ABSTRACT:The effects of chitin, chitosan, and their derivatives on in vitro human blood coagulation and platelet activation were comparatively studied. The coagulation was assessed by the measure of the whole blood clotting time (WHBCT) and plasma recalcification time (PRT). The tested materials were chitin, chitosan, partially N-acetylated chi- -(2-hydroxy)propyl-3-trimethylammonium chitosan chloride, and SPONGOSTAN ® standard (a positive control). The results revealed that the WHBCTs of whole blood mixed with chitin, chitosan, NOCC, or SPON-GOSTAN ® standard were significantly decreased with respect to that of the pure whole blood (a blank control) (P Ͻ 0.05), while the WHBCT value of whole blood mixed with PNAC was not significantly reduced. However, the presence of PNAC significantly lowered the PRT value, similar to the addition of chitin, NOCC, or SPONGOSTAN ® standard. Chitosan was found to reduce PRT, but not significantly. In the platelet adhesion and activation studies, the morphology of platelets adherent to the film surfaces of tested materials was examined using a scanning electron microscopic technique. Because of their effective coagulation activites, chitosan, PNAC, and NOCC were further evaluated to determine how platelets behaved when in contact with these film samples for given periods. It was found that NOCC activated platelets most effectively.

The genus Tylopus currently contains 41 species, all keyed and mapped, including five new from northern Thailand: Tylopus bispinosus sp. n., Tylopus grandis sp. n., Tylopus extremus sp. n., Tylopus veliger sp. n. and Tylopus parajeekeli sp. n. Species of Tylopus are predominantly forest-dwellers, especially in montane habitats where up to 9–10 species can coexist per faunule. We expect many more congeners to be discovered in future, in particular from poorly or relatively poorly prospected regions such as Laos (only two species recorded), Cambodia (no species yet), Vietnam (a few species), Myanmar (a few species) and southern China (one species only). Because the genus is so species-rich and as yet so poorly sampled, a phylogenetic analysis of Tylopus would be premature.

The interaction between L929 cells and carboxymethylchitosan (CM-chitosan)-based hydrogels, hydrogels from pure CM-chitosan and its blends, was examined in this study. Cytotoxicity of all materials was also assessed. The cellular morphology and behavior on the surfaces of the hydrogels were observed by scanning electron microscopy (SEM). The effects of various parameters, e.g., type and content of blended polymers, surface structure of hydrogels, and steaming condition used for the preparation of the hydrogels, on the cell-material response were investigated. The results of the cytotoxicity test revealed that all hydrogels were non-cytotoxic. The SEM micrographs demonstrated that the cells proliferated and spread onto a porous CM-chitosan sample. Better cell spreading was found on a flat surface of a CM-chitosan film. Rounded cells were observed when poly(vinyl alcohol) (PVA) was incorporated into CM-chitosan. Fewer cells were found when the content of PVA increased. Spherical clusters of the aggregated cells existed in the blends with ultra high viscosity carboxymethylcellulose (CM-cellulose). In contrast, with the use of low viscosity CM-cellulose, the cells appeared more spreading. The attached cells on the CM-chitosan film steamed at the highest temperature and longest period appeared to spread the most among all tested steaming conditions.