Physicochemical and biochemical properties of iron-loaded silicon substituted hydroxyapatite (FeSiHAp)

We have synthesized scaffolding materials based on iron-loaded silicon substituted hydroxyapatite (SiHAp) (FeSiHAp). The compounds, Ca10−x(Fex)(PO4)5-(SiO4)(OH)2−δ (x = 0.1, 0.3, 0.5), were synthesized using the stoichiometric amounts of the chemical constituents. Both physicochemical properties (structure, surface charge and hardness) and in vitro biochemical properties (Bovine serum albumin (BSA) adsorption and rat osteoblast-like UMR-106 cells response) of the products were measured. The synthesized powders still exhibited the apatite structure for iron contents up to x = 0.5. The surface charge became less negative, from −21.3 to −13.5 mV as the iron loading was increased. Compounds of FeSiHAp whisker showed a micro hardness in rang of 80–84 MPa for x = 0.1–0.5. BSA protein adsorption by FeSiHAp particles was able to fit to the energetically homogeneous behaviors in the Freundlich and Langmuir models. The release of BSA from the iron-loaded SiHAp particles was slow when compared to the release from the non iron loaded particles. Mineralization study showed the formation of apatite crystals on the FeSiHAp surface after modified simulated body fluid (m-SBF) incubation. In vitro cell growth on the FeSiHAp surface, the density of cells, the spread and production of calcium nodules on the substrate were seen to be higher for iron content x = 0.1 (FeSiHAp01). MTT tests on the FeSiHAp indicated that the UMR-106 cells were viable and there was a confluence of cells on the substrate.