Effect of copper-doped silicate 13-93 bioactive glass scaffolds on the response of MC3T3-E1 cells in vitro and on bone regeneration and angiogenesis in rat calvarial defects in vivo

The release of inorganic ions from biomaterials could provide an alternative approach to the use of growth factors for improving tissue healing. In the present study, the release of copper (Cu) ions from bioactive silicate (13-93) glass scaffolds on the response of cells in vitro and on bone regeneration and angiogenesis in vivo was studied. Scaffolds doped with varying concentrations of Cu (0-2.0 wt.% CuO) were created with a grid-like microstructure by robotic deposition. When immersed in simulated body fluid in vitro, the Cu-doped scaffolds released Cu ions into the medium in a dose-dependent manner and converted partially to hydroxyapatite. The proliferation and alkaline phosphatase activity of pre-osteoblastic MC3T3-E1 cells cultured on the scaffolds were not affected by 0.4 and 0.8 wt.% CuO in the glass but they were significantly reduced by 2.0 wt.% CuO. The percent new bone that infiltrated the scaffolds implanted for 6 weeks in rat calvarial defects (46 ± 8%) was not significantly affected by 0.4 or 0.8 wt.% CuO in the glass whereas it was significantly inhibited (0.8 ± 0.7%) in the scaffolds doped with 2.0 wt.% CuO. The area of new blood vessels in the fibrous tissue that infiltrated the scaffolds increased with CuO content of the glass and was significantly higher for the scaffolds doped with 2.0 wt.% CuO. Loading the scaffolds with bone morphogenetic protein-2 (1 μg/defect) significantly enhanced bone infiltration and reduced fibrous tissue in the scaffolds. These results showed that doping the 13-93 glass scaffolds with up to 0.8 wt.% CuO did not affect their biocompatibility whereas 2.0 wt.% CuO was toxic to cells and detrimental to bone regeneration.