Conjugation of CMCS to silk fibroin for tuning mechanical and swelling behaviors of fibroin hydrogels

Silk fibroin (SF) attracts great scientific interests as multifunctional biomaterials, owing to its excellent biocompatibility. However, a critical issue with regard to pure SF hydrogels is its poor formability. To address this issue, a composite hydrogel of SF and carboxymethyl chitosan (CMCS) was prepared, via EGDE-assisted conjugation of CMCS to SF chains for tuning the mechanical property and drug-release behavior. The results reveals that molecular weight of SF was noticeably increased after grafting of CMCS, meanwhile, the obtained hydrogel exhibited high structural stability and improved mechanical properties compared to the control. In the range of compression ratio of 10 to 50%, the composite hydrogel exhibited satisfactory elastic recovery effects, meanwhile, increasing CMCS contents was beneficial enhance its water retention ability. Using Trypan blue as the model drug, the sustained release rate of the SF/CMCS hydrogel was approximately 35% higher than that of the SF hydrogel. Moreover, the introduction of CMCS into SF hydrogel also promoted the proliferation of NIH/3T3 cells, revealing excellent biocompatibility of the prepared hydrogel. In summary, an efficient and novel strategy to prepare fibroin hydrogels with desired properties is developed, which might expand the applications of SF in the field of biomedical materials.