Cardiovascular stents - Biomaterials and Devices for the Circulatory System - page 187

to result in a reduced infl ammatory response and accelerated endothelial
coverage of the stent by reversing the negative effect on endothelial growth
and induce smooth muscle cells (SMC) (Di Mario et al. , 2004). This hypoth-
esis was tested in the MOONLIGHT trial (Multicenter Objective Obser-
vatioNal Lunar iridium oxide Intimal GrowtH Trial) which aimed to
evaluate the immediate outcome and long-term angiographic success
after implantation of iridium coated Lunar stents. The Lunar stents (Infl ow
Dynamics, Munich, Germany) were produced from 316L stainless steel
laser cut tubular stents with a double coating of a thin layer of gold (5 µm)
to improve visibility and an outer layer of iridium (1 µm) to stimulate
endothelialisation. The study concluded that the Lunar stent was both
deliverable and achieved optimal clinical and angiographic results with a
low restenosis rate (13.8%). Other iterations of this stent have been pro-
duced that eliminate the gold layers by sputtering the iridium directly onto
the stent (O'Brien & Chandrasekaran, 2004). Currently, research in this
area is focused on the production of titanium alloys such as Ti-45Ta-5Ir
and particularly Ti-17Ir for their more favourable mechanical and radi-
opacity, although the biocompatibility and corrosion resistance of these
materials has yet to be proven (O'Brien et al. , 2008).

Titanium-nitride oxide coatings

Titanium alloys have found application in a range of biomedical materials
because of their favourable corrosion resistance, biocompatibility and
mechanical properties, although they have not been widely accepted as
stent materials (O'Brien et al. , 2008). However, studies of coatings of tita-
nium-nitride oxide produced on stainless steel stents using physical vapour
deposition in a mix of oxygen-nitrogen gas have been demonstrated to
reduce neointimal hyperplasia compared to bare stainless steel stents in a
porcine restenosis model (Windecker et al. , 2001). The effi cacy of the coating
in attenuating the neointimal proliferation was mainly attributed by the
authors to its electrochemical properties. The 'TiNOX' stents have subse-
quently undergone clinical trials. In 2005 Windecker and colleagues revealed
the results of the TiNOX trial which concluded that re-vascularisation with
the titanium-nitride oxide coated stents was safe and effective in patients
with de novo native artery lesions and that the coatings reduced restenosis
and major adverse cardiac events when compared with stainless steel coun-
terparts (Windecker et al. , 2005). In 2006, Karajalainen and colleagues
compared stainless steel stents coated with titanium-nitride oxide with a
paclitaxel eluting stent and demonstrated that both stent types produced
favourable outcomes with infrequent need for repeat interventions in high
risk patients (Karajalainen et al. , 2006). In 2008 the same group reported a
12 month follow-up to the TITAX AMI trial which concluded that the

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