Biomedical Engineering Reference
In-Depth Information
implanting the scaffold materials in animals and subsequently
observing the reactions of the animals to the materials. Informa-
tion on the last item cannot be obtained without conducting bio-
logical research. The last item is a desirable property, that is, the
activity of the scaffolds to influence the proliferation and differen-
tiation of transplanted and host cells to actively induce regenera-
tion. If realized, it will dramatically enhance the performance of the
scaffolds.
In the current paper, we would like to take up bone tissue engi-
neeringasanexample,discusswaystooptimizetheperformanceof
scaffolds, and point out a pivotal role of the 3D shape control of the
scaffolds.
29.2 Current Status of Artificial Bones
Reconstructive surgery using autograft, allograft, and artificial
bones has been performed to treat craniofacial bone deformities.
3
An autograft is superior to the other techniques in function and
engraftment because it is a bone tissue derived from the same
individual, containing live cells and growth factors. An autograft
has both the ability to facilitate bone regeneration (osteoconductiv-
ity) and the ability to actively induce bone regeneration (osteoin-
ductivity) and is speedily fused and integrated to the bone of the
implantation site. However, because this process requires highly
invasive bone collection surgery from healthy sites, donor site mor-
bidityoftenoccurswiththequantityoftheautograft beinglimited.
4
Although an allograft is usually collected from cadavers and thus
is free from the invasiveness to the recipient and less restricted in
quantity, it runs a biological risk of contamination by pathogens as
well as an ethical risk associated with illegal body trading.
5
Because
an allograft is usually heat-treated and kept frozen in order to
reduceimmunologicalreactions,nolivecellsarepresentandgrowth
factors are inactivated to some extent. Therefore, its osteoconduc-
tivity and osteoinductivity are inferior to those of an autograft.
These factors cause an allograft to fail more often than an autograft.
In addition, common to the both procedures, the graft has to be
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