Biomedical Engineering Reference
In-Depth Information
overproduction of proteins such as collagen and ECM. Fibrosis works
as a repair and restoration of a structure but cannot reproduce the
initial function of the tissue. The biomaterial is not well integrated into
the tissues - it is not “biointegrated” - it cannot be qualified as
biocompatible since a hostile host response or foreign body response
has been developed against the biomaterial. Is the biomaterial bio-
tolerant or biocompatible? Does an encapsulation mean a disrupted
healing or an abnormal healing process? The intensity of the
inflammatory host response gives an idea of the biocompatibility of a
material.
Aside from the inflammatory and immune system, the other part of
the host response is more specific and depends on the location of the
implantation. Coagulation is an important part of the host response
since it facilitates the regulation and equilibrium of the entire
blood vascular system. In the case of contact between a biomaterial
and blood, a cascade of reactions lead to the formation of a blood
clot - biocompatibility with blood, or “hemocompatibility”, would
mean the biomaterial helps in preventing the formation of a thrombus.
This biomaterial does not yet exist even if several surface
modifications have been set up to solve this problem.
As the host response is developed at the interface between the
living tissues and the implant, it is strongly dependent on the nature
of the biomaterial surface: chemistry, physico-chemistry
(hydrophilic/hydrophobic balance), structure (rough, smooth, nano- or
microstructuration). The most extreme care has to be taken on the
control of the surface.
4.5. Biocompatibility - how can we evaluate it?
Biocompatibility is very often correlated with performance and
success in a particular domain or a precise application [WIL 08,
PAR 05]. Therefore, to
evaluate biocompatibility, it is useful to keep
in mind the definition of biocompatibility given by D. Williams
in
section 4.2.2. That definition insists on the specificity of the
