Preparation of a silk fibroin/gelatin composite hydrogel for high-selectively adsorbing bovine hemoglobin

Hydrogels are widely used in biomedical applications and separation of biomolecules. However, they either share limited biocompatibility or possess poor mechanical properties. In this study, by integrating two natural polymers of silk fibroin and gelatin into one hydrogel under the assistance of the cross-linker genipin, a silk fibroin/gelatin composite hydrogel was prepared with a high selectivity, a good biocompatibility and a porous structure. The preparation conditions were optimized as SF solution concentration of 3.5 wt%, gelatin solution concentration of 7 wt%, genipin solution concentration of 5 mg mL-1, reaction time of 1 h at 50 °C, and freeze-defrost cycle of 3. Following the entanglement of silk fibroin and gelatin, the mechanical strength of the obtained natural polymer-based hydrogel was significantly improved to around 0.8 MPa at 80% compression. The obtained hydrogel showed high adsorbing selectivity toward bovine hemoglobin (BHb) with an adsorption capacity of 724.0 mg g-1 at the BHb initial concentration of 0.5 mg mL-1, a 24.0-folder higher than that of BSA. The selectivity factor of BHb from BHb/BSA mixtures was also as high as 13.9. The adsorption isotherm and kinetics study indicated the obtained SF/G-G hydrogel possessed heterogeneous adsorption sites, the BHb adsorption process was chemisorption and diffusion-controlled, the increasing of temperature contributed to the adsorption process. The obtained hydrogel demonstrated the superiority and the valuable application prospect on selectively adsorbing BHb.