Influence of sol–gel derived strontium–cerium co-substitution in fluorohydroxyapatite and its in-vitro bioactivity

Abstract

The present study is to investigate the influence of Sr2+ and Ce3+ ions in the structure of fluorohydroxyapatite (FHA) (Ca10(PO4)6F0.5(OH)1.5), a partial substitution of fluorine ion in hydroxyapatite. Co-substitution of Sr2+ and Ce3+ ions improves the osteoblast cell response, an important factor which stimulates the bone formation surrounding the implant material. Sol–gel derived fluorohydroxyapatite samples were co-substituted with Sr2+ and Ce3+ ions [xSr/yCe-FHA, where x = 5–40 mol% of Sr2+ and y = 5–20 mol% of Ce3+]. The intensity variation and shift of Fourier transform infrared bands observed after the co-substitution of Sr2+ and Ce3+ ions confirmed the doping. The X-ray diffraction shows the decrease in crystallite size with Ce3+ concentration and aids in forming beta-tri calcium phosphate and cerium-oxide (CeO) phases. Co-substitution of Sr2+ and Ce3+ increases the microhardness and fracture toughness, while micro structural analysis reveals the decrease in grain size. In-vitro bioactivity studies were conducted on samples using human osteosarcoma MG63 cells to investigate the osteoblast cell response. Co-substitution of cations in fluorohydroxyapatite by sol–gel method influenced the structure, phase formation, mechanical property, and grain size. These factors due to addition of Sr2+ and Ce3+ ions in fluorohydroxyapatite are attributed to the improvement of cell viability and alkaline phosphatase (ALP) activity.