Biomedical Engineering Reference
In-Depth Information
10.3.3
Cell Infiltration
Atechnicalconcernwiththeuseofelectrospinningisthesmallpore
size, which may limit cellular infiltration into the nanofibrous scaf-
fold.Forcellmigrationorinfiltrationtooccur,theporesizeofascaf-
fold should be greater than the size of a cell; a value of 10
μ
mhas
beensuggestedastheminimumporesizenecessaryforcellularinfil-
tration.Asanexample,intheengineeringofbloodvesselsusingelec-
trospun nanofibrous scaffolds, pore size does not present a major
problemwithrespecttocoatingthelumenusingEC.However,itmay
limit the ability of smooth muscle cells (SMC) to colonize the outer
portionoftheneovesselandremodeltheECM.Toovercomethislim-
itation, several approaches have been designed to generate larger
pores within electrospun scaffolds. These include the use of a salt-
leachingtechnique
33
,
34
andco-electrospinningwithawater-soluble
polymerassacrificialfibers.
35
However,theseapproachesmaycom-
promise the mechanical properties and dimensional stability of the
scaffold when the fibers dissolve and collapse. Microintegration is
another approach developed by Stankus
et al
.
36
for producing a
highlycellularizedconstruct.However,thisprocessmaylimithomo-
geneity, sterility, and cell survival, due to the long-term processing
times required.
Controlled variables of electrospinning include the solution con-
centration,flowrate,electricfieldstrength,distancebetweentipand
collector, needle tip design, and collector composition and geome-
try. These parameters can determine the fiber morphology, diam-
eter, and alignment. It is demonstrated that fiber diameter can be
controlled using various parameters, as indicated.
37
,
38
The increase
of fiber diameter of the electrospun fibrous scaffold increases the
poreareaofthescaffold.Toaddressthistechnicalchallenge,studies
have been directed toward evaluating cellular infiltration into elec-
trospun fibrous scaffolds with various fiber diameters. To evaluate
in vitro
cell infiltration, scaffolds with four different fiber diameters
(500 nm, 1
μ
μ
μ
m) were used. NIH/3T3 fibroblasts
were seeded onto electrospun fibrous scaffolds with different fiber
diameters up to 21 days. Figure 10.6 shows that fiber diameters of
the electrospun scaffolds can affect cellular infiltration with time
in vitro
. These results also indicate that fiber diameter is closely
m, 2
m, and 5
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