Biomedical Engineering Reference
In-Depth Information
regeneration. Hyalomatrix PA, Hyalograft 3D, and Laserskin are just a few of
the hyaluronan-based commercial skin grafts available for wound dressing.
Chondroitin Sulfate (CS)
:CSoccupiesaround80%ofglycosaminoglycan
(GAG), a major component of articular cartilage. CS is a disaccharide com-
posed of glucuronic acid and
N
-acetylgalactosamine as shown in Fig. 4. An
oral intake of CS has been identified to alleviate the symptoms of OA, and
is commonly sold in USA as a dietary supplement. CS-based hydrogels have
been used for cartilage tissue regeneration in order to achieve enhanced
cell proliferation and proteoglycan secretion [184-186]. Sechriest et al. have
shown that a monolayer of bovine articular chondrocytes plated on CS-
chitosan composite expressed focal adhesions and maintained the character-
istic chondrocyte phenotype [187]. Chang et al. have applied a tri-copolymer
scaffold containing gelatin, CS and HA as a scaffold for cartilage tissue en-
gineering [188]. In our laboratory, we have modified CS by incorporating
methacrylate groups such that it can be photo-polymerized into a hydrogel
and therefore can be used as a minimally invasive tissue engineering scaffold
for cartilage replacement [185].
Similar to HA, CS has also been explored for wound healing applications in
the past. Prestwich and coworkers have shown that wound dressings contain-
ing both HA and CS enhance the re-epithelization of the wound [173, 189].
Like HA and collagen, CS is also physically weak and degrades rapidly in
vivo, but the formation of a hydrogel improves its mechanical properties and
degradation rate. Other than being used as a scaffold component, our lab-
oratory has also explored the possibility of CS-based polymers as a tissue
adhesive for ophthalmology and for integrating the engineered cartilage to
host tissue in the defect site (Wang and Elisseeff, 2005, personal communica-
tion) [98].
Fibrin
: Fibrin is well known for its hemostatic function of preventing
bleeding by forming blood clots, which are structurally similar to hydrogels.
Hence fibrin has been considered as a natural scaffold for supporting wound
healing. This property also makes fibrin glue a global surgical sealant, and
it has been widely used as an adhesive in plastic and reconstructive surgery.
Fibrin glue (hydrogel) is formed by the enzymatic polymerization of fibrino-
gen and thrombin at physiological conditions. The thrombin concentration
present during the gelation influences the structural property of fibrin hydro-
gels and the extent of cell invasion [190, 191].
The most attractive feature of fibrin-based materials is their biological
activity, and many studies have investigated the possibility of using them
as scaffolds for various tissue engineering applications such as cartilage,
bone, cardiovascular, and chronic wound healing [181, 192-194]. Various
research groups have used fibrin glue for cartilage tissue engineering ap-
proaches [195-198]. Silverman et al. investigated the possibility of using
fibrin glue for developing neocartilage in vivo in an athymic mouse and
the biochemical analysis has confirmed that the ultimate tissue formed had
