Cardiovascular stents - Biomaterials and Devices for the Circulatory System - page 184

early stage following vascular injury. Aoki and coworkers (2005) reported
the fi rst clinical investigation to use stents with immobilised antibodies able
to capture endothelial progenitor cell (EPC) surface antigens. The EPC
capture stent consists of a covalently coupled polysaccharide intermediate
coating with murine monoclonal anti-human CD34 antibodies attached to
a stainless steel stent. The study was the fi rst of its kind to demonstrate that
the EPC capture coronary stent could provide a feasible new treatment of
atherosclerotic coronary arteries (Aoki et al. , 2005).
More recently, Miglionico and colleagues (2008) demonstrated the use of
an endothelial progenitor cell antibody-coated stent implanted into patients
with high risk angiographic or clinical features. In an attempt to facilitate
the growth of a confl uent, functional endothelial layer over the implant and
in an attempt to reduce thrombosis and restenosis the stainless steel Genous
R-stents were covered with antibodies specifi c to surface antigens on endo-
thelial progenitor cells (Miglionico et al. , 2008). The study claimed the cell
capture stent to be safe and effective with good short and mid-term out-
comes and no evidence of thrombosis, but pointed to the need for larger
randomised trials before being considered as alternatives for drug eluting
or bare metal stents. The trial is currently ongoing in the Tri-stent Adjudica-
tion Study (TRIAS) that will directly compare the clinical usefulness of
endothelial progenitor cell capturing stents with drug eluting and bare
metal counterparts. A full review of the progress in this area can be found
in Klomp et al. (2009).

7.4.4 Carbon coatings

The coating of stents has been hypothesised to reduce the release of metal-
lic products, with a view to reducing both platelet and cellular activation
and the associated infl ammatory response. Indeed, Gutensohn et al. (2000)
developed diamond-like carbon (DLC) coatings which, in vitro , resulted in
the release of virtually no metal ions (manganese and molybdenum) from
coated stents (BioDiamond DLC coated stents, Mainz, Germany). Further-
more, the study demonstrated that in the presence of platelet-rich plasma,
DLC coated stents produced less platelet activation and deposition and
reduced thrombogenicity when compared to bare stainless steel stents
(Gutensohn et al. , 2000; Santin et al. , 2004). The ability of thin layer carbon
fi lms to improve the haemocompatibility of stainless steel stents was further
demonstrated in subsequent studies (Stary et al. , 2003; Yang et al. , 2004). A
number of DLC coated stents have subsequently appeared on the market,
including the Biodiamond (PlasmaChem GmbH) and Biodiamond F
(PlasmaChem GmbH) stents, both of which have a 316L stainless steel
substrate coated with a thin (50 nm) layer of DLC and the DLC-coated
Phytis™ (Phytis Medical Devices GmbH, Berlin, Germany). The clinical

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