Biocompatible nHA/Col-BMP-9/GM Scaffold: Synthesis, Characterization, and Effects on Bone Marrow Mesenchymal Stem Cells

Bone tissue engineering is a complex process that requires concerted functions of biomaterials, cells, and bioactive growth factors. A porous nano-hydroxyapatite (nHA)/collagen (Col)-bone morphogenetic protein (BMP)-9/gelatin microsphere (GM) scaffold was fabricated by a combination of blending, crosslinking, and freeze-drying technologies. The nHA/Col-BMP-9/GM scaffold was well manufactured with a three-dimensional structure and had good mechanical properties. Rat bone marrow mesenchymal stem cells (BMMSCs) were isolated and cultured in vitro, and then identified by flow cytometry. An indirect Cell Counting Kit-8 assay demonstrated that the scaffolds favored BMMSC proliferation, indicating their cytocompatibility. In vitro, BMMSCs were seeded onto the nHA/Col-BMP-9/GM scaffolds to mimic a natural microenvironment. Scanning electron microscopy observation and adhesion rate determination were performed to evaluate the adherence and growth of BMMSCs on the composite scaffolds. Cells cultured in the scaffolds tended to maintain good morphology, attachment, and proliferation, confirming that the scaffolds were biocompatible and showed no cytotoxicity in vitro. Alkaline phosphatase expression was examined to assess the effect of the composite scaffolds on the osteogenic differentiation of rat BMMSCs. The results revealed that the nHA/Col-GM scaffolds, especially the BMP-9-loaded nHA/Col-GM scaffolds, significantly promoted the osteogenic differentiation of BMMSCs. For in vivo determination, acute toxicity, pyrogenic, and implantation tests were performed and verified that the composite scaffolds possessed excellent biocompatibility. This novel biocompatible scaffold has good application prospects for bone repair and regeneration.