Biomedical Engineering Reference
In-Depth Information
the ef ect of weight of chitosan molecule on blood coagulation, the review by
Whang
et al.
, mentioned that low molecular weight chitosans were unable
to initiate i rm coagulum formation [90]. h e
in vivo
studies carried out by
Hirano,
et al.
, showed that more blood coagulum is formed on suture surfaces
coated with fully deacetylated chitosan rather than on sutures impregnated
with acetylated chitosan [91]. h e recent studies by Fischer by electrophoretic
and Western blot analysis of red blood cell surface proteins demonstrated that
chitin microi bers were bound to band three of the red blood cells. However,
they stated that the interaction resulted in the activation of the intrinsic coag-
ulation cascade associated with the presentation of phosphatidylserine on the
outer layer of the surface membrane of nanoi ber-bound red blood cells. h e
results demonstrated that red blood cells play a direct and important role in
achieving surface hemostasis by accelerating the generation of thrombin [92].
Chitosan also mediates platelet aggregation [93]. Study of the mecha-
nism for this phenomenon by Chou,
et al.
, demonstrated that chitosan is
an ef ective inducer of rabbit platelet adhesion and aggregation [88].
h e
potent platelet aggregation induced by chitosan was proportional to the
concentration of platelets in the plasma [94].
h e relationship was investigated by Fischer,
et al.
, between confor-
mation of chitins and activation of hemostasis, including SyvekPatch ,
whose chitin i bers are organised in a parallel tertiary structure that can
be chemically modii ed to an antiparallel one; and hydrogels consisting
of either partially or fully deacetylated daughter chitosans [106]. Several
studies were performed on the said chitosans, including, (1) an analysis
of the ability of chitosans to activate platelets and turnover of the intrinsic
coagulation cascade, (2) an examination of the viscoelastic properties of
mixtures of platelet-rich plasma and chitosans via thrombo-elastography
and (3) scanning electron microscopy to examine the morphology of the
chitosans. h e haemostatic responses to the chitosans were highly depen-
dent on their chemical nature and tertiary/quaternary structure, while the
microalgal chitin i bers were found to have superior hemostatic activity
compared to the other chitosans.
h e action of chitosan on blood could be modulated by formation of its
sulfate esters which chemically behave as heparin-like substances.
6.6
Chitosan as Immunity Modulator
h e immunological activity of chitosan is particularly interesting and con-
tributes to potentially very important applications of this polymer in the
treatment of various tumoral al ictions and in the treatment of several
