Bioactivities of Chitosan and Its Derivatives - Chitosan Based Hydrogels: Functions and Applications - page 124

Figure 3.2
Scanning electron micrographs of platelets and erythrocytes on chitosan microsphere surfaces. (a) Platelets
with pseudopodia and (b) erythrocyte aggregation.

time [86]. The clotting time for chitosan microspheres was 30 min compared to 50 min for
the control, indicating that chitosan microspheres can induce blood coagulation.
The morphology of aggregated platelets in each microsphere was investigated using
scanning electron microscopy (SEM) (Figure 3.2a). Platelets adhered strongly on the sur-
face with pseudopodia. Furthermore, platelets were bound to each other and formed the
aggregated mass. Erythrocytes considerably adhered on the surface of chitosan micro-
spheres. The surface thus tended to enhance erythrocyte agglutination or agglomeration
(Figure 3.2b). Table 3.1 shows the results obtained for hemolysis of rabbit blood with chito-
san microspheres. It was observed that hemolysis was less than 5% at the concentration of
1 mg/mL chitosan microspheres, which was well within the permissible limit. When the
concentration of microspheres changed to 100 mg/mL, chitosan showed a little hemolysis,
with the value 7.99%.
To examine the specific interactions of protein with microspheres, adsorption for
plasma was studied using SDS-PAGE. Figure 3.3 shows gels of proteins adsorbed to
microspheres from 4% plasma. It can be seen that by comparing the microsphere gels
(lane 3) to the gel of the plasma (lane 2), the surface of chitosan microspheres bound a
large amount of plasma proteins, a fact that may explain the observed coagulation
behavior of chitosan microspheres.
When blood is in contact with a foreign material surface, adsorption of plasma pro-
teins occurs first, followed by platelet adhesion and deformation. These platelets release
substrates that start the coagulation process, resulting in thrombosis. Blood compatibility

TAble 3.1
Hemolytic Activity of Chitosan Microspheres with Different Concentration

Sample optical Density at 545 nm Hemolysis (%)

Distilled water 0.866 ± 0.041 +ve control

Normal saline 0.035 ± 0.010 −ve contol

Chitosan microspheres (500 mg/mL) 0.103 ± 0.020 7.99%

Chitosan microspheres (500 mg/mL) 0.044 ± 0.009 1.20%