Biomedical Engineering Reference
In-Depth Information
14.2 State-of-the-art of biomaterials for bone tissue
engineering
the use of biomaterials in tissue engineering has two main functions: (1)
temporary support for the cells while they produce new tissue and (2) cell
carrier during implantation thus ensuring their appropriate delivery at the
site of implantation.
The first function is essential regardless of the tissue engineering strategy.
More explicitly, the biomaterial substrate role is essential to the tissue
engineering construct, both when a tissue is grown
in vitro
, for example in
a bioreactor system, and when the tissue engineering construct is implanted
in the body early after its assembly. the second function is important only
in those cases where a tissue engineering construct is intended to stimulate
tissue repair at the site of implantation. in the last case, the biomaterial has
to offer a series of properties which:
∑ provide an appropriate environment to maximise cell viability
∑ give ease of handling in the surgical theatre to facilitate the implantation
procedure
∑ provide a mild pro-inflammatory potential to avoid an adverse foreign
body response
∑
give a degradation/resorption rate comparable to that of the host repairing
tissue to facilitate complete tissue repair.
Biomaterials for bone tissue engineering will be hereinafter presented
taking into account the requirements for both
in vitro
tissue formation and
in vivo
tissue repair. in both cases, the challenge for the material scientists
is to produce biomaterials with substrate properties that mimic the natural
extracellular matrix of the bony tissue. as these characteristics have to be
ideally coupled to degradation/resorption, only biomaterials able to degrade/
resorb will be presented. Owing to the bone physicochemical properties
to be mimicked, the examples that will be provided will inevitably fall
within the categories of polymeric and ceramic materials, and their relative
composites.
Furthermore, it has to be observed that extracellular matrix mimicry can
target the cell substrate role played by the natural tissue in different phases.
More specifically, a biomaterial can favour cell adhesion, either resembling
the physicochemical properties of the mature natural tissue (e.g. chemistry,
surface topography and surface tension/wettability) or the physicochemical
properties and biorecognition processes of the bone tissue during its different
phases of formation.
in the case of biomaterials that aim to simulate mature bone, it is obvious
that their preponderant feature has to be mimicry of the bone mineral phase.
as described early in this topic (Part i, Chapter 2), this is composed of
