Injuries to the central nervous system (CNS) have traumatic consequences such as irreparable disability due to the inability of the CNS to regenerate injured nerve fibres. The aim of the work presented here was to develop a scaffold which potentially provides guidance to axons in the injured spinal cord thus facilitating signal transduction. A poly-(lactic-co-glycolic acid) (PLGA, PLA:PGA ratio of 75:25) flat sheet membrane scaffold was created using phase inversion with N-methyl pyrrolidinone (NMP) as the solvent and water as the non-solvent for immersion precipitation. PLGA flat sheet membranes were exposed to surface treatments including aminolysis, peptide immobilisation and ozonation in order to achieve higher cell attachment of PC12 cells, a cell line which was cloned from a solid pheochromocytoma tumour of white rats, and used as a tool for measurement of regeneration. Cell attachment studies revealed no significant difference in cell attachment between modified and not-modified PLGA flat sheet membranes. However, the absence of foetal calf serum (FCS) resulted in fivefold higher cell attachment compared to medium supplemented with 10% FCS. A second scaffold was produced by electrospinning 10% (w/w) PLGA in a chloroform:methanol (CHCl3:MeOH) mixture in ratio of 3:1 resulting in a nanofibrous scaffold. Optimum settings for electrospinning were found to be 3 ml/h feeding rate, 15kV applied voltage and 11cm collector-to-needle distance. Random and aligned PLGA nanofibres were produced, with a fibre diameter of 530±140nm. PC12 cells attached and differentiated to the nanofibrous scaffold. When exposed to NGF these cells stopped dividing and extended neurites. On random fibres, neurite orientation was random, whereas on aligned fibres 63% of neurites grew with the fibre orientation ±15��ᵒ. After 7 days of exposure to NGF, cells had 1-4 neurites on random fibres, reaching a maximum length of 188μm, whereas on aligned fibres, cells had 1-2 neurites, reaching a maximum length of 400μm. PLGA nanofibres were also investigated as a delivery vehicle for bioactive molecules. For this, poly-L-lysine (PLL) was incorporated into electrospun PLGA nanofibres via emulsion electrospinning. PLGA-PLL nanofibres were significantly larger than PLGA nanofibres having a diameter of 830±190nm. In order to visualise the incorporation of PLL, FITC-PLL was electrospun und the resulting nanofibres fluoresced greed. Attachment of PC12s to PLGA-PLL nanofibres was not significantly different compared to PLGA nanofibres. Aligned PLGA-PLL nanofibres were shown to promote neurite outgrowth of PC12s with resulting neurites of up to twice the length compared to aligned PLGA nanofibres. The results suggest that PLGA nanofibres strongly influences neurite organisation, which is potentially useful for future therapeutic approaches. The work in this thesis has shown that electrospun PLGA nanofibre mats have the potential to be used as scaffolds for spinal cord repair addressing topographical guidance and delivery of bioactive molecules to the site of injury.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:591041 |
| Date | January 2013 |
| Creators | Kraemer, Marina |
| Contributors | De Bank, Paul ; Ellis, Marianne ; Chaudhuri, Julian |
| Publisher | University of Bath |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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