Gel–sol–gel thermo-gelation behavior study of chitosan–inorganic phosphate solutions

In present study, the feasibility of developing a novel thermo-sensitive hydrogel suitable for injectable formulations based on chitosan and inorganic phosphate was demonstrated. The physicochemical and rheological changes of chitosan/dibasic sodium phosphate solutions as in function with temperature were investigated in order to gain a better understanding of gelation process. According to the result of rheological study, there are two phase transition points as in function with temperature, corresponding to 30 degrees C and 43 degrees C. The system is gel state at approximately 4 degrees C. With the temperature increased to 30 degrees C, the gel-sol transition as well as the decrease in turbidity was observed. The sol-gel transition as well as the increase in turbidity was observed again as the temperature was above 43 degrees C. And the gel obtained at approximately 4 degrees C is reversible, but the gel obtained at approximately 43 degrees C is irreversible.