Preparation of chitosan‐based thermosensitive hydrogels for drug delivery

The thermosensitive material that could be transformed into gel at 37°C was prepared from chitosan (dissolved in acetic acid/sodium acetate buffer solution) and a mixture of α‐ and β‐glycerophosphate (αβ‐GP). The thermosensitive characteristics, appearance, and structure of the hydrogel were all affected by the pH, ionic strength, and CS/αβ‐GP ratio. The optimal conditions for the preparation of a transparent CS‐αβ‐GP thermosensitive hydrogel were pH 4.6, ionic strength 0.15 mol/L, and a CS/αβ‐GP ratio of 8.8/1.2 (v/v). The hydrogel was stable for at least 3 months at 4°C. We believe that hydrogen bonding interactions between the N H (and CO) groups of chitosan and the OH groups of αβ‐GP play an important role during the process of sol‐to‐gel transition. The cumulative release of adriamycin from the CS‐αβ‐GP hydrogel, measured in PBS at pH 7.4, reached only 60 to 70% over 24 h, indicating that this material could be potentially used in a sustained drug delivery system.