Biological Evaluation of Silk Fibroin – Based Three Dimensional Nanofibrous Scaffolds for Bone Regeneration

Abstract

As the importance of developing biomaterials has grown, many studies using silk based scaffolds have been performed in the tissue regeneration field because silk has significant biocompatibility. However, although electrospining has a strong advantage as it enables biomaterials to have many micropores, electrospun silk fibroin scaffolds have not been extensively investigated. In this study, we developed three-dimensional (3D) electrospun silk fibroin scaffolds (ESFS) with controllable pore sizes. ESFSs were evaluated in vitro and in vivo by comparing with a commercially available sponge type 3D polylactic acid (PLA) scaffold for bone regeneration. Seven weeks after implantation, micro-computed tomography revealed that 78.30% of the original bone volume was attained in the ESFS with medium size pores (M-ESFS) implantation group. Comparatively, the PLA implantation group showed only 49.31%. Also, the biodegradation rates of ESFS were studied in calvaria or subcutaneous tissue of rats. Biodegradation is a very important element for regeneration of tissue because the remaining biomaterials cause chronic imflammation at the implanted site and interrupt the complete regeneration process. Implanted ESFSs were traced for 6 months and the remaining scaffold volumes were measured using image analysis at 2, 4, and 6 months after implantation. ESFSs in vivo were degraded above of 50% within 2 months after implantation. ESFSs were degraded more faster in subcutaneous tissue than in calvaria, and with 300 ~ 500 μm porous than with 100 ~ 200 μm if the size of implanted ESFSs were the same originally. In addiaion, we made ESFS containing hydroxyapatite manoparticles (ESFS-HNPs) as a bio-functional scaffold for bone regeneration. ESFS-HNPs, containing 2 or 5 % of HNPs in SF fiber, were implanted in a bone defected model of rats and the effects for bone regeneration were evaluated. Unfortunately, however, no significant difference was observed among ESFS and ESFS-HNPs 12 weeks after implantation, although the adhesion and mineralization ability of the cells were increased on ESFS-HNPs than those on ESFS. As results of this study, we assured that ESFS promote regeneration of defected tissue, progress the development of silk based biomaterials, and can be applied reliably in clinical field.