NOVEL FABRICATION AND CHARACTERIZATION OF PORE-SIZE-GRADIENT SCAFFOLDS BY A CENTRIFUGATION TECHNIQUE - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 594

increment of the centrifugal force along the cylindrical axis. After
supernatant removing and freeze-drying, a pore-size-gradient algi-
nate scaffold (height ∼ 5.0 cm) was formed. The prepared alginate
scaffold was further treated by soaking in 1 wt% chitosan solution
to bond alginate fibrils to each other via anion complex and thus to
strengthen the mechanical properties of the scaffold as well as to
prevent the disentanglement of fibrous structures in a cell culture
medium or in the body. The prepared cylindrical alginate scaffold
wassectionedalongthelongitudinaldirectionbycuttingthescaffold
using a blade after being frozen in liquid nitrogen to characterize it
in terms of scaffoldpore sizes(section thickness 5 mm).
30.2.3 Pore-Size-Gradient Chitosan Scaffolds
Chitosan solution (2 wt% in 0.1 M acetic acid) was slowly dropped
into 0.05 M NaOH (nonsolvent for chitosan) with vigorous agita-
tion using a homogenizer (20,000 rpm) to obtain fibril-like chi-
tosan precipitates. The prepared fibril-like chitosans were washed
inexcesswatertoremoveresidualNaOH(Fig.30.2).Thenthefibril-
like chitosan-suspended solution was poured into a cylindrical PP
mold, and centrifugation was carried out, same as the fabrication
methodforthealginatescaffoldabove.Duringthefreeze-drying,the
somewhat sticky chitosan fibrilswere bondedto each other.
30.2.4 Pore-Size-Gradient PCL Scaffolds
PCL and Pluronic F127 (1/1.5, w/w) were heated together to
120 ◦ C with vigorous agitation using a homogenizer (20,000 rpm)
until a homogeneous molten phase was formed. The Pluronic F127
blended with PCL helps to reduce the viscosity of molten PCL and
also provides the hydrophilicity in the prepared PCL scaffold. The
PCL/PluronicF127mixturewasslowlydroppedintowater(nonsol-
vent for PCL) with vigorous agitation using a homogenizer (20,000
rpm) to obtain fibril-like PCL precipitates (Fig. 30.2). The prepared
fibril-like PCLs were washed in excess water to remove residual
Pluronic F127. Then the fibril-like PCL-suspended solution was
poured into a cylindrical PP mold, and centrifugation was carried
out, same as the fabrication method for the alginate or chitosan