Fibroblast interaction with carboxymethylchitosan-based hydrogels

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.     

In vitro comparative hemostatic studies of chitin,chitosan, and their derivatives

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 chitosan (PNAC), N,O‐carboxymethylchitosan (NOCC), N‐sulfated chitosan, N‐(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 SPONGOSTAN® standard were significantly decreased with respect to that of the pure whole blood (a blank control) (P < 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. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 445–451, 2006     

Phase evolution and electrical properties of lead zirconate titanate thin films grown by using a triol sol–gel route

Lead zirconate titanate (PZT) precursor sols were prepared using a triol based sol–gel route. Inorganics salts metal alkoxides lead acetate trihydrate [Pb(OOCCH₃)₂·3H₂O], titanium (IV) isopropoxide [Ti(OCH(CH₃)₂)₄], and zirconium n-propoxide [ZrOC₃H7)₄] were used as starting materials. Thin films were deposited by spin coating onto Pt/Ti/SiO₂/Si substrates. The samples were pre-heated (pyrolysis) on a calibrated hotplate over the temperature range of 200–400 °C for 10 min then firing at a temperature of 600 °C for 30 min. Randomly-oriented PZT thin films pre-heated at 400 °C for 10 min and annealed at 600 °C for 30 min showed well-defined ferroelectric hysteresis loops with a remanent polarization of 27 μC/cm² and a coercive field of 115 kV/cm. The dielectric constant and dielectric loss of the PZT films were 621 and 0.040, respectively. The microstructures of the thin films are dense, crack-free and homogeneous with fine grains about 15–20 nm in size.     

New route to the preparation of carboxymethylchitosan hydrogels

A new method to prepare CM–chitosan hydrogels was introduced with the use of steam. The procedure was simple and economical, with no toxic chemicals involved. The steam‐induced crosslinking of CM–chitosan sodium salt involved the –NH₂ and –COONa groups, forming amide linkages (–CONH–), evidently supported by FTIR spectroscopy and other techniques. The hydrogels instantly imbibed a great deal of water. The degree of swelling (DS) of the hydrogels was found to be up to 36, depending on the harshness of steaming conditions used. Likewise, the coloration of the samples increased from light beige to brown with increasing temperature and duration of steam exposure. The overall efficiency of the steam method for the crosslinking of CM–chitosan sodium salt was quite high. The percentage weight loss was found to be less than 10 to obtain hydrogels with DS values around 20. No weight loss in the dry weight of the fractionated hydrogels was observed when the samples were steamed at 115°C or higher for 15 min or longer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4016–4020, 2003