Biomedical Engineering Reference
In-Depth Information
fold is a pivotal issue in tissue engineering, and much progress has been made
in this pursuit over recent years, with the development of smart biomimetic
scaffolds being the key contenders [60]. Examples of tissue engineered prod-
ucts using this strategy include Apligraf, Dermagraft, and Orcel, all of which
consist of dermis cells and collagen. These products are mainly used for skin
replacement, in the case of burns and diabetic ulcer. This approach has also
been used for regenerating other tissues such as cartilage, e.g. Hyalograft
C which uses a combination of chondrocytes and a hyaluronan (HA)-based
scaffold [61].
3
Scaffolds in Tissue Engineering
As discussed above, in order to create biologically and functionally active
tissue/organ replacements, cultured cells are grown on or within a scaffold.
The scaffold is expected to provide a specific biological and mechanical en-
vironment to the encapsulated cells. The scaffold also assigns a predefined
architecture to the regenerated tissue. Furthermore, various growth factors
and other bioactive signals and bio-molecules can be loaded into the scaffold
along with the cells to guide the regulation of cellular functions during tissue
development [62-65]. Scaffolding biomaterials can be designed to meet a se-
ries of stringent requirements as described below that are either required or
highly desirable to optimize tissue formation.
1. The matrix should be biocompatible and should promote cell growth.
2. Scaffolds that are designed to encapsulate cells must be able to solidify
without damaging the cells.
3. The scaffold must allow diffusion of nutrients and metabolites between
the encapsulated cells and the surroundings.
4. The scaffold material should degrade in response to the production of
ECM components into noncytotoxic segments for easy elimination. The
degradation of the scaffold also prevents the scaffolds from impeding the
growth of new tissue.
Tissue engineering scaffolds are constructed out of natural and synthetic
polymers. Natural polymers typically comprise of collagen or other proteins,
polysaccharides, fibrin, or other biomolecules. The use of these polymers
to construct hydrogels is discussed later in Sect. 4.1. Synthetic biodegrad-
able polymers used for tissue engineering scaffolds involve FDA-approved
polyesters such as poly(lactic acid) (PLA), poly(glycolic acid) (PGA), and
their copolymer poly(lactic-glycolic) acid (PLGA) (refer to Fig. 2 for their
chemical structures) [66].
Vacanti et al. have reported that poly(glycolic acid) matrices are capable
of supporting the regeneration of musculoskeletal tissues such as cartilage
