NOVEL FABRICATION AND CHARACTERIZATION OF PORE-SIZE-GRADIENT SCAFFOLDS BY A CENTRIFUGATION TECHNIQUE - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 602

the scaffold sections, owing to their hydrophilic character, and thus
directly seeded without any prewetting treatment. The cell-seeded
scaffold sections were maintained for two hours at 37 ◦ Cinanincu-
bator with humidified 5% CO 2 atmosphere for cell adhesion to the
scaffoldsections.Thenthescaffoldsectionsweretransferredtonew
12-well PS dishes, the culture medium was added to the culture
plate (3.0 mL/well), and the cells in the scaffold sections were cul-
tured up to eight weeks with mild shaking (about 50 rpm). The cul-
ture medium was changed into a fresh one every day during the cell
culture periods. The cells were cultured in the scaffold sections for
givenperiods(1,7,14,28,and56days),andtheviablecellnumbers
in each specimen were estimated by the 3-(4,5-dimethylthiazol-2-
yl)-2,5-diphenyltetrazoliumbromide(MTT)assaymethod,asshown
in Figs. 30.10 and 30.11. The pore-size-gradient scaffold sections
showed over 90% cell-seeding e ciencies (after the cell-seeded
specimens were maintained for one day at 37 ◦ CinaCO 2 incubator
forcelladhesion),indicatingthatthescaffoldsfabricatedbythecen-
trifugation method satisfied the requirements for cell scaffolds, that
is, highly porous and interconnected pore structures. The cells were
grown in the scaffold sections without significant differences up to
14 days, regardless of cell types, pore sizes, and scaffolds. There-
after, the different types of cells showed different growth behaviors
inthescaffolds;thechondrocytesandosteoblastsshowedbettercell
growth in the scaffold sections having larger pore sizes, while the
fibroblasts showed best cell growth in the scaffold sections having
pore size about 200 m. Generally the cells need the pores to be

large enough to allow them to migrate into the pores of the scaffold
and to allow effective nutrient supply and metabolic waste removal,
which are essential for effective cell growth, but to be small enough
to establish a su ciently high surface area for e cient binding to
the scaffold and cell-cell interactions for better cell growth, as dis-
cussed earlier. The exact mechanism of different growth behavior
of different types of cells in the scaffolds with different pore sizes
is not clear yet. However, the result of Figs. 30.10 and 30.11 sug-
gest that the chondrocytes and osteoblasts may prefer larger pores
(betterconditionsfore cienttransportofnutrientsormetabolites)
for their growth, while the fibroblasts seem to prefer smaller pores
(more surface areas for cell attachment and signaling).

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