Synthesis and characterization of polysialic acid/carboxymethyl chitosan hydrogel with potential for drug delivery

A novel hydrogel was prepared from polysialic acid (PSA) and carboxymethyl chitosan (CMCS) using glutaraldehyde as the cross-linking agent. The resulting PSA–CMCS hydrogel exhibited pH sensitivity, in which the swelling ratio under acidic conditions was higher than those under neutral or alkaline conditions. The swelling ratio of PSA–CMCS hydrogel at equilibrium depended on the medium pH, the cross-linking agent concentration, and the ratio of PSA to CMCS (w/w). Bovine serum albumin (BSA) and 5-fluorouracil (5-FU) were used as model drugs to prepare hydrogel delivery systems. The loading efficiencies of the hydrogel for BSA and 5-FU were 26.25 and 36.74%, respectively. Release behaviors of BSA and 5-FU were influenced by the pH. MTT assays confirmed that PSA–CMCS hydrogel has no cytotoxicity toward the NIH-3T3 cell line; in fact, the 100% aqueous extract of the PSA–CMCS hydrogel enhanced cell growth. These results suggest that PSA–CMCS hydrogel may be a promising pH-sensitive delivery system, especially for hydrophobic chemicals.