Biomedical Engineering Reference
In-Depth Information
Figure 3.4
(a) Effect of the proportion and type of PP in chitosan on blood clotting rates, as measured by absorbance of
hemoglobin from lyzed uncoagulated RBCs. *
p
< 0.05 compared to chitosan, analyzed by one-way ANOVA with
the post-hoc Scheffe test,
n
= 4. (b) Photograph showing more rapid clot formation on chitosan-10% PP com-
pared to chitosan. (From Park, C. J. et al. 2009.
Acta Biomater
5: 1926-1936. With permission.)
4.2 mM HCO
3
−
, 1.0 mM HPO
4
2−
, and 5.0 mM SO
4
2−
, and was buffered at pH 7.4 with
tris(hydroxymethyl)aminomethane and 1 M hydrochloric acid at 37°C. Weighed dry dress-
ings (
Wini
) were placed in tissue culture plate wells containing 1.5 mL of SBF or citrated
whole blood. Plates were sealed and incubated in a humidified chamber at 37°C. At the
end of 2 h, the dressings were removed, placed on absorbent paper towel for 3 s to remove
surface water and freely draining liquid, and weighed to determine wet weight (
Wwet
).
Fluid uptake (g/g) was calculated as (
Wwet
−
Win
)/
Wini
.
3.2.2.2 Hemostatic Potential of Chitosan and Its Derivatives
Hemorrhage remains a leading cause of early death after trauma, and infectious compli-
cations in combat wounds continue to challenge caregivers. Chitosan and its derivatives
were developed to address these problems, chitosan containing different amounts and
types of polyphosphate polymers was fabricated, and their hemostatic efficacies were
evaluated
in vitro
.
Figure 3.4a shows the effect of the proportion and type of PP in chitosan on blood
clotting rates, as measured by absorbance of hemoglobin from lyzed uncoagulated
blood. A higher absorbance value of the hemoglobin solution thus indicates a slower
clotting rate. Chitosan with 6.7% w/w or 10% w/w PP65 or PP45 led to significantly
lower absorbance values than chitosan (Figure 3.4a). The clots formed on chitosan-10%
PP45 were also visibly larger than those on chitosan at 10 min (Figure 3.4b). Blood clot-
ting rates on gauze were significantly slower than on chitosan (
p
< 0.05), while the
absorbance value of no-sample controls was significantly higher than that of chitosan-
based materials (
p
< 0.001) but not gauze (
p
= 0.362). This indicates that gauze was not
able to cause significant blood clotting within 10 min. Significantly more platelets
adhered on chitosan-10% PP45 (
p
< 0.01) and chitosan-10% PP65 (
p
< 0.05) than on chi-
tosan
(Figure 3.5a),
while significantly fewer platelets adhered on gauze than on chito-
s a n (
p
< 0.001). More platelets were also observed on chitosan-10% PP45 than on chitosan
under SEM (Figures 3.5c and f). In addition, larger platelet aggregates and more exten-
sive platelet pseudopod formation can be observed on chitosan-10% PP45 compared to
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