The long-term efficacy of coronary or peripheral stenting is limited by in-stent
restenosis (ISR), which occurs in 15 to 30% of patients and is attributed primarily to
neointimal hyperplasia. By adding a drug-eluting coating, this rate has been reduced
to about 5% or less. However, recently longer-term follow-up data has highlighted
problems with drug-coated stents, including late stage thrombosis. A bio-stable
poly(carbonate-urea)urethane has been used for stent coating and the surface
properties of the polymer have been optimised by incorporating the polyhedral
oligomeric silsesquioxane molecule. These POSS polymers improve the adhesion and
the growth of endothelial cells. The work described in this thesis, presents an
innovative approach in self-expanding/balloon expandable coronary stent design that
incorporates a NiTi/stainless steel alloy scaffold with a polyhedral oligomeric
silsesquioxane- poly (carbonate-urea) urethane nanocomposite polymer (POSS-PCU)
coating. Electrohydrodynamic spraying and ultrasonic atomization spraying of the
non-biodegradable nanocomposite polyhedral oligomeric silsesquioxane (POSS)
polymer have been investigated in detail for coating metallic stent materials and
compared with dip coating. Because of the tight geometry of coronary stents, these
new coating techniques have been shown to offer advantages over traditional coating
techniques. These advantages include, reduced polymer consumption, precise coating
thickness as low as 10 μm and a highly controllable spray which leads to consistent
reproducible results. However, poor adhesion, or bond deterioration over the lifespan/
deployment of the device could reduces the efficiency and could impart even more
complexity to the implant including formation of debris which can induce thrombus
formation. Changing the surface physical property/chemical composition through the
proposed protocol has been shown to increase the bonding strength by up to three
times. This study has identified a new process and conditions which can be used in
stent coating research
