Blood interface biomaterials - Biomaterials and Devices for the Circulatory System - page 42

Endothelial cell seeding of small calibre vascular prostheses has been
shown to reduce long-term platelet deposition, thrombus formation and
thus graft failure (Simon et al. , 1996). Numerous approaches have been
explored to facilitate the achievement of endothelialisation. An effective
method of promoting the integration and adhesion of the cells onto the
device is to immobilise agents such as extracellular matrix (ECM) protein
and oligopeptides, e.g. RGDs, directly onto the device surfaces (Sugawara
& Matsuda, 1995).
For enhancing the recognition of cell by the RGD-ligand modifi ed
surface, the combination of Pluronic surfactant/RGD containing hexapep-
tide has been shown to be effective in promoting cell attachment to hydro-
phobic substrates (Neff et al. , 1998).
A haemocompatible surface-modifying additive has been developed for
modifying PU or PU urea substrates. The additive has a urethane hard block
and a silicone soft block, an optional hydrophilic spacer and a RGD peptide.
It can be used as an additive to blend with PU in order to promote cell
adhesion (Riffl e, 1998).
In summary, there are many approaches to modify a polymeric surface
for improved blood compatibility on the basis of different hypotheses,
including increase in hydrophilicity, increase in hydrophobicity, forming a
microdomain structured surface, and building a bioactive surface which
functions as a living cell. It is believed that mimicking the blood vessel
surface represents the future for developing long-term blood-contacting
medical devices.

2.6 Conclusions

In this chapter, blood interface biomaterials have been reviewed, with a
brief discussion on the response of blood components when blood contacts
biomaterial surfaces. The infl uencing factors on blood compatibility were
considered, with an emphasis on one of the most commonly used blood
contacting biomaterials - plasticised poly(vinyl chloride) (PVC). There are
still many challenges to be met in order to achieve an ideal blood-compat-
ible surface. Many hypotheses have been proposed in the past to under-
stand the interface between blood and the biomaterial and many approaches
have been carried out, as discussed in this chapter.
Regenerative medicine and tissue engineering is a rapidly growing area
that aims to create, repair and/or replace tissues and organs by using com-
binations of cells, biomaterials and/or biologically active molecules. The use
of biomimetic approaches is one of the important approaches currently
being developed. This aims, via the modifi cation of existing biomaterials
with biomimetic moieties, to obtain a blood-compatible surface or stimulate
and regulate cell interaction. To produce a biodegradable scaffold for a

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