Samarium doped glass-reinforced hydroxyapatite with enhanced osteoblastic performance and antibacterial properties for bone tissue regeneration

A novel bioactive bone substitute with improved osteoblastic performance and effective antibacterial activity was developed, using a completely new approach based on samarium (Sm³⁺) doped P₂O₅ glass-reinforced hydroxyapatite composites (GR-HA). The composites were prepared by adding 2.5% (w/w) of the P₂O₅ glass to 97.5% (w/w) of HA. Four composites were developed, i.e. one non-doped composite, and three Sm³⁺ doped composites prepared with the P₂O₅ glass containing 0.5, 1 and 2 (mol%) of Sm₂O₃. The composites were labeled as GR-HA_control, GR-HA_0.5Sm, GR-HA_1Sm and GR-HA_2Sm. The composites were physicochemical and mechanically characterized, namely performing SEM, EDS and XRD analysis and flexural bending strength (FBS) assessment. The incorporation of Sm³⁺ in the GR-HA matrix resulted in the presence of a residual Sm³⁺ containing phase besides HA, β-TCP and α-TCP phases, increased surface hydrophilicity and slightly higher FBS. Sm³⁺ doped composites exhibited improved osteoblastic cell response, as evidenced by a better F-actin cytoskeleton organization and higher cell proliferation and expression of relevant osteoblastic genes. In addition, adhesion of Staphylococcus aureus and Staphylococcus epidermidis was greatly reduced on these composites. The improved osteoblastic behavior and the antibacterial effects were dependent on the amount of Samarium in the composite, this being particularly evident in the composite with a higher Sm³⁺ content. Therefore, the developed composite GR-HA_2Sm appears as a successful bone substitute with osteoconductive and antibacterial properties.