Biomedical Engineering Reference
In-Depth Information
HO
targets such as proteins, DNA and lipids [318] It may not be due to
scavenging of the O
2
-
by chitosan as this radical does not react with car-
bohydrates. Any observations of apparent reaction with O
2
-
are due to
the well-documented ability of chitosans to chelate metal ions, especially
Fe
3+
, which at er reduction, reacts with H
2
O
2
derived from the dismuta-
tion of the O
2
-
or from other sources (Fenton reaction) [319]. Antioxidant
activity in cellular system may be mediated by other activities of chitosan
and derivatives like inhibition of myeloperoxidase activity [300], induction
of intracellular glutathione [273, 274] and protective ef ects on oxidative
damage of DNA [320].
6.11 Conclusion
h e cationic and polymeric nature of chitosan molecule bestows it a novel
set of biological properties apart from being the biodegradable, nontoxic,
biocompatible. It is marketed as a food additive or as a dietary supple-
ment. Playing on the health card, chitosan is commercially projected as
weight lowering agent however high quality clinical trials do not sub-
stantiate this claim dei nitely. Noteworthy number of reports related to
its variety of other biological activities is available. h e most important
of the array of biological activities are the antimicrobial, hemostatic and
wound healing actions which have already been commercialized to some
extent. h e immunological and antioxidant activities of chitosan are par-
ticularly interesting and contribute to potentially very important applica-
tions of this polymer in the treatment of various tumoral al ictions and
in the treatment of several pathologies of viral origin. h e immunoadju-
vant properties of chitosan are keenly observed for their possible use in
vaccination. Since the chitosan can be degraded in living cell media, the
question remains whether the biological activities are due to the monomer
and oligomer or directly due to the polymer. h ere is need to understand
the mechanisms underlying these activities and to exploit the actions by
chemical derivitization. Chitosan-based oligomers and derivatives may
assume signii cant biological role. h e role of chitosan as a constituent of
the composites for dif erent biomedical applications based on its bioactivi-
ties and physicochemical properties has not been addressed here. Taken
that into account along with this overview, it can safely be said that, in
the near future, biomedical products based on chitin and chitosan will be
embarking on a commercialization program.
