Biomedical Engineering Reference
In-Depth Information
transplantation of large volumes of constructs cannot survive
because of diffusion limitations that restrict interaction with the
host environment for nutrients, gas exchange, and elimination of
waste products. Therefore, implanted cells survive poorly under
such conditions.
14
Scaffolds used usually in therapeutic applications are made
from natural or synthetic polymers that are often resorbed or
degraded in the body. In degradable scaffolds, several key chal-
lenges exist. First, the primary generation of degradable polymers,
widely used in regenerative medicine, was adapted from other sur-
gical uses and has deficiencies in terms of mechanical and degra-
dation properties.
15
The second major challenge is how to fabricate
these polymers into scaffolds that have defined shapes and a com-
plex porous internal architecture that can direct tissue growth.
16
In
nondegradable scaffolds, which are rarely used for skin substitutes
in these days, a major challenge is how foreign-body reactions are
reduced.Andalso,thesepolymersandtheirdegradationproductsas
well as nondegradable polymers must also be nontoxic and nonim-
munogenicuponimplantation.Theidealsyntheticbiomaterial,such
aswounddressing,andbiologicskinsubstitutesshouldhavethefol-
lowing characteristics, listed by Pruitt
et al.
17
,
18
•
absence ofantigenicity
•
tissue compatibility
•
absence oflocal or systemictoxicity
•
impermeability forexogenousmicroorganisms
•
water vapor transmission similar to normal skin
•
rapid and sustained adherence to woundsurface
•
conformance to surface irregularities
•
elasticity to permit motionof underlying tissue
•
resistance to linear and shear stress
•
tensile strength to resist fragmentation
•
inhibitionof woundsurface flora and bacteria
•
long shelf life, minimalstorage requirements
•
biodegradability (for permanent membranes)
•
low cost
•
minimizationofnursing care of wound
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