Influence of the pore size and porosity of selective laser melted Ti6Al4V ELI porous scaffold on cell proliferation, osteogenesis and bone ingrowth

Abstract

This paper systematically investigates the biomedical performance of selective laser melted (SLM) porous Ti6Al4V ELI scaffolds for bone implantation through in vitro and in vivo experiments. Scaffolds with pore sizes of 500 μm, 600 μm and 700 μm and porosities of 60% and 70% were manufactured in order to explore the optimum pore size and porosity. Rat bone marrow mesenchymal stem cells (rBMMSCs) were used in the in vitro experiments. Cell Counting Kit-8, live/dead staining and scanning electron microscope were used to assess the cytotoxicity of the porous scaffolds. DNA content quantification was performed to investigate cell proliferation on the porous scaffolds. The osteogenic differentiation of cells was measured by alkaline phosphatase (ALP) activity and osteogenic gene expressions, including bone morphogenetic protein-2 (BMP-2), collagen type 1α1 (COL-1), osteocalcin (OCN), osteopontin (OPN) and runt-related transcription factor-2 (RUNX-2). The Sprague-Dawley (SD) rat models with distal femoral condyles defect were used in the in vivo experiments. Micro-CT analysis and histological analysis were performed after implantation surgery to reveal the bone ingrowth into the porous scaffolds. All in vitro data were analyzed by one-way ANOVA followed by Tukey post hoc tests, in vivo data were analyzed using Kruskall-Wallis ANOVA and Conover-Inman post-hoc test. Based on the in vitro and in vivo experiments, it is found that the porous scaffolds manufactured by SLM did not induce a cytotoxic effect. Among all the porous scaffolds, the scaffold with a pore size of 500 μm and porosity of 60% showed the best cell proliferation and osteogenic differentiation (in vitro experiments) and bone ingrowth (in vivo experiments).

Keywords: Bone defect; Bone ingrowth; Osteogenesis; Pore size; Porosity; Ti6Al4V ELI.