Fabrication of 3D-printed hydroxyapatite using freeze-drying method for bone regeneration: RVE and finite element simulation analysis

Abstract

Tissue engineering is an interdisciplinary approach that utilizes cells, scaffolds, and biofactors to develop biosynthetic bone scaffolds for bone regeneration applications. These scaffolds are three-dimensional porous structures with specific mechanical and biological properties that facilitate the attachment and proliferation of osteoinductive cells on their surfaces. In this study, bone scaffolds were 3D-printed using PLA material, and a variety of three-dimensional porous structures, including Kelvin, Octet truss, and Gibson Ashby, were employed. To improve the biological properties of the scaffolds, they were coated with alginate/hydroxyapatite using the Freeze-drying method. The Alginate/HA RVEs were analyzed under periodic boundary conditions, and the elastic modulus was found to improve from 100 MPa (pure alginate) to 149 MPa by adding 30 wt% HA particles. The mechanical properties of the scaffolds were investigated under compressive deformation using experiments and finite element simulations. The results show that the compressive strength of structures follows the order σOctettruss > σGibsonashby > σKelvin. The Freeze-drying process causes pore formation on the scaffold surface. According to the microstructural analysis, the pore size was observed for composite scaffolds approximately at 320–340 μm. After 21-day, most parts of the scaffold surface were coated by the apatite layer completely, and the surface of the pores was blocked by the apatite layer. To characterize cell viability, an MTT assay was used. The scaffolds expose high cell viability around 97% and did not show any significant toxicity.

Keywords

• Hydroxyapatite
• Alginate
• 3D printing
• RVE simulation
• Bone regeneration
• Gibson Ashby