ZrO2 nano-additives to bone cement increase osteoblast adhesion and proliferation

Zirconia particles were introduced into a methyl methacrylate monomer (MMA) liquid and polymethyl methacrylate (PMMA) beads during polymerization to develop novel bone cement substrates. Osteoblasts (bone-forming cells) were seeded at a density of 3500 cells/cm² and were cultured on unmodified bone cements comprising of only PMMA, bone cements modified with micron ZrO₂ additives, bone cements modified with evenly dispersed ZrO₂ nano-additives, and bone cements modified with evenly dispersed ZrO₂ nano-additives functionalized with 3-(trimethoxysilyl)propyl methacrylate for four hours and twenty-four hours. Cells were subsequently stained and counted. It was found that after four hours, osteoblast adhesion was significantly greater on bone cements containing unfunctionalized nano-ZrO₂ and bone cements containing functionalized nano-ZrO₂ as compared to unmodified bone cements with no additives. After twenty-four hours, osteoblast proliferation was shown to be significantly greater on all bone cements containing ZrO₂ additives as compared to unmodified bone cements with no additives. Additionally, osteoblast proliferation was found to be significantly greater on bone cements containing unfunctionalized nano-ZrO₂ bone cements and functionalized nano-ZrO₂ as compared to bone cements containing micron ZrO₂. Such data provided strong evidence of the increased cytocompatibility properties of PMMA with evenly dispersed ZrO₂ nano-particles and, thus, these materials should be further studied for orthopedic applications.