Biology Reference
In-Depth Information
et al., 2002
), chitin gels prepared by selective N-acetylation of chitosan
amine groups (
Hirano, Ohe, & Ono, 1976
) are known to be mechanically
strong (
Vachoud & Domard, 2001
), suggesting that they may be able to
overcome the insufficient strength described for chitosan-based NGCs.
Chitosan hydrogel tubes have been fabricated from chitosan solution using
acylation chemistry and mold-casting techniques followed by alkaline
hydrolysis that results in chitosan tube formation, with the extent of hydro-
lysis controlling the resulting amine content (
Freier, Montenegro, et al.,
2005
). Chitosan tubes resulted to be mechanically stronger to support
adhesion and differentiation of primary chick dorsal root ganglion neurons
and to significantly enhance neurite outgrowth (
Freier, Montenegro,
et al., 2005
).
Also, the DD affects chitosan mechanical properties, and it has been
shown that the swelling index of chitosan films decreases and the elastic
modulus and tensile strength increase with the increase in DD (
Wenling
et al., 2005
).
Finally, Wang et al. showed that a bilayered chitosan mesh tube, with an
inner layer of oriented nanofibers and an outer layer of random nanofibers,
increased the resistance to the compression force compared with the random
fiber mesh tubes (
Wang, Itoh, Matsuda, Ichinose, 2008; Wang et al., 2008
).
2.1.2 Porosity
Porosity of
a regenerative scaffold is an important factor in tissue engineer-
ing. Huang et al. described an easy method for the production of longitu-
dinally oriented channels made of chitosan by using a lyophilizing and
wire-heating process. Ni-Cu wires were used as a mandrel because of their
high level of resistance (
Huang, Huang, Huang, & Liu, 2005
). In compar-
ison with poly-lactic-
co
-glycolic acid (PLGA), the permeability and porous
structure of chitosan improved its effectiveness for the nerve tissue engineer-
ing (
Huang, Onyeri, Siewe, Moshfeghian, &Madihally, 2005
). The employ
of a weak base, to neutralize chitosan, can be used to influence the porous
structure, making it more uniform (
Huang, Onyeri, et al., 2005
). Porosity
geometry can also be controlled by a production method based on inverted
colloid crystals (
Kuo & Lin, 2013
).
2.1.3 Chitosan biodegradability
Concerning biodegradability, chitin and chitosan are degraded
in vivo
by
proteases present in all mammal tissues, such as lysozyme, papain, and pepsin,
leading to the release of nontoxic oligosaccharides of variable length which
