Biomedical Engineering Reference
In-Depth Information
to the ability of the graft to support the attachment of cells and allow new
cell migration and vessel formation. the osteoinductive quality of scaffolds
describes their ability to induce non-differentiated stem cells or progenitor
cells along an osteogenic lineage. the scaffold should not elicit an immune
response. Maximizing the porosity of the scaffold to promote cellular and
neovascular ingrowth must be balanced by the need to maintain the structural
integrity of the lattice (table 6.1).
2
Metals and ceramics are classically employed materials in bone engineering
mainly because of their mechanical properties. Moreover, bone structure is
very similar to that of many ceramics. nevertheless, metal implants cannot
perform as efficiently as a healthy bone, and metallic structures cannot
remodel with time because they lack the capability of osteogenic regeneration.
Most of these materials are not biodegradable, and therefore, might require
subsequent surgical procedures. recent advances in materials science have
provided an abundance of innovations, which has led to the increasing
importance of polymers in this field.
to help address the need for better bone substitutes, bone tissue engineers
Table 6.1
Synthetic and natural polymers for bone tissue engineering
Material
Characteristics
Poly(
a
-hydroxy
acids)
Extensively studied aliphatic polyesters
Degradation by hydrolysis
Already approved for other health related applications
Acidic by-products (e.g. lactic acid, glycolic acid), that enter
the tricarboxylic acid cycle or alternatively (e.g. glycolic acid)
are excreted in the urine
Problems regarding biocompatibility and cytotoxicity in the
surrounding area of the implantation site
Poly(
e
-caprolactone) Aliphatic polyester
Degraded by hydrolysis or bulk erosion
Slow degrading
Degradation products incorporated in the tricarboxylic acid cycle
Low chemical versatility
Some problems related with withstanding mechanical loads
Poly(anhydrides)
Mainly developed as drug delivery carriers
Biocompatible
Support both endosteal and cortical bone regeneration
Poly(propylene
fumarates)
Unsaturated polyester consisting of alternating propylene
glycol and fumaric acids
Main degradation products are fumaric acid and propylene
glycol
Satisfactory biological results
Adapted from Salgado
et al
.
2
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