Characterization of the interaction between chitosan and inorganic sodium phosphates by means of rheological and optical microscopy studies

The physicochemical and rheological properties of chitosan and two different inorganic sodium phosphate dispersions (NaH 2PO 4 and Na 3PO 4) were investigated in order to elucidate the role of different factors, such as ratios between polymer and sodium inorganic phosphates, different pHs and storage stability, on the gelling properties of chitosan. This was deemed opportune since physico-chemical characterizations of chitosan in the literature often appear incomplete and questionable. We also compared the elastic modulus values of the different chitosan/inorganic phosphate systems and examined their behaviour through optical microscopy analyses. The most efficient formulations that showed a thermogelling capacity with a significant gel transition behaviour after 24 h were the NaH 2PO 4/chitosan and Na 3PO 4/chitosan systems at ratio 2 and pH 7.0. These results confirmed the importance of the pH value and ratio selection for the final systems.