Hydrogel drug delivery systems based on chitosan/polyol salt combinations were prepared with cylindrical and spherical shapes, and their thermo-/pH-sensitivities were investigated.The systems could be held liquid below room temperature and they formed monolithic gels at body temperature.The higher the gelling temperature was, the higher the strength of hydrogels.VB12 was taken as the model drug and the release characteristics of the prepared system were studied at various pH environments.Under pH 4.0 condition,about 65% of the drug was released within 70 min;while under pH 7.4 condition,about 57% released within the same time.Release experiments on hydrogels with modified chitosan were performed.Under pH 4.0 condition, the hydrogel system released 42% within 70 min;while under pH 7.4 condition, it only released 37% within the same time.By modifying the chitosan,the rate of release was decreased while the thermo /pH sensitivities were retained in a certain extent.Distinct differences of microstructures of hydrogels were found both after release experiments in different pH conditions and after biodegradation.
