Nanotechnology and nanomedicine in cardiovascular therapy - Biomaterials and Devices for the Circulatory System - page 254

These studies highlight the role that nanotechnology could potentially
play in the management of cardiovascular disease in the coming years.

9.3 Nanofi bres

The fi rst synthetic graft to be used clinically was Vinyon N in the early 1950s
(Voorhees et al. , 1952). Since then numerous synthetic grafts are available
but their thrombogenicity makes them unsuitable for low-fl ow conditions,
e.g. when the luminal diameter is less than 6 mm. Again the nanotechnology
strategy using nanofi bres with tissue engineering is attempting to tackle this
problem (Hoenig et al. , 2006).
Electrospinning employs an electric fi eld and the principle of mutual
charge repulsion to produce a jet of the polymeric solution onto a collector
which then solidifi es to produce fi bres. If the collector is static the fi bres will
be randomly distributed and if the collector is rotating then they are aligned.
Co-axial electrospinning, a more recent development, allows the integration
of two components into one conduit to produce core-shell structured nano-
fi bres (Venugopal et al. , 2008).
Examples of materials used in electropsun nanofi bres include
poly(caprolactone), collagen blended poly(L-lactic acid)-co-poly(epsilon-
caprolactone), and silk (He et al. , 2005b; Ma et al. , 2005; Soffer et al. , 2008).
These products have shown signifi cant potential especially when co-
electrospun with the tri- n -buytlamine salt of heparin. This results in a
heparin-releasing nanofi bre whose surface content of heparin could
be increased by raising the heparin content in the fabrics (Kwon and
Matsuda, 2005).
Electrospun nanofi bres could also potentially be modifi ed to present
nanostructured surfaces which encourage endothelial cell adhesion. This
was demonstrated by higher human umbilical vein endothelial cell
adherence to a poly(ethylene terephthalate) fabric covalently linked to
nano-scaled sintered hydroxyapatite compared with the absence of hydroxy-
apatite (Furuzono et al. , 2006; Igarashi et al. , 2007). Electrospun fi bres can
also be biodegradable (Xu et al. , 2004).
Endothelialisation of nanofi bres may prevent intimal hyperplasia, which
is a signifi cant problem in small diameter vascular grafts. A nanofi bre
fabricated by electrospinning collagen-coated poly(L-lactic acid)-co-
poly(epsilon-caprolactone) can attach human coronary artery endothelial
cells, possibly due to its collagen coat, which subsequently proliferate (He
et al. , 2005a).
Self-assembling nanoparticles offer an alternative to electrospun nanofi -
bres. These nanoparticles form molecular coatings 1-10 nm in depth.
Self-assembled monolayers of 11-mercaptoundecanoic acid and 11-
mercapto-1-undecanol on stainless steel can be aids to drug delivery in

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