Synthesis of and in vitro and in vivo evaluation of a novel TGF-1-SF-CS three-dimensional scaffold for bone tissue engineering

The role of transforming growth factor-1 (TGF-1) in normal human fracture healing has been previously demonstrated. The objective of the present study was to examine the biocompatibility of TGF-1-silk fibroin-chitosan (TGF-1-SF-CS) three-dimensional (3D) scaffolds in order to construct an ideal scaffold for bone tissue engineering. We added TGF-1 directly to the SF-CS scaffold to construct a 3D scaffold for the first time, to the best of our knowledge, and performed evaluations to determine whether it may have potential applications as a growth factor delivery device. Bone marrow-derived mesenchymal stem cells (BMSCs) were seeded on the TGF-1-SF-CS scaffolds and the silk fibroin-chitosan (SF-CS) scaffolds. On the TGF-1-SF-CS and the SF-CS scaffolds, the cell adhesion rate increased in a time-dependent manner. Using a Cell Counting Kit-8 (CCK-8) assay and analyzing the alkaline phosphatase (ALP) expression proved that TGF-1 significantly enhanced the growth and proliferation of BMSCs on the SF-CS scaffolds in a time-dependent manner. To examine the in vivo biocompatibility and osteogenesis of the TGF-1-SF-CS scaffolds, the TGF-1-SF-CS scaffolds and the SF-CS scaffolds were implanted in rabbit mandibles and studied histologically and microradiographically. The 3D computed tomography (CT) scan and histological examinations of the samples showed that the TGF-1-SF-CS scaffolds exhibited good biocompatibility and extensive osteoconductivity with the host bone after 8 weeks. Moreover, the introduction of TGF-1 to the SF-CS scaffolds markedly enhanced the efficiency of new bone formation, and this was confirmed using bone mineral density (BMD) and biomechanical evaluation, particularly at 8 weeks after implantation. We demonstrated that the TGF-1-SF-CS scaffolds possessed as good biocompatibility and osteogenesis as the hybrid ones. Taken together, these findings indicate that the TGF-1-SF-CS scaffolds fulfilled the basic requirements of bone tissue engineering, and have the potential to be applied in orthopedic, reconstructive and maxillofacial surgery. Thus, TGF-1-SF-CS composite scaffolds represent a promising, novel type of scaffold for use in bone tissue engineering.