[Effect of deacetylation degree of chitosan on thermosensitive hydrogel via rheological characterization]

To evaluate the effect of deacetylation degree (DDA) on the gelation behavior of thermosensitive chitosan-beta glycerol phosphate disodium salt pentahydrate (CH-GP) system and to compare their rheological behaviors before and after gelation.

A series of thermosensitive CH-GP samples with different DDAs (70%, 85%, 90%, 97%) were prepared by dissolving CH with 0.1 mol/L HCl solution, 5 samples for every single DDA, and then all these CH-GP solution samples processed the frequency sweep test and temperature sweep test (10-70 degrees C, 1 degrees C/min) on AR 2000ex rheometer, with pH value of 7.02. Also, all the results of hydrogel samples were processed a frequency sweep test.

With CH concentration of 2% (w/v) and pH value of 7.02 , the gelatin temperature of CH-GP systems with different DDAs (85%, 90%, 97%) were (59.90 +/- 0.08), (48.10 +/- 0.08), (37.10 +/- 0.11) degrees C, respectively. While the gelatin temperature of CH-GP system with 70% DDA was over 70 degrees C. There were statistically significant differences in temperature and time of gelation among groups with different DDAs (P < 0.05). Furthermore, storage modulus of such system raised from dozens Pa to a magnitude of several kPa during gelation, while loss modulus kept almost steady.

Gelatin temperature and mechanical property of the system could be measured objectively by rheological characterization. Thus during designing tissue engineered scaffolds for various purposes, it is helpful applying selected CH with optimal DDA to different target tissues.