Division of Information Technology, Engineering and the Environment
School of Advanced Manufacturing and Mechanical Engineering
School of Advanced Manufacturing and Mechanical Engineering
Thesis Abstract
Blindness is one of the worst disabilities. The statistic reported by WHO in 2002 indicated that 6.5 million people under 50 years of age and 30.3 million people above 50 years old were clinically blind. Age-related macular degeneration (AMD) is a primary cause responsible for over 8.7% of these cases (Resnikoff, 2004). This illness is a result of damage to the retinal pigment epithelium (RPE). In AMD the central vision is gradually lost, due to pigmentary abnormalities and drusen (i.e. waste materials) accumulation, resulting in retinal pigment epithelium (RPE) detachment, leakage and choroidal neovascularisation (Fine et al., 2000). Various methods of treatment of AMD have been investigated so far; thermal laser photocoagulation, photodynamic therapy (Del Priore et al., 2006), radiotherapy, surgical macular translocation or surgical removal of the neovascular membrane (Aisenbrey et al., 2002; van Meurs and Van Den Biesen, 2003), pharmacological treatment which make use of inhibitors of angiogenesis (Binder et al., 2007), gene therapy (Jager et al., 2008) and electronic devices which could replace the retina (Loewenstein et al., 2004). However, with the possible exception of electronic devices, these methods are not sufficient for a complete cure of the disease being unable to effect repair of the already damaged tissue and evoke severe side effects.
The main purpose of this research project is to identify a surface capable of supporting the in vitro growth and culture of RPE cells to form a functional epithelial cell sheet, suitable for transplantation. In this project the surface is prepared from a biodegradable polymer, poly(DL-lactic-co-glycolic acid) (PLGA). Formulations of this co-polymer are used as cell scaffolds for skin, cartilage and bone regeneration (Holy et al., 2001) and it has been demonstrated to promote good cell attachment (Giordano et al., 1997). PLGA is soluble in water (Wnek G.E., 2008) and biocompatible at the intraocular site (Lu et al., 2001).
The understanding of the interaction between cells and the polymer surface is essential. In most instances cells prefer to adhere to surfaces which are moderately hydrophilic; extremely hydrophobic and hydrophilic surfaces preventing most types of cells from attaching and growing. The hydrophilicity can be changed by the ratio of carbon to oxygen and here we have chosen plasma polymerisation as the technique to chemically engineer the surface of the PLGA substrate. This technique allows the production of the ultrathin, homogenous films displaying specific chemical functionalities. The plasma polymerisation process generates a coating which reflects aspects of chemical functionality present in a monomer precursor. A range of plasma co-polymers, using allylamine and octadiene monomer precursors, were deposited onto the PLGA. Allylamine is used as a source of nitrogen and 1,7-octodiene as a source of hydrocarbon groups to distribute nitrogen functional groups and similar plasma processing has been used successfully in the development and clinical application of cell therapies for chronic wounds such as burns and non-healing foot ulcers (Haddow et al., 2006).
Plasma polymer coatings of the type described here, with amine functionalities, allows for passive immobilisation of glycosaminoglycans (GAGs) on the surface. There are many important biological processes that depend on these sugar molecules in the binding of freely diffusible proteins e.g. growth factors, chemokines and blood clotting factors in addition to their role in cell-extracellular matrix adhesion. It has previously been demonstrated, in our laboratory and elsewhere, that immobilisation of GAGs on a surface can enhance cell adhesion and survival with maintenance of physiological functionality and it is hypothesised that the presence of GAGs on the chemically engineered surface can help to mimic the natural cell environment. GAGs are synthesised naturally in RPE and their influence on this particular type of cells is going to be investigated in this work.
