Rheological characterisation of thermogelling chitosan/glycerol-phosphate solutions

In this study we demonstrate that chitosan solutions can be neutralised up to physiological pH (similar to7.2) using beta -glycerol phosphate without creating immediate gel-like precipitation and furthermore that subsequent h eating of these solutions induces hydrogel formation. The addition of the p articular basic salt, glycerol phosphate, provides the correct buffering an d other physicochemical conditions including control of hydrophobic interac tions and hydrogen bonding which are necessary to retain chitosan in soluti on at neutral pH near 4 degreesC and Furthermore to allow gel formation upo n heating to 37 degreesC. Rheological investigation evidenced the endotherm ic gelation of chitosan/beta -glycerol phosphate solutions and allowed the establishment of a sol/gel diagram. The gelation process appears to be gove rned by delicate interplay between the pH and the temperature. The role of beta -glycerol phosphate is discussed in the light of relevant literature p articularly those indicating the role of glycerol and polyols in the stabil isation of proteins and polysaccharides. (C) 2001 Elsevier Science Ltd. All rights reserved.