Radiation synthesis and characteristic of the hydrogels based on carboxymethylated chitin derivatives

Carboxymethylchitin (CM-chitin) and its deacetylated product carboxymethylchitosan (CM-chitosan) were irradiated in aqueous solutions at various irradiation dose by high-energy radiation electronic accelerator in vacuum. Carboxymethylated chitin derivatives irradiated at paste-like conditions were found to introduce crosslinking structure. When the dosage of electron beam irradiation was 20 kGy or more, transparent hydrogels could be produced. In the case of CM-chitosan, high degree of deacetylation was found to negatively correlate to crosslinking even if it has a high degree of substitution. The hydrogels created from carboxymethylated chitin derivatives, exhibited excellent mechanical properties and good swelling in water. The further study on the swelling properties at various conditions indicated that CM-chitin and CM-chitosan hydrogels displayed characteristically pH-sensitive character in their swelling behavior. The gel of CM-chitosan with a high DS (0.91) swelled in acid (pH<3.5) and alkaline (pH>6) conditions and deswelled between pH 3.5 and 6.0 due to the ionic composition changes of the gel network. In addition, the antibacterial activity against E. coli was also found in CM-chitosan hydrogel.