NOVEL FABRICATION AND CHARACTERIZATION OF PORE-SIZE-GRADIENT SCAFFOLDS BY A CENTRIFUGATION TECHNIQUE - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 600

heattreatmentconditionused.Figure30.8bshowsthatthemechan-
icalstrengthofthescaffoldsections(afterheattreatment)alongthe
longitudinal direction gradually decreased with the increasing pore
size and porosity, similarly to the alginate or chitosan scaffold case.
It was recognized from our preliminary studies that all scaffold sec-
tions(eventhelargest-pore-sizedscaffoldsection;positionfromthe
bottom, 4.0-5.0 cm) have su cient mechanical property for in vitro
cell culture and in vivo animalstudies.

30.3.3 Evaluation of Wettability
The alginate, chitosan and PCL gradient scaffold sections were
observed for their wettability or water absorbability, which is an
essential factor for cell culture and homogeneous tissue regenera-
tion. For this, a cell culture medium was dropped on top of the scaf-
fold, and the time required for complete absorption of the medium
into the scaffold was measured. When the culture medium was
dropped to the scaffold sections, the medium was completely wet-
ted into the alginate and chitosan scaffold sections for all the pore
size ranges since they are natural polymers having hydrophilicity
(Fig. 30.9a).
However, it was not wetted at all into the control PCL scaffold,
owing to its hydrophobic character (Fig. 30.9b). Hydrophilization
of the PCL scaffold sections (by the addition of Pluronic F127, as
treated in this study) allowed the scaffolds to be completely wet-
tedwithinafewseconds,similartothealginateorchitosanscaffolds
(Fig.30.9c).Thefastwettingofscaffoldsintothecellculturemedium
are highly desirable for tissue engineering applications because the
cellscanbedirectlyseededandculturedinthesehydrophilizedscaf-
folds withoutany prewetting treatments.

30.3.4 In vitro Cell Interactions
Selected sections of the pore-size-gradient, cylindrical chitosan and
PCL scaffolds (diameter 14 mm; thickness 2 mm; average pore sizes
∼

80,

∼

190,

∼

270, and

∼

400

μ

m [chitosan] and

∼

88,

∼

200,

∼

310,

and

∼

405

μ

m [PCL]) sterilized by ethylene oxide (EO) were placed