Biomedical Engineering Reference
In-Depth Information
successful application for the regenerative medicine and tissue
engineering scaffolds of these natural polymers,
in vivo
and
in vitro
experiments and physicochemical modification must be performed
in the near future.
1.2.5
Bioactive Molecules Release System for the
Regenerative Medicine and Tissue Engineering
Bioactivemoleculesasgrowthfactorsarepolypeptidesthattransmit
signals to modulate cellular activity and tissue development such as
cellpatterning,motility,proliferation,aggregation,andgeneexpres-
sion. As in the development of the tissue-engineered organs, regen-
erationoffunctionaltissuerequiresmaintenanceofcellviabilityand
differentiated function, encouragement of cell proliferation, modu-
lation of the direction and speed of cell migration, and regulation of
cellularadhesion.Forexample,transforminggrowthfactor-
β
1
(TGF-
β
1
) might be required to induce osteogenesis and chondrogenesis
from bone marrow-derived mesenchymal stem cells. Also, brain-
derived neurotrophic factor (BDNF) can be enhanced to regenerate
spinal cord injury.
Also small molecules can control the differentiation of stem cells
tospecifiedcells.Hydroxybutylateor
β
-mercaptoethanolcanbedif-
ferentiated to neuronal cell from bone marrow-derived mesenchy-
mal stem cells.
The easiest method for the delivery of the bioactive molecules is
the injection near the site of cell differentiation and proliferation.
2
,
3
Themostsignificantproblemofthedirectinjectionmethodofbioac-
tive molecules is the relatively short half-life, the relatively high
molecular weight and size, very low tissue penetration, and poten-
tial toxicity of systemiclevel.
34
One promising way of the improvement technique of their e
-
cacy is the locally controlled release of bioactive molecules for a
desired release period by the impregnation into a scaffold. Through
impregnation into a scaffold, protein structure and biological activ-
ity can be stabilized to a certain extent, resulting in prolonging the
release time at the local site. The duration of bioactive molecules
releasefromascaffoldcanbecontrolledbythetypesofbiomaterials
used, the loading amount of cytokine, the formulation factors, and
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