Blood interface biomaterials - Biomaterials and Devices for the Circulatory System - page 40

microdomain structured surface, which exhibits blood compatibility
(Akers et al. , 1977).

2.5.2 Bioactive surfaces

A bioactive surface is a surface which is able to simulate or mimic the func-
tion of a blood vessel surface to secrete bioactive substances, to function
metabolically and to respond to physiological effects. In summary, biomi-
metic character is the main feature of a bioactive surface.
Bioactive surfaces can be prepared by surface immobilisation of bioac-
tive substances, incorporation of bioactive additives to a blend system,
utilisation of oligosaccharides, phospholipid substances and biospecifi c pep-
tides, and/or the combination of the above methods. The molecular design
of a bioactive surface for improved blood compatibility is shown in Fig. 2.3.

Heparinised surfaces

Lindahl et al. (1994) showed that the blood vessel wall contains substances
that are structurally and functionally related to heparin and this promoted
acceptance of the concept of immobilisation of the heparin anticoagulant
activity. In fact, heparinised surfaces are the most commonly applied non-
thrombogenic surfaces for current blood-contacting medical devices. The
design of such a surface has been reviewed by Plate & Value (1986), Kim
(1996) and Kim & Jacobs (1996).

Immobilised
anticoagulant

Incorporation of
antioxidants

Phospholipid polar
group

￿ ￿ ￿ ￿ ￿

Oligosaccharides Release of

anticoagulant

Biomaterials

Immobilised
enzymes

Oligopeptide
for cell
adhesion

Release of
nitric oxide

2.3 Molecular design of bioactive surfaces with improved blood
compatibility.