of blended fibres was undertaken. Scaffolds containing at least 25% chitosan by weight were found to significantly reduce peroxide and cytokine expression from macrophage cells in comparison to controls. PCL solutions were also functionalised with surfactant additives and electrospun into non-woven mats. The influence of surfactant in solution elicited a small change in fibre diameters produced, as well as significant differences in the wettability of the spun scaffolds. The incorporation of lecithin, mannitol and sodium lauryl sulphate into PCL was tested according to ISO 10993-5 for cytotoxicological effects - results demonstrated that all scaffold compositions had retained their biocompatibility. Imaging of cells cultured on functionalised PCL scaffolds showed significantly improved cell infiltration into the porous network compared to untreated PCL fibres. Poor cell infiltration has been recognised as a major obstacle to widespread adoption of electrospun scaffolds and this novel functionalisation method shows great potential for further study. The contributions presented in this thesis reveal improved protocols for controlling and monitoring the production of predictable electrospun fibre morphologies. These techniques were employed to produce electrospun scaffolds with properties targeted to specific cell interactions. Results show that control over scaffold morphology and the inclusion of bioactive agents can significantly improve the suitability of these materials.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: electrospinning ; biomaterials