Systhesis and Characterization of Novel Carboxymethyl Chitosan Hydrogel

Novel hydrogels were prepared by crosslinking carboxymethyl chitosan(CMCS) with 1-ethyl-3-(3-dimethyl-aminopropyl)-1-carbodiimide/N-hydroxysuccinimide(EDC/NHS) as catalyst at room temperature. The amount of EDC and EDC/NHS mass ratio revealed to be influencing factors on the reaction. The hydrogels exhibited typical pH-responsive character. Solid-state13C nuclear magnetic resonance(NMR) and differential scanning calorimetry(DSC) measurements confirmed the effective crosslinking of carboxymethyl chitosan. A minimum swelling ratio is obtained at the isoelectric point in the pH range of 3—5. Degradation of hydrogels was carried out at 37 ℃ in phosphate buffered saline(PBS) or in PBS containing 0. 2 mg/mL lysozyme. The hydrogels appeared rather stable in PBS for 10 d. The initial mass loss of 15% —45% was assigned to the dissolution of uncrosslinked CMCS. The hydrogel with low crosslink density was degraded after 80 h in the presence of lysozyme,while the hydrogel with high crosslink density was hardly degraded. A model drug,bovine serum albumin(BSA) was loaded in CMCS hydrogels. Preliminary drug release studies show that the hydrogels are promising carrier of hydrophilic drugs.