Beta-sheet content significantly correlates with the biodegradation time of silk fibroin hydrogels showing a wide range of compressive modulus

Abstract Elasticity and biodegradability are required for hydrogel scaffolds in soft tissue engineering and vary among target tissues. To identify the unique effects of these properties on tissue regeneration, a factor that alters only one of these properties independent of the other is needed. Here, we evaluated various properties of 15 types of silk fibroin (SF) physical hydrogels with different SF concentrations and molecular weights, and found that the compressive modulus and biodegradability did not correlate with each other significantly. This suggested the possibility of a factor that affected only one of the properties. SF concentration and water content of the hydrogels changed both the compressive modulus and biodegradability simultaneously. In contrast, the β-sheet content in SF hydrogels correlated only with the biodegradation time significantly, suggesting that the β-sheet content may be used to study the effect of biodegradation time on tissue regeneration. In addition, an SF hydrogel was modified with a peptide derived from the β-sheet forming GAGAGS/Y repeated region in SF heavy-chain, resulting in no significant difference in the compressive modulus but a significantly delayed biodegradation time. These results suggest the potential for SF hydrogels as a group of materials with made-to-order elasticity and biodegradability for soft tissue engineering applications.