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Fabrication of Novel Cytocompatible Membranes for Ocular Application, Concentrating in Particular on Age-Related Macular Degeneration (AMD)
[Thesis]. Manchester, UK: The University of Manchester; 2014.
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AbstractThe University of ManchesterAtikah Shahid HaneefDoctor of Philosophy (PhD)Fabrication of Novel Cytocompatible Membranes for Ocular Application, Concentrating in Particular on Age-Related Macular Degeneration (AMD)April 2014The aims of this research were to investigate polymer fibre morphology, overall mat morphology, mechanical properties and general handling of the mats, and ideal mat thickness in order to fabricate a suitable substrate for potential use in cell transplantation for application as a permanent substrate for the treatment of dry age-related macular degeneration (AMD). Polystyrene (PS), poly(ethylene terephthalate) (PET) and polyurethane (PU) were electrospun to ascertain the ideal electrospinning parameters to reproducibly obtain fibres to construct a mat as a potential candidate for a replacement Bruch’s membrane (BM). After identifying the ideal spinning parameters, mats were fabricated, their fibre morphology, overall mat morphology, and handling during processing were examined. This allowed the shortlisting of PS and PET substrates, which were suitable to be taken forward for further testing and cell culture. PU was found to be unsuitable as it had a tendency to become entwined and stick to itself, which would destroy the gross mat morphology. Therefore PU was excluded from further testing.Further handling, both quantitative and qualitative, and thickness and porosity were tested for PS and PET mats. Electrospun PET demonstrated greater handling and durability properties compared to PS mats, which were more fragile. PET was able to withstand twisting, folding, and rolling, whereas PS could not undergo twisting and fell apart. PS mats were thicker and more porous compared to PET mats, which was attributed to the widely spaced placement of the larger PS fibres and the fluffy gross morphology of the PS mats, in comparison to the closer fibre placement of the smaller PET mats which had a smooth gross mat morphology. Considering this, PS mats were compressed and thickness and porosity was reduced, while maintaining its fibrous structure. However the compressed PS mats became extremely fragile and could not withstand much handling. Although PET mats were thinner than PS mats, it did not match the native BM thickness and so experiments in varying collection time during electrospinning to match the native BM thickness were undertaken. Tensile tests, thickness and porosity measurements showed that PET tensile properties, thickness, and porosity reduced with reduced collection time.For the purposes of surface treatment and cell culture, uncompressed mats collected for 60 minutes were used since sufficient PS fibres were able to be collected to form a mat that was able to withstand processing at this collection time. Effect of UV/ozone surface treatment was tested for both PS and PET mats. Treatment of both substrate types affected protein adsorption, with evidence of aminolysis observed on PET substrates. Short-term initial growth and survival of retinal pigment epithelial cells (RPE cells) on electrospun, surface oxidised PS and PET was investigated. Untreated PS did not support cell proliferation and although treated PS did, the resultant RPE cell morphology was undesirable, therefore was not taken forward to long term cell culture. Treated and untreated PET supported cell proliferation, and was taken forward to the long term culture study, where cells exhibited the desired monolayer morphology. In this work it has been demonstrated that electrospun PET may potentially be a suitable candidate as cell carrier substrate for subsequent implantation in application towards AMD treatment.