Biomedical Engineering Reference
In-Depth Information
architecture that aids in bone growth and vascularization, and
reproducibility of global architecture. Significant drawbacks to this
technique include the extra steps associated with the indirect pro-
cedure, which include designing a mold, casting a polymer into the
mold, and then adding a microstructure through a traditional fab-
rication technique.
54
In a study utilizing a slightly different 3DP
approach poly(
L
-lactic acid) (PLA) scaffolds were created by mixing
PLA with a salt of different pore sizes and molded into a 3D archi-
tecture using 3DP and the salt was leached out to create pores.
50
These porogen-leaching 3DP scaffolds were made in two different
void fractions (75% and 90%) and pore sizes ranging from 90
μ
m
to 120
μ
m. To test cellular response to this scaffold fabrication
method, three different cell types (canine dermal fibroblasts, vas-
cular smooth muscle cells, and microvascular epithelial cells) were
seeded onto the scaffolds and the viability and extracellular matrix
depositionofthecellswasmeasured.Theresultsdemonstratedthat
the75%voidfractiongroupswerelessoptimalforsupportingcellu-
larinfiltrationthanthe90%voidfractiongroups.
50
Thisstudyhigh-
lights the need for strictly controlled architectures but also high-
lights a weakness of SFF methods utilizing porogen leaching, as the
poresizeswerenotuniforminthescaffoldandwerelargerthanthe
sizeof the salt used.
Abenefitofcontrolledinterconnectivityofscaffoldporesinaddi-
tion to enhancing cellular infiltration is the added utility to use
these scaffolds in a perfusion bioreactor system. Perfusion biore-
actor systems enhance
in vitro
cell culture by increasing nutrient
transfer and replicating
in vivo
mechanical stresses, but these sys-
tems require pore interconnectivity to allow fluid to flow through
the scaffold.
55
Successfully integration of scaffolds formed by 3DP
have been demonstrated in the literature as fluid was easily per-
fused through the 3DP scaffolds and greater interior cell growth
was observed in scaffolds in the perfusion system.
48
In vivo
per-
formance of scaffolds developed by 3DP was also assessed in the
literature.
5
,
56
Scaffolds fabricated using the commercially available
TheriForm
TM
3DP process were made from PLGA of two differ-
ent molecular weights and combined with 20% tricalcium phos-
phate (TCP). Scaffolds incorporated two different architectures: one
withmacroscopicchannelsandanotherwithamicroscopicporosity
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