Biomedical Engineering Reference
In-Depth Information
3DF is an FDM technique as molten polymeric biomaterials,
hydrogel, and paste biomaterials are extruded from a CAM-
controlled robotic unit on a stage in the form of a fiber. These fil-
aments are deposited to form a layer, and a 3D scaffold could be
built with a layer-by-layer strategy following a CAD pattern. Differ-
ent fiber architecture might be performed by altering the angle of
deposition between subsequent layers, resulting in different pore
shapes. Recently, in order to improve more delicate scaffolds, a mul-
tidispensing system was used for depositing different materials at
thesametimetoproduceconstructswithdifferentphysicochemical
properties. The drawback of this method might be the high temper-
atures involvedduring fabrication of molten polymers.
1.3.1.7 Injectable gel method
Injectable gel scaffolds also have been reported and explained in
section 1.3. An injectable, gel-forming scaffold may provide several
advantages such as it (i) can fill any shape of defects due to flow-
ablematerials,(ii)mayloadvarioustypesofbioactivemoleculesand
cells by simple mixing, (iii) does not contain residual solvents that
may be present in a performed scaffold, and (iv) does not require a
surgical procedure for placement. Typical examples are thermosen-
sitive gels such as Pluronics and PEG-PLGA-PEG triblock copoly-
mers, pH-sensitive gels such as chitosan and its derivates, ionically
cross-linked gels such as alginate, and fibrin gels, hyaluronan gels,
etc., as already introduced in section 1.2. In the near future, multi-
functional gels such as tissue-specific injectable scaffolds materials
with very fast sol-gel transition and that can be fully degradable for
a desired period willbepresent.
Also, newly hybridized fabrication techniques such as organic/
inorganic and synthetic/natural at the nanosized level to biomimic
are continuously developed for the application of tissue-engineered
scaffolds.
1.3.2
Physicochemical Characterization of Scaffolds
For the successful achievement of 3D scaffolds, several charac-
terization methods are needed. These can be divided into four
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