Chemistry Reference
In-Depth Information
should determine the three-dimensional shape of the resulting tissue, and
should degrade while the cells are growing and replacing the artificial
structures. The need for scaffolds in tissue engineering is undisputed as cells
cannot survive on their own; cells need a substrate on which to grow.
The choice of scaffold for tissue depends on its characteristics. Besides the
mechanical properties, the optimum design of a scaffold for a specific tissue
application requires consideration of microstructural, chemical and biologi-
cal aspects. In surgical applications, a number of requirements need to be
fulfilled such as surface biocompatibility (chemical structure, topography,
etc.), mechanical compatibility (elastic modulus, strength, stiffness, etc.),
non-toxicity, durability conditions and sterilising properties. Owing to
recent advances in textile engineering and biomedical research, the use of
textiles in surgery is growing, and they have been used in some situations
to replace the functions of living tissues of the human body
23
.
Polymers reinforced with textiles, called polymer composite materials, are
also considered in tissue replacements or with implants such as dental posts,
bone grafts, bone plates, joint replacements, spine rods, inter-vertebral discs
and spine cages
24
. Synthetic biomaterials are reasonably successful, but have
drawbacks compared with living tissues, including a higher risk of infection,
loosening, failure and finally rejection. In a currently developing field of
tissue-engineering, mammalian cells and certain synthetic biodegradable
materials are being combined to produce living (vital) synthetic tissue
substitutes or replacement tissues
25,26
.Tissue engineering already has ap-
plications in engineering skin
27
, blood vessels
28
, heart valve
29
cartilage
30
and
nerve
31
for applications such as replacement of burned skin and restoring
of vital heart functions.
The basic concept of tissue engineering is to regenerate or grow new
tissues by culturing isolated cells from the damaged body on porous
biodegradable scaffolds or templates. A new and innovative step further in
this field is to grow complete organs in such an artificial environment. The
scaffold acts as an extracellular matrix for cell adhesion and growth and/or
regeneration. They can be processed into various shapes and micro-
structures, such as desired surface area, porosity, pore size and pore-size
distribution. Recent progress in electrospinning
32-36
allows scaffolds of
nano-dimensioned structure with a large surface/volume ratio to be
obtained, promoting the adhesion of cells. These aspects are vital, as they
provide the optimal spatial and nutritional conditions for the cells, and
determine the successful integration of the natural tissue and the scaffold.
Fibro-vascular tissues require a pore size greater than 500 mm for rapid
vascularisation, whereas the optimal porosity for bone-bonding materials is
considered to be between 70 and 200 mm. Textile structures have the poten-
tial to be tailored in such a way as to provide the required porosity in terms
of size, quantity and distribution pattern. For example, in a typical textile
