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Title: Development of laser micro-fabricated surfaces to accelerate & enhance endothelial cell adhesion and proliferation
Author: Ching Tzu Goh
Awarding Body: Liverpool John Moores University
Current Institution: Liverpool John Moores University
Date of Award: 2014
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The aim of this thesis was to develop novel indirect laser micro-textured polymer substrates to accelerate and enhance bovine aorta endothelium (BAE-1) cell adhesion and proliferation. The response of BAE-1 and human coronary smooth muscle cells (HCASMCs) were studied, including cell adhesion, proliferation, β-actin expression, migration velocity, and migration directionality. The laser used in these experiments was a SPI infrared solid state fibre laser. By using beam overlapping scanning strategies surfaces having two types of distinct surface features were produced: (i) microfringes and (ii) microripples. Through a series of laser parameter optimisation experiments control of the melt expulsion mechanism and the formation of an intact recast ring could be generated. Overlapping of the focused beam resulted in an overlapping of the recast rings, thus resulting in surfaces having microripple and microfringe features. Experimental results found that polyurethane 1A, which has a projecting topography of ~4μm width microfringes, significantly increased BAE-1 cell adhesion, proliferation, and β-actin expression, compared to the non-textured surface. However, strong adhesion to this surface decreased mean cell migration velocity. Furthermore, focal adhesions were confined to the microfringe structure leading to the formation of parallel actin stress fibres and as a result changed the cell migration directionality. On the other hand, Polyurethane 3D, which has a projecting topography of ~6μm width microripples, was also found to significantly enhance BAE-1 cell proliferation (only at 72 hours post cell seeding), β-actin expression and migration velocity, when compared to the non-textured polyurethane. Differences were also found between BAE-1 and HCASMCs cells. HCASMCs were less sensitive to the polymer substrates and were not found to be influenced by the microfringe and microripple structures. However, the microridges with >700nm height on polyurethane 1A, 3A and 3D were found to promote HCASMC alignment parallel to the microridges. In addition, the Z1A1 polyurethane used for pattern transfer through polymer casting has shown delayed HCASMCs adhesion. Further investigation is required to study the effect of Z1A1 polyurethane’s chemical properties on HCASMACs behaviour. Overall, the data obtained from this work, suggests that the width dimension of the microfringes and microripples between ~4-6μm are important regulators for BAE-1 behaviour and microridge heights >700nm are important regulators for HCASMCs alignment. The preliminary data provided from this work can be used for stent technology development in the future.
Supervisor: French, Paul Sponsor: Biomer Technology Ltd
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral