Biomedical Engineering Reference
In-Depth Information
Figure 7.1
Dependence of the CaCl
2
-dihydrate/methanol solubility of chitin with respect to
the degree of acetylation and the molecular weight of chitin. Solid square, 1.2
×
104; solid
triangle, 4.0
×
104; solid circle, 1.6
×
105 (with permission from Ref. [87]).
can be monitored by FTIR spectroscopy and by the weight loss of the material,
which raised up to 40% for a complete hydrolysis. The restoration of the chitin
structure from dibutyrylchitin fi bers resulted in an increase of the degree of crys-
tallinity and in the diameter of the fi bers along with a decrease of the tensile
strength [92] .
The peculiar biochemical properties of chitins and chitosans remain unmatched
by other polysaccharides. The major areas of application include water treatment,
biomedical applications (including wound dressing and artifi cial skin), and
personal-care products. Chitin and chitosan-based materials have unique charac-
teristics in the area of tissue regeneration. Hemostasis is immediately obtained
after application of chitin-based dressings to traumatic and surgical wounds: plate-
lets are activated by chitin with redundant effects and superior performances
compared with known hemostatic materials. To promote angiogenesis, the pro-
duction of the vascular endothelial growth factor is upregulated in wound healing
when macrophages are activated by chitin/chitosan. Biocompatible wound dress-
ings derived from chitin are available in the form of hydrogels, xerogels, powders,
composites, fi lms, and scaffolds. The scaffolds are easily colonized by human cells
to restore tissue defects. Chitin tubes, which can be manufactured from the tendon
of the crab leg muscle or by using electrospun chitosan nonwoven, can be
implanted to bridge a dissected nerve and used as alternative to autologous grafts.
Chitosan is also used in cartilage tissue engineering where it provides an environ-
ment in which the chrondrocytes maintain their correct morphology and their
capacity to synthesize the correct extracellular matrix. Scaffolds made of either
pure
β
-chitin, or pure chitosan, or mixtures of both polysaccharides had the same
