Biomedical Engineering Reference
In-Depth Information
engraftment, proliferation, and differentiation and to encourage cell
migration from surrounding tissue.
Biodegradable scaffolds produced from a bioabsorbable polymer
are frequently utilized for seeding with cells. In addition, liquid
scaffolds mixed with cells can be directly injected into a diseased
site or gelated and poured into a mold. Biodegradable scaffolds are
classified into groups based on structural proteins, bioabsorbable
materials, and decellularized matrix scaffolds. Since scaffolds can be
easily constructed, their advantage is being able to assemble new
tissue conveniently. With these methods, various tissues or organs
such as skin, cornea, cartilage, bladder, and vessels have been
investigated and applied in clinical settings.
4a.2
Natural Hydrogels
Biodegradable natural hydrogels made from biogenic proteins (e.g.,
collagen, gelatin, and fibrin) and polysaccharides (e.g., alginate
and hyaluronic acid) are commonly utilized as scaffolds in tissue
engineering (Fig. 4a.1). However, ECM-derived animal proteins are
rarely used by researchers because of the potential immunoreaction
or infection [4-6].
4a.2.1 Collagen
In mammals, collagen, especially type I collagen, is the major protein
component of intravital connective tissue and organs and makes up
the fibrotic ECM scaffolds of skin, bones, tendons, and many other
tissues [7, 8].
Collagen gel used as a hydrogel in tissue engineering facilitates
adaptation to in vitro culture and can affect the maintenance of cell-
specific morphology and function [9-11]. For example, hepatocytes
cultured using type I collagen maintained their function, ability to
differentiate, and gene expression level [12, 13]. However, the growth
of several different cells cultured in type I collagen is inhibited,
for example, smooth muscle cells [14], melanoma cells [15], and
glomerular epithelial cells [16]. Recombinant human collagen in the
form of a sponge or gel used for engineering of human tissues is an
effective scaffold to reconstruct bone, skin, cartilage, and periodontal
ligaments [17].
