Biomedical Engineering Reference
In-Depth Information
cartilage-like properties [199]. Additionally, the adhesive property of fibrin
has also been utilized for skin repair, bone grafts, and targeted immobiliza-
tion of various cells [181, 200, 201]. Horch et al. utilized Fibrin glue (Tisseel)
for keratinocyte transplantation in burn patients and their findings suggest
the feasibility of using fibrin glue to treat chronic wounds [202]. Recently
Curri et al. reviewed the role of fibrin glue in the development of tissue engi-
neered skin grafts [203]. One of the major concerns of using fibrin glue is that
it poses a potential immunological threat since it can carry life-threatening
viruses such as HIV. In order to prevent this potential immunologic threat,
fibrin can be produced from the patient's own blood to use as an autologous
scaffold.
Chitosan
: It is a linear polysaccharide composed of
D
-glucosamine and
N
-acetyl-
D
-glucosamine residues (see Fig. 4 for chemical structure) and is
derived from chitin, a polysaccharide found in the exoskeleton of shellfish.
Chitosan is semi-crystalline in nature and its crystallinity varies with the
degree of deacetylation. Chitosan can also be used in a minimally invasive
manner because it can undergo thermal and pH-triggered gelation [204], and
is biodegradable as it can be enzymatically degraded in vivo by lysozyme
and chytosanasitase enzymes. The biocompatibility and cationic nature of
chitosan has been explored for a variety of biomedical applications such
as gene delivery [205], wound dressings [206-208], and space-filling im-
plants [209, 210].
Chitosan is structurally similar to GAG and hence has been widely used as
a cartilage scaffold for tissue engineering applications in recent years [211-
214]. According to Lu et al. intra-articular injection of chitosan increases
the chondrocyte proliferation and maintains the cartilage thickness [215].
Chitosan-coated surfaces have been used for the expansion of human os-
teoblasts and chondrocytes [212]. Results from these studies have shown that
a chitosan-coated surface promotes good cell viability and the surface enables
the cells to retain their characteristic morphology similar to that observed in
vivo. Additionally, osteoblasts expanded on chitosan film expressed signifi-
cant collagen type I gene markers whereas chondrocytes expressed collagen
type II and aggrecan. Matthew and coworkers have extensively studied the
effect of CS-chitosan composite on chondrocyte phenotype and their obser-
vations substantiate the earlier described findings [213].
Hoemann et al. have investigated the potential of using injectable chitosan-
based hydrogels for tissue engineering cartilage both in vivo and in vitro [216].
Buschmann and coworkers have developed a chitosan/blood-clot compos-
ite scaffold (commercially known as CarGel) for cartilage regeneration and
has just finished pre-clinical trials [217]. In addition to their potential for
chondrogenesis, chitosan hydrogels have also been investigated for bone re-
generation [212, 218]. Muzzarelli et al. has successfully created mineralized
bone-like tissues in osseous defects in rats, sheep, and dogs with the aid
of chitosan-based scaffolds [218]. Chitosan has also been explored as a bio-
