In vitro and in vivo evaluations of three-dimensional hydroxyapatite/silk fibroin nanocomposite scaffolds.

In this study, three-dimensional hydroxyapatite/silk fibroin (HAp/SF) nanocomposite scaffolds were successfully prepared through layer solvent casting combined with the freeze-drying technique for tissue engineering applications. Various SF aqueous concentrations, ranging from 2.5% to 10%, were used to control the physicochemical properties of the prepared scaffolds. Biologic responses of the rat bone marrow stromal cells (rBMSCs) to the HAp/SF scaffolds were examined by culturing the cells within them. In addition, biodegradation and biocompatibility of the scaffolds were evaluated in vitro and in vivo, respectively. Among the prepared scaffolds, HAp/SF-2.5% was the most brittle sample and showed porous structure with lowest mechanical properties. The average pore diameters were 350 ± 67 and 112 ± 89 µm and decreased with the increase in the SF concentration from 5% to 10%, respectively. The pores formed in the scaffolds, made up of the 5% SF, were more uniform and regular than those of the scaffolds made up of 5% and 10% SF. The HAp/SF scaffolds did not change the rBMSCs viability and were not cytotoxic compared with the control sample. The scanning electron microscopy micrographs showed that the cells migrated into the pores and well attached to the scaffolds and their cytoplasm was extended in all directions, indicating a promising cell adhesion, high biocompatibility, and no cytotoxicity of the HAp/SF-5% nanocomposite scaffolds. Subcutaneous implantation of the HAp/SF-5% scaffolds in rat models suggested an excellent biocompatibility. All data obtained from this study suggest the potential use of the HAp/SF-5% for hard tissue engineering.