Effects of two sterilization methods on the thermo-gelation behavior and in vitro protein release characteristics of chitosan hydrogel

Objective To compare the effects of two different sterilization methods on the thermo-gelation behavior and protein release characteristics of chitosan hydrogel in vitro. Methods Chitosan thermo-sensitive hydrogel was routinely fabricated and sterilized by two methods: (1) conventional group: steam sterilization on chitosan solution; (2) modified group: steam sterilization on chitosan powder. Gelation time was recorded and the viscosity was measured using a viscometer. The topography and the cross section of the chitosan hydrogel were observed by a scanning electron microscopy (SEM) . Fourier transform infrared (FTIR) spectra were obtained with a Fourier Transform IR Spectrophotometer. In vitro protein release characteristics were observed using bovine serum albumin (BSA) as a model protein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to determine the structural integrity of model protein. Results At 37℃, the gelation time of modified group was significantly longer than that of conventional group (t=61.677, P= 0.000) . The viscosity of modified group was 15000 mPa.s at 37℃, while the viscosity of conventional group was 1560 mPa.s at 37℃ and increased to 11 500 mPa.s at 40℃. SEM observation showed three-dimensional mesh porous structures in both groups. Mean pore size of conventional group was larger than those of modified group. Both groups presented great controlled-release of the model protein, modified group was better than conventional group (t= 61.415, P= 0.000) . There is no significant difference on the FTIR spectra of the two sterilized groups. The result of SDS-PAGE indicated that the protein released from both groups remained structural integrity. Conclusions Autoclaving chitosan powder had shorter gelation time, better thermo-gelation behavior and could prolong the release of model protein in vitro than autoclaving chitosan/β-GP solution. Key words: Chitosan; Thermo-sensitive hydrogel; Sterilization methods; Protein release