Preparation and characterization of PEG-cross-linked chitosan hydrogel films with controllable swelling and enzymatic degradation behavior

The PEG-cross-linked chitosan hydrogel films with different content and molecular weight of PEG were prepared. The formation of the PEG-cross-linked structure was confirmed by FT-IR measurement. The swelling ratio increases with the decrease of pH value of the surrounding buffer solution and molecular weight of PEG with the same content sample. The reversible temperature dependence was observed for swelling behavior of the PEG-cross-linked chitosan hydrogel films. The degradation rate of chitosan component by lysozyme was found to be influenced by the content and molecular weight of PEG. An increase in total PEG content resulted in a considerable increase of the degradation rate, that is, the weight loss of the sample including 45% PEG was amount to more than 15% after 24 days degradation, and lowering the molecular weight of PEG led to the fast degradation. From the SEM observation of the film surface, it was confirmed that the PEG-cross-linked chitosan hydrogel film was degraded by lysozyme from its surface to internal area.