In Vitro Study on the Suitable Porosity of Co–Cr Alloys Manufactured by Selective Laser Melting for Promoting Osteogenesis

In this study, we evaluated the effect of pore size with constant porosity for promoting osteogenesis in vitro. Three porous Cu-bearing Co–Cr alloys specimens (with an intended porosity of 40%, 60%, and 80%, respectively), were manufactured by selective laser melting (SLM). A diamond lattice was adapted as the basic structure. In order to systematically investigate the cell biocompatibility, experiments including immersion tests, cell morphology, cell skeleton, CCK-8 assessment, ALP activity and osteogenic induction were conducted with comparison to Cu-bearing Co–Cr alloys. The immersion test and scratch test showed that the alloys have no cytotoxicity on L929 (rat fibroblasts) cells. The field-emission scanning electron microscope (FESEM) and fluorescent staining observation revealed good cell morphology and migration ability of BMSCs (bone marrow stromal cells) and L929 on SLM copper-bearing Co–Cr alloys. The results showed that the number of cells on 60% porosity samples are obviously larger than the other samples. Besides, the extracellular matrix (ECM) mineralization of BMSCs on SLM copper-bearing Co–Cr alloys indicated that 60% porositysamples promoted osteoblasts proliferation and differentiation. Our results indicated that 60% porosity of Cu-bearing Co–Cr alloys fabricated by SLM exhibited good cytocompatibility, is a suitable porous structure for orthopedic implants manufactured by SLM.