Biomedical Engineering Reference
In-Depth Information
5.1 Conclusions
The use of synthetic materials for scaffolds allows the manipulation of chemical
properties by copolymerization, mechanical properties by changing the ratio of
chemical polymers involved, as well as introducing different architectural designs
(connected pores in triangles, pentagons, and honeycombs) to the scaffold. In the
creation of such scaffolds, controlling the degradable nature of the biomaterial is
crucial [
4
,
41
]. Degradability ultimately relies on the chemical structure, architec-
ture, and morphology of the scaffold, so a synthetic material that contains copoly-
mers associated with crystalline materials are the most promising [
4
]. With these
approaches and considerations, synthetic bone scaffolds carry enormous potential
and thorough investigation into their designs will help optimize engineered bone
regeneration.
6 Biologically-Based Scaffolds
Of the many different materials that could be used for biological bone scaffolds, hy-
droxyapatite (HA) is considered the most promising since it is a very strong osteoin-
ductive factor [
4
]. The chemical formula for hydroxyapatite is Ca
10
(PO
4
)
6
(OH)
2
.
Other materials containing calcium phosphate have been used as biomaterials for
bone repair and regeneration [
4
]. The main advantage of using materials like hy-
droxyapatite, or any other synthetic calcium phosphate biomaterial is that these ma-
terials are much more biocompatible and stable than other synthetic materials when
implanted in the body [
4
].
Although calcium phosphate biomaterials are better at regenerating bone, and are
therefore promising bone substitute materials, these materials are inherently brittle
in nature. This problem is generally solved by combining the crystalline biomateri-
als with polyesters [
4
]. This produces a scaffold that has the strong osteoinductive
nature of the calcium phosphates, combined with the biodegradable and reactive
nature of polyesters, allowing cell attachment to occur. To this end, many inves-
tigations with calcium phosphates or hydroxyapatite in combination with poly(
ε
-
caprolactone) (PLC) or poly(lactide) (PLA) have been performed to produce poten-
tial bone substitutes [
4
]. It is hypothesized that the osteoinductive effects of these
scaffolds can be attributed to their structural similarity to the extracellular matrix
content of endogenous bone.
The mechanical properties of biologically-based bone scaffolds can also be mod-
ulated by cross-linking with different compounds [
4
]. For instance, it has been
shown that crosslinking of calcium sulfate and poly(propylene fumarate) produces
a scaffold with mechanical properties close to that of cortical bone, with a compres-
sive strength of 5 MPa [
4
,
42
]. In a different study, cross-linking with atelocollagen
produced an injectable form of a bone substitute, which could be more effective for
clinical use than implantable scaffolds. Hydroxyapatite-atelocollagen cross-linked
compounds have been shown to promote ossification [
4
,
43
]. However, despite this
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