Abstract: By two steps of reaction, a novel water-soluble chitosan derivative[N-(2-sulfobenzyl) chitosan, SBCS] was synthesized. The chemical structure of SBCS was characterized by FTIR, ¹H NMR, UV-Vis spectra. Degree of substitution(DS) of N-2-sulfobenzyl was determined by colloid titration. In the buffer solutions with different pH values the swelling characteristics of hydrogels based on SBCS(SBCSG) prepared by cross-linking with glutaraldehyde were studied. The results show that the swelling ratio(SR) of SBCSG was decreased with increasing the dosage of glutaraldehyde. The SBCSG swelled more significantly in alkaline solution than in acidic medium and showed the lowest SR at pH=5.0. In alkaline solution, the SR of SBCSG was increased with raising the DS of N-2-sulfobenzyl of SBCS, but no significant change in acidic environment. The SBCSG showed swelling reversibility when soaked in pH=1.0 and pH=7.4 buffer solutions alternately. The results imply that SBCS could be potential pH sensitive carrier for colon-specific drug delivery system.

Key words: Chitosan, Modification, pH-sensitivity, Hydrogel, Swelling ratio