Biomedical Engineering Reference
In-Depth Information
temperatures are associated with the removal of the unreacted
polymer. Also many scaffolds will shrink as a result of curing, lead-
ing to changes in the controlled architecture and possible cracking
of the scaffolds. Shrinking on the order of 25% following curing has
been reported in the literature.
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Despite these drawbacks SLA rep-
resents a promising technique to manufacture scaffolds with con-
trolled architecture forbonetissue engineering.
25.2.2
Biological Implications
Several studies have been completed to test
in vitro
cell growth and
in vivo
bonegrowthwithinscaffoldsmanufacturedbySLA.
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,
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In a study designed to test the ability of the SLA-developed scaf-
folds to support bone growth
in vivo
, porous hydroxyapatite (HA)
scaffolds with a porosity of 40% were developed using an indirect
SLA approach.
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,
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These scaffolds were created with two different
architectures,orthogonalandradial,bydevelopingamoldusingSLA
and forming a scaffold around it. The scaffolds were implanted into
porcine mandibles, and bone ingrowth was evaluated by scanning
electron microscopy (SEM) and toluene blue staining. The amount
of bone ingrowth was quantified using histomorphometry, and the
architecture of the scaffold was shown to influence the amount of
the regenerated bone as the orthogonal scaffolds had a larger bone
growth area than the radial scaffolds. Scaffold architecture was also
shown to influence bone geography, as the orthogonal HA scaffolds
formedaninterpenetratingmatrix,whiletheboneintheradialscaf-
foldsformedinanintactpieceinthecenterofthescaffold.Theshape
of the new bone greatly influences the mechanical properties of the
regenerated tissue, and thus it is important to develop scaffolds
with controlled architecture to induce proper regenerated bone
formation.
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,
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Most solid freeform scaffold fabrication techniques
involveseedingcellsontothesurfaceofthescaffold.Thoughthiscan
be effective, it is di
cult to achieve a uniform distribution of cells
throughoutthescaffoldusingthismethodasthecellseedingisinflu-
enced by diffusion and architecture of the scaffold. In another study
utilizing SLA a method was devised to encapsulate cells directly
into the scaffold using a photopolymerizable poly(ethylene oxide)
(PEO) and poly(ethylene glycol) diacrylate (PEGDA) hydrogel.
37
In
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