NANOTECHNOLOGY AND BIOMATERIALS IN OPHTHALMIC SURGERY

Glaucoma is one of the leading causes of blindness. When medical therapy is not effective in reducing the intraocular pressure, a surgical approach is needed. Trabeculecomy is the gold standard procedure, but new minimally invasive techniques are available. The ExPress glaucoma shunt is recognized as one of the most promising options and its characterization and possible improvements are the aim of the present study. The device was physically and chemically characterized. SEM images were obtained and the ExPress implant was analyzed in all aspects. Surprisingly, a high degree of roughness was observed on the surface of the internal lumen. This may cause cell adhesion and fibrin deposition, eventually leading to obstruction of the device and failure of the surgery. Cell adhesion was studied with the use of cell cultures of fibroblasts. A limited degree of cell adhesion was demonstrated on the inner lumen of the device. On an explanted Ex-Press device from a human eye, a discrete amount of biological extracellular matrix was observed. The use of energy-dispersive X-ray spectroscopy was used to demonstrate the presence of carbon on the device. Evidence of possible cell growth and extracellular matrix deposition on the device was therefore demonstrated. Moreover, a massive bacterial contamination occurred, suggesting possible infection transmission in vivo. The second part of the research was dedicated to define a computational model in order to study the effect of the scleral flap and the suture position on the filtration rate. A 2 D model and a 3D model were studied to simulate the outflow of aqueous from the eye. Interestingly, we demonstrated the role of the suture placing in determining the pathways of outflow. The 3D model was useful to better understand the deformation of the scleral flap and it suggested a role of the head position on the outflow pattern. Most of the outflow was estimated to occur at the sides of the scleral flap, within 2 mm from the corneal side. Subsequently, a nanocoating was planned in order to reduce cell and bacterial adhesion on the device. The procedure allowed the formation of a layer of fluorinated silanes and polymer grafting chains, possibly with biologically active moieties. After the silane treatment, different polymers were tested using the “grafting from” technique. Grafting from technique is based on the growth of polymers directly from the surface previously functionalized with the proper species. Monomers employed were styrene, methylmethacrylate and N,N-dimethylacrylamide. The experiments were carried out on stainless steel (SS) 316L 1x1 cm plates, in order to test the same material of the device, but with easier handling. Contact angle measures and atomic force microscopy analysis were performed to characterize the samples. Samples were then tested for bacterial adhesion. In order to verify the anti adhesion properties, samples were compared with pristine SS plates. Samples and pristine plates were immersed in a solution of Staphylococcus Aureus, properly incubated, washed and treated in order to permit a bacteria count. The bacterial adhesion analysis showed that the Polystyrene treated plates demonstrated the lowest bacterial adhesion and vitality, while the effect of Polymethylmethacrylate and PolyN,N-dimethylacrylamide was less evident