Biomedical Engineering Reference
In-Depth Information
that the use of nanometals in vascular stent applications can solve problems that
were associated with endothelial monolayer formation.
Poly(butylenes succinate) (PBSU) have good biocompatibility and biode-
gradability but is unexplored for tissue engineering. 206 Thus, Zhao et al., com-
pared PBSU and PLGA scaffolds prepared by electrospinning technique as
vascular tissue engineering materials. Their studies showed that fiber diameter
of the electrospun scaffolds ranged from 300 to 800 nm and their porosities
were higher than 90%. The electrospun PLGA scaffolds gave a maximum ten-
sile strength of 14.31 ± 5.24 MPa while the electrospun PBSU scaffolds showed
a tensile strength of 2.06 ± 0.11 MPa. There was no significant difference in cell
adhesion efficacy between PBSU and PLGA scaffolds, but cell proliferation
rate on PLGA scaffolds was significantly higher than that on PBSU scaffolds
after 7 days of culture. These in vitro studies revealed that the electrospun PBSU
scaffolds showed lower tensile strength and slower proliferation rate than PLGA.
On the other hand, the biocompatibility and pore structure of the electrospun
PBSU scaffolds showed promising application vascular tissue engineering.
6.3.4 Nanomaterials for Bladder Implants
Nanomaterials are also being studied for bladder applications. 169 More than
90% of bladder cancers begin in the urothelium transitional epithelial layer.
These are categorized as superficial and require bladder tissue replacements 166
because these often require the removal of large portions of the bladder or the
entire bladder wall. As a result of biocompatibility and ability to stretch and
relax, polymers are promising replacement materials. Since implant surface
properties undoubtedly impact cellular responses, an important parameter for
achieving maximal cell responses is the material topography. 112 Just like any
natural soft tissue, the bladder has constituent ECM proteins having nanometer
lengths and widths. Thus, the next generation of polymeric bladder construct
materials should incorporate nanodimensional surface characteristics.
The design of synthetic bladder wall substitutes has involved polymers
with microdimensional structures. Nanostructured polymers for use as syn-
thetic bladder constructs that mimic the topography of natural bladder tissue
has been studied in vitro. 166 In this study, novel nanostructured biodegradable
polymeric films of PLGA ( Figure 6.6 ), poly-ether-urethane (PU, Figure 6.7 ),
and poly-caprolactone (PCL) were fabricated and separately treated with vari-
ous concentrations of NaOH (for PLGA and PCL) and HNO 3 (for PU) for
select time periods. The results provided the first evidence that adhesion of
bladder smooth muscle cells was enhanced as polymer surface feature dimen-
sions were reduced into the nanometer range. Surface analysis revealed that
the polymer nanometer surface roughness was the primary design parameter
that increased bladder smooth muscle cell adhesion. Results from their studies
provided the first evidence that bladder smooth muscle cell adhesion and prolif-
eration were enhanced on polymeric surfaces with nanodimensional, compared
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