Biomedical Engineering Reference
In-Depth Information
by the beam of the laser used, which has a typical beam thickness
of 400 μ m. This creates a technological limitation to the resolution
achieved via SLS.
25.4.2 Biological Implications
ScaffoldsdevelopedbyindirectSLShavebeenshowntoinducebone
growth when seeded with bone marrow stromal cells. 67 The scaf-
foldsinthisstudywereformedfromamoldconstructedviaSLS,and
two experimental groups were created (smooth and textured), as
wellasanonmoldedcontrol.Theuseofamoldprovidedforahighly
controlled macrostructure but the potential for variability in the
microstructure of the scaffolds. This microstructure was shown to
have a significant effect on the seeded cells as increased cell attach-
mentwasobservedonsurfacesofthescaffoldwithtexturedsurfaces
(grooves
m wide). Cell density was higher
on the textured outer surface of the scaffold, revealing that the tex-
tured surface influenced the cell distribution. In addition areas of
the scaffold with textured surfaces demonstrated an increased for-
mation of budding bone, as shown by histology, though the total
amountofnewboneareawasnotdifferentbetweenthesmoothand
textured scaffolds. Two different scaffold properties likely caused
theincreasedbonebuddingonthetexturedsurface.First,increased
surface texture leads to a greater surface area for cells to adhere
andthereforeinfluencescelldistribution.Second,calciumandphos-
phate have been shown to enhance bone formation; therefore it
is hypothesized that the increased degradation of the scaffold at
areas of surface texture leads to increased local concentrations of
calcium and phosphate and enhanced in vitro bone formation. This
studydemonstratedaneffectiveuseofcell-seededbonetissueengi-
neering scaffolds developed by SLS and provided evidence for the
need for scaffolds with controlled architecture. In another study
involving SLS and bone tissue engineering, a significant amount of
in vivo bone formation was shown four weeks following seeding
in an SLS-manufactured scaffold with primary human fibroblasts
infected with a BMP-7 gene that causes the cells to produce bone. 6
Thecell-seededscaffoldswereimplantedsubcutaneouslyintomice,
andbonegrowthwasdetectedusing
25
μ
m deep and
40
μ
μ
CTandhematoxylinandeosin
 
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