Investigation on the thermal gelation of Chitosan/β-Glycerophosphate solutions.

This work deals with the effect of temperature on the thermal-gelation process of water solutions containing chitosan β-glycerolphosphate disodium salt hydrate. In particular, the attention is focused on the role played by temperature on the gel final properties, a very important aspect in the frame of drug delivery systems. The study was performed by combining rheology and low field nuclear magnetic resonance, two approaches that revealed to be highly synergic as they can detect different aspects of the developing polymeric network. This study indicates that 30 °C represent a sort of threshold for both the gelation kinetics and the gel final properties. Indeed, above this temperature, gelation kinetics was rapid and yielded to a strong gel. On the contrary, a slow kinetics and a final weak gel occurred below 30 °C. Finally, rheology and low field NMR allowed, independently, evaluating the time evolution of the network mesh size upon gelation.