Biomedical Engineering Reference
In-Depth Information
PLLA nanofibrous scaffolds with large interconnected pores by using a low-
temperature electrospinning technique first described by Simonet et al.
122
with ice crystals serving as removable templates. Subsequently, the scaf-
folds were seeded with 3T3/NIH fibroblasts, and as a result good infiltration
of the cells up to 50 μm thickness was observed.
121
PLLA fibers can also be
blended with other substances. For instance, in a study by Kim et al.
123
PLLA
fibers were mixed with fibers spun from bioactive glass. The scaffold cre-
ated exhibited an even distribution of both fibers. When seeded with 3T3-E1
osteoblasts, the cells showed favorable attachment and proliferation, as well
as an improved differentiation and mineralization behavior, as compared
with cells seeded onto pure PLLA scaffolds.
Also, PLGA is a biocompatible material and has a tunable biodegradabil-
ity, depending on the ratio of lactic to glycolic acid.
53,59
Seeding fibrous PLGA
scaffolds with MSCs was found to result in good proliferation in the first
week of culturing. However, after this week, no further effect of the scaffolds
on the cells was noted.
48,53
Like PLLA, PLGA can also be blended with other
substances, for instance with αTCP nanoparticles as described by Schneider
et al.
124
After immersing the scaffolds in SBF and subsequent seeding of the
scaffolds with human MSCs, an increase in proliferation and differentiation
of the cells was seen, as compared with pure PLGA electrospun scaffolds.
Another frequently used synthetic polymer for electrospinning is PCL. MSCs
seeded onto electrospun PCL microporous scaffolds were reported to migrate
through the entire scaffold, to differentiate into osteoblastic cells, and to form a
calcified matrix.
53,61
Blending PCL with a high CaCO
3
content during the elec-
trospinning procedure and subsequent seeding of the material with osteoblasts
resulted in low proliferation of the cells and high mineralized matrix forma-
tion.
125
Another material blended into PCL nanofibrous constructs was nHA.
Seeding of these scaffolds with human osteoblasts, however, was not successful
and resulted in comparable proliferation to plain PCL scaffolds.
126
4.4.2.2
In Vivo
Studies on Nanofibrous Constructs
In addition to
in vitro
studies, several
in vivo
experiments with nanofibrous con-
structs have been performed. Implanting electrospun scaffolds of silk fibroin
material in critical-sized calvarial defects in New Zealand white rabbits showed
complete healing of the defects without observing any inflammatory reaction,
thereby proving the material to be osteoconductive as well as biocompatible.
127
Synthetic electrospun PLLA scaffolds with large interconnected pores
were produced by low-temperature spinning with ice crystals serving as
removable templates and were also tested
in vivo
. As a control, conventional
spun PLLA scaffolds with small nonconnected pores were used. After 14,
28, and 56 days of subcutaneous implantation in rats, the scaffolds were his-
tologically examined. Both materials showed good biocompatibility but the
scaffold with large interconnected pores showed higher cell infiltration and
proliferation.
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