Biology Reference
In-Depth Information
manner or fail to regenerate spontaneously after SCI. When nervous tissue
loss occurs, different methods have been used to bridge the spinal cord gap.
For example, transplantation of peripheral nerves (
Bray, Villegas-Perez,
Vidal-Sanz, & Aguayo, 1987; Cheng, Cao, & Olson, 1996
), SCs (
Bunge,
2002; Novikova, Pettersson, Brohlin, Wiberg, & Novikov, 2008; Xu,
Zhang, Li, Aebischer, & Bunge, 1999
), olfactory ensheathing cells
(
Li, Field, & Raisman, 1997; Ramon-Cueto, Plant, Avila, & Bunge,
1998
), and NSCs has been used (
Teng et al., 2002; Xue et al., 2012;
Zheng & Cui, 2012
). These studies have shown that CNS axons can regen-
erate in an appropriate microenvironment and injured axons can recover
part of their function. However, the above-mentioned methods have lim-
itations for clinical applications, such as damage to the donors of peripheral
nerves and immunological rejection.
Biomaterials are becoming increasingly popular as a potential tool for the
treatment of SCI as a mean to restore the ECM at the site of injury. Various
materials, both of natural and synthetic origin, have been investigated for
potential applications in the spinal cord (
Nomura, Tator, & Shoichet,
2006; Novikova et al., 2003; Samadikuchaksaraei, 2007; Straley, Foo, &
Heilshorn, 2010
). These materials can support endogenous tissue regener-
ation (
Tysseling-Mattiace et al., 2008; Woerly, Pinet, de Robertis, Van
Diep, & Bousmina, 2001
), promote directed axonal regrowth (
Li and
Hoffman-Kim, 2008; Yoshii, Ito, Shima, Taniguchi, & Akagi, 2009
),
enhance cell transplant survival and integration (
Itosaka et al., 2009; Teng
et al., 2002
), deliver drugs (
Johnson, Parker, & Sakiyama-Elbert, 2009;
Kang, Poon, Tator, & Shoichet, 2009; Willerth & Sakiyama-Elbert,
2007
), and seal damaged
dura mater
(
Gazzeri et al., 2009
). Biomaterials
designed for spinal cord repair should provoke minimal chronic inflamma-
tion and immune responses when implanted into the body (
Anderson,
Rodriguez, & Chang, 2008; Williams, 2008
). These responses depend
not only on the intrinsic properties of the material itself but also on the form
in which the material is presented, for example, implant shape (
Di Vita et al.,
2008
), size (
Kohane et al., 2006
), and porosity (
Ghanaati et al., 2010
). In
particular, it is important to monitor over time degradation kinetics and sec-
ondary product formation of biomaterials because degradation products can
elicit inflammatory responses that may be different than those elicited by the
implanted material. Regarding degradation kinetics, chitosan is an attractive
material because of its degradation rate that can be regulated by acting on its
DD. Fully deacetylated (DD
100%) chitosan is nondegradable (
Freier,
Koh, et al., 2005; Tomihata & Ikada, 1997
), whereas partially deacetylated
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