Cytotoxicity and cell response of preosteoblast in calcium sulfate-augmented PMMA bone cement

Poly(methyl methacrylate) (PMMA) has been widely used in orthopedic applications, but bone ingrowth and toxic monomer release are drawback of this material. Particle reinforcement with osteoconductive substitute, such as calcium sulfate (CaSO₄), is one of the solutions used to modify PMMA bone cement. The current study investigated the mechanical, chemical and biological properties of CaSO₄-augmented bone cement. Mechanical strength was measured by a material testing machine. The concentration of methyl methacrylate (MMA) monomer from the various formulations of PMMA mixed with CaSO₄ was measured by ultra-performance liquid chromatography (UPLC). CCK-8 assay and ALP assay were performed to evaluate cytotoxicity of released MMA monomer and cell differentiation. The attachment of cells to CaSO₄-augmented bone cement discs was observed by confocal and scanning electron microscopy, and surface topography was also evaluated by atomic force microscopy. The results revealed that increased CaSO₄ weight ratios led to compromised mechanical strength and increased MMA monomer release. Cell density and cell differentiation on CaSO₄-augmented bone cement discs were decreased at CaSO₄ weight ratios above 10%. In addition, the presence of micropores on the surface and surface roughness were both increased for PMMA composite discs containing higher levels of CaSO₄. These results demonstrated that fewer MC3T3-E1 cells on the surface of CaSO₄–PMMA composites was correlated to increased MMA monomer release, micropore number and surface roughness. In summary, the augmentation of a higher proportion of CaSO₄ (>10 wt. %) to PMMA did not promote the biological properties of traditional PMMA bone cement.