Biocompatibility of cardiovascular devices - Biomaterials and Devices for the Circulatory System - page 68

anticoagulants, anti-proliferative drugs, statins, ACE inhibitors, and nitric
oxide donors (Feldman et al. , 2000; Chan et al. , 2001; Luan et al. , 2003). The
most commonly used systemic agents are the antiplatelet agents used after
coronary stenting to minimize thrombotic complications (Kedia and Lee,
2007). However, other systemic approaches have fared less successfully and
have been limited by systemic complications in animal models and thus
have not made a great impact in clinical applications (Walpoth et al. , 2001).
The utilization of targeted approaches with systemic therapy such as the
fusion of platelet integrin receptor (GPIIb/IIIa) ligands to antiplatelet
drugs can have some benefi t in minimizing these complications (Vyas and
Vaidya, 2009).
Local delivery either by direct infusion (Mattar et al. , 1996) or, more
commonly, by use of polymers as either coatings or scaffold for devices
can optimize local drug concentrations while limiting systemic toxicity.
While the advent of drug eluting stents has increased the interest in
delivering targeted therapies to coronary angioplasty and stent sites,
late stent thrombosis and persistent infl ammatory and pro-coagulant
responses to polymers may remain a problem (Nakazawa et al. , 2008;
Wykrzykowska et al. , 2009). For these reasons, the utilization of bioresorb-
able polymers for both drug delivery and as scaffolding holds promise for
the future.

3.4.3 Bioresorbable materials

Bioresorbable materials can serve as scaffolds for temporary devices which
are resorbed and incorporated into the native anatomy over time, can be
used as polymeric vehicles from which drugs can be eluted with controlled
kinetics, or can serve both purposes simultaneously. Thus, the implanted
device can serve its functional purpose for the time it is required and then
histologically 'disappear,' theoretically minimizing the long-term infl amma-
tory and injury response and the potential for device infection. Knowledge
of resorption kinetics of specifi c bioresorbable materials or copolymeric
formulations with non-resorbable or other resorbable materials can ulti-
mately lead to a well-controlled drug release strategy based on the intrinsic
properties of the materials being used (Blindt et al. , 1999; Zilberman et al. ,
2004, 2005; Lafont et al. , 2006). The study of the histologic, immunologic,
infl ammatory and other biologic mediators which modulate the resorption
kinetics of these biomaterials is a fi eld of intense study and should serve to
provide optimal polymer constructs for bioresorption and the delivery of
drugs to the interventional site.
The conceptual utility of these biomaterials has been acknowledged
for some time. Early encouraging studies demonstrated repopulation of
bioresorbable polyglycalic acid (PGA) with host cells and endogenous

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