Porous hydroxyapatite-chitosan scaffolds for tissue engineering: experimental characterization and molecular dynamics simulation

In recent years, hydroxyapatite (HA) scaffolds have been widely used in bone tissue engineering as a result of their superior properties. However, the compressive strength and toughness of HA was low. In this study, natural chitosan (CS) binder was extracted from honey bees and HA was extracted from cortical bovine bone. CS and HA were mixed with different ratios; 1/6, 1/8, and 1/10. After sintering and removing CS, porous HA scaffolds were synthesized with different porosities, and their biocompatibility and mechanical properties were evaluated. The samples were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), and atomic force microscopy (AFM). SEM results revealed that the pores are worm-shaped in all three samples. Furthermore, the porosities and roughness of CS/HA:1/6 were higher than the other two samples. However, the toughness and compressive strength of this sample were lower than other samples. The bioactivity of the scaffolds was evaluated by immersion in a simulated body fluid (SBF) at 37 °C for 28 days. Biocompatibility of the samples was performed by cell culture with human osteoblast cells for 7 days. The results showed that more porosity leads to higher biocompatibility, although the mechanical properties decreased with increasing porosity. Furthermore, the structural and physical properties of HA-CS simulated by molecular dynamics simulation (MD). The simulated HA-CS revealed that the simulated glass transition temperature (T_g) is reliable and well consistent with the experiment values. Experimental and simulated studies revealed that CS/HA:1/10 is a promising combination for tissue engineering applications.