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Title: Microplasma technology for influencing cell-surface interactions
Author: Doherty, Kyle George
ISNI:       0000 0004 5350 9804
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2014
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Cataracts are the most common cause of preventable blindness worldwide. During cataract surgery a polymeric intraocular lens (IOL) is used to replace the cloudy natural lens. The most common post-operative complication is posterior capsule opacification (PCO). PCO is a wound healing response related to scarring, in which cellular changes disrupt the light path to the back of the eye through various processes, requiring a costly surgery to restore vision. The material of the IOL has been shown to affect PCO and it is hypothesised that the surface modification of IOL materials may be able to reduce the incidence of PCO. The use of plasmas established in the field of biomaterials modification and atmospheric pressure processes have significant benefits over the previous low pressure systems. In this work investigates the use of an atmospheric pressure plasma jet to modify the surface properties of polymeric materials, with the aim of developing a surface treatment method for use on IOLs. Materials and Methods The centre of polystyrene (PS) and poly(methyl methacrylate)(PMMA) surfaces were treated with an atmospheric pressure microplasma jet. The modification of surfaces was characterised by spatially resolved water contact angle, x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). LECs were seeded onto surfaces and grown for 1-7 days. Cell attachment, growth and morphology were examined microscopically. The concentrations of some cytokines implicated in PCO (transforming growth factor-β2, basic fibroblast growth factor, interleukin-1, interleukin-6, and tumour necrosis factor-α) in culture medium were examined at specific time points. Tissue culture polystyrene and untreated materials served as controls. Atmospheric pressure plasma polymerisation of amine containing monomers using a plasma jet was also investigated. Results and Discussions The size of surface treatment could be tailored by altering flow rate and sample-nozzle distance. Surface treatment was due to an increase in surface oxygen content and plasma treatment did not cause a significant change in surface roughness. Plasma treatment increased the LEC adhesion to substrates. LECs were densely populated in the centre of treated materials and cells lacked the cobblestone morphology typical of epithelial cells. The secretion of inflammatory cytokines by LECs grown on plasma treated surfaces did not appear to be up-regulated in comparison to tissue culture polystyrene, however these results are preliminary. This work demonstrated that atmospheric pressure plasma polymerisation can be achieved using the plasma jet system to incorporate nitrogen functionalisation onto PS surfaces; however oxygen was also incorporated onto surfaces. Conclusions This work demonstrates that an atmospheric pressure microplasma jet can be used to modify surfaces in a spatially defined manner, without damaging the polymer surfaces. The increase in surface oxygen promotes cell adhesion which can be confined to an area <3mm. This treatment size is too large to be used to create different spatially defined treatments on IOL optics as the typical optic diameter is only 6mm. The large treatment size is possibly due to gas convection spreading reactive species across the surface of samples when the plasma jet reaches the surface. Plasma polymerisation could possibly be used to incorporate functional groups which promote LEC growth which maintains an epithelial morphology.
Supervisor: Williams, Rachel; Sheridan, Carl Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available