Calcium sulfate cement combined with silica-based mesoporous material for bone regeneration: in vitro and in vivo study

Objective: One of the disadvantages of using CSC (calcium sulfate cement) in vivo is its weak osteogenic activity. Thus composite materials based on CSC have been recently studied. Silica-based mesoporous material (SBA-15) shows great potential for biological applications because of its functionalized surfaces and biocompatibility. We assumed that blending SBA-15 into CSC could improve the osteogenic activity of the CSC. Methods: SBA-15 was blended into CSC powder at a mass ratio of 5%, 10% and 20% to make a CSC/SBA composite. Four groups including CSC (pure CSC), CSC-5S (5% mass ratio), CSC-10S (10% mass ratio) and CSC-20S (20% mass ratio) group were designed. The cell adherence was assessed using the cell counting. The cell proliferation was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The osteogenic differentiation was evaluated using alkaline phosphatase (ALP) staining, alizarin red staining analysis, and the expression levels of osteogenic related genes, mainly ALP, collagen I (COL1), osteopontin and osteocalcin. An in vivo animal study was performed using the radius bone defect in a rabbit model. The micro computed tomography (CT) and histological evaluation were used to investigate bone formation. Results: The number of adhered cells on the CSC-10S and CSC-20S surface was higher than that on CSC and CSC-5S surface. The relative cell proliferation rate in CSC/SBA group was higher than that in CSC group. Compared with CSC and CSC-5S group, ALP staining in CSC-10S and CSC-20S group was increased. Alizarin red staining in the different CSC/SBA groups was higher than that in the CSC group. Higher expression levels of osteogenic differentiation-related genes were seen in cells grown on CSC/SBA composite. Micro CT and histological evaluation confirmed that CSC/SBA composite improved the efficiency of new bone formation in the bone defect. The above osteogenic activities were enhanced with increased mass ratio of SBS-15 in CSC/SBA composite. Conclusion: Incorporation of SBA-15 into CSC could greatly improve the osteogenic activity of CSC, implying the CSC/SBA composite are more beneficial to the bone repairing than pristine CSC.