Biomedical Engineering Reference
In-Depth Information
particles such as sodium chloride crystals, sodium tartrate, and
sodium citrate sieved using a molecular sieve.
1
,
13
,
15
,
25
,
27
,
28
,
31
,
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These methods have been broadly used to make 3D scaffolds in the
wholearea of the scaffoldsof tissue engineering.
PLGA, PLA, collagen, poly(
ortho
ester), or SIS- and DBP-
impregnated PLGA scaffolds were successfully fabricated with a
biodegradable sponge structure by this method with above 93%
porosity and desired pore size of 1,000
μ
m. Using the solvent-
casting/particulate-leaching method, complex geometries such as
tube,nose,andspecificorgantypes,notsomuchasnano-composite
hybrid scaffolds, could be fabricated by means of conventional poly-
merprocessingtechniqueslikecalendaring,extrusion,andinjection.
Complex geometry can befabricated from porous film lamination.
39
Theadvantageofthismethodiseasycontrolofporosityandgeome-
try. However, disadvantages of this method are (i) the loss of water-
soluble biomolecules or cytokines during leaching of the porogen,
(ii) the possibility of porogen remaining as salt that can harmfully
affect cell culture, (iii) the different geometry surface and cross sec-
tion,and (iv)pore tortuosity.
1.3.1.4 Gas-foaming method
The gas-foaming method is a sudden expansion of CO
2
gas under
high pressure, resulting in the formation of a sponge structure
because of the nucleation and expansion in the dissolved CO
2
scaf-
fold matrix. PLGA scaffolds with above 93% porosity and around
100
μ
m median pore size were developed by this method.
40
The
significant advantage is no loss of bioactive molecules in the scaf-
fold matrix due to no need for the leaching process and no residual
organic solvent, whereas the disadvantage is the presence of skim-
mingfilmlayersonthescaffoldsurface,resultinginanotherprocess
to further remove this skinlayer.
1.3.1.5 Phase separation method
The phase separation method is divided into freeze-drying, freeze-
thawing, freeze-immersion precipitation, and emulsion freeze-
drying.
14
Phase separation by freeze-drying can be induced in a
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