Biomedical Engineering Reference
In-Depth Information
4.4.2 Nanofiber-Cell Interaction
Electrospun materials facilitate, or even enhance, cell growth and differ-
entiation, thereby qualifying these fibers as an excellent material for tissue
engineering purposes. The interaction between cells and scaffold material is
dependent on material properties such as the degradation rate and the flex-
ibility. Slow-degrading polymers provide scaffolds with a longer-lasting sta-
bility. Flexibility of the materials allows cells to migrate through the matrix
by pushing the fibers aside, which is important since the pores created in
nanofibrous materials are often smaller than the size of a single cell.
1 3 , 4 7, 7 7
4.4.2.1
In Vitro
Studies on Nanofibrous Constructs
Many nanofibrous materials from nature-derived, as well as synthetic, poly-
mers have been elaborately tested for their suitability as tissue engineering
scaffolds. For example, collagen type I, electrospun into a fibrous scaffold,
showed excellent proliferation and infiltration of smooth muscle cells in
several studies, even though the pore diameter was smaller than the cell
diam eter.
53,56
These studies were followed by seeding chondrocytes onto a
collagen type II scaffold, on which the cells proliferated and were evenly
distributed, after 1 week.
4 7, 11 7
The disadvantage of using collagen, however, is
the possibility of immunogenic reactions.
48
A second material of choice is chitosan because of its known biocompat-
ibility, degradability, and even an antimicrobial and antifungal activity. The
physical characteristics provide this material with favorable plasticity and
adhesiveness for many applications.
48
When blended with nHA and seeded
with human fetal osteoblasts, this scaffold significantly stimulated prolifera-
tion and mineral deposition after 15 days.
118
In addition, fibrous gelatin scaffolds are biocompatible and bioresorbable,
and when blended with nHA and PCL, good attachment and proliferation of
bone marrow stromal cells was shown.
4 7, 4 8 , 11 9
Finally, the natural material silk has also been shown to be cytocompat-
ible. Seeding electrospun silk/polyethyleneoxide scaffolds with human
MSCs resulted in proliferation of the cells, and addition of nHA and bone
morphogenetic protein 2 (BMP-2) to the scaffold resulted in high calcifica-
tion values. It was therefore concluded that the addition of nHA and BMP-2
significantly improves the osteoconductivity/inductivity of this specific type
of scaffold.
4 7, 7 7
PLLA is one of the synthetic polymers often used for bone tissue engi-
neering purposes because it is biocompatible, biodegradable, and has a high
tensile strength. When seeded with 3T3-E1 osteoblastic cells, nanofibrous
PLLA films showed an increase in differentiation of the cells, as evidenced
by higher ALP activity, an increase in bone sialoprotein (BSP) gene expres-
sion, and a decrease in proliferation of the cells, compared with flat PLLA
films.120
120
To overcome the low pore size and lack of interconnectivity that is
present in conventional electrospun PLLA scaffolds, Leong et al.
121
created
