Biocompatiable silk fibroin/carboxymethyl chitosan/strontium substituted hydroxyapatite/cellulose nanocrystal composite scaffolds for bone tissue engineering.

Bone defects arise from trauma, skeletal diseases or tumor resections have become a critical clinical challenge. Biocomposite materials as artificial bone repair materials provide a promising approach for bone regeneration. In this study, we used silk fibroin (SF), carboxymethyl chitosan (CMCS), cellulose nanocrystals (CNCs) and strontium substituted hydroxyapatite (Sr-HAp) to prepare the biocomposite scaffolds of SF/CMCS, SF/CMCS/CNCs, SF/CMCS/CNCs/Sr-HAp. The characterization results showed that all the SF-based scaffolds have a porous sponge-like structure with porosities over 80%. In addition, there was a significant increase in compressive strength of SF/CMCS/Sr-HAp/CNCs scaffold when compared to that of SF/CMCS scaffolds, while maintaining high porosity with lower swelling ratio. All the SF-based scaffolds were non-toxic and had a good hemocompatibility. Comparing to the SF/CMCS scaffold, the scaffolds with addition of Sr-HAp and/or CNCs showed enhanced protein adsorption and ALP activity. In addition, higher expression of osteogenic gene markers such as RUNX2, ALP, OCN, OPN, BSP and COL-1 further substantiated the applicability of SF/CMCS/Sr-HAp/CNCs scaffolds for bone related applications. Hence, this study suggests that SF/CMCS/Sr-HAp/CNCs scaffolds have a potential in non-loading bone repair application.