Biomedical Engineering Reference
In-Depth Information
glass, and polymeric biomaterials alone do not easily integrate into
the host tissue and have a limited lifetime. Furthermore, implanta-
tion generally requires invasive surgery.
4
In the past decade, much
effort has been made in engineering ideal scaffolds for bone tis-
sue regeneration (high porosity, proper pore size, biocompatibil-
ity, biodegradability, osteoinductivity, etc.), but none of the current
materials fulfills all demands. Thus, a broad range of solutions have
been developed for each particular function, for instance, devices
withhighmechanicalstabilityforlargebonedefectsinload-bearing
long bones and moldable or injectable materials for craniofacial
surgery.
1
−
4
In order to avoid the shortage of donor organ and other prob-
lems caused from poor biocompatibility of only biomaterials, a
new hybridized method combined with cells and biomaterials has
been introduced as regenerative medicine and tissue engineering.
2
To reconstruct a new tissue by regenerative medicine and tissue
engineering, triad components such as (i) cells that are harvested
and dissociated from the donor tissue, including nerve, liver, pan-
creas, cartilage, and bone, as well as embryonic stem cells, adult
stem cells, induced pluripotent cells (iPS), or precursor cells; (ii)
biomaterialsasscaffoldsubstrateswhosecellsareattachedandcul-
tured, resulting in the implantation at the desired site of the func-
tioning tissue; and (iii) growth factors that are promoting and/or
preventing cell adhesion, proliferation, migration, and differentia-
tion by up-regulating or down-regulating the synthesis of protein,
growth factors, and receptors are needed, as shown in Fig. 1.1.
1
,
5
In a typical application for cartilage regeneration, donor cartilage
or bone marrow-derived stem cells are harvested from the patient
and dissociated into individual chondrocyte cells using enzymes
such as collagenase and then mass-cultured
in vitro
. The chondro-
cytecellsorchondrogenesisstemcellsusingdifferentiation-induced
molecules are then seeded onto a porous and synthetic biodegrad-
able scaffold. This cell/polymer structure also is massively cul-
tured in a bioreactor. The malfunctioned tissue is removed, and the
cell/polymer structure is then implanted in the patient. Finally, the
synthetic biodegradable scaffold bioresorbs into the body, and the
chondrocyte cells produce collagen and glycosaminoglycan as their
own natural ECM, resulting in regenerated cartilage. This approach
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